JP2003299081A - Encoder, encoding method, program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decide the maximum value of a sum value sum<SB>-</SB>sup of a bit supply quantity, according to the margin of a VBV (video buffering verifier) buffer size. <P>SOLUTION: In a step S31, the generating code amount of a nearest I picture is detected, and in a step S32, it is determined that max<SB>-</SB>sum<SB>-</SB>sup=VBV buffer size is the generating amount of the I picture. In a step S33, it is judged that a scene change occurs. If it is judged that the scene change occurs in a step S34, the encoding difficulties of the I picture of the scene change and an I picture before one picture are obtained. In a step S35, the difference between the two I pictures in coding difficulty are calculated, and the value of max<SB>-</SB>sum<SB>-</SB>sup calculated in the step S32 is increased or decreased on the basis of the difference in the coding difficulty, i.e., a scene change from a difficult image to an easy image or a scene change from the easy image to the difficult image. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coding device, a coding method, a program, and a recording medium, and particularly to a coding device suitable for use in a bit rate control in feedback rate control. And an encoding method, a program, and a recording medium.

[0002]

2. Description of the Related Art In recent years, various compression coding methods have been proposed as a method of compressing video data and audio data to reduce the amount of information, of which MPEG2 is a typical one.
(MovingPicture Experts Group Phase 2) is available.

In such an image compression method, TM5 (Test Model
There is 5). In step 1 of TM5, the target bit to be given for each picture is calculated. When calculating the target bit, the GC for each picture type is used.
The bit amount R that can be assigned to the remaining pictures in the GOP (Group of Pictures) is proportionally distributed according to each ratio of (Global Complexity), and the bit amount to be assigned to each picture is calculated.

TM4 is an excellent method for making the amount of generated bits per GOP almost constant, but when performing fixed rate coding, it is not always necessary to make the amount of generated bits of GOP constant. . In fixed-rate encoding, it is necessary to prevent the occupied amount of a VBV (Video Buffering Verifier) buffer from overflowing or underflowing a specified value.

In TM5, since the amount of generated bits per GOP is almost constant, the VBV buffer does not overflow or underflow. However, in TM5, the buffer capacity cannot be effectively used when encoding is performed at a low bit rate. For example, TM5 in MP @ PL of MPEG
, The VBV buffer capacity is about 1.8 Mbi.
However, since the number of bits per picture that is pulled out from the buffer is small, it is about 1.8 Mb.
It cannot be used effectively.

As described above, regardless of the input pattern,
By assigning a certain amount of bits, coding distortion will occur remarkably for pictures with high coding difficulty, while pictures with low coding difficulty will have less coding distortion. , As a whole, it becomes an unstable image with a lot of unevenness.

In order to solve such a problem, a larger amount of bits is allocated to a picture having a high degree of coding difficulty in a range where the buffer does not underflow, while a picture having a low degree of coding difficulty is distributed. Needs to allocate a small amount of bits suitable for the picture within the range where the buffer does not overflow.

Therefore, the applicant of the present invention has filed Japanese Patent Application Laid-Open No. 10-754.
43, a video data compression apparatus and method for adjusting the generated bit amount according to the complexity of a picture for each part of the video data so as to improve the quality of the video after compression as a whole. Disclosure.

In TM5, the available bit amount R that can be assigned to the remaining pictures of the GOP is an important parameter in rate control. For example, G
In the first half of the OP, images with complicated patterns continued, so if a large amount of bits were allocated, GOP
In the latter half of the above, the bit amount R becomes extremely small or becomes a negative number.

On the other hand, the applicant of the present invention has disclosed in Japanese Patent Laid-Open No. 10-7.
The bit replenishment rate control disclosed in 5443 is
A bit amount is added to or subtracted from the usable bit amount R allocated to a plurality of pictures to be encoded, depending on the image difficulty level of the encoding target and the VBV buffer occupancy amount (hereinafter, added Bits that can be or are subtracted are called supplements).

[0011]

The bit replenishment rate control that has been proposed in the past has been proposed in the case where information such as the difficulty levels of a plurality of picture images to be encoded is already known, that is, the feedforward (prefetching the encoding information). This is applied to feed forward type rate control. For example, after the data of 15 GOP data is accumulated, the image encoding difficulty level is judged, so that a certain delay occurs in the information accumulation. It is something that ends up.

However, with feedback (Feed Back) rate control in which prefetch information cannot be obtained, the future VBV margin cannot be accurately estimated, and therefore the maximum and minimum values of sum_supplement (hereinafter referred to as sum_sup). Was forced to use a fixed value determined by the bit rate and the usable VBV size.
However, in particular, when the maximum value of sum_sup is a fixed value, there is a problem that VBV underflow is likely to occur depending on the amount of generated pictures, and in order to prevent VBV underflow, the VBV margin Therefore, it was necessary to determine the maximum value of sum_sup.

The present invention has been made in view of such a situation, and it is possible to perform a bit replenishment rate control in a feedback type rate control.

[0014]

The encoding device of the present invention is
First detecting means for detecting the complexity of the uncompressed data, encoding means for compression-encoding the uncompressed data, and non-encoding detected in the past by the encoding means detected by the first detecting means. Based on the complexity of the compressed data, the second bit amount added to the usable first bit amount of the buffer capacity of the VBV buffer allocated to the uncompressed data to be encoded is calculated. Calculation means,
Second detection means for detecting the bit generation amount of the intra-frame coded image among the uncompressed data previously coded by the coding means and the second detection means from the buffer capacity of the VBV buffer. Setting means for calculating a value obtained by subtracting the bit generation amount of the generated intra-frame coded image and setting it as the maximum value of the total value of the second bit amounts.

A third detection means for detecting that the picture has changed from a predetermined reference value between the previous picture and the picture to be encoded next, and the third detection means make the predetermined picture. When the change from the reference value is detected, the second bit amount of the second bit amount set by the setting unit is determined based on the complexity of the intra-frame coded image before and after the change of the pattern detected by the first detecting unit. Resetting means for resetting the maximum value of the total value may be further provided.

The encoding method of the present invention is detected by the processes of the first detection step of detecting the complexity of uncompressed data, the encoding step of compressing and encoding the uncompressed data, and the first detection step. In addition, based on the complexity of the uncompressed data encoded in the past by the processing of the encoding step, the available capacity of the VBV buffer allocated to the uncompressed data to be encoded is A calculation step of calculating a second bit amount added to the bit amount of 1 and a bit generation amount of the intra-frame encoded image of the uncompressed data encoded in the past by the processing of the encoding step are detected. Second detection step, V
Setting for calculating a value obtained by subtracting the bit generation amount of the intra-frame coded image detected by the process of the second detection step from the buffer capacity of the BV buffer and setting it to the maximum value of the total value of the second bit amounts And a step.

The program recorded on the recording medium of the present invention includes a first detecting step for detecting the complexity of uncompressed data, an encoding step for compressing and encoding the uncompressed data, and a first detecting step. Of the buffer capacity of the VBV buffer allocated to the uncompressed data to be encoded in the future, based on the complexity of the uncompressed data encoded in the past by the processing of the encoding step detected by The calculation step of calculating the second bit amount added to the usable first bit amount, and the bit of the intra-frame encoded image of the uncompressed data encoded in the past by the processing of the encoding step. The second detection step of detecting the amount of generation and the intra-frame coded image detected by the processing of the second detection step from the buffer capacity of the VBV buffer It calculates a value obtained by subtracting the bit generation, characterized in that it comprises a setting step of setting the maximum value of the total value of the second bit quantity.

The program of the present invention is detected by the processing of the first detection step of detecting the complexity of uncompressed data, the encoding step of compressing and encoding the uncompressed data, and the processing of the first detection step. Based on the complexity of the non-compressed data encoded in the past by the processing of the encoding step, the first available buffer capacity of the VBV buffer allocated to the non-compressed data to be encoded from now on. A calculation step of calculating a second bit amount added to the bit amount, and a second step of detecting the bit generation amount of the intra-frame coded image of the uncompressed data coded in the past by the process of the coding step. Detection step of V
Setting for calculating a value obtained by subtracting the bit generation amount of the intra-frame coded image detected by the process of the second detection step from the buffer capacity of the BV buffer and setting it to the maximum value of the total value of the second bit amounts And a step.

In the encoding device, the encoding method, and the program of the present invention, the complexity of non-compressed data is detected, the non-compressed data is compression-encoded, and the complexity of non-compressed data encoded in the past is detected. Of the VBV buffer allocated to the uncompressed data to be encoded, a second bit amount added to the usable first bit amount is calculated, and the second bit amount is calculated. The bit generation amount of the intra-frame encoded image of the uncompressed data encoded in the past is detected by the processing, and the bit generation amount of the detected intra-frame encoded image is subtracted from the buffer capacity of the VBV buffer. A value is calculated and set to the maximum value of the total value of the second bit amounts.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an encoder 1 to which the present invention is applied.

The image rearrangement unit 12 rearranges the input uncompressed video data in the order of encoding. The scan conversion / macroblocking unit 13 performs picture / field conversion, and performs, for example, 3: 2 pulldown processing when the uncompressed video data is video data of a movie. Intra AC
The calculation unit 14 is processed by the image rearrangement unit 12 and the scan conversion / macroblocking unit 13, and the intra AC (intra A
Calculate C).

Since the I picture is compression-encoded without reference to other pictures, the ME residual, which will be described later, cannot be obtained. Therefore, the intra AC is used as a parameter in place of the ME residual in order to obtain the coding difficulty of the I picture. Intra AC is MP
It is a parameter defined as a sum of variance values of video data for each DCT block in the DCT processing unit in the EG method, which indicates the complexity of the video and correlates with the difficulty of the picture pattern of the video and the amount of data after compression. Have sex. That is, the intra AC is the total sum of absolute values in the screen obtained by subtracting the average value of the pixel values of each block from the pixel value of each pixel in DCT block units.
The intra AC is represented by the following equation (1).

[0024]

[Equation 1] ... (1)

Further, in the equation (1), the equation (2) is established.

[Equation 2] ... (2)

The intra AC calculator 14 outputs the calculated intra AC value to the difficulty calculator 32 of the rate controller 15.

The arithmetic processing unit 16 performs motion compensation on the supplied video data based on the motion compensation information supplied from the motion compensating unit 25, and outputs it to the DCT unit 18. The DCT unit 18 performs, for example, discrete cosine transform (DCT) processing on the video data input from the arithmetic processing unit 16 in units of macroblocks of 16 pixels × 16 pixels, and converts the time domain data to the frequency domain data. And outputs to the quantizer 19.

The quantizing unit 19 converts the frequency domain data input from the DCT unit 18 into the rate control unit 15.
Quantized by the quantization index Q supplied from the quantization index determination unit 35 of
It outputs to (Variable Length Code) unit 20 and inverse quantization unit 22.

The VLC unit 20 performs variable length coding processing on the quantized data input from the quantizing unit 19 based on a predetermined conversion table, and outputs the resulting variable length coded data to the buffer 21. To do.

The buffer 21 buffers the input coded data to form a coded bit stream.
Output sequentially.

The inverse quantization unit 22 inversely quantizes the quantized data input from the quantization unit 19 in the quantization step of the quantization executed by the quantization unit 19, and the inverse DCT unit 23 as the inverse quantized data. Output to.

The inverse DCT unit 23 performs inverse DCT processing on the inverse quantized data input from the inverse quantization unit 22,
It is output to the arithmetic processing unit 24.

The arithmetic processing unit 24 adds the output data of the motion compensation unit 25 and the output data of the inverse DCT unit 23,
It is output to the motion compensation unit 25. The motion detector 17
The motion vector is searched for a macroblock that minimizes the sum of absolute values or the sum of squared differences between the target macroblock of the picture to be compressed (input picture) and the referenced picture (reference picture). Is calculated and output to the motion compensation unit 25. The motion compensation unit 25 performs motion compensation processing on the output data of the arithmetic processing unit 24 based on the motion vector input from the motion detection unit 17, and outputs the data to the arithmetic processing units 24 and 16. To do.

The rate control unit 15 is composed of an ME residual calculation unit 31, a difficulty calculation unit 32, a genbit detection unit 33, a target bit determination unit 34, and a quantization index determination unit 35, and the target bit and the quantization index. To decide.

The ME residual calculation unit 31 calculates the ME residual, which is a parameter having a strong correlation with the image coding difficulty. By motion estimation, it is possible to obtain a motion vector that reduces the sum of absolute difference values from the reference frame to the input frame, but in that case, the error obtained by the sum of absolute difference values or the sum of squares. The power of the component is the ME residual. In the P picture and the B picture, the ME residual and the image coding difficulty are
It has an almost simple proportional relationship.

The difficulty level calculation unit 32 uses the ME residual calculation unit 31.
By the approximation with the ME residual input from Equation (3),
Also, the coding difficulty Dj of the P picture and the B picture is calculated using the equation (4).

[Equation 3] ... (3)

[Equation 4] ... (4)

Here, MEj is the j-th picture.
KE ME residual, a_P, A_B, B _P, B_BIs that
Is a slope and a correction value when approximated by a linear expression.

Further, the difficulty calculation section 32 similarly calculates the coding difficulty Dj of the I picture by approximation by the intra AC input from the intra AC calculation section 14, and outputs it to the target bit determination section 34.

Then, the difficulty level calculator 32 calculates the average difficulty level avgD for each GOP from the coding difficulty level Dj calculated for each picture.

The genbit detection unit 33 detects the generated bit amount genbit of the most recently encoded I picture from the encoded data buffered in the buffer 21, and outputs the value to the target bit determination unit 34. To do.

The target bit determination unit 34 receives the encoding difficulty Dj and the gen input from the difficulty calculation unit 32.
Amount of generated bits of I picture input from bit detector 33
The target bit of each picture of each picture type is calculated based on the genbit, and the rate control is performed.

That is, the target bit determining unit 34
Is the value of the supplement added to the usable bit amount R assigned to the plurality of pictures to be encoded, based on the difficulty of the past image that has been encoded by the process described later ( su
pplement is 0 for positive and negative values
May be). The target bit determination unit 34 determines the value of the target bit based on the usable bit amount R + supplement and outputs it to the quantization index determination unit 35.

The quantization index determination unit 35 generates a quantization index Q based on the target bit value input from the target bit determination unit 34, and outputs it to the quantization unit 19.

Next, referring to the flowchart of FIG.
A bit replenishment rate control process for determining the supplement to be added to R based on the degree of difficulty in the past image that has been encoded will be described.

In step S1, the target bit determining section 34 determines whether or not the picture currently being processed is the head of the GOP. In step S1, GO
When it is determined that it is not the head of P, the process of step S1 is repeated until it is determined that it is the head of GOP.

When it is determined in step S1 that the GOP is at the beginning, in step S2, the target bit determination unit 34 determines that the previous G from the difficulty level calculation unit 32 is determined.
Get the average difficulty level avgD in OP.

In step S3, a max_sum_sup calculation process described later with reference to FIG. 3 or 6 is executed.

In step S4, the target bit determining section 34 determines that avgD> 0x2000 and sum_sup <max_sum_s.
It is determined whether it is up. Here, 0x2000 which is compared with the average difficulty level avgD is a predetermined threshold value,
It is a value that can be set to obtain the required image quality while considering the image quality.

When it is determined in step S4 that avgD> 0x2000 and sum_sup <max_sum_sup, the target bit determination unit 34 determines in step S5.
A positive value supplement is added to the usable bit amount R. That is, since the previous GOP has a certain degree of difficulty or more, the target bit determination unit 34 predicts that the degree of difficulty of the GOP to be encoded is similar to that of the previous GOP, and can use the target bit. A positive value supplement is added to the bit amount R.

If it is determined in step S4 that avgD> 0x2000 and sum_sup <max_sum_sup are not satisfied,
In step S6, the target bit determination unit 34
Determines whether avgD <0x1000 and sum_sup> min_sum_sup. Here, 0x1000 compared with the average difficulty level avgD is a predetermined threshold value, which is a value smaller than 0x2000 described above (a value indicating that the image difficulty level is low), and is requested while considering the image quality. It is a value that can be set in order to obtain high image quality.

In step S6, avgD <0x1000,
And if it is determined that sum_sup> min_sum_sup,
In step S7, the target bit determination unit 34
Is a negative value for the available bit amount R
Add. That is, the target bit determination unit 34
Since the previous GOP had a certain level of difficulty or less (that is, a simple image), the difficulty of the GOP to be encoded is predicted to be the same as that of the previous GOP and can be used. Negative value of suppleme for bit amount R
add nt.

In step S6, avgD <0x1000,
When it is determined that sum_sup> min_sum_sup is not satisfied, the target bit determining unit 34 sets supplement = 0 in step S8. That is, the target bit determining unit 34 sets the available bit amount R to
Do not increase or decrease supplement.

After the processing of step S5, step S7, or step S8 is completed, the target bit determination unit 34 is used in step S5, step S7, or step S8 in step S9.
Using the value of supplement, sum_sup = sum_sup + supple
ment, the process returns to step S1 and the subsequent processes are repeated.

By the processing described with reference to FIG. 2, the usable bit amount R is added or reduced based on the difficulty level of the past image which has been encoded.
The value of ment is determined. For example, in GOP units, R + su
The previous GO if pplemet (supplement is a positive value, a negative value, or 0) is determined
Based on the average value of the image difficulty level of P (intra AC, ME residual, etc.), it is predicted that the difficulty level of the GOP to be encoded will be the same as the difficulty level of the previous GOP, and the usable bit Depending on the amount R, depending on the difficulty
supplement is added.

Although the image difficulty has been described as being calculated using the intra AC or ME residual, the image difficulty may be calculated using other parameters.

The method of calculating the specific value of the supplement may be, for example, the method disclosed in Japanese Patent Laid-Open No. 10-75443, or a method other than that may obtain the required image quality. You may make it use a value.

Further, although it has been described here that the average difficulty level avgD in the previous 1 GOP is used, the difficulty level calculation section 32 may replace the average difficulty level avgD in 1 GOP with, for example, a plurality of GOPs or GOPs. The average of the degree of difficulty may be calculated for a part of the above, or, instead of the simple average of the degree of difficulty, a weighted sum or a weighted average may be calculated as necessary.

Next, the max_sum_sup calculation process executed in step S3 of FIG. 2 will be described.

In Long GOP, the amount of I-pictures tends to increase. Therefore, in order to prevent VBV underflow depending on the amount of generated pictures, the maximum value of sum_sup (max_sum_sup) may be obtained by subtracting the bit generation amount of the most recent I picture after encoding from the VBV buffer size. .

The max_sum_sup calculation process 1 executed in step S3 of FIG. 2 will be described with reference to the flowchart of FIG.

In step S21, the genbit detector 3
3 detects the generated code amount genbit of the latest I picture. The target bit determination unit 34 includes a genbit detection unit 33.
Receives the value of genbit from.

In step S22, the target bit determining unit 34 sets the value of max_sum_sup, which is the maximum value of sum_sup, to max_sum_sup = VBV buffer size-I picture generation amount, and the process returns to step S4 in FIG.

By the processing described with reference to FIG. 3, as shown in FIG. 4, the total amount of the solid line arrow obtained by subtracting the I picture generation amount from the VBV size is defined as the next GB margin by the following G
It is the maximum value of sum_sup of OP. As a result, supplementation is less likely to be given to a pattern that easily underflows, and supplementation is likely to be given to a pattern that has a margin for underflow. That is, it is possible to prevent the VBV underflow that occurs due to the large amount of generated bits of the I picture.

However, the processing described with reference to FIG. 3 causes a problem when a scene change occurs. For example, when a scene change from a difficult design to a simple design occurs, as shown in FIG.
Because OP is a difficult pattern, max_sum_sup of the next GOP
GOP with large (total of solid line arrows) and simple design
Since the increased max_sum_sup will be applied to
The maximum value of sum_sup is increased for those with no VBV margin. Similarly, in the case of a scene change from a simple design to a difficult design, the opposite problem will occur.

In order to prevent this, when encoding a GOP including an I picture of a scene change, the previous I
The maximum value of sum_sup calculated from the picture generation amount is
It can be increased or decreased depending on the difficulty level of the I picture of the scene change.

The max_sum_sup calculation process 2 executed in step S3 of FIG. 2 will be described with reference to the flowchart of FIG.

In step S31, the genbit detector 3
3 detects the generated code amount genbit of the latest I picture. The target bit determination unit 34 includes a genbit detection unit 33.
Receives the value of genbit from.

In step S32, the target bit determination unit 34 sets the value of max_sum_sup which is the maximum value of sum_sup to max_sum_sup = VBV buffer size-I picture generation amount.

In step S33, the target bit determining section 34 determines whether or not there is a scene change. The determination as to whether or not there is a scene change is made by, for example, M
The determination may be made based on the ME residual value calculated by the E residual calculation unit 31, or may be made by any other method.

If it is determined in step S33 that the scene change has not occurred, the process proceeds to step S in FIG.
Return to 4.

When it is determined in step S33 that there is a scene change, in step S34, the target bit determination section 34 causes the difficulty level calculation section 32 to
The coding difficulty of the scene change I picture and the previous I picture is acquired.

In step S35, the target bit determination unit 34 calculates the difference in coding difficulty between the two I pictures, and max_sum_calculated in step S32.
The value of sup is increased or decreased based on the difference in encoding difficulty, that is, whether the scene change is from a difficult design to a simple design or from a simple design to a difficult design. , And returns to step S4 in FIG.

Specifically, if the encoding difficulty after the scene change is low, the value of max_sum_sup is decreased, and if the encoding difficulty after the scene change is high, max_sum_su is reached.
Increase the value of p.

When a GOP including an I picture of a scene change is encoded by the processing described with reference to FIG. 6, the maximum value of sum_sup obtained by the previous I picture generation amount is set to the difficulty level of the I picture of the scene change. By increasing or decreasing by, for example, although the I-picture generation amount of the next GOP is large and VBV has no margin,
It is possible to prevent things such as a large sum_sup maximum value.

Further, according to the present invention, when the bit replenishment rate control is performed other than the bit replenishment rate control processing described with reference to FIG. 2, that is, max_sum_sup, which is the maximum value of the integrated value sum_sup of the bit replenishment amount supplement, It is applicable to all the processes used.

The series of processes described above can be executed by hardware, but can also be executed by software. In this case, for example, the encoder 1
Is a personal computer 10 as shown in FIG.
It is composed of 1.

In FIG. 7, the CPU 111 uses the program stored in the ROM 112 or RA from the storage unit 118.
Various processes are executed according to the program loaded in M113. The RAM 113 also appropriately stores data necessary for the CPU 111 to execute various processes.

CPU 111, ROM 112, and RAM 113
Are mutually connected via a bus 114. An input / output interface 115 is also connected to the bus 114.

The input / output interface 115 includes an input unit 116 including a keyboard and a mouse, an output unit 117 including a display and a speaker, a storage unit 118 including a hard disk, a communication including a modem and a terminal adapter. The section 119 is connected. The communication unit 119 performs communication processing via a network including the Internet.

A drive 120 is also connected to the input / output interface 115 if necessary, and the magnetic disk 1
31, the optical disk 132, the magneto-optical disk 133, the semiconductor memory 134, or the like is appropriately mounted, and the computer program read from them is installed in the storage unit 118 as necessary.

When a series of processes are executed by software, a program that constitutes the software is installed in a computer in which dedicated hardware is installed, or various programs are installed to perform various functions. Is installed from a network or a recording medium into a general-purpose personal computer or the like capable of executing.

This recording medium, as shown in FIG.
A magnetic disk 131 (including a floppy disk) in which a program is stored, which is distributed in order to supply the program to a user separately from the apparatus body, and an optical disk 13.
2 (CD-ROM (Compact Disk-Read Only Memory),
DVD (including Digital Versatile Disk), magneto-optical disk 133 (including MD (Mini-Disk) (trademark),
Alternatively, in addition to being configured by a package medium including a semiconductor memory 134, a ROM 112 in which a program is stored and a hard disk included in a storage unit 118, which is supplied to a user in a state of being incorporated in the apparatus body in advance, is used. Composed.

In the present specification, the steps for writing the program stored in the recording medium are not limited to the processing performed in time series in the order of inclusion, but may be performed in parallel if they are not necessarily performed in time series. Alternatively, it also includes processes that are individually executed.

[0084]

According to the present invention, image data can be encoded. Further, according to the present invention, when the supplement to be added to the usable bit amount R is determined based on the degree of difficulty in the past image that has been encoded, the supp
Since you can set the maximum of the total value of lement,
VBV underflow can be prevented when the bit supplement rate control is applied to the feedback rate control.

When encoding a GOP in which a scene change has occurred, a value obtained by comparing the image difficulty levels of the intra-frame coded images before and after the scene change is used.
Since you can reset the maximum value of the total value of ment,
VBV underflow can be prevented when the bit supplement rate control is applied to the feedback rate control.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an encoder to which the present invention has been applied.

FIG. 2 is a flowchart illustrating a bit supply rate control process.

FIG. 3 is a flowchart illustrating a max_sum_sup calculation process 1.

FIG. 4 is a diagram for explaining a VBV buffer and a maximum value of sum_sup.

FIG. 5 is a diagram for describing a VBV buffer and a maximum value of sum_sup.

FIG. 6 is a flowchart illustrating a max_sum_sup calculation process 2.

FIG. 7 is a diagram illustrating a configuration of a personal computer.

[Explanation of symbols]

1 encoder, 12 image rearranging unit, 13 scanning conversion / macroblocking unit, 14 intra AC calculation unit, 15 rate control unit, 16 arithmetic processing unit, 17 motion detection unit, 18 DCT processing unit, 1
9 quantization unit, 20 VLC unit, 21 buffer,
22 inverse quantizer, 23 inverse DCT processor, 24
Arithmetic processing unit, 25 motion compensation unit, 31 ME residual calculation unit, 32 difficulty calculation unit, 33 genbit detection unit, 34 target bit determination unit, 35 quantization index determination unit

Continued front page    F term (reference) 5C059 KK01 KK22 KK35 MA00 MA05                       MA14 MA23 MC11 MC38 ME01                       NN01 NN21 NN43 PP05 PP06                       PP07 SS20 TA46 TA60 TB03                       TB04 TC02 TC03 TC10 TC14                       TC16 TC20 TC27 TC38 TC41                       TD03 TD05 TD06 TD12 UA02                       UA32 UA33 UA38 UA39

Claims (5)

[Claims] 1. An encoding device for encoding uncompressed data, comprising: first detecting means for detecting complexity of the uncompressed data; encoding means for compressing and encoding the uncompressed data; A buffer of a VBV buffer allocated to the uncompressed data that is to be encoded, based on the complexity of the uncompressed data that was previously encoded by the encoding unit and that was detected by the first detecting unit. Out of capacity
Calculating means for calculating a second bit amount to be added to the usable first bit amount, and bits of the intra-frame encoded image of the uncompressed data previously encoded by the encoding means Second detection means for detecting the amount of generation, and a value obtained by subtracting the bit generation amount of the intra-frame coded image detected by the second detection means from the buffer capacity of the VBV buffer are calculated, An encoding device, comprising: a setting unit configured to set a maximum value of a total value of two bit amounts. 2. A third detecting means for detecting that a picture has changed from a predetermined reference value between a previous picture and a picture to be encoded next, and the third detecting means, When it is detected that the pattern has changed from the predetermined reference value, the setting unit sets it based on the complexity of the intra-frame encoded image before and after the change of the pattern detected by the first detection unit. The encoding device according to claim 1, further comprising: a resetting unit that resets a maximum value of the summed values of the second bit amounts. 3. A coding method of a coding device for coding uncompressed data, comprising: a first detecting step of detecting complexity of the uncompressed data; and coding for compressing and coding the uncompressed data. Step, based on the complexity of the uncompressed data previously encoded by the process of the encoding step, detected by the process of the first detecting step, A calculation step of calculating a second bit amount to be added to the usable first bit amount of the buffer capacity of the VBV buffer allocated to the VBV buffer, and the encoding step performed in the past by the encoding step. The second detection step of detecting the bit generation amount of the intra-frame encoded image in the uncompressed data, and the second detection step from the buffer capacity of the VBV buffer. A setting step of calculating a value obtained by subtracting the bit generation amount of the intra-frame coded image detected by the processing of the detection step and setting the value to the maximum value of the total value of the second bit amounts. Encoding method. 4. A program for an encoding device that encodes uncompressed data, comprising a first detection step of detecting the complexity of the uncompressed data, and a code that compression-encodes the uncompressed data. An encoding step, and the uncompressed data to be encoded based on the complexity of the uncompressed data previously encoded by the processing of the encoding step, which is detected by the processing of the first detection step. Of the buffer capacity of the VBV buffer allocated to the second bit amount, which is added to the usable first bit amount, and a step of calculating the second bit amount that has been encoded in the past by the process of the encoding step. From the second detection step of detecting the bit generation amount of the intra-frame encoded image of the uncompressed data, and from the buffer capacity of the VBV buffer, the second detection step is performed. And a setting step of calculating a value obtained by subtracting the bit generation amount of the intra-frame coded image detected by the processing of the detection step and setting it to the maximum value of the total value of the second bit amounts. A recording medium on which a computer-readable program is recorded. 5. A program executable by a computer that controls an encoding device that encodes uncompressed data, the first detection step detecting complexity of the uncompressed data, and the uncompressed data. And a coding step for compressing and coding, based on the complexity of the non-compressed data previously coded by the processing of the coding step, detected by the processing of the first detection step. Of the buffer capacity of the VBV buffer allocated to the uncompressed data, the calculation step of calculating a second bit amount to be added to the usable first bit amount, and the encoding step. A second detection step of detecting the bit generation amount of the intra-frame encoded image of the uncompressed data encoded in the past, and the VBV buffer. Value obtained by subtracting the bit generation amount of the intra-frame coded image detected by the processing of the second detection step from the buffer capacity of the buffer, and set to the maximum value of the total value of the second bit amounts. A program including a setting step.