JP7026049B2 - Affine motion vector derivation device, predictive image generator, motion image decoding device, and motion image coding device - Google Patents

Description

Embodiments of the present invention relate to an affine motion vector derivation device, a predictive image generation device, a moving image decoding device, and a moving image coding device.

In order to efficiently transmit or record a moving image, a moving image coding device that generates coded data by encoding the moving image, and a moving image that generates a decoded image by decoding the coded data. An image decoding device is used.

Specific examples of the moving image coding method include the methods proposed by H.264 / AVC and HEVC (High-Efficiency Video Coding).

In such a moving image coding method, the image (picture) constituting the moving image is a slice obtained by dividing the image and a coding unit (coding unit) obtained by dividing the slice. : CU)), and managed by a hierarchical structure consisting of a prediction unit (PU) and a conversion unit (TU), which are blocks obtained by dividing the coding unit, and coded for each CU / It is decrypted.

Further, in such a moving image coding method, a predicted image is usually generated based on a locally decoded image obtained by encoding / decoding an input image, and the predicted image is obtained from the input image (original image). The predicted residual obtained by subtraction (sometimes referred to as a "difference image" or "residual image") is encoded. Examples of the method for generating a prediction image include inter-screen prediction (inter-prediction) and in-screen prediction (intra-prediction).

Further, as a technique of video coding and decoding in recent years, affine prediction of Non-Patent Document 1 can be mentioned.

"Algorithm Description of Joint Exploration Test Model 3", JVET-C1002, Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29/WG 11, 2016-05-31 released Improved affine motion prediction, JVET-C0062, Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29/WG 11, 2016-05-17 released

In the affine prediction of Non-Patent Document 1, based on the affine prediction with 4 degrees of freedom (4 parameter affine), the motion vector of each of the plurality of subblocks included in the target block is referred to the motion vector of the two control points. And calculate. In the affine prediction of Non-Patent Document 2, the motion vector of each of the subblocks is calculated with reference to the motion vector of the three control points based on the affine prediction with 6 degrees of freedom (six-parameter affine).

The processing of the 6-parameter affine contributes to the improvement of the coding efficiency as a whole as compared with the processing of the 4-parameter affine, but when looking at the individual blocks, the movement of the control points required for the affine processing is performed. There is a problem that the amount of coding in vector coding increases. In addition, since the accuracy of the motion vector of the control point is easily affected, if the accuracy of the motion vector of the control point is low and the deviation from the true motion vector is large, the motion vector calculated by applying the processing of 6-parameter affine. There was the first problem that the accuracy of the was further lowered.

Further, in the processing of the 4-parameter affine, two control points set in the reference block are used. There is a second problem that the accuracy of the processing of the 4-parameter affine is lowered if the appropriate two points are not used as the control points.

In order to solve the first problem described above, in the affine motion vector derivation device for deriving the motion vector of each of the subblocks constituting the target PU, the affine motion vector derivation device is a plurality of subs included in the target block. Each motion vector of the block is calculated by referring to the motion vector at the control point set in the reference block that shares the vertex with the target block, and is at least one of the shape and size of the target block. Depending on the situation, the motion vector of the two control points is calculated and the four-parameter affine process is performed, or the motion vector of the three control points is calculated and the six-parameter affine process is performed.

Further, in order to solve the above-mentioned first problem, the predictive image generation device according to one aspect of the present invention is an affine in a predictive image generation device for generating a predictive image used for coding or decoding a moving image. The affine motion vector derivation unit includes a motion vector derivation unit and a prediction image generation unit, and the motion vector derivation unit includes motion vectors of each of a plurality of subblocks included in the target block in a reference block that shares a vertex with the target block. It is calculated by referring to the motion vector at the set control point, and the motion vector of the two control points is calculated according to at least one of the shape and size of the target block, and the processing of the four parameter affine. The prediction image generation unit generates a prediction image by referring to the motion vector of the control point.

Further, in order to solve the above-mentioned first problem, the predictive image generation device according to one aspect of the present invention is an affine in a predictive image generation device for generating a predictive image used for coding or decoding a moving image. The affine motion vector derivation unit includes a motion vector derivation unit and a prediction image generation unit, and the motion vector derivation unit includes motion vectors of each of a plurality of subblocks included in the target block in a reference block that shares a vertex with the target block. It is calculated by referring to the motion vector at the set control point, and the motion vector of the two control points is calculated according to at least one of the shape and size of the reference block, and the four-parameter affine process is performed. The prediction image generation unit generates a prediction image by referring to the motion vector of the control point.

Further, in order to solve the above-mentioned second problem, the predictive image generation device according to one aspect of the present invention is an affine in a predictive image generation device for generating a predictive image used for coding or decoding a moving image. The affine motion vector derivation unit includes a motion vector derivation unit and a prediction image generation unit, and the motion vector derivation unit includes motion vectors of each of a plurality of subblocks included in the target block in a reference block that shares a vertex with the target block. It is calculated by referring to the motion vector at the set control point, and the control point used for the processing of the 4-parameter affine is changed according to the shape of the target block or the shape of the reference block, and the prediction is made. The image generation unit generates a predicted image by referring to the motion vector of the control point.

According to the embodiment of the present invention, whether to apply the processing of 4-parameter affine or the processing of 6-parameter affine in order to accurately calculate the motion vector of each of the plurality of subblocks included in the target block. Can be switched appropriately. Further, it is possible to reduce the amount of coding in coding the motion vector of the control point required when performing the affine processing.

Further, according to the embodiment of the present invention, an appropriate control point can be used in the processing of the four-parameter affine.

It is a figure which shows the hierarchical structure of the data of the coded stream which concerns on this embodiment. It is a figure which shows the pattern of a PU division mode. (A) to (h) show the partition shape when the PU division modes are 2Nx2N, 2NxN, 2NxnU, 2NxnD, Nx2N, nLx2N, nRx2N, and NxN, respectively. It is a conceptual diagram which shows an example of a reference picture and a reference picture list. It is a block diagram which shows the structure of the image coding apparatus which concerns on this embodiment. It is a schematic diagram which shows the structure of the image decoding apparatus which concerns on this embodiment. It is a schematic diagram which shows the structure of the inter prediction image generation part of the image coding apparatus which concerns on this embodiment. It is a schematic diagram which shows the structure of the merge prediction parameter derivation part which concerns on this embodiment. It is a schematic diagram which shows the structure of the AMVP prediction parameter derivation part which concerns on this embodiment. It is a flowchart which shows the operation of the motion vector decoding process of the image decoding apparatus which concerns on this embodiment. It is a schematic diagram which shows the structure of the inter prediction parameter coding part of the image coding apparatus which concerns on this embodiment. It is a schematic diagram which shows the structure of the inter prediction image generation part which concerns on this embodiment. It is a schematic diagram which shows the structure of the inter prediction parameter decoding unit which concerns on this embodiment. It is a figure which shows the example which derives the motion vector spMvLX [xi] [yj] of each subblock constituting PU (width nPbW) which is the object for predicting a motion vector. (A) is a figure for explaining bilateral matching. (B) is a diagram for explaining template matching. It is a figure which shows the example of the position of the prediction unit used for deriving the motion vector of a control point in AMVP mode and merge mode. It is a figure which shows the example of the square sub-block which one side is BW, the control point V0 of the target block (width W, height H) which is the target for predicting a motion vector is located at the upper left vertex. It is a flowchart which shows an example of the process which the inter prediction parameter decoding part determines the number of control points which derives a motion vector based on the shape of a target PU. It is a flowchart which shows another example of the process which the inter prediction parameter decoding part determines the number of control points which derives a motion vector based on the shape of a target PU. It is a flowchart which shows still another example of the process which the inter prediction parameter decoding part determines the number of control points which derives a motion vector based on the shape of a target PU. It is a flowchart which shows an example of the process which the inter prediction parameter decoding part determines the number of control points which derives a motion vector based on the size of a target PU. It is a flowchart which shows another example of the process which the inter prediction parameter decoding part determines the number of control points which derives a motion vector based on the size of a target PU. It is a table showing the processing for each size when log2 (puWidth) + log2 (puHeight) is used as the value indicating the size of the target PU. It is a table which shows the processing for each size when min (puWidth, puHeight) is used as the value which shows the size of a target PU. It is a flowchart which shows an example of the process which the inter prediction parameter decoding part determines the number of control points which derives a motion vector based on both the shape and the size of a target PU. It is a flowchart which shows another example of the process which the inter prediction parameter decoding part determines the number of control points which derives a motion vector based on both the shape and the size of a target PU. It is a table which shows an example of the processing of the affine prediction part for each size and shape of a target PU. It is a table which shows another example of the processing of the affine prediction part for each size and shape of a target PU. It is a flowchart which shows an example of the process which determines whether the process of a 4-parameter affine or a 6-parameter affine is performed by the inter-prediction parameter decoding unit based on the shape of an adjacent block. It is a figure for demonstrating an example of selection of the number of control points by the process shown in FIG. 28. It is a flowchart which shows an example of the process which determines whether the process of a 4-parameter affine or a 6-parameter affine is performed by the inter-prediction parameter decoding unit based on the size of an adjacent block. It is a figure for demonstrating an example of selection of the number of control points by the process shown in FIG. It is a flowchart of the process in which the inter-prediction parameter decoding unit determines the position of the control point from which the motion vector is derived based on the shape of the target PU. It is a figure which shows the example of the position of the control point determined by the inter prediction parameter decoding unit of 3rd Embodiment. It is a flowchart of the process which the inter prediction parameter decoding unit determines the position of the point of the adjacent block used for deriving the motion vector of the control point based on the shape of the adjacent block. It is a figure which shows the example of the position of the control point determined by the inter prediction parameter decoding unit of 4th Embodiment. It is a flowchart of the process which the inter prediction parameter decoding part determines the position of the control point which derives a motion vector based on the shape of an adjacent block. It is a figure which shows the example of the position of the control point determined by the inter prediction parameter decoding unit 303 of the 5th embodiment. It is a figure which showed the structure of the transmission device equipped with the image coding device, and the receiving device equipped with an image decoding device which concerns on this embodiment. (A) shows a transmitting device equipped with an image coding device, and (b) shows a receiving device equipped with an image decoding device. It is a figure which showed the structure of the recording apparatus equipped with the image coding apparatus which concerns on this embodiment, and the reproduction apparatus equipped with the image decoding apparatus. (A) shows a recording device equipped with an image coding device, and (b) shows a playback device equipped with an image decoding device. It is a schematic diagram which shows the structure of the image transmission system which concerns on this embodiment.

(First Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 40 is a schematic diagram showing the configuration of the image transmission system 1 according to the present embodiment.

The image transmission system 1 is a system that transmits a code obtained by encoding a coded image, decodes the transmitted code, and displays the image. The image transmission system 1 includes an image coding device (moving image coding device) 11, a network 21, an image decoding device (moving image decoding device) 31, and an image display device 41.

An image T showing an image of a single layer or a plurality of layers is input to the image coding device 11. A layer is a concept used to distinguish a plurality of pictures when there is one or more pictures constituting a certain time. For example, encoding the same picture with a plurality of layers having different image quality and resolution results in scalable coding, and coding a picture with different viewpoints with a plurality of layers results in view scalable coding. When prediction (interlayer prediction, interview prediction) is performed between pictures of a plurality of layers, the coding efficiency is greatly improved. In addition, even when prediction is not performed (simulcast), the coded data can be collected.

The network 21 transmits the coded stream Te generated by the image coding device 11 to the image decoding device 31. The network 21 is an internet (internet), a wide area network (WAN: Wide Area Network), a small-scale network (LAN: Local Area Network), or a combination thereof. The network 21 is not necessarily limited to a bidirectional communication network, but may be a one-way communication network that transmits broadcast waves such as terrestrial digital broadcasting and satellite broadcasting. Further, the network 21 may be replaced with a storage medium on which a coded stream Te such as a DVD (Digital Versatile Disc) or BD (Blue-ray Disc) is recorded.

The image decoding device 31 decodes each of the coded streams Te transmitted by the network 21 and generates one or a plurality of decoded images Td respectively.

The image display device 41 displays all or a part of one or a plurality of decoded images Td generated by the image decoding device 31. The image display device 41 includes, for example, a display device such as a liquid crystal display or an organic EL (Electro-luminescence) display. Further, in spatial scalable coding and SNR scalable coding, when the image decoding device 31 and the image display device 41 have high processing power, an extended layer image with high image quality is displayed and only lower processing power is obtained. Displays a base layer image that does not require as high processing power and display power as the extended layer.

<Operator>
The operators used herein are described below.

>> is a right bit shift, << is a left bit shift, & is a bitwise AND, | is a bitwise OR, and | = is a sum operation (OR) with another condition.

x? y: z is a ternary operator that takes y when x is true (other than 0) and z when x is false (0).

Clip3 (a, b, c) is a function that clips c to a value greater than or equal to a and less than or equal to b. Is a function that returns c (where a <= b).

<Structure of coded stream Te>
Prior to the detailed description of the image coding device 11 and the image decoding device 31 according to the present embodiment, the data structure of the coded stream Te generated by the image coding device 11 and decoded by the image decoding device 31 will be described. ..

FIG. 1 is a diagram showing a hierarchical structure of data in the coded stream Te. The coded stream Te typically includes a sequence and a plurality of pictures constituting the sequence. 1 (a) to 1 (f) of FIG. 1 are a coded video sequence that defines a sequence SEQ, a coded picture that defines a picture PICT, a coded slice that defines a slice S, and a coded slice that defines slice data, respectively. It is a figure which shows the coding unit (CU) included in the data, the coding tree unit included in the coding slice data, and the coding tree unit.

(Coded video sequence)
The coded video sequence defines a set of data that the image decoder 31 refers to in order to decode the sequence SEQ to be processed. As shown in FIG. 1A, the sequence SEQ includes a video parameter set (Video Parameter Set), a sequence parameter set SPS (Sequence Parameter Set), a picture parameter set PPS (Picture Parameter Set), a picture PICT, and an addition. Includes SEI (Supplemental Enhancement Information). Here, the value shown after # indicates the layer ID. FIG. 1 shows an example in which coded data of # 0 and # 1, that is, layer 0 and layer 1 exist, but the type of layer and the number of layers do not depend on this.

A video parameter set VPS is a set of coding parameters common to a plurality of moving images in a moving image composed of a plurality of layers, and a set of coding parameters related to the multiple layers included in the moving image and individual layers. The set is defined.

The sequence parameter set SPS defines a set of coding parameters that the image decoding device 31 refers to in order to decode the target sequence. For example, the width and height of the picture are specified. There may be a plurality of SPS. In that case, select one of multiple SPS from PPS.

The picture parameter set PPS defines a set of coding parameters that the image decoding device 31 refers to in order to decode each picture in the target sequence. For example, it includes a reference value of the quantization width used for decoding a picture (pic_init_qp_minus26) and a flag (weighted_pred_flag) indicating the application of weighted prediction. There may be a plurality of PPS. In that case, select one of a plurality of PPSs from each picture in the target sequence.

(Coded picture)
The coded picture defines a set of data referred to by the image decoding device 31 in order to decode the picture PICT to be processed. As shown in FIG. 1 (b), the picture PICT includes slices S0 to S _NS-1 (NS is the total number of slices contained in the picture PICT).

In the following, when it is not necessary to distinguish each of slices S0 to S _NS-1 , the subscript of the sign may be omitted. The same applies to the data included in the coded stream Te described below and having a subscript.

(Coded slice)
The coded slice defines a set of data referred to by the image decoding device 31 in order to decode the slice S to be processed. As shown in FIG. 1 (c), the slice S includes the slice header SH and the slice data SDATA.

The slice header SH includes a group of coding parameters referred to by the image decoding device 31 for determining the decoding method of the target slice. The slice type specification information (slice_type) that specifies the slice type is an example of the coding parameter included in the slice header SH.

The slice types that can be specified by the slice type specification information are (1) I slice that uses only intra prediction for coding, (2) unidirectional prediction for coding, or P slice that uses intra prediction. (3) B slices using unidirectional prediction, bidirectional prediction, or intra prediction at the time of coding can be mentioned.

The slice header SH may include a reference (pic_parameter_set_id) to the picture parameter set PPS included in the coded video sequence.

(Coded slice data)
The coded slice data defines a set of data referred to by the image decoding device 31 in order to decode the slice data SDATA to be processed. The slice data SDATA includes a coding tree unit (CTU) as shown in FIG. 1 (d). A CTU is a block of fixed size (for example, 64x64) that constitutes a slice, and is sometimes called a maximum coding unit (LCU).

(Coded tree unit)
As shown in FIG. 1 (e), a set of data referred to by the image decoding device 31 for decoding the coded tree unit to be processed is defined. The coded tree unit is divided by a recursive quadtree division. A node with a tree structure obtained by recursive quadtree division is called a coding node (CN). The middle node of the quadtree is a coding node, and the coding tree unit itself is also defined as the top-level coding node. The CTU includes a split flag (cu_split_flag), and when cu_split_flag is 1, it is split into four coding nodes CN. When cu_split_flag is 0, the coding node CN is not divided and has one coding unit (CU: Coding Unit) as a node. The coding unit CU is the terminal node of the coding node and is not further divided. The coding unit CU is a basic unit of coding processing.

When the size of the coding tree unit CTU is 64x64 pixels, the size of the coding unit can be any of 64x64 pixels, 32x32 pixels, 16x16 pixels, and 8x8 pixels.

(Coding unit)
As shown in FIG. 1 (f), a set of data referred to by the image decoding device 31 for decoding the coding unit to be processed is defined. Specifically, the coding unit is composed of a prediction tree, a conversion tree, and a CU header CUH. The CU header defines the prediction mode, division method (PU division mode), and the like.

In the prediction tree, prediction information (reference picture index, motion vector, etc.) of each prediction unit (PU) obtained by dividing the coding unit into one or a plurality is defined. In other words, the prediction unit is one or more non-overlapping regions that make up the coding unit. The prediction tree also includes one or more prediction units obtained by the above division. In the following, the prediction unit obtained by further dividing the prediction unit will be referred to as a “subblock”. The subblock is composed of a plurality of pixels. If the size of the prediction unit and the subblock are equal, there is only one subblock in the prediction unit. If the prediction unit is larger than the size of the subblock, the prediction unit is divided into subblocks. For example, when the prediction unit is 8x8 and the subblock is 4x4, the prediction unit is divided into four subblocks consisting of two horizontal divisions and two vertical divisions.

The prediction process may be performed for each prediction unit (subblock).

Roughly speaking, there are two types of divisions in the prediction tree: intra-forecasting and inter-forecasting. Intra-prediction is prediction within the same picture, and inter-prediction refers to prediction processing performed between pictures different from each other (for example, between display times and between layer images).

In the case of intra-prediction, there are two division methods: 2Nx2N (same size as the coding unit) and NxN.

In the case of inter-prediction, the division method is encoded by the PU division mode (part_mode) of the coded data, 2Nx2N (same size as the coding unit), 2NxN, 2NxnU, 2NxnD, Nx2N, nLx2N, nRx2N, and There are NxN and so on. Note that 2NxN and Nx2N indicate a 1: 1 symmetric division, and 2NxnU, 2NxnD and nLx2N and nRx2N indicate a 1: 3 and 3: 1 asymmetric division. The PUs included in the CU are expressed as PU0, PU1, PU2, and PU3 in that order.

2 (a) to 2 (h) specifically show the shape of the partition (position of the boundary of the PU division) in each PU division mode. (A) of FIG. 2 shows a partition of 2Nx2N, and (b), (c), and (d) show a partition (horizontal partition) of 2NxN, 2NxnU, and 2NxnD, respectively. (E), (f), and (g) indicate partitions (vertical partitions) in the case of Nx2N, nLx2N, and nRx2N, respectively, and (h) indicates an NxN partition. The horizontally long partition and the vertically long partition are collectively called a rectangular partition, and 2Nx2N and NxN are collectively called a square partition.

Further, in the conversion tree, the coding unit is divided into one or a plurality of conversion units, and the position and size of each conversion unit are defined. In other words, the conversion unit is one or more non-overlapping regions constituting the coding unit. The conversion tree also includes one or more conversion units obtained from the above divisions.

There are two types of division in the conversion tree: one that allocates an area of the same size as the coding unit as the conversion unit, and one that recursively divides into quadtrees, similar to the above-mentioned division of CU.

The conversion process is performed for each conversion unit.

(Prediction parameters)
The prediction image of the prediction unit (PU) is derived by the prediction parameters attached to the PU. The prediction parameters include prediction parameters for intra-prediction and prediction parameters for inter-prediction. Hereinafter, the prediction parameters of the inter-prediction (inter-prediction parameters) will be described. The inter-prediction parameter is composed of the prediction list utilization flags predFlagL0 and predFlagL1, the reference picture indexes refIdxL0 and refIdxL1, and the motion vectors mvL0 and mvL1. The prediction list usage flags predFlagL0 and predFlagL1 are flags indicating whether or not the reference picture list called the L0 list and the L1 list is used, respectively, and the reference picture list corresponding to the case where the value is 1 is used. In the present specification, when "a flag indicating whether or not it is XX" is described, it is assumed that a flag other than 0 (for example, 1) is XX, 0 is not XX, and logical negation, logical product, etc. Treat 1 as true and 0 as false (same below). However, in an actual device or method, other values can be used as true values and false values.

The syntax elements for deriving the inter-prediction parameters contained in the coded data include, for example, PU split mode part_mode, merge flag merge_flag, merge index merge_idx, inter-prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, There is a difference vector mvdLX, a PU affine application flag pu_affine_enable_flag, and a PU affine mode flag pu_affine_mode_flag.

(Reference picture list)
The reference picture list is a list composed of reference pictures stored in the reference picture memory 306. FIG. 3 is a conceptual diagram showing an example of a reference picture and a reference picture list. In FIG. 3A, the rectangle is a picture, the arrow is a reference relationship of the picture, the horizontal axis is time, I, P, and B in the rectangle are intra pictures, single prediction pictures, bi-prediction pictures, and the numbers in the rectangle are decoded. Show the order. As shown in the figure, the decoding order of the pictures is I0, P1, B2, B3, B4, and the display order is I0, B3, B2, B4, P1. FIG. 3B shows an example of a reference picture list. The reference picture list is a list representing candidates for reference pictures, and one picture (slice) may have one or more reference picture lists. In the example of the figure, the target picture B3 has two reference picture lists, L0 list RefPicList0 and L1 list RefPicList1. When the target picture is B3, the reference pictures are I0, P1, and B2, and the reference picture has these pictures as elements. For each prediction unit, the reference picture index refIdxLX specifies which picture in the reference picture list RefPicListX is actually referenced. The figure shows an example in which refIdxL0 and refIdxL1 refer to reference pictures P1 and B2.

(Merge prediction and AMVP prediction)
Prediction parameter decoding (encoding) methods include a merge mode and an AMVP (Adaptive Motion Vector Prediction) mode. The merge flag merge_flag is a flag for identifying these. The merge prediction mode is a mode used to derive the prediction list utilization flag predFlagLX (or inter prediction identifier inter_pred_idc), the reference picture index refIdxLX, and the motion vector mvLX from the prediction parameters of the neighboring PUs that have already been processed without including them in the coded data. , AMVP mode is a mode in which the inter-prediction identifier inter_pred_idc, the reference picture index refIdxLX, and the motion vector mvLX are included in the encoded data. The motion vector mvLX is encoded as a prediction vector index mvp_LX_idx that identifies the prediction vector mvpLX and a difference vector mvdLX.

The inter-prediction identifier inter_pred_idc is a value indicating the type and number of reference pictures, and takes any value of PRED_L0, PRED_L1, and PRED_BI. PRED_L0 and PRED_L1 indicate that the reference pictures managed by the reference picture list of the L0 list and the L1 list are used, respectively, and indicate that one reference picture is used (single prediction). PRED_BI indicates that two reference pictures are used (bipred), and the reference pictures managed by the L0 list and the L1 list are used. The prediction vector index mvp_LX_idx is an index indicating the prediction vector, and the reference picture index refIdxLX is an index indicating the reference pictures managed by the reference picture list. LX is a description method used when L0 prediction and L1 prediction are not distinguished, and by replacing LX with L0 and L1, the parameters for the L0 list and the parameters for the L1 list are distinguished.

The merge index merge_idx is an index indicating whether one of the prediction parameter candidates (merge candidates) derived from the PU for which processing has been completed is used as the prediction parameter of the target PU (target block) to be decoded.

(Motion vector)
The motion vector mvLX indicates the amount of deviation between blocks on two different pictures. The prediction vector and the difference vector related to the motion vector mvLX are called the prediction vector mvpLX and the difference vector mvdLX, respectively.

(Inter prediction identifier inter_pred_idc and prediction list usage flag predFlagLX)
The relationship between the inter-prediction identifier inter_pred_idc and the prediction list usage flags predFlagL0 and predFlagL1 is as follows and can be converted to each other.

inter_pred_idc = (predFlagL1 << 1) + predFlagL0
predFlagL0 = inter_pred_idc & 1
predFlagL1 = inter_pred_idc >> 1
As the inter-prediction parameter, the prediction list utilization flag may be used, or the inter-prediction identifier may be used. Further, the determination using the prediction list utilization flag may be replaced with the determination using the inter-prediction identifier. On the contrary, the determination using the inter-prediction identifier may be replaced with the determination using the prediction list utilization flag.

(Judgment of bipred biPred)
The bipred BiPred flag biPred can be derived depending on whether the two prediction list usage flags are both 1. For example, it can be derived by the following formula.

biPred = (predFlagL0 == 1 && predFlagL1 == 1)
The flag biPred can also be derived by whether or not the inter-prediction identifier is a value indicating that two prediction lists (reference pictures) are used. For example, it can be derived by the following formula.

biPred = (inter_pred_idc == PRED_BI)? 1: 0
The above equation can also be expressed by the following equation.

biPred = (inter_pred_idc == PRED_BI)
Note that PRED_BI can use a value of 3, for example.

(PU affine application flag, PU affine mode flag)
The PU affine application flag pu_affine_enable_flag is a flag indicating whether or not to apply the affine prediction. The PU affine mode flag pu_affine_mode_flag (also simply referred to as affine mode) is a flag indicating whether to apply a 4-parameter affine or a 6-parameter affine.

(Configuration of image decoder)
Next, the configuration of the image decoding device 31 (moving image decoding device) according to the present embodiment will be described. FIG. 5 is a schematic view showing the configuration of the image decoding device 31 according to the present embodiment. The image decoding device 31 includes an entropy decoding unit 301, a prediction parameter decoding unit (prediction image decoding device) 302, a loop filter 305, a reference picture memory 306, a prediction parameter memory 307, a prediction image generation unit (prediction image generation device) 308, and a reverse. It includes a quantization / inverse DCT unit 311 and an addition unit 312.

Further, the prediction parameter decoding unit 302 includes an inter prediction parameter decoding unit 303 and an intra prediction parameter decoding unit 304. The prediction image generation unit 308 includes an inter-prediction image generation unit 309 (prediction image generation unit) and an intra-prediction image generation unit 310.

The entropy decoding unit 301 performs entropy decoding on the coded stream Te input from the outside, separates and decodes each code (syntax element). The separated codes include prediction information for generating a prediction image, residual information for generating a difference image, and the like.

The entropy decoding unit 301 outputs a part of the separated codes to the prediction parameter decoding unit 302. Some of the separated codes are, for example, the prediction mode predMode, the PU split mode part_mode, the merge flag merge_flag, the merge index merge_idx, the interprediction identifier inter_pred_idc, the reference picture index refIdxLX, the prediction vector index mvp_LX_idx, and the difference vector mvdLX. The control of which code is decoded is performed based on the instruction of the prediction parameter decoding unit 302. The entropy decoding unit 301 outputs the quantization coefficient to the inverse quantization / inverse DCT unit 311. This quantization coefficient is a coefficient obtained by performing DCT (Discrete Cosine Transform) on the residual signal and quantizing it in the coding process.

The inter-prediction parameter decoding unit 303 decodes the inter-prediction parameter with reference to the prediction parameter stored in the prediction parameter memory 307 based on the code input from the entropy decoding unit 301.

The inter-prediction parameter decoding unit 303 outputs the decoded inter-prediction parameter to the prediction image generation unit 308 and stores it in the prediction parameter memory 307. The details of the inter-prediction parameter decoding unit 303 will be described later.

The intra prediction parameter decoding unit 304 decodes the intra prediction parameter by referring to the prediction parameter stored in the prediction parameter memory 307 based on the code input from the entropy decoding unit 301. The intra prediction parameter is a parameter used in the process of predicting the CU in one picture, for example, the intrapred mode. The intra prediction parameter decoding unit 304 outputs the decoded intra prediction parameter to the prediction image generation unit 308, and stores the decoded intra prediction parameter in the prediction parameter memory 307.

The intra prediction parameter decoding unit 304 may derive an intra prediction mode that differs depending on the luminance and the color difference. In this case, the intra prediction parameter decoding unit 304 decodes the luminance prediction mode IntraPredModeY as the luminance prediction parameter and the luminance prediction mode IntraPredModeC as the color difference prediction parameter. The brightness prediction mode IntraPredModeY is 35 modes, and corresponds to planar prediction (0), DC prediction (1), and direction prediction (2 to 34). The color difference prediction mode IntraPredModeC uses any one of planar prediction (0), DC prediction (1), direction prediction (2-34), and LM mode (35). The intraprediction parameter decoding unit 304 decodes a flag indicating whether or not IntraPredModeC is in the same mode as the luminance mode, and if it shows that the flag is in the same mode as the luminance mode, assigns IntraPredModeY to IntraPredModeC and sets the flag to luminance mode. If it is shown that the mode is different from the mode, the planar prediction (0), DC prediction (1), direction prediction (2-34), and LM mode (35) may be decoded as IntraPredModeC.

The loop filter 305 applies a filter such as a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the decoded image of the CU generated by the addition unit 312.

The reference picture memory 306 stores the decoded image of the CU generated by the addition unit 312 at a position predetermined for each of the picture to be decoded and the CU.

The prediction parameter memory 307 stores the prediction parameters in a predetermined position for each picture and prediction unit (or subblock, fixed size block, pixel) to be decoded. Specifically, the prediction parameter memory 307 stores the inter prediction parameter decoded by the inter prediction parameter decoding unit 303, the intra prediction parameter decoded by the intra prediction parameter decoding unit 304, and the prediction mode pred Mode separated by the entropy decoding unit 301. .. The stored inter-prediction parameters include, for example, the prediction list utilization flag predFlagLX (inter-prediction identifier inter_pred_idc), the reference picture index refIdxLX, and the motion vector mvLX.

The prediction mode predMode input from the entropy decoding unit 301 is input to the prediction image generation unit 308, and the prediction parameters are input from the prediction parameter decoding unit 302. Further, the prediction image generation unit 308 reads the reference picture from the reference picture memory 306. The prediction image generation unit 308 generates a prediction image of the PU using the input prediction parameter and the read reference picture in the prediction mode indicated by the prediction mode predMode.

Here, when the prediction mode predMode indicates the inter-prediction mode, the inter-prediction image generation unit 309 uses the inter-prediction parameter input from the inter-prediction parameter decoding unit 303 and the reference picture read out to perform inter-prediction to predict the PU. To generate.

The inter-prediction image generation unit 309 refers to the reference picture list (L0 list or L1 list) in which the prediction list usage flag predFlagLX is 1, from the reference picture indicated by the reference picture index refIdxLX, and the motion vector mvLX with reference to the target PU. The reference picture block at the position indicated by is read from the reference picture memory 306. The inter-prediction image generation unit 309 performs prediction based on the read reference picture block and generates a prediction image of the PU. The inter-prediction image generation unit 309 outputs the generated prediction image of the PU to the addition unit 312.

When the prediction mode predMode indicates the intra prediction mode, the intra prediction image generation unit 310 performs intra prediction using the intra prediction parameters input from the intra prediction parameter decoding unit 304 and the reference picture read out. Specifically, the intra prediction image generation unit 310 reads from the reference picture memory 306 a picture to be decoded, which is an adjacent PU within a predetermined range from the target PU among the already decoded PUs. The predetermined range is, for example, one of the adjacent PUs on the left, upper left, upper, and upper right when the target PU moves sequentially in the order of so-called raster scan, and differs depending on the intra prediction mode. The order of raster scan is the order in which each row is sequentially moved from the left end to the right end in each picture from the upper end to the lower end.

The intra prediction image generation unit 310 predicts the read adjacent PU in the prediction mode indicated by the intra prediction mode IntraPredMode, and generates a prediction image of the PU. The intra prediction image generation unit 310 outputs the generated prediction image of the PU to the addition unit 312.

When the intra prediction parameter decoding unit 304 derives an intra prediction mode different in brightness and color difference, the intra prediction image generation unit 310 determines the planar prediction (0), DC prediction (1), and direction according to the brightness prediction mode IntraPredModeY. A PU prediction image of brightness is generated by any of the predictions (2 to 34), and the planar prediction (0), DC prediction (1), direction prediction (2 to 34), and LM mode are generated according to the color difference prediction mode IntraPredModeC. A predicted image of the color difference PU is generated by any of (35).

The inverse quantization / inverse DCT unit 311 inversely quantizes the quantization coefficient input from the entropy decoding unit 301 to obtain the DCT coefficient. The inverse quantization / inverse DCT unit 311 performs an inverse DCT (Inverse Discrete Cosine Transform) on the obtained DCT coefficient and calculates a residual signal. The inverse quantization / inverse DCT unit 311 outputs the calculated residual signal to the addition unit 312.

The addition unit 312 adds the prediction image of the PU input from the inter-prediction image generation unit 309 or the intra-prediction image generation unit 310 and the residual signal input from the inverse quantization / inverse DCT unit 311 for each pixel. Generate a decrypted image of PU. The addition unit 312 stores the generated PU decoded image in the reference picture memory 306, and outputs the decoded image Td in which the generated PU decoded image is integrated for each picture to the outside.

(Structure of inter-prediction parameter decoding unit)
Next, the configuration of the inter-prediction parameter decoding unit 303 will be described.

FIG. 12 is a schematic diagram showing the configuration of the inter-prediction parameter decoding unit 303 according to the present embodiment. The inter prediction parameter decoding unit 303 includes an inter prediction parameter decoding control unit 3031, an AMVP prediction parameter derivation unit 3032 (affine motion vector derivation unit, an affine motion vector derivation device), an addition unit 3035, a merge prediction parameter derivation unit 3036, and a subblock prediction unit. It includes a parameter derivation unit 3037.

The inter-prediction parameter decoding control unit 3031 instructs the entropy decoding unit 301 to decode the code (syntax element) related to the inter-prediction, and the code (syntax element) included in the coded data, for example, the PU division mode part_mode. , Merge flag merge_flag, merge index merge_idx, inter prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX.

The inter-prediction parameter decoding control unit 3031 first extracts the merge flag merge_flag. When the inter-prediction parameter decoding control unit 3031 expresses that a certain syntax element is extracted, it means that the entropy decoding unit 301 is instructed to decode the certain syntax element and the corresponding syntax element is read from the coded data. do.

When the merge flag merge_flag indicates 0, that is, the AMVP prediction mode, the inter-prediction parameter decoding control unit 3031 extracts the AMVP prediction parameter from the coded data using the entropy decoding unit 301. AMVP prediction parameters include, for example, the inter prediction identifier inter_pred_idc, the reference picture index refIdxLX, the prediction vector index mvp_LX_idx, and the difference vector mvdLX. The AMVP prediction parameter derivation unit 3032 derives the prediction vector mvpLX from the prediction vector index mvp_LX_idx. Details will be described later. The inter-prediction parameter decoding control unit 3031 outputs the difference vector mvdLX to the addition unit 3035. The addition unit 3035 adds the prediction vector mvpLX and the difference vector mvdLX to derive a motion vector.

When the merge flag merge_flag indicates 1, that is, the merge prediction mode, the inter-prediction parameter decoding control unit 3031 extracts the merge index merge_idx as a prediction parameter related to the merge prediction. The inter-prediction parameter decoding control unit 3031 outputs the extracted merge index merge_idx to the merge prediction parameter derivation unit 3036 (details will be described later), and outputs the sub-block prediction mode flag subPbMotionFlag to the sub-block prediction parameter derivation unit 3037. The sub-block prediction parameter derivation unit 3037 divides the PU into a plurality of sub-blocks according to the value of the sub-block prediction mode flag subPbMotionFlag, and derives a motion vector in sub-block units. That is, in the sub-block prediction mode, the prediction block is predicted in small block units of 4x4 or 8x8. In the image encoding device 11 described later, the subblock prediction mode is used for a method of dividing the CU into a plurality of partitions (PUs such as 2NxN, Nx2N, NxN) and encoding the syntax of the prediction parameters for each partition. Then, since a plurality of sub-blocks are grouped into a set and the syntax of the prediction parameter is encoded for each set, the motion information of many sub-blocks can be encoded with a small amount of code.

More specifically, the sub-block prediction parameter derivation unit 3037 performs sub-block prediction in the sub-block prediction mode, and is a spatiotemporal sub-block prediction unit 30371 and an affine prediction unit 30372 (affine motion vector derivation unit, affine motion vector derivation device). ), At least one of the matching prediction unit 30373.

(Subblock prediction mode flag)
Here, a method of deriving the subblock prediction mode flag subPbMotionFlag indicating whether or not the prediction mode of a certain PU is the subblock prediction mode in the image decoding device 31 and the image coding device 11 (details will be described later) will be described. .. The image decoding device 31 and the image coding device 11 derive the subblock prediction mode flag subPbMotionFlag based on which of the spatial subblock prediction SSUB, the time subblock prediction TSUB, the affine prediction AFFINE, and the matching prediction MAT, which will be described later, is used. do. For example, when the prediction mode selected by a certain PU is N (for example, N is a label indicating the selected merge candidate), the subblock prediction mode flag subPbMotionFlag may be derived by the following equation.

subPbMotionFlag = (N == TSUB) || (N == SSUB) || (N == AFFINE) || (N == MAT)
Here, || indicates the logical sum (the same applies hereinafter).

Further, the image decoding device 31 and the image coding device 11 may be configured to perform some predictions among the spatial subblock prediction SSUB, the time subblock prediction TSUB, the affine prediction AFFINE, and the matching prediction MAT. That is, when the image coding apparatus 11 is configured to perform spatial subblock prediction SSUB and affine prediction AFFINE, the subblock prediction mode flag subPbMotionFlag may be derived as follows.

subPbMotionFlag = (N == SSUB) || (N == AFFINE)
The image decoding device 31 and the image coding device 11 may decode the affine application flag pu_affine_enable_flag from the encoded data and derive the subPbMotionFlag as 1 when the affine application flag pu_affine_enable_flag is 1. In this case, the affine prediction unit 30372 may be applied when the affine application flag pu_affine_enable_flag is 1.

(Sub-block prediction unit)
Next, the sub-block prediction unit will be described.

(Space-time subblock prediction unit 30371)
The spatiotemporal subblock prediction unit 30371 is based on the motion vector of the PU on the reference image (for example, the immediately preceding picture) adjacent to the target PU in time, or the motion vector of the PU spatially adjacent to the target PU. The motion vector of the subblock obtained by dividing is derived. Specifically, by scaling the motion vector of the PU on the reference image to match the reference picture referenced by the target PU, the motion vector of each subblock in the target PU spMvLX [xi] [yj] (xi = xPb). + nSbW * i, yj = yPb + nSbH * j, i = 0, 1, 2, ..., nPbW / nSbW -1, j = 0, 1, 2, ..., nPbH / nSbH -1) Derived (time subblock prediction). Here, (xPb, yPb) is the upper left coordinate of the target PU, nPbW, nPbH is the size of the target PU, and nSbW, nSbH is the size of the subblock.

In addition, by calculating the weighted average according to the distance between the motion vector of the PU adjacent to the target PU and the subblock obtained by dividing the target PU, the motion vector spMvLX [ xi] [yj] (xi = xPb + nSbW * i, yj = yPb + nSbH * j, i = 0, 1, 2, ・ ・ ・, nPbW / nSbW ―― 1, j = 0, 1, 2, ・ ・·, NPbH / nSbH-1) may be derived (spatial subblock prediction).

The above-mentioned candidate TSUB for time subblock prediction and candidate SSUB for spatial subblock prediction are selected as one mode (merge candidate) of the merge mode.

(Affine prediction department)
The affine prediction unit 30372 derives the affine prediction parameters of the target PU. In this embodiment, motion vectors of two or three control points of the target PU are derived as affine prediction parameters. For example, in the case of three control points (V0, V1, V2), motion vectors (MV0_x, MV0_y) (MV1_x, MV1_y) (MV2_x, MV2_y) are derived.

Specifically, the motion vector of each control point may be derived by predicting from the motion vector of the adjacent PU of the target PU, or the prediction vector mvpLX of the control point and the difference vector mvdLX derived from the coded data. The motion vector of each control point may be derived by the sum of and.

FIG. 13 shows the motion vector spMvLX of each subblock (xi, yj) constituting the target PU (nPbW × nPbH) from the motion vector (MV0_x, MV0_y) of the control point V0 and the motion vector (MV1_x, MV1_y) of V1. It is a figure which shows the example of deriving. As shown in FIG. 13, the motion vector spMvLX of each subblock is derived as a motion vector for each point located at the center of each subblock.

The affine prediction unit 30372 uses the motion vector spMvLX [xi] [yj] (xi = xPb + nSbW * i, yj = yPb + nSbH * j, i) of each subblock in the target PU based on the affine prediction parameters of the target PU. = 0, 1, 2, ···, nPbW / nSbW − 1, j = 0, 1, 2, ···, nPbH / nSbH − 1) is derived using the following equation.

spMvLX [xi] [yj] [0] = MV0_x + (MV1_x --MV0_x) / nPbW * (xi + nSbW / 2)-(MV1_y --MV0_y) / nPbH * (yj + nSbH / 2)
spMvLX [xi] [yj] [1] = MV0_y + (MV1_y --MV0_y) / nPbW * (xi + nSbW / 2) + (MV1_x --MV0_x) / nPbH * (yj + nSbH / 2)
Here, xPb and yPb are the upper left coordinates of the target PU, nPbW and nPbH are the width and height of the target PU, and nSbW and nSbH are the width and height of the subblock.

(Process flow)
Hereinafter, as an example of a more specific implementation configuration, the flow of the process in which the affine prediction unit 30372 or the AMVP prediction parameter derivation unit 3032 derives the motion vector mvLX of each subblock using the affine prediction will be described in steps. do. The process of deriving the motion vector mvLX of the subblock by the affine prediction unit 30372 or the AMVP prediction parameter derivation unit 3032 using the affine prediction includes the following four steps (STEP1) to (STEP4).

(STEP1) Derivation of control point vector As two or more control points used by the affine prediction unit 30372 or the AMVP prediction parameter derivation unit 3032 for affine prediction for deriving a candidate, representative points of the target block (here, V0 and V1). ) Is the process of deriving each motion vector. As the representative point of the block, a point on the target block or a point in the vicinity of the target block is used. In the present specification, a representative point of a block used as a control point for affine prediction is referred to as a “block control point”. The control points of the affine prediction that are not the representative points of the block are expressed as "reference control points" and may be distinguished.

(STEP2) Derivation of sub-block vector Affine prediction unit 30372 or AMVP prediction parameter derivation unit 3032 from the motion vector of the block control points (control points V0 and V1), which are the representative points of the target block derived in STEP1, to the target block. This is the process of deriving the motion vector of each included subblock. The motion vector mvLX of each subblock is derived by (STEP1) and (STEP2).

(STEP3) Subblock motion compensation The motion compensation unit 3091 has a reference picture from the reference picture memory 306 based on the prediction list usage flag predFlagLX, the reference picture index refIdxLX, and the motion vector mvLX input from the inter-prediction parameter decoding unit 303. Motion compensation is performed for each sub-block that generates motion compensation image predSamplesLX by reading and filtering blocks located at positions shifted by the motion vector mvLX from the position of the target block on the reference picture specified by the index refIdxLX. It is a process.

(STEP4) Storage of motion vector of subblock In the AMVP mode, the motion vector mvLX of each subblock derived by the AMVP prediction parameter derivation unit 3032 in the above (STEP2) is stored in the prediction parameter memory 307. Similarly, in the merge mode as well, the motion vector mvLX of each subblock derived by the affine prediction unit 30372 in the above (STEP 2) is stored in the prediction parameter memory 307.

The derivation of the motion vector mvLX of the subblock using the affine prediction can be carried out in both the AMVP mode and the merge mode. In the following, some of the processes of (STEP1) to (STEP4) will be described for the AMVP mode and the merge mode, respectively.

(Details of STEP1)
First, regarding the process of (STEP1), the AMVP mode and the merge mode will be described below with reference to FIG. FIG. 15 is a diagram showing an example of the position of the prediction unit used for deriving the motion vector of the control point in the AMVP mode and the merge mode.

(Derivation of motion vector of control point in AMVP mode)
The AMVP prediction parameter derivation unit 3032 derives a vector candidate mvpLX from the motion vector stored in the prediction parameter memory 307 based on the reference picture index refIdx. Then, the AMVP prediction parameter derivation unit 3032 predicts (derives) the motion vector of the representative point (here, the point V0, the point V1 and the point V2) of the target block with reference to the read motion vector.

In the AMVP mode, the inter-prediction parameter decoding control unit 3031 extracts the AMVP prediction parameter from the coded data using the entropy decoding unit 301. This AMVP prediction parameter includes a separately encoded difference vector mvdLX for correcting the prediction vector mvpLX of the representative points (point V0, point V1 and point V2).

As shown in FIG. 15A, the AMVP prediction parameter derivation unit 3032 is adjacent to one of the representative points (here, point V0), and blocks A and B sharing the representative point (vertex) with the target block. , And one of the motion vectors of C (reference block) is referred to from the prediction parameter memory 307, and the prediction vector mvpLX of the representative point is derived. Further, the motion vector mvLX at the control point V0 is derived by adding the difference vector mvdLX of the representative point decoded from the coded data to the derived prediction vector mvpLX. The AMVP prediction parameter derivation unit 3032 may decode the index mvp_LX_idx from the coded data and determine which of the motion vectors of blocks A, B, and C is referred to as the prediction vector.

Similarly, as shown in FIG. 15A, the AMVP prediction parameter derivation unit 3032 is adjacent to a representative point (here, point V1) different from the point V0, and sets the target block and the representative point (vertex). One of the motion vectors of the shared blocks D and E (reference block) is referred to from the prediction parameter memory 307, and the prediction vector mvpLX of the representative point V1 is derived. Further, the difference vector mvdLX of the representative point V1 decoded from the coded data is added to the derived prediction vector mvpLX to derive the motion vector mvLX of the control point V1. The AMVP prediction parameter derivation unit 3032 may decode the index mvp_LX_idx from the coded data and determine which of the motion vectors of blocks D and E is referred to as the prediction vector.

Similarly, as shown in FIG. 15 (b), the AMVP prediction parameter derivation unit 3032 is adjacent to a representative point (here, point V2) different from the points V0 and V1, and is adjacent to the target block and the representative point (vertex). ) Is referred to from the prediction parameter memory 307 for any one of the motion vectors of the blocks F and G (reference block), and the prediction vector mvpLX of the representative point V2 is derived. Further, the AMVP prediction parameter derivation unit 3032 adds the difference vector mvdLX of the representative point V2 decoded from the coded data to the derived prediction vector mvpLX to derive the motion vector mvLX of the control point V2. The AMVP prediction parameter derivation unit 3032 may decode the index mvp_LX_idx from the coded data and determine which of the motion vectors of the blocks F and G is referred to as the prediction vector.

More specifically, the AMVP prediction parameter derivation unit 3032 derives the prediction vector candidate of the control point VN (N = 0.2) and stores it in the prediction vector candidate list mvpListVNLX []. Further, the AMVP prediction parameter derivation unit 3032 derives the motion vector (MVi_x, MVi_y) of the control point VN from the prediction vector index mvpVN_LX_idx of the point VN and the difference vector mvdVNLX from the coded data by the following equation.

MVi_x = mvLX [0] = mvpListVNLX [mvpVN_LX_idx] [0] + mvdVNLX [0]
MVi_y = mvLX [1] = mvpListVNLX [mvpVN_LX_idx] [1] + mvdVNLX [1]
The position of the control point in STEP 1 is not limited to the above. The lower right vertex of the target block or the points around the target block may be used as described later.

As will be described later, in the configuration of switching between the 4-parameter affine and the 6-parameter affine, the AMVP prediction parameter derivation unit 3032 encodes the difference vector of two points, for example, points V0 and V1 in the case of the 4-parameter affine. Decoding from, and deriving the motion vector of two control points. In the case of a 6-parameter affine, the difference vector of three points, for example, points V0, V1 and V2, is decoded from the coded data, and the motion vector of the three control points is derived. The control points derived in the case of the four-parameter affine are not limited to the points V0 and V1, but may be the points V0 and V2, the points V1 and V2, the points V0 and V2, and the other two points. Even in the case of the 6-parameter affine, the control points to be derived are not limited to the points V0, V1 and V2.

(General formula for affine prediction)
The general formula of the four-parameter affine will be described below. Position (0, 0), motion vector mv_x, my_y The motion vector (MVi_x, MVi_y) of the point Vi at the position (xi, yi) starting from V0 has four parameters (mv_x, mv_y, ev, rv). That is, it can be obtained by the following general formula (eq1) using the motion vector of the expansion and rotation center (translation vector mv_x, mv_y), the expansion parameter ev, and the rotation parameter rv.

MVi_x = mv_x + ev * xi --rv * yi
MVi_y = mv_y + rv * xi + ev * yi (eq1)
Substituting the motion vector (MV0_x, MV0_y) at the point (xi, yi) = (0, 0) and the motion vector (MVk_x, MVk_y) at the point (xi, yi) = (xk, yk) into the above. , (Ev, rv) can be solved to obtain the following equation.

ev = {xk * (MVk_x --MV0_x) + yk * (MVk_y --MV0_y)} / (pow (xk, 2) + pow (yk, 2))
rv = {-yk * (MVk_x --MV0_x) + xk * (MVk_y --MV0_y)} / (pow (xk, 2) + pow (yk, 2))
Note that pow (x, 2) indicates the square of x.

Subsequently, the general formula of the 6-parameter affine will be described below. Position (0, 0), motion vector mv_x, my_y The motion vector (MVi_x, MVi_y) of the point Vi at the position (xi, yi) starting from V0 has four parameters (mv_x, mv_y, ev1, rv1, Using ev2, rv2), it can be obtained by the following general formula (eq2).

MVi_x = mv_x + ev1 * xi + rv2 * yi
MVi_y = mv_y + rv1 * xi + ev2 * yi (eq2)
(Derivation of motion vector of control point in merge mode)
The affine prediction unit 30372 refers to the prediction parameter memory 307 for the prediction unit including the blocks A to E as shown in FIG. 15 (c), and confirms whether or not the affine prediction is used. The first prediction unit found as the prediction unit in which the affine prediction is used (here, the reference block A in FIG. 15C) is selected as the adjacent block (merge reference block), and the motion vector is derived. The adjacent block does not necessarily have to be in direct contact with the target PU (it does not have to have a common side). For example, a block having a common point with the target PU, such as a point on the upper right, a point on the upper left, and a point on the lower right of the target PU, can be regarded as an adjacent block. Further, a neighboring block sufficiently close to the target PU can be used as an adjacent block. This also applies to the second to fifth embodiments described later.

The affine prediction unit 30372 is used to use the affine prediction at the upper left corner point (point v0 of (d) in FIG. 15) and the upper right corner point (of (d) in FIG. 15) of the selected adjacent block. The motion vector of the control point is derived from the point v1), the point in the lower left corner (point v2 in (d) of FIG. 15), and two or three points out of each point v3 in the lower right. In the case of a four-parameter affine, in one example, motion vectors of V0 (first control point) and V1 (second control point) are derived. Further, in the case of a 6-parameter affine, motion vectors of V0, V1 and V2 (third control point) are derived. In the example shown in FIG. 15 (d), the width of the block for which the motion vector is predicted is W and the height is H, and the adjacent blocks (in the example of the figure, the adjacent blocks including the block A). The width is w and the height is h.

In the 4-parameter affine, the motion vector (MVN_x, MVN_y) of the control point VN (N = 0.1) is derived by the following equation.

MVN_x = mv_x + ev * xN --rv * yN
MVN_y = mv_y + rv * xN + ev * yN
Here, (ev, rv) is the affine parameter, and (xN, yN) is the relative position seen from the reference point (for example, v0) where the control point VN is located. mv_x and mv_y are translation vectors, for example, motion vectors at point v0 (mv0_x, mv0_y). The translation vector is not limited to (mv0_x, mv0_y), and motion vectors (mv1_x, mv1_y), (mv2_x, mv2_y), (mv3_x, mv3_y) of points v1, point v2, and point v3 may be used.

The relative position of the point Vi starting from the point v0 is derived as follows. First, when the position of the point v0 is (xRef, yRef) and the position of the point Vi is (xPi, yPi), the relative position (xi, yi) of the point Vi starting from the point v0 is from the position of the point Vi. From the difference in position from the starting point v0,
xi = xPi --xRef
yi = yPi --yRef
Will be. In the above example, the position of point v0 is (xP-w, yP + H-h), and the position of points V0, V1, V2 is (xP, yP), (xP + W, yP), (xP, Since yP + H), the relative position (xi, yi) (here i = 0..2) of the point Vi starting from the point v0 is derived as follows.

x0 = xP0 --xRef = xP-(xP --w) = w
y0 = yP0 --yRef = yP-(yP + H --h) = h --H
x1 = xP1 --xRef = (xP + W)-(xP --w) = w + W
y1 = yP1 --yRef = yP-(yP + H --h) = h --H
x2 = xP2 --xRef = xP-(xP --w) = w
y2 = yP2 --yRef = (yP + H)-(yP + H --h) = h
Further, the affine prediction unit 30372 may derive (MVN_x, MVN_y) by an integer operation using the following equation.

MVN_x = mv_x + ((evBW --rvBH) >> 1) + evBW * iN --rvBH * jN
MVN_y = mv_y + ((rvBW + evBH) >> 1) + rvBW * iN + evBH * jN
Here, (evBW, rvBW) and (evBH, rvBH) are the affine parameters, and (iN, jN) are the coordinates in the subblock of the control point VN as a unit. For example, (iN, jN) = (xN >> log2 (W), yN >> log2 (H)). Where W and H are the width and height of the subblock.

In the 6-parameter affine, the motion vector of the control point is derived by the following equation.

MVN_x = mv_x + ev1 * xN + rv2 * yN
MVN_y = mv_y + rv1 * xN + ev2 * yN
Here (ev1, rv1, ev2, rv2) are affine parameters.

Further, the affine prediction unit 30372 may derive (MVN_x, MVN_y) by an integer operation using the following equation.

MVN_x = mv_x + ((ev1BW + rv2BH) >> 1) + ev1BW * iN + rv2BH * jN
MVN_y = mv_y + ((rv1BW + ev2BH) >> 1) + rv1BW * iN + ev2BH * jN
Here, (ev1BW, rv1BW, ev2BH, ev2BH) are affine parameters.

For the derivation method of the above affine parameters (ev, rv), (evBW, rvBW), (evBH, rvBH), (ev1, rv1, ev2, rv2), (ev1BW, rv1BW, ev2BH, ev2BH), see (STEP2 details). It will be described later. When deriving, the control points V0, V1, V2, V3 are replaced with reference points v0, v1, v2, v3 on the adjacent blocks, respectively, and the motion vectors of the control points (MV1_x, MV1_y), (MV2_x, MV2_y) ), (MV3_x, MV3_y) are replaced with motion vectors of reference points (mv0_x, mv0_y), (mv1_x, mv1_y), (mv2_x, mv2_y), (mv3_x, mv3_y), respectively.

Further, the affine prediction unit 30372 is a representative point on the target block from the motion vectors (mv0_x, mv0_y), (mv1_x, mv1_y), (mv2_x, mv2_y) of the points v0, v1 and v2 in FIG. The motion vector of (control points V0, V1 and V2) may be derived. The derivation formula is as follows.

MVi_x = mv0_x + (mv1_x --mv0_x) / w * xi + (mv2_x --mv0_x) / h * yi
MVi_y = mv0_y + (mv1_y --mv0_y) / w * xi + (mv2_y --mv0_y) / h * yi
Here, (xi, yi) are the coordinates of the derivation target points (here, control points V0, V1 and V2) starting from the point v0, and w and h are the reference points v1 and the base reference point v0, respectively. It corresponds to the distance (= X coordinate of point v1-X coordinate of point v0) and the distance between the reference point v2 and the base reference point v0 (= Y coordinate of point v2-Y coordinate of point v0).

In (xi, yi) of the above derivation formula, the position of the point V0 starting from the point v0 of the base reference point (x0, y0) = (w, h --H), the position of the point V1 (x1, y1) = ( Substituting w + W, h --H) to derive the motion vector at point V0 (MV0_x, MV0_y) and the motion vector at point V1 (MV1_x, MV1_y),
MV0_x = mv0_x + (mv1_x --mv0_x) / w * w + (mv2_x --mv0_x) / h * (h --H)
MV0_y = mv0_y + (mv1_y --mv0_y) / w * w + (mv2_y --mv0_y) / h * (h --H)
MV1_x = mv0_x + (mv1_x --mv0_x) / w * (w + W) + (mv2_x --mv0_x) / h * (h --H)
MV1_y = mv0_y + (mv1_y --mv0_y) / w * (w + W) + (mv2_y --mv0_y) / h * (h --H)
Will be.

In STEP 1, the selection of the control point is not limited to the above.

The affine prediction unit 30372 of this configuration derives the motion vector of the control point (V0, V1, V2, V3) from the motion vector of the reference point (v0, v1, v2, v3) of the adjacent block in (STEP1). , (STEP2) is configured to derive the motion vector of the subblock from the motion vector of the control point (V0, V1, V2, V3), but (STEP1) and (STEP2) are integrated and the adjacent block. The motion vector of the subblock may be derived from the motion vector of the reference point (v0, v1, v2, v3) of.

(Details of STEP2)
Subsequently, the process of (STEP2) will be described with reference to FIG. FIG. 16 is a diagram showing an example in which the control point V0 of the target block (width W, height H) is located at the upper left apex and is divided into sub-blocks of width BW and height BH. (W, H) and (BW, BH) correspond to the above-mentioned (nPbW, nPbH) and (nSbW, nSbH).

The affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) refers to the motion vector of two or three control points V0, V1 and V2, which are representative points on the block, derived in (STEP1). Then, in (STEP2), the affine parameter is calculated. That is, the affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) performs any of the following processes.
-Affine parameters (ev, rv) from two motion vectors of the motion vector of control point V0 (MV0_x, MV0_y), the motion vector of control point V1 (MV1_x, MV1_y) and the motion vector of control point V2 (MV2_x, MV2_y). ) Is derived.
-Affine parameters (ev1, rv1, Derived ev2, ev2).

In the following description, the process of deriving affine parameters (ev, rv) from two motion vectors is referred to as "four-parameter affine". Further, the process of deriving the affine parameters (ev1, rv1, ev2, ev2) from the three motion vectors is referred to as "6 parameter affine".

Affin parameters can also be treated as integers instead of decimal points. Below, the decimal point affine parameters are (ev, rv), (ev1, rv1, ev2, ev2), and the integer affine parameters are (evBW, rvBW), (evBH, rvBH), (ev1BW, rv1BW, ev2BH, ev2BH). It is expressed as.

The integer affine parameter is obtained by multiplying the decimal point affine parameter by a constant (constant for integer conversion) corresponding to the subblock size (BW, BH). Specifically, there is the following relationship between the affine parameter of the decimal point and the affine parameter of the integer.

evBW = ev * BW = ev << log2 (BW)
rvBW = rv * BW = rv << log2 (BW)
evBH = ev * BH = ev << log2 (BH)
rvBH = rv * BH = rv << log2 (BH)
ev1BW = ev1 * BW = ev1 << log2 (BW)
rv1BW = rv1 * BH = rv1 << log2 (BW)
ev2BH = ev2 * BW = ev2 << log2 (BH)
rv2BH = rv2 * BH = rv2 << log2 (BH)
If the width BW and height BH of the subblock are equal, (evBW, rvBW) = (evBH, rvBH), so it is not necessary to distinguish between (evBW, rvBW) and (evBH, rvBH). That is, in deriving the following affine parameters, it is sufficient to derive only (evBW, rvBW) or only (evBH, rvBH).

For example, when the motion vectors of the control points V0 and V1 are used, the affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) uses the following equation to set the affine parameters.
evBW = (MV1_x --MV0_x) >> shiftWBW
rvBW = (MV1_y --MV0_y) >> shiftWBW
evBH = (MV1_x --MV0_x) >> shiftWBH
rvBH = (MV1_y --MV0_y) >> shiftWBH
shiftWBW = log2 (W) --log2 (BW)
shiftHBH = log2 (H) --log2 (BH)
Is derived.

When using the decimal point affine parameter, use the following formula.
ev = (MV1_x --MV0_x) / W
rv = (MV1_y --MV0_y) / W
May be derived. In this equation, the position of the general expression control point V0 is (0, 0) and the position of the control point V1 is (W, 0).

Further, when the motion vectors of the control points V0 and V2 are used, the affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) uses the following equation to set the affine parameters.
evBW = (MV2_y --MV0_y) >> shiftHBW
rvBW =-(MV2_x --MV0_x) >> shiftHBW
evBH = (MV2_y --MV0_y) >> shiftHBH
rvBH =-(MV2_x --MV0_x) >> shiftHBH
shiftHBW = log2 (H) --log2 (BW)
shiftHBH = log2 (H) --log2 (BH)
Is derived. This formula is a derivation formula for the following decimal point affine parameters.
ev = (MV2_y --MV0_y) / H
rv =-(MV2_x --MV0_x) / H
Is equal to.

When the motion vectors of the control points V1 and V2 are used, the affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) uses the following equation to set the affine parameters.
evBW = {(MV1_x --MV2_x)-(MV1_y --MV2_y)} >> (shiftWBW + 1)
rvBW = {(MV1_x --MV2_x) + (MV1_y --MV2_y)} >> (shiftWBW + 1)
evBH = {(MV1_x --MV2_x)-(MV1_y --MV2_y)} >> (shiftWBH + 1)
rvBH = {(MV1_x --MV2_x) + (MV1_y --MV2_y)} >> (shiftWBH + 1)
Is derived. This formula is a derivation formula for the following decimal point affine parameters.
ev = {(MV1_x --MV2_x)-(MV1_y --MV2_y)} / 2W
rv = {(MV1_x --MV2_x) + (MV1_y --MV2_y)} / 2W
Is equal to.

Further, it is also possible to use a motion vector of the control point V3 (control point located diagonally to V0 in the target block), which is different from any of the control points V0 to V2 described above. For example, when the motion vectors of the control points V0 and V3 are used, the affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) uses the following equation to set the affine parameters.
evBW = (MV3_x --MV0_x + MV3_y --MV0_y) >> (shiftWBW + 1)
rvBW = (-MV3_x + MV0_x + MV3_y --MV0_y) >> (shiftWBW + 1)
evBH = (MV3_x --MV0_x + MV3_y --MV0_y) >> (shiftWBH + 1)
rvBH = (-MV3_x + MV0_x + MV3_y --MV0_y) >> (shiftWBH + 1)
Is derived. This formula is a derivation formula for the following decimal point affine parameters.
ev = (MV3_x --MV0_x + MV3_y --MV0_y) / 2W
rv = (-MV3_x + MV0_x + MV3_y --MV0_y) / 2W
Is equal to.

When three motion vectors of control points V0, V1 and V2 are used, the affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) uses the following equation to set the affine parameters.
ev1BW = (MV1_x --MV0_x) >> shiftWBW
rv2BH = (MV2_x --MV0_x) >> shiftHBH
rv1BW = (MV1_y --MV0_y) >> shiftWBW
ev2BH = (MV2_y --MV0_y) >> shiftHBH
shiftWBW = log2 (W) --log2 (BW)
shiftHBH = log2 (H) --log2 (BH)
Is derived. This formula is a derivation formula for the following decimal point affine parameters.
ev1 = (MV1_x --MV0_x) / W
rv2 = (MV2_x --MV0_x) / H
rv1 = (MV1_y --MV0_y) / W
ev2 = (MV2_y --MV0_y) / H
Is equal to.

(Derivation of motion vector of subblock)
The affine prediction unit 30372 (AMVP prediction parameter derivation unit 3032) derives the motion vector of the subblock using the affine parameter obtained by the above equation.

In the case of 4-parameter affine, the motion vector (MVi_x, MVi_y) of the subblock of the subblock coordinates (xi, yi) is derived from the affine parameter (ev, rv) by the following equation AF4P_float.

MVi_x = mv_x + ev * xi --rv * yi
MVi_y = mv_y + rv * xi + ev * yi (Expression AF4P_float)
(MV0_x, MV0_y) may be used as the affine parameters mv_x, mv_y of the translation vector, but the present invention is not limited to this. For example, motion vectors (MV1_x, MV1_y) other than (MV0_x, MV0_y), (MV2_x, MV2_y), and (MV3_x, MV3_y) may be translation vectors. In particular, when V1 and V2 are used as control points, the motion vector of V1 (MV1_x, MV1_y) or the motion vector of V2 (MV2_x, MV2_y) may be a translation vector.

If the affine parameters are integer affine parameters (evBW, rvBW) and (evBH, rvBH), the motion vector (MVij_x, MVij_y) of the subblock at the subblock position (i, j) is derived by the following equation AF4P_integer. do.

MVij_x = mv_x + ((evBW --rvBH) >> 1) + evBW * i --rvBH * j
MVij_y = mv_y + ((rvBW + evBH) >> 1) + rvBW * i + evBH * j (expression AF4P_integer)
When (MV0_x, MV0_y) is used as the translation vector, the above equation becomes the following equation.

MVij_x = MV0_x + ((evBW --rvBH) >> 1) + evBW * i --rvBH * j
MVij_y = MV0_y + ((rvBW + evBH) >> 1) + rvBW * i + evBH * j
If the width BW and height BH of the subblock are equal, (evBW, rvBW) = (evBH, rvBH)
Therefore, it is not necessary to distinguish between (evBW, rvBW) and (evBH, rvBH) in the above derivation formula. That is, it may be derived only from (evBW, rvBW).

MVij_x = mv_x + ((evBW + rvBW) >> 1) + evBW * i --rvBW * j
MVij_y = mv_y + ((rvBW + evBW) >> 1) + rvBW * i + evBW * j
Further, it may be derived only from (evBH, rvBH).

MVij_x = mv_x + ((evBH + rvBH) >> 1) + evBH * i --rvBH * j
MVij_y = mv_y + ((rvBH + evBH) >> 1) + rvBH * i + evBH * j
Here, the relationship between the sub-block position (i, j) and the sub-block coordinates (xi, yj) is as follows (Equation XYIJ).

xi = BW / 2 + BW * i
yj = BH / 2 + BH * j (Equation XYIJ)
i = 0 .. (B / SW) -1, j = 0 .. (H / SH) -1
The point at the subblock position (i, j) is the intersection of the solid line parallel to the x-axis and the solid line parallel to the y-axis in FIG. The points of the sub-block coordinates (xi, yj) are the intersections of the broken line parallel to the x-axis and the broken line parallel to the y-axis in FIG. FIG. 16 shows, as an example, a point at the subblock position (i, j) = (1, 1) and a point at the subblock coordinates (x1, y1) with respect to the subblock position.

The integer derivation formula from the decimal point derivation formula can be obtained by the following transformation. Substituting the above-mentioned formula XYIJ into (xi, yi) of the above-mentioned decimal point formula AF4P_float and transforming it
MVij_x = mv_x + ev * (BW / 2 + BW * i) --rv * (BH / 2 + BH * j)
MVij_y = mv_y + rv * (BW / 2 + BW * i) + ev * (BH / 2 + BH * j)
Will be. When transformed further,
MVij_x = mv_x + ev * BW * (1/2 + i) --rv * BH * (1/2 + j)
MVij_y = mv_y + rv * BW * (1/2 + i) + ev * BH * (1/2 + j)
Will be. Furthermore, when transformed by ev * BW = evBW, rv * BH = rvBH, rv * BW = rvBW, ev * BH = evBH,
MVij_x = MV0_x + evBW * (1/2 + i) --rvBH * (1/2 + j)
MVij_y = MV0_y + rvBW * (1/2 + i) + evBH * (1/2 + j)
Will be. When transformed further,
MVij_x = MV0_x + evBW / 2 --rvBH / 2 + evBW * i --rvBH * j
MVij_y = MV0_y + rvBW / 2 + evBH / 2 + rvBW * i + evBH * j
Finally, the above-mentioned integer arithmetic expression AF4P_integer
MVij_x = mv_x + ((evBW --rvBH) >> 1) + evBW * i --rvBH * j
MVij_y = mv_y + ((rvBW + evBH) >> 1) + rvBW * i + evBH * j
Will be. It is advisable to use (MV0_x, MV0_y) as the affine parameters mv_x, mv_y of the translation vector, but the present invention is not limited to this. For example, motion vectors (MV1_x, MV1_y), (MV2_x, MV2_y), and (MV3_x, MV3_y) may be translation vectors.

In the case of 6-parameter affine, from the affine parameters (ev1, rv1, ev2, ev2), the motion vector (MVij_x, MVij_y) of the subblock of the subblock coordinates (xi, yi) is calculated by the following formula AF6P_float.
MVij_x = mv_x + ev1 * xi + rv2 * yi
MVij_y = mv_y + rv1 * xi + ev2 * yi (expression AF6P_float)
Is derived.

If the affine parameters (ev1, rv1, ev2, ev2) are integer affine parameters (ev1BW, rv1BH, ev2BW, ev2BH), the motion vector (MVij_x, MVij_y) of the subblock at the subblock position (i, j) ) Is derived by the following equation AF6P_integer.

MVij_x = mv_x + ((ev1BW + rv2BH) >> 1) + ev1BW * i + rv2BH * j
MVij_y = mv_y + ((rv1BW + ev2BH) >> 1) + rv1BW * i + ev2BH * j (expression AF6P_integer)
For example, when (MV0_x, MV0_y) is used as the translation vector, the above equation becomes the following equation.

MVij_x = MV0_x + ((ev1BW + rv2BH) >> 1) + ev1BW * i + rv2BH * j
MVij_y = MV0_y + ((rv1BW + ev2BH) >> 1) + rv1BW * i + ev2BH * j (expression AF6P_integer)
The integer derivation formula from the decimal point derivation formula can be obtained by the following transformation. When the above formula XYIJ is substituted into (xi, yi) of the above-mentioned decimal point formula AF6P_float to transform the formula,
MVij_x = mv_x + ev1 * (BW / 2 + BW * i) + rv2 * (BH / 2 + BH * j)
MVij_y = mv_y + rv1 * (BW / 2 + BW * i) + ev2 * (BH / 2 + BH * j)
Will be. When transformed further,
MVij_x = mv_x + ev1 * BW * (1/2 + i) + rv2 * BH * (1/2 + j)
MVij_y = mv_y + rv1 * BW * (1/2 + i) + ev2 * BH * (1/2 + j)
Will be. Furthermore, when transformed by ev1 * BW = ev1BW, rv2 * BH = rv2BH, rv1 * BW = rv1BW, ev2 * BH = ev2BH,
MVij_x = mv_x + ev1BW * (1/2 + i) + rv2BH * (1/2 + j)
MVij_y = mv_y + rv1BW * (1/2 + i) + ev2BH * (1/2 + j)
Will be. When transformed further,
MVij_x = mv_x + ev1BW / 2 + rv2BH / 2 + ev1BW * i + rv2BH * j
MVij_y = mv_y + rv1BW / 2 + ev2BH / 2 + rv1BW * i + ev2BH * j
Finally, the above-mentioned integer arithmetic derivation formula AF6P_integer
MVij_x = mv_x + ((ev1BW + rv2BH) >> 1) + ev1BW * i + rv2BH * j
MVij_y = mv_y + ((rv1BW + ev2BH) >> 1) + rv1BW * i + ev2BH * j
Will be.

(Determining control points)
The inter-prediction parameter decoding unit 303 determines whether to execute the 4-parameter affine or the 6-parameter affine process by a predetermined process. An example of a predetermined process is shown below. In the flowchart used in the following description, puWidth indicates the width of the target PU, and puHeight indicates the height of the target PU. (PuWidth, puHeight) corresponds to the above-mentioned (nPbW, nPbH).

(Determined by the shape of the target PU)
FIG. 17 is a flowchart showing an example of a process in which the inter-prediction parameter decoding unit 303 determines the number of control points for deriving a motion vector based on the shape of the target PU. In the example shown in FIG. 17, in the inter-prediction parameter decoding unit 303, first, the inter-prediction parameter decoding control unit 3031 determines whether the width of the target PU and the height of the target PU are equal (SA1). When the width of the target PU and the height of the target PU are equal (Y in SA1), the affine prediction unit 30372 (or the AMVP prediction parameter decoding unit 3032) performs the processing of the 6-parameter affine (SA2). When the width of the target PU and the height of the target PU are not equal (N in SA1), the affine prediction unit 30372 (or the AMVP prediction parameter decoding unit 3032) performs the processing of the four-parameter affine (SA3).

The determination in SA1 is equivalent to determining whether or not the target PU is a square. That is, in the example shown in FIG. 17, the processing of the 6-parameter affine is performed when the target PU is square, and the processing of the 4-parameter affine is performed when the target PU is not square.

Further, the process of deriving the motion vector based on the shape of the target PU may be applied only in the case of the merge mode or may be applied only in the case of AMVP. FIG. 18 is a flowchart showing another example of the process in which the affine prediction unit 30372 determines the number of control points for deriving a motion vector based on the shape of the target PU. In the example shown in FIG. 18, prior to the processing of SA1 shown in FIG. 17, the inter-prediction parameter decoding control unit 3031 determines whether the merge flag is 1 (SB1). When the merge flag is 1, that is, when the merge mode is set (Y in SB1), the inter-prediction parameter decoding unit 303 performs the processes of SB2 to SB4. The processing of SB2 to SB4 is the same as the processing of SA1 to SA3 shown in FIG. On the other hand, when the merge flag is 0, that is, when the merge mode is not set (N in SB1), the inter-prediction parameter decoding unit 303 performs the motion vector derivation process of AMVP.

In the example shown in FIG. 18, the affine prediction unit 30372 derives the affine parameter according to whether or not the target PU is square when the merge flag is 1. However, the affine prediction unit 30372 of the present embodiment, contrary to the example shown in FIG. 18, has an affine parameter depending on whether the target PU is square or not when the merge flag is 0, that is, when it is AMVP. Derivation may be performed. In this case, the derivation of the affine parameter is executed by the AMVP prediction parameter derivation unit 3032. Further, the derivation of the motion vector of the control point is performed according to the above-mentioned (derivation of the motion vector of the control point in the AMVP mode).

Although not described above, the inter-prediction parameter decoding unit 303 may decode the affine application flag pu_affine_enable_flag, which is a flag indicating whether or not to perform affine prediction. The inter-prediction parameter decoding unit 303 performs affine prediction processing when the affine application flag pu_affine_enable_flag indicates that the affine prediction is applied, and does not apply the affine prediction when the affine application flag pu_affine_enable_flag is 0. ..

FIG. 19 is a flowchart showing still another example of the process in which the inter-prediction parameter decoding unit 303 determines the number of control points for deriving a motion vector based on the shape of the target PU.

In the example shown in FIG. 19, in the case of AMVP, when the shape of the target PU is square, the PU affine mode flag, which is a flag indicating 6-parameter affine and 4-parameter affine, is decoded, and in other cases, the PU affine mode flag is decoded. Do not decrypt the PU affine mode flag. More specifically, the inter-prediction parameter decoding control unit 3031 first determines whether the merge flag is 1 (SC1). When the merge flag is 0 (indicating that the merge process is not performed) (N in SC1), the inter-prediction parameter decoding control unit 3031 determines whether the width of the target PU and the height of the target PU are equal (N). SC2). When the width of the target PU and the height of the target PU are equal (Y in SC2), the inter-prediction parameter decoding control unit 3031 decodes the PU affine mode flag (SC3). After that, the inter-prediction parameter decoding control unit 3031 determines whether the PU affine mode flag is 1 (SC4).

The AMVP prediction parameter derivation unit 3032 performs 6-parameter affine processing when the PU affine mode flag is 1 (indicating that 6-parameter affine processing is performed) (Y in SC4), and the PU affine mode flag. When is 0 (N in SC4), the processing of the 4-parameter affine is performed. Further, the AMVP prediction parameter derivation unit 3032 also performs the 4-parameter affine process when the width of the target PU and the height of the target PU are not equal (N in SC2). On the other hand, when the merge flag is 1 (Y in SC1), the motion vector is derived by the merge prediction.

In this configuration, the inter-prediction parameter decoding unit 303 calculates motion vectors of two control points and performs processing of four-parameter affine according to the shape of the target block, or calculates motion vectors of three control points. 6 Switch whether to process the parameter affine. When applied to AMVP, SC1 encodes / decodes a two-point motion vector (difference vector) or encodes / decodes a three-point motion vector (difference vector) according to the shape of the target block. May be switched. When applying to merging, in SC1, the motion vector of the control point is derived by referring to the motion vector of two points according to the shape of the target block, or the motion vector of the control point is derived by referring to the motion vector of three points. You may switch whether to derive the vector. In SC2, whether to derive the motion vector of each subblock by referring to the motion vector of two points or to derive the motion vector of each subblock by referring to the motion vector of three points according to the shape of the target block. , May be switched.

(Determined by the size of the target PU)
FIG. 20 is a flowchart showing an example of a process in which the inter-prediction parameter decoding unit 303 determines the number of control points for deriving a motion vector based on the size of the target PU. In the example shown in FIG. 20, the inter-prediction parameter decoding control unit 3031 first determines whether or not the value indicating the size of the target PU is equal to or greater than a predetermined threshold value (SD1). When the size of the target PU is equal to or larger than a predetermined threshold value (Y in SD1), the affine prediction unit 30372 processes the 6-parameter affine (SD2). When the size of the target PU is not equal to or larger than a predetermined threshold value (N in SD1), the affine prediction unit 30372 processes the four-parameter affine (SD3).

As a value indicating the size of the target PU, for example, the following can be used.
・ Max (puWidth, puHeight)
・ Min (puWidth, puHeight)
・ PuWidth + puHeight
・ PuWidth * puHeight
・ Log2 (puWidth) + log2 (puHeight)
However, the value indicating the size of the target PU is not limited to the above example.

Further, the determination in SD1 may be as follows.
-Is the size of the target PU larger than the specified threshold?
-Is the size of the target PU less than or equal to the specified threshold?
-Is the size of the target PU smaller than the specified threshold?

FIG. 21 is a flowchart showing another example of the process in which the inter-prediction parameter decoding unit 303 determines the number of control points for deriving a motion vector based on the size of the target PU. In the example shown in FIG. 21, in the case of AMVP, if the size of the target PU is large, the PU affine mode flag, which is a flag indicating the 6-parameter affine and the 4-parameter affine, is decoded, and in other cases, the PU affine is decoded. Do not decode the mode flag. More specifically, as in the example shown in FIG. 19, the inter-prediction parameter decoding control unit 3031 first determines whether the merge flag is 1 (SE1). When the merge flag is 0 (N in SE1), the inter-prediction parameter decoding control unit 3031 determines whether the size of the target PU is equal to or larger than a predetermined threshold value (SE2). Based on the determination result of SE2, the inter-prediction parameter decoding unit 303 performs the processing of SE3 to SE6. The processing of SE3 to SE6 is the same as the processing of SC3 to SC6 shown in FIG. 19, respectively.

FIG. 22 is a table showing processing for each size when log2 (puWidth) + log2 (puHeight) is used as a value indicating the size of the target PU. In the example shown in FIG. 22, the threshold value for determination is 8. In this case, in the example shown in FIG. 22, if log2 (puWidth) + log2 (puHeight) is 6 or 7, the affine prediction unit 30372 processes the 4-parameter affine regardless of the shape of the target PU. If log2 (puWidth) + log2 (puHeight) is 8, the affine prediction unit 30372 processes the 6-parameter affine regardless of the shape of the target PU.

FIG. 23 is a table showing processing for each size when min (puWidth, puHeight) is used as a value indicating the size of the target PU. In the example shown in FIG. 23, the determination threshold is set to 8. In this case, as shown in FIG. 23, if min (puWidth, puHeight) is 4, the affine prediction unit 30372 processes the 4-parameter affine regardless of the shape of the target PU. If min (puWidth, puHeight) is 8 or 16, the affine prediction unit 30372 processes the 6-parameter affine regardless of the shape of the target PU.

In this configuration, the inter-prediction parameter decoding unit 303 calculates motion vectors of two control points and performs processing of four-parameter affine, or calculates motion vectors of three control points, depending on the size of the target block. 6 Switch whether to process the parameter affine. When applied to AMVP, SE1 encodes / decodes a two-point motion vector (difference vector) or encodes / decodes a three-point motion vector (difference vector) according to the size of the target block. You may switch between. When applying to merging, in SE1, the motion vector of the control point is derived by referring to the motion vector of two points according to the size of the target block, or the motion vector of the control point is derived by referring to the motion vector of three points. You may switch whether to derive the vector. In SE2, whether to derive the motion vector of each subblock by referring to the motion vector of two points or to derive the motion vector of each subblock by referring to the motion vector of three points according to the size of the target block. , May be switched.

(Determined by the shape and size of the target PU)
FIG. 24 is a flowchart showing an example of a process in which the inter-prediction parameter decoding unit 303 determines the number of control points for deriving a motion vector based on both the shape and size of the target PU. In the example shown in FIG. 24, the inter-prediction parameter decoding control unit 3031 first determines whether the size of the target PU is equal to or larger than a predetermined threshold value (SF1). When the size of the target PU is equal to or larger than a predetermined threshold value (Y in SF1), the affine prediction unit 30372 processes the 6-parameter affine (SF3).

When the size of the target PU is not equal to or larger than a predetermined threshold value (N in SF1), the inter-prediction parameter decoding control unit 3031 continuously determines whether the width of the target PU and the height of the target PU are equal (SF2). When the width of the target PU and the height of the target PU are equal (Y in SF2), the affine prediction unit 30372 processes the 6-parameter affine (SF3). When the width of the target PU and the height of the target PU are not equal (N in SF2), the affine prediction unit 30372 processes the four-parameter affine (SF4).

That is, in the example shown in FIG. 24, when the target PU has a predetermined size or more or is square, the affine prediction unit 30372 processes the 6-parameter affine. On the other hand, when the target PU is smaller than a predetermined size and is not a square, the affine prediction unit 30372 processes the four-parameter affine.

FIG. 25 is a flowchart showing another example of the process in which the inter-prediction parameter decoding unit 303 determines the number of control points for deriving a motion vector based on both the shape and size of the target PU. In the example shown in FIG. 25, similarly to the examples shown in FIGS. 19 and 21, the inter-prediction parameter decoding control unit 3031 first determines whether the merge flag is 1 (SG1). When the merge flag is 0 (N in SE1), the inter-prediction parameter decoding control unit 3031 determines the size and shape of the target PU in the same manner as SF1 and SF2 shown in FIG. 24 (SG2, SG3). When the size of the target PU is equal to or larger than a predetermined threshold value (Y in SG2), or when the size of the target PU is not equal to or larger than the predetermined threshold value (N in SG2) and the target PU is square (Y in SG3). The affine prediction unit 30372 performs processing of SG4 to SG7 (similar to SC3 to SC6 shown in FIG. 19).

FIG. 26 is a table showing an example of processing of the affine prediction unit 30372 for each size and shape of the target PU. In the example shown in FIG. 26, log2 (puWidth) + log2 (puHeight) is used as a value indicating the size of the target PU, and the threshold value is set to 8.

In the example shown in FIG. 26, when the value indicating the size of the target PU is 6 or 7, the affine prediction unit 30372 has 6 parameters only when the symmetric PU is square (8 * 8 in FIG. 26). Process the affine. In other cases, the affine prediction unit 30372 processes the four-parameter affine. On the other hand, when the size of the target PU is 8, the affine prediction unit 30372 processes the 6-parameter affine regardless of the shape of the target PU.

FIG. 27 is a table showing another example of processing of the affine prediction unit 30372 for each size and shape of the target PU. In the example shown in FIG. 27, min (puWidth, puHeight) is used as a value indicating the size of the target PU, and the threshold value is 16.

In the example shown in FIG. 27, when the value indicating the size of the target PU is 4 or 8, the affine prediction unit 30372 has 6 parameters only when the target PU is square (8 * 8 in FIG. 27). Process the affine. In other cases, the affine prediction unit 30372 processes the four-parameter affine. On the other hand, when the size of the target PU is 16, the affine prediction unit 30372 processes the 6-parameter affine.

In this configuration, the inter-prediction parameter decoding unit 303 calculates motion vectors of two control points and performs processing of four-parameter affine, or calculates motion vectors of three control points, according to the shape and size of the target block. Then, it is switched whether to process the 6-parameter affine. When applied to AMVP, SG1 encodes / decodes two motion vectors (difference vector) according to the shape and size of the target block, or encodes / decodes three motion vectors (difference vector). You may switch whether to decrypt. When applying to merging, in SG1, the motion vector of the control point is derived by referring to the motion vector of two points according to the shape and size of the target block, or the motion vector of the control point is derived by referring to the motion vector of three points. You may switch whether to derive the motion vector of. In SG2, the motion vector of each subblock is derived by referring to the motion vector of two points, or the motion vector of each subblock is derived by referring to the motion vector of three points according to the shape and size of the target block. You may switch between.

(Matching prediction unit 30373)
The matching prediction unit 30373 derives the motion vector spMvLX of the subblocks constituting the PU by performing matching processing of either bilateral matching or template matching. FIG. 14 is a diagram for explaining (a) bilateral matching and (b) template matching. The matching prediction mode is selected as one merge candidate (matching candidate) in the merge mode.

The matching prediction unit 30373 derives a motion vector by matching regions in a plurality of reference images, assuming that the object moves at a constant velocity. In bilateral matching, matching between reference images A and B is performed on the assumption that an object passes through a certain area of the reference image A, a target PU of the target picture Cur_Pic, and a certain area of the reference image B in a constant velocity motion. To derive the motion vector of the target PU. In template matching, assuming that the motion vector of the target PU is equal to the motion vector of the target PU, the motion vector is derived by matching the motion vector of the target PU adjacent region Temp_Cur and the reference block adjacent region Temp_L0 on the reference picture. In the matching prediction unit, the target PU is divided into multiple subblocks, and the motion vector spMvLX [xi] [yj] (xi =) of the subblocks is performed by performing bilateral matching or template matching described later in each divided subblock. xPb + nSbW * i, yj = yPb + nSbH * j, i = 0, 1, 2, ・ ・ ・, nPbW / nSbW -1 、 j = 0, 1, 2, ・ ・ ・, nPbH / nSbH ―― 1) Is derived.

As shown in FIG. 14A, in bilateral matching, two reference images are referred to in order to derive the motion vector of the subblock Cur_block in the target picture Cur_Pic. More specifically, first, when the coordinates of the subblock Cur_block are expressed as (xCur, yCur), it is a region in the reference image (referred to as reference picture A) specified by the reference picture index Ref0.
(XPos0, yPos0) = (xCur + MV0_x, yCur + MV0_y)
Block_A with the upper left coordinates (xPos0, yPos0) specified by and the area within the reference image (referred to as reference picture B) specified by the reference picture index Ref1.
(XPos1, yPos1) = (xCur + MV1_x, xCur + MV1_y) = (xCur --MV0_x * TD1 / TD0, yCur --MV0_y * TD1 / TD0)
Block_B with the upper left coordinates (xPos1, yPos1) specified by is set. Here, TD0 and TD1 represent the distance between the target picture Cur_Pic and the reference picture A, and the distance between the target picture Cur_Pic and the reference picture B, respectively, as shown in FIG. 14 (a). ing.

Next, (MV0_x, MV0_y) is determined so that the matching cost between Block_A and Block_B is minimized. The motion vector derived in this way (MV0_x, MV0_y) is a motion vector given to the subblock.

On the other hand, FIG. 14B is a diagram for explaining template matching among the above matching processes.

As shown in FIG. 14 (b), in template matching, one reference picture is referred to in order to derive the motion vector of the subblock Cur_block in the target picture Cur_Pic.

More specifically, first, it is a region in the reference image (referred to as reference picture A) specified by the reference picture index Ref0.
(XPos0, yPos0) = (xCur + MV0_x, yCur + MV0_y)
The reference block Block_A with the upper left coordinates (xPos0, yPos0) specified by is specified. Here, (xCur, yCur) is the upper left coordinate of the subblock Cur_block.

Next, the template area Temp_Cur adjacent to the subblock Cur_block in the target picture Cur_Pic and the template area Temp_L0 adjacent to Block_A in the reference picture A are set. In the example shown in FIG. 14 (b), the template region Temp_Cur is composed of a region adjacent to the upper side of the subblock Cur_block and a region adjacent to the left side of the subblock Cur_block. Further, the template area Temp_L0 is composed of an area adjacent to the upper side of Block_A and an area adjacent to the left side of Block_A.

Next, the matching cost between Temp_Cur and TempL0 is determined to be the minimum (MV0_x, MV0_y), and it becomes the motion vector spMvLX given to the subblock.

FIG. 7 is a schematic diagram showing the configuration of the merge prediction parameter derivation unit 3036 according to the present embodiment. The merge prediction parameter derivation unit 3036 includes a merge candidate derivation unit 30361, a merge candidate selection unit 30632, and a merge candidate storage unit 30363. The merge candidate storage unit 30363 stores the merge candidates input from the merge candidate derivation unit 30361. The merge candidate includes the prediction list usage flag predFlagLX, the motion vector mvLX, and the reference picture index refIdxLX. In the merge candidate storage unit 30363, an index is assigned to the stored merge candidates according to a predetermined rule.

The merge candidate derivation unit 30361 derives the merge candidate by using the motion vector of the adjacent PU that has already been decoded and the reference picture index refIdxLX as they are. Alternatively, affine prediction may be used to derive merge candidates. This method will be described in detail below. The merge candidate derivation unit 30361 may use the affine prediction for the spatial merge candidate derivation process, the time merge candidate derivation process, the join merge candidate derivation process, and the zero merge candidate derivation process, which will be described later. The affine prediction is performed in sub-block units, and the prediction parameters are stored in the prediction parameter memory 307 for each sub-block. Alternatively, the affine prediction may be performed on a pixel-by-pixel basis.

(Spatial merge candidate derivation process)
As the spatial merge candidate derivation process, the merge candidate derivation unit 30361 reads and reads the prediction parameters (prediction list usage flag predFlagLX, motion vector mvLX, reference picture index refIdxLX) stored in the prediction parameter memory 307 according to a predetermined rule. The predicted parameters are derived as merge candidates. The predicted parameters to be read are prediction parameters related to each of the PUs within a predetermined range from the target PU (for example, all or a part of the PUs in contact with the left lower end, the upper left end, and the upper right end of the target PU). The merge candidate derived by the merge candidate derivation unit 30361 is stored in the merge candidate storage unit 30363.

(Time merge candidate derivation process)
As the time merge derivation process, the merge candidate derivation unit 30361 reads the prediction parameter of the PU in the reference image including the lower right coordinates of the target PU from the prediction parameter memory 307 and sets it as a merge candidate. The method for specifying the reference image may be, for example, the reference picture index refIdxLX specified in the slice header, or may be specified using the smallest reference picture index refIdxLX of the PU adjacent to the target PU. The merge candidate derived by the merge candidate derivation unit 30361 is stored in the merge candidate storage unit 30363.

(Join merge candidate derivation process)
As a merge merge derivation process, the merge candidate derivation unit 30361 uses the motion vectors and reference picture indexes of two different derived merge candidates that have already been derived and stored in the merge candidate storage unit 30363 as motion vectors of L0 and L1, respectively. Derivation of join merge candidates by combining. The merge candidate derived by the merge candidate derivation unit 30361 is stored in the merge candidate storage unit 30363.

(Zero merge candidate derivation process)
As the zero merge candidate derivation process, the merge candidate derivation unit 30361 derives a merge candidate in which the reference picture index refIdxLX is 0 and the X component and the Y component of the motion vector mvLX are both 0. The merge candidate derived by the merge candidate derivation unit 30361 is stored in the merge candidate storage unit 30363.

Among the merge candidates stored in the merge candidate storage unit 30363, the merge candidate selection unit 30632 selects the merge candidate to which the index corresponding to the merge index merge_idx input from the inter-prediction parameter decoding control unit 3031 is assigned to the target PU. Select as an inter-prediction parameter for. The merge candidate selection unit 30362 stores the selected merge candidate in the prediction parameter memory 307 and outputs the selected merge candidate to the prediction image generation unit 308.

FIG. 8 is a schematic diagram showing the configuration of the AMVP prediction parameter derivation unit 3032 according to the present embodiment. The AMVP prediction parameter derivation unit 3032 includes a vector candidate derivation unit 3033, a vector candidate selection unit 3034, and a vector candidate storage unit 3035. The vector candidate derivation unit 3033 derives a prediction vector candidate from the motion vector of the already processed PU stored in the prediction parameter memory 307 based on the reference picture index refIdx, and the prediction vector candidate list mvpListLX [] of the vector candidate storage unit 3035. Store in.

The vector candidate selection unit 3034 selects the motion vector mvpListLX [mvp_LX_idx] indicated by the prediction vector index mvp_LX_idx among the prediction vector candidates of the prediction vector candidate list mvpListLX [] as the prediction vector mvpLX. The vector candidate selection unit 3034 outputs the selected prediction vector mvpLX to the addition unit 3035.

The prediction vector candidate is a PU for which decoding processing has been completed, and is derived by scaling the motion vector of a PU (for example, an adjacent PU) in a predetermined range from the target PU. The adjacent PU includes a PU spatially adjacent to the target PU, for example, the left PU, the upper PU, and an area temporally adjacent to the target PU, for example, the same position as the target PU, and the display times are different. Includes regions obtained from PU prediction parameters.

The addition unit 3035 calculates the motion vector mvLX by adding the prediction vector mvpLX input from the AMVP prediction parameter derivation unit 3032 and the difference vector mvdLX input from the inter-prediction parameter decoding control unit 3031. The addition unit 3035 outputs the calculated motion vector mvLX to the prediction image generation unit 308 and the prediction parameter memory 307.

(Inter prediction image generation unit 309)
FIG. 11 is a schematic diagram showing the configuration of the inter-prediction image generation unit 309 included in the prediction image generation unit 308 according to the present embodiment. The inter-prediction image generation unit 309 includes a motion compensation unit (prediction image generation device) 3091 and a weight prediction unit 3094.

(Motion compensation)
The motion compensation unit 3091 has a reference picture index refIdxLX from the reference picture memory 306 based on the inter-prediction parameters (prediction list utilization flag predFlagLX, reference picture index refIdxLX, motion vector mvLX) input from the inter-prediction parameter decoding unit 303. In the reference picture specified in, an interpolated image (motion compensation image) is generated by reading a block at a position shifted by the motion vector mvLX from the position of the target PU. Here, when the accuracy of the motion vector mvLX is not an integer accuracy, a filter called a motion compensation filter for generating pixels at decimal positions is applied to generate a motion compensation image.

(Weight prediction)
The weight prediction unit 3094 generates a prediction image of the PU by multiplying the input motion compensation image predSamplesLX by a weight coefficient. When one of the prediction list usage flags (predFlagL0 or predFlagL1) is 1 (in the case of simple prediction), and when weight prediction is not used, the input motion compensation image predSamplesLX (LX is L0 or L1) is the number of pixel bits bitDepth. Perform the following formula processing to match.

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth) --1, (predSamplesLX [X] [Y] + offset1) >> shift1)
Here, shift1 = 14 --bitDepth, offset1 = 1 << (shift1-1).
If both of the reference list usage flags (predFlagL0 and predFlagL1) are 1 (in the case of biprediction BiPred) and weight prediction is not used, the input motion compensation images predSamplesL0 and predSamplesL1 are averaged and the number of pixel bits. Perform the following formula processing to match.

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth) --1, (predSamplesL0 [X] [Y] + predSamplesL1 [X] [Y] + offset2) >> shift2)
Here, shift2 = 15-bitDepth, offset2 = 1 << (shift2-1).

Further, in the case of simple prediction, when weight prediction is performed, the weight prediction unit 3094 derives the weight prediction coefficient w0 and the offset o0 from the coded data, and performs the processing of the following equation.

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth) ―― 1, ((predSamplesLX [X] [Y] * w0 + 2 ^ (log2WD ―― 1)) >> log2WD) + o0)
Here, log2WD is a variable indicating a predetermined shift amount.

Further, in the case of the biprediction BiPred, when the weight prediction is performed, the weight prediction unit 3094 derives the weight prediction coefficients w0, w1, o0, and o1 from the coded data, and performs the processing of the following equation.

predSamples [X] [Y] = Clip3 (0, (1 << bitDepth) --1, (predSamplesL0 [X] [Y] * w0 + predSamplesL1 [X] [Y] * w1 + ((o0 + o1 + 1)) << log2WD)) >> (log2WD + 1))
<Motion vector decoding process>
Hereinafter, the motion vector decoding process according to the present embodiment will be specifically described with reference to FIG. 9.

As is clear from the above description, the motion vector decoding process according to the present embodiment is a process of decoding a syntax element related to inter-prediction (also referred to as a motion syntax decoding process) and a process of deriving a motion vector (also referred to as a motion vector decoding process). Motion vector derivation process) and included.

(Motion syntax decoding process)
FIG. 9 is a flowchart showing the flow of the inter-prediction syntax decoding process performed by the inter-prediction parameter decoding control unit 3031. In the following description in the description of FIG. 9, each process is performed by the inter-prediction parameter decoding control unit 3031 unless otherwise specified.

First, in step S101, the merge flag merge_flag is decoded, and in step S102,
merge_flag! = 0 (whether merge_flag is 0)
Is judged.

When merge_flag! = 0 is true (Y in S102), the merge index merge_idx is decoded in S103, and the motion vector derivation process (S111) in the merge mode is executed.

If merge_flag! = 0 is false (N in S102), the inter-prediction identifier inter_pred_idc is decoded in S104.

When inter_pred_idc is other than PRED_L1 (PRED_L0 or PRED_BI), the reference picture index refIdxL0, the difference vector parameter mvdL0, and the prediction vector index mvp_L0_idx are decoded in S105, S106, and S107, respectively.

When inter_pred_idc is other than PRED_L0 (PRED_L1 or PRED_BI), the reference picture index refIdxL1, the difference vector parameter mvdL1, and the prediction vector index mvp_L1_idx are decoded in S108, S109, and S110. Subsequently, the motion vector derivation process (S112) in the AMVP mode is executed.

(Effect of image decoder)
In the image decoding device 31 of the present embodiment, the affine prediction unit 30372 performs either 4-parameter affine or 6-parameter affine processing based on the shape and / or size of the target PU. Therefore, a highly reliable affine parameter can be derived. It is also possible to reduce the amount of coding when the affine parameter is explicitly coded.

(Second embodiment)
Hereinafter, a second embodiment of the present invention will be described. In the first embodiment, the inter-prediction parameter decoding unit 303 determines whether to perform the processing of the 4-parameter affine or the 6-parameter affine based on the shape or size of the target PU. In the present embodiment, the inter-prediction parameter decoding unit 303 is either a 4-parameter affine or a 6-parameter affine based on the shape or size of a block adjacent to the target PU (adjacent block, in the case of a merge, a merge reference block). Decide if you want to do the processing. Since the configuration of the inter-prediction parameter decoding unit 303 is the same as that described in the first embodiment, it will not be described again.

FIG. 28 is a flowchart showing an example of a process of determining whether the inter-prediction parameter decoding unit 303 performs the process of the 4-parameter affine or the 6-parameter affine based on the shape of the adjacent block. In the example shown in FIG. 28, in the inter-prediction parameter decoding unit 303, first, the inter-prediction parameter decoding control unit 3031 determines whether the width (neighWidth) and the height (neighHeight) of the adjacent blocks are equal (SH1). In FIG. 28 and FIG. 29 described later, neighborWidth and neighborHeight are described as width and height, respectively.

When the width and height of the adjacent blocks are equal (Y in SH1), the affine prediction unit 30372 (or AMVP prediction parameter decoding unit 3032) performs the processing of the 6-parameter affine (SH2). When the width of the target PU and the height of the target PU are not equal (N in SH1), the affine prediction unit 30372 (or the AMVP prediction parameter decoding unit 3032) performs the processing of the four-parameter affine (SH3).

(Determined by the shape of the merge reference block)
FIG. 29 is a diagram for explaining an example of selecting the number of control points by the process shown in FIG. 28. In FIG. 29, PU indicates a target PU, and RB indicates an adjacent block.

In the example shown in FIG. 29 (a), the width and height of the adjacent blocks are not equal. Therefore, the affine prediction unit 30372 refers to two motion vectors (for example, v2 and v3) on the adjacent block, derives a motion vector of two control points (for example, V1 and V2) on the target block, and processes the four-parameter affine. To execute.

In the example shown in FIG. 29 (b), the width and height of adjacent blocks are not equal. Therefore, the affine prediction unit 30372 refers to two motion vectors (for example, v1 and v3) on the adjacent block, derives a motion vector of two control points (for example, V1 and V2) on the target block, and processes the four-parameter affine. To execute.

In the example shown in FIG. 29 (c), the width and height of the adjacent blocks are equal to each other. Therefore, the affine prediction unit 30372 refers to the three motion vectors (for example, v1, v2 and v3) on the adjacent block and derives the motion vectors of the three control points (for example, V0, V1 and V2) on the target block, and 6 Process the parameter affine.

In the example shown in FIG. 29 (d), the width and height of the adjacent blocks are equal to each other. Therefore, the affine prediction unit 30372 refers to the three motion vectors (for example, v0, v1 and v2) on the adjacent block and derives the motion vectors of the three control points (for example, V0, V1 and V2) on the target block, and 6 Process the parameter affine.

In the description of FIGS. 29A to 29D, the affine prediction unit 30372 processes the 4-parameter affine or the 6-parameter affine, but the AMVP prediction parameter decoding unit 3032 describes the 4-parameter affine or the 6-parameter affine. Affine processing may be performed.

(Determined by the size of the merge reference block)
FIG. 30 is a flowchart showing an example of a process of determining whether the inter-prediction parameter decoding unit 303 performs the process of the 4-parameter affine or the 6-parameter affine based on the size of the adjacent block. In the example shown in FIG. 30, first, the inter-prediction parameter decoding control unit 3031 determines whether or not the value indicating the size of the adjacent block is equal to or larger than a predetermined threshold value (SI1). When the value indicating the size of the adjacent block is equal to or larger than a predetermined threshold value (Y in SI1), the affine prediction unit 30372 (or the AMVP prediction parameter decoding unit 3032) performs the processing of the 6-parameter affine (SI2). When the value indicating the size of the adjacent block is not equal to or larger than a predetermined threshold value (N in SI1), the affine prediction unit 30372 (or the AMVP prediction parameter decoding unit 3032) performs the processing of the four-parameter affine (SI3).

FIG. 31 is a diagram for explaining an example of selecting the number of control points by the process shown in FIG. 30. In FIG. 31, PU indicates a target PU, and RB indicates an adjacent block. In the following explanation, log2 (neighWidth) + log2 (neighHeight) is used as a value indicating the size of the adjacent block.

(A) and (b) of FIG. 31 show an example in which the size of the adjacent block is smaller than the predetermined threshold value TH, and (c) and (d) of FIG. 31 show an example in which the size of the adjacent block is equal to or larger than the predetermined threshold value TH. Here is an example. In the example of FIG. 31, the size of the target block is 8 × 8 (log2 (puWidth) + log2 (puHeight) = 6), and the sizes of the adjacent blocks of (a), (b), (c), and (d) are respectively. An example is shown in which 4 × 4, 4 × 4, 8 × 8, 4 × 8, TH = 5, but the sizes and thresholds of the target block and the reference block are not limited to this.

In the example shown in FIG. 31 (a), the size of the adjacent block is smaller than the predetermined threshold value TH (log2 (neighWidth) + log2 (neighHeight) <TH). Therefore, the affine prediction unit 30372 refers to two motion vectors (for example, v2 and v3) on the adjacent block, derives a motion vector of two control points (for example, V1 and V2) on the target block, and processes the four-parameter affine. To execute.

In the example shown in FIG. 31 (b), the size of the adjacent block is smaller than the predetermined threshold value TH (log2 (neighWidth) + log2 (neighHeight) <TH). Therefore, the affine prediction unit 30372 refers to two motion vectors (for example, v1 and v3) on the adjacent block, derives a motion vector of two control points (for example, V1 and V2) on the target block, and processes the four-parameter affine. To execute.

In the example shown in FIG. 31 (c), the size of the adjacent block is equal to or larger than a predetermined threshold value TH (log2 (neighWidth) + log2 (neighHeight)> = TH). Therefore, the affine prediction unit 30372 refers to the three motion vectors (for example, v1, v2 and v3) on the adjacent block and derives the motion vectors of the three control points (for example, V0, V1 and V2) on the target block, and 6 Process the parameter affine.

In the example shown in FIG. 31 (d), the size of the adjacent block is equal to or larger than a predetermined threshold value TH (log2 (neighWidth) + log2 (neighHeight)> = TH). Therefore, the affine prediction unit 30372 refers to the three motion vectors (for example, v0, v1 and v3) on the adjacent block and derives the motion vectors of the three control points (for example, V0, V1 and V2) on the target block, and 6 Process the parameter affine.

As the value indicating the size of the target PU, for example, the following can be used.
・ Max (neighWidth, neighHeight)
・ Min (neighWidth, neighHeight)
・ NeighWidth + neighHeight
・ NeighWidth * neighHeight
・ Log2 (neighWidth) + log2 (neighHeight)
However, the value indicating the size of the target PU is not limited to the above example.

Further, the determination in the size of the adjacent block may be as follows.
-Is the size of the target PU larger than the specified threshold?
-Is the size of the target PU less than or equal to the specified threshold?
-Is the size of the target PU smaller than the specified threshold?

(Effect of image decoder)
In the image decoding device 31 of the present embodiment, the affine prediction unit 30372 performs either 4-parameter affine or 6-parameter affine processing based on the shape or size of the adjacent block. A highly reliable affine parameter can also be derived by such an inter-prediction parameter decoding unit 303. It is also possible to reduce the amount of coding when the affine parameter is explicitly coded.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described. In the first embodiment, the inter-prediction parameter decoding unit 303 determines whether to perform the processing of the 4-parameter affine or the 6-parameter affine based on the shape or size of the target PU. The present embodiment relates to the selection of control points in a four-parameter affine. In the present embodiment, the inter-prediction parameter decoding unit 303 may switch the processing of either the 4-parameter affine or the 6-parameter affine, or may always perform the processing of the 4-parameter affine. The inter-prediction parameter decoding unit 303 of the present embodiment determines the position of the control point for deriving the motion vector used for the four-parameter affine based on the shape of the target PU.

FIG. 32 is a flowchart of a process in which the inter-prediction parameter decoding unit 303 determines the position of a control point for deriving a motion vector based on the shape of the target PU. In the example shown in FIG. 32, in the inter-prediction parameter decoding unit 303, first, the inter-prediction parameter decoding control unit 3031 determines whether the target PU is a square (SJ1). When the target PU is square (Y in SJ1), the inter-prediction parameter decoding control unit 3031 uses two diagonal vertices of the target PU as control points (SJ2). When the target PU is not a square (N in SJ1), the inter-prediction parameter decoding control unit 3031 uses two vertices sandwiching the long side of the target PU as control points (SJ3). After that, the affine prediction unit 30372 (or AMVP prediction parameter decoding unit 3032) processes the four-parameter affine at the selected control point (SJ4).

FIG. 33 is a diagram showing an example of the position of the control point determined by the inter-prediction parameter decoding unit 303 of the present embodiment. As shown in FIG. 33 (a), when the shape of the target PU is square, the inter-prediction parameter decoding unit 303 sets four diagonal vertices (for example, control points V1 and V2) of the target PU. Determined as a control point used for parameter affine processing.

When the shape of the target PU is not square as shown in FIGS. 33 (b) and 33 (c), the inter-prediction parameter decoding unit 303 processes the two vertices sandwiching the long side of the target PU into the processing of the four-parameter affine. Determined as the control point to be used. Specifically, for example, in the example shown in FIG. 33 (b), the inter-prediction parameter decoding unit 303 derives the motion vectors of the control points V0 and V2, and uses the motion vectors for the four-parameter affine. Further, for example, in the example shown in FIG. 33 (c), the inter-prediction parameter decoding unit 303 derives the motion vectors of the control points V0 and V1 and uses the motion vectors for the four-parameter affine.

The inter-prediction parameter decoding unit 303 of the present embodiment determines the position of the control point according to the shape of the target PU. Therefore, the accuracy of the motion vector used by the inter-prediction parameter decoding unit 303 for the 4-parameter affine is improved.

In the above example, the inter-prediction parameter decoding unit 303 switches the reference control points in three patterns when the shape of the target PU is a square, a horizontally long rectangle, and a vertically long rectangle, but it is simpler. As a configuration, the control points may be switched in two patterns. For example, the inter-prediction parameter decoding unit 303 determines the control points V0 and V1 as control points when the shape of the target PU is puWidth> = puHeight, and the control points V0 and V2 when the shape is other than that (puWidth <puHeight). Is determined as a control point. Further, the following configuration may be used. The inter-prediction parameter decoding unit 303 determines the control points V0 and V1 as control points when the shape of the target PU is puWidth> puHeight, and controls the control points V0 and V2 when the shape is other than that (puWidth <= puHeight). Determined as a point.

(Fourth Embodiment)
Hereinafter, a fourth embodiment of the present invention will be described. In the second embodiment, the inter-prediction parameter decoding unit 303 determines whether to perform the processing of the 4-parameter affine or the 6-parameter affine based on the shape or size of the adjacent block or the like. The present embodiment relates to the selection of control points in a four-parameter affine. In the present embodiment, the inter-prediction parameter decoding unit 303 may switch the processing of either the 4-parameter affine or the 6-parameter affine, or may always perform the processing of the 4-parameter affine. At this time, the inter-prediction parameter decoding unit 303 changes the control points used for the processing of the four-parameter affine according to the shape of the adjacent block. Specifically, the inter-prediction parameter decoding unit 303 determines the position of the control point in the adjacent block that derives the motion vector used for the 4-parameter affine based on the shape of the adjacent block.

FIG. 34 is a flowchart of the process of determining the position of the point of the adjacent block used by the inter-prediction parameter decoding unit 303 for deriving the motion vector of the control point based on the shape of the adjacent block. In the example shown in FIG. 34, in the inter-prediction parameter decoding unit 303, first, the inter-prediction parameter decoding control unit 3031 determines whether the adjacent block is a square (SK1). When the adjacent block is square (Y in SK1), the inter-prediction parameter decoding control unit 3031 determines two points on the diagonal of the adjacent block to be used for deriving the motion vector of the control point (SK2). When the adjacent block is not a square (N in SK1), the inter-prediction parameter decoding control unit 3031 determines the points used for deriving the motion vector of the control point to two points sandwiching the long side of the adjacent block (SK3). After that, the affine prediction unit 30372 (or AMVP prediction parameter decoding unit 3032) derives the motion vector of the control point using the points of the selected adjacent blocks, and performs the processing of the four-parameter affine (SK4).

FIG. 35 is a diagram showing an example of the position of the control point determined by the inter-prediction parameter decoding unit 303 of the present embodiment. When the shape of the adjacent block is square as shown in FIGS. 35A and 35, the inter-prediction parameter decoding unit 303 is located at two vertices on the diagonal line of the adjacent block (for example, at the upper left of the adjacent block). The motion vector of two control points (for example, V1 and V2) on the target block is derived by referring to the motion vector of the point v0 and the motion vector of the point v3) located at the lower right, and the processing of the four-parameter affine is executed.

When the shape of the adjacent block is rectangular as shown in FIGS. 35 (c) to 35, the inter-prediction parameter decoding unit 303 refers to the motion vector of the two vertices sandwiching the long side of the adjacent block. Then, the motion vectors of the two control points (for example, V1 and V2) on the target block are derived, and the processing of the four-parameter affine is executed. For example, as shown in FIGS. 35 (c) and 35 (d), when the shape of the adjacent block is a rectangle longer in the height direction than the width direction, the inter-prediction parameter decoding unit 303 is in the height direction of the adjacent block. The motion vectors of two points located at both ends of the side (for example, the point v1 located at the upper right of the adjacent block and the point v3 located at the lower right) are used. For example, as shown in FIGS. 35 (e) and 35 (f), when the shape of the adjacent block is a rectangle longer in the width direction than in the height direction, the inter-prediction parameter decoding unit 303 is the side in the width direction of the adjacent block. The motion vector of two points located at both ends of (for example, the point v2 located at the lower left and the point v3 located at the lower right of the adjacent block) is used.

The inter-prediction parameter decoding unit 303 of the present embodiment determines the positions of the vertices in the adjacent block used for deriving the motion vector of the two control points on the target block according to the shape of the adjacent block. Such an inter-prediction parameter decoding unit 303 also improves the accuracy of the motion vector used by the inter-prediction parameter decoding unit 303 for the 4-parameter affine.

(Fifth Embodiment)
Hereinafter, a fifth embodiment of the present invention will be described. In the fourth embodiment, the inter-prediction parameter decoding unit 303 determines the positions of the vertices in the adjacent block used for deriving the motion vector of the two control points on the target block based on the shape of the adjacent block. In the present embodiment, the inter-prediction parameter decoding unit 303 determines the position of the control point in the target PU based on the shape of the adjacent block.

FIG. 36 is a flowchart of a process in which the inter-prediction parameter decoding unit 303 determines the position of a control point for deriving a motion vector based on the shape of an adjacent block. In the example shown in FIG. 36, in the inter-prediction parameter decoding unit 303, first, the inter-prediction parameter decoding control unit 3031 determines whether the adjacent block is a square (SL1). When the adjacent block is a square (Y in SL1), the inter-prediction parameter decoding control unit 3031 uses two diagonal vertices of the target PU as control points (SL2). When the adjacent block is not a square (N in SL1), the inter-prediction parameter decoding control unit 3031 uses two vertices sandwiching the side of the target PU adjacent to the adjacent block as control points (SL3). After that, the affine prediction unit 30372 (or AMVP prediction parameter decoding unit 3032) processes the four-parameter affine at the selected control point (SL4).

FIG. 37 is a diagram showing an example of the position of the control point determined by the inter-prediction parameter decoding unit 303 of the present embodiment. When the shape of the adjacent block is square as shown in FIGS. 37 (a) and 37 (b), the inter-prediction parameter decoding unit 303 displays two vertices (for example, V0 and V3) on the diagonal line of the target PU. 4 Determined as the control point used for the parameter affine.

When the shape of the adjacent block is rectangular as shown in FIGS. 37 (c) to 37 (f), the inter-prediction parameter decoding unit 303 sandwiches two vertices sandwiching the side of the target PU in contact with the adjacent block. 4 Determined as a control point used for the parameter affine. For example, as shown in FIGS. 37 (c) and 37, when the adjacent block is in contact with the left side of the target PU, the inter-prediction parameter decoding unit 303 is in contact with the adjacent block. The two points located at both ends of the target PU (point V1 located at the upper left of the target PU and point V3 located at the lower left) are used as control points. For example, as shown in (d) or (f) of FIG. 37, when the adjacent block is in contact with the upper side of the target PU, the inter-prediction parameter decoding unit 303 is in contact with the adjacent block. Two points located at both ends of the target PU (point V0 located at the upper left of the target PU and point V1 located at the upper right of the target PU) are used as control points.

The inter-prediction parameter decoding unit 303 of the present embodiment determines the position of the control point in the adjacent block according to the shape of the adjacent block. Such an inter-prediction parameter decoding unit 303 also improves the accuracy of the motion vector used by the inter-prediction parameter decoding unit 303 for the 4-parameter affine.

(Configuration of image coding device)
Next, the configuration of the image coding device 11 (moving image coding device) according to the present embodiment will be described. FIG. 4 is a block diagram showing the configuration of the image coding device 11 according to the present embodiment. The image coding device 11 includes a prediction image generation unit 101, a subtraction unit 102, a DCT / quantization unit 103, an entropy coding unit 104, an inverse quantization / inverse DCT unit 105, an addition unit 106, a loop filter 107, and a prediction parameter memory. (Prediction parameter storage unit, frame memory) 108, reference picture memory (reference image storage unit, frame memory) 109, coding parameter determination unit 110, and prediction parameter coding unit 111 are included. The prediction parameter coding unit 111 includes an inter-prediction parameter coding unit 112 (prediction image generation device) and an intra-prediction parameter coding unit 113.

For each picture of the image T, the prediction image generation unit 101 generates a prediction image P of the prediction unit PU for each coding unit CU which is a region in which the pictures are divided. Here, the prediction image generation unit 101 reads out the decoded block from the reference picture memory 109 based on the prediction parameter input from the prediction parameter coding unit 111. The prediction parameter input from the prediction parameter coding unit 111 is, for example, a motion vector in the case of inter-prediction. The prediction image generation unit 101 reads out the block at the position on the reference image indicated by the motion vector starting from the target PU. In the case of intra-prediction, the prediction parameter is, for example, an intra-prediction mode. The pixel value of the adjacent PU used in the intra prediction mode is read from the reference picture memory 109, and the predicted image P of the PU is generated. The prediction image generation unit 101 generates a prediction image P of the PU for the read reference picture block by using one of the plurality of prediction methods. The predicted image generation unit 101 outputs the generated predicted image P of the PU to the subtraction unit 102.

The predicted image generation unit 101 has the same operation as the predicted image generation unit 308 described above. For example, FIG. 6 is a schematic diagram showing the configuration of the inter-prediction image generation unit 1011 included in the prediction image generation unit 101. The inter-prediction image generation unit 1011 includes a motion compensation unit 10111 and a weight prediction unit 10112. Since the motion compensation unit 10111 and the weight prediction unit 10112 have the same configurations as the motion compensation unit 3091 and the weight prediction unit 3094 described above, the description thereof will be omitted here.

The prediction image generation unit 101 uses the parameters input from the prediction parameter coding unit to generate the prediction image P of the PU based on the pixel value of the reference block read from the reference picture memory. The predicted image generated by the predicted image generation unit 101 is output to the subtraction unit 102 and the addition unit 106.

The subtraction unit 102 generates a residual signal by subtracting the signal value of the predicted image P of the PU input from the predicted image generation unit 101 from the pixel value of the corresponding PU of the image T. The subtraction unit 102 outputs the generated residual signal to the DCT / quantization unit 103.

The DCT / quantization unit 103 performs DCT on the residual signal input from the subtraction unit 102, and calculates the DCT coefficient. The DCT / quantization unit 103 quantizes the calculated DCT coefficient to obtain the quantization coefficient. The DCT / quantization unit 103 outputs the obtained quantization coefficient to the entropy coding unit 104 and the inverse quantization / inverse DCT unit 105.

A quantization coefficient is input to the entropy coding unit 104 from the DCT / quantization unit 103, and a coding parameter is input from the prediction parameter coding unit 111. The coded parameters to be input include, for example, a reference picture index refIdxLX, a prediction vector index mvp_LX_idx, a difference vector mvdLX, a prediction mode predMode, and a merge index merge_idx.

The entropy coding unit 104 entropy-codes the input quantization coefficient and coding parameter to generate a coded stream Te, and outputs the generated coded stream Te to the outside.

The dequantization / inverse DCT unit 105 dequantizes the quantization coefficient input from the DCT / quantization unit 103 to obtain the DCT coefficient. The inverse quantization / inverse DCT unit 105 performs an inverse DCT on the obtained DCT coefficient and calculates a residual signal. The inverse quantization / inverse DCT unit 105 outputs the calculated residual signal to the addition unit 106.

The addition unit 106 adds the signal value of the predicted image P of the PU input from the prediction image generation unit 101 and the signal value of the residual signal input from the inverse quantization / inverse DCT unit 105 for each pixel, and decodes the signal. Generate an image. The addition unit 106 stores the generated decoded image in the reference picture memory 109.

The loop filter 107 applies a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the decoded image generated by the addition unit 106.

The prediction parameter memory 108 stores the prediction parameters generated by the coding parameter determination unit 110 at positions predetermined for each of the picture to be coded and the CU.

The reference picture memory 109 stores the decoded image generated by the loop filter 107 at a predetermined position for each of the picture to be encoded and the CU.

The coding parameter determination unit 110 selects one set from the plurality of sets of coding parameters. The coding parameter is a prediction parameter described above or a parameter to be coded generated in connection with the prediction parameter. The prediction image generation unit 101 generates a prediction image P of the PU using each of these sets of coding parameters.

The coding parameter determination unit 110 calculates a cost value indicating the magnitude of the amount of information and the coding error for each of the plurality of sets. The cost value is, for example, the sum of the code amount and the value obtained by multiplying the squared error by the coefficient λ. The code amount is the amount of information of the coded stream Te obtained by entropy-coding the quantization error and the coding parameter. The squared error is the sum of the squared values of the residual values of the residual signal calculated by the subtraction unit 102 between the pixels. The coefficient λ is a real number greater than the preset zero. The coding parameter determination unit 110 selects the set of coding parameters that minimizes the calculated cost value. As a result, the entropy coding unit 104 outputs the selected set of coding parameters to the outside as a coding stream Te, and does not output the set of unselected coding parameters. The coding parameter determination unit 110 stores the determined coding parameter in the prediction parameter memory 108.

The prediction parameter coding unit 111 derives a format for coding from the parameters input from the coding parameter determination unit 110 and outputs the encoding format to the entropy coding unit 104. Derivation of the form for coding is, for example, deriving a difference vector from a motion vector and a prediction vector. Further, the prediction parameter coding unit 111 derives the parameters necessary for generating the prediction image from the parameters input from the coding parameter determination unit 110, and outputs the parameters to the prediction image generation unit 101. The parameters required to generate the predicted image are, for example, motion vectors in sub-block units.

The inter-prediction parameter coding unit 112 derives an inter-prediction parameter such as a difference vector based on the prediction parameter input from the coding parameter determination unit 110. In the inter-prediction parameter coding unit 112, the inter-prediction parameter decoding unit 303 (see FIG. 5, etc.) derives the inter-prediction parameter as a configuration for deriving the parameters necessary for generating the prediction image to be output to the prediction image generation unit 101. Includes a configuration that is partially the same as the configuration to be used. The configuration of the inter-prediction parameter coding unit 112 will be described later.

The intra prediction parameter coding unit 113 derives a format for coding (for example, MPM_idx, rem_intra_luma_pred_mode, etc.) from the intra prediction mode IntraPredMode input from the coding parameter determination unit 110.

(Structure of inter-prediction parameter coding unit)
Next, the configuration of the inter-prediction parameter coding unit 112 will be described. The inter-prediction parameter coding unit 112 is a means corresponding to the inter-prediction parameter decoding unit 303 of FIG. 12, and the configuration is shown in FIG.

The inter-prediction parameter coding unit 112 includes an inter-prediction parameter coding control unit 1121, an AMVP prediction parameter derivation unit 1122 (affin motion vector derivation unit, an affine motion vector derivation device), a subtraction unit 1123, and a subblock prediction parameter derivation unit 1125. And not shown, it is configured to include a split mode derivation section, a merge flag derivation section, an inter-prediction identifier derivation section, a reference picture index derivation section, a vector difference derivation section, etc. The derivation unit, the reference picture index derivation unit, and the vector difference derivation unit derive the PU division mode part_mode, the merge flag merge_flag, the inter-prediction identifier inter_pred_idc, the reference picture index refIdxLX, and the difference vector mvdLX, respectively. The inter-prediction parameter coding unit 112 outputs a motion vector (mvLX, subMvLX), a reference picture index refIdxLX, a PU division mode part_mode, an inter-prediction identifier inter_pred_idc, or information indicating these to the prediction image generation unit 101. Further, the inter-prediction parameter coding unit 112 entropies the PU split mode part_mode, the merge flag merge_flag, the merge index merge_idx, the inter-prediction identifier inter_pred_idc, the reference picture index refIdxLX, the prediction vector index mvp_LX_idx, the difference vector mvdLX, and the subblock prediction mode flag subPbMotionFlag. It is output to the coding unit 104.

The inter-prediction parameter coding control unit 1121 includes a merge index derivation unit 11211 and a vector candidate index derivation unit 11212. The merge index derivation unit 11211 compares the motion vector and the reference picture index input from the coding parameter determination unit 110 with the motion vector and the reference picture index of the merge candidate PU read from the prediction parameter memory 108, and merges them. The index merge_idx is derived and output to the entropy coding unit 104. The merge candidate is a reference PU within a predetermined range from the coding target CU to be encoded (for example, a reference PU in contact with the left lower end, the upper left end, and the upper right end of the coding target block), and is encoded. It is a PU that has been processed. The vector candidate index derivation unit 11212 derives the prediction vector index mvp_LX_idx.

In the subblock prediction parameter derivation unit 1125, when the coding parameter determination unit 110 decides to use the subblock prediction mode, any of spatial subblock prediction, time subblock prediction, affine prediction, and matching prediction is performed according to the value of subPbMotionFlag. Derivation of the motion vector and reference picture index of the subblock prediction. As described in the description of the image decoding device, the motion vector and the reference picture index read the motion vector of the adjacent PU, the reference picture block, and the reference picture index from the prediction parameter memory 108 and derive the motion vector and the reference picture index. Specifically, the sub-block prediction parameter derivation unit 1125 has the same configuration as the above-mentioned sub-block prediction parameter derivation unit 3037 (see FIG. 12).

The AMVP prediction parameter derivation unit 1122 has the same configuration as the AMVP prediction parameter derivation unit 3032 (see FIG. 12) described above.

That is, when the prediction mode predMode indicates the inter-prediction mode, the motion vector mvLX is input from the coding parameter determination unit 110 to the AMVP prediction parameter derivation unit 1122. The AMVP prediction parameter derivation unit 1122 derives the prediction vector mvpLX based on the input motion vector mvLX. The AMVP prediction parameter derivation unit 1122 outputs the derived prediction vector mvpLX to the subtraction unit 1123. The reference picture index refIdx and the prediction vector index mvp_LX_idx are output to the entropy coding unit 104.

The subtraction unit 1123 generates a difference vector mvdLX by subtracting the prediction vector mvpLX input from the AMVP prediction parameter derivation unit 1122 from the motion vector mvLX input from the coding parameter determination unit 110. The difference vector mvdLX is output to the entropy coding unit 104.

In addition, a part of the image coding device 11 and the image decoding device 31 in the above-described embodiment, for example, the entropy decoding unit 301, the prediction parameter decoding unit 302, the loop filter 305, the prediction image generation unit 308, the inverse quantization / inverse DCT. Unit 311, addition unit 312, prediction image generation unit 101, subtraction unit 102, DCT / quantization unit 103, entropy coding unit 104, dequantization / inverse DCT unit 105, loop filter 107, coding parameter determination unit 110, The prediction parameter coding unit 111 may be realized by a computer. In that case, a program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed. The "computer system" referred to here is a computer system built in either the image coding device 11 or the image decoding device 31, and includes hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, and a storage device such as a hard disk built in a computer system. Further, a "computer-readable recording medium" is a medium that dynamically holds a program for a short time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In that case, a program may be held for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. Further, the above-mentioned program may be for realizing a part of the above-mentioned functions, and may be further realized for realizing the above-mentioned functions in combination with a program already recorded in the computer system.

Further, a part or all of the image coding device 11 and the image decoding device 31 in the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the image coding device 11 and the image decoding device 31 may be individually made into a processor, or a part or all of them may be integrated into a processor. Further, the method of making an integrated circuit is not limited to the LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, when an integrated circuit technology that replaces LSI appears due to the progress of semiconductor technology, an integrated circuit based on the technology may be used.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like are made without departing from the gist of the present invention. It is possible to do.

[Application example]
The image coding device 11 and the image decoding device 31 described above can be mounted on and used in various devices for transmitting, receiving, recording, and reproducing moving images. The moving image may be a natural moving image captured by a camera or the like, or an artificial moving image (including CG and GUI) generated by a computer or the like.

First, it will be described with reference to FIG. 38 that the above-mentioned image coding device 11 and image decoding device 31 can be used for transmission and reception of moving images.

FIG. 38A is a block diagram showing a configuration of a transmission device PROD_A equipped with an image coding device 11. As shown in FIG. 38 (a), the transmission device PROD_A modulates the carrier wave with the coding unit PROD_A1 that obtains the coded data by coding the moving image and the coded data obtained by the coding unit PROD_A1. It includes a modulation unit PROD_A2 for obtaining a modulation signal, and a transmission unit PROD_A3 for transmitting the modulation signal obtained by the modulation unit PROD_A2. The image coding device 11 described above is used as the coding unit PROD_A1.

The transmitter PROD_A has a camera PROD_A4 for capturing a moving image, a recording medium PROD_A5 for recording a moving image, an input terminal PROD_A6 for inputting a moving image from the outside, and a moving image as a source of the moving image to be input to the coding unit PROD_A1. , An image processing unit A7 for generating or processing an image may be further provided. In FIG. 38 (a), the configuration in which the transmitting device PROD_A includes all of them is illustrated, but a part thereof may be omitted.

The recording medium PROD_A5 may be a recording of an unencoded moving image, or a moving image encoded by a recording coding method different from the transmission coding method. It may be a thing. In the latter case, a decoding unit (not shown) that decodes the coded data read from the recording medium PROD_A5 according to the coding method for recording may be interposed between the recording medium PROD_A5 and the coding unit PROD_A1.

FIG. 38B is a block diagram showing a configuration of a receiving device PROD_B equipped with an image decoding device 31. As shown in FIG. 38 (b), the receiving device PROD_B has a receiving unit PROD_B1 that receives a modulated signal, a demodulation unit PROD_B2 that obtains coded data by demodulating the modulated signal received by the receiving unit PROD_B1, and demodulation unit PROD_B2. It includes a decoding unit PROD_B3 that obtains a moving image by decoding the coded data obtained by the unit PROD_B2. The image decoding device 31 described above is used as the decoding unit PROD_B3.

The receiving device PROD_B has a display PROD_B4 for displaying the moving image, a recording medium PROD_B5 for recording the moving image, and an output terminal for outputting the moving image to the outside as a supply destination of the moving image output by the decoding unit PROD_B3. It may also have PROD_B6. In FIG. 38 (b), a configuration in which the receiving device PROD_B includes all of them is illustrated, but a part thereof may be omitted.

The recording medium PROD_B5 may be used for recording an unencoded moving image, or may be encoded by a recording coding method different from the transmission coding method. You may. In the latter case, a coding unit (not shown) that encodes the moving image acquired from the decoding unit PROD_B3 according to the recording coding method may be interposed between the decoding unit PROD_B3 and the recording medium PROD_B5.

The transmission medium for transmitting the modulated signal may be wireless or wired. Further, the transmission mode for transmitting the modulated signal may be broadcasting (here, a transmission mode in which the destination is not specified in advance) or communication (here, transmission in which the destination is specified in advance). It may refer to an aspect). That is, the transmission of the modulated signal may be realized by any of wireless broadcasting, wired broadcasting, wireless communication, and wired communication.

For example, a broadcasting station (broadcasting equipment, etc.) / receiving station (television receiver, etc.) of terrestrial digital broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives a modulated signal by radio broadcasting. Further, a broadcasting station (broadcasting equipment, etc.) / receiving station (television receiver, etc.) of cable television broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives a modulated signal by wired broadcasting.

In addition, servers (workstations, etc.) / clients (television receivers, personal computers, smartphones, etc.) such as VOD (Video On Demand) services and video sharing services using the Internet are transmitters that send and receive modulated signals via communication. This is an example of PROD_A / receiver PROD_B (usually, in LAN, either wireless or wired is used as a transmission medium, and in WAN, wired is used as a transmission medium). Here, personal computers include desktop PCs, laptop PCs, and tablet PCs. Smartphones also include multifunctional mobile phone terminals.

The client of the video sharing service has a function of decoding the encoded data downloaded from the server and displaying it on the display, as well as a function of encoding the moving image captured by the camera and uploading it to the server. That is, the client of the video sharing service functions as both the transmitting device PROD_A and the receiving device PROD_B.

Next, it will be described with reference to FIG. 39 that the above-mentioned image coding device 11 and image decoding device 31 can be used for recording and reproducing moving images.

FIG. 39A is a block diagram showing a configuration of a recording device PROD_C equipped with the above-mentioned image coding device 11. As shown in FIG. 39 (a), the recording device PROD_C uses the coding unit PROD_C1 for obtaining coded data by coding the moving image and the coded data obtained by the coding unit PROD_C1 for the recording medium PROD_M. It has a writing unit PROD_C2 for writing. The image coding device 11 described above is used as the coding unit PROD_C1.

The recording medium PROD_M may be of a type built in the recording device PROD_C, such as (1) HDD (Hard Disk Drive) or SSD (Solid State Drive), or (2) SD memory. It may be of a type connected to the recording device PROD_C, such as a card or USB (Universal Serial Bus) flash memory, or (3) DVD (Digital Versatile Disc) or BD (Blu-ray Disc: registration). It may be loaded into a drive device (not shown) built in the recording device PROD_C, such as (trademark).

Further, the recording device PROD_C has a camera PROD_C3 that captures a moving image, an input terminal PROD_C4 for inputting a moving image from the outside, and a reception for receiving the moving image as a source of the moving image to be input to the coding unit PROD_C1. The unit PROD_C5 and the image processing unit PROD_C6 for generating or processing an image may be further provided. In FIG. 39 (a), a configuration in which the recording device PROD_C is provided with all of these is illustrated, but some of them may be omitted.

The receiving unit PROD_C5 may receive an unencoded moving image, or receives coded data encoded by a coding method for transmission different from the coding method for recording. It may be something to do. In the latter case, a transmission decoding unit (not shown) that decodes the coded data encoded by the transmission coding method may be interposed between the receiving unit PROD_C5 and the coding unit PROD_C1.

Examples of such a recording device PROD_C include a DVD recorder, a BD recorder, an HDD (Hard Disk Drive) recorder, and the like (in this case, the input terminal PROD_C4 or the receiving unit PROD_C5 is the main source of moving images). .. In addition, a camcorder (in this case, the camera PROD_C3 is the main source of the moving image), a personal computer (in this case, the receiving unit PROD_C5 or the image processing unit C6 is the main source of the moving image), a smartphone (this). In this case, the camera PROD_C3 or the receiver PROD_C5 is the main source of moving images) is also an example of such a recording device PROD_C.

FIG. 39B is a block diagram showing the configuration of the reproduction device PROD_D equipped with the above-mentioned image decoding device 31. As shown in FIG. 39 (b), the reproduction device PROD_D obtains a moving image by decoding the coded data read by the reading unit PROD_D1 and the reading unit PROD_D1 for reading the coded data written in the recording medium PROD_M. It has a decoding unit PROD_D2 to obtain. The image decoding device 31 described above is used as the decoding unit PROD_D2.

The recording medium PROD_M may be of a type built in the playback device PROD_D, such as (1) HDD or SSD, or (2) SD memory card, USB flash memory, or the like. It may be of a type connected to the playback device PROD_D, or may be loaded into a drive device (not shown) built in the playback device PROD_D, such as (3) DVD or BD. good.

Further, the playback device PROD_D has a display PROD_D3 for displaying a moving image, an output terminal PROD_D4 for outputting the moving image to the outside, and a transmitting unit for transmitting the moving image as a supply destination of the moving image output by the decoding unit PROD_D2. It may also have PROD_D5. In FIG. 39 (b), the configuration in which the reproduction device PROD_D includes all of them is illustrated, but a part thereof may be omitted.

The transmission unit PROD_D5 may transmit an unencoded moving image, or transmits coded data encoded by a transmission coding method different from the recording coding method. It may be something to do. In the latter case, it is preferable to interpose a coding unit (not shown) that encodes the moving image by a coding method for transmission between the decoding unit PROD_D2 and the transmission unit PROD_D5.

Examples of such a playback device PROD_D include a DVD player, a BD player, an HDD player, and the like (in this case, the output terminal PROD_D4 to which a television receiver or the like is connected is the main supply destination of the moving image). .. In addition, a television receiver (in this case, display PROD_D3 is the main supply destination of moving images) and digital signage (also called electronic signage or electronic bulletin board, etc., and display PROD_D3 or transmitter PROD_D5 is the main supply destination of moving images. (First), desktop PC (in this case, output terminal PROD_D4 or transmitter PROD_D5 is the main supply destination of moving images), laptop or tablet PC (in this case, display PROD_D3 or transmitter PROD_D5 is video) An example of such a playback device PROD_D is a smartphone (in this case, the display PROD_D3 or the transmitter PROD_D5 is the main supply destination of the moving image), which is the main supply destination of the image.

(Hardware realization and software realization)
Further, each block of the image decoding device 31 and the image coding device 11 described above may be realized by hardware by a logic circuit formed on an integrated circuit (IC chip), or may be realized by a CPU (Central Processing Unit). It may be realized by software using.

In the latter case, each of the above devices is a CPU that executes an instruction of a program that realizes each function, a ROM (Read Only Memory) that stores the above program, a RAM (RandomAccess Memory) that expands the above program, the above program, and various data. It is equipped with a storage device (recording medium) such as a memory for storing the data. Then, an object of the embodiment of the present invention is a recording in which the program code (execution format program, intermediate code program, source program) of the control program of each of the above-mentioned devices, which is software for realizing the above-mentioned function, is readablely recorded by a computer. It can also be achieved by supplying the medium to each of the above devices and having the computer (or CPU or MPU) read and execute the program code recorded on the recording medium.

Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic discs such as floppy (registered trademark) discs / hard disks, and CD-ROMs (Compact Disc Read-Only Memory) / MO discs (Magneto-Optical discs). ) / MD (Mini Disc) / DVD (Digital Versatile Disc) / CD-R (CD Recordable) / Blu-ray Disc (registered trademark) and other optical discs, IC cards (including memory cards) / Cards such as optical cards, mask ROM / EPROM (Erasable Programmable Read-Only Memory) / EEPROM (Electrically Erasable and Programmable Read-Only Memory: registered trademark) / Semiconductor memories such as flash ROM, or PLD (Programmable logic device) ) And logic circuits such as FPGA (Field Programmable Gate Array) can be used.

Further, each of the above devices may be configured to be connectable to a communication network, and the above program code may be supplied via the communication network. This communication network is not particularly limited as long as it can transmit the program code. For example, Internet, Intranet, Extranet, LAN (Local Area Network), ISDN (Integrated Services Digital Network), VAN (Value-Added Network), CATV (Community Antenna television / Cable Television) communication network, Virtual Private network (Virtual Private) Network), telephone line network, mobile communication network, satellite communication network, etc. can be used. Further, the transmission medium constituting this communication network may be any medium as long as it can transmit the program code, and is not limited to a specific configuration or type. For example, even wired such as IEEE (Institute of Electrical and Electronic Engineers) 1394, USB, power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital Subscriber Line) line, infrared ray such as IrDA (Infrared Data Association) and remote control. , BlueTooth (registered trademark), IEEE802.11 wireless, HDR (High Data Rate), NFC (Near Field Communication), DLNA (Digital Living Network Alliance: registered trademark), mobile phone network, satellite line, terrestrial digital broadcasting network, etc. It can also be used wirelessly. The embodiment of the present invention can also be realized in the form of a computer data signal embedded in a carrier wave, in which the program code is embodied by electronic transmission.

The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. That is, an embodiment obtained by combining technical means appropriately modified within the scope of the claims is also included in the technical scope of the present invention.

(Mutual reference of related applications)
This application claims the benefit of priority to the Japanese patent application filed on September 27, 2016: Japanese Patent Application No. 2016-188791, and by referring to the application, all the contents thereof. Is included in this book.

The embodiment of the present invention can be suitably applied to an image decoding device that decodes coded data in which image data is encoded, and an image coding device that generates coded data in which image data is encoded. can. Further, it can be suitably applied to the data structure of the coded data generated by the image coding device and referenced by the image decoding device.

11 Image coding device 31 Image decoding device 112 Inter-prediction parameter coding unit (prediction image generation device)
303 Inter-prediction parameter decoding unit (prediction image generator)
1122, 3032 AMVP prediction parameter derivation unit (affine motion vector derivation unit, affine motion vector derivation device)
30372 Affine prediction unit (affine motion vector derivation unit, affine motion vector derivation device)
309 Inter-prediction image generation unit (prediction image generation unit)

Claims (10)

In the affine motion vector derivation device that derives the motion vector of each subblock constituting the target PU,
The affine motion vector derivation device is
The motion vector of each of the plurality of subblocks included in the target block is calculated by referring to the motion vector at the control point set in the reference block sharing the vertex with the target block.
Depending on at least one of the shape and size of the target block, the motion vectors of the two control points are calculated and the four-parameter affine is processed, or the motion vectors of the three control points are calculated and the six-parameter affine is calculated. An affine motion vector derivation device characterized by switching whether or not to perform the processing of. In a predictive image generator for generating a predictive image used for coding or decoding a moving image,
Affine motion vector derivation part and
Equipped with a predictive image generator
The affine motion vector derivation unit is
The motion vector of each of the plurality of subblocks included in the target block is calculated by referring to the motion vector at the control point set in the reference block sharing the vertex with the target block.
Depending on at least one of the shape and size of the target block, the motion vectors of the two control points are calculated and the four-parameter affine is processed, or the motion vectors of the three control points are calculated and the six-parameter affine is calculated. Switch whether to perform the processing of
The predicted image generation unit
A predictive image generation device, characterized in that a predictive image is generated by referring to a motion vector of the control point. The affine motion vector derivation unit is
The predictive image generation device according to claim 2, wherein when the target block is square, processing of 6-parameter affine is performed, and when the target block is not square, processing of 4-parameter affine is performed. The affine motion vector derivation unit is
When the merge flag merge_flag indicates that the merge process is not performed, and the target block is not a square, the 4-parameter affine process is performed.
If the merge flag merge_flag indicates that the merge process is not performed, and the target block is square, the PU affine mode flag pu_affine_mode_flag is decoded, and the PU affine mode flag pu_affine_mode_flag processes the 6 parameter affine. When the PU affine mode flag pu_affine_mode_flag indicates that the 4-parameter affine is processed, the 4-parameter affine is processed. The predicted image generation device according to claim 2 or 3. The affine motion vector derivation unit is
2. Predictive image generator according to. The affine motion vector derivation unit is
When the merge flag merge_flag indicates that the merge process is not performed, and the size of the target block is not equal to or larger than a predetermined threshold value, the 4-parameter affine process is performed.
When the merge flag merge_flag indicates that the merge process is not performed and the size of the target block is equal to or larger than a predetermined threshold, the PU affine mode flag pu_affine_mode_flag is decoded and the PU affine mode flag pu_affine_mode_flag is set. When it indicates that 6-parameter affine processing is performed, 6-parameter affine processing is performed, and when the PU affine mode flag pu_affine_mode_flag indicates that 4-parameter affine processing is performed, 4-parameter affine processing is performed. The predicted image generation device according to claim 5, wherein the above-mentioned is performed. The affine motion vector derivation unit is
The predicted image generation device according to claim 2, wherein the processing of the 6-parameter affine is performed when the size of the target block is equal to or larger than a predetermined threshold value and the target block is square. The affine motion vector derivation unit is
When the merge flag merge_flag indicates that the merge process is not performed, and the size of the target block is not equal to or larger than a predetermined threshold value and the target block is not a square, a 4-parameter affine process is performed. ,
(1) The merge flag merge_flag indicates that the merge process is not performed, and the size of the target block is equal to or larger than a predetermined threshold, or (2) the merge flag merge_flag does not perform the merge process. When the size of the target block is not equal to or larger than a predetermined threshold and the target block is square, the PU affine mode flag pu_affine_mode_flag is decoded, and the PU affine mode flag pu_affine_mode_flag is 6. If it indicates that the parameter affine processing is performed, the 6-parameter affine processing is performed, and if the PU affine mode flag pu_affine_mode_flag indicates that the 4-parameter affine processing is performed, the 4-parameter affine processing is performed. The predictive image generation device according to claim 7, wherein the prediction image generation device is performed. The predictive image generator according to any one of claims 2 to 8 is provided.
A moving image decoding device, characterized in that a decoded image is generated by adding or subtracting a residual signal from the predicted image. The predictive image generator according to any one of claims 2 to 8 is provided.
A moving image coding device for coding a residual signal between a predicted image and a coded target image.

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