JP2004297696A - Video signal encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the quality of a video reproduced by coded data by flexibly controlling generation of codes depending on situations when encoding video signals. <P>SOLUTION: A video signal encoder 1 is provided with an encoding unit 10 generating the coded data by an encoding operation including a quantization operation in which the video signals are quantized in processing unit blocks, a buffer 30 for temporarily storing the coded data and a code amount control unit 40 for controlling a quantization parameter used for the quantizing operation in the encoding unit 10. The code amount control unit 40 determines the quantization parameter QPn+1 used for the next quantization operation based on an accumulated code amount BF in the buffer 30 using a judgement standard indicating a relation between the accumulated code amount BF in the buffer 30 and an increase/decrease value R of the quantization parameter. A judgement unit 43 in the quantization amount control unit 40 sets the judgement standard variable in accordance with the present quantization parameter QPn. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for encoding a video signal, and more particularly to a video signal encoding apparatus that controls a quantization parameter used for encoding processing to adjust a generated code amount.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a video signal encoding apparatus that encodes a video signal, the amount of code of a video signal obtained by the encoding process (hereinafter, referred to as generated code amount) is controlled by controlling a quantization parameter used in the encoding process. Techniques for adjusting the temperature are known. This type of video signal encoding apparatus controls an encoding unit that encodes the video signal, a buffer that stores the encoded video signal and outputs the encoded video signal for each predetermined capacity, and a quantization parameter of the encoding unit. And a control unit that performs the control.
[0003]
A video signal representing a moving image including a plurality of frames is input to the encoding unit. The encoding unit divides each frame into a plurality of processing unit blocks, encodes a video signal for each processing unit block, and generates encoded data. The encoding process includes a quantization process for quantizing a video signal using a quantization parameter.
[0004]
The encoding unit performs intra-frame encoding on a plurality of frames at predetermined intervals, and performs inter-frame encoding between two frames to be intra-frame encoded. Here, the intra-frame encoding is encoding using only a target frame. Further, the inter-frame coding is coding using a mutual relationship between frames. Generally, the code amount of code data generated by intra-frame coding is larger than that of code data generated by inter-frame coding.
[0005]
The buffer sequentially accumulates the encoded data and outputs the accumulated encoded data at a predetermined timing and a predetermined bit rate. Here, the capacity that can be output from the buffer at one time is determined according to the above-mentioned bit rate. Therefore, when the code amount of the video signal accumulated in the buffer is smaller than the data capacity that can be output at one time, all the signals in the buffer are output by one output. On the other hand, when the code amount stored in the buffer is larger than the data capacity that can be output at one time, not all data can be output, and some data remains after output. The remaining data is output at the next output timing.
[0006]
Here, in the encoding process of the video signal, even when the processing unit blocks having the same number of pixels are encoded, the amount of code generated by the encoding process differs depending on the content of the signal. On the other hand, the code amount generated by the encoding process can be changed by increasing or decreasing the quantization parameter used for the encoding process. Therefore, the control unit adjusts the code amount stored in the buffer by increasing or decreasing the quantization parameter.
[0007]
For this purpose, during the encoding process, the control unit calculates a difference between the code amount stored in the buffer (hereinafter, referred to as a code storage amount) and a target code amount at that time, and performs encoding in accordance with the difference. The quantization parameter used in the section is increased or decreased. Specifically, when the code storage amount in the buffer is larger than the target code amount, the control unit decreases the quantization parameter to increase the generated code amount, and conversely, the code storage amount becomes larger than the target code amount. Is smaller, the quantization parameter is increased to suppress the generated code amount.
[0008]
The video signal encoding device as described above is described in, for example, Patent Document 1.
[0009]
[Patent Document 1]
JP 2001-169281 A (Pages 7-11, FIG. 5)
[0010]
[Problems to be solved by the invention]
However, in the conventional video signal encoding device, when the code storage amount of the buffer is lower than the target code amount, even if the quantization parameter is reduced, it takes time to increase the generated code amount. I will. As a result, even in a situation where there is a margin in the free space of the buffer with respect to the target code amount and the generated code amount may be increased, the image quality cannot be improved by effectively utilizing the spare space amount. Occurs.
[0011]
Further, as described above, the code amount generated by intra-frame coding is larger than the code amount generated by inter-frame coding. The amount of data that can be output from the buffer in one output is determined as described above. Therefore, at the time of intra-frame encoding, it is desirable to reduce the code accumulation amount in the buffer as much as possible. For that purpose, it is necessary to suppress the amount of generated codes before the intra-frame encoding. However, if the generated code amount is suppressed, the image quality is reduced accordingly.
[0012]
An object of the present invention is to improve the image quality of an encoded video signal by flexibly controlling the amount of generated code when encoding the video signal according to the situation.
[0013]
[Means for Solving the Problems]
A video signal encoding apparatus according to the present invention includes: an encoding unit that encodes a video signal by quantizing the video signal using a quantization parameter for each predetermined processing unit; and a video signal encoded by the encoding unit. And a quantization parameter increase / decrease criterion representing a relationship between the capacity of the data accumulated in the buffer and the increase / decrease value of the quantization parameter, and quantizing based on the capacity of the data accumulated in the buffer. A quantization parameter determining means for determining a parameter, and a quantization parameter for determining a quantization parameter to be used for data of the processing unit after the processing unit in accordance with the quantization parameter used for the data of the processing unit. Reference changing means for variably setting the quantization parameter increase / decrease reference.
[0014]
According to this configuration, based on the quantization parameter used for the encoding process of the data of a certain processing unit, the increase / decrease standard of the quantization parameter used for the data of the subsequent processing unit is set, so that an appropriate quantization parameter is set. It is possible to flexibly control the amount of code generated in the encoding process. Note that, in the above-described video signal encoding device, each of the above units does not have to function for data of all processing units, and as described later, for data of a specific processing unit, Other means may be configured to function.
[0015]
In the video signal encoding apparatus, the reference changing unit may be configured such that when the quantization parameter used for the data of the processing unit is higher than a predetermined threshold, the quantization parameter is lower than the threshold. A quantization parameter increase / decrease criterion in which the quantization parameter tends to decrease more strongly is set.
[0016]
With this configuration, when the quantization parameter is set to a high value, the generated code amount is suppressed, and when there is a margin in the free space of the buffer and the generated code amount may be increased, the quantization parameter may be increased. Since it can be reduced, it is possible to improve the image quality of the video reproduced by the code data by effectively utilizing the free space of the buffer.
[0017]
In the video signal encoding apparatus, the quantization parameter determination unit may include a quantization parameter calculation unit that calculates a quantization parameter according to the quantization parameter increase / decrease criterion, and the quantization parameter calculation unit may calculate the quantization parameter. Code amount prediction means for predicting the generated code amount when the data of the processing unit is quantized using a quantization parameter; and the quantization parameter based on the generated code amount predicted by the code amount prediction means. An adoption determining means for determining whether or not to employ the quantization parameter calculated by the calculating means, wherein the quantization parameter determined to be employed by the adoption determining means is used by the quantization means used in the encoding means. Is determined as a parameter.
[0018]
According to this configuration, since the quantization parameter is determined after the adoption determination unit determines the adoption based on the prediction of the generated code amount, an excessive change in the generated code amount due to an increase or decrease in the quantization parameter is prevented. be able to.
[0019]
In the video signal encoding apparatus, the encoding unit encodes a video signal representing a moving image including a plurality of frames by intra-frame encoding and inter-frame encoding, and the reference changing unit includes an inter-frame encoding unit. For the data of the processing unit to be converted, the quantization parameter increase / decrease criterion is set according to the number of times of encoding until the next intra-frame encoding.
[0020]
With this configuration, the quantization parameter increase / decrease criterion is set for the data of the processing unit to be inter-coded according to the number of times of encoding until the next intra-frame encoding. When encoding moving images, efficient encoding processing can be realized by effectively utilizing the free space of the buffer. In addition, as the number of times of encoding until the next intra-frame encoding, the number of frames until the next intra-frame encoding may be counted, or the number of processing units to be processed until the next intra-frame encoding is performed. It may be counted.
[0021]
A video signal encoding apparatus according to another aspect of the present invention quantizes a video signal representing a moving image composed of a plurality of frames using a quantization parameter for each predetermined processing unit, so that the plurality of frames are included in a frame. Coding means for coding by coding and inter-frame coding; a buffer for storing the video signal coded by the coding means; a capacity of data stored in the buffer and an increase / decrease value of a quantization parameter And a quantization parameter determining unit that determines a quantization parameter based on a capacity of data stored in the buffer, using a quantization parameter increase / decrease criterion representing a relationship with the encoding unit. For data of a processing unit to be processed, the quantization parameter increase / decrease criterion is variably set according to the number of times of encoding until the next intra-frame encoding. And a reference change means.
[0022]
With this configuration, the quantization parameter increase / decrease criterion is set for the data of the processing unit to be inter-coded according to the number of times of encoding until the next intra-frame encoding. When encoding moving images, efficient encoding processing can be realized by effectively utilizing the free space of the buffer.
[0023]
Further, in the video signal encoding apparatus, the reference changing unit has a stronger tendency to increase the quantization parameter for data of a processing unit immediately before the intra-frame coding than for data of another processing unit. Set the quantization parameter increase / decrease criterion.
[0024]
With this configuration, immediately before the intra-frame encoding, a quantization parameter increase / decrease criterion in which the quantization parameter increase tendency is stronger than that of the data of other processing units is set, so that the quantization is rapidly performed immediately before the intra-frame encoding. By increasing the parameter, it is possible to reduce the generated code amount. As a result, a sufficient code amount can be generated for an intra-coded frame, and a generated code amount can be generated for a larger number of processing units for an inter-coded frame. Is possible, and the image quality of the video reproduced by the code data can be improved.
[0025]
A video signal encoding apparatus according to still another aspect of the present invention includes encoding means for encoding the video signal by quantizing the video signal using a quantization parameter for each predetermined processing unit; A buffer for storing the video signal encoded by the quantization means, and a quantization parameter increase / decrease criterion representing a relationship between a capacity of the data accumulated in the buffer and an increase / decrease value of the quantization parameter. Quantization parameter determining means for determining a quantization parameter based on the capacity of the processed data, and a quantization parameter increase / decrease criterion for determining a quantization parameter to be used for data of a processing unit after the processing unit. Criterion changing means for setting the criterion.
[0026]
According to this configuration, since the increase / decrease criterion of the quantization parameter is variably set, the quality of the video reproduced by the code data can be improved by flexibly controlling the generated code amount according to the situation.
[0027]
Further, the above-mentioned problems can be solved by a video signal encoding method having the features of the present invention, a program for causing a computer to execute the video signal encoding method, and a recording medium storing the program.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0029]
(First Embodiment)
FIG. 1 and FIG. 2 are block diagrams showing the configuration of the video signal encoding device 1 according to the first embodiment. The video signal encoding device 1 according to the first embodiment is generated by an encoding unit 10 that encodes and compresses a video signal, a buffer 30 that temporarily stores an encoded video signal, and an encoding unit 10. A code amount control unit 40 for controlling the code amount is provided. FIG. 1 illustrates the configuration of the code amount control unit 40 in detail, and FIG. 2 illustrates the configuration of the encoding unit 10 in detail. Hereinafter, first, the overall configuration of the video signal encoding device 1 and the configuration of the encoding unit 10 will be described with reference to FIG. 2, and then the configuration of the code amount control unit 40 will be described with reference to FIG.
[0030]
FIG. 2 is a block diagram illustrating the configuration of the video signal encoding device 1 in which the configuration of the encoding unit 10 is described in detail as described above. As shown in FIG. 2, the video signal encoding device 1 includes an encoding unit 10, a buffer 30, and a code amount control unit 40.
[0031]
The encoding unit 10 includes a division unit 11, a subtraction unit 12, a DCT unit 13, a quantization unit 14, and a VLC unit 15. The dividing unit 11 captures a video signal indicating a moving image obtained by an image sensor or the like. The video signal is composed of a plurality of frames. For example, 30 frames of images are input to the dividing unit 11 per second. The division unit 11 divides the input image of each frame into processing unit blocks, and generates image data indicating an image for each processing unit block. The dividing unit 11 divides, for example, one frame image into three equal parts in the horizontal direction and five equal parts in the vertical direction, and divides the image into 15 processing unit blocks having the same size. Note that this processing unit block corresponds to the processing unit of the present invention, but the processing unit of the present invention may be larger or smaller than the 15-divided block as described above, and one frame is a processing unit. May be done.
[0032]
The processing unit block output from the division unit 11 is input to the subtraction unit 12 when the block is inter-coded, and is input to the DCT unit 13 when the block is intra-coded. .
[0033]
The subtraction unit 12 captures image data of a processing unit block to be subjected to inter-frame encoding. Then, the subtraction unit 12 calculates prediction error data by subtracting prediction reference image data described later from the image data of the processing unit block. The DCT unit 13 performs a two-dimensional discrete cosine transform on the image data of the processing unit block output from the division unit 11 and the prediction error data output from the subtraction unit 12.
[0034]
The quantization unit 14 quantizes the image data and the prediction error data of the processing unit block subjected to the two-dimensional discrete cosine transform by the DCT unit 13. Here, the quantization unit 14 performs a quantization process using the quantization parameter. The quantization parameter is a parameter indicating the quantization width, that is, the roughness of the quantization. When the quantization parameter is large, the capacity of the code data, that is, the generated code amount decreases, and conversely, when the quantization parameter is small, the generated code amount increases. The VLC unit 15 performs variable-length conversion on the quantized image data and prediction error data of the processing unit block to generate code data. The code data is output to the buffer 30.
[0035]
The encoding unit 10 further includes an inverse quantization unit 16, an inverse DCT unit 17, an addition unit 18, a memory unit 19, a motion detection unit 20, a motion compensation unit 21, and a motion prediction unit 22. The inverse quantization unit 16 performs inverse quantization on the image data and the prediction error data quantized by the quantization unit 14. The inverse DCT unit 17 performs two-dimensional inverse discrete cosine transform on the data of the processing unit block inversely quantized by the inverse quantization unit 16 to generate prediction error data or reconstructed image data. The adder 18 adds the prediction error data created by the inverse DCT unit 17 and the prediction reference image data obtained by the motion compensation unit 21 to generate reconstructed image data. The memory unit 19 stores the reconstructed image data generated by the adder 18 or the inverse DCT unit 17.
[0036]
The motion detecting section 20 takes in the reconstructed image data stored in the memory section 19. The motion detection unit 20 detects motion vector data by comparing reconstructed image data from image data of an uncompressed processing unit block input from the division unit 11. The motion compensator 21 extracts predicted reference image data from the reconstructed image data based on the motion vector data detected by the motion detector 20. This predicted reference image data is used in the subtraction unit 12 as described above. That is, the subtraction unit 12 calculates prediction error data by subtracting the prediction reference image data generated by the motion compensation unit 21 from the image data of the uncompressed processing unit block. The motion prediction unit 22 calculates predicted motion vector data, and subtracts predicted motion vector data from the motion vector data detected by the motion detection unit 20 to calculate motion vector difference data.
[0037]
With the above configuration, the image data of the frame to be intra-coded is divided into the processing unit blocks divided by the division unit 11, and the processing is performed by the DCT unit 13, the quantization unit 14, and the VLC unit 15. , Are output to the buffer 30 as code data. Further, image data of a frame to be subjected to inter-frame encoding is divided into processing unit blocks by the division unit 11 and input to the subtraction unit 12. The subtraction unit 12 calculates prediction error data by subtracting the prediction reference image data from the image data of the processing unit block to be coded between frames. Then, the prediction error data is output to the buffer 30 as code data through the processing in the DCT unit 13, the quantization unit 14, and the VLC unit 15. The prediction error data is used to generate predicted reference image data after being quantized by the quantization unit 14.
[0038]
In the encoding process of the video signal as described above, the quantization parameter used in the quantization unit 14 is controlled by the code amount control unit 40. By controlling the quantization parameter, the code amount of the code data output from the coding unit 10 is controlled. The code amount control unit 40 controls the quantization parameter according to the use state of the buffer 30 so that the code storage amount of the buffer 30 becomes a target value.
[0039]
FIG. 1 is a block diagram of the video signal encoding device 1 showing the configuration of the code amount control unit 40. The code amount control unit 40 includes a target code amount calculation unit 41, a difference calculation unit 42, a determination unit 43, a quantization parameter calculation unit 44, a code amount prediction unit 45, and a quantization parameter determination unit 46.
[0040]
Each time the encoding unit 10 encodes the image data of the processing unit block, the target code amount calculation unit 41 calculates a target code amount TB that should be stored in the buffer 30 at that time. The target code amount calculation unit 41 calculates the target code amount TB by using Expression (1) using the frame rate FR and the bit rate BR.
(Equation 1)
Target code amount TB = (bit rate BR / frame rate FR) × (block number BN / total number of blocks TN) (1)
[0041]
Here, the block number BN indicates the number of processing unit blocks for which compression processing has been completed in one frame, and the total block number TN indicates the total number of processing unit blocks included in one frame. That is, the target code amount TB is equal to the total block size of one frame with respect to the code amount (bit rate BR / frame rate FR) that should be stored in the buffer 30 when all the processing unit blocks for one frame are processed. This is a value obtained by multiplying the number by the ratio up to the block after the compression processing (block number BN / total number of blocks TN).
[0042]
The difference calculator 42 calculates a difference N between the code accumulation amount BF of the buffer 30 and the target code amount TB. The determination unit 43 stores a determination criterion for an increase / decrease value that defines the relationship between the code accumulation amount BF of the buffer 30 and the increase / decrease value R of the quantization parameter for each block number BN. The criterion is that when the difference N between the code accumulation amount BF and the target code amount TB is plus, the increase / decrease value R is zero or plus, and when the difference N is minus, the increase / decrease value R is zero or minus. Thus, the relationship between the difference N and the increase / decrease value R is defined. In this determination criterion, the larger or smaller the difference N, the larger the increase / decrease value R of the quantization parameter.
[0043]
According to this determination criterion, the determination unit 43 increases the quantization parameter when the code storage amount of the buffer 30 for each block number BN is larger than the target code amount TB corresponding to the block number BN. As a result, the generated code amount decreases, and the code storage amount BF approaches the target code amount TB. On the other hand, when the code storage amount is smaller than the target code amount, the determination unit 43 reduces the quantization parameter according to the determination criterion. As a result, the generated code amount increases, and the code storage amount BF approaches the target code amount TB.
[0044]
As described above, the determination unit 43 controls the code storage amount BF to approach the target code amount TB by increasing or decreasing the quantization parameter based on the code storage amount BF of the buffer 30. However, even if the difference N between the code storage amount BF and the target code amount TB is the same and the same increase / decrease value R is added to the quantization parameter, the quantization code has already been set to a large value and the generated code amount is small. The speed at which the code storage amount BF approaches the target code amount TB, that is, the code storage amount BF is equal to the target code amount, depending on whether the code amount is increasing or the quantization parameter is set to be small and the generated code amount is decreasing. The number of processing unit blocks required to approach TB differs. For example, when the quantization parameter is already set to a large value and the generated code amount is suppressed to a small value, if the code storage amount BF becomes less than the target code amount TB, the generated code amount is immediately increased and the target code amount is increased. It is desired to reach the code amount TB. Therefore, in order to make the code storage amount BF reach the target code amount TB earlier, not only the difference N between the code storage amount BF and the target code amount TB, but also a state where the generated code amount is increasing or decreasing. It is desirable to control the quantization parameter in consideration of the above.
[0045]
Therefore, the determination unit 43 stores a plurality of determination criteria as described above, in which the magnitude of the decreasing tendency or the increasing tendency of the quantization parameter is different from each other. In the present embodiment, the determination unit 43 stores two types of determination criteria. Then, the determining unit 43 determines which of these two criteria is to be used for each processing of the processing unit block according to whether the generated code amount is in a state of increasing or a state of decreasing. The increase / decrease value R of the quantization parameter is calculated according to the determined criterion. This criterion corresponds to the quantization parameter increase / decrease criterion of the present invention. In the following, a plurality of criteria stored in the determination unit 43 will be described first, and then a determination of which one of the criteria will be used will be described.
[0046]
FIG. 3 and FIG. 4 are graphs showing the determination criteria stored in the determination unit 43. FIGS. 3 and 4 show graphs in which the horizontal axis is the block number BN of the processing unit block that has been subjected to the encoding processing by the encoding unit 10 and the vertical axis is the code accumulation amount BF of the buffer 30. ing. These graphs show the target code amount TB. As described above, the target code amount TB is an amount defined by the equation (1). Therefore, as shown in FIGS. 3 and 4, the larger the coded processing unit block, that is, the more the coding process is performed. The target code amount TB also increases as it proceeds. In the graphs of FIGS. 3 and 4, each of the increase / decrease values (−2 to +2) is divided into a plurality of regions by a line parallel to a straight line indicating the transition of the target code amount TB.
[0047]
When comparing FIG. 3 with FIG. 4, the determination criterion shown in FIG. 3 is set such that the area of each increase / decrease value is set higher than the determination criterion of FIG. Is a strong determination criterion. Conversely, the criterion shown in FIG. 4 has a stronger tendency to increase the quantization parameter than the criterion shown in FIG. That is, the area of each increase / decrease value of the criterion in FIG. 3 is located at a position where the code accumulation amount is larger than those of the criterion in FIG. Accordingly, even if the code accumulation amount at the time when a certain processing unit block is processed is the same, the case where the determination criterion of FIG. 3 is used and the case where the determination criterion of FIG. In some cases, the amount of increase in the quantization parameter is smaller (or the amount of decrease is larger) when is used.
[0048]
For example, in the determination criterion in FIG. 3, the area of the increase / decrease value of 0 and the area of the increase / decrease value of -1 are separated by a straight line indicating the transition of the target code amount TB, and the code accumulation amount BF of the buffer 30 is determined by the target code amount TB Immediately below, the increase / decrease value R immediately becomes negative. On the other hand, according to the determination criterion in FIG. 4, the area of the increase / decrease value 0 includes a straight line indicating the transition of the target code amount TB, and even if the code accumulation amount BF of the buffer 30 falls below the target code amount TB, the difference When N is small, the increase / decrease value R becomes zero. In addition, according to the criterion in FIG. 3, the increase / decrease value R of the quantization parameter does not become positive unless the code storage amount BF significantly exceeds the target code amount TB. When the accumulated amount BF exceeds the target code amount TB, the region reaches +1 with a difference smaller than the criterion in FIG.
[0049]
The criteria shown in FIGS. 3 and 4 can be expressed by mathematical expressions. That is, the area corresponding to each increase / decrease value R is represented by the following determination formula.
(Equation 2)
Area of increase / decrease value + 2: BF−TB> PB × n1 (2)
[Equation 3]
Area of increase / decrease value +1: PB × n1 ≧ BF−TB> PB × n2 (3)
(Equation 4)
Area of increase / decrease value 0: PB × n2 ≧ BF−TB> PB × n3 (4)
(Equation 5)
Area of increase / decrease value −1: PB × n3 ≧ BF−TB> PB × n4 (5)
(Equation 6)
Area of increase / decrease value-2: PB × n4 ≧ BF-TB (6)
Here, n1 to n4 are coefficients for determining the boundary of the increase / decrease value, and satisfy n4 <n3 ≦ 0 <n2 <n1. As n1 to n4 are larger, the area of each increase / decrease value is set to a position where the code accumulation amount is higher. In equations (2) to (6), BF is the code storage amount, TB is the target code amount, and PB is the target generated code amount for one processing unit block, which is a value obtained by expression (7). is there.
(Equation 7)
Target generated code amount PB = (bit rate BR / frame rate FR) × (number of pixels in one processing unit block / number of pixels in one frame) (7)
[0050]
Each of n1 to n4 in equations (2) to (6) corresponding to FIG. 3 is larger than each of n1 to n4 in equations (2) to (6) corresponding to FIG. This means that the criterion equation corresponding to FIG. 3 has a stronger tendency to decrease the quantization parameter than the criterion equation corresponding to FIG.
[0051]
The determination unit 43 stores, as a determination criterion, a table including information on combinations of the above equations (2) to (6) and values of n1 to n4. Tables respectively corresponding to FIGS. 3 and 4 are, for example, the following Table1 and Table2.
Table1:
n1 = 13
n2 = 10
n3 = -2
n4 = -3
Table2:
n1 = 7
n2 = 5
n3 = -3
n4 = -5
[0052]
As described above, each time the encoding unit 10 processes one processing unit block, the determination unit 43 determines which of the above determination criteria is to be adopted. In the present embodiment, in order to determine which criterion is to be used, the determination unit 43 determines which quantization criterion is to be used by the quantization parameter calculation unit 44 at the time of adopting the criterion (hereinafter, the following) Current quantization parameter QPn). At this time, the determination unit 43 functions as a reference changing unit of the present invention.
[0053]
As described above, the criterion shown in FIG. 3 has a stronger tendency to decrease the quantization parameter than the criterion shown in FIG. Therefore, when the increase / decrease value R of the quantization parameter is determined using the determination criterion shown in FIG. 3, the amount of generated code is more likely to increase. In particular, when the quantization parameter is already set to a large value and the generated code amount is suppressed to a small value, if the code storage amount BF becomes less than the target code amount TB, the generated code amount is immediately increased and the code amount is increased. It is desired that the accumulated amount BF reaches the target code amount TB. Therefore, when the current quantization parameter QPn is larger than the predetermined threshold value m, the determination unit 43 determines the determination criterion shown in FIG. Is adopted. Conversely, when the current quantization parameter QPn is smaller than the threshold value m, the criterion shown in FIG. 4 is adopted. When the current quantization parameter QPn is equal to the threshold value m, any one of the determination criteria shown in FIG. 3 and FIG. 4 may be used, and any one may be appropriately determined at the stage of designing the apparatus.
[0054]
In the above example, the determination unit 43 stores two determination criteria, and employs one of the determination criteria based on the magnitude of the quantization parameter. However, the present invention is not limited to this. That is, the determination unit 43 may store three or more determination criteria in which the decreasing tendency or increasing tendency of the quantization parameter is different from each other. In this case, a plurality of threshold values of the current quantization parameter QPn are set according to the number of determination criteria, and an appropriate determination criterion is determined according to the magnitude of the current quantization parameter QPn.
[0055]
Furthermore, in the above example, the plurality of determination criteria are stored in the determination unit 43 in a preset state, but the present invention is not limited to this. For example, the values of n1 to n4 in the above determination formula may be changed according to the magnitude of the current quantization parameter QPn. In this case, the determination unit 43 stores a plurality of functions that monotonically increase n1 to n4 when the current quantization parameter increases, and substitutes the current quantization parameter QPn for these functions to obtain n1 to n4. n4 is calculated respectively.
[0056]
Further, in the above example, the increase / decrease value is set in the range of −2 to +2, but the range of the increase / decrease value may be wider or narrower than this range. The above equations (2) to (6) may be appropriately set in accordance with the range of the increase / decrease value.
[0057]
Returning to FIG. 1, the quantization parameter calculation unit 44 calculates a new quantization parameter by adding the increase / decrease value R obtained by the determination unit 43 to the current quantization parameter QPn.
[0058]
Here, in the present embodiment, as described above, the criterion for determining the quantization parameter is variably set according to the magnitude of the current quantization parameter QPn, so that the generated code amount can be flexibly controlled. However, the correspondence between the size of the quantization parameter and the generated code amount is not always constant, and the generated code amount differs depending on the content of the image even if the quantization parameter has the same size. Therefore, in order to adjust the code accumulation amount BF in consideration of the generated code amount, the code amount control unit 40 of the present embodiment includes a code amount prediction unit 45 and a quantization parameter determination unit 46. With this configuration, the code amount control unit 40 does not use the quantization parameter calculated by the quantization parameter calculation unit 44 as it is, but stores the code storage amount when the coding process is performed using the quantization parameter. After predicting the BF, the quantization parameter QPn + 1 to be used for the next processing unit block is determined.
[0059]
To this end, the code amount prediction unit 45 uses the quantization parameter calculated by the quantization parameter calculation unit 44 based on the relationship between the size of the quantization parameter in the already processed processing unit block and the generated code amount. The generated code amount at the time of occurrence is predicted (hereinafter, the predicted generated code amount is referred to as a predicted generated code amount X). The code prediction unit 45 predicts a generated code amount based on transitions of a quantization parameter and a code storage amount in some previous processing unit blocks. For example, when the quantization parameter calculating section 44 calculates the quantization parameter = 9, the average value of the generated code amount when the same quantization parameter (= 9) is used in the past is the predicted generated code amount X. It is said.
[0060]
Then, the quantization parameter determination unit 46 takes in the predicted generated code amount X calculated by the code amount prediction unit 45, and adds the predicted generated code amount X to the code storage amount BF actually stored in the buffer 30. The predicted code storage amount (X + BF) is calculated, and the predicted code storage amount (X + BF) is compared with the target code amount TB. As a result of this comparison, if the predicted code storage amount (X + BF) does not exceed the target code amount TB by more than the predetermined threshold value s, the quantization parameter determination unit 46 calculates the quantization parameter calculation unit 44. Adopt quantization parameters. If the predicted code storage amount (X + BF) exceeds the target code amount TB by more than the threshold s, the quantization parameter determination unit 46 adopts the current quantization parameter QPn without increasing or decreasing the quantization parameter. .
[0061]
For this purpose, a predetermined threshold value s is stored in the quantization parameter determination unit 46 in advance. When the following equation (8) is satisfied, the quantization parameter determination section 46 determines the quantization parameter calculated by the quantization parameter calculation section 44 as the next quantization parameter QPn + 1, and calculates the following equation (9). If so, the current quantization parameter QPn is determined as the next quantization parameter QPn + 1.
(Equation 8)
(X + BF) -TB> s (8)
(Equation 9)
(X + BF) −TB ≦ s (9)
[0062]
Here, the quantization parameter calculation unit 44, the code amount prediction unit 45, and the quantization parameter determination unit 46 constitute a quantization parameter determination unit of the present invention. The quantization parameter calculator 44 corresponds to the quantization parameter calculator of the present invention, the code amount predictor 45 corresponds to the code amount predictor of the present invention, and the quantization parameter determiner 46 corresponds to the present invention. Corresponds to the adoption determination means. However, the code amount prediction unit 45 and the quantization parameter determination unit 46 are not indispensable components of the quantization parameter determination unit of the present invention, and the quantization amount calculated by the quantization parameter calculation unit 44 without predicting the code amount. Even if the quantization parameter is adopted as the next quantization parameter QPn + 1, the effect of the present invention is achieved.
[0063]
FIG. 5 is a flowchart illustrating a code amount control process performed by the video signal encoding device 1 described above. In the code amount control process, first, the target code amount calculation unit 41 calculates the target generated code amount PB of one processing unit block by the above equation (7) (step 501). Subsequently, the target code amount calculation unit 41 calculates a target code amount TB up to the processing unit block after the compression processing is completed, using the above equation (1) (step 502). Next, the code accumulation amount BF of the buffer 30 is input to the difference calculation unit 42 and the quantization parameter determination unit 46 (Step 503). Then, the difference calculator 42 calculates a difference N between the target code amount PB calculated by the target code amount calculator 41 and the code storage amount BF input from the buffer 30 (step 504).
[0064]
The determining unit 43 determines whether or not the current quantization parameter QPn is larger than a threshold value m (Step 505). When it is determined in step 505 that the current quantization parameter QPn is larger than the threshold value m, the tables n1 to n4 in the table stored in the determination unit 43 are read and set (step 506). On the other hand, when it is determined in step 505 that the current quantization parameter QPn is equal to or smaller than the threshold value m, n1 to n4 are read from Table2 in the table stored in the determination unit 43 and set (step 507). .
[0065]
When n1 to n4 are set in step 506 or step 507, the determination unit 43 determines which region the difference N belongs to using equations (2) to (4) in which n1 to n4 are set. Judgment is made and the increase / decrease value R corresponding to the area is obtained (step 508). The quantization parameter calculation unit 44 calculates a new quantization parameter by adding the increase / decrease value R obtained in step 508 to the current quantization parameter QPn (step 509). The code amount prediction unit 45 calculates a predicted generated code amount X when the quantization parameter calculated in step 509 is adopted (step 510).
[0066]
The quantization parameter determination unit 46 uses the predicted generated code amount X calculated in step 510, the code storage amount BF input in step 503, and the target code amount TB calculated in step 502. , And the following quantization parameter Qpn + 1 is determined according to the equations (8) and (9) (step 511). Then, when the processing of all the processing unit blocks is completed (YES in step 512), the code amount control processing is completed, and when the processing of all the processing unit blocks is not completed (NO in step 512), step 502 is performed. And the processing of Steps 502 to 511 is repeated.
[0067]
As described above, according to the video signal encoding device 1 of the first embodiment, the determination criterion for calculating the quantization parameter QPn + 1 used for the next processing unit block based on the current quantization parameter QPn. Is set, an appropriate quantization parameter QPn + 1 can be set according to the use state of the buffer. This makes it possible to flexibly control the amount of code generated in the encoding process according to the use state of the buffer.
[0068]
Further, when the current quantization parameter QPn is set to be high, the generated code amount is suppressed low, and when there is a margin in the free space of the buffer 30 and the generated code amount may be increased, Since the parameterization can be reduced quickly, the image quality of the video reproduced by the code data can be improved by effectively utilizing the free space of the buffer 30.
[0069]
Further, the quantization parameter determination unit 46 determines whether or not to adopt the new quantization parameter calculated by the quantization parameter calculation unit 44 based on the predicted generated code amount X, and then performs the next quantization. Since the parameter QPn + 1 is determined, it is possible to prevent the generated code amount from excessively changing due to an increase or decrease in the quantization parameter.
[0070]
(Second embodiment)
FIG. 6 is a block diagram illustrating a configuration of the video signal encoding device 2 according to the second embodiment. The video signal encoding device 2 includes an encoding unit 10, a buffer 30, and a code amount control unit 40, like the video signal encoding device according to the first embodiment. The configuration of the encoding unit 10 is the same as the configuration of the encoding unit of the first embodiment. The code amount control unit 40 includes a target code amount calculation unit 41, a difference calculation unit 42, a determination unit 43, and a quantization parameter calculation unit 44, as in the first embodiment.
[0071]
As described above, the encoding unit 10 performs the intra-frame encoding on a plurality of frames at a predetermined fixed interval, and performs the inter-frame encoding on the frames during the intra-frame encoding. Apply. In general, the code amount generated by intra-frame coding is larger than the code amount generated by inter-frame coding. Therefore, after the output of the buffer 30 immediately before the intra-frame encoding process, it is desirable to reduce the code accumulation amount remaining in the buffer 30 as much as possible, and most desirably to zero. Therefore, before the intra-frame encoding process, it is necessary to control so that the code accumulation amount of the buffer 30 does not become larger than the code amount that can be output by one output.
[0072]
Therefore, in the present embodiment, the target code amount calculation unit 41 calculates the target code amount TB using the above equation (1) for a frame on which normal inter-frame coding is performed, When the frame to be encoded is near, the target code amount TB is reduced using the following equation (10) in order to reduce the generated code amount.
(Equation 10)
Target code amount TB = (bit rate BR / frame rate FR) × (block number BN / total number of blocks TN) × α (10)
Here, α is a coefficient satisfying α <1.
[0073]
Further, in the intra-frame encoding process, the target code amount calculation unit 41 increases the target code amount TB in order to increase the generated code amount. In this case, the target code amount TB is calculated using the following equation (11).
[Equation 11]
Target code amount TB = (bit rate BR / frame rate FR) × (block number BN / total number of blocks TN) × β (11)
Here, β is a coefficient satisfying β> 1.
[0074]
As described using equation (10), by setting the target code amount TB low before intra-frame encoding, the generated code amount decreases for each processing unit block, and the output from the buffer 30 is reduced. The code accumulation amount BF remaining in the buffer 30 later decreases with each frame processing. Then, by setting the target code amount high using the equation (11) in the intra-frame encoding process, a sufficient code amount can be generated and the image quality of the intra-coded frame can be increased.
[0075]
However, simply lowering the target code amount has a problem that it takes time to reduce the code storage amount BF of the buffer, as described below. Since the code accumulation amount BF of the buffer 30 is controlled by increasing or decreasing the quantization parameter with a predetermined step width (+2 to -2), a considerable number of processes are performed until the code accumulation amount BF is sufficiently reduced. The encoding process and the output process of the unit block must be performed. Therefore, in order to keep the code accumulation amount BF of the buffer 30 to zero at the time of the intra-frame encoding process, the target code amount TB is reduced using the equation (10) long before the intra-frame encoding process. The encoding process must be performed in the state. If the number of processing unit blocks processed in a state where the target code amount TB is set to be low is large, the image quality is reduced accordingly.
[0076]
Therefore, in the present embodiment, the number of encoding processes (that is, the number of processing unit blocks) until the code accumulation amount BF of the buffer 30 is sufficiently reduced for intra-frame encoding is minimized, and the target code amount is reduced. The code amount control unit 40 is configured as follows in order to maintain image quality by performing inter-frame encoding processing as much as possible with a high TB.
[0077]
That is, similarly to the first embodiment, the determination unit 43 stores the determination criterion of the increase / decrease value of the two quantization parameters shown in FIGS. A judgment criterion having a strong tendency is stored. Then, in the normal inter-frame encoding process, one of the two criteria shown in FIGS. 3 and 4 is selected in the same manner as in the first embodiment, and a predetermined immediately before the intra-frame encoding process is performed. For a number of frames, a criterion in which the quantization parameter tends to increase is adopted. That is, when the target code amount calculation unit 41 sets the target code amount TB low in order to suppress the generated code amount immediately before the intra-frame encoding processing, the determination unit 43 also increases the determination criterion of the quantization parameter. , And the generated code amount is rapidly reduced.
[0078]
In order to perform such processing, the video signal encoding device 2 of the present embodiment further includes a counter 47 in addition to the configuration of the code amount control unit of the first embodiment, as shown in FIG. And a subtraction unit 48. The counter 47 updates the count value each time the encoding unit 10 processes one frame of image data, and resets the count value at the timing of intra-frame encoding. The subtractor 48 subtracts the count value of the counter 47 from the number of frames between frames to be intra-coded, and calculates the number of frames until the next intra-frame encoding process.
[0079]
The encoding unit 10 intra-frame encodes one frame every time, for example, every 15 frames are inter-frame encoded. The subtraction unit 48 stores a numerical value 15, which is the number of frames between frames to be intra-coded, and subtracts the count value obtained from the counter 47 from 15 to obtain a value up to intra-frame encoding. Is calculated. When the number of remaining frames reaches a predetermined number as a result of the subtraction performed by the subtraction unit 48, the target code amount calculation unit 41 reduces the target code amount TB using Expression (10), and the determination unit 43 sets the quantization parameter The increase / decrease value R of the quantization parameter is calculated by using a determination criterion in which the increase tendency is strong. Further, in the intra-frame encoding process, the target code amount calculation unit 41 calculates the target code amount TB using Expression (11). As a result, a sufficient code amount can be generated in the intra-frame encoding process.
[0080]
Then, the determination unit 43 outputs the increase / decrease value R to the quantization parameter calculation unit 44. The quantization parameter calculation unit 44 calculates a new quantization parameter by adding the increase / decrease value R to the current quantization parameter QPn. The encoding unit 10 sets the quantization parameter calculated by the quantization parameter calculation unit as the quantization parameter QPn + 1 of the next processing unit block. In the present embodiment, the quantization parameter calculation unit 44 corresponds to a quantization parameter determination unit of the present invention.
[0081]
FIG. 7 is a graph showing a criterion adopted immediately before intra-frame encoding. The criterion shown in FIG. 7 has a stronger tendency to increase the quantization parameter than the criterion shown in FIGS. 3 and 4, that is, the criterion used in the normal inter-frame encoding process. According to the criterion of FIG. 7, the area of each increase / decrease value is located at a position where the code amount is smaller than the criterion of FIGS. As shown in FIG. 7, according to this criterion, when the code accumulation amount BF of the buffer 30 exceeds the target code amount TB, the quantization parameter is immediately increased (+1).
[0082]
In addition, according to the determination criterion in FIG. 7, the area of each increase / decrease value is divided by a boundary line parallel to a straight line indicating a transition of the target code amount TB calculated by Expression (10). In the expression (10), the increase in the target code amount TB with respect to the number of processed blocks is slower than in the expression (1). Further, since each boundary line of the determination criterion in FIG. 7 is also parallel to the straight line indicating the equation (10), the inclination is gentle.
[0083]
FIG. 8 is a graph showing the relationship between the number of processing unit blocks for which processing has been completed and the code accumulation amount BF of the buffer 30. FIG. 8 shows an example in which an inter-frame encoding process in which the target code amount TB is set low is performed on two frames immediately before intra-frame encoding.
[0084]
The counter 47 adds a count value for each processing of one frame. The subtraction unit 48 subtracts the count value of the counter 47 from 15 which is the number of frames to be inter-coded, for each processing of one frame. When the result of the subtraction is larger than 2, that is, in the normal inter-frame encoding process, the target code amount calculation unit 41 calculates the target code amount TB using Expression (1). As a result, as shown in FIG. 8, the target code amount for one frame becomes the code amount that the buffer 30 can output at one time (code amount b).
[0085]
When the number of frames until the intra-frame encoding becomes two remaining frames in the subtraction unit 48, the target code amount calculation unit 41 calculates the target code amount TB using Expression (10). This reduces the target code amount for one frame (code amount c). When the target code amount TB decreases, the code storage amount BF of the buffer 30 exceeds the target code amount TB. As a result, the quantization parameter increases for each processing unit block, and the generated code amount decreases accordingly. The determination unit 43 calculates the increase / decrease value of the quantization parameter for the two frames using the determination criterion shown in FIG. As a result, the generated code amount for each processing unit rapidly decreases. During the processing of two frames, the code accumulation amount BF of the buffer 30 is sufficiently reduced, and after outputting the last frame immediately before the intra-frame encoding, the code accumulation amount BF remaining in the buffer 30 becomes zero. Become.
[0086]
When the number of frames up to the intra-frame encoding in the subtraction unit 48 becomes zero, the encoding unit 10 intra-frame encodes the image data of the next frame. At this time, the target code amount calculation unit 41 calculates the target code amount TB using Expression (11). As a result, the target code amount for one frame is increased (code amount a). Note that, as is clear from the equations (1), (10) and (11), the target code amounts a, b and c for one frame are represented by a = β × b and c = α × b. is there.
[0087]
As described above, if the determination criterion shown in FIG. 7 is used to reduce the code accumulation amount BF of the buffer 30, the encoding process in which the target code amount TB is set low is performed only for two frames immediately before the intra-frame encoding. , And more interframe coding processing can be performed with the target code amount TB set high. As a result, it is possible to reduce a decrease in the image quality of the coded data generated in the inter-frame coding process, and to generate a sufficient code amount in the intra-frame coding process.
[0088]
In the above example, the criterion in which the quantization parameter has a strong tendency to increase is used for two frames immediately before the frame to be intra-coded, but the criterion is switched in units of processing unit blocks. Is also good. That is, the counter 47 may count the number of frames or the processing unit block. In any case, it is sufficient to use a determination criterion that tends to increase the quantization parameter for a predetermined number of times of encoding processing immediately before the intra-frame encoding processing. When the counter 47 counts the processing unit blocks, the subtracting unit 48 multiplies the number of frames between frames to be intra-coded by the number of divisions of the processing unit blocks per frame (in the above example, 15 frames × 15 blocks = 225 blocks).
[0089]
As described above, according to the video signal encoding device 2 of the second embodiment, the encoding up to the next intra-frame encoding is performed on the image data of the processing unit block to be inter-frame encoded. Since the criterion is set in accordance with the number of times, when performing inter-frame coding processing, efficient coding processing that effectively utilizes the free space of the buffer can be realized.
[0090]
In the above example, in a normal inter-frame encoding process, the increase / decrease value of the quantization parameter is calculated using a plurality of determination criteria in the same manner as in the first embodiment. In the embodiment, the control of the quantization parameter may be executed by another method during the normal inter-frame encoding process. However, as in the above example, when the quantization parameter is controlled so that the code storage amount always exceeds the target code amount by using a plurality of determination criteria in the normal inter-frame coding process, the intra-frame coding is performed. The effect that the deterioration of the image quality can be reduced by rapidly reducing the quantization parameter immediately before the quantization processing becomes remarkable.
[0091]
The video signal encoding device 2 illustrated in FIG. 6 does not include the code amount prediction unit and the quantization parameter determination unit unlike the video signal encoding device 1 according to the first embodiment. As in the first embodiment, a code amount predicting unit and a quantization parameter determining unit are provided in the embodiment to predict the generated code amount when the quantization parameter calculated by the quantization parameter 44 is used. It goes without saying that the next quantization parameter may be finally determined.
[0092]
【The invention's effect】
As described above, the present invention is to flexibly control the amount of generated code according to various situations by variably setting the increase / decrease criterion of the quantization parameter, and to improve the image quality of the output video signal. Thus, a video signal processing device having an excellent effect that the video signal processing can be performed can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a video signal processing device according to a first embodiment.
FIG. 2 is a block diagram illustrating a configuration of a video signal processing device according to the first embodiment;
FIG. 3 is a graph showing a criterion (decreasing tendency: strong) according to the first embodiment;
FIG. 4 is a graph showing a criterion (decreasing tendency: weak) according to the first embodiment;
FIG. 5 is a flowchart illustrating a code amount control process according to the first embodiment;
FIG. 6 is a block diagram illustrating a configuration of a video signal processing device according to a second embodiment;
FIG. 7 is a graph showing a criterion (increase tendency: strong) according to the second embodiment;
FIG. 8 is a graph showing the relationship between the number of processed blocks and the code storage amount according to the second embodiment;
[Explanation of symbols]
10 Encoding unit
11 Division
14 Quantization unit
30 buffers
40 code amount control unit
41 Target code amount calculation unit
42 Difference calculator
43 Judgment unit
44 Quantization parameter calculator
45 Code amount prediction unit
46 Quantization parameter determination unit
47 counter
48 Subtraction unit

Claims (7)

Encoding means for encoding by quantizing the video signal using a quantization parameter for each predetermined processing unit,
A buffer for storing the video signal encoded by the encoding means,
Using a quantization parameter increase / decrease criterion representing the relationship between the amount of data stored in the buffer and the increase / decrease value of the quantization parameter, quantization that determines a quantization parameter based on the amount of data stored in the buffer Parameter determining means;
A criterion for variably setting a quantization parameter increase / decrease criterion for determining a quantization parameter to be used for data of a processing unit after the processing unit according to the quantization parameter used for the data of the processing unit. Change means;
A video signal encoding device comprising: When the quantization parameter used for the data of the processing unit is higher than a predetermined threshold, the criterion changing unit has a stronger tendency to decrease the quantization parameter than when the quantization parameter is lower than the threshold. The video signal encoding device according to claim 1, wherein a quantization parameter increase / decrease criterion is set. The quantization parameter determination means,
Quantization parameter calculation means for calculating a quantization parameter according to the quantization parameter increase / decrease criterion,
Code amount prediction means for predicting the generated code amount when quantizing the data of the processing unit using the quantization parameter calculated by the quantization parameter calculation means,
Based on the generated code amount predicted by the code amount prediction unit, and an adoption determination unit that determines whether to employ the quantization parameter calculated by the quantization parameter calculation unit,
The video signal encoding device according to claim 1, wherein the quantization parameter determined to be adopted by the adoption determination unit is determined as a quantization parameter used by the encoding unit. The encoding means encodes a video signal representing a moving image composed of a plurality of frames by intra-frame encoding and inter-frame encoding,
The criterion changing means sets the quantization parameter increase / decrease criterion for data in a processing unit to be inter-frame coded according to the number of times of coding until the next intra-frame coding. The video signal encoding device according to claim 1. Encoding means for encoding a plurality of frames by intra-frame encoding and inter-frame encoding by quantizing a video signal representing a moving image composed of a plurality of frames using a quantization parameter for each predetermined processing unit When,
A buffer for storing the video signal encoded by the encoding means,
Using a quantization parameter increase / decrease criterion representing the relationship between the amount of data stored in the buffer and the increase / decrease value of the quantization parameter, quantization that determines a quantization parameter based on the amount of data stored in the buffer Parameter determining means;
A reference changing means for variably setting the quantization parameter increase / decrease criterion according to the number of times of encoding until the next intra-frame encoding for data of a processing unit which is inter-coded by the encoding means. When,
A video signal encoding device comprising: The reference changing unit sets a quantization parameter increase / decrease criterion in which a quantization parameter increase tendency is stronger for data of a processing unit immediately before the intra-frame encoding than data of another processing unit. The video signal encoding device according to claim 5, wherein Encoding means for encoding the video signal by quantizing the video signal using a quantization parameter for each predetermined processing unit,
A buffer for storing the video signal encoded by the encoding means,
Using a quantization parameter increase / decrease criterion representing the relationship between the amount of data stored in the buffer and the increase / decrease value of the quantization parameter, quantization that determines a quantization parameter based on the amount of data stored in the buffer Parameter determining means;
Reference changing means for variably setting a quantization parameter increase / decrease criterion for determining a quantization parameter used for data of a processing unit after the processing unit,
A video signal encoding device comprising:

Images