JPH07177513A - Video signal coding system - Google Patents

Abstract

PURPOSE:To allow the system to cope with periodic refresh for a divided picture by using number of non-zero conversion coefficients of a preceding picture and a quantized step parameter so as to estimate the degree of complexity of a coded picture or a generated code quantity. CONSTITUTION:A number 201 of non-zero transformation coefficients of a preceding picture, a quantization step parameter 202, a quantization step parameter 203 in a current picture and a type identification signal 204 are respectively given to 1st-4th inputs of a target complexity calculation means 3a. Furthermore, an output 205 and a buffer residual capacity 206 are given respectively to 1st and 2nd inputs of a target bit quantity calculation means 4a, a target bit quantity 207 and a generated code quantity 208 are given respectively to 1st and 2nd inputs of a virtual buffer residual capacity calculation means 5a, and an output 209 is given to an input of a quantization step parameter calculation means 6a. Moreover, a reference quantization step parameter 210 and an adaptive quantization coefficient 211 are given respectively to 1st and 2nd inputs of an adaptive quantization means 7a, from which 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. 9 shows, for example, ISO-IEC / JTC1 / SC29 / WG11.
FIG. 11 is a schematic block diagram showing a conventional video signal encoding system shown in MPEG 92 / N0245 Test Model 2. In the figure, the digitized video signal 1101 input from the input terminal 101a is applied to the first input of the subtractor 9, the first input of the motion compensation prediction circuit 16 and the second input of the quantization circuit 11. To be The output 1102 of the subtractor 9 is D
It is given to the first input of the quantization circuit 11 via the CT 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 circuit 1 are also provided.
3 to the first input of the adder 14. 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 to the second input of the motion compensation prediction circuit 16 and the first input of the switching circuit 17. . The second output of the memory circuit 15 is provided with the first output 1111 of the motion compensation prediction circuit 16. On the other hand, the second input of the switching circuit 17
A zero signal is provided, and the third input of the switching circuit 17 is provided with the second output 1110 of the motion compensation prediction circuit 16. The output 1109 of the switching circuit 17 is the subtractor 9
And the second input of adder 14. On the other hand, the second output 1113 of the transmission buffer 19 is supplied to the third input of the quantization circuit 11, and the transmission buffer 1
The first output 1114 of 9 is output from the output terminal 2e.

FIG. 10 shows, for example, ISO-IEC / JTC1 / SC29 / WG11.
FIG. 11 is a schematic block diagram showing an example of a quantization control method in the conventional video signal coding method shown in MPEG 92 / N0245 Test Model 2. In the figure, the first generated code amount 1201 input from the input terminal 101d is given to the first input of the complexity calculation circuit 20a, and the first average quantization step parameter 12 input from the input terminal 101e.
02 is given to the second input of the complexity calculation circuit 20a. The first complexity 1203, which is the output of the complexity calculating circuit 20a, is given to the first input of the target bit amount calculating circuit 4e. 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 up to the current macroblock which is the second output. Is the first
Is input to the second input of the virtual buffer remaining amount calculation circuit 5e. The target bit amount 1220 which is the third output of the virtual buffer selection circuit 22a is input to the first input of the second virtual buffer remaining amount calculation circuit 5f, and the generated code amount 1221 up to the current macroblock which is the fourth output. Is input to the second input of the second 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 up to the current macroblock, which is the sixth output. Is input to the second input of the third virtual buffer remaining amount calculation circuit 5g.

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 f.

FIG. 11 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. Figure 9
[Fig. 3] is a schematic block diagram of the hybrid coding system. 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, and after variable length coding,
It is transmitted via the 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 of 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 varies from screen to screen 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: One or more consecutive GOPs (Group of pi)
ctures). 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. This type is called a picture type.

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 a refresh method, as shown in FIG. 11, there are a method of collectively performing screens and a method of performing divided screens. The method referred to in the conventional embodiment is the former, and the refresh screen is the I picture. In the case of the screen division refresh method, FIG.
As shown in (b), for example, the screen is divided into several areas, and one area is refreshed for each screen. 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. 10 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 I picture that existed in the closest past, and Sp (t, y) is in the closest past. Sb (u, z) is the actual amount of generated code in the y-th picture of the t-th GOP, which is the P-picture, and is the actual amount of generated code in the z-th picture of the u-th GOP, which is the closest B picture that existed in the past. . (At this time, one of the above three pictures should 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 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 total number of remaining bits allocated to the g-th GOP immediately before the f-th picture of the g-th GOP is coded, and is updated as follows after the coding of each picture. R (g, f) = R (g, 1)-{S (g, 1) + S (g, 2) +… + S (g, f-1)} where S (g, f-1 ) Represents the actual generated code amount in the (f-1) th picture of the gGOP. 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 that 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)} At this time, MB_cnt is the number of macroblocks per picture, and B (g, f, m-1) is the f-th f of the g-th GOP. This is the actual amount of generated code in the m-1th macroblock of the picture. For di (g, f, 1), the buffer occupancy ratio 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. Further, the occupancy rate dp (g, f, m) of the virtual buffer for P pictures and the virtual buffer occupancy rate db (g, f, m) 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 quantization control method in the conventional video signal coding method is mainly intended for the case where the screen is collectively refreshed periodically.
It is not optimized for the case of dividing the screen and performing periodic refresh. Further, since the complexity is set on a screen-by-screen basis and the change in the complexity within the screen is not taken into consideration, the method of calculating the complexity and the quantization step parameter is not quantitatively optimum.

The present invention has been made to solve the above problems, and a video signal code provided with a quantization control method suitable for a screen division refresh method and a quantization control method based on quantitative properties. The purpose is to obtain the conversion method.

[0027]

A video signal coding system according to claim 1 of the present invention has a transform coding as a constituent element, and the complexity or generated code amount of a coded image is set to a non-zero value in a past screen. It is configured to perform estimation using the number of transform coefficients and the quantization step parameter in the past screen.

Further, the video signal coding method according to claim 2 of the present invention has transform coding as a constituent element, and the complexity or generated code amount of the coded image is converted into each transform before quantization in the past screen. The estimation is performed using the coefficient value and the quantization step parameter in the current screen.

Further, the video signal coding method according to claim 3 of the present invention comprises transform coding as a constituent element, and the complexity or the generated code amount of the coded image is converted into a transform coefficient before quantization in the past screen. It is configured to perform estimation using a representative value indicating a distribution of numerical values and a quantization step parameter on the current screen.

Further, the video signal coding method according to claim 4 of the present invention has transform coding as a constituent element, and has means for classifying each transform coefficient before quantization by its size, The image complexity or the generated code amount is estimated using the class to which each transform coefficient in the past screen belongs and the quantization step parameter of the current screen.

[0031]

In the video signal coding system according to the first aspect of the present invention, the transform coding is used as a constituent element, and for each divided area,
Achieves good image quality and rate stability by estimating the complexity of the coded image or the generated code amount from the number of non-zero transform coefficients in the past screen and the quantization step parameter of the past screen To do.

The video signal coding method according to claim 2 of the present invention has transform coding as a constituent element, and for each divided area, the value of each transform coefficient before quantization in the past screen and the current screen. By estimating the complexity of the coded image or the generated code amount from the quantization step parameter, good image quality is maintained and rate stability is realized.

In the video signal coding method according to claim 3 of the present invention, the transform coding is a constituent element, and for each divided area, a representative value indicating a distribution of transform coefficient values before quantization in the past screen is set. By estimating the complexity of the coded image or the generated code amount from the quantization step parameter of the current screen, good image quality is maintained and rate stability is realized.

According to a fourth aspect of the present invention, the video signal coding system has a transform coding as a constituent element, and has means for classifying each transform coefficient before quantization according to its size, and for each divided area. In addition, by estimating the complexity of the coded image or the generated code amount from the class to which each transform coefficient in the past screen belongs and the quantization step parameter of the current screen, good image quality maintenance and rate stability can be achieved. To be realized.

[0035]

EXAMPLES Example 1. Hereinafter, Embodiment 1 will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a quantization control system in a video signal coding system according to an embodiment of the present invention. In the figure, the number 201 of non-zero conversion coefficient values in the past screen input from the input terminal 1a
Is the quantization step parameter 202 in the past screen input from the input terminal 1b to the first input of the target complexity calculating means 3a, and the second input of the target complexity calculating means 3a from the input terminal 1c. The input quantization step parameter 203 in the current screen is input to the third input of the target complexity calculating unit 3a, and the type identification signal 204 input from the input terminal 1d is input to the fourth input of the target complexity calculating unit 3a. Given to input. The output 205 of the target complexity calculation unit 3a is given to the first input of the target bit amount calculation unit 4a, and the buffer remaining amount 206 inputted from the input terminal 1e is given to the second input of the target bit amount calculation unit 4a. To be The target bit amount 207 which is the output of the target bit amount calculating means 4a is the generated code amount 208 input from the input terminal 1f to the first input of the virtual buffer remaining amount calculating means 5a.
It is given to the second input of the virtual buffer remaining amount calculation means 5a. The output 209 of the virtual buffer remaining amount calculation means 5a is given to the input of the quantization step parameter calculation means 6a. The reference quantization step parameter 210, which is the output of the quantization step parameter calculation means 6a, is given to the first input of the adaptive quantization means 7a. Adaptive quantizer 7
An adaptive quantization coefficient 211 is given to the second input of a from the input terminal 1g. Quantization step parameter 21 for each macroblock which is the output of the adaptive quantization means 7a
2 is output from the output terminal 2a.

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. 2 is a diagram showing the main hierarchical structure of the video signal in the first embodiment. FIG. 2B is a diagram in which the picture in FIG. 2A 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. still,
The divided area of the sub-picture is not limited to this example. FIG. 2C is a diagram in which each sub-picture is further divided into L pieces. At this time, in each sub-picture, each of the L divided areas is GOB (Group).
of blocks). It should be noted that the GOB division area does not follow only this example. Further, as shown in FIG. 2D, GOBs existing at the same position in each sub-picture are collectively called a slice. As in the conventional example, there are macroblocks and blocks 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 in the screen, the quantization control needs to treat all sub-pictures collectively, that is, as a picture. At this time, basically, when GOBs existing at the same position in each sub-picture are processed at the same time, the quantization control is 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.

This embodiment basically adopts one picture period as the reference fixed rate period and one slice period as the reference control period, and the quantization control is based on the above-mentioned main hierarchical structure and follows the procedure below. Is done. 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 this 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, it is performed by referring to the information of the GOB in the past picture existing at the same position on the screen as the GOB.

First, the number 201 of non-zero transform coefficients in the past picture input from the input terminal 1a is accumulated for each GOB in the target complexity calculation means 3a. Here, the sum total of the number of non-zero transform coefficients in the GOB corresponding to the sth subpicture of the hth slice of the fth picture is represented as X (f, h, s). The target complexity calculation means 3a calculates the target complexity Y (f, h, s) of the s-th sub-picture of the h-th slice of the f-th picture.
As X (f-1, h, s) of the f-1th picture obtained as described above.
And a quantization step parameter Q (f−1, h, s) used in the s-th sub-picture of the h-th slice of the f−1-th picture and a quantum used in the s-th sub-picture of the h-th slice of the f-th picture. Optimization step parameter Q (f, h, s) and type identification signal ty
From pe (f, h, s) and the function F1, we define as follows. Y (f, h, s) = F1 (X (f-1, h, s), Q (f-1, h, s), Q (f, h, s), type (f, h, s) However, in reality, the s-th slice of the h-th slice of the f-th picture
Immediately before encoding the sub-picture, since the quantization step parameter Q (f, h, s) used in the GOB is undecided, instead of Q (f, h, s), Q (f-1, L, s) is used.

In the above definition, the function F1 is defined as follows. First, FIG. 3 shows X (f, h, s) of the s-th sub-picture of the h-th slice of the f-th picture and the generated code amount Sx (f, h, s).
It is a figure which shows the schematic relationship of s). As shown in the figure, the code amount Sx
(f, h, s) is X (f, h, s) and the quantization step parameter Q (f, h, s
It can be estimated from However, since X (f, h, s) cannot be known before encoding the s-th sub-picture of the h-th slice of the f-th picture, X (f-1, h, s) becomes
X (f, h, s) is estimated from Q (f-1, h, s) and Q (f, h, s). FIG. 4 is a diagram showing a schematic relationship between X (f, h, s) and Q (f, h, s). Thus, X (f, h, s) is the quantization step parameter Q (f, h, s
s), so when Q (f-1, h, s) changes to Q (f, h, s), the expected value of X (f-1, h, s) is X (f, h, s)
I think. As already mentioned, since Q (f, h, s) is actually undetermined, assuming that the quantization control is stable,
The value Q (f-1, L, s) that seems to be the closest to Q (f, h, s) is
used instead of h, s).

Further, in the case of the screen division refresh, the estimated value of the generated code amount Sx (f, h, s) of the s-th sub-picture of the h-th slice of the f-th picture is whether the GOB is intra-picture coded. It is also necessary to change depending on whether it is inter-picture coding or whether the GOB at the same position in the previous picture is intra-picture coding or inter-picture coding. Therefore, the estimated code amount Sx (f, h, s) is corrected by the type identification signal type (f, h, s). Type identification signal type (f, h, s)
There are the following four values. type (f, h, s) = 0: The s-th sub-picture of the h-th slice of the (f-1) -th picture is intra-picture coding, and the s-th sub-picture of the h-th slice of the f-th picture is inter-picture coding. type (f, h, s) = 1: The s-th sub-picture of the h-th slice of the (f-1) -th picture is inter-picture coding, and the s-th sub-picture of the h-th slice of the f-th picture is inter-picture coding. type (f, h, s) = 2: The s-th sub-picture of the h-th slice of the (f-1) -th picture is intra-picture coding, and the s-th sub-picture of the h-th slice of the f-th picture is intra-picture coding. type (f, h, s) = 3: The s-th sub-picture of the h-th slice of the (f-1) -th picture is inter-picture coding, and the s-th sub-picture of the h-th slice of the f-th picture is intra-picture coding.

FIG. 5 is a flow chart showing the process of calculating the target complexity referred to in the quantization control method in the first embodiment, showing the procedure for estimating the generated code amount Sx (f, h, s). There is. The function F1 is the flowchart of FIG.
It is summarized in two functions, X (f-1, h, s), Q (f-1, h, s,
s), Q (f, h, s), type (f, h, s) and generated code amount Sx (f, h, s)
, And outputs the estimated value as the target complexity Y (f, h, s). Note that FIG. 5 is an example of the function F1 and is not limited to this procedure. In the encoding device to which the video signal encoding system according to the present invention is applied, the function F1 is the above-mentioned 4
ROM that outputs target complexity Y (f, h, s) from one value
Can be configured as

Target complexity Y (f, h, s) of each GOB
, The target complexity of each slice is defined. Target complexity Y of the h-th slice of the f-th frame
(f, h) is defined as follows. Y (f, h) = Y (f, h, 1) + Y (f, h, 2) + ... + Y (f, h, S)
(S; number of sub-pictures)

Next, the target bit amount calculation means 4a
Estimates the bit amount (target bit amount) that can be used in each slice of the next picture based on the target complexity of each slice and the remaining buffer capacity. Target bit amount T (f, h) of each slice of the f-th picture (1 ≦ h
≦ 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 × TE}] However, in the above equation, BIT_RATE: Transmission rate PICTURE_RATE: Number of pictures per second TE: Reference accumulation time constant, BE (f, h) is the h-th picture of the f-th picture. Indicates the remaining amount of the transmission buffer immediately before encoding the slice.

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)-BIT_RATE × TE}] In addition, BE (f, 1) in the initial state is, for example, Define. BE (f, h) = BIT_RATE / PICTUR
E_RATE Moreover, due to the delay due to the hardware configuration, BE (f,
If 1) is not available, for example, the latest available buffer 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 virtual buffer remaining amount calculation means 5a uses the occupancy of the virtual buffer immediately before encoding the h-th slice of the f-th frame.
d (f, h) 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 generated code amount in the h-th slice of the f-th picture.

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.

Quantization step parameter calculating means 6a
Changes the quantization step parameter 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 two, the virtual buffer occupancy rate is changed, and the quantization step parameter is corrected 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 h-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 (f, h) = 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 (f, h)
Based on, the final quantization step parameter for each macroblock is determined. In this embodiment, the adaptive quantization coefficient K (f, h, m) is obtained based on the power of the original signal for each macroblock, and the final quantization step parameter Q (f, h) for each macroblock is as follows. , m) is calculated. Q (f, h, m) = Qr (f, h) × K (f, h, m)

Example 2. The second embodiment will be described below. This embodiment differs from the first embodiment in the target complexity calculation process.

FIG. 6 is a schematic block diagram showing a quantization control system in a video signal coding system according to an embodiment of the present invention. In the figure, the transform coefficient value 301 before the quantization in the past screen input from the input terminal 1h
Is the quantization step parameter 302 in the current screen input from the input terminal 1i to the first input of the target complexity calculating unit 3b, and the second input of the target complexity calculating unit 3b from the input terminal 1j. The inputted type identification signal 303 is given to the third input of the target complexity degree calculation means 3b. Target complexity calculation means 3
The output 304 of b is supplied to the first input of the target bit amount calculation means 4b, and the remaining buffer capacity 305 input from the input terminal 1k is supplied to the second input of the target bit amount calculation means 4b. The target bit amount 306 output from the target bit amount calculation means 4b is the first input of the virtual buffer remaining amount calculation means 5b, and the generated code amount 307 input from the input terminal 11 is the virtual buffer remaining amount calculation means 5b. Given to the second input of. The output 308 of the virtual buffer remaining amount calculation means 5b is given to the input of the quantization step parameter calculation means 6b. The reference quantization step parameter 309, which is the output of the quantization step parameter calculation means 6b, is given to the first input of the adaptive quantization means 7b. An adaptive quantization coefficient 310 is given to the second input of the adaptive quantization means 7b from the input terminal 1m.
The quantization step parameter 311 for each macroblock, which is the output of the adaptive quantization means 7b, is output from the output terminal 2b.

The operation will be described below. The second embodiment differs from the first embodiment in the target complexity calculation process. In this embodiment, the generated code amount of the current screen is estimated using the transform coefficient value before quantization in the past screen and the quantization step parameter of the current screen. That is, in the same hierarchical structure as in the first embodiment, each GOB is made up of a plurality of blocks, so that, for example, the sth sub-picture of the h-th slice of the f-1 picture is made up of N blocks. , The transformation coefficients after orthogonal transformation are Coeff (f-1, h, s, n, i, j) (n is the block number, n = 1, ..., N; i is the horizontal Represents the coefficient of direction, i = 1,
, 8; j represents a coefficient in the vertical direction, and j = 1, ... 8), the target complexity calculation means 3b uses these conversion coefficients Coeff (f-1, h, s, n, i, j) is quantized with the current quantization step parameter Q (f, h, s), and the generated code amount Xs (f, h, s
s) is estimated. Transformation coefficient Coeff (f-1, h, s, n, i, j) (n = 1,
, N; i = 1, ..., 8; j = 1, ... 8) is the transform coefficient value before quantization, so if the quantization step parameter Q (f, h, s) is given, the code amount Xs You can obtain (f, h, s) accurately. Since this code amount Xs (f, h, s) is considered to be an estimated value of the generated code amount of the s-th sub-picture of the h-th slice of the f-th frame, this estimated value is used as the target complexity Y (f, h, s). ) Is output.

However, as in the first embodiment, whether the s-th sub-picture of the h-th slice of the f-th picture and the s-th sub-picture of the h-th slice of the f-1st picture are each intra-picture coded. Since it is necessary to change the value of the estimated code amount Xs (f, h, s) depending on whether it is inter-picture coding,
Type identification signal type (f, h,
The value of the estimated code amount Xs (f, h, s) is corrected by (s). Therefore, the target complexity Y (f, h, s) is defined by the following equation using the function F2. Y (f, h, s) = F2 ((Coeff (f-1, h, s, n, i, j), 1 ≦ n ≦ N, 1 ≦
i, j ≦ 8}, Q (f, h, s), type (f, h, s)))

The operations from the subsequent target bit amount calculating means 4b to the adaptive quantizing means 7b are the same as in the first embodiment. In the above embodiment, when the target complexity Y (f, h, s) is actually obtained, the quantization step parameter Q (f, h, s) is not yet determined, so Q (f, h , s) which is considered to be the closest to Q (f-1, L, s) is used instead of Q (f, h, s).

Example 3. The third embodiment will be described below. This embodiment differs from the first and second embodiments in the process of calculating the target complexity.

FIG. 7 is a schematic block diagram showing a quantization control system in a video signal coding system according to an embodiment of the present invention. In the figure, the conversion coefficient value 401 before quantization in the past screen input from the input terminal 1n
Is given to the input of the coefficient representative value calculating means 8a. The two outputs 402 and 403 of the coefficient representative value calculating means 8a are given to the first and second inputs of the target complexity calculating means 3c. Further, the quantization step parameter 404 in the current screen input from the input terminal 1o is the third input of the target complexity calculation means 3c, and the type identification signal 405 input from the input terminal 1p is the target complexity calculation. Provided to the fourth input of the means 3c. The output 406 of the target complexity calculating means 3c is given to the first input of the target bit amount calculating means 4c, and the buffer remaining capacity 407 inputted from the input terminal 1q is given to the second input of the target bit amount calculating means 4c. To be Target bit amount 408 output from the target bit amount calculating means 4c
Is given to the first input of the virtual buffer remaining amount calculation means 5c, and the generated code amount 409 inputted from the input terminal 1r is given to the second input of the virtual buffer remaining amount calculation means 5c. The output 410 of the virtual buffer remaining amount calculation means 5c is given to the input of the quantization step parameter calculation means 6c. The reference quantization step parameter 411 which is the output of the quantization step parameter calculation means 6c is the adaptive quantization means 7
given to the first input of c. The second input of the adaptive quantizing means 7c is the adaptive quantizing coefficient 41 from the input terminal 1s.
2 is given. The quantization step parameter 413 for each macroblock, which is the output of the adaptive quantization unit 7c, is
It is output from the output terminal 2c.

The operation will be described below. In the second embodiment, in the process of calculating the target complexity, the transform coefficient Coeff (f-1, of the s-th sub-picture of the h-th slice of the (f-1) -th picture is calculated.
It is necessary to hold all h, s, n, i, j) (1≤n≤N, 1≤i, j≤8). The third embodiment differs from the second embodiment in that only the representative values of these transform coefficients are used in the process of calculating the target complexity.

First, the coefficient representative value calculating means 8a uses the pre-quantization transform coefficient Coeff (f-1, h, h) of the s-th sub-picture of the h-th slice of the (f-1) -th picture input from the input terminal 1n.
s, n, i, j) (1 ≦ n ≦ N, 1 ≦ i, j ≦ 8) average value ave (f-1, h,
s) and variance var (f-1, h, s). The target complexity calculation means 3c calculates the average value ave (f-1, h, s) and the variance var (f-1, h, s).
s) and the quantization step parameter Q (f, h, s) and the type identification signal type (f, h, s) in the sth subpicture of the hth slice of the fth frame, h
Target complexity Y (f, h,
s) is defined as follows. Y (f, h, s) = F3 (ave (f-1, h, s), var (f-1, h, s), Q (f, h, s), type (f, h, s) ) Here, the function F3 is determined based on the quantitative property as in the second embodiment. Also, the target complexity Y (f, h, s) is actually
Q (f, h, s) is undecided when calculating
Instead of Q (f-1, L,
s) etc. are used.

Although the mean and the variance are used as the coefficient representative values in the above-mentioned third embodiment, the representative values of the coefficients are not limited to these values, and values representing the distribution of the conversion coefficients such as median and standard deviation are used. I wish I had it.

Example 4. The fourth embodiment will be described below. This embodiment differs from the first and second embodiments in the process of calculating the target complexity.

FIG. 8 is a schematic block diagram showing a quantization control system in a video signal coding system according to an embodiment of the present invention. In the figure, the transform coefficient value 501 before quantization in the past screen input from the input terminal 1t
Is given to the input of the coefficient representative value calculating means 8b. The two outputs 502 and 503 of the coefficient representative value calculating means 8b are given to the first and second inputs of the target complexity calculating means 3d. In addition, the quantization step parameter 504 in the current screen input from the input terminal 1u is the third input of the target complexity calculation means 3d, and the type identification signal 505 input from the input terminal 1v is the target complexity calculation. Provided to the fourth input of the means 3d. The output 506 of the target complexity calculation unit 3d is given to the first input of the target bit amount calculation unit 4d, and the buffer remaining amount 507 inputted from the input terminal 1w is given to the second input of the target bit amount calculation unit 4d. To be Target bit amount 508 output from the target bit amount calculation means 4d
Is given to the first input of the virtual buffer remaining amount calculation means 5d, and the generated code amount 509 inputted from the input terminal 1x is given to the second input of the virtual buffer remaining amount calculation means 5d. The output 510 of the virtual buffer remaining amount calculation means 5d is given to the input of the quantization step parameter calculation means 6d. The reference quantization step parameter 511 which is the output of the quantization step parameter calculation means 6d is the adaptive quantization means 7
applied to the first input of d. The second input of the adaptive quantizing means 7d is the adaptive quantizing coefficient 51 from the input terminal 1y.
2 is given. The quantization step parameter 513 for each macroblock, which is the output of the adaptive quantization unit 7d, is
It is output from the output terminal 2d.

The operation will be described below. In the second embodiment, in the process of calculating the target complexity, the transform coefficient Coeff (f-1, of the s-th sub-picture of the h-th slice of the (f-1) -th picture is calculated.
It is necessary to hold all h, s, n, i, j) (1≤n≤N, 1≤i, j≤8). The fourth embodiment is different from the second embodiment in that these conversion coefficients are classified into classes and only representative values of the values indicating the classes are used.

First, the coefficient representative value calculating means 8b receives the pre-quantization transform coefficient Coeff (f-1, h, h) of the s-th sub-picture of the h-th slice of the (f-1) -th picture input from the input terminal 1t.
s, n, i, j) (1≤n≤N, 1≤i, j≤8) is classified into classes.
For example, when the quantization step parameter Q can take 31 different values, each of the transform coefficients Coeff (f-1, h, s, n, i, j) is quantized with which quantization step parameter. When the quantized value becomes 0, it can be classified into 32 classes. Each conversion coefficient Coeff (f-1, h, s, n, i,
The class to which j) belongs is represented by Coeff_cls (f-1, h, s, n, i, j). For example, if the conversion coefficient Coeff (f-1, h, s, n, i, j) is a very small value and Q = 1 and the quantized value is already 0, Coeff_cls (f-1, h, s, n, i, j) = 1, and conversely, the conversion coefficient Coeff (f-1, h, s, n, i, j) is a very large value and the coarsest quantization step parameter Q = Even if it is 31, if the quantized value does not become 0, Coeff_cls (f-1, h, s, n,
i, j) = 32. Further, the coefficient representative value calculating means 8b
Is Coeff_cls (f-1, h, s, n, i, j) (1 ≦ n ≦ N, 1 ≦ in the s-th sub-picture of the h-th slice of the f-1 picture.
i, j ≦ 8) mean ave_cls (f-1, h, s) and variance var_cls (f-
1, h, s) is calculated.

The target complexity calculating means 3d uses the mean value ave_cls (f-1, h, s) and the variance var_cls (f-1, h, s), and the s-th sub-th slice of the h-th slice of the f-th frame. Using the quantization step parameter Q (f, h, s) and the type identification signal type (f, h, s) in the picture, the target complexity Y (f, f, f) of the s-th sub-picture of the h-th slice of the f-th frame is used. h, s) is defined as follows. Y (f, h, s) = F4 (ave_cls (f-1, h, s), var_cls (f-1, h, s), Q (f, h, s), type (f, h, s) ) Here, the function F4 is determined based on the quantitative property as in the third embodiment. Also, the target complexity Y (f, h, s) is actually
Q (f, h, s) is undecided when calculating
Instead of Q (f-1, L,
s) etc. are used.

Although the mean and variance are used as the representative value representing the class to which each transform coefficient belongs in the fourth embodiment, the representative value is not limited to this, and the median, standard deviation, or It may be the number of times a coefficient belonging to a class is generated.

[0070]

As described above, according to the first aspect of the invention, the complexity of the coded image is calculated by using the number of non-zero transform coefficient values in the past screen and the quantization step parameter in the past screen. Alternatively, by estimating the amount of generated code, it is possible to obtain a video signal coding system having a quantization control system suitable for performing periodic refresh with divided screens and a quantization control system based on quantitative properties. .

According to the second aspect of the present invention, the complexity of the encoded image or the generated code amount is calculated by using the transform coefficient value before quantization in the past screen and the quantization step parameter in the current screen. By the estimation, there is an effect of obtaining a video signal coding system equipped with a quantization control system suitable for performing periodic refresh with divided screens and a quantization control system based on quantitative properties.

According to the third aspect of the invention, the complexity of the coded image is calculated by using the representative value indicating the distribution of the transform coefficient values before quantization on the past screen and the quantization step parameter on the current screen. By estimating the degree or the amount of generated code, there is an effect of obtaining a video signal coding system equipped with a quantization control system suitable for performing periodic refresh with divided screens and a quantization control system based on quantitative properties. .

Further, according to the invention of claim 4, each transform coefficient before quantization is divided into classes according to its size, and the class to which each transform coefficient in the past screen belongs and the quantization step parameter of the current screen are classified. , The quantization control method suitable for the case of performing periodic refresh by dividing the screen by estimating the complexity of the encoded image or the generated code amount, and the quantization control method based on the quantitative property are provided. There is an effect of obtaining a video signal coding system.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a quantization control method in a video signal encoding method according to an embodiment of the invention of claim 1.

FIG. 2 is a diagram showing a main hierarchical structure of a video signal according to the first embodiment.

FIG. 3 is a diagram showing a schematic relationship between the number of non-zero transform coefficients and a generated code amount for explaining the quantization control method in the first embodiment.

FIG. 4 is a diagram showing a schematic relationship between a quantization step parameter and the number of non-zero transform coefficients for explaining the quantization control method in the first embodiment.

FIG. 5 is a flowchart showing a process of calculating a target complexity referred to in the quantization control method according to the first embodiment.

FIG. 6 is a schematic block diagram showing a quantization control method in a video signal encoding method according to an embodiment of the invention of claim 2;

FIG. 7 is a schematic block diagram showing a quantization control method in a video signal encoding method according to an embodiment of the invention of claim 3;

FIG. 8 is a schematic block diagram showing a quantization control system in a video signal coding system according to an embodiment of the invention of claim 4;

FIG. 9 is a schematic block diagram showing a conventional video signal encoding system.

FIG. 10 is a schematic block diagram showing an example of a quantization control method in a conventional video signal coding method.

FIG. 11 is a conceptual diagram of a refresh method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 input terminal 2 output terminal 3 target complexity calculation means 4 target bit amount calculation means 5 virtual buffer remaining amount calculation means 6 quantization step parameter calculation means 7 adaptive quantization means 8 coefficient representative value calculation means 9 subtracter 10 DCT circuit 11 Quantization 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

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[Procedure amendment]

[Submission date] September 6, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

FIG. 10 shows, for example, ISO-IEC / JTC1 / SC29 / WG11.
FIG. 11 is a schematic block diagram showing an example of a quantization control method in the conventional video signal coding method shown in MPEG 92 / N0245 Test Model 2. In the figure, the first generated code amount 1201 input from the input terminal 101d is given to the first input of the complexity calculation circuit 20a, and the first average quantization step parameter 12 input from the input terminal 101e.
02 is given to the second input of the complexity calculation circuit 20a. The first double is the output of the complexity calculation circuit 20a Zatsudo 1
203 is supplied to the first input of the target bit amount calculation circuit 4e. Second input from the input terminal 101f
Of the generated code amount 1204 is the first code of the complexity calculation circuit 20b.
And the second average quantization step parameter 1205 input from the input terminal 101g is input to the second input of the complexity calculation 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.
Third generated code amount 12 input from input terminal 101h
07 is given to the 1st input of the complexity calculation circuit 20c, and the 3rd average quantization step parameter 1208 inputted from the input terminal 101i is given to the 2nd input of the complexity calculation circuit 20c. 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.

Front page continuation (72) Inventor Takahiro Nakai 1 Baba-Zou, Nagaokakyo-shi Video System Development Laboratory, Mitsubishi Electric Corporation

Claims (4)

[Claims] 1. A video signal coding system for coding a video signal, the video signal coding system comprising transform coding as a constituent element, wherein the index for estimating the complexity of a coded image or the generated code amount. As a video signal coding method, the number of non-zero transform coefficient values in the past screen and the quantization step parameter in the past screen are used as 2. A video signal coding system for coding a video signal, the video signal coding system comprising conversion coding as a constituent element, wherein the index for estimating the complexity of a coded image or the generated code amount. As a video signal coding method, the transform coefficient value before quantization in the past screen and the quantization step parameter in the current screen are used as. 3. A video signal coding system for coding a video signal, the video signal coding system comprising transform coding as a constituent element, wherein the index for estimating the complexity of a coded image or the generated code amount. As a video signal encoding method, a representative value indicating a distribution of transform coefficient values before quantization on a past screen and a quantization step parameter on the current screen are used as. 4. A video signal coding system for coding a video signal, comprising a transform coding as a constituent element, wherein each transform coefficient before quantization is classified according to its size. And a quantization step parameter of the current screen and a class to which each transform coefficient in the past screen belongs as an index for estimating the complexity of the coded image or the generated code amount. Encoding method.