JP2010136037A - Video code amount control method, video-encoding device, video code amount control program, and recording medium for the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance subjective picture quality, while making variation in the picture quality quiet as a whole by utilizing surplus code amount of sound in video encoding. <P>SOLUTION: In a video-encoding device, a surplus code amount calculation part 131, when determining a target code amount of a GOP to be encoded, calculates the sound surplus code amount allowed to be utilized for the encoding of the GOP from a sound generation code amount. A condition determining section 132 determines the utilization condition of a predetermined surplus code amount; and when the calculated surplus code amount agrees with the condition, a GOP target code amount calculating part 133 adds all or a part of the sound surplus code amount to an original GOP target code amount. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides video code amount control for controlling the video code amount in accordance with the generated code amount of audio so that the sum of the bit rate of the audio stream and the bit rate of the video stream falls within a predetermined bit rate range. The present invention relates to a method, a video encoding device, a video code amount control program, and a recording medium thereof.

  In general, in a transmission system in which a video stream and other streams such as audio and data are multiplexed and transmitted, the video is subjected to bit rate control independently of other streams (Non-Patent Documents 1 and 2). reference).

  In general, in video / audio coding, the amount of code increases for an input signal that is complex and changes a lot, and the amount of code decreases for an input signal that is monotonous and changes little.

Since the lossy coded stream is transmitted at a constant bit rate (CBR), the generated code amount is controlled to fall within a predetermined range by changing the degree of signal degradation. On the other hand, in a lossless encoded stream, since the change in the amount of generated code cannot be controlled, it is generally transmitted at a variable bit rate (VBR).
ISO / IEC 13818-2 Annex C, ITU-T Recomendation H.264 Annex C The Institute of Image Information and Television Engineers, “Multi-media selection MPEG”, The Institute of Image Information and Television Engineers, published by Ohm Corporation, 1996.4.20

  When a lossless audio encoded stream such as MPEG-4 ALS and a video encoded stream (hereinafter, the encoded stream is also simply referred to as “stream”) are multiplexed, the fluctuation of the audio transmission bit rate is changed to the video transmission bit rate. It is often too large to ignore.

  Therefore, in the multiplexed stream of video and audio, out of the fixed bit rate of audio, if the surplus code amount with small generated code amount of audio encoded data can be used for video encoding, The rate is not wasted, and it is thought that it contributes to the improvement of image quality.

  However, considering that the fluctuation of the generated code amount of the audio encoded data is effectively used for video encoding in this way, the image quality of the entire video is improved, but the generated code of the audio encoded data is improved. Image quality is greatly degraded in scenes with a large amount of data, and image quality may be too clear in scenes with a small amount of generated code of speech encoded data. Therefore, image quality fluctuations become conspicuous according to changes in speech encoded data. A new problem arises.

  FIG. 9 is a diagram illustrating the problem of the present invention. Conventionally, when an audio encoded stream and a video encoded stream with a fixed encoding bit rate are multiplexed, as shown in FIG. 9A, the video is bit-rate controlled independently of the audio stream. It was. Note that GOP (Group Of Pictures) is a unit of video encoded data generally composed of a group of pictures of dozens to tens of frames, where GOP (n) represents the nth GOP.

  In the case of a lossless audio encoded stream, the generated code amount of audio fluctuates, and the data amount of audio encoded data may be considerably smaller than the data amount that can be transmitted at a given audio bit rate. The amount of code for this bit rate margin is referred to as surplus code amount here. The portion indicated by hatching in FIG. 9B is the surplus code amount.

  FIG. 9C shows the relationship between the audio bit rate and the video bit rate when it is considered to use the audio surplus code amount shown in FIG. 9B for transmission of video encoded data. . By using the surplus audio code amount for transmission of video encoded data, the target code amount in GOP units during video encoding can be made larger than the target code amount based on the original video bit rate.

  As shown in FIG. 9C, if the extra audio code amount is used for transmission of video encoded data, the generated code amount of video can be increased, so that the image quality of the video is improved. However, the video bit rate fluctuates according to the fluctuation of the audio bit rate, and a new problem that the fluctuation of the image quality may be noticeable occurs.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to effectively use the excess code amount of audio for video coding, improve the image quality, and make the fluctuation of the image quality inconspicuous as a whole.

  In order to solve the above-described problem, the present invention provides the following when multiplexing a lossy audio encoded stream, a data stream, etc., which cannot control the encoding bit rate, and a lossy video encoded stream into CBR as follows: The code amount of the video is controlled according to the generated code amount of the audio.

  (1) The excess audio code amount is used for video encoding only when the parameters such as the difference between the target code amount and the generated code amount at the time of video encoding, the quantization step size, and the activity meet the predetermined conditions. To do.

  (2) The amount of surplus audio that can be used for video encoding is obtained from the amount of surplus code of the encoded audio data already encoded at that time and the transmission timing. In addition, the use determination of the surplus code amount and the timing for determining the use amount are set at the head of the GOP or in units of frames.

  (3) At the start of video GOP encoding, if the audio for the GOP period is encoded in advance, the excess code amount of the audio for the same GOP period, otherwise the immediately preceding GOP period is obtained. When the use of the surplus code amount is determined, the surplus code amount is set as the upper limit. The amount of code required for image quality improvement is calculated from the quantization step size and activity.

  Based on the above points, the present invention controls the video code amount as follows. First, a surplus audio code amount in a period of a video encoding control unit (for example, GOP or frame) is calculated from the encoded audio generation code amount. A video feature or a coding condition that affects a predetermined video generated code amount is determined as to whether or not the surplus code amount is added to the target code amount in the video coding control unit. If the condition is satisfied, part or all of the surplus code amount is added to the target code amount in the video coding control unit. If the condition is not satisfied, the surplus code amount is added to the target code amount in the video coding control unit. In addition, the target code amount in the video encoding control unit to be encoded next is determined. According to the determined target code amount, the video signal in the video encoding control unit is encoded.

For example, it is preferable to use one of the following conditions as the condition.
A condition that the average quantization parameter of a predetermined number of past video frames is equal to or greater than a predetermined threshold;
A condition that the average quantization step of a predetermined number of video frames in the past is equal to or greater than a predetermined threshold;
-The condition that the average activity value of the video encoding control unit to be encoded is equal to or greater than a predetermined threshold,
-The condition that there is a scene change in the video encoding control unit to be encoded from now on,
A condition that the sum of the differences between the target code amount and the generated code amount of a predetermined number of past video frames is equal to or greater than a predetermined threshold.

The following method can be used as a method for calculating the excess code amount of audio used for video encoding.
The sum of the difference between the predetermined maximum generated code amount of each audio encoding control unit and the actual generated code amount in the audio encoding control unit group in the same display period as the video encoding control unit To calculate from
In the audio encoding control unit group having the same display period as the video frame group having the same length as that of the video encoding control unit preceding the video encoding control unit by a predetermined number of video frames, A method of calculating from a sum of differences between a predetermined maximum generated code amount and an actual generated code amount in each speech encoding control unit.

  In the present invention, when video encoded data and encoded data other than video encoded data are multiplexed and transmitted, codes other than video encoded data are transmitted in the same manner as the excess code amount of audio encoded data described above. It is also possible to determine the additional target code amount based on the surplus code amount of the encoded data and control the code amount of video encoding.

  According to the present invention, when video is encoded so that an encoded stream obtained by multiplexing video and audio is within a predetermined bit rate range, the image quality is improved in a scene where video encoding is difficult. As a whole, subjective image quality can be improved by making image quality fluctuations less noticeable.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of an apparatus according to an embodiment of the present invention. The video encoding device 10 receives a video signal from the video / audio superimposed signal, encodes the video signal, and outputs a video stream. The audio encoding device 20 inputs an audio signal among the video / audio superimposed signals and outputs an audio stream. The multiplexing unit 30 multiplexes and outputs the audio stream and the video stream so as to have a predetermined bit rate.

  In this embodiment, the audio encoding device 20 can be configured in the same manner as the prior art except that it has a function of transmitting the audio generation code amount to the video encoding device 10 for each frame or sequentially. Description is omitted.

  The video encoding device 10 includes a video input unit 11 that inputs a video signal, a video input buffer 12 that stores the input video signal, a video GOP target encoding amount determination unit 13 that determines a target code amount of a video for each GOP, Video frame target code amount determination unit 14 that determines a target code amount for each video frame, video frame encoding processing unit 15 that encodes a video signal according to the frame target code amount, video stream output unit 16 that outputs a video stream, and video A video stream output buffer 17 for temporarily storing the stream is provided.

  The video GOP target code amount determination unit 13 performs a surplus code amount calculation unit 131 that calculates a surplus code amount that can be used for video encoding from the audio generation code amount for each GOP, and video encodes the calculated surplus code amount. And a GOP target code amount calculation unit 133 that calculates a GOP target code amount according to the determination result of the condition.

  The activity / scene change analysis unit 18 calculates activity values or detects the presence / absence of a scene change in the video data to be analyzed prior to encoding in the input video signal. , 4 are used. In other embodiments, it can be omitted.

[Example 1]
FIG. 2 is a flowchart of the video encoding process according to the first embodiment of the present invention. In the first embodiment, when the average quantization parameter QP _ave (n) of several past video frames is equal to or greater than a certain threshold TH _qp , the surplus audio code amount is used for video coding. This is because when the average quantization parameter QP _ave (n) exceeds a certain value due to a lack of code amount that can be used for video coding, the degree of coarsening of the image increases, the need for improving the image quality increases, This is because the change in image quality due to the addition of the excess code amount is less noticeable.

  The nth GOP (Group Of Pictures) is GOP (n). Video and audio are encoded in parallel. However, in this embodiment, it is assumed that encoding of an audio frame having the same display period as that of a GOP (n) video frame is completed before the start of GOP (n) video frame encoding.

First, the video GOP target code amount determination unit 13 executes the following steps S101 to S105. The information on the amount of generated speech code is received from the speech encoding device 20, and the surplus amount of code G _r (n) in the GOP (n) period for the speech frames j to j + M−1 in the same display period as the video frame of GOP (n). Is obtained by the following equation (step S101).

G _r (n) = Σx _{= j} ^{j + M−1} {S _amax −S _a (x)}
Here, M is the number of speech frames in the GOP (n) period, S _amax is the maximum generated code amount of each speech frame, and S _a (x) is the generated code amount of the xth speech frame. A predetermined value may be used as _Samax .

Next, it is determined whether the average quantization parameter QP _ave (n) of the past several video frames is equal to or greater than a certain threshold TH _qp (step S102). The number of video frames to be averaged may be any number and is determined in advance. If the average quantization parameter QP _ave (n) is greater than or equal to a certain threshold TH _qp , the average quantization parameter QP _ave (n) exceeds the threshold TH _qp within a range not exceeding the surplus code amount G _r (n). The additional GOP target code amount G _d (n) is determined in proportion to (step S103). In this case, G _d (n) is obtained by the following equation.

G _d (n) = min (G _r (n), a · (QP _ave (n) −TH _qp ))
min () is a function that returns a minimum value, and a is a predetermined constant.

On the other hand, if the average quantization parameter QP _ave (n) is not equal to or greater than a certain threshold TH _qp , the additional GOP target code amount G _d (n) is set to 0 (step S104).

Next, the GOP target code amount G (n) is calculated as follows: NOP frame number N × reference video bit rate R / video frame rate P, additional GOP target code amount G _d (n), and carry-over code from the previous GOP The sum is obtained (step S105). The GOP target code amount G (n) is as follows.

Carryover code amount from G (n) = N · R / P + G d (n) + previous GOP Incidentally, the reference image bit rate R, the video bit rate can be ensured when always maximum amount of codes generated in the speech frame Point to.

  Next, the video frame target code amount determination unit 14 and the video frame encoding processing unit 15 repeat the processing of steps S106 to S109 described below until the encoding of the frame in GOP (n) is completed (step S106). S110).

The video frame target code amount determination unit 14 allocates the target code amount of GOP (n) to each frame in the GOP and obtains the target code amount T (i) of the next frame (step S106). As a method for calculating the target code amount T (i) of the next frame from the target code amount of GOP (n), for example, there is a method disclosed in the following reference 1, and this is a well-known technique. The detailed description in is omitted.
[Reference 1] International Organization for Standardization, Test Model Editing Committee, 1993, Test Model 5, April, ISO-IEC / JTC1 / SC29 / WG11 / N0400
Next, the video frame target code amount determination unit 14 determines the limit that the decoder reception buffer will not fail based on the buffer occupancy calculated from the buffer size of the decoder reception buffer and the transferred data amount in the transmission destination video decoding device. Is clipped so that the target code amount does not exceed the value (step S107). If the buffer size of the decoder reception buffer is sufficiently large, or if the delay time until decoding may be increased, the clipping process can be omitted.

  The video frame encoding processing unit 15 encodes the frame i according to the target code amount calculated by the video frame target code amount determining unit 14 (step S108). If interlace is specified, encoding is performed in units of fields. However, in order to simplify the description, the case of encoding in units of fields will be described simply as frame encoding.

  When the frame encoding is completed, the video frame target code amount determination unit 14 subtracts the generated code amount S (i) from the target code amount of GOP (n) (step S109). Thereafter, it is determined whether or not encoding has been completed for all frames in GOP (n). If not, the process returns to step S106, and the same processing is repeated until encoding is completed for all frames (step S110). ).

  The video GOP target code amount determination unit 13 determines the carry-over code amount to the next GOP from the difference between the GOP target code amount G (n) at the start of GOP and the GOP generated code amount (step S111). Thereafter, the process returns to step S101, and the encoding process is similarly performed for the next GOP.

[Example 2]
FIG. 3 is a flowchart of the video encoding process according to the second embodiment of the present invention. In the second embodiment, when the average quantization step Q _ave (n) of several past video frames is greater than or equal to a certain threshold value TH _q , the excess code amount of speech is used for video coding. This becomes a shortage of code amount available for video encoding more than a certain value average quantization step Q _ave (n), the extent of a rough picture quality is increased, along with the need for improved image quality increases, the voice This is because the change in image quality due to the addition of the excess code amount is less noticeable.

The difference between the first embodiment and the second embodiment described above is that the condition for determining whether or not to use the audio surplus code amount for video coding is determined by the average quantization parameter QP _ave (n) or the average quantization. This is whether it is performed in step Q _ave (n). Although the conversion formula between the quantization parameter and the quantization step varies depending on the encoding standard, it can be approximated by “(code amount) = a / (quantization step) + b” (a and b are constants) in general. The calculation accuracy of the additional target code amount is better in the second embodiment.

  In the second embodiment, steps S102 to S104 in the flowchart shown in FIG. 2 are replaced with steps S202 to S204 in FIG. 3 and the other portions are the same. Therefore, only the steps S202 to S204 will be described below. explain.

After executing step S101 shown in FIG. 2, the condition determination unit 132 of the video GOP target code amount determination unit 13 determines whether the average quantization step Q _ave (n) of the past several video frames is greater than a certain threshold TH _q . Is determined (step S202). When the average quantization parameter Q _ave (n) is greater than or equal to the threshold value TH _{q, the} GOP target code amount calculation unit 133 does not exceed the excess code amount G _r (n), and the average quantization parameter Q _ave (n ) according to the threshold TH _q excess of, determining an additional GOP target code amount G _d (n) (step S203). In this case, G _d (n) is obtained by the following equation.

G _d (n) = min (G _r (n), a · (1 / TH _q −1 / Q _ave (n))
min () is a function that returns a minimum value, and a is a predetermined constant.

On the other hand, if the average quantization parameter Q _ave (n) is not equal to or greater than the threshold TH _q , the additional GOP target code amount G _d (n) is set to 0 (step S204).

  The subsequent processing is the same as steps S105 to S111 in FIG.

Example 3
FIG. 4 is a flowchart of the video encoding process according to the third embodiment of the present invention. In the third embodiment, when the activity average value act (n) of the GOP to be encoded is equal to or greater than a certain threshold TH _act , the excess audio code amount is used for video encoding. This is because if the activity average value act (n) is large, the amount of generated code increases, the image quality becomes coarse, the need for improving the image quality increases, and the change in image quality due to the addition of the extra code amount of audio becomes less noticeable. is there.

  In the third embodiment, an activity / scene change analysis unit 18 is provided in the video encoding apparatus 10 shown in FIG. 1, and the activity / scene change analysis unit 18 precedes the video encoding by 1 GOP and performs video activity analysis. The activity average value act (n) is calculated in advance. Here, the activity indicates the characteristics of the pixel value distribution in the encoding target area, and is a value representing the degree of variation of the pixel value. For example, an activity is defined by a minimum variance value of small blocks obtained by further dividing a macroblock. The variance value of the small block is a sum of absolute values of differences between the average value of the luminance values in the small block and the luminance value of each pixel in the small block.

  In the third embodiment, steps S102 to S104 in the flowchart shown in FIG. 2 are replaced with steps S302 to S304 in FIG. 4 and the other portions are the same, so only the steps S302 to S304 will be described below. explain.

After executing step S101 shown in FIG. 2, the condition determination unit 132 of the video GOP target code amount determination unit 13 determines whether the activity average value act (n) of the GOP to be encoded is equal to or greater than a certain threshold TH _act. (Step S302). When the activity average value act (n) is equal to or greater than the threshold TH _act , the GOP target code amount calculation unit 133 does not exceed the surplus code amount G _r (n), and the threshold TH of the activity average value act (n). _The additional GOP target code amount G _d (n) is determined in proportion to the excess of _act (step S303). In this case, G _d (n) is obtained by the following equation.

G _d (n) = min (G _r (n), a · (act (n) −TH _act ))
min () is a function that returns a minimum value, and a is a predetermined constant.

On the other hand, if the activity average value act (n) is not equal to or greater than the threshold TH _act , the additional GOP target code amount G _d (n) is set to 0 (step S304).

  The subsequent processing is the same as steps S105 to S111 in FIG.

Example 4
FIG. 5 is a flowchart of the video encoding process according to the fourth embodiment of the present invention. In the fourth embodiment, when there is a scene change in the GOP to be encoded, the surplus amount of audio is used for video encoding. This is because if a GOP to be encoded has a scene change, motion compensation is not performed in the frame immediately after the scene change, and a larger amount of code is required than usual in order to maintain the same image quality.

In the fourth embodiment, an activity / scene change analysis unit 18 is provided in the video encoding device 10 shown in FIG. 1, and the activity / scene change analysis unit 18 performs video activity analysis by 1 GOP before video encoding. In addition, scene change analysis is performed to determine in advance the presence / absence of a scene change and the activity act _sc of the scene change frame when there is a scene change.

Various methods for detecting a scene change have been conventionally known, such as the method described in Reference Document 2 below, and will not be described in detail here.
[Reference 2] Otsuki, Tonomura, “Examination of automatic video cut detection method”, The Institute of Image Information and Television Engineers, ITJ Technical Report, Vol.16, No.43 (19920710), pp.7 -12
In the fourth embodiment, steps S102 to S104 in the flowchart shown in FIG. 2 are replaced with steps S402 to S404 in FIG. 5 and the other portions are the same, so only the steps S402 to S404 will be described below. explain.

After executing step S101 shown in FIG. 2, the condition determination unit 132 of the video GOP target code amount determination unit 13 determines from the analysis result by the activity / scene change analysis unit 18 whether there is a scene change in the GOP to be encoded. Is determined (step S402). When there is a scene change, the GOP target code amount calculation unit 133 adds the additional GOP target code amount G _d in proportion to the activity act _sc of the scene change frame within a range not exceeding the surplus code amount G _r (n). (N) is determined (step S403). In this case, G _d (n) is obtained by the following equation.

G _d (n) = min (G _r (n), a · act _sc + b))
min () is a function that returns the minimum value, and a and b are predetermined constants.

On the other hand, if there is no scene change in the GOP to be encoded, the additional GOP target code amount G _d (n) is set to 0 (step S404).

  The subsequent processing is the same as steps S105 to S111 in FIG.

Example 5
FIG. 6 is a flowchart of the video encoding process according to the fifth embodiment of the present invention. In the fifth embodiment, when the sum ΔB of the difference between the target code amount and the generated code amount of several past video frames is equal to or greater than a certain threshold TH _B , the surplus audio code amount is used for video encoding. To do. This is because it is considered that the code amount is insufficient when the difference between the target code amount and the generated code amount continues.

  In the fifth embodiment, steps S102 to S104 in the flowchart shown in FIG. 2 are replaced with steps S502 to S504 in FIG. 6 and the other portions are the same, so only the steps S502 to S504 will be described below. explain.

After executing step S101 shown in FIG. 2, the condition determination unit 132 of the video GOP target code amount determination unit 13 has the sum ΔB of the difference between the target code amount of the past several video frames and the actual generated code amount. It is determined whether or not the threshold value TH _{B is} exceeded (step S502). When the total difference ΔB is equal to or greater than the threshold value TH _q , the GOP target code amount calculation unit 133 adds the additional GOP target in proportion to the excess of the threshold value TH _B within a range not exceeding the surplus code amount G _r (n). The code amount G _d (n) is determined (step S503). In this case, G _d (n) is obtained by the following equation.

G _d (n) = min (G _r (n), a · (ΔB−TH _B ))
min () is a function that returns a minimum value, and a is a predetermined constant.

On the other hand, if the total difference ΔB is not equal to or greater than the threshold value TH _B , the additional GOP target code amount G _d (n) is set to 0 (step S504).

  The subsequent processing is the same as steps S105 to S111 in FIG.

Example 6
FIG. 7 is a flowchart of the video encoding process according to the sixth embodiment of the present invention. The difference between the sixth embodiment and the first to fifth embodiments described above is the method of calculating the surplus code amount G _r (n) in the GOP (n) period in the surplus code amount calculation unit 131.

Also in the sixth embodiment, video and audio are encoded in parallel. However, in the first to fifth embodiments, the surplus code amount G _r (n) in the GOP (n) period is calculated based on the generated code amount of the audio frame in the same display period as the video frame of GOP (n). On the other hand, in the sixth embodiment, based on the generated code amount of the audio frame in the same display period having the same length as that of the A video frame before the last video frame of GOP (n), n) The surplus code amount G _r (n) for the period is calculated. Here, A is a predetermined non-negative integer.

  Therefore, in this embodiment, before the start of video frame encoding of GOP (n), the audio encoding device 20 makes a period (length is GOP) of the last video frame of GOP (n) before the A video frame. (N) Same as period) It is assumed that the encoding of the audio frame in the same display period is completed.

In the sixth embodiment, the calculation accuracy of the surplus code amount G _r (n) is slightly worse than that of the above-described embodiment due to the time lag between the video coding period of GOP (n) and the sound generation code amount calculation period. However, since it is possible to shorten the time period for encoding speech in advance, the encoding delay time can be shortened as compared with the above-described embodiment.

  In the sixth embodiment, step S101 in the flowchart shown in FIG. 2 is replaced with step S601 in FIG.

In step S601, the surplus code amount calculation unit 131 of the video GOP target code amount determination unit 13 starts from the video frame period of GOP (n) based on the information of the audio generation code amount notified from the audio encoding device 20. For audio frames j to j + M−1 (M is the number of audio frames in the display period) in the same display period as the same long period before the A video frame, the surplus code amount G _r (n) in the GOP (n) period is Obtained by the formula.

G _r (n) = Σx _{= j} ^{j + M−1} {S _amax −S _a (x)}
Here, S _amax is the maximum generated code amount of each audio frame, and S _a (x) is the generated code amount of the x-th audio frame.

  The subsequent processing is the same as steps S102 to S111 of FIG. 2 in the first embodiment, but the determination of the surplus code amount use condition may be performed using the method of the second to fifth embodiments described above. In this case, steps S102 to S104 in FIG. 2 are performed in steps S202 to S204 in FIG. 3 in the case of the second embodiment, steps S302 to S304 in FIG. 4 in the case of the third embodiment, and in the case of the fourth embodiment. 5 further replaces steps S402 to S404 in FIG. 5 and, in the case of the fifth embodiment, steps S502 to S504 in FIG.

Example 7
FIG. 8 is a flowchart of the video encoding process according to the seventh embodiment of the present invention. The difference between the seventh embodiment and the first to sixth embodiments described above is that, in the first to sixth embodiments described above, the audio extra code amount is used for video coding, whereas in the seventh embodiment, the code is changed. The surplus code amount of the data stream other than the video stream to be superimposed on the encoded stream is calculated as the surplus code amount G _r (n) in the GOP (n) period in the surplus code amount calculation unit 131.

  In this embodiment, the amount of data bits of data to be multiplexed in the encoded stream at the same decoding time as the video frame of GOP (n) is known before the start of video frame encoding of GOP (n). And The reference video bit rate in this case refers to a video bit rate that can be secured when the bit amount of the data frame is always the maximum.

  In the seventh embodiment, step S101 in the flowchart shown in FIG. 2 is replaced with step S701 in FIG.

In step S701, the surplus code amount calculation unit 131 of the video GOP target code amount determination unit 13 uses the data frames j to j + M−1 (required on the receiving side at the same time as the video frame decoding time of GOP (n). For M) (the number of data frames in the same period as GOP (n)), the surplus code amount G _r (n) in the GOP (n) period is obtained by the following equation.

G _r (n) = Σx _{= j} ^{j + M−1} {S _dmax −S _d (x)}
Here, S _dmax is the maximum generated code amount of each data frame, and S _d (x) is the generated code amount of the x-th data frame.

  The subsequent processing is the same as steps S102 to S111 in FIG. 2 in the first embodiment. However, as in the sixth embodiment, the surplus code amount use condition is determined using the method of the second to fifth embodiments. You may go.

  The above video encoding processing can be realized by a computer and a software program, and the program can be recorded on a computer-readable recording medium or provided through a network.

It is a figure which shows the structural example of the apparatus which concerns on the Example of this invention. It is a flowchart of the video encoding process of Example 1 of this invention. It is a flowchart of the video encoding process of Example 2 of this invention. It is a flowchart of the video encoding process of Example 3 of this invention. It is a flowchart of the video encoding process of Example 4 of this invention. It is a flowchart of the video encoding process of Example 5 of this invention. It is a flowchart of the video encoding process of Example 6 of this invention. It is a flowchart of the video encoding process of Example 7 of this invention. It is a figure explaining the subject of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Video coding apparatus 11 Video input part 12 Video input buffer 13 Video GOP target coding amount determination part 131 Surplus code amount calculation part 132 Condition determination part 133 GOP target code amount calculation part 14 Video frame target code amount determination part 15 Video frame Encoding processing unit 16 Video stream output unit 17 Video stream output buffer 18 Activity / scene change analysis unit 20 Audio encoding device 30 Multiplexing unit

Claims (8)

A video code amount control method for controlling a video code amount so that an encoded stream obtained by multiplexing video encoded data and audio encoded data falls within a predetermined bit rate range,
A process of calculating a surplus code amount of audio in a period of a video encoding control unit from a coded audio generation code amount;
Determining whether or not to add a surplus code amount to a target code amount in a video encoding control unit, and determining a video feature or encoding condition that affects a predetermined generated video amount;
When it is determined that the condition is satisfied, a part or all of the excess code amount is added to the target code amount in the video encoding control unit, and when it is determined that the condition is not satisfied, the excess code amount Determining the target code amount in the video encoding control unit to be encoded next, without adding to the target code amount in the video encoding control unit;
A video code amount control method comprising: encoding a video signal in a video encoding control unit according to the determined target code amount. In the video code amount control method according to claim 1,
The condition is that the average quantization parameter of a predetermined number of past video frames is greater than or equal to a predetermined threshold, or that the average quantization step of a past predetermined number of video frames is greater than or equal to a predetermined threshold, or The condition that the average activity value of the video encoding control unit to be encoded is greater than or equal to a predetermined threshold, the condition that there is a scene change in the video encoding control unit to be encoded, or the past predetermined number of video frames A video code amount control method, characterized in that the total sum of the differences between the target code amount and the generated code amount is equal to or greater than a predetermined threshold. In the video code amount control method according to claim 1 or 2,
The surplus code amount of the audio is determined as a difference between a predetermined maximum generated code amount of each audio encoding control unit and an actual generated code amount in the audio encoding control unit group in the same display period as the video encoding control unit. A video code amount control method, characterized by being calculated from a sum. In the video code amount control method according to claim 1 or 2,
The audio encoding control unit group having the same display period as the video frame group having the same length as the video encoding control unit preceding the video encoding control unit by a predetermined number of video frames. A video code amount control method, comprising: calculating a sum of differences between a predetermined maximum generated code amount and an actual generated code amount in each audio encoding control unit. A video code amount control method for controlling a video code amount so that an encoded stream obtained by multiplexing video encoded data and other encoded data is within a predetermined bit rate range,
Calculating a surplus code amount of the other encoded data in a period of a video encoding control unit from a generated code amount of the other encoded data that has been encoded;
Determining whether or not to add a surplus code amount to a target code amount in a video encoding control unit, and determining a video feature or encoding condition that affects a predetermined generated video amount;
When it is determined that the condition is satisfied, a part or all of the excess code amount is added to the target code amount in the video encoding control unit, and when it is determined that the condition is not satisfied, the excess code amount Determining the target code amount in the video encoding control unit to be encoded next, without adding to the target code amount in the video encoding control unit;
A video code amount control method comprising: encoding a video signal in a video encoding control unit according to the determined target code amount. A video encoding device that controls the amount of video code and encodes a video signal so that an encoded stream obtained by multiplexing video encoded data and audio encoded data falls within a predetermined bit rate range. And
Means for obtaining an encoded audio generation code amount and calculating a surplus code amount of audio in a period of a video encoding control unit;
Means for determining whether or not to add a surplus code amount to a target code amount in a video encoding control unit, a video feature or encoding condition that affects a predetermined generated code amount of video;
When it is determined that the condition is satisfied, a part or all of the excess code amount is added to the target code amount in the video encoding control unit, and when it is determined that the condition is not satisfied, the excess code amount Means for determining the target code amount in the video encoding control unit to be encoded next, without adding to the target code amount in the video encoding control unit;
A video encoding device, comprising: means for encoding a video signal in a video encoding control unit according to the determined target code amount.   A video code amount control program for causing a computer to execute the video code amount control method according to any one of claims 1 to 5.   A computer-readable recording medium having recorded thereon a video code amount control program for causing a computer to execute the video code amount control method according to any one of claims 1 to 5.

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