JP2002232887A - Image encoding method and image encoder, and image decoding method and image decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To an image encoder/decoder that divides an image into block encoding mode information and data with respect to pixel values in a block to encode the image and improves an encoding efficiency of the mode information so as to reduce the entire encoding quantity of one frame. SOLUTION: A mode information encoding means 2 predicts encoding object block mode information by mode information of blocks around an encoding object block and having already been encoded and uses an encoding word table corresponding to a prediction hit rate for encoding an image so as to generate a code word with respect to the mode information, and a block data encoding means 3 encodes pixel data in the block according to an encoding method depending on the mode information of the block and generates an encoded signal of the digital image. Thus the encoding efficiency of the mode information can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding / decoding method and an image encoding / decoding apparatus for encoding and decoding a digital image, and a recording medium on which a program for realizing the image encoding / decoding apparatus is recorded. It is about.

[0002]

2. Description of the Related Art Conventionally, as an image coding method requiring reversibility, MMR (M
odified Modified Read) is famous. However, MM
R performs processing on the entire input frame.
One of the problems is compatibility with an encoding method that divides one frame employed in TU-T H.261 or ISO / IEC MPEG into a plurality of blocks and performs processing in block units. So this
MMMR (Modified MMR), which is a further improvement of MMR, has been adopted as an evaluation model for MPEG4 (ISO / IECJTC / SC29 / WG11
N1277, July 1996).

[0003] In such a system in which a digital image divided into two-dimensional blocks consisting of a plurality of pixels is encoded for each block, the presence or absence of block motion compensation, the presence or absence of orthogonal transform coefficients for each block, and the input image If the image is a shape image that indicates the shape of the object or the composition ratio, it indicates the significance of the block, etc., and is divided into coding mode information indicating the coding method of the pixel value data in the block and data on the pixel value in the block. Is encoded.

[0004]

According to the above-described method of coding by dividing the coding mode information of the block into data relating to the pixel values in the block, the motion information, the orthogonal transform coefficient, the significant When the number of blocks that do not have a complicated shape or the like increases, the ratio of the mode information of the blocks in the generated coded signal relatively increases, and the coding efficiency deteriorates.

[0005] It is an object of the present invention to improve the coding efficiency of mode information and reduce the code amount of one entire frame in such an image coding and decoding apparatus.

[0006]

According to the first aspect of the present invention, when a digital image divided into two-dimensional blocks consisting of a plurality of pixels is encoded for each block, encoding of each block is performed. Determining a method, outputting mode information, encoding data in a block according to the mode information, and predicting and encoding the mode information from mode information of surrounding already encoded blocks. And an image encoding method.

With the above configuration, when coding mode information, the coding mode of the block to be coded is predicted from the mode information of the peripheral block that has already been coded.
By switching a codeword table in which codewords are determined according to the prediction hit rate, it is possible to achieve an improvement in coding efficiency of mode information.

According to a second aspect of the present invention, when a digital image divided into two-dimensional blocks consisting of a plurality of pixels is encoded for each block, an encoding method for each block is determined and mode information is output. An image code comprising: a step of collectively encoding the mode information for all blocks in one frame; and a step of sequentially encoding data of each block in accordance with the mode information. Method.

According to the above-described configuration, by encoding mode information for encoding of each block of a digital image divided into a plurality of blocks for one frame, encoding using the correlation between the blocks of the mode information can be performed. It can be easily performed, and improvement in coding efficiency can be achieved.

According to a third aspect of the present invention, a digital image is decoded by reproducing an image for each two-dimensional block composed of a plurality of pixels with an encoded signal as an input and rearranging the pixel values in the block. At this time, the process of predicting and decoding the mode information of the current block to be decoded from the mode information of the peripheral block that has already been decoded, and the process of decoding data in the block according to the decoded mode information An image decoding method comprising:

With the above configuration, when decoding the mode information, the coding mode of the block to be decoded is predicted from the mode information of the peripheral blocks that have already been decoded, and the mode is predicted in accordance with the hit rate of the prediction. The mode information can be correctly decoded by switching the codeword table that defines the codeword.

According to a fourth aspect of the present invention, when a coded signal is input, an image is reproduced for each two-dimensional block composed of a plurality of pixels, and a digital image is reproduced by rearranging pixel values in the block. A step of decoding mode information of all blocks in one frame and outputting the mode information; and a step of sequentially decoding data of each block in accordance with the decoded mode information. Image decoding method.

[0013] With the above-described configuration, by collectively decoding code words related to mode information for one frame, decoding using correlation between blocks of mode information can be easily performed, and mode information can be correctly decoded.

According to a fifth aspect of the present invention, when a digital image divided into two-dimensional blocks consisting of a plurality of pixels is encoded for each block, an encoding mode determining means for determining an encoding method of each block. Block data encoding means for encoding data in a block in accordance with the mode information determined by the encoding mode determining means; and Is an image coding apparatus including mode information coding means for predicting and coding from mode information of a block.

According to the above configuration, when coding mode information, the coding mode of the block to be coded is predicted from the mode information of the peripheral block that has already been coded.
By switching a codeword table in which codewords are determined according to the prediction hit rate, it is possible to achieve an improvement in coding efficiency of mode information.

According to a sixth aspect of the present invention, when a digital image divided into two-dimensional blocks consisting of a plurality of pixels is encoded for each block, an encoding mode determining means for determining an encoding method for each block. Mode information coding means for collectively coding the mode information determined by the coding mode determining means for all blocks in one frame, and a block for sequentially coding data of each block according to the mode information This is an image encoding device including data encoding means.

According to the above configuration, the encoding mode information of each block of the digital image divided into a plurality of blocks is collectively encoded for one frame, so that the encoding using the correlation between the blocks of the mode information can be performed. It can be easily performed, and improvement in coding efficiency can be achieved.

According to a seventh aspect of the present invention, a digital image is reproduced by reproducing an image for each two-dimensional block composed of a plurality of pixels by using an encoded signal as an input and rearranging the pixel values in the block. A mode information decoding means for predicting and decoding mode information of a current block to be decoded from mode information of peripheral blocks which have already been decoded; and mode information in the block according to the mode information reproduced by the mode information decoding means. An image decoding apparatus includes a block data decoding unit that decodes data.

With the above arrangement, when decoding the mode information, the coding mode of the block to be decoded is predicted from the mode information of the peripheral block that has already been decoded, and the mode is predicted in accordance with the hit rate of the prediction. The mode information can be correctly decoded by switching the codeword table that defines the codeword.

According to an eighth aspect of the present invention, a digital image is reproduced by reproducing an image for each two-dimensional block composed of a plurality of pixels by using an encoded signal as an input and rearranging pixel values in the block. Image, comprising: mode information decoding means for decoding mode information of all blocks in one frame and outputting mode information; and data decoding means for sequentially decoding data of each block based on the mode information. It is a decoding device.

With the above configuration, by collectively decoding code words relating to mode information for one frame, decoding using correlation between blocks of mode information can be easily performed, and mode information can be correctly decoded.

According to a ninth aspect of the present invention, there is provided an apparatus for encoding a digital image divided into a two-dimensional block composed of a plurality of pixels by a programmed computer for each block. Coding mode determining means for determining, block data coding means for coding data in a block according to the mode information determined by the coding mode determining means, and mode information determined by the coding mode determining means Is a mode information encoding means for predicting and encoding from the mode information of already encoded blocks in the vicinity.

With the above arrangement, when a digital image divided into a two-dimensional block composed of a plurality of pixels by a programmed computer is encoded for each block, encoding is performed when mode information is encoded. The coding mode of the block to be coded is predicted from the mode information of the neighboring blocks that have been set, and the codeword table in which the codewords are determined according to the prediction accuracy is improved, thereby improving the coding efficiency of the mode information. Can be achieved.

According to a tenth aspect of the present invention, an image is reproduced for each two-dimensional block composed of a plurality of pixels by using a coded signal as an input by a programmed computer, and the pixel values in the block are rearranged to perform digital reproduction. An apparatus for reproducing an image, comprising: mode information decoding means for predicting and decoding mode information of a current block to be decoded based on mode information of peripheral blocks which have already been decoded; and mode information decoded by the mode information decoding means. An image decoding apparatus includes a block data decoding unit that decodes data in a block according to mode information.

With the above arrangement, an encoded signal is input by a programmed computer to reproduce an image for each two-dimensional block composed of a plurality of pixels, and a digital image is reproduced by rearranging the pixel values in the block. At this time, by encoding the mode information of the encoding of each block of the digital image divided into a plurality of blocks for one frame, encoding using the correlation between the blocks of the mode information can be easily performed, Improvement in coding efficiency can be achieved.

According to an eleventh aspect of the present invention, there is provided a method for encoding a digital image divided into two-dimensional blocks each consisting of a plurality of pixels by a programmed computer for each block. Determining, outputting the mode information, encoding the data in the block according to the mode information, and predicting and encoding the mode information from the mode information of the already-encoded blocks in the vicinity. An image coding method characterized by comprising:

With the above configuration, when a digital image divided into a two-dimensional block composed of a plurality of pixels by a programmed computer is encoded for each block, encoding is already performed when mode information is encoded. The coding mode of the block to be coded is predicted from the mode information of the neighboring blocks that have been set, and the codeword table in which the codewords are determined according to the prediction accuracy is improved, thereby improving the coding efficiency of the mode information. Can be achieved.

According to a twelfth aspect of the present invention, an image is reproduced for each two-dimensional block composed of a plurality of pixels by using a coded signal as an input by a programmed computer, and the pixel values in the block are rearranged to perform digital reproduction. A method of reproducing an image, wherein a step of predicting and decoding mode information of a current block to be decoded from mode information of peripheral blocks that have already been decoded, and a step of decoding data in the block according to the decoded mode information. And a decoding step.

With the above arrangement, an encoded signal is input by a programmed computer to reproduce an image for each two-dimensional block composed of a plurality of pixels, and a digital image is reproduced by rearranging the pixel values in the block. When decoding the mode information, the coding mode of the block to be decoded is predicted from the mode information of the neighboring blocks that have already been decoded, and the codeword is determined according to the prediction accuracy. By switching the code word table, the mode information can be correctly decoded.

According to a thirteenth aspect of the present invention, there is provided a recording medium storing an image encoding program for encoding a digital image divided into a two-dimensional block composed of a plurality of pixels by a computer for each block. The encoding program determines the encoding method of each block to the computer, outputs mode information, encodes data in the block according to the mode information, and encodes the mode information of the surrounding already encoded blocks. This is a recording medium that records an image encoding program characterized by performing prediction and encoding from mode information.

According to the above configuration, the recording medium is a computer recording medium. By transferring this recording medium, another independent computer encodes a digital image divided into two-dimensional blocks consisting of a plurality of pixels for each block. , An image encoding program to be executed, and highly efficient encoding can be performed.

According to a fourteenth aspect of the present invention, a digital image is decoded by reproducing an image for each two-dimensional block composed of a plurality of pixels by using a coded signal as an input and rearranging the pixel values in the block. A recording medium storing an image decoding program to be decoded, wherein the image decoding program predicts and decodes mode information of a decoding target block from mode information of peripheral blocks which have already been decoded by a computer; A recording medium on which an image decoding program characterized by decoding data in a block according to the obtained mode information.

With the above structure, the present invention is a recording medium of a computer. By transferring this recording medium, another independent computer reproduces an image for each two-dimensional block composed of a plurality of pixels by using an encoded signal as an input. Executing an image decoding program that decodes the digital image by reordering the pixel values in the block,
Accurate playback is possible.

According to a fifteenth aspect of the present invention, there is provided an image encoding / decoding device comprising the image encoding device according to the fifth or ninth aspect and the image decoding device according to the seventh or tenth aspect.

According to the above configuration, the configuration of the image encoding / decoding device can be realized by combining the image encoding device and the image decoding device.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a block diagram of an image coding apparatus according to Embodiment 1 of the present invention. In the figure, reference numeral 1 denotes coding mode determining means for determining a coding mode of a block, and 2 denotes mode information for generating a codeword relating to coding mode information from coding mode information of a block determined by the coding mode determining means 1. Encoding means 3 is a block data encoding means for encoding a pixel value in the block according to the encoding mode information of the block determined by the encoding mode determination means 1 to generate a code word, and 4 is a mode information encoding means 2 Is a multiplexing unit that multiplexes a codeword related to the encoding mode information output by the unit and a codeword related to the pixel value data output by the block data coding unit 3 to generate a coded image signal. Reference numeral 11 denotes a pixel value signal of a block of a digital input image divided by a block dividing unit (not shown), 12 denotes coding mode information of the block, 13 denotes a code word relating to coding mode information,
Reference numeral 4 denotes a code word relating to block data, and reference numeral 15 denotes an encoded image signal of a digital input image divided into blocks.

The operation of the image coding apparatus according to the first embodiment configured as described above will be described below.

First, the digital input image is, as shown in FIG. 2, an ordinary color signal in which one frame is composed of M horizontal pixels and N vertical lines, and shape information representing the shape of an object or the composition ratio. The input pixel value signal 11 is divided into a plurality of blocks each having m horizontal pixels and n vertical lines by a block dividing means not shown in the figure. The input pixel value signal 11 of the divided block is input to the coding mode determining means 1 and the block data coding means 3.

In the encoding mode determining means 1, the position (i, j)
The coding mode of the block is determined from the pixel value data of the block (hereinafter, referred to as POS (i, j)). In the case of a normal color signal, the presence / absence of motion compensation and the presence / absence of an orthogonal transform coefficient are determined. In the case of a shape signal, the presence / absence of a significant shape is determined. (POS (i, j)
Hereinafter, the coding mode of the block is described as MODE (i, j). The encoding mode determination unit 1 outputs the determined MODE (i, j) to the mode information encoding unit 2 and the block data encoding unit 3, respectively.

Referring to FIG. 3, the encoding mode determining means 1 will be described in detail. FIG. 3B shows a digital input image divided into 4 × 4 blocks for convenience of explanation.
In each block of the digital input image shown in FIG. 3 (b), the encoding mode determination means 1 sets A when the pixels in the block are all “0” as shown in FIG. Is assigned to a coding mode when B includes "0" and "1", and to C when all the pixels in the block are "1". As a result of adding three types of encoding modes to the digital input image of FIG.
(C).

Next, the mode information coding means 2 converts the coding mode given to each block by the coding mode determining means 1 into a code corresponding to MODE (i, j) from the code word table shown in FIG. Select a word and output it as a codeword for the encoding mode.

If the coding mode of the block to be coded is MODE (i, j), the mode information coding means 2 sets the surrounding coding mode MODE (i-1, j) shown in FIG.
MODE (i, j) can be predicted from j), MODE (i-1, j-1), and MODE (i, j-1). That is, A,
MODE (i-1, j), MOD
If E (i-1, j-1) and MODE (i, j-1) are all A, MODE (i, j)
A code word with a small amount of information (for example, “0”:
1 bit) and adaptively switch the codeword table using a codeword table as shown in FIG. 4 to improve the coding efficiency in the coding mode.

Specifically, when the coding mode of the peripheral block is biased toward A, the code word of coding mode A is 0.
(Codeword length = 1 bit), codeword of coding mode B is 1
0 (codeword length = 2 bits), and the codeword of coding mode C is set to 11 (codeword length = 2 bits). Similarly, when the coding mode of the peripheral block includes a large amount of B, and when the coding mode of the peripheral block includes a large amount of C, the code word length of the dominant coding mode is similarly reduced. . In this case, a code word set is selected from peripheral code words from among three types of code word sets.
However, as shown in FIG. 3C, the surrounding blocks are assumed to be, for example, “A” in the coding mode of the surrounding blocks.
The encoding mode of each peripheral block is encoded.

Next, regarding the mode information encoding means 2,
FIG. 6 shows a detailed block diagram for explanation.

The mode information encoding means 2 encodes the encoding mode sent from the encoding mode determining unit 1 so that the information on the encoding mode of the peripheral block of the encoding target block can be easily obtained. Mode storage unit 101
Save to The coding mode of a block is stored in a position corresponding to the block position of the block in one frame.

When the block position POS (i, j) of the block to be coded is input, the coding mode reading section 102 receives the block position POS (i-1,
j-1), POS (i, j-1), POS (i-1, j) coding mode MODE (i-1,
j), MODE (i-1, j-1), and MODE (i, j-1) are read from the encoding mode storage unit 101 and provided to the codeword table selecting unit 104.

The codeword table selecting unit 104 generates encoding modes MODE (i-1, j), MODE (i-1, j-1), MODE (i, j-
A code word table set in association with a combination that matches the combination of 1) is selected from the code word table table 103.
For example, if the coding mode of the peripheral block is (A, A,
A), (A, A, B), (A, A, C), (B, A,
A), (C, A, A), (A, B, A), (A, C,
In the case of A), a codeword table of (A = 0, B = 10, C = 11) is selected. The above example is a case where the encoding mode A of the peripheral block is dominant. When the encoding mode B of the peripheral block is dominant, (A = 10, B = 0, C =
When the codeword table of 11) is selected and the encoding mode C of the peripheral block is dominant, (A = 10, B = 11, C =
0) is selected. The codeword table selected according to the mode state of the peripheral block is provided to encoding section 105.

As described above, in the first embodiment, the codeword table used for encoding the mode information is adaptively switched according to the state of the encoding mode of the peripheral block.

The encoding unit 105 encodes the encoding mode of the encoding target block based on the selected codeword table. Now, if the encoding mode input from the encoding mode determining means 1 is A and the codeword table input from the codeword table selecting unit 104 is (A = 0, B = 10, C = 11), the codeword = 0 is output. FIG. 3D shows the result of encoding the encoding mode shown in FIG.

Therefore, when the dominant mode is included in the peripheral block of the block to be coded and the mode of the block to be coded matches the dominant mode, a codeword having a short codeword length is generated.

On the other hand, if A or C is input as the encoding mode for the POS (i, j) block from the encoding mode determining means 1, the block data encoding means 3 determines the pixel value encoding of the encoding target block. Stop the conversion. This is because in the case of the encoding modes A and C, since all the pixels in the block are black or white, the block can be decoded only in the encoding mode. In the case of the encoding mode C, the pixel value of the encoding target block is encoded, and a codeword related to the block data is output.

Finally, the multiplexing means 4 multiplexes the codeword relating to the encoding mode and the codeword relating to the block data and outputs a coded image signal. FIG. 7 shows an example of a bit stream at the time of multiplexing. When all the pixels in the block are “0” or “1”, only the code word 701 in the encoding mode is set, and “0” is assigned to the pixel in the block. "When"
Only when 1 "is present, the code word 701 of the coding mode and the code word 702 of the block data are output.

As described above, according to the present embodiment, a plurality of codeword tables for converting individual encoding modes into codewords are prepared in association with the encoding mode states of the peripheral blocks, and are included in many peripheral blocks. A code word having a short code word length is assigned to the dominant mode, and the code word table is adaptively switched according to the state of the coding mode of the peripheral block.

Instead of passing the contents of the codeword table selected by the codeword table selection unit 104 to the encoding unit 105, only the number of the selected codeword table is notified to the encoding unit 105.
The encoding unit 105 may fetch the contents of the codeword table specified by the number from the codeword table table 103.

(Embodiment 2) FIG. 8 is a block diagram of an image decoding apparatus according to Embodiment 2 of the present invention. In the figure, the same means and signals as those in the first embodiment shown in FIG.

In the figure, reference numeral 21 denotes a demultiplexing means for separating and outputting a codeword relating to a coding mode and a codeword relating to block data from a coded image signal, and 22 designates a coding mode outputted by the demultiplexing means 21. The mode information decoding means 23 for reproducing the coding mode of the block from the code word. The mode information decoding means 23 converts the code word relating to the block data output from the Block data decoding means 31 for reproducing pixel values in the block indicates a digital pixel value signal in the reproduced block.

The operation of the image decoding apparatus according to the second embodiment configured as described above will be described below.

First, the demultiplexing means 21 receives the coded image signal, separates the coded image signal into a code word 13 relating to the encoding mode and a code word 14 relating to the block data, and outputs them.

The mode information decoding means 22 receives the code word 13 relating to the coding mode, and reproduces and outputs the coding mode information 12 of the corresponding block from the code word table.

Assuming that the object to be decoded by the mode information decoding means 22 is a block of POS (i, j), the MO shown in FIG.
DE (i-1, j), MODE (i-1, j-1), MODE (i, j-1) have already been played, and MODE (i, j) is MODE (i-1, j) , MODE (i-1, j-
1) By switching the codeword table table based on FIG. 4 from the state of the encoding mode of MODE (i, j-1), decoding is performed from the codeword related to the encoding mode encoded according to the first embodiment. The coding mode of the target block can be correctly reproduced.

Next, FIG. 9 shows a detailed block diagram of the mode information decoding means 22, which will be described.

When the decoding unit 110 decodes the code word in the coding mode, the decoded coding mode is written into the corresponding pixel block position in the coding mode storage unit 111.

The position information of the block to be decoded within one frame is input to the encoding mode reading unit 112.
The encoding mode reading unit 112 stores the encoding mode of the decoded block around the current block based on the position information of the current block.
, And input to the codeword table selection unit 114.

The codeword table selection unit 114 extracts the same codeword table as the codeword table at the time of encoding from the codeword table prediction table 113 based on the state of the encoding mode of the peripheral block of the block to be decoded. The code word table extracted from the code word table table 113 is passed to the decoding unit 110.

Decoding section 110 has code word table selecting section 114
Is decoded using the codeword table passed from.

The decoded coding mode is stored in the coding mode storage section 111 and is input to the block data decoding means 23.

The block data decoding means 23 receives the code word 14 relating to the block data and performs a decoding process corresponding to the coding mode indicated in the coding mode information 12 to thereby obtain the digital pixel value signal 31 in the block. Play and output.

In the first and second embodiments, the coding modes of the three neighboring blocks are used for predicting the coding mode of the current block. However, it is not possible to further increase the number of reference blocks. It is possible.

Further, in the above embodiment, the case where the coding mode is of three types (A, B, C) is described, but the same processing can be performed even if the number of states is further increased.

Further, in the above-described embodiment, the coding word table shown in FIG. 4 is used for coding the coding mode information, but the coding mode information of the coding target block is predicted by using the arithmetic coding method. It is possible to switch the probability model used for arithmetic coding depending on the value.

By combining the image encoding device of the first embodiment with the image decoding device of the second embodiment,
It is possible to realize an encoding / decoding device. (Embodiment 3) FIG. 10 is a block diagram of an image coding apparatus according to Embodiment 3 of the present invention. In the figure,
The same means and signals as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals and description thereof will be omitted.

In FIG. 10, reference numeral 41 denotes a memory for holding the coding mode information for each block output from the coding mode determining means 1 and outputting the data for one frame collectively; 42, a memory for one frame output from the memory 41; A mode information encoding unit 43 collectively encodes the encoding mode information to generate a code word. The mode information encoding unit 43 holds the code word relating to the block data for each block created by the block data encoding unit 3 and collectively outputs one frame. A multiplexing means 44 multiplexes a code word for one frame of mode information output from the memory 43 and a code word for one frame of block data output from the memory 43 to generate an encoded image signal. In addition, 51 is encoding mode information for 12 frames, 52 is a codeword for mode information for one frame, 53 is a codeword for block data for one frame, and 54 is an encoded image signal of a digital input image. It is.

The operation of the image coding apparatus according to the third embodiment configured as described above will be described below.

First, as in the first embodiment, the digital input image signal 11 is
The coding mode MODE (i, j) of the block of S (i, j) is determined. The determined MODE (i, j) is held by the memory 41 and all the encoding modes MODE (1,1), MODE for one frame are stored.
(1,2),... MODE (2,1),... MODE (X, Y) are input to the mode information encoding means 42.

Next, the mode information encoding means 42
The mode information for the frame is encoded and a codeword 52 is output. As for the pixel data in the block, the code words relating to the block data encoded by the block data encoding unit 3 are held by the memory 43 in the same manner as in the first embodiment, and are combined into a code word 53 relating to all the block data for one frame. . The encoding operation of the mode information encoding means 42 will be specifically described.

The mode information encoding means 42 has a code word table (Table 1) for encoding the encoding modes of a plurality of blocks at a time. In this code word table, unique code words are assigned to all combinations of two of the three types of coding modes (A, B, C).
In particular, the combinations (A, A), (B,
For B) and (C, C), the codeword length is set to be relatively shorter than other combinations.

[0078]

[Table 1] Now, as an encoding mode for one frame, FIG.
It is assumed that the encoding mode for one frame having the contents shown in (1) has been transferred to the mode information encoding unit 42.

The encoding mode is cut out two blocks at a time from the head of the line. In the case shown in FIG. 11A, two coding modes that are continuous in the horizontal direction are set as one unit in the order of (A, B), (B, B), (A, A), and are to be coded. Becomes

FIG. 1 shows the result of encoding the encoding mode for one frame shown in FIG. 11 (a) using the code word table shown in (Table 1).
This is shown in FIG. It can be seen that a region where the same mode continues is a code word having a short code word length.

On the other hand, the pixel data of the pixel block is encoded by the block data encoding means 3 in the same manner as in the first embodiment, and the code words relating to the block data are stored in the memory 4.
3 and are collected into a code word 53 for all block data for one frame.

The multiplexing means 44 multiplexes the code word 52 relating to the encoding mode and the code word 53 relating to all the block data for one frame, and
4 is output.

As described above, in the third embodiment, after encoding modes of pixel blocks for one frame are stored in the memory, a plurality of encoding modes are encoded at a time. In a codeword table for encoding a plurality of encoding modes at once, a codeword having a short codeword length is assigned to a combination of the same encoding modes.

(Embodiment 4) FIG. 12 is a block diagram of an image decoding apparatus according to Embodiment 4 of the present invention. In the figure, the same signals as those in the second embodiment shown in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 61 denotes a demultiplexing means for separating a code word string relating to the encoding mode and a code word string relating to the block data from the encoded signal, and 62 denotes a coding mode outputted by the demultiplexing means 61. Mode information decoding means for obtaining mode information from the code word string; 63, a memory for holding mode information of all blocks for one frame output by the mode information decoding means 62;
Is a block data decoding means for reproducing a pixel value from a codeword string relating to the corresponding block data outputted by the demultiplexing means 61 in accordance with the coding mode of the block outputted by. Reference numeral 31 denotes a reproduced digital image signal.

The operation of the image decoding apparatus according to the fourth embodiment configured as described above will be described below.

First, the demultiplexing means 61 outputs the encoded signal 5
4 is separated and output as a code word string relating to the encoding mode of all the blocks for one frame and a code word string relating to the block data of each block.

Next, in mode information decoding means 62, the code word table (Table 1)
Is used to decode the coding modes of all the blocks in one frame from the code word string 52 for the coding mode for one frame. The memory 63 holds the encoding modes of all the blocks in one frame, and performs POS according to the request from the block data decoding unit 23.
Output the encoding mode MODE (i, j) of the block at the position (i, j).

Finally, the block data decoding means 23 outputs the POS (i, j) separated and output by the demultiplexing means 61.
Codeword string 14 relating to block data of the block at the position
And the coding mode MO of the block output from the memory 63
Upon receiving DE (i, j), the pixel value in the block is reproduced and output according to MODE (i, j).

Further, a digital image signal is reproduced by rearranging the output pixel values for each block in a scanning order by a suitable rearranging means not shown in the figure.

In the above-described embodiment, the coding modes of all the blocks in one frame decoded by the mode information decoding means 62 are stored in the memory 63, and the coding mode of the block data decoding means 23 is Therefore, the coding mode MODE (i,
By obtaining j), the encoded image signal encoded by the image encoding device described in Embodiment 3 can be correctly reproduced.

In the third and fourth embodiments, the coding modes of two consecutive pixel blocks are collectively coded. However, the coding modes of more pixel blocks are coded together. It is also possible. In addition, although a plurality of pixel blocks that are continuous in the horizontal direction are targeted for encoding, a plurality of pixel blocks that are consecutive in the vertical direction and pixel blocks that are continuous in the two-dimensional direction may be collectively targeted for encoding. it can. in this case,
A code word table corresponding to a combination of blocks to be collectively encoded is required.

In the above-described embodiment, the codeword table shown in Table 1 showing the encoding of mode information is used. However, other encoding methods such as an arithmetic encoding method can be used. Note that the decoding device according to the fourth embodiment is combined with the encoding device according to the third embodiment to perform encoding / coding.
A decoding device can be realized.

(Embodiment 5) The present invention relates to Embodiment 1,
By realizing the configuration shown in 2, 3 and 4 as software by a program, recording this on a recording medium such as a floppy (R) disk and transferring it, it can be easily implemented by another independent computer system. Can be.

FIG. 14 is a block diagram of a computer system, which will be described below. 120 is a TV signal, V
A moving image input device for reproducing and inputting a moving image from a TR, a DVD or the like, 121 is a memory, 122 is a CPU (Central Processing Unit) that performs image encoding or image decoding by a program, and 123 is an instruction to the CPU 122. Give keyboard and display and FD (Floppy (R)
Input / output device including a storage medium storing a program such as a disk), an IC card, and a CD-ROM; 124, a display for displaying the result of processing by the CPU 122; 125, an external storage for storing the result of processing by the CPU 122; Device.

First, prior to the processing, an image encoding program or an image decoding program is previously installed in the CPU 122 via an apparatus for reading a recording medium such as an FD or a CD-ROM according to an instruction from the input / output device 123. It is assumed that the image encoding program or the image decoding program is activated by the input / output device 123.

In the computer system configured as described above, an image coding apparatus for coding a digital image divided into a two-dimensional block composed of a plurality of pixels by a programmed computer for each block will be described with reference to FIG. A description will be given along the processing flow.

In step 200, an image signal is sent from the moving image input device 120 to the CPU 1 according to an instruction from the input / output device 123.
The data is recorded in the memory 121 through the memory 22. The image signal is
One frame unit or a plurality of frame units may be used.

In step 201, the image signal of one frame in the memory 121 is divided into a plurality of blocks,
Extract the pixel value of (i, j).

In step 202, coding modes A (all "0" in the block), B ("0" and "1" in the block), and C (all "1" in the block) are determined from the pixel values in the block. ). Step 203 converts the block data from the memory 121 into a codeword only when the encoding mode is “B”. Step 204 converts the coding mode of the target block into a codeword according to the codeword table from the neighboring coding modes.

In step 205, the code word of the coding mode and the code word of the block data are multiplexed. Step 20
6 moves to the next block position. Step 208
Determines whether the process is completed, and if NO, repeats steps 201 to 206. YES
In the case of, the process proceeds to step 208, where the encoded image signal formed by the multiplexing is recorded in the external storage device 125.
It should be noted that there is no problem even if video is recorded in the external storage device 125 in block units.

Next, a coded image signal is input by a programmed computer to form a 2
An image decoding apparatus that reproduces a digital image by reproducing an image for each dimensional block and reordering the pixel values in the block will be described with reference to the processing flow of FIG.

Step 220 is a process in which the moving image input device 120
From the memory 12 via the CPU 122
Enter 1

In step 221, the multiplexed coded image signal is read out in block units, and the target block P (i,
For j), the code word of the coding mode and the code word of the block data are separated. In step 222, the encoding mode of the target block is reproduced based on the encoding mode of the neighboring decoded blocks and the encoding table. Step 223 decodes the block data according to the reproduced encoding mode. A step 224 stores the block data of the target block in the memory 121.

Step 225 moves to the next block position. Step 226 is for judging whether or not the processing is completed. In the case of NO, the processing from step 221 to step 226 is repeated. In the case of YES, the process proceeds to step 227, where the decoded digital image signal is recorded on the external storage device 125 or output to the display 124.

FIG. 13 shows a floppy (R) disk as an example of the recording medium.

In this embodiment, a floppy (R) disk is shown as a recording medium. However, the present invention can be similarly implemented as long as a program such as an IC card, a CD-ROM, or a magnetic tape can be recorded. it can.

The present invention is not limited to the above embodiments, but can be variously modified without departing from the gist of the present invention, and they are included in the scope of the present invention.

[0109]

As described above, the effects of the present invention include:
In an image encoding apparatus and an image decoding apparatus, which divide a digital image into blocks and divide and encode the blocks into block coding modes and block data for each block, the coding efficiency of codewords related to the coding modes is improved. And a remarkable effect that encoding can be performed with a smaller number of bits can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image encoding device according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing block division of a digital input image according to the first embodiment.

FIG. 3 is a view for explaining an encoding mode determining unit according to the first embodiment;

FIG. 4 is a diagram showing a codeword table of the image encoding apparatus according to the first embodiment.

FIG. 5 is a conceptual diagram showing a target block and peripheral blocks according to the first embodiment.

FIG. 6 is a detailed block diagram of a mode information encoding unit of the image encoding device according to the first embodiment.

FIG. 7 is a diagram for explaining a bit stream of the image encoding device according to the first embodiment.

FIG. 8 is a block diagram of an image decoding apparatus according to Embodiment 2 of the present invention.

FIG. 9 is a detailed block diagram of a mode information decoding unit of the image decoding apparatus according to the second embodiment.

FIG. 10 is a block diagram of an image encoding device according to a third embodiment of the present invention.

FIG. 11 is an example of combining adjacent blocks in encoding in the encoding mode according to the third embodiment.

FIG. 12 is a block diagram of an image decoding apparatus according to Embodiment 4 of the present invention.

FIG. 13 is a plan view of a floppy (R) disk as an example of a recording medium according to Embodiment 5 of the present invention.

FIG. 14 is a block diagram of a computer system according to the fifth embodiment.

FIG. 15 is an operation flowchart of an image encoding device using a computer according to the fifth embodiment.

FIG. 16 is an operation flowchart of an image decoding apparatus using a computer according to the fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Encoding mode determination means 2, 42 Mode information encoding means 3 Block data encoding means 4, 44 Multiplexing means 21, 61 Demultiplexing means 22, 62 Mode information decoding means 23 Block data decoding means 41, 43 , 63 memory 101 coding mode storage unit 102 coding mode reading unit 103 code word table table 104 code word table selection unit 105 coding unit 110 decoding unit 111 coding mode storage unit 112 coding mode reading unit 113 code word table Table 114 Codeword table selection unit 120 Video input device 121 Memory 122 CPU 123 Input / output device 124 Display 125 External storage device 701 Codeword in encoding mode 702 Codeword of block data

Claims (16)

[Claims] When encoding a digital image divided into two-dimensional blocks consisting of a plurality of pixels for each block, a method for determining an encoding method for each block and outputting mode information; An image encoding method, comprising: encoding data in a block according to information; and predicting and encoding the mode information from mode information of a neighboring encoded block. 2. A process for determining a coding method for each block and outputting mode information when coding a digital image divided into a two-dimensional block consisting of a plurality of pixels for each block; An image encoding method comprising: a step of collectively encoding information for all blocks in one frame; and a step of sequentially encoding data of each block according to the mode information. 3. When a digital image is decoded by reproducing an image for each two-dimensional block composed of a plurality of pixels by using an encoded signal as an input and reordering pixel values in the block, decoding is already performed. A step of predicting and decoding the mode information of the current block to be decoded from the mode information of the already-peripheral blocks, and a step of decoding data in the block according to the decoded mode information. Image decoding method. 4. An image is reproduced for each two-dimensional block composed of a plurality of pixels by using an encoded signal as an input, and when a digital image is reproduced by rearranging the pixel values in the block, one frame in one frame is reproduced. An image decoding method, comprising: a step of decoding mode information of all blocks and outputting mode information; and a step of sequentially decoding data of each block according to the decoded mode information. 5. An encoding mode determining means for determining an encoding method of each block when encoding a digital image divided into a two-dimensional block consisting of a plurality of pixels for each block; A block data encoding unit that encodes data in the block according to the mode information determined by the determination unit; and a mode information determined by the encoding mode determination unit, based on the mode information of the surrounding already-encoded blocks. An image coding apparatus comprising a mode information coding unit for performing prediction and coding. 6. A coding mode determining means for determining a coding method for each block when a digital image divided into two-dimensional blocks consisting of a plurality of pixels is coded on a block-by-block basis. Mode information encoding means for collectively encoding the mode information determined by the determination means for all blocks in one frame, and block data encoding means for sequentially encoding data of each block according to the mode information. Image encoding device. 7. When an encoded signal is input, an image is reproduced for each two-dimensional block composed of a plurality of pixels, and when a digital image is reproduced by rearranging pixel values in the block, decoding has already been performed. Mode information decoding means for predicting and decoding the mode information of the decoding target block from the mode information of the peripheral blocks of, and a block for decoding data in the block according to the mode information reproduced by the mode information decoding means An image decoding device comprising data decoding means. 8. When an encoded signal is input, an image is reproduced for each two-dimensional block composed of a plurality of pixels, and when a digital image is reproduced by rearranging pixel values in the block, a digital image within one frame is reproduced. An image decoding apparatus comprising: mode information decoding means for decoding mode information of all blocks and outputting mode information; and data decoding means for sequentially decoding data of each block based on the mode information. 9. An apparatus for encoding, on a block-by-block basis, a digital image divided into a two-dimensional block consisting of a plurality of pixels by a programmed computer, wherein an encoding mode is determined for each block. Means, block data encoding means for encoding data in a block in accordance with the mode information determined by the encoding mode determining means, and mode information determined by the encoding mode determining means in the surrounding area. An image coding apparatus, comprising: mode information coding means for predicting and coding from mode information of a block already completed. 10. An apparatus which reproduces an image for each two-dimensional block composed of a plurality of pixels using a coded signal as an input by a programmed computer, and reproduces a digital image by rearranging pixel values in the block. A mode information decoding means for predicting and decoding mode information of a current block to be decoded from mode information of peripheral blocks which have already been decoded; and a mode in the block according to mode information reproduced by the mode information decoding means. An image decoding device comprising a block data decoding means for decoding the data of (1). 11. A method for encoding a digital image divided into two-dimensional blocks each consisting of a plurality of pixels by a programmed computer for each block, comprising:
Determining the encoding method of each block, outputting the mode information, encoding the data in the block according to the mode information, and extracting the mode information from the mode information of the peripheral already encoded blocks. A step of predicting and encoding. 12. A method in which a coded signal is input by a programmed computer to reproduce an image for each two-dimensional block composed of a plurality of pixels, and a digital image is reproduced by rearranging pixel values in the block. A process of predicting and decoding mode information of a current block to be decoded from mode information of peripheral blocks that have already been decoded, and a process of decoding data in the block in accordance with the decoded mode information. An image decoding method, comprising: 13. A recording medium for recording an image encoding program for encoding a digital image divided into a two-dimensional block consisting of a plurality of pixels by a computer for each block, wherein the image encoding program is stored in a computer. Determine the encoding method of each block, output mode information, encode the data in the block according to the mode information, predict the mode information from the mode information of the surrounding already encoded blocks A recording medium on which an image encoding program characterized by being converted is recorded. 14. An image decoding program for reproducing an image for each two-dimensional block composed of a plurality of pixels by using a coded signal as an input by a computer, and decoding a digital image by rearranging pixel values in the block. The image decoding program predicts and decodes mode information of a decoding target block from mode information of peripheral blocks that have already been decoded by a computer, and decodes the image according to the decoded mode information. A recording medium on which an image decoding program for decoding data in a block is recorded. 15. An image coding / decoding device comprising the image coding device according to claim 5 and the image decoding device according to claim 7. 16. An image encoding / decoding device comprising the image encoding device according to claim 6 and the image decoding device according to claim 8.