JP2011071778A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image processing apparatus that reduces a delay amount in comparison with when code amount control is performed in a GOP unit or a frame unit. <P>SOLUTION: The image processing apparatus 1 includes an encoder 2 for executing encoding including quantization processing of an image signal, and a control unit 3 for controlling a quantization parameter in the quantization processing. The control unit 3 determines a difference between a target code amount and a generation code amount about the prescribed number of macroblocks processed just previously on the basis of a target code amount per macroblock and the generation code amount about the prescribed number of macroblocks processed just previously. Then, the control unit 3 decides a quantization parameter about a macroblock of the present processing target as an increase and decrease value with respect to a reference value on the basis of a comparison result between the difference and a prescribed threshold. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, and more particularly to a code amount control algorithm in moving image compression.

  The code amount control is a technique for optimizing the image quality by controlling the generated code amount (see, for example, Patent Documents 1 and 2 below). In the current code amount control algorithm, code amount control is generally performed in GOP (Group Of Picture) units or frame units. For example, in the code amount control for each frame, the allocated code amount for one frame is calculated, and the quantization parameter for each macroblock in the frame is controlled so as not to exceed the code amount.

Japanese Patent Laid-Open No. 10-215460 Japanese Patent Laid-Open No. 10-243399

  In the method of controlling the code amount in GOP units or frame units as the target code amount, the average interval for obtaining the target constant bit rate is long, and a relatively large value is allowed as the peak value of the code amount. Can be achieved. However, a long average interval means that the buffer time is large, and the amount of delay associated with the encoding process inevitably increases. Therefore, GOP-unit or frame-unit code amount control is suitable for applications without delay restrictions such as playback of recorded programs, but suitable for applications with severe delay restrictions (for example, wireless transmission video game machines). Not.

  The present invention has been made in view of such circumstances, and compared with a case where code amount control is performed in units of GOPs or frames by performing code amount control using a code amount in units of macroblock lines as a target code amount. Then, it aims at obtaining the image processing apparatus which can reduce delay amount.

  An image processing apparatus according to a first aspect of the present invention includes: an encoder that performs an encoding process including a quantization process for an image signal; and a control unit that controls a quantization parameter in the quantization process. Is based on the target code amount per macroblock and the generated code amount for the predetermined number of macroblocks processed immediately before, and the target code amount and generated code amount for the predetermined number of macroblocks processed immediately before A difference is obtained, and a quantization parameter relating to a current macroblock to be processed is determined as an increase / decrease value with respect to a reference value based on a comparison result between the difference and a predetermined first threshold value. It is.

  According to the image processing apparatus according to the first aspect, the control unit performs the predetermined processing performed immediately before based on the target code amount per macroblock and the generated code amount related to the predetermined number of macroblocks processed immediately before. The difference between the target code amount and the generated code amount for a number of macroblocks is obtained. Then, based on the comparison result between the difference and the predetermined first threshold, the quantization parameter for the current macroblock to be processed is determined. Therefore, the amount of delay can be reduced as compared with the case where code amount control is performed in GOP units or frame units.

  An image processing apparatus according to a second aspect of the present invention is the image processing apparatus according to the first aspect, in which the control unit determines the generated code amount related to the predetermined number of macroblocks processed immediately before the predetermined number. It is obtained by a moving accumulation operation having a calculation window having a width corresponding to.

  According to the image processing apparatus according to the second aspect, the control unit obtains the generated code amount related to the predetermined number of macro blocks processed immediately before by a moving accumulation operation having a calculation window having a width corresponding to the predetermined number. Therefore, the fluctuation of the generated code amount regarding the predetermined number of macroblocks processed immediately before is smoothed by the movement accumulation calculation, so that the control accuracy can be improved.

  In the image processing device according to the third aspect of the present invention, in particular, in the image processing device according to the first or second aspect, the control unit sets the predetermined initial value until the calculation window is filled. It is used as a reference value.

  According to the image processing apparatus according to the third aspect, the control unit uses a predetermined initial value as a reference value until the calculation window is filled. Therefore, since it is possible to avoid a situation in which the quantization parameter fluctuates greatly immediately after the start of processing, it is possible to improve the image quality.

  In the image processing device according to the fourth aspect of the present invention, in particular, in the image processing device according to any one of the first to third aspects, the first threshold value is set in a plurality of stages. The said increase / decrease value which differs according to a stage is set, It is characterized by the above-mentioned.

  According to the image processing apparatus of the fourth aspect, the first threshold value is set in a plurality of stages, and different increase / decrease values are set for each stage. Accordingly, it is possible to finely adjust the quantization parameter for the current macroblock to be processed according to the difference between the target code amount and the generated code amount for the predetermined number of macroblocks processed immediately before.

  An image processing apparatus according to a fifth aspect of the present invention is the image processing apparatus according to any one of the first to fourth aspects, and in particular, the control unit is configured to perform quantization parameters relating to the current macroblock to be processed. Is determined by referring to a comparison result between the activity evaluation value indicating the degree of variation of the pixel value in the macroblock and a predetermined second threshold value.

  According to the image processing apparatus according to the fifth aspect, the control unit determines the quantization parameter related to the current macroblock to be processed, and the activity evaluation value indicating the degree of variation in the pixel value in the macroblock. Then, a comparison result with a predetermined second threshold value is referred to. Thus, by using the activity evaluation value for a macroblock as additional information, the quantization parameter for the macroblock can be set more accurately.

  In the image processing device according to the sixth aspect of the present invention, in particular, in the image processing device according to the fifth aspect, the second threshold value is set in a plurality of stages, and the increase / decrease varies depending on each stage. A value is set.

  According to the image processing apparatus of the sixth aspect, the second threshold value is set in a plurality of stages, and different increase / decrease values are set for each stage. Accordingly, since the quantization parameter for the macroblock can be finely adjusted according to the magnitude of the activity evaluation value for the macroblock, the image quality can be improved.

  The image processing apparatus according to the seventh aspect of the present invention is the image processing apparatus according to any one of the first to sixth aspects, in particular, the quantization parameter related to the current macroblock to be processed includes a predetermined parameter. A lower limit value is set.

  According to the image processing device of the seventh aspect, a predetermined lower limit value is set for the quantization parameter related to the current macroblock to be processed. Therefore, it is possible to avoid a situation in which the quantization parameter is reduced indefinitely due to a long continuous image.

  The image processing device according to an eighth aspect of the present invention is the image processing device according to any one of the first to seventh aspects, and in particular, the control unit uses the predetermined number processed immediately before as the reference value. The average value of the quantization parameter for the macroblock is used.

  According to the image processing apparatus of the eighth aspect, the control unit uses the average value of the quantization parameter for the predetermined number of macroblocks processed immediately before as the reference value. Accordingly, the increase / decrease in the quantization parameter between the macroblocks becomes smooth, so that the image quality can be improved.

  In the image processing device according to the ninth aspect of the present invention, in particular, in the image processing device according to any one of the first to seventh aspects, the control unit uses a quantum for a macroblock processed last time as the reference value. It is characterized by using a parameter.

  According to the image processing apparatus of the ninth aspect, the control unit uses the quantization parameter related to the macroblock processed last time as the reference value. Therefore, since it is possible to quickly follow fluctuations in the generated code amount, when a macroblock with a large generated code amount appears suddenly, the instantaneous code amount exceeds the maximum transmission rate of the transmission path, and the reproduction of the moving image is interrupted. It is possible to avoid this situation.

  The image processing device according to a tenth aspect of the present invention is the image processing device according to any one of the first to seventh aspects, and in particular, the control unit uses the predetermined number processed immediately before as the reference value. One of the average value of the quantization parameters related to the macroblock and the quantization parameter related to the macroblock processed last time is selectively used.

  According to the image processing apparatus of the tenth aspect, the control unit uses, as the reference value, the average value of the quantization parameter for the predetermined number of macroblocks processed immediately before and the quantization parameter for the macroblock processed last time. One is selectively used. Therefore, by selecting an appropriate reference value according to the type of moving image to be processed, it is possible to execute appropriate code amount control according to the type of moving image.

  According to the present invention, it is possible to reduce the delay amount as compared with the case where the code amount control is performed in GOP units or frame units.

It is a block diagram which shows the structure of the image processing apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the encoding process per macroblock. It is a block diagram which shows the structure of the control part shown in FIG. It is a figure which divides and shows the determination result of a quantization parameter so that it may be easy to understand visually. It is a figure which divides and shows the determination result of a quantization parameter so that it may be easy to understand visually. It is a figure which divides and shows the determination result of a quantization parameter so that it may be easy to understand visually. It is a block diagram which shows the other structure of the control part shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

  FIG. 1 is a block diagram showing a configuration of an image processing apparatus 1 according to an embodiment of the present invention. As shown in FIG. 1, the image processing apparatus 1 includes an encoder 2 and a control unit 3. The encoder 2 is compliant with a moving image standard such as MPEG-2 or MPEG-4, and performs image processing such as quantization processing and encoding processing on the image signal S1 before compression encoding. The image signal S4 after compression encoding is output. The image signal S4 is transmitted from the image processing apparatus 1 to a display device via a wireless LAN or the like, and a moving image is displayed on the display device.

  The control unit 3 receives image signals S1 and S4 and a signal S2 indicating a target code amount per macroblock. Based on these signals S1, S2, and S4, the control unit 3 controls the quantization parameter in the quantization process in the encoder 2 by the control signal S3. The target code amount per macroblock is calculated based on the transmission bit rate from the image processing device 1 to the display device, the frame rate of the moving image, and the number of pixels of the display device.

  FIG. 2 is a diagram illustrating an example of encoding processing in units of macroblocks. FIG. 2 illustrates a high-definition one-frame image having 1280 pixels in the row direction and 720 pixels in the column direction. Since the macroblock is divided into 16 pixels in the row direction and every 16 pixels in the column direction, one frame is divided into 80 macroblocks in the row direction and 45 macroblocks in the column direction. The encoder 2 performs image compression processing in units of macro blocks. A set of macroblocks for one row is called a macroblock line.

  FIG. 3 is a block diagram showing a configuration of the control unit 3 shown in FIG. As shown in FIG. 3, the control unit 3 includes an evaluation value calculation unit 10, a parameter determination unit 11, a storage unit 12, a movement accumulation calculation unit 13, and a bit number counter 14. The image signal S1 is input to the evaluation value calculation unit 10. The signal S2 is input to the parameter determination unit 11. The image signal S4 is input to the bit number counter 14. The control signal S3 is output from the parameter determination unit 11.

Hereinafter, the operation of the image processing apparatus 1 according to the present embodiment will be described. In the following description, “B” is the code amount, “BN” is the target code amount per macroblock, “ΔB” is the difference between the target code amount and the actually generated code amount, and “j” is the macroblock. number, "QP" value of the quantization parameter "QP _0" is the initial value of the quantization parameter, "QP _j" is the value of the quantization parameter relating to the current macroblock to be processed, "QP _j-1" Is the value of the quantization parameter for the previously processed macroblock, “QP _L ” is the lower limit value of the quantization parameter, “W” is the width of the calculation window (number of macroblocks) of the moving accumulation calculation unit 13, and “y” is “S” is the row number of the pixel in the macroblock, “t” is the column number of the pixel in the macroblock, “M” is the number of rows and columns that one macroblock has, “ X " An activity evaluation value indicating the degree of variation of pixel values in the macroblock, “Th1 to Th3” (Th1>Th2> Th3) are threshold values relating to code amount, and “A1, A2” (A1> A2) are activity evaluation. Threshold values relating to values, “α ₁ , α ₂ ” (α ₁ <α ₂ ) are defined as arbitrary predetermined values, and “β ₁ , β ₂ ” (β ₁ <β ₂ ) are defined as arbitrary predetermined values, respectively. . As an example, QP ₀ = 38, QP _L = 24, W = 80, Th1 = 2000, Th2 = 1000, Th3 = −2000, A1 = 10, A2 = 5, α ₁ = 1, α ₂ = 2, β ₁ = 1 and β ₂ = 2. However, it is not limited to these numerical values, and can be set to an arbitrary value.

  Referring to FIG. 3, bit number counter 14 counts the amount of generated code for each macroblock and outputs the count result as signal S10. The signal S10 is input to the movement accumulation calculation unit 13. The movement accumulation calculation unit 13 obtains the sum of generated code amounts for a predetermined number of macro blocks (that is, a plurality of macro blocks corresponding to the width W) processed immediately before, and outputs the value as a signal S11. The signal S11 is input to the parameter determination unit 11.

The threshold values Th1 to Th3, A1, and A2 are set in advance and stored in the storage unit 12. The threshold values Th1 to Th3, A1, and A2 are input from the storage unit 12 to the parameter determination unit 11 as the signal S13. Similarly, the predetermined values α ₁ , α ₂ , β ₁ , β ₂ are set in advance and stored in the storage unit 12. The predetermined values α ₁ , α ₂ , β ₁ , β ₂ are input from the storage unit 12 to the parameter determination unit 11 as the signal S14. Further, the activity evaluation value X _j regarding the current macroblock to be processed is input from the evaluation value calculation unit 10 to the parameter determination unit 11 as the signal S12.

First, the quantization parameter QP determination algorithm (in other words, initialization of the algorithm) for the first macroblock (that is, j = 1) will be described. As shown in Equation (1), ΔB ₁ is 0 for the _first macroblock. As shown in Expression (2), the parameter determination unit 11 determines the quantization parameter QP ₁ as the initial value QP ₀ .

Next, the quantization parameter QP determination algorithm for the second to Wth macroblocks (that is, 2 ≦ j ≦ W) will be described. ΔB _j is expressed by Expression (3). When the condition shown in Expression (4-1) is satisfied, the parameter determination unit 11 determines the quantization parameter QP _j as shown in Expression (4-2). The symbol “∩” in formula (4-1) means “and”. Similarly, the conditions shown in the equations (5-1), (6-1), (7-1), (8-1), (9-1), (10-1), and (11-1) are as follows. In the case of satisfying, the parameter determination unit 11 sets the quantization parameter QP _j to the expressions (5-2), (6-2), (7-2), (8-2), (9-2), (10− 2) and (11-2) respectively.

Next, the calculation for obtaining the activity evaluation value X will be described. The evaluation value calculation unit 10 obtains the activity evaluation value X according to the equation (32). The average pixel value (bar y _{s, t} ) in the equation (32) is defined by the equation (33).

FIG. 4 is a diagram showing the determination result of the quantization parameter QP _j by the algorithm shown in the above formulas (3) to (11-2) so that it can be easily understood visually. Based on the target code amount BN per macroblock and the generated code amount related to the j-1 macroblock processed immediately before, the parameter determination unit 11 generates the target code amount and the generated code related to j-1 macroblocks. A difference (ΔB _j ) from the code amount is obtained. Then, the parameter determination unit 11 sets the quantization parameter QP _j related to the current macroblock to be processed based on the comparison result between the difference (ΔB _j ) and the threshold values Th1 to Th3. It is determined as an increase / decrease value with respect to the value QP ₀ ).

In addition, when determining the quantization parameter QP _j for the current macro block to be processed, the parameter determination unit 11 determines an activity evaluation value X _j indicating the degree of variation in pixel values in the macro block, and a threshold value A1. Reference is made to the comparison result with A2. That is, the parameter determination unit 11 sets the quantization parameter QP _j related to the current macroblock to be processed based on the comparison result between the activity evaluation value X _j and the threshold values A1 and A2 as the reference value (in this case, the initial value). It is determined as an increase / decrease value with respect to the value QP ₀ ).

Here, a lower limit value QP _L is set for the quantization parameter QP _j . Parameter determining section 11, when the value of the quantization parameter QP _j determined by the algorithm of Figure 4 is larger than the lower limit value QP _L adopts the quantization parameter QP _j, whereas, as determined by the algorithm of Figure 4 If the value of the quantization parameter QP _j is less than the lower limit value QP _L adopts the lower limit QP _L. An expression representing an algorithm for determining a quantization parameter QP based on a comparison result between the quantization parameter QP _j and the lower limit value QP _L is shown. When the condition shown in Expression (12-1) is satisfied, the parameter determination unit 11 determines the quantization parameter QP _j as shown in Expression (12-2). Further, if conditions are met shown in the formula (13-1), the parameter determination unit 11 determines the quantization parameter QP _j according to Equation (13-2).

Next, the first determination algorithm of the quantization parameter QP regarding the (W + 1) th and subsequent macroblocks will be described. ΔB _j is expressed by Expression (14). When the condition shown in Expression (15-1) is satisfied, the parameter determination unit 11 determines the quantization parameter QP _j as shown in Expression (15-2). Similarly, the conditions shown in the equations (16-1), (17-1), (18-1), (19-1), (20-1), (21-1), and (22-1) are as follows. When satisfying, the parameter determination unit 11 sets the quantization parameter QP _j to the expressions (16-2), (17-2), (18-2), (19-2), (20-2), (21−). 2) and (22-2) respectively. Note that the average value (bar QP _j−1 ) of the quantization parameters for the W macroblocks before the macroblock processed last time is defined by Expression (23).

FIG. 5 is a diagram showing the determination result of the quantization parameter QP _j by the algorithm shown in the above formulas (14) to (23) divided so as to be easily understood visually. Based on the target code amount BN per macroblock and the generated code amount related to the W macroblocks processed immediately before, the parameter determination unit 11 calculates the target code amount and generated code amount related to the W macroblocks. The difference (ΔB _j ) is obtained. Then, the parameter determination unit 11 sets the quantization parameter QP _j related to the current macroblock to be processed based on the comparison result between the difference (ΔB _j ) and the threshold values Th1 to Th3. QP _j-1 ) is determined as an increase / decrease value.

In addition, when determining the quantization parameter QP _j for the current macro block to be processed, the parameter determination unit 11 determines an activity evaluation value X _j indicating the degree of variation in pixel values in the macro block, and a threshold value A1. Reference is made to the comparison result with A2. That is, the parameter determination unit 11 sets the quantization parameter QP _j related to the current macroblock to be processed based on the comparison result between the activity evaluation value X _j and the thresholds A1 and A2 to the reference value (in this case, the bar QP _j-1 ) is determined as an increase / decrease value.

Here, similarly to the above, the lower limit value QP _L is set for the quantization parameter QP _j . Parameter determining section 11, when the value of the quantization parameter QP _j determined by the algorithm of FIG. 5 is larger than the lower limit value QP _L adopts the quantization parameter QP _j, whereas, as determined by the algorithm of FIG. 5 If the value of the quantization parameter QP _j is less than the lower limit value QP _L adopts the lower limit QP _L.

Next, the second determination algorithm of the quantization parameter QP regarding the (W + 1) th and subsequent macroblocks will be described. ΔB _j is expressed by the above equation (14). When the condition shown in Expression (24-1) is satisfied, the parameter determination unit 11 determines the quantization parameter QP _j as shown in Expression (24-2). Similarly, the conditions shown in the equations (25-1), (26-1), (27-1), (28-1), (29-1), (30-1), and (31-1) are as follows. When satisfying, the parameter determination unit 11 sets the quantization parameter QP _j to the expressions (25-2), (26-2), (27-2), (28-2), (29-2), (30− 2) and (31-2) respectively.

FIG. 6 is a diagram showing the determination result of the quantization parameter QP _j by the algorithm shown in the above formulas (24-1) to (31-2) divided so as to be easily understood visually. Based on the target code amount BN per macroblock and the generated code amount related to the W macroblocks processed immediately before, the parameter determination unit 11 calculates the target code amount and generated code amount related to the W macroblocks. The difference (ΔB _j ) is obtained. Then, the parameter determination unit 11 sets the quantization parameter QP _j related to the current macroblock to be processed based on the comparison result between the difference (ΔB _j ) and the threshold values Th1 to Th3. It is determined as an increase / decrease value for the quantization parameter QP _j−1 ) regarding the processed macroblock.

In addition, when determining the quantization parameter QP _j for the current macro block to be processed, the parameter determination unit 11 determines an activity evaluation value X _j indicating the degree of variation in pixel values in the macro block, and a threshold value A1. Reference is made to the comparison result with A2. That is, the parameter determination unit 11 sets the quantization parameter QP _j related to the current macroblock to be processed based on the comparison result between the activity evaluation value X _j and the threshold values A1 and A2 to the reference value (in this case, the quantum And an increase / decrease value with respect to the conversion parameter QP _j−1 ).

Here, similarly to the above, the lower limit value QP _L is set for the quantization parameter QP _j . Parameter determining section 11, when the value of the quantization parameter QP _j determined by the algorithm of Figure 6 is greater than the lower limit value QP _L adopts the quantization parameter QP _j, whereas, as determined by the algorithm of Figure 6 If the value of the quantization parameter QP _j is less than the lower limit value QP _L adopts the lower limit QP _L.

  FIG. 7 is a block diagram showing another configuration of the control unit 3 shown in FIG. Information regarding the type of moving image to be processed by the image processing apparatus 1 is input to the parameter determination unit 11 as a signal S20. For example, when the image processing apparatus 1 is mounted on a video game machine, information regarding the type of game and information regarding the current scene in progress in the game are input as the signal S20. The parameter determination unit 11 selects and applies one of the algorithm shown in FIG. 5 and the algorithm shown in FIG. 6 based on the signal S20.

As described above, according to the image processing apparatus 1 according to the present embodiment, the control unit 3 is based on the target code amount BN per macroblock and the generated code amount related to the W macroblocks processed immediately before. Then, a difference (ΔB _j ) between the target code amount and the generated code amount regarding the W macroblocks processed immediately before is obtained. Based on the comparison result between the difference (ΔB _j ) and the threshold values Th1 to Th3, the quantization parameter QP _j for the current macroblock to be processed is determined. Therefore, the amount of delay can be reduced as compared with the case where code amount control is performed in GOP units or frame units.

  Also, according to the image processing apparatus 1 according to the present embodiment, the control unit 3 calculates the generated code amount related to the W macroblocks processed immediately before by a moving accumulation calculation having a calculation window having a width corresponding to the number. Ask for. Therefore, since the fluctuation of the generated code amount regarding the W macroblocks processed immediately before is smoothed by the movement accumulation calculation, the control accuracy can be improved.

Further, according to the image processing apparatus 1 according to the present embodiment, the control unit 3 uses the predetermined initial value QP ₀ as a reference value until the calculation window is filled. Therefore, since it is possible to avoid a situation in which the quantization parameter fluctuates greatly immediately after the start of processing, it is possible to improve the image quality.

Further, according to the image processing apparatus 1 according to the present embodiment, the threshold values Th1 to Th3 are set in a plurality of stages, and different increase / decrease values (−1, ± 0, + β _1, + β depending on each stage). ₂ ) is set. Therefore, the quantization parameter QP _j for the current macroblock to be processed is finely adjusted according to the difference (ΔB _j ) between the target code amount and the generated code amount for the W macroblocks processed immediately before. Is possible.

Further, according to the image processing apparatus 1 according to the present embodiment, the control unit 3 determines the degree of variation in pixel values in the macroblock when determining the quantization parameter QP _j for the current macroblock to be processed. The comparison result between the activity evaluation value X _{j shown} and the threshold values A1 and A2 is referred to. Therefore, by using the activity evaluation value X _j for the macroblock as additional information, the quantization parameter QP _j for the macroblock can be set more accurately.

Further, according to the image processing apparatus 1 according to the present embodiment, the thresholds A1 and A2 are set in a plurality of stages, and different increase / decrease values (± 0, −α _1, −α ₂₎ depending on each stage. ) Is set. Accordingly, since the quantization parameter QP _j related to the macroblock can be finely adjusted according to the magnitude of the activity evaluation value _Xj related to the macroblock, the image quality can be improved.

Further, according to the image processing apparatus 1 according to the present embodiment, the predetermined lower limit value QP _L is set in the quantization parameter QP _j regarding the current macro block to be processed. Therefore, it is possible to avoid a situation in which the quantization parameter QP _j is decreased indefinitely due to, for example, continuous still images.

Further, according to the example illustrated in FIG. 5, the control unit 3 uses the average value (bar QP _j−1 ) of the quantization parameters regarding the W macroblocks processed immediately before as the reference value. Accordingly, since the increase / decrease of the quantization parameter QP _j between the macroblocks becomes smooth, the image quality can be improved.

Further, according to the example illustrated in FIG. 6, the control unit 3 uses the quantization parameter QP _j−1 related to the previously processed macroblock as the reference value. Therefore, since it is possible to quickly follow fluctuations in the generated code amount, when a macroblock with a large generated code amount appears suddenly, the instantaneous code amount exceeds the maximum transmission rate of the transmission path, and the reproduction of the moving image is interrupted. It is possible to avoid this situation.

Further, according to the example shown in FIG. 7, the control unit 3 uses, as the reference value, the average value (bar QP _j−1 ) of the quantization parameter for the W macroblocks processed immediately before and the previous processing. One of the quantization parameters QP _{j−1 for} the macroblock is selectively used. Therefore, by selecting an appropriate reference value according to the type of moving image to be processed, it is possible to execute appropriate code amount control according to the type of moving image.

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 2 Encoder 3 Control part 10 Evaluation value calculating part 11 Parameter determining part 12 Storage part 13 Movement accumulation calculating part 14 Bit number counter

Claims (10)

An encoder that performs encoding processing including quantization processing on an image signal;
A control unit for controlling a quantization parameter in the quantization process,
Based on the target code amount per macroblock and the generated code amount related to the predetermined number of macroblocks processed immediately before, the control unit sets the target code amount and generated code related to the predetermined number of macroblocks processed immediately before Image processing that obtains a difference from an amount and determines a quantization parameter related to a current macroblock to be processed as an increase / decrease value with respect to a reference value based on a comparison result between the difference and a predetermined first threshold value apparatus.   The image processing apparatus according to claim 1, wherein the control unit obtains a generated code amount related to the predetermined number of macroblocks processed immediately before by a moving accumulation operation having a calculation window having a width corresponding to the predetermined number.   The image processing apparatus according to claim 1, wherein the control unit uses a predetermined initial value as the reference value until the calculation window is filled.   The image processing apparatus according to claim 1, wherein the first threshold value is set in a plurality of stages, and the increase / decrease value that is different for each stage is set.   In determining the quantization parameter for the current macroblock to be processed, the control unit includes an activity evaluation value indicating a degree of variation in pixel values in the macroblock and a predetermined second threshold value. The image processing apparatus according to claim 1, wherein the comparison result is referred to.   The image processing apparatus according to claim 5, wherein the second threshold value is set in a plurality of stages, and the increase / decrease value different according to each stage is set.   The image processing apparatus according to claim 1, wherein a predetermined lower limit value is set for a quantization parameter related to the current macroblock to be processed.   The image processing apparatus according to claim 1, wherein the control unit uses an average value of quantization parameters regarding the predetermined number of macroblocks processed immediately before as the reference value.   The image processing apparatus according to claim 1, wherein the control unit uses a quantization parameter related to a previously processed macroblock as the reference value. The control unit selectively uses, as the reference value, one of an average value of quantization parameters related to the predetermined number of macroblocks processed immediately before and a quantization parameter related to macroblocks processed last time. The image processing apparatus according to any one of?

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