JPH07115651A - Video signal encoding system - Google Patents

Abstract

PURPOSE:To maintain satisfactory picture quality and to stabilize the rate even for a high-resolution signal by dividing a picture, parallelly processing the divided pictures and simultaneously quantizing them with in-image encoding and inter-image encoding as components. CONSTITUTION:Signal power 201 between average images inputted from an input terminal 1a, signal power 202 within an average image inputted from an input terminal 1b, reference quantization step parameter 203 inputted from an input terminal 1c and type identification signal 204 inputted from an input terminal 1d are inputted to a target complexity degree calculation circuit 3a. Its output 205 is inputted to a target amount calculation circuit 4a, remaining buffer capacity 206 inputted from an input terminal 1e is inputted to the circuit 4a, the output of the circuit 4a is inputted to a virtual remaining buffer capacity calculation circuit 5a, and a signal generation amount 208 inputted from an input terminal 1f is inputted to the circuit 5a. The output of the circuit 5a is inputted to the calculation circuit 6a, and its output is inputted to a quantization circuit 7a. An adaptive quantization coefficient is inputted from an input terminal 1g to the circuit 7a, and a quantization step parameter 212 is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal coding system, and more particularly to a video signal quantization control system.

[0002]

2. Description of the Related Art FIG. 7 shows, for example, ISO-IEC / JTC1 / SC29 / WG11 M.
FIG. 11 is a schematic block diagram for explaining a conventional video signal encoding system shown in PEG 92 / N0245 Test Model 2. In the figure, the digitized video signal 1101 input from the input terminal 101c is the first input of the subtractor 9,
First input of motion compensation prediction circuit 16 and quantization circuit 1
1 to the second input. Output 1102 of subtractor 9
Is given to the first input of the quantization circuit 11 via the DCT circuit 10. The output 1104 of the quantization circuit 11 is given to the input of the transmission buffer 19 via the variable length coding circuit 18, and the dequantization circuit 12 and the IDCT are also provided.
It is provided to the first input of the adder 14 via the circuit 13. The output 1107 of the adder 14 is supplied to the first input of the memory circuit 15, and the output 1108 of the memory circuit 15 is supplied.
Are provided to the second input of the motion compensation prediction circuit 16 and the first input of the switching circuit 17. The second input of the memory circuit 15 is connected to the first output 1 of the motion compensation prediction circuit 16.
111 is given. On the other hand, the zero signal is given to the second input of the switching circuit 17, and the second output 11 of the motion compensation prediction circuit 16 is supplied to the third input of the switching circuit 17.
10 is given. Output 1109 of switching circuit 17
Are applied to the second input of the subtractor 9 and the second input of the adder 14. On the other hand, the second output 1113 of the transmission buffer 19 is given to the third input of the quantization circuit 11, and the first output 1114 of the transmission buffer 19 is output to the output terminal 2d.
Will be output.

FIG. 8 shows, for example, ISO-IEC / JTC1 / SC29 / WG11 MPE.
FIG. 11 is a schematic block diagram for explaining an example of a quantization control method in the conventional video signal encoding method shown in G 92 / N0245 Test Model 2. In the figure, the input terminal 101
The first generated code amount 1201 input from d is given to the first input of the complexity calculation circuit 20a, and the input terminal 10
The first average quantization step parameter 1202 input from 1e is given to the second input of the complexity calculation circuit 20a. The first complexity 1203 output from the complexity calculating circuit 20a is the first complexity of the target bit amount calculating circuit 4e.
Given to the input of. The second generated code amount 1204 input from the input terminal 101f is given to the first input of the complexity calculation circuit 20b, and the second average quantization step parameter 1205 input from the input terminal 101g is the complexity calculation. It is applied to the second input of the circuit 20b. The second complexity 1206, which is the output of the complexity calculating circuit 20b, is given to the second input of the target bit amount calculating circuit 4e. The third generated code amount 1207 input from the input terminal 101h is given to the first input of the complexity calculation circuit 20c, and the third average quantization step parameter 1208 input from the input terminal 101i is the complexity calculation. Circuit 20c
Given to the second input of. The third complexity 1209, which is the output of the complexity calculating circuit 20c, is given to the third input of the target bit amount calculating circuit 4e.

The fourth input of the target bit amount calculation circuit 4e is the first remaining number 1 from the input terminal 101j.
210 has a second input from the input terminal 101k for the fifth input.
1211 is input. The sixth input has a constant Kp1212, which is the output of the constant generating circuit 21a.
However, the constant Kb1213, which is the output of the constant generation circuit 21b, is input to the seventh input. Further, the remaining code amount 1214 is input to the eighth input from the input terminal 101l. A picture type 1215 is input to the ninth input from the input terminal 101m.

The target bit amount 1217, which is the output of the target bit amount calculation circuit 4e, is given to the first input of the virtual buffer selection circuit 22a. The generated code amount input from the input terminal 101c is input to the second input of the virtual buffer selection circuit 22a. A picture type 1215 is input to the third input from the input terminal 101m. The target bit amount 1218, which is the first output of the virtual buffer selection circuit 22a, is input to the first input of the first virtual buffer remaining amount calculation circuit 5e, and the generated code amount 1219, which is the second output, is the first output. It is input to the second input of the virtual buffer remaining amount calculation circuit 5e. Target bit amount 12 which is the third output of the virtual buffer selection circuit 22a
20 is the first input of the second virtual buffer remaining amount calculation circuit 5f, and the generated code amount 1221 which is the fourth output is the second input.
Is input to the second input of the virtual buffer remaining amount calculation circuit 5f. The target bit amount 1222, which is the fifth output of the virtual buffer selection circuit 22a, is input to the first input of the third virtual buffer remaining amount calculation circuit 5g, and the generated code amount 1223, which is the sixth output, is the third output. Virtual buffer remaining amount calculation circuit 5
input to the second input of g.

The output 1224 of the first virtual buffer remaining amount calculating circuit 5e is supplied to the first input of the virtual buffer selecting circuit 22b and the output 1224 of the second virtual buffer remaining amount calculating circuit 5f.
25 is a second input of the virtual buffer selection circuit 22b,
Output 1226 of the third virtual buffer remaining amount calculation circuit 5g
Is applied to the third input of the virtual buffer selection circuit 22b. For the fourth input of the virtual buffer selection circuit 22b,
The picture type 1215 is input from the input terminal 101m. The output 1227 of the virtual buffer selection circuit 22b is
The reference quantization step parameter 1228 that is given to the quantization step parameter calculation circuit 6e and is the output of the quantization step parameter calculation circuit 6e is given to the first input of the adaptive quantization circuit 7e. The adaptive quantization coefficient 1229 is applied to the second input of the adaptive quantization circuit 7e from the input terminal 101n. The quantization step parameter 1230 output from the adaptive quantization circuit 7e is output to the output terminal 2
It is output from e.

FIG. 9 is a conceptual diagram of the refresh system, which is one of the prominent properties of the hybrid coding system.

Next, the operation will be described. As one of high-efficiency coding schemes for coding a video signal, there is a hybrid coding scheme in which inter-picture predictive coding using motion compensation prediction and intra-picture transform coding are combined. This conventional example also employs the above hybrid coding method. In this case, the digitized input signal is subjected to DCT in the spatial axis direction by taking the difference between the images using motion compensation prediction in order to reduce the redundancy in the time axis direction. The transformed coefficients are quantized, variable-length coded, and then transmitted through a transmission buffer.

The basic concept of quantization control will be described below. Generally, in a video signal encoding system, the transmission rate is fixed, so that a method for converging the generated code amount to the transmission rate is required. The concept of the method of converging the generated code amount to the fixed transmission rate is shown below. In general, the converted coefficient cannot always be expressed with a finite number of digits. Representing this coefficient with a finite number of digits is called quantization, a discrete value by quantization is called a quantization level, and an interval between quantization levels is called a quantization step. Also, the difference between the coefficient before quantization and the quantization level after quantization is called quantization noise. If the quantization step is made smaller, the quantization noise will be reduced, but the generated code amount will be increased.If the quantization step is made larger, the quantization noise will be increased, but the generated code amount will be reduced. Become. Controlling the quantization step in this way is called quantization control. That is, the quantization control makes it possible to converge the generated code amount to the transmission rate. At this time, it is an important subject to converge to a fixed rate while maintaining good image quality. In this conventional example, a quantization step parameter is used as an index similar to the quantization step. The function of the quantization step parameter may be considered to be equivalent to the quantization step.

The following two are defined as units for performing quantization control. Standard fixed rate period Standard control period

The reference fixed rate period means a unit or period in which the generated code amount is determined to be a fixed rate. For example, the sum of the generated code amounts in a certain number of screens may be a fixed rate, or the generated code amount in one screen may be a fixed rate.
If this fixed rate period is large, the tolerance of fluctuations in the generated code amount within that period increases. For example, in a moving image, the generated code amount changes for each picture as the image moves. Therefore, in order to continuously obtain stable image quality, it is effective that the fixed rate period is large.
However, a buffer with a large capacity is required in order to increase the tolerance of fluctuations in the generated code amount. A large capacity buffer means an increase in delay time in the encoding / decoding system. On the other hand, if the fixed rate period is small, the admissibility of the generated code amount becomes low. For example, if the fixed rate period is set to a fraction of the screen, it is not possible to sufficiently allow the fluctuation of the generated code amount in the screen. For example, in a moving image, there is often a case where only one part in the screen is moving. In such a case, the degree of image quality deterioration in the screen varies greatly depending on the position in the screen. there is a possibility. However, in this case, the buffer capacity may be small, which means that the delay time in the coding / decoding system is small.

The reference control period is defined as follows. Basically, the quantization control is to check the state of the generated code amount every certain period, verify whether or not it matches the desired generated code amount, and change the quantization step parameter if it does not match. That is the work. The above period is defined as the standard control period. If this reference control period is large, the code amount becomes excessively large or small, which easily causes a buffer overflow or underflow. If this reference period is short, overflow or underflow is unlikely to occur, but a high degree of accuracy is required to predict the desired generated code amount. Uncertain prediction of the desired amount of generated code causes unnecessary fluctuation of the quantization step parameter,
This causes local deterioration of image quality.

In describing the quantization control method in this conventional example, the hierarchical structure of the video signal in this conventional example will be defined, and one property of the hybrid coding related to the hierarchical structure will be described below.

The hierarchical structure of the video signal in this conventional example is outlined as follows. Sequence: Consists of one or more consecutive GOPs. GOP: Composed of a plurality of consecutive pictures (screens). Picture: One screen, which is composed of multiple slices. Slice: It consists of one or more macroblocks. Macro block: It consists of four luminance blocks and a color difference block at the same position on the screen. Block: One block is composed of 8 × 8 pixels. In this conventional example, three types of pictures are defined. There are three types: I picture that does not perform inter-picture predictive coding but only intra-picture conversion coding, P picture that predicts from only one direction, and B picture that predicts from both directions.

Next, one of the prominent properties of the hybrid coding system is listed below. In this conventional example, inter-picture predictive coding using motion compensation prediction is performed. this is,
Since it is basically time-domain predictive coding, it is necessary to set an initial value. Further, in order to prevent the propagation of an error that occurs accidentally after encoding, it is necessary to set the initial value at an appropriate cycle. This periodic initial value setting operation is generally called periodic refresh. The periodic refresh in the case of the hybrid method using inter-picture predictive coding using motion compensation prediction and intra-picture transform coding is specifically intra-picture transform coding without motion-compensated prediction.

Generally, as the refresh method, there are a method of collectively performing screens and a method of performing divided screens. The method referred to in the conventional example is the former,
The refresh screen is called an I picture. In the case of the screen division refresh method, for example, the screen is divided into several areas, and one area is refreshed for each screen. FIG. 9 shows a conceptual diagram of the refresh method. In general, intra-picture transform coding has a larger amount of generated code than inter-picture predictive coding, and therefore, when performing periodic refresh in screen units, a large reference fixed rate period of about several pictures is adopted. This means that the delay time in the encoding / decoding system is large.

Next, the quantization control method in the conventional example will be described. FIG. 8 is a diagram for explaining an example of the quantization control method in the conventional example. In this conventional example, basically, one GOP period is adopted as the reference fixed rate period and one macroblock period is adopted as the reference control period. The quantization control is performed in the following procedure. Estimate the bit amount (target bit amount) that can be used in the encoding of the next picture. The reference value of the quantization step parameter for each macroblock is set based on the estimated target bit amount and the actually generated code amount. The reference value of the quantization step parameter is changed according to the feature of the image for each macroblock, and the final quantization step parameter for each macroblock is determined.

The details will be described below. As the first procedure, the amount of bits that can be used in encoding the next picture is estimated. Introducing the concept of complexity in this work.
In this conventional example, complexity is defined for each picture type. Also, the complexity is updated every time one picture is encoded. In reality, since the coded picture has a certain picture type, one complexity will be updated each time one picture is coded. Immediately before encoding the f-th picture of the g-th GOP, the complexity Xi (g, f) of the I picture and the complexity Xp of the P picture
The complexity Xb (g, f) of (g, f) and B picture is defined as follows. Xi (g, f) = Si (s, x) × Qi (s, x) Xp (g, f) = Sp (t, y) × Qp (t, y) Xb (g, f) = Sb (u , z) × Qb (u, z) At this time, Si (s, x) is the actual amount of generated code in the xth picture of the sGOP, which is the closest I picture in the past, Sp (t, y). Is the actual amount of generated code in the y-th picture of the t-th GOP, which is the closest P-picture, and Sb (u, z) is the z-th picture of the u-GOP, which is the B-picture that was closest in the past. This is the actual generated code amount. (At this time, any one of the above three pictures must correspond to the f-1th picture of the gGOP.) Also, Qi (s, x), Qp (t, y), Qb (u, z) is the average value of the actual quantization step parameters in the above three pictures.

Based on the above-mentioned complexity, the target bit amount T (g, f) of the f-th picture of the g-th GOP is estimated as follows.

[0020]

[Equation 1]

[0021] R (g, f) is the g-th GO
It is the total number of remaining bits allocated to the g-th GOP immediately before the P-th f-th picture is encoded, and is updated as follows after the encoding of each picture. R (g, f) = R (g, 1)-{S (g, 1) + S (g, 2) +… + S (g, f-
1)} Here, S (g, f-1) represents the actual generated code amount in the (f-1) th picture of the gth GOP. Further, the following calculation is performed before the head picture of the GOP is encoded. R (g + 1,1) = G + R (g, f + 1) G = BIT_RATE × (F / PICTURE_RATE) At this time, F is the number of pictures per GOP, and R (1, 1) = G Further, Fp (g, f) and Fb (g, f) are the number of pictures of the P picture and the B picture which remain unencoded in the current GOP immediately before encoding the fth picture of the gth GOP. Show.

Next, as the second procedure, the reference value of the quantization step parameter for each macroblock is set based on the estimated target bit amount and the actual generated code amount. A virtual buffer is assumed when setting the reference value.
The virtual buffer is a buffer that roughly stores the difference between the target bit amount and the actual generated code amount. A virtual buffer is assumed for each picture. That is, if the picture is an I picture, the virtual buffer for the corresponding I picture is, if the picture is a P picture, the virtual buffer for the corresponding P picture is, and if the picture is a B picture, the corresponding B picture is Is used, and the buffer occupancy of the virtual buffer is changed. For example, if the picture type of the f-th picture of the g-th GOP is an I-picture, the occupation ratio di (g, f, m immediately before encoding the m-th macroblock of the f-th picture of the g-th GOP of the virtual buffer for I-pictures. ) Is defined as follows. di (g, f, m) = di (g, f, 1) + B (g, f, 1) + B (g, f, 2) +…
+ B (g, f, m-1)-{T (g, f) × ((m-1) / MB_cnt)} where MB_cnt is the number of macroblocks per picture, and B (g, f, m-1) f, m-1) is the actual generated code amount in the m-1th macroblock of the fth picture of the gth GOP. For di (g, f, 1), the buffer occupancy di (a, b, MB_cnt + 1) in the b-th picture of the a-th GOP, which is the picture of the same type that existed in the closest past, is adopted. Also, P
The occupancy rate dp (g, f, m) of the virtual buffer for pictures and the occupancy rate db (g, f, m) of the virtual buffers for B pictures are similarly updated according to the picture type.

The virtual buffer occupancy ratios di (g, f, m), dp (g,
Based on f, m) and db (g, f, m), the reference value Qr (g, f, m) of the quantization step parameter of the m-th macroblock of the f-th picture of the g-th GOP is calculated as follows. It If (the f-th picture of the g-th GOP is an I-picture) Then Qr (g, f, m) = (di (g, f, m) / VB) × 31 If (the f-th picture of the g-th GOP is a P-picture) Then Qr (g, f, m) = (dp (g, f, m) / VB) × 31 If (the f-th picture of the g-th GOP is a B-picture) Then Qr (g, f, m) = (db (g, f , m) / VB) × 31 At this time, VB: virtual buffer capacity.

Next, as the third procedure, the above Qr (g, f,
Based on m), the final quantization step parameter for each macroblock is determined. In the present embodiment, the adaptive quantization coefficient K (g, f,
m) is obtained, and the final quantization step parameter Q (g, f, m) for each macroblock is calculated as follows. Q (g, f, m) = Qr (g, f, m) × K (g, f, m)

[0025]

The conventional quantization control method in the video signal coding method does not sufficiently consider the hardware configuration. For example, the conventional example is
It is good as long as it handles a signal having a resolution similar to that of an NTSC signal, but is not necessarily good at handling an HDTV signal or a signal with a higher resolution. In addition, the quantization control method in the conventional example is basically targeted for the case where the screen is periodically refreshed collectively, and is not optimized for the case where the screen is divided and the periodic refresh is performed. . Also, the method of calculating the complexity and the quantization step parameter is not quantitatively optimal, and no scene change has been dealt with.

The present invention has been made in order to solve the above-mentioned problems, and has a quantization control method capable of coping with high resolution signals, a quantization control method suitable for a screen division refresh method, and a quantitative property. It is an object of the present invention to obtain a quantization control method based on it, and also to obtain a quantization control method that also considers scene changes.

[0027]

A video signal coding system according to claim 1 of the present invention comprises intra-picture coding and inter-picture coding as constituent elements, divides a screen and performs parallel processing, and batches the screen. Then, it has a means for controlling the quantization.

The video signal coding method according to the second aspect of the present invention has means for estimating the complexity of the coded image or the generated code amount for each divided area.

The video signal coding system according to claim 3 of the present invention has means for using the intra-picture signal power, the inter-picture signal power and the quantization step parameter as an index for estimating the generated code amount. is there.

In the video signal coding method according to claim 4 of the present invention, the generated code amount of the past screen, the screen quantization step parameter in the past, and the current screen quantization step are used as an index for estimating the generated code amount. It has a means to use parameters.

The video signal encoding system according to the fifth aspect of the present invention has a means for detecting the change rate of the image and controlling the quantization step parameter based on the change rate.

[0032]

According to the video signal coding system of claim 1 of the present invention, the intra-picture coding and the inter-picture coding are constituent elements, and the screen is divided into parallel processings and the screens are collectively quantized and controlled. As a result, good image quality is maintained and rate stability is achieved even with high resolution signals.

According to the video signal coding method of the second aspect of the present invention, when the complexity of the coded image or the generated code amount is estimated for each divided area, the periodic refresh is performed with the screen divided. Also achieves good image quality maintenance and rate stability.

In the video signal coding method according to the third aspect of the present invention, the stability of the rate is realized by using the intra-picture signal power, the inter-picture signal power and the quantization step parameter as an index for estimating the generated code amount. .

In the video signal coding method according to claim 4 of the present invention, the generated code amount of the screen in the past, the quantization step parameter of the past screen, and the quantization step parameter of the current screen are used as an index for estimating the generated code amount. To achieve rate stability.

According to the video signal coding method of the fifth aspect of the present invention, the rate stability is realized even at the scene change by detecting the change rate of the image and controlling the quantization step parameter based on the change rate.

[0037]

【Example】

Example 1. The first embodiment of the present invention will be described below. FIG. 2 is a schematic block diagram for explaining an example of the quantization control system in the first embodiment of the present invention. In the figure, the average inter-image signal power 201 input from the input terminal 1a is the first input of the target complexity calculation circuit 3a, and the average intra-image signal power 202 input from the input terminal 1b is the target complexity calculation The reference quantization step parameter 203 input from the input terminal 1c to the second input of the circuit 3a is the target complexity calculation circuit 3a.
The type identification signal 204 input from the input terminal 1d is input to the third input of the target complexity calculation circuit 3a.
Given to the input of. The output 205 of the target complexity calculation circuit 3a is the first bit of the target bit amount calculation circuit 4a.
To the input of, the remaining buffer capacity 2 input from the input terminal 1e
06 is given to the second input of the target bit amount calculation circuit 4a. The target bit amount 207 output from the target bit amount calculation circuit 4a is the first input of the virtual buffer remaining amount calculation circuit 5a, and the generated code amount 208 input from the input terminal 1f is the virtual buffer remaining amount calculation circuit 5a.
provided to the second input of a. The output 209 of the virtual buffer remaining amount calculation circuit 5a is given to the input of the quantization step parameter calculation circuit 6a. The reference quantization step parameter 210, which is the output of the quantization step parameter calculation circuit 6a, is given to the first input of the adaptive quantization circuit 7a. The second input of the adaptive quantizer is the input terminal 1
An adaptive quantization coefficient 211 is given from g. The quantization step parameter 212 for each macroblock, which is the output of the adaptive quantization circuit 7a, is output from the output terminal 2a.

FIG. 3 is a diagram showing a schematic relationship between the complexity referred to in the quantization control method and the generated code amount in the first embodiment of the present invention.

The operation will be described below. In recent years, the development of high-efficiency coding apparatus for video signals has been shifting to the development of high-resolution systems including HDTV signals. At this time, the high-resolution system inevitably requires high-speed processing. Generally, by adopting parallel processing, high speed performance is supplemented. FIG. 1 is a diagram showing a main hierarchical structure of a video signal in the first embodiment.
FIG. 1B is a diagram in which the picture in FIG. 1A is vertically divided into S pieces. At this time, each of the S divided areas is called a sub-picture, and each sub-picture becomes a unit for performing parallel processing. It should be noted that the divided area of the sub-picture is not limited to this example. FIG. 1C is a diagram in which each sub-picture is further divided into L pieces. At this time,
Within each sub-picture, each of the L divided areas is referred to as GOB (Group of Block).
It should be noted that the GOB division area does not follow only this example. Further, as shown in FIG. 1D, GOBs existing at the same position in each sub-picture are collectively called a slice. still,
As in the conventional example, macroblocks and blocks exist as lower layers of GOB. Even in the case of parallel processing, in order not to cause the image quality deterioration depending on the position on the screen, the quantization control is performed on each sub-picture at once.
That is, it must be treated as a picture. At this time, basically, GOBs existing at the same position in each sub-picture
However, if they are processed at the same time, the quantization control will be processed in slice units. It should be noted that the slice is for the purpose of collectively processing the regions processed at the same time, and the divided regions do not follow only this example.

FIG. 2 is a diagram for explaining an example of the quantization control method in the first embodiment of the present invention. In the present embodiment, basically, one picture period is used as a reference fixed rate period as a reference. One slice period is adopted as the control period, and the quantization control is performed according to the following procedure based on the main hierarchical structure. Estimate the bit amount (target bit amount) that can be used for encoding each slice of the next picture. The reference value of the quantization step parameter for each macroblock is set based on the estimated target bit amount and the actually generated code amount. The reference value of the quantization step parameter is changed according to the feature of the image for each macroblock, and the final quantization step parameter for each macroblock is determined.
In the present embodiment, the case of performing parallel processing or the case of dividing a screen and performing periodic refreshing is also considered. Therefore, in this embodiment, GOB will be described as a basic unit.

The details will be described below. As the first procedure, the amount of bits that can be used for encoding each slice of the next picture is estimated. For this work, in this embodiment,
For each GOB, a pattern target complexity and a motion target complexity are defined. The pattern target complexity is
The target complexity is defined based on the intra-image signal power, and the motion target complexity is the complexity defined based on the inter-image signal power.

The image signal power Eint is defined as follows, for example, in macroblock units. When the macroblock size is P (pixels) × Q (lines) and the signal value of the (p, q) component of the macroblock is V (p, q), P, Q: constants representing the macroblock size p, q: constants that represent the position within the macroblock

[0043]

[Equation 2]

It is assumed that The in-image signal power Eint does not have to comply with the above definition as long as it is an index indicating the complexity of the pattern of the input image. For example, the absolute value sum or the absolute value sum of squares of the conversion coefficients excluding the DC component after the input signal is subjected to the conversion coding and the specific quantization is performed for each conversion coefficient may be used.

The inter-picture signal power Emc is defined as follows, for example, in macroblock units. The macroblock size is P × Q, and (p,
When the signal value of the q) component is V (p, q) and the signal value of the (p, q) component of the motion compensation prediction block of the macroblock is R (p, q),

[0046]

[Equation 3]

It is assumed that The inter-image signal power Emc does not have to comply with the above definition as long as it is an index representing the complexity of the movement of the input image. For example, the sum of absolute values or the sum of absolute values squared after transform-encoding the signal after motion compensation prediction and performing specific quantization for each transform coefficient may be used.

The picture target complexity Yint (f, h, s) and the motion target complexity Ymc (f, h, s) of the sth subpicture of the hth slice of the fth picture are the function fint and the function fm.
It is defined as follows using c. Yint (f, h, s) = fint (GOBaverage_Eint (f-1, h, s), Q (f,
h, s)) Ymc (f, h, s) = fmc (GOBaverage_Emc (f-1, h, s), Q (f,
h, s)) then GOBaverage_Eint (f-1, l, s) and GOBaverage
_Emc (f-1, l, s) is the average Eint and the average Emc of the s-th sub-picture of the l-th slice of the f-1th picture, and Q
(f, h, s) is the average value of the quantum or step parameters actually used in the s-th sub-picture of the l-th slice of the f-th picture. Also, depending on the delay due to the hardware configuration, GOBaverage_Eint (f-1, h, s) or GOBaverage_Emc
When (f-1, h, s) cannot be used, it is defined as follows. Yint (f, h, s) = fint (GOBaverage_Eint (f-2, h, s), Q (f,
h, s)) Ymc (f, h, s) = fmc (GOBaverage_Emc (f-2, h, s), Q (f,
h, s))

In the above definition, the functions fint and fmc are
It is defined as follows. FIG. 3A shows GOBaverage_Eint of the s-th sub-picture of the l-th slice of the f-th picture.
3 is a diagram showing a schematic relationship between (f, h, s) and the generated code amount Sint (f, h, s) when the GOB is intra-coded, and FIG.
(B) is the GOBa of the s-th phase of the l-th slice of the f-th picture
It is a figure which shows the schematic relationship between verage_Emc (f, h, s) and the generated code amount Smc (f, h, s) when the said GOB is inter-image coded.
As is clear from the figure, GOBaverage_Eint (f, h, s) and Q
It is possible to estimate Sint (f, h, s) from (f, h, s). This estimated generated code amount is the pattern target complexity Yint. Similarly, Smc (f, h, s) can also be estimated, and this estimated generation amount is the motion target complexity Ymc. Function fin
t and fmc are determined based on the above quantitative properties.

By the way, in the present embodiment, both the screen batch refresh and the screen division refresh are assumed as the periodic refresh. Further, it is assumed that the screen division refresh area is a slice unit. That is, it may be considered that there are cases where intra-picture coding is performed in slice units. Based on the above, the target complexity Y (f, h, s) of the s-th phase of the l-th slice of the f-th picture is the GOB
Is defined as follows depending on whether or not the slice to which is belongs to is an intra-coded slice. If (The slice type to which the GOB belongs is an intra-frame coding slice) Then Y (f, h, s) = Yint (f, h, s) Else Y (f, h, s) = Ymc (f, h , s)

The target complexity of each slice is defined based on the target complexity of each GOB. The f
The target complexity Y (f, h) of the 1st slice of the frame is
It is defined as follows. Y (f, h) = Y (f, h, 1) + Y (f, h, 2) + ... + Y (f, h, S) (S; number of subpictures)

Next, the bit amount (target bit amount) usable in each slice of the next picture is estimated based on the target complexity of each slice and the remaining buffer capacity. Target bit amount of each slice of f-th picture
T (f, h) (1 ≦ l ≦ L) is assumed as follows after the encoding of the f−1th picture is completed. T (f, h) = [Y (f, h) / {Y (f, 1) + Y (f, 2) +… + Y (f, L)}]
× [BIT_RATE / PICTURE_RATE-{BE (f, 1)-BIT_RATE
However, in the process of obtaining Y (f, h, s), Q (f-1, L, s) is used instead of Q (f, h, s). At this time, BIT_RATE: transmission rate PICTURE_RATE: number of pictures per second TE: reference accumulation time constant, and BE (f, h) is the transmission buffer remaining immediately before encoding the 1st slice of the fth picture. Indicates the amount.

If all Y (f, h) cannot be defined in the initial state immediately after the start of encoding, T (f, h) is defined as follows. T (f, h) = [1 / L] × [BIT_RATE / PICTURE_RATE-(BE
(f, 1) -BI_RATET × TE}] Further, BE (f, 1) in the initial state is defined as follows, for example. BE (f, h) = BIT_RATE / PICTURE_RATE When BE (f, 1) cannot be used due to the delay due to the hardware configuration, for example, the latest available buffer remaining capacity is used.

Next, as the second procedure, the reference value of the quantization step parameter for each macroblock is set based on the estimated target bit amount and the actually generated code amount. A virtual buffer is assumed when setting the reference value. The virtual buffer is a buffer that roughly stores the difference between the target bit amount and the actual generated code amount. In this embodiment, one virtual buffer is assumed. The occupancy rate d (f, h) of the virtual buffer immediately before encoding the l-th slice of the f-th frame is defined as follows. d (f, h) = {S (1,1) + S (1,2) +… + S (1, L) + S (2,1) + S (2,2) +
… + S (2, L)… + S (f-1,1) + S (f-1,2) +… + S (f-1, L) + S (f, 1) + S
(f, 2) +… + S (f, h-1)}-{T (1,1) + T (1,2) +… + T (1, L) + T (2,
1) + T (2,2) +… + T (2, L)… + T (f-1,1) + T (f-1,2) +… + T (f-1,
L) + T (f, 1) + T (f, 2) + ... + T (f, h-1)} At this time, S (f-1, h) is the actual value in the l-th slice of the f-th picture. Is the amount of code generated. When S (x, y) cannot be used due to the hardware configuration, S (x, y) is defined as follows, for example. S (x, y) = Y (x, y) The original value of S (x, y) will be applied as soon as it becomes available.

The quantization step parameter is changed by associating the occupation rate of the virtual buffer with the quantization step parameter. For example, if there is no difference between the target bit amount set for each slice and the actual generation amount, the virtual buffer occupancy does not change and the quantization step parameter does not change. If there is a difference between the above two,
The virtual buffer occupancy changes, and the quantization step parameter is modified according to the change. For example, when the generated code amount exceeds the target bit amount,
The difference is the increase amount of the virtual buffer occupation rate. The virtual buffer occupancy corresponds to the quantization step parameter, and an increase in the virtual buffer occupancy leads to an increase in the quantization step parameter. Increasing the quantization step parameter will reduce the subsequent generated code amount.

Based on the virtual buffer occupancy ratio d (f, h),
The reference value Qr (f, h) of the quantization step parameter of the l-th slice of the f-th picture is calculated as follows using the function fq. Qr (f, h) = fq (d (f, h)) function fq is, for example, Qr (f, h) = 31 × {d (f, h) / r}, where r = BIT_RATE
/ PICTURE_RATE or Qr (m, n) = 31 × d (f, h) / r where r = BIT_RATE
Possible / PICTURE_RATE. Alternatively, it is determined based on the generated code amount and the quantitative property of the quantization step parameter.

Next, as the third procedure, the above Qr (g, f,
Based on m), the final quantization step parameter for each macroblock is determined. In the present embodiment, the adaptive quantization coefficient K (g, f,
m) is obtained, and the final quantization step parameter Q (g, f, m) for each macroblock is calculated as follows. Q (g, f, m) = Qr (g, f, m) × K (g, f, m)

Example 2. The second embodiment of the present invention will be described below. The second embodiment differs from the first embodiment in the target complexity calculation process. In the first embodiment,
The GOB is implicitly classified into two types, that is, intra-picture coding and inter-picture coding, and the target complexity is calculated. (At this time, to be exact, the latter is a hybrid coding of inter-picture coding and intra-picture coding.) However, in reality, a macroblock and inter-picture coding for performing intra-picture coding in one GOB are performed. In some cases, macroblocks to be converted are mixed. Based on this, the l-th of the f-th picture
Target complexity Y (f, h,
s) is defined as follows using the function fintandmc. Y (f, h, s) = fintandmc (GOBaverage_Eint (f-1, h, s), Ei
nt_num (f-1, h, s), GOBaverage_Emc (f-1, h, s), Emc_num
(f-1, h, s), Q (f, h, s)) At this time, Eint_num (f-1, h, s): the number of intra-picture coding macroblocks in the GOB Emc_num (f-1, h) , s): the number of inter-picture coded macroblocks in the GOB. For example, the function fintandmc is defined based on the quantitative property as in the first embodiment.

Example 3. The third embodiment of the present invention will be described below. The third embodiment differs from the first embodiment in the process of calculating the target complexity. FIG. 4 shows the third aspect of the present invention.
4 is a schematic block diagram for explaining an example of a quantization control method in the embodiment of FIG. In the figure, the reference quantization step parameter 401 input from the input terminal 1h is
The generated code amount 402 input from the input terminal 1i to the first input of the target complexity calculation circuit 3b is the type identification signal 403 input from the input terminal 1j to the second input of the target complexity calculation circuit 3b. Is given to the third input of the target complexity calculation circuit 3b. The output 404 of the target complexity calculation circuit 3b is given to the first input of the target bit amount calculation circuit 4b, and the remaining buffer capacity 405 input from the input terminal 1k is input to the second input of the target bit amount calculation circuit 4b. Given. Target bit amount 406 output from the target amount calculation circuit 4b
Is supplied to the first input of the virtual buffer remaining amount calculation circuit 5b, and the generated code amount 407 input from the input terminal 1h is supplied to the second input of the virtual buffer remaining amount calculation circuit 5b. The output 408 of the virtual buffer remaining amount calculation circuit 5b is supported by the input of the quantization step parameter calculation circuit 6b. The reference quantization step parameter 409, which is the output of the quantization step parameter calculation circuit 6b, is given to the first input of the adaptive quantization circuit 7b. An adaptive quantization coefficient 410 is given to the second input of the adaptive quantization circuit 7b from the input terminal 1m. The quantization step parameter 411 for each macroblock, which is the output of the adaptive quantization circuit 7b, is output from the output terminal 2b.

The operation will be described below. The third embodiment differs from the third embodiment in the target complexity calculation process. Similar to the first embodiment, as the first procedure, the bit amount usable in each slice of the next picture is estimated. FIG. 5 is a conceptual diagram of the slice type of the quantization control method in the third embodiment of the present invention, and FIG.
An example of screen division periodic refresh is shown. In general, the calculation of the target complexity is performed by the GOB in the past picture existing at the same position on the screen as the GOB.
Refer to the information in. At this time, in the case of the screen division periodic refresh, the information of the reference GOB cannot be used as it is. Because G
Depending on the type of slice to which the OB and the reference GOB belong (for example, whether it is an intra-coded slice or not),
For example, the amount of generated code varies greatly. Figure 5 (b)
As described above, in the third embodiment, for example, a combination of three slice types can be considered.

Based on the above, in the third embodiment, for example, three types of target complexity are defined as follows. Intra / non-intra target complexity Yint / mc (f, h, of the sth sub-block of the h-th slice of the f-th picture
s), non-intra / intra target complexity Ymc / int
(f, h, s) and non-intra / non-intra target complexity Ymc / mc (f, h, s) can be calculated as follows using function fint / mc, function fmc / int and function fmc / mc. Is defined. Yint / mc (f, h, s) = fint / mc (S (f-1, h, s), Q (f-1, h, s),
Q (f, h, s)) Ymc / int (f, h, s) = fmc / int (S (f-1, h, s), Q (f-1, h, s),
Q (f, h, s)) Ymc / mc (f, h, s) = fmc / mc (S (f-1, h, s), Q (f-1, h, s),
Q (f, h, s)) At this time, S (f-1, h, s) is the generated code amount in the sth sub-block of the l-th slice of the f-1th picture,
Q (f-1, h, s) is the s-th slice of the l-th slice of the f-1th picture.
It is the quantization step parameter actually used in the sub-picture.

Further, due to the delay due to the hardware configuration, GOBaverage_Eint (f-1, h, s) or GOBaverage_Emc
When (f-1, h, s) cannot be used, it is defined as follows. Yint / mc (f, h, s) = fint / mc (S (f-2, h, s), Q (f-2, h, s),
Q (f, h, s)) Ymc / int (f, h, s) = fmc / int (S (f-2, h, s), Q (f-2, h, s),
Q (f, h, s)) Ymc / mc (f, h, s) = fmc / mc (S (f-2, h, s), Q (f-2, h, s),
Q (f, h, s))

Based on the above, the target complexity Y (f, f, f) of the s-th sub-picture of the l-th slice of the f-th picture is finally obtained.
h, s) is a slice type SliceType (f, h, s) of the s-th sub-picture of the l-th slice of the f-th picture and a slice type SliceType (f of the s-th sub-picture of the l-th slice of the f-1th picture. -1, h, s) is defined as follows. if (SliceType (f-1, h, s) is an intra-coded slice) &
(SliceType (f, h, s) is the inter-coded slice) then Y (f, h, s) = Yint / mc (f, h, s) if (SliceType (f-1, h, s) is the image Inter-coded slice) &
(SliceType (f, h, s) is the intra-image coding slice) then Y (f, h, s) = Ymc / int (f, h, s) if (SliceType (f-1, h, s) is the image Inner coding slice) &
(SliceType (f, h, s) is an intra-coded slice) then Y (f, h, s) = Ymc / mc (f, h, s)

In the above definition, the function fint / mc, the function fmc
/ int and the function fmc / mc are defined based on the quantitative property as in the first embodiment.

Example 4. The fourth embodiment of the present invention will be described below. The fourth embodiment includes a process of detecting a scene change from the input video signal and changing the quantization step parameter. FIG. 6 is a schematic block diagram for explaining an example of the quantization control method in the fourth exemplary embodiment of the present invention. In the figure, the video signal 610 input from the input terminal 1t is applied to the scene change detection circuit 8. The output 611 of the scene change detection circuit 8 is given to the second input of the quantization step parameter calculation circuit 6c.

Next, the operation will be described. Generally, the amount of generated codes increases at the scene change. A sudden change in the generated code amount is likely to cause an unnecessary change in the quantization step parameter. Also, it is generally said that the visual resolution characteristics deteriorate immediately after a scene change.
The fourth embodiment has an operation of detecting the rate of change of an image and intentionally keeping the generated code amount at a normal level at the time of a scene change. For example, the image change rate is detected as follows. The pixel value of the (i, j) component of the f-1th picture is V (f-1, i, j), and the pixel value of the (i, j) component of the fth picture is V (f, i, j). Image change rate ch of the f-th picture
Define ange (f) as follows.

[0067]

[Equation 4]

At this time, the number of pixels per picture is I ×
Let's say J. For example, in consideration of the image change rate change (f), the offset amount is given to the occupancy rate of the virtual buffer of the f-th picture as follows. d (f, 1) = d (f, 1) + fob (change (f)) However, at the end of the f-th picture, the offset amount is reduced as follows. d (f + 1,1) = d (f + 1,1)-fob (change (f)) At this time, the function fob is determined based on the quantitative property. Alternatively, in consideration of the image change rate change (f), an offset amount is given to the reference quantization step parameter of the f-th picture as follows. Qr (f, h) = fq (d (f, h)) + foq (Schange (f)) At this time, the function foq is determined based on the quantitative property.

[0069]

As described above, according to the first aspect of the present invention, there is an effect that a quantization control system capable of coping with high resolution signals can be obtained.

According to the second aspect of the present invention, there is an effect that a quantization control system suitable for the case where the screen is divided and the periodic refresh is performed.

According to the third aspect of the present invention, there is an effect that the quantization control system based on the quantitative property can be obtained.

According to the fourth aspect of the present invention, there is an effect that the quantization control system based on the quantitative property can be obtained.

According to the fifth aspect of the present invention, there is an effect that the quantization control system in consideration of the scene change can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a main hierarchical structure of a video signal according to a first embodiment of the present invention.

FIG. 2 is a schematic block diagram for explaining an example of a quantization control method in the first exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a schematic relationship between complexity and a generated code amount referred to in the quantization control method in the first exemplary embodiment of the present invention.

FIG. 4 is a schematic block diagram for explaining an example of a quantization control method in a third exemplary embodiment of the present invention.

FIG. 5 is a conceptual diagram of slice types of a quantization control method according to a third embodiment of the present invention.

FIG. 6 is a schematic block diagram for explaining an example of a quantization control system according to a fourth exemplary embodiment of the present invention.

FIG. 7 is a schematic block diagram for explaining a conventional video signal encoding system.

FIG. 8 is a schematic block diagram for explaining an example of a quantization control method in a conventional video signal encoding method.

FIG. 9 is a conceptual diagram of a refresh method.

[Explanation of symbols]

 1 Input Terminal 2 Output Terminal 3 Target Complexity Calculation Circuit 4 Target Bit Amount Calculation Circuit 5 Virtual Buffer Remaining Capacity Calculation Circuit 6 Quantization Step Parameter Calculation Circuit 7 Adaptive Quantization Circuit 8 Scene Change Detection Circuit 9 Subtractor 10 DCT Circuit 11 Quantum Decoding circuit 12 Dequantization circuit 13 IDCT circuit 14 Adder 15 Memory circuit 16 Motion compensation prediction circuit 17 Switching circuit 18 Variable length coding circuit 19 Transmission buffer 20 Complexity calculation circuit 21 Constant generation circuit 22 Virtual buffer selection circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Nakai No. 1 Baba Institute, Nagaokakyo City Video System Development Laboratory, Mitsubishi Electric Co., Ltd. (72) Inventor Takahiro Fukuhara 5-11 1-1 Ofuna, Kamakura-shi Mitsubishi Electric Corporation Company Communication Systems Laboratory

Claims (5)

[Claims] 1. A video signal coding system for coding a video signal, which is a video signal coding system having intra-picture coding and inter-picture coding as constituent elements, wherein a screen is divided and processed in parallel. A video signal coding method, characterized in that the screen is collectively quantized and controlled. 2. A video signal coding system for coding a video signal, the video signal coding system comprising intra-picture coding and inter-picture coding as constituent elements, wherein a screen is divided into a plurality of areas. A video signal coding method, characterized in that the complexity of a coded image or the amount of generated code is estimated for each area. 3. A video signal coding system for coding a video signal, the video signal coding system comprising intra-picture coding and inter-picture coding as constituent elements, wherein the complexity or occurrence of a coded image A video signal coding method characterized by using intra-picture signal power, inter-picture signal power, and a quantization step parameter as an index for estimating the code amount. 4. A video signal coding system for coding a video signal, the video signal coding system comprising intra-picture coding and inter-picture coding as constituent elements, wherein the complexity or occurrence of a coded image A video signal coding method characterized in that a past code amount generated in a screen, a past screen quantization step parameter, and a present screen quantization step parameter are used as an index for estimating a code amount. 5. A video signal coding system for coding a video signal, the video signal coding system having intra-picture coding and inter-picture coding as constituent elements, wherein a change rate of an image is detected, A video signal encoding method characterized in that a quantization step parameter is controlled based on the rate of change.