JP2009055262A - Image encoding control device, image encoding control method, image encoding control program, and computer-readable medium recorded with the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new image encoding control technology capable of achieving stable encoding control even in the case of encoding images to be gradually changed in difficulty of image. <P>SOLUTION: Paying attention to a fact that action showing the index of complication and action showing the screen characteristic quantity such as screen total variance value are similar to each other, the screen characteristic quantity of a picture to be encoded is computed by correcting the index of complication of I picture, and the index of complication of the I picture is corrected based on the computed screen characteristic quantity of the picture to be encoded and the screen characteristic quantity of the I picture encoded last before the picture to be encoded so as to set the index of complication of the I picture to be used to decide a target encoding quantity of the picture to be encoded, and the target encoding quantity of the picture to be encoded is decided by using the set index of complication. With this structure, prediction accuracy of the target encoding quantity of the picture to be encoded is raised, and stable encoding control can be achieved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a video coding control apparatus and method for determining a target code amount of a picture to be coded based on an image complexity index, a video coding control program used for realizing the video coding control apparatus, and a method thereof. The present invention relates to a computer-readable recording medium on which the program is recorded.

  MPEG2 test Model 5 (hereinafter referred to as MPEG2 TM5) standardizes a method for determining a target code amount of a picture to be encoded that is necessary for performing rate control (quantization control) (for example, see Non-Patent Document 1). ).

  This MPEG2 TM5 standardizes the determination of the target code amount of a picture to be encoded based on the number of pictures of each picture type to be encoded and the complexity index of each picture type of encoded picture. .

Here, the complexity index X [β] of a picture β is the code amount S [β] generated when the picture β is encoded, and the average value aveQ ( β] and
X [β] = S [β] × aveQ [β]
It is derived according to the following formula.

  Next, a method for determining the target code amount of the encoding target picture to be standardized by MPEG2 TM5 will be described with reference to FIG.

  As shown in FIG. 12, the number of I pictures included in future Z pictures including the picture to be encoded (picture α shown in the figure) is Ni, the number of P pictures is Np, and the number of B pictures is Nb. For example, in MPEG2 TM5, when the encoding target picture is a P picture, it is defined that the target code amount Tp is determined according to the following equation (1), and the encoding target picture is a B picture. In some cases, it is defined that the target code amount Tb is determined according to the following equation (2). When the encoding target picture is an I picture, the target code amount is determined according to the following equation (3). It is specified that the quantity Ti is determined.

  Here, Kp and Kb in the formula represent constants. R represents the remaining code amount for Z pictures (total target code amount for Z pictures). Xi represents the complexity index of the I picture (picture β shown in the figure) encoded before and at the end of the encoding target picture, and Xp is encoded before and at the end of the encoding target picture. Represents the complexity index of the P picture, and Xb represents the complexity index of the B picture encoded before and at the end of the current picture.

Thus, in MPEG2 TM5, for each picture included in the future Z pictures, each of the I picture, P picture, and B picture is
Ti: Tp: Tb = (Xi / 1) :( Xp / Kp) :( Xb / Kb)
Therefore, it is specified that the remaining code amount R is allocated.

  In the prior art, the target code amount of the picture to be encoded is determined by executing the processes of the flowcharts shown in FIGS. 13 and 14 in accordance with the MPEG2 TM5 standard.

  That is, as shown in the flowchart of FIG. 13, first, in step S300, when encoding of the first picture of the GOP is started, the number of GOP pictures (gopN) is multiplied by the average code amount per picture. Then, the total target code amount of the GOP to be encoded is calculated, and the remaining code amount of the GOP to be encoded is added by adding the remaining code amount in the previous GOP to the calculated total target code amount. The code amount R is obtained.

  Subsequently, in step S301, an encoding target picture is selected according to the order from the first picture of the GOP. Subsequently, in step S302, the complexity index X of pictures of various encoded picture types is read from the memory.

  Subsequently, in step S303, from the read complexity index X, the complexity index Xi of the I picture encoded last and before the encoding target picture, and the encoding index before the encoding target picture and the last one are encoded. Are extracted from the complexity index Xp of the P picture encoded in step B and the complexity index Xb of the B picture encoded last and before the picture to be encoded, and these complexity indices Xi, Xp, Xb are extracted. And the above-described Ni, Np, and Nb, the target code amount T of the encoding target picture is determined.

  That is, as shown in the flowchart of FIG. 14, when the picture to be encoded is a P picture, the complexity index Xi, Xp, Xb is used to determine the target code amount Tp according to the equation (1), and the encoding is performed. If the target picture is a B picture, the complexity index Xi, Xp, Xb is used to determine the target code amount Tb according to the equation (2). If the target picture is an I picture, the complexity Using the indices Xi, Xp, and Xb, the target code amount Ti is determined according to the equation (3).

  Subsequently, in step S304, a quantization step is set according to the determined target code amount T, and the encoding target picture is encoded. Subsequently, in step S305, the code amount S generated by encoding the encoding target picture is measured. Subsequently, in step S306, the remaining code amount R is updated by subtracting the generated code amount S from the remaining code amount R.

  Subsequently, in step S307, the average value aveQ of the quantization step Q used for encoding the encoding target picture is calculated. Subsequently, in step S308, the complexity index X of the picture to be encoded is calculated according to “X = S × aveQ” and written into the memory.

  Subsequently, in step S309, it is determined whether or not the GOP has ended. When it is determined that the GOP has not ended, the process returns to step S301. When it is determined that the GOP has ended, The process returns to step S300 to process the GOP.

  FIG. 15 shows a device configuration of a conventional video encoding device that executes this processing.

  As shown in this figure, the conventional video encoding apparatus includes an encoding unit 100 and a rate control unit 200. The encoding unit 100 includes a macroblock division unit 101, a motion prediction unit 102, and a motion compensation unit 103. , An intra / inter selection unit 104, a subtractor 105, a DCT unit 106, a quantization unit 107, an information source encoding unit 108, an inverse quantization unit 109, an inverse DCT unit 110, an adder 111, and a frame memory 112, The macro block to be encoded is encoded according to the quantization step value given from the rate control unit 200, and the code amount generated at that time is notified to the rate control unit 200.

  On the other hand, the rate control unit 200 includes a remaining IPB number updating unit 201 that updates the remaining number of pictures in the GOP, a GOP remaining code amount updating unit 202 that updates the remaining code amount of the GOP, an IPB number and a remaining GOP code amount. And a target code amount calculation unit 203 that calculates a target code amount of a picture to be encoded based on the complexity index read from the encoded picture complexity index memory 300, and a macroblock quantum based on the target code amount The macro block quantization step calculation unit 204 that calculates the quantization step value and supplies the quantization step value to the quantization unit 107, and the generated code amount of the macro block given from the information source coding unit 108 is aggregated to generate the generated code of the picture to be encoded Quantization step value given to picture generation code amount calculation unit 205 for calculating the amount and quantization unit 107 A picture average quantization step calculation unit 206 that calculates an average value in the encoding target picture, and calculates a complexity index of the encoding target picture that has been encoded based on the average quantization step value and the generated code amount And a complexity index calculating unit 207 that writes the encoded picture complexity index memory 300 to the encoded picture complexity index memory 300, thereby controlling encoding performed by the encoding unit 100.

The conventional video encoding apparatus determines the target code amount of the encoding target picture according to the MPEG2 TM5 standard by executing the flowcharts of FIGS. 13 and 14 according to the configuration of FIG. The encoding target picture is encoded.
Internet <URL: http://www.mpeg.org/MSSG/tm5/Ch10/Ch10.html>

  Fade video, which is one of the video effects of moving images, has the problem that rate control (quantization control) in video coding is difficult because the difficulty of the image gradually changes without scene changes. is there.

  On the other hand, as described above, in the conventional video encoding apparatus, the target code amount of the encoding target picture is determined according to the MPEG2 TM5 standard.

  As a result, in the conventional video encoding apparatus, even when a video such as a faded video in which the difficulty of an image gradually changes is encoded, a complicated result that is the encoding result of the most recently encoded I / P / B picture is obtained. The target code amount of the picture to be encoded is determined using the depth indices Xi, Xp, and Xb.

  However, in such a method, the complexity index obtained a long time ago is used as the complexity index of the same picture type to be encoded in the future, and the target code amount of the current picture to be encoded is encoded. Will be predicted.

  Thus, in the conventional video encoding device, the prediction accuracy of the target code amount of the encoding target picture does not increase, and in the case of encoding a fade-in video (a video in which a dark screen becomes gradually brighter), the code amount is In the case of encoding a fade-out video (a video in which a bright screen becomes gradually darker), there is a problem that the amount of codes is not higher than expected.

  As described above, in the conventional technology, the complexity index obtained a long time ago is used as the complexity index of the same picture type to be encoded in the future, and the target code amount of the encoding target picture to be encoded from now on is used. Therefore, when encoding a video in which the prediction accuracy of the target code amount does not increase and the difficulty of the image gradually changes, the image quality deteriorates due to unstable encoding control. There is.

  In particular, since the I picture only appears at the beginning of the GOP and has a smaller number of appearances than the P picture and the B picture, the complexity index obtained long before is used. Make it big.

  The present invention has been made in view of such circumstances, and is a new video encoding control technique that can realize stable encoding control even when encoding video in which the difficulty of an image gradually changes. The purpose is to provide.

[1] First Configuration In order to achieve the above-described object, the video coding control apparatus according to the present invention includes the number of pictures of each picture type included in a predetermined number of pictures to be coded, and a picture to be coded. When adopting a configuration in which the target code amount of a picture to be coded is determined based on the complexity index of the picture of each picture type coded before and last, (1) the picture of the picture to be coded A calculation means for calculating a feature value; (2) based on the screen feature value calculated by the calculation means and the screen feature value of the I picture encoded last and before the encoding target picture; Setting means for setting the complexity index of the I picture used for determining the target code amount of the picture to be encoded by correcting the complexity index of (3), and (3) the complexity set by the setting means And determining means for determining a target code amount of the encoding target picture using the exponent.

  When adopting this configuration, the screen variance total value may be used as the screen feature amount. In this case, the calculation unit calculates the screen variance total value as the screen feature amount, and the setting unit calculates the calculation unit. The complexity index of the I picture is set on the basis of the calculated screen variance total value and the screen variance total value of the I picture encoded last and before the encoding target picture.

  Also, when this configuration is adopted, if the encoding target picture is a B picture, (i) the setting means sets the complexity index of the I picture used to determine the target code amount of the encoding target picture. (Ii) the P picture that is encoded before and at the end of the encoding target picture is used as the complexity index of the I picture used to determine the target code amount of the encoding target picture. It is decided to use the complexity index of the I picture used in determining the target code amount.

  Each of the above processing means can also be realized by a computer program. This computer program is provided by being recorded on an appropriate computer-readable recording medium or provided via a network, and is used when implementing the present invention. The present invention is realized by being installed and operating on a control means such as a CPU.

  In the video encoding control apparatus of the present invention configured as described above, a screen such as the behavior indicated by the complexity index of the image and the screen variance total value (values such as L1 variance and L2 variance for the pixels in the image), etc. Focusing on the fact that the behavior indicated by the feature amount is similar, the complexity index obtained long ago is used because the appearance frequency is the lowest among the I, P, and B pictures. Using the complexity index of the I picture as a correction target, the screen feature amount of the encoding target picture is calculated, and the calculated screen feature amount of the encoding target picture is encoded before and at the end of the encoding target picture. By correcting the complexity index of the I picture based on the screen feature value of the I picture, the complexity index of the I picture used to determine the target code amount of the encoding target picture is set, Set So as to determine the target code amount of the encoding target picture by using the complexity index.

  At this time, considering that rearrangement occurs for the B picture, if the encoding target picture is a B picture, the complexity index of the I picture is not corrected and the target code of the encoding target picture is not corrected. As the complexity index of the I picture used to determine the amount, the complexity index of the I picture used in determining the target code amount of the P picture encoded before and at the end of the encoding target picture is used. Like that.

  In this way, in the video coding control apparatus of the present invention, when determining the target code amount of the picture to be coded, the complexity index of I picture is not used in terms of the complexity index that is much earlier in time. Therefore, since the complexity index at the time of the encoding target picture predicted using the change in the screen feature amount is used, the prediction accuracy of the target encoding amount of the encoding target picture increases, and the difficulty of the image gradually changes. Even when the video to be encoded is encoded, the encoding control is stabilized and the deterioration of the image quality can be prevented.

[2] Second Configuration In order to achieve the above-described object, the video coding control apparatus according to the present invention includes the number of pictures of each picture type included in a predetermined number of pictures to be coded, and a picture to be coded. When a configuration is adopted in which the target code amount of the encoding target picture is determined based on the complexity index of the picture of each picture type encoded before and last, (1) than the encoding target picture A calculation means for calculating the screen feature value of the I picture to be encoded later and first; (2) the screen feature value calculated by the calculation means; and the encoding before the encoding target picture. By correcting the complexity index of the I picture based on the screen feature quantity of the I picture, the complexity index of the I picture used to determine the target code quantity of the encoding target picture is obtained. A setting unit configured to set; and (3) a determination unit configured to determine a target code amount of the encoding target picture using the complexity index set by the setting unit.

  When adopting this configuration, the screen variance total value may be used as the screen feature amount. In this case, the calculation unit calculates the screen variance total value as the screen feature amount, and the setting unit calculates the calculation unit. The complexity index of the I picture is set on the basis of the calculated screen variance total value and the screen variance total value of the I picture encoded last and before the encoding target picture.

  Each of the above processing means can also be realized by a computer program. This computer program is provided by being recorded on an appropriate computer-readable recording medium or provided via a network, and is used when implementing the present invention. The present invention is realized by being installed and operating on a control means such as a CPU.

  In the video coding control apparatus of the present invention configured as described above, a screen such as the behavior indicated by the complexity index of the image and the screen variance total value (values such as L1 variance and L2 variance for the pixels in the screen), etc. Focusing on the fact that the behavior indicated by the feature amount is similar, the complexity index obtained long ago is used because the appearance frequency is the lowest among the I, P, and B pictures. Using the complexity index of the I picture as a correction target, calculate the screen feature amount of the I picture to be encoded first after the encoding target picture, the calculated screen feature amount of the encoding target picture, The target code amount of the encoding target picture is determined by correcting the complexity index of the I picture based on the screen feature amount of the I picture encoded before and at the end of the encoding target picture. In Set the complexity index of I pictures are, so as to determine the target code amount of the encoding target picture by using the complexity index was the setting.

  In this way, in the video coding control apparatus of the present invention, when determining the target code amount of the picture to be coded, the complexity index of I picture is not used in terms of the complexity index that is much earlier in time. Therefore, since the complexity index at a future time point is used rather than the current picture predicted using changes in the screen feature value, the target code quantity prediction accuracy of the current picture increases and the picture becomes difficult. Even when a video with a gradually changing length is encoded, the encoding control is stabilized and the deterioration of the image quality can be prevented.

  According to the present invention, when determining the target code amount of a picture to be encoded, the change of the screen feature amount is used for the complexity index of the I picture, instead of using the complexity index that is much earlier in time. Therefore, the prediction accuracy of the target code amount of the encoding target picture is improved, and the complexity index at the time of the encoding target picture predicted in advance and the complexity index at the future time point are used. Even when a video whose difficulty is gradually changed is encoded, the encoding control is stabilized and the deterioration of the image quality can be prevented.

  Hereinafter, the present invention will be described in detail according to embodiments.

  FIG. 1 illustrates a device configuration of a video encoding device 1 to which the present invention is applied.

  As shown in this figure, a video encoding apparatus 1 to which the present invention is applied includes an encoding unit 100 and a rate control unit 200, and the encoding unit 100 is a quantization step given from the rate control unit 200. The macroblock to be encoded is encoded according to the value, and the code amount generated at that time is notified to the rate control unit 200. The rate control unit 200 remains based on the generated code amount received from the encoding unit 100. While updating the target code amount, the quantization step value of the encoding target macroblock is set and supplied to the encoding unit 100.

[1] First Embodiment Next, a method for determining a target code amount of a picture to be encoded according to a first embodiment of the present invention will be described with reference to FIG.

In this embodiment example,
(B) The behavior indicated by the complexity index of the image is similar to the behavior indicated by the total screen variance,
(B) If the picture to be encoded is represented as picture α, and the I picture coded before and at the end of the picture to be coded is represented as picture β, the screen variance total value for picture α and picture β Note that the complexity index Xi [β] of the picture β, the screen variance total value var [β] of the picture β, and the screen variance total value var [α] of the picture α On the basis of the complexity index Xi [α] when the picture α is an I picture,
Xi [α] = Xi [β] × (var [α] / var [β])
Thus, the predicted Xi [α] is used instead of the complexity index Xi shown in the equations (1) and (3) used in the determination of the target code amount of the picture α by the prior art. The configuration is to be taken.

  In the following, the picture β, which is an I picture, may be referred to as an I picture β for simplicity.

  Here, as the screen dispersion total value, the following L1 dispersion value, L2 dispersion value, or the like can be used.

L1 dispersion value = ΣΣ | I _xy −A _ve |
Where ΣΣ is the sum of the pixels in the macroblock
I _xy is the pixel value of the pixel in the macroblock
A _ve is the average pixel value of the pixels in the macroblock
L2 dispersion value = ΣΣ | I _xy −A _ve | ²
Where ΣΣ is the sum of the pixels in the macroblock
I _xy is the pixel value of the pixel in the macroblock
_Ave is the average value of the pixel values of the pixels in the macroblock. FIGS. 3 and 4 are flowcharts executed by the rate control unit 200 configured in this embodiment.

  Next, according to the flowcharts of FIGS. 3 and 4, the target code amount determination process of the encoding target picture executed by the present embodiment will be described.

  According to the present embodiment, as shown in the flowchart of FIG. 3, the rate control unit 200 first enters the number of GOP pictures (gopN) and 1 when the encoding of the first picture of the GOP starts in step S100. Multiply by the average code amount per picture to calculate the total target code amount of the GOP to be encoded, and add the remaining code amount in the previous GOP to the calculated total target code amount Thus, the remaining code amount R of the GOP to be encoded is obtained.

  Subsequently, in step S101, the encoding target picture α is selected according to the order from the first picture of the GOP.

  Subsequently, in step S102, the screen variance total value var [α] of the encoding target picture α is calculated.

  Subsequently, in step S103, the screen variance total value var [β] of the I picture β encoded last and before the encoding target picture α is read from the memory. The I picture β is encoded before the encoding target picture α, and the screen variance total value var [β] is calculated and stored in the memory at that time, and is read from the memory.

  Subsequently, in step S104, the encoded complexity indices X of various picture types including the complexity index Xi [β] of the I picture β are read out from the memory.

  Subsequently, in step S105, the complexity index X read from the memory, the calculated screen variance total value var [α], the screen variance total value var [β] read from the memory, and the aforementioned Ni, Np, Nb. Are used to determine the target code amount T of the encoding target picture α.

That is, when entering the process of step S105, as shown in the flowchart of FIG. 4, first, in step S1050, it is determined whether or not the encoding target picture α is a P picture, and the encoding target picture α Is determined to be a P picture, the process proceeds to step S1051, and the complexity index Xi [β] of the I picture β, the screen variance total value var [β] of the I picture β, and the encoding target picture α Based on the total screen variance var [α]
Xi [α] = Xi [β] × (var [α] / var [β])
According to the calculation formula, the complexity index Xi [α] that the encoding target picture α will have if it is an I picture is predicted.

  Subsequently, in step S1052, the predicted complexity index Xi [α] is set as the complexity index Xi used in Expression (1), and the encoding target picture α is selected from the complexity indices X read from the memory. The complexity index Xp of the P picture encoded before and last and the complexity index Xb of the B picture encoded last and before the encoding target picture α are extracted and their complexity is extracted. The target code amount Tp is determined according to the above-described equation (1) using the depth index Xi, Xp, Xb and the above-described Ni, Np, Nb.

  On the other hand, when it is determined in step S1050 that the encoding target picture is not a P picture, the process proceeds to step S1053 to determine whether or not the encoding target picture α is a B picture. When it is determined that the picture is a picture, the process proceeds to step S1054, and the complexity index Xi used when calculating the target code amount of the P picture encoded before and last from the encoding target picture α from the memory. To get.

  Subsequently, in step S1055, out of the complexity index X read from the memory, the complexity index Xp of the P picture encoded last before the encoding target picture α and the encoding target picture α is determined. Extract the complexity index Xb of the B picture encoded before and last, and use the obtained complexity index Xi and the extracted Xp, Xb and the aforementioned Ni, Np, Nb, and The target code amount Tb is determined according to (2).

  Here, when the encoding target picture α is a B picture, the prediction process that is executed in step S1051 is not performed because the B picture is rearranged and the prediction process is performed. Is not appropriate.

On the other hand, when it is determined in step S1053 that the encoding target picture α is not a B picture, that is, when it is determined that the encoding target picture α is an I picture, the process proceeds to step S1056 to determine the complexity of the I picture β. Based on the index Xi [β], the screen variance total value var [β] of the I picture β, and the screen variance total value var [α] of the encoding target picture α that is an I picture,
Xi [α] = Xi [β] × (var [α] / var [β])
The complexity index Xi [α] when the encoding target picture α that is an I picture is encoded is predicted according to the following calculation formula.

  Subsequently, in step S1057, the predicted complexity index Xi [α] is set as the complexity index Xi used in Expression (3), and the encoding target picture α is selected from the complexity indices X read from the memory. The complexity index Xp of the P picture encoded before and last and the complexity index Xb of the B picture encoded last and before the encoding target picture α are extracted and their complexity is extracted. The target code amount Ti is determined according to the above-described equation (3) using the depth index Xi, Xp, Xb and the above-described Ni, Np, Nb.

  When the process of step S105 is completed by executing the flowchart of FIG. 4 in this way, subsequently, in step S106, the quantization step is set according to the determined target code amount T, and the encoding target picture α is encoded. Turn into.

  Subsequently, in step S107, the code amount S generated by the encoding of the encoding target picture α is measured. Subsequently, in step S108, the remaining code amount R is updated by subtracting the generated code amount S from the remaining code amount R.

  Subsequently, in step S109, an average value aveQ of the quantization step Q used for encoding the encoding target picture α is calculated. Subsequently, in step S110, the complexity index X of the encoding target picture α is calculated according to “X = S × aveQ”, and is written in the memory.

  Subsequently, in step S111, it is determined whether or not the GOP has ended. When determining that the GOP has not ended, the process returns to step S101. When determining that the GOP has ended, The process returns to step S100 to process the GOP.

  FIG. 5 illustrates a device configuration of the video encoding device 1 of the present embodiment that executes this processing. Here, the same components as those shown in FIG. 15 are denoted by the same symbols.

  As shown in FIG. 5, unlike the prior art shown in FIG. 15, this embodiment includes an encoded I picture variance value memory 301, and the encoding unit 100 further includes a macroblock variance value calculation unit. 113, the rate control unit 200 further includes a picture variance value calculation unit 208 and an I picture complexity index correction unit 209, and the rate control unit 200 further includes the target code amount calculation unit 203 illustrated in FIG. A target code amount calculation unit 203x that executes different processing is provided.

  The encoded I picture variance value memory 301 stores the screen variance total value var [β] of the I picture β that has been encoded.

  The macroblock variance value calculation unit 113 calculates the variance value of the encoding target macroblock.

  The picture variance value calculation unit 208 calculates the screen variance total value var [α] of the encoding target picture α by aggregating the variance values calculated by the macroblock variance value calculation unit 113.

  The I picture complexity index correction unit 209 includes the complexity index Xi [β] of the I picture β read from the encoded picture complexity index memory 300 and the I picture β read from the encoded I picture variance value memory 301. When the encoding target picture α is a P picture based on the screen dispersion total value var [β] of the image and the screen dispersion total value var [α] of the encoding target picture α calculated by the picture distribution value calculation unit 208 Predicts the complexity index Xi [α] that the encoding target picture α will have if it is an I picture, and if the encoding target picture α is an I picture, the complexity index Xi [ α] is predicted.

  Based on the complexity index Xi [α] predicted by the I picture complexity index correction unit 209 and the complexity index X read from the encoded picture complexity index memory 300, the target code amount calculation unit 203x The target code amount T of the encoding target picture α is calculated by executing the flowchart of FIG.

  The video encoding apparatus 1 according to the present embodiment executes the flowcharts of FIGS. 3 and 4 according to the configuration of FIG. 5 to determine the complexity of the I picture when determining the target code amount of the encoding target picture α. With respect to the length index, processing is performed so as to use the complexity index Xi [α] at the time of the picture to be encoded α predicted using the change in the screen variance total value.

  According to this configuration, according to the video encoding device 1 of the present embodiment, the prediction accuracy of the target code amount of the encoding target picture α is increased, and even when encoding video in which the difficulty of the image gradually changes, Encoding control can be stabilized and deterioration of image quality can be prevented.

[2] Second Embodiment Next, a method for determining a target code amount of a picture to be encoded according to a second embodiment of the present invention will be described with reference to FIG.

In this embodiment example,
(B) The behavior indicated by the complexity index of the image is similar to the behavior indicated by the total screen variance,
(B) If the picture to be coded is represented as picture α, and the I picture coded before and at the end of the picture to be coded is represented as picture β, the screen variance total value can be calculated for picture β. (C) If the I picture to be encoded first after the picture to be encoded is represented as picture γ, the picture up to picture γ is pre-read, and picture γ is displayed on the screen. Focusing on the fact that the variance total value can be calculated, the complexity index Xi [β] of picture β, the screen variance total value var [β] of picture β, and the screen variance total value var [γ of picture γ ], The complexity index Xi [γ] of the picture γ is
Xi [γ] = Xi [β] × (var [γ] / var [β])
Thus, instead of the complexity index Xi shown in the equations (1) to (3) used in the prior art for determining the target code amount of the encoding target picture α, the predicted Xi [γ] is The configuration is to use.

  7 and 8 show flowcharts executed by the rate control unit 200 configured in the present embodiment.

  Next, the target code amount determination process of the encoding target picture α executed by the present embodiment will be described with reference to the flowcharts of FIGS. 7 and 8.

  According to the present embodiment, as shown in the flowchart of FIG. 7, the rate control unit 200 first enters the GOP picture number (gopN) and 1 when the encoding of the first picture of the GOP starts in step S200. Multiply by the average code amount per picture to calculate the total target code amount of the GOP to be encoded, and add the remaining code amount in the previous GOP to the calculated total target code amount Thus, the remaining code amount R of the GOP to be encoded is obtained.

  Subsequently, in step S201, the encoding target picture α is selected according to the order from the first picture of the GOP.

  Subsequently, in step S202, a screen variance total value var [γ] of a picture γ to be encoded next as an I picture is calculated. Since the picture γ is prefetched, the screen variance total value var [γ] of the picture γ being prefetched is calculated.

  Subsequently, in step S203, the screen variance total value var [β] and the complexity index Xi [β] of the I picture β encoded before and at the end of the encoding target picture α are read from the memory. Since the I picture β is encoded before the encoding target picture α, the screen dispersion total value var [β] and the complexity index Xi [β] are calculated and stored in the memory. They are read from memory.

Subsequently, in step S204, based on the complexity index Xi [β] of the I picture β, the screen variance total value var [β] of the I picture β, and the screen variance total value var [γ] of the picture γ,
Xi [γ] = Xi [β] × (var [γ] / var [β])
The complexity index Xi [γ] for encoding the picture γ, which is an I picture, is predicted according to the following calculation formula.

  Hereinafter, the picture γ that is an I picture may be referred to as an I picture γ for simplicity.

  Subsequently, in step S205, the complexity index X of pictures of various encoded picture types is read from the memory.

  Subsequently, in step S206, the target code amount T of the encoding target picture α is calculated using the predicted complexity index Xi [γ], the complexity index X read from the memory, and Ni, Np, Nb described above. decide.

  That is, when the process of step S206 is entered, as shown in the flowchart of FIG. 8, first, in step S2060, it is determined whether or not the encoding target picture α is a P picture. Is determined to be a P picture, the process proceeds to step S2061, where the complexity index Xi [γ] predicted in step S204 is set as the complexity index Xi used in equation (1), and the complexity read out from the memory is set. The complexity index Xp of the P picture encoded last and before the encoding target picture α and the complexity of the B picture encoded last and before the encoding target picture α from the length index X The depth index Xb is extracted, and the target code amount Tp is calculated according to the above-described equation (1) using the complexity index Xi, Xp, Xb and the above-described Ni, Np, Nb. decide.

  On the other hand, when it is determined in step S2061 that the encoding target picture α is not a P picture, the process proceeds to step S2062 to determine whether or not the encoding target picture α is a B picture. When determining that the picture is a B picture, the process proceeds to step S2063, where the complexity index Xi [γ] predicted in step S204 is set as the complexity index Xi used in equation (2), and the complexity read from the memory is set. Of the index X, the complexity index Xp of the P picture encoded last and before the encoding target picture α and the complexity of the B picture encoded last and before the encoding target picture α The index Xb is extracted, and the complexity code Xi, Xp, Xb and the above-described Ni, Np, Nb are used, and the target code amount according to the above-described equation (2). Tb is determined.

  On the other hand, when it is determined in step S2062 that the encoding target picture α is not a B picture, that is, when it is determined that the encoding target picture α is an I picture, the process proceeds to step S2064 and the complex predicted in step S204 is performed. The length index Xi [γ] is set as the complexity index Xi used in the expression (3), and P encoded before and finally from the encoding target picture α is read out from the complexity index X read from the memory. The complexity index Xp of the picture and the complexity index Xb of the B picture encoded before and at the end of the picture α to be encoded are extracted, and the complexity index Xi, Xp, Xb and the above-described Ni , Np, Nb and the target code amount Ti is determined according to the above-described equation (3).

  In this way, by executing the flowchart of FIG. 8, when the processing of step S206 is completed, subsequently, in step S207, the quantization step is set according to the determined target code amount T, and the encoding target picture α is set. Encode.

  Subsequently, in step S208, the code amount S generated by encoding the encoding target picture α is measured. Subsequently, in step S209, the remaining code amount R is updated by subtracting the generated code amount S from the remaining code amount R.

  Subsequently, in step S210, an average value aveQ of the quantization step Q used for encoding the encoding target picture α is calculated. Subsequently, in step S211, the complexity index X of the encoding target picture α is calculated according to “X = S × aveQ”, and is written in the memory.

  Subsequently, in step S212, it is determined whether or not the GOP has ended. When it is determined that the GOP has not ended, the process returns to step S201. When it is determined that the GOP has ended, The process returns to step S200 to process the GOP.

  FIG. 9 illustrates a device configuration of the video encoding device 1 of the present embodiment that executes this processing. Here, the same components as those shown in FIG. 15 are denoted by the same symbols.

  As shown in FIG. 9, the present embodiment includes an encoded I picture variance value memory 301, a frame memory 400, and a picture variance precedence calculation unit 500, unlike the prior art shown in FIG. The rate control unit 200 includes a picture variance value calculation unit 208y and an I picture complexity index correction unit 209y, and the rate control unit 200 executes processing different from the target code amount calculation unit 203 illustrated in FIG. A target code amount calculation unit 203y is provided.

  The encoded I picture variance value memory 301 stores the screen variance total value var [β] of the I picture β that has been encoded.

  The frame memory 400 realizes prefetching of the picture γ by delaying the input image input to the encoding unit 100.

  The picture distribution advance calculation unit 500 inputs an input image input to the frame memory 400 in a pre-read form, and divides the input image into macro blocks, and the macro block division unit 501 A macroblock distribution preceding calculation unit 502 that calculates a distribution value of the divided macroblocks.

  The picture variance value calculation unit 208y calculates the screen variance total value var [γ] of the I picture γ preceding the encoding target picture α by aggregating the variance values calculated by the macroblock variance precedence calculation unit 502.

  The I picture complexity index correction unit 209y reads the complexity index Xi [β] of the I picture β read from the encoded picture complexity index memory 300 and the I picture β read from the encoded I picture variance value memory 301. Complexity index Xi [γ for encoding picture γ based on the total screen variance value var [β] of picture γ and the total screen variance value var [γ] of picture γ calculated by the picture variance value calculation unit 208y ].

  Based on the complexity index Xi [γ] predicted by the I picture complexity index correction unit 209y and the complexity index X read from the encoded picture complexity index memory 300, the target code amount calculation unit 203y The target code amount T of the encoding target picture α is calculated by executing the flowchart of FIG.

  The video encoding apparatus 1 according to the present embodiment executes the flowcharts of FIGS. 7 and 8 according to the configuration of FIG. 9 to determine the complexity of the I picture when determining the target code amount of the encoding target picture α. For the depth index, processing is performed so as to use the complexity index Xi [γ] of the future I picture γ predicted using the change in the total screen variance.

  According to this configuration, according to the video encoding device 1 of the present embodiment, the prediction accuracy of the target code amount of the encoding target picture α is increased, and even when encoding video in which the difficulty of the image gradually changes, Encoding control can be stabilized and deterioration of image quality can be prevented.

[3] Results of Experiments Performed to Verify the Effectiveness of the Present Invention FIGS. 10 and 11 are performed assuming that a gray image is faded to a moving image in order to verify the effectiveness of the present invention. The experimental results are illustrated.

  FIG. 10 shows the experimental results when using the first embodiment, and FIG. 11 shows the experimental results when using the conventional technique.

  Here, the horizontal axis indicates the frame number of the video faded from the gray image with frame number 0 to the moving image, and the vertical axis indicates the complexity index value and the screen dispersion total value.

  As can be seen from a comparison between FIG. 10 and FIG. 11, in the prior art, since the complexity index of the I picture when the I picture was last encoded is used, the movement of the complexity index is the movement of the screen variance total value. On the other hand, in the present invention, since the complexity index of the I picture when the I picture is encoded last is corrected in the P picture period, the movement of the complexity index is distributed on the screen. You can keep up with the movement of the total value. From this experimental result, the effectiveness of the present invention could be confirmed.

  The present invention can be applied to video coding control for determining the target code amount of a picture to be coded based on the complexity index, and the prediction accuracy of the target code quantity of the picture to be coded is improved, and the difficulty of the image is increased. Even in the case of encoding a video in which the gradual change occurs, the encoding control is stable and it is possible to prevent the deterioration of the image quality.

It is an apparatus block diagram of the video coding apparatus with which this invention is applied. It is explanatory drawing of the example of 1st Embodiment. 3 is a flowchart executed by the first embodiment. 3 is a flowchart executed by the first embodiment. 1 is a device configuration diagram of a video encoding device according to a first embodiment. FIG. It is explanatory drawing of the example of 2nd Embodiment. It is a flowchart which a 2nd embodiment example performs. It is a flowchart which a 2nd embodiment example performs. It is an apparatus block diagram of the video encoding apparatus of 2nd Example. It is explanatory drawing of the experimental result performed in order to verify the effectiveness of this invention. It is explanatory drawing of the experimental result performed in order to verify the effectiveness of this invention. It is explanatory drawing of a prior art. It is a flowchart which the conventional video coding apparatus performs. It is a flowchart which the conventional video coding apparatus performs. It is an apparatus block diagram of the conventional video coding apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Video coding apparatus 100 Encoding part 200 Rate control part 201 Remaining IPB number update part 202 GOP remaining code amount update part 203x Target code amount calculation part 204 Macroblock quantization step calculation part 205 Picture generation code amount calculation part 206 Picture average Quantization step calculation unit 207 Complexity index calculation unit 208 Picture variance value calculation unit 209 I picture complexity index correction unit 300 Encoded picture complexity index memory 301 Encoded I picture variance value memory

Claims (12)

Based on the number of pictures of each picture type included in the predetermined number of pictures to be encoded and the complexity index of the picture type of each picture type encoded before and at the end of the picture to be encoded A video encoding control device for determining a target code amount of a picture,
Calculating means for calculating a screen feature amount of the encoding target picture;
By correcting the complexity index of the I picture based on the screen feature value calculated by the calculating means and the screen feature value of the I picture encoded before and at the end of the encoding target picture, Setting means for setting a complexity index of an I picture used to determine a target code amount of a picture to be converted;
Using a complexity index set by the setting means, and determining means for determining a target code amount of a picture to be encoded.
A video encoding control device. The video encoding control apparatus according to claim 1,
The calculation means calculates a screen variance total value as the screen feature value,
The setting means calculates the complexity index of the I picture based on the screen variance total value calculated by the calculation means and the screen variance total value of the I picture encoded before and at the end of the encoding target picture. To set
A video encoding control device. The video encoding control apparatus according to claim 1 or 2,
When the encoding target picture is a B picture,
The setting means does not correct the complexity index of the I picture used to determine the target code amount of the encoding target picture,
The determination means determines the target code amount of the P picture encoded before and last to the encoding target picture as the complexity index of the I picture used for determining the target code amount of the encoding target picture. To decide to use the complexity index of the I picture used in
A video encoding control device. Based on the number of pictures of each picture type included in the predetermined number of pictures to be encoded and the complexity index of the picture type of each picture type encoded before and at the end of the picture to be encoded A video encoding control device for determining a target code amount of a picture,
Calculating means for calculating a screen feature amount of an I picture to be encoded first after the encoding target picture;
By correcting the complexity index of the I picture based on the screen feature value calculated by the calculating means and the screen feature value of the I picture encoded before and at the end of the encoding target picture, Setting means for setting a complexity index of an I picture used to determine a target code amount of a picture to be converted;
Using a complexity index set by the setting means, and determining means for determining a target code amount of a picture to be encoded.
A video encoding control device. The video encoding control apparatus according to claim 4, wherein
The calculation means calculates a screen variance total value as the screen feature value,
The setting means calculates the complexity index of the I picture based on the screen variance total value calculated by the calculation means and the screen variance total value of the I picture encoded before and at the end of the encoding target picture. To set
A video encoding control device. Based on the number of pictures of each picture type included in the predetermined number of pictures to be encoded and the complexity index of the picture type of each picture type encoded before and at the end of the picture to be encoded A video encoding control method for determining a target code amount of a picture, comprising:
A process of calculating the screen feature of the encoding target picture;
By correcting the complexity index of the I picture based on the calculated screen feature quantity and the screen feature quantity of the I picture encoded before and at the end of the encoding target picture, the encoding target picture is corrected. Setting a complexity index of an I picture used to determine a target code amount of
Using the set complexity index to determine a target code amount of a picture to be encoded.
A characteristic video encoding control method. The video encoding control method according to claim 6, wherein
In the calculating process, a screen dispersion total value is calculated as the screen feature amount,
In the setting process, the complexity index of the I picture is set based on the calculated screen variance total value and the screen variance total value of the I picture encoded last and before the encoding target picture. That
A characteristic video encoding control method. In the video encoding control method according to claim 6 or 7,
When the encoding target picture is a B picture,
In the setting process, the complexity index of the I picture used for determining the target code amount of the encoding target picture is not corrected,
In the determining process, as the complexity index of the I picture used to determine the target code amount of the encoding target picture, the target code amount of the P picture encoded last and before the encoding target picture is determined. Deciding to use the complexity index of the I picture used in the
A characteristic video encoding control method. Based on the number of pictures of each picture type included in the predetermined number of pictures to be encoded and the complexity index of the picture type of each picture type encoded before and at the end of the picture to be encoded A video encoding control method for determining a target code amount of a picture, comprising:
A process of calculating a screen feature amount of an I picture to be encoded first after the encoding target picture;
By correcting the complexity index of the I picture based on the calculated screen feature quantity and the screen feature quantity of the I picture encoded before and at the end of the encoding target picture, the encoding target picture is corrected. Setting a complexity index of an I picture used to determine a target code amount of
Using the set complexity index to determine a target code amount of a picture to be encoded.
A characteristic video encoding control method. The video encoding control method according to claim 9, wherein
In the calculating process, a screen dispersion total value is calculated as the screen feature amount,
In the setting process, the complexity index of the I picture is set based on the calculated screen variance total value and the screen variance total value of the I picture encoded last and before the encoding target picture. That
A characteristic video encoding control method.   6. A video encoding control program for causing a computer to function as means constituting the video encoding control apparatus according to claim 1.   A computer-readable recording medium having recorded thereon a video encoding control program for causing a computer to function as means for constituting the video encoding control device according to any one of claims 1 to 5.

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