JP5969408B2 - Video compression format conversion apparatus, video compression format conversion method, and program - Google Patents

Description

  The present invention relates to a video compression format conversion device, a video compression format conversion method, and a program.

  Research and development on high-performance video compression technology is ongoing worldwide. New technologies are being standardized every few years as international standards for video compression technology.

  Recently, in 2003, H.C. H.264 (for example, see Non-Patent Document 1) has been standardized and is becoming widespread. However, in the field of international standardization, HEVC (for example, see Non-Patent Document 2) is being discussed as a new compression technique.

  H. Although a similar technique is used between different compression schemes such as H.264 and HEVC, there are cases where there is no compatibility as a format of compressed data. For example, H.C. Both H.264 and HEVC are based on motion compensation and orthogonal transform (discrete cosine transform), but there is no compatibility with respect to the format.

  For this reason, when a new video compression method becomes widespread, video contents having different compression data formats are mixed. Therefore, there is a need for a format conversion technique for converting video content from an old compressed data format to a new compressed data format.

Joint Video Team (JVT) of ISO / IEC MPEG and ITU-T VCEG, "Text of ISO / IEC 14496-10 Advanced Video Coding," High Efficiency Video Coding (HEVC) text specification draft 6, JCTVC-H1003 ISO / IEC MPEG and ITU-T VCEG, "Text of ISO / IEC 13818-2 Generic coding of moving pictures and associated audio information: Video," 2000.

  The conventional format conversion technique is a technique that assumes a case where the unit block size of the encoding process is the same before and after conversion.

  For example, MPEG-2 (for example, see Non-Patent Document 3) and H.264. In H.264, the unit block size of the encoding process is the same. For this reason, video content is changed from MPEG-2 to H.264. When converting to H.264, since the encoding processing blocks to be converted correspond one-to-one, it is easy to use the encoding information before conversion for the compression processing after conversion, and the conventional format conversion technology is applied. It was possible to do.

  However, H.C. When the unit block size of the encoding process is larger after the conversion than before the conversion like H.264 to HEVC, if the encoded information before the conversion is simply used for the compression process after the conversion as described above. In some cases, an appropriate prediction block size or conversion block size cannot be selected, and the image quality deteriorates.

  In order to suppress the above-described deterioration in image quality, it is necessary to appropriately determine the predicted block size after conversion and the converted block size.

  When determining the prediction block size and conversion block size after conversion, it is conceivable to apply the prediction block size and conversion block size before conversion as the prediction block size and conversion block size after conversion. However, in this case, the predicted block size after conversion and the upper limit value of the conversion block size are the maximum values of the prediction block size and conversion block size before conversion. Here, in coding in which a large unit block is allowed, such as HEVC, high coding performance is obtained by applying as large a predicted block size and transform block size as possible in a region where the characteristics of the video signal are similar. be able to. For this reason, if the prediction block size before conversion and the conversion block size are simply applied as the prediction block size and conversion block size after conversion, the upper limit of the prediction block size and conversion block size after conversion is limited, and a high code Performance could not be obtained.

  Further, when determining the predicted block size after conversion and the conversion block size, it is conceivable to calculate the cost value when applied for each of all the block sizes applicable as the block size after conversion. According to this, since the prediction block size and conversion block size after conversion can be determined according to a cost value, the prediction block size and conversion block size after conversion can be determined appropriately. However, since the cost value is calculated for all block sizes applicable as the converted block size, the processing cost required for converting the video format has been increased.

  Therefore, the present invention has been made in view of the above-described problems, and even after a compression method in which the unit block size of the encoding process is larger after the conversion than before the conversion, the image quality is reduced. An object of the present invention is to provide a video compression format conversion device, a video compression format conversion method, and a program capable of realizing suppression, improvement of encoding performance, and reduction of processing cost required for conversion.

The present invention proposes the following matters in order to solve the above problems.
(1) The present invention is a second size in which the unit block size of the encoding process is larger than the first size from the first compression method in which the unit block size of the encoding process is the first size. A video compression format conversion device (for example, the video compression format conversion device 1 in FIG. 1, the video compression format conversion device 1A in FIG. 10, or the video compression format in FIG. 14) converts the video compression format into the second compression method. Between the prediction blocks adjacent to each other before conversion based on the characteristics of the video signal in each prediction block before conversion (e.g., corresponding to a motion vector described later or a pixel value described later). Similarity calculation means for calculating the similarity of the video signals of (for example, the MV similarity calculation unit 211 in FIG. 4 and the MV similarity calculation unit 211 in FIG. 12), Similarity determination means for determining the similarity of video signals between the prediction blocks adjacent to each other before the conversion based on the calculation result by the similarity calculation means (for example, the MV similarity determination unit 212 in FIG. 12 MV similarity determination unit 222) and block size determination means for determining a block size after conversion (e.g., corresponding to a PU size or TU size described later) based on the determination result by the similarity determination means (For example, equivalent to the PU size determination unit 213 in FIG. 4 and the TU size determination unit 223 in FIG. 12) has been proposed.

  According to this invention, from the first compression method in which the unit block size of the encoding process is the first size, the second unit block size of the encoding process is the second size larger than the first size. In the video compression format conversion apparatus for converting the video compression format to the compression method, similarity calculation means, similarity determination means, and block size determination means are provided. Further, the similarity calculation means calculates the similarity of the video signal between the prediction blocks adjacent to each other before the conversion based on the characteristics of the video signal in each prediction block before the conversion, and the similarity determination means calculates the similarity. Based on the calculation result by the calculation means, the similarity of the video signals between the prediction blocks adjacent to each other before the conversion is determined. Further, the block size determination unit determines the block size after conversion based on the determination result by the similarity determination unit.

  For this reason, it is possible to determine a region where the features of the video signal are similar based on the signal features in each prediction block before conversion, and to determine the block size after conversion based on the determination result. Therefore, the video compression format can be converted while suppressing a decrease in image quality even between compression methods in which the unit block size of the encoding process is larger after conversion than before conversion.

  Further, as described above, based on the signal features in each prediction block before conversion, it is possible to determine a region where the features of the video signal are similar, and to determine the block size after conversion based on the determination result. For this reason, it is possible to apply a prediction block size and a transform block size that are as large as possible in a region where the characteristics of the video signal are similar, so that the encoding performance can be improved.

  Further, as described above, based on the signal features in each prediction block before conversion, it is possible to determine a region where the features of the video signal are similar, and to determine the block size after conversion based on the determination result. For this reason, the block size after conversion can be determined without calculating the cost value when applied for each of all the block sizes applicable as the block size after conversion. Therefore, the processing cost required for converting the video compression format can be reduced.

  (2) In the video compression format conversion apparatus according to (1), the similarity calculation unit calculates the similarity of the video signal based on a motion vector in each prediction block before conversion. The video compression format converter is proposed.

  According to the present invention, in the video compression format conversion apparatus of (1), the similarity calculation means calculates the similarity of the video signal based on the motion vector in each prediction block before conversion. For this reason, the block size after conversion can be determined using the motion vector in the prediction block before conversion.

  (3) The present invention relates to the video compression format conversion apparatus according to (1) or (2), wherein the similarity calculation means uses the distance between motion vectors between adjacent prediction blocks before conversion to perform the prediction. A video compression format conversion device is proposed that calculates the similarity of video signals between blocks.

  According to the present invention, in the video compression format conversion device according to (1) or (2), the similarity calculation means uses the distance between motion vectors between adjacent prediction blocks before conversion to convert between these prediction blocks. It was decided to calculate the similarity of the video signal. For this reason, the block size after conversion can be determined using the distance between motion vectors between the prediction blocks adjacent to each other before conversion.

  (4) In the video compression format conversion apparatus according to (1), the similarity calculation unit calculates the similarity of the video signal based on a pixel value in each prediction block before conversion. The video compression format converter is proposed.

  According to the present invention, in the video compression format conversion apparatus of (1), the similarity calculation means calculates the similarity of the video signal based on the pixel value in each prediction block before conversion. For this reason, the block size after conversion can be determined using the pixel value in each prediction block before conversion.

  (5) In the video compression format conversion device according to any one of (1) to (4), the block size determination unit includes a predicted block size after conversion and a converted block size as the converted block size. The video compression format conversion device is characterized in that either one of the conversion block size or the conversion block size is determined.

  According to the present invention, in the video compression format conversion device according to any one of (1) to (4), the block size determination unit converts the predicted block size after conversion and the converted block after conversion as the block size after conversion. One of the size and the size was decided. For this reason, the prediction block size after conversion or the conversion block size after conversion can be determined using the characteristics of the video signal in each prediction block before conversion.

  (6) The present invention relates to the video compression format conversion device according to any one of (1) to (5), wherein the block size determination unit includes a predicted block size after conversion and a converted block size as the converted block size. The video compression format conversion device is characterized in that both the conversion block size and the conversion block size are determined.

  According to the present invention, in the video compression format conversion device according to any one of (1) to (5), the block size determining unit converts the predicted block size after conversion and the converted block after conversion as the block size after conversion. Both size and size were decided. For this reason, both the prediction block size after conversion and the conversion block size after conversion can be determined using the characteristic of the video signal in each prediction block before conversion.

(7) In the video compression format conversion apparatus according to (6), the similarity determination unit includes the similarity of video signals between prediction blocks adjacent to each other before conversion calculated by the similarity calculation unit. _Are compared with predetermined threshold values (e.g., corresponding to threshold values T _PU and T _TU described later), the similarity between the prediction blocks is determined based on the comparison result, and the conversion is performed by the block size determination unit. A video compression format conversion device using a value that is independent of each other as a threshold value when determining a subsequent predicted block size and when determining a converted block size after conversion by the block size determination unit Has proposed.

  According to the present invention, in the video compression format conversion apparatus of (6), the similarity determination unit determines in advance the similarity of the video signal between the prediction blocks adjacent to each other before conversion calculated by the similarity calculation unit. The determined threshold values are compared, and the similarity between the prediction blocks is determined based on the comparison result. In addition, independent values are used as threshold values when the predicted block size after conversion is determined by the block size determination means and when the converted block size after conversion is determined by the block size determination means. For this reason, optimal threshold values can be used for the predicted block size after conversion and the conversion block size after conversion, respectively, and the above-described effects can be more effectively achieved.

  (8) The present invention relates to similarity calculation means (for example, the MV similarity calculation section 211 in FIG. 4 or MV similarity calculation section 211 in FIG. 12), similarity determination means (for example, MV similarity in FIG. 4). And a block size determining means (for example, equivalent to the PU size determining unit 213 in FIG. 4 and the TU size determining unit 223 in FIG. 12). From the first compression method in which the unit block size of the encoding process is the first size, to the second compression method in which the unit block size of the encoding process is a second size larger than the first size. , A video compression format converter for converting the video compression format (for example, the video compression format converter 1 in FIG. 1, the video compression format converter 1A in FIG. 10, and the video compression format in FIG. 14). A video compression format conversion method in the mat conversion device 1B), in which the similarity calculation unit corresponds to a feature (for example, a motion vector described later or a pixel value described later) in each prediction block before conversion. ) Based on the first step (for example, corresponding to the processing of step S1 in FIG. 9 or the processing of step S11 in FIG. 13) for calculating the similarity of video signals between adjacent prediction blocks before conversion A second step (for example, step of FIG. 9) in which the similarity determination unit determines the similarity of video signals between the prediction blocks adjacent to each other before the conversion based on the calculation result in the first step. S2 and the processing in step S12 in FIG. 13) and the block size determination means change the values based on the determination result in the second step. A third step (for example, corresponding to the processing in step S5 in FIG. 9 or the processing in step S15 in FIG. 13) for determining the block size after replacement (for example, corresponding to a PU size or a TU size described later), The video compression format conversion method characterized by comprising is proposed.

  According to this invention, the similarity calculation means calculates the similarity of the video signal between the prediction blocks adjacent to each other before the conversion based on the characteristics of the video signal in each prediction block before the conversion, and the similarity determination means Thus, the similarity of the video signals between the prediction blocks adjacent to each other before the conversion is determined based on the calculation result by the similarity calculation means. Further, the block size determination unit determines the block size after conversion based on the determination result by the similarity determination unit. For this reason, the effect similar to the effect mentioned above can be produced.

  (9) The present invention relates to similarity calculation means (for example, the MV similarity calculation section 211 in FIG. 4 and MV similarity calculation section 211 in FIG. 12), similarity determination means (for example, MV similarity in FIG. 4). And a block size determining means (for example, equivalent to the PU size determining unit 213 in FIG. 4 and the TU size determining unit 223 in FIG. 12). From the first compression method in which the unit block size of the encoding process is the first size, to the second compression method in which the unit block size of the encoding process is a second size larger than the first size. , A video compression format converter for converting the video compression format (for example, the video compression format converter 1 in FIG. 1, the video compression format converter 1A in FIG. 10, and the video compression format in FIG. 14). This is a program for causing a computer to execute the video compression format conversion method in the mat conversion device 1B), wherein the similarity calculation means is characterized by the video signal in each prediction block before the conversion (for example, a motion described later) A first step (for example, the process of step S1 in FIG. 9 or the process of FIG. 13) calculates the similarity of video signals between prediction blocks adjacent to each other before conversion based on a vector or a pixel value described later. And the similarity determination unit determines the similarity of the video signals between the prediction blocks adjacent to each other before the conversion based on the calculation result in the first step. (For example, the process of step S2 in FIG. 9 or the process of step S12 in FIG. 13) and the block size determining means Based on the determination result in the second step, a third step (for example, the process in step S5 in FIG. 9 or the process in FIG. Is equivalent to the process of step S15), and a program for causing a computer to execute is proposed.

  According to the present invention, by executing the program using a computer, the similarity calculation means causes the video signal between adjacent prediction blocks before conversion based on the characteristics of the video signal in each prediction block before conversion. The similarity determination unit determines the similarity of the video signals between the prediction blocks adjacent to each other before the conversion based on the calculation result by the similarity calculation unit. Further, the block size determination unit determines the block size after conversion based on the determination result by the similarity determination unit. For this reason, the effect similar to the effect mentioned above can be produced.

  According to the present invention, it is possible to suppress deterioration in image quality, improve encoding performance, and perform conversion even between compression methods in which the unit block size of the encoding process is larger after conversion than before conversion. It is possible to reduce the processing cost required.

1 is a block diagram of a video compression format conversion apparatus according to a first embodiment of the present invention. It is a block diagram of the pre-conversion decoding process part provided in the said video compression format converter. It is a block diagram of the conversion process part provided in the said video compression format converter. It is a block diagram of the 2nd predicted value generation part provided in the above-mentioned conversion processing part. It is a figure for demonstrating operation | movement of a said 2nd predicted value production | generation part. It is a figure for demonstrating operation | movement of a said 2nd predicted value production | generation part. It is a figure for demonstrating operation | movement of a said 2nd predicted value production | generation part. It is a figure for demonstrating operation | movement of a said 2nd predicted value production | generation part. It is a flowchart of a said 2nd predicted value production | generation part. It is a block diagram of the video compression format conversion apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram of the conversion process part provided in the said video compression format converter. It is a block diagram of the DCT / quantization part provided in the said conversion process part. It is a flowchart of the said DCT / quantization part. It is a block diagram of the video compression format conversion apparatus which concerns on 3rd Embodiment of this invention. It is a block diagram of the conversion process part provided in the said video compression format converter.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the constituent elements in the following embodiments can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. Accordingly, the description of the following embodiments does not limit the contents of the invention described in the claims.

<First Embodiment>
[Configuration and Operation of Video Compression Format Conversion Apparatus 1]
FIG. 1 is a block diagram of a video compression format conversion apparatus 1 according to the first embodiment of the present invention. The video compression format conversion device 1 converts the pre-conversion compressed data a into post-conversion compressed data b of a compression method in which the unit block size of the encoding process is larger than the pre-conversion compressed data a. The video compression format conversion apparatus 1 includes a pre-conversion decoding processing unit 10 and a conversion processing unit 20.

(Configuration and operation of pre-conversion decoding processor 10)
FIG. 2 is a block diagram of the pre-conversion decoding processing unit 10. The pre-transform decoding processing unit 10 includes an entropy decoding unit 11, a first predicted value generation unit 12, an inverse DCT / inverse quantization unit 13, and a local memory 14.

  The entropy decoding unit 11 receives the pre-conversion compressed data a as an input. The entropy decoding unit 11 performs entropy decoding on the pre-conversion compressed data a, and extracts and outputs the prediction information c and the residual signal e for each pre-conversion unit block that is a unit block for encoding processing before conversion. .

  The first predicted value generation unit 12 receives the prediction information c and a later-described decoded video d output from the local memory 14. The first predicted value generation unit 12 generates and outputs a predicted value f from the decoded video d for each pre-conversion unit block according to the prediction information c.

  The inverse DCT / inverse quantization unit 13 receives the residual signal e. The inverse DCT / inverse quantization unit 13 performs an inverse DCT process and an inverse quantization process on the residual signal e for each unit block before conversion, and outputs the result as an inverse DCT and an inversely quantized residual signal g. To do.

  The predicted value f output from the first predicted value generation unit 12 and the residual signal g output from the inverse DCT / inverse quantization unit 13 are added by an adder for each unit block before conversion and decoded. The video d is output from the pre-conversion decoding processing unit 10.

  The local memory 14 receives the decoded video d. The local memory 14 stores the input decoded video d and supplies it to the first predicted value generation unit 12 as appropriate.

(Configuration and operation of conversion processing unit 20)
FIG. 3 is a block diagram of the conversion processing unit 20. The transformation processing unit 20 includes a second predicted value generation unit 21, a DCT / quantization unit 22, an entropy encoding unit 23, an inverse DCT / inverse quantization unit 24, and a local memory 25.

  The second predicted value generation unit 21 receives a post-conversion local decoded video m, a prediction information c, and a decoded video d, which will be described later, output from the local memory 25. The second prediction value generation unit 21 converts the prediction unit (PU after conversion) so that the prediction accuracy is optimized based on the motion vector (MV) in each prediction block before conversion included in the prediction information c. : Prediction Unit) size is determined. And about each PU, while calculating | requiring the optimal prediction method and outputting it as the prediction information i, the prediction value by an optimal prediction method is calculated | required and it outputs as the prediction value h. As shown in FIG. 4, the second predicted value generation unit 21 includes an MV similarity calculation unit 211, an MV similarity determination unit 212, a PU size determination unit 213, and a unit predicted value generation unit 214.

  Based on the motion vector, the MV similarity calculation unit 211 calculates the similarity of video signals between prediction blocks adjacent to each other before conversion included in a region corresponding to a processing coding unit (CU) after conversion. Is calculated.

The similarity of video signals can be calculated using, for example, the distance between two motion vectors in two adjacent prediction blocks before conversion. Specifically, when the motion vector MV _A is expressed by the following formula (1) and the motion vector MV _B is expressed by the following formula (2), the motion vectors MV _A and MV _B The similarity S can be obtained by the following mathematical formula (3).

The MV similarity determination unit 212 determines the similarity of video signals between prediction blocks adjacent to each other before conversion based on the calculation result by the MV similarity calculation unit 211. Specifically, the similarity of the video signal calculated by the MV similarity calculation unit 211 is compared with a predetermined threshold value _TPU . When the similarity of the video signal calculated by the MV similarity calculation unit 211 is smaller than the threshold value T _PU , the similarity of the video signal between the two prediction blocks for which the similarity of the video signal is calculated is high. Then, it is determined that these two prediction blocks can be merged in the encoding after conversion. On the other hand, when the similarity of the video signal calculated by the MV similarity calculation unit 211 is equal to or greater than the threshold value _TPU , the similarity of the video signal between the two prediction blocks for which the similarity of the video signal is calculated. It is determined that it is impossible to merge these two prediction blocks in the encoding after conversion.

  Based on the determination result by the MV similarity determination unit 212, the PU size determination unit 213 determines the PU size so that the area per PU in encoding after conversion is maximized. Specifically, prediction blocks that are determined to be mergeable are combined so that the PU size becomes as large as possible among a plurality of predetermined PU sizes, and the PU size of each PU is determined.

  The operations of the MV similarity calculation unit 211, the MV similarity determination unit 212, and the PU size determination unit 213 will be described below with reference to FIGS. 5 to 8 by taking as an example the case where the converted CU size is 64 × 64. To do.

  FIG. 5 is a diagram illustrating the shape of each prediction block before conversion included in the area corresponding to the processed CU after conversion, and the motion vector in each prediction block. The MV similarity calculation unit 211 calculates the similarity of motion vectors between adjacent prediction blocks before conversion based on the motion vector in each prediction block before conversion.

  FIG. 6 is a diagram illustrating a determination result by the MV similarity determination unit 212. In FIG. 6, the broken line indicates that it is determined that two prediction blocks adjacent to each other across the broken line can be merged, and the solid line indicates that the two prediction blocks adjacent to each other across the solid line cannot be merged. This means that it was determined that it was possible.

  FIG. 7 is a diagram illustrating the PU size of each PU determined by the PU size determination unit 213. In FIG. 7, each rectangular block surrounded by a solid line represents each PU whose PU size has been determined by the PU size determination unit 213. The PU size determination unit 213 combines adjacent prediction blocks with a broken line in FIG. 6 so that the PU size is as large as possible among a plurality of predetermined PU sizes.

  The determination of the PU size will be described in detail with reference to FIG. FIG. 8 is a rewrite of FIG. In FIG. 8, all hatched portions are prediction blocks that are determined to be mergeable by the MV similarity determination unit 212. Combining all the prediction blocks represented by these diagonal lines most satisfies the above-mentioned condition that the PU size is as large as possible. However, the PU size when all prediction blocks represented by diagonal lines are combined is not predetermined in the PU size determination unit 213. For this reason, as shown in FIG. 7, each prediction block represented by hatching in FIG. 8 is preliminarily stored in the PU size determining unit 213 with a 32 × 32 PU size block and the PU size determining unit 213 in advance. The PU size is determined by combining the three blocks of 16 × 16 PU size defined.

  Returning to FIG. 4, the unit predicted value generation unit 214 executes a predicted value generation procedure, a cost value calculation procedure, and a prediction method determination procedure.

  In the prediction value generation procedure, the unit prediction value generation unit 214 calculates the prediction value in each of all prediction methods applicable to the conversion processing unit 20 for each PU whose PU size is determined by the PU size determination unit 213. It is generated from the decoded video d and the converted local decoded video m according to the prediction method. According to this, for each PU whose PU size is determined by the PU size determination unit 213, a prediction value is obtained for each prediction method to which the conversion processing unit 20 can be applied.

  In the cost value calculation procedure, the unit prediction value generation unit 214 generates coding distortion when each prediction method applicable to the transform processing unit 20 is applied to each PU whose PU size is determined by the PU size determination unit 213. The code amount is calculated based on the decoded video d, the converted local decoded video m, and the predicted value obtained in the predicted value generation procedure. According to this, for each PU whose PU size is determined by the PU size determination unit 213, a cost value is obtained for each prediction method to which the conversion processing unit 20 can be applied.

  In the prediction method determination procedure, the unit prediction value generation unit 214 determines, for each PU whose PU size has been determined by the PU size determination unit 213, the prediction method with the best cost value obtained in the cost value calculation procedure, as the optimal prediction method. Determine as. Then, for each PU whose PU size is determined by the PU size determination unit 213, information indicating an optimal prediction method is output as prediction information i, and a prediction value by the optimal prediction method is output as a prediction value h.

  The flowchart of the 2nd predicted value production | generation part 21 provided with the above structure is shown in FIG.

  The second predicted value generation unit 21 executes the following steps S1 to S4 for each predicted block before conversion included in the region corresponding to the converted process CU.

  In step S1, the second predicted value generation unit 21 uses the MV similarity calculation unit 211 to calculate the similarity of video signals between adjacent prediction blocks before conversion, and moves the process to step S2.

In step S2, the second predicted value generation unit 21 uses the MV similarity determination unit 212 to compare the similarity of the video signal calculated in step S1 with the threshold value _TPU . When the similarity of the calculated video signal is smaller than the threshold T _PU in step S1, the process proceeds to step S3, if the similarity of the video signal calculated in step S1 is the threshold value T _PU or more, The process moves to step S4.

  In step S3, the second predicted value generation unit 21 can merge the two prediction blocks whose similarity of the video signal has been determined in step S2 by the MV similarity determination unit 212 in the encoded encoding. to decide.

  In step S4, the second prediction value generation unit 21 cannot merge the two prediction blocks whose similarity is determined in the video signal in step S2 by the MV similarity determination unit 212 in the encoded encoding. Judge.

  When the second predicted value generation unit 21 executes the processes of steps S1 to S4 described above for each predicted block before conversion included in the area corresponding to the converted process CU, the process proceeds to step S5. .

  In step S5, the 2nd predicted value production | generation part 21 determines PU size based on the result in step S1-S4 by PU size determination part 213, and moves a process to step S6.

  In step S6, the second predicted value generation unit 21 uses the unit predicted value generation unit 214 to obtain an optimal prediction method and a predicted value based on the prediction method for each PU whose PU size has been determined in step S5. Then, the process shown in FIG.

  Returning to FIG. 3, the DCT / quantization unit 22 receives a difference signal (residual signal) between the predicted value h and the decoded video d. The DCT / quantization unit 22 appropriately determines an orthogonal transform block (transform unit (TU) size), performs DCT on the residual signal according to the determined TU size, and obtains a DCT coefficient. The DCT coefficient is quantized and output as a DCT and a quantized residual signal j.

  The entropy encoding unit 23 receives the prediction information i, the DCT, and the quantized residual signal j as inputs. The entropy encoding unit 23 performs variable length encoding or arithmetic encoding on the input information for each unit block after conversion, writes the result as a compressed data stream according to the encoding syntax, and compresses the converted information after the conversion. Output as data b.

  The inverse DCT / inverse quantization unit 24 receives the DCT and the quantized residual signal j as inputs. The inverse DCT / inverse quantization unit 24 performs inverse quantization processing and inverse DCT processing on the DCT and the quantized residual signal j for each unit block after conversion, and performs inverse quantization and inverse DCT. And output as a residual signal k.

  The local memory 25 receives the converted local decoded video m as an input. The post-conversion local decoded video m is addition information of the predicted value h and the residual signal k that has been subjected to inverse quantization and inverse DCT. The local memory 25 accumulates the input converted local decoded video m and supplies it to the second predicted value generation unit 21 as appropriate.

  According to the video compression format converter 1 described above, the following effects can be obtained.

  The video compression format conversion apparatus 1 determines an area where the characteristics of the video signal are similar based on the motion vector in each prediction block before conversion, and determines the PU size after conversion based on the determination result. Therefore, the video compression format can be converted while suppressing a decrease in image quality even between compression methods in which the unit block size of the encoding process is larger after conversion than before conversion.

  In addition, as described above, the video compression format conversion device 1 determines a region where the characteristics of the video signal are similar based on the motion vector in each prediction block before conversion, and the PU size after conversion based on the determination result To decide. For this reason, it is possible to apply a PU size that is as large as possible in a region where the features of the video signal are similar, so that the encoding performance can be improved.

  In addition, as described above, the video compression format conversion device 1 determines a region where the characteristics of the video signal are similar based on the motion vector in each prediction block before conversion, and the PU size after conversion based on the determination result To decide. For this reason, the PU size after conversion can be determined without calculating the cost value when applied for each of all PU sizes applicable as the PU size after conversion. Therefore, the processing cost required for converting the video compression format can be reduced.

Second Embodiment
[Configuration and Operation of Video Compression Format Conversion Apparatus 1A]
FIG. 10 is a block diagram of a video compression format conversion apparatus 1A according to the second embodiment of the present invention. The video compression format conversion device 1A differs from the video compression format conversion device 1 according to the first embodiment of the present invention shown in FIG. 1 in that a conversion processing unit 20A is provided instead of the conversion processing unit 20. In the video compression format conversion device 1A, the same components as those of the video compression format conversion device 1 are denoted by the same reference numerals and description thereof is omitted.

(Configuration and operation of conversion processing unit 20A)
FIG. 11 is a block diagram of the conversion processing unit 20A. The conversion processing unit 20A is different from the conversion processing unit 20 according to the first embodiment of the present invention shown in FIG. 3 in that a second prediction value generation unit 21A is provided instead of the second prediction value generation unit 21. The point that DCT / quantization part 22A is provided instead of DCT / quantization part 22 is different.

  The second predicted value generation unit 21A receives the converted local decoded video m and the decoded video d. The second predicted value generation unit 21A appropriately determines the PU size, and determines an optimal prediction method using the converted local decoded video m and the decoded video d for each PU for which the PU size has been determined. While outputting as information i, the predicted value by the optimal prediction method is output as predicted value h.

  The DCT / quantization unit 22A receives the difference signal (residual signal) between the predicted value h and the decoded video d and the prediction information c. The DCT / quantization unit 22A determines the TU size so that the coding performance is the highest based on the motion vector in each prediction block before conversion included in the prediction information c. Then, according to the determined TU size, DCT is performed on the residual signal to obtain a DCT coefficient, the quantization process is performed on the DCT coefficient, and the DCT and the quantized residual signal j are output. As shown in FIG. 12, the DCT / quantization unit 22 includes an MV similarity calculation unit 221, an MV similarity determination unit 222, a TU size determination unit 223, and a unit DCT / quantization unit 224.

  The MV similarity calculation unit 221 and the MV similarity determination unit 222 operate in the same manner as the MV similarity calculation unit 211 and the MV similarity determination unit 212 in FIG.

  The TU size determination unit 223 operates in the same manner as the PU size determination unit 213, and based on the determination result by the MV similarity determination unit 222, the TU size determination unit 223 maximizes the area per TU in encoding after conversion. Determine the size.

  The unit DCT / quantization unit 224 performs DCT on the residual signal according to the TU size determined by the TU size determination unit 223 to obtain a DCT coefficient, performs quantization processing on the DCT coefficient, Output as DCT and quantized residual signal j.

  FIG. 13 shows a flowchart of the DCT / quantization unit 22A having the above configuration.

  The DCT / quantization unit 22A performs the same process as the process performed by the second predicted value generation unit 21 in each of steps S1 to S5 in FIG. 8 in each of steps S11 to S15.

  In step S16, the DCT / quantization unit 22A performs DCT on the residual signal according to the TU size determined in step S15 to obtain DCT coefficients, performs quantization processing on the DCT coefficients, and performs FIG. The process shown in (5) is terminated.

  According to the video compression format conversion device 1A described above, the following effects can be obtained.

  The video compression format conversion device 1A determines a region where the features of the video signal are similar based on the motion vector in each prediction block before conversion, and determines the TU size after conversion based on the determination result. Therefore, the video compression format can be converted while suppressing a decrease in image quality even between compression methods in which the unit block size of the encoding process is larger after conversion than before conversion.

  Further, as described above, the video compression format conversion device 1A determines a region where the features of the video signal are similar based on the motion vector in each prediction block before conversion, and the TU size after conversion based on the determination result To decide. For this reason, since a TU size as large as possible can be applied in a region where the characteristics of the video signal are similar, in general, by adopting a large TU size in a region where the characteristics of the video signal are uniform, The degree of energy concentration is increased for the transformed transform coefficient, and high coding performance is obtained. Therefore, the video compression format conversion device 1A can improve the encoding performance.

  Further, as described above, the video compression format conversion device 1A determines a region where the features of the video signal are similar based on the motion vector in each prediction block before conversion, and the TU size after conversion based on the determination result To decide. For this reason, it is possible to determine the TU size after conversion without calculating the cost value when applied to each of all TU sizes applicable as the TU size after conversion. Therefore, the processing cost required for converting the video compression format can be reduced.

<Third Embodiment>
[Configuration and Operation of Video Compression Format Conversion Apparatus 1B]
FIG. 14 is a block diagram of a video compression format conversion apparatus 1B according to the third embodiment of the present invention. The video compression format conversion device 1B is different from the video compression format conversion device 1 according to the first embodiment of the present invention shown in FIG. 1 in that a conversion processing unit 20B is provided instead of the conversion processing unit 20. In the video compression format conversion device 1B, the same components as those of the video compression format conversion device 1 are denoted by the same reference numerals and description thereof is omitted.

(Configuration and operation of conversion processing unit 20B)
FIG. 15 is a block diagram of the conversion processing unit 20B. The transform processing unit 20B is different from the transform processing unit 20 according to the first embodiment of the present invention shown in FIG. 3 in place of the DCT / quantization unit 22, and the DCT / quantization according to the second embodiment of the present invention. The difference is that the portion 22A is provided.

Note that the PU size is determined by the second predicted value generation unit 21 so that the prediction accuracy is optimal. On the other hand, the TU size is determined by the DCT / quantization unit 22A so that the encoding performance is the highest. For this reason, although both the PU size and the TU size are determined depending on the characteristics of the video signal, the norms that contribute to the determination differ between the two. Therefore, it is assumed that the threshold value T _PU used by the second predicted value generation unit 21 and the threshold value T _TU used by the DCT / quantization unit 22A are independent values.

  According to the video compression format conversion device 1B described above, the above-described effects that the video compression format conversion device 1 can exhibit and the above-described effects that the video compression format conversion device 1A can achieve can be achieved.

  The processing of the video compression format converter 1 and the video compression format converters 1A and 1B of the present invention is recorded on a computer-readable non-transitory recording medium, and the program recorded on the recording medium is recorded in a video compression format. The present invention can be realized by causing the conversion device 1 and the video compression format conversion devices 1A and 1B to read and execute them.

  Here, for example, a nonvolatile memory such as an EPROM or a flash memory, a magnetic disk such as a hard disk, a CD-ROM, or the like can be applied to the above-described recording medium. Also, reading and execution of the program recorded on the recording medium is performed by a processor provided in the video compression format conversion device 1 and the video compression format conversion devices 1A and 1B.

  In addition, the above-mentioned program is transmitted from the video compression format conversion device 1 or the video compression format conversion devices 1A and 1B storing the program in a storage device or the like via a transmission medium or by transmission waves in the transmission medium. It may be transmitted to a computer system. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  Further, the above-described program may be for realizing a part of the above-described function. Furthermore, what can implement | achieve the above-mentioned function in combination with the program already recorded on the video compression format converter 1 or the video compression format converter 1A, 1B, what is called a difference file (difference program) may be sufficient.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes a design that does not depart from the gist of the present invention.

  For example, in each of the above-described embodiments, the similarity of video signals between prediction blocks adjacent to each other before conversion is calculated using motion vectors in these prediction blocks. However, the present invention is not limited to this. For example, the pixel values of these prediction blocks may be used. In this case, an average value or a variance value of each pixel value of these prediction blocks is calculated, and signal similarity is calculated based on a difference value of calculation results of each prediction block.

  In each of the above embodiments, the compression method of the pre-conversion compressed data a is, for example, H.264. H.264, and the compression method of the converted compressed data b may be HEVC, for example. Further, the compression method of the pre-conversion compressed data a may be MPEG-2, for example, and the compression method of the post-conversion compressed data b may be HEVC, for example.

DESCRIPTION OF SYMBOLS 1, 1A, 1B ... Video compression format conversion apparatus 10 ... Pre-conversion decoding process part 20, 20A, 20B ... Conversion process part 21, 21A ... 2nd prediction value generation part 22, 22A. ··· DCT / quantization unit 211, 221 ... MV similarity calculation unit 212, 222 ... MV similarity determination unit 213 ... PU size determination unit 223 ... TU size determination unit T _PU , T _TU ... Threshold

Claims (6)

From the first compression method in which the unit block size of the encoding process is the first size, to the second compression method in which the unit block size of the encoding process is a second size larger than the first size, A video compression format converter for converting a video compression format,
Similarity calculation means for calculating the similarity of the video signal between the prediction blocks using the distance between motion vectors between the prediction blocks adjacent to each other before conversion ;
Similarity determination means for determining the similarity of video signals between prediction blocks adjacent to each other before the conversion based on the calculation result by the similarity calculation means;
A video compression format conversion device comprising: a block size determination unit that determines a block size after conversion based on a determination result by the similarity determination unit. 2. The video according to claim 1 , wherein the block size determining unit determines one of a predicted block size after conversion and a converted block size after conversion as the block size after conversion. Compression format converter. The video according to claim 1 or 2 , wherein the block size determining means determines both the predicted block size after conversion and the converted block size after conversion as the block size after conversion. Compression format converter. The similarity determination means includes
The similarity of the video signal between the prediction blocks adjacent to each other before the conversion calculated by the similarity calculation means is compared with a predetermined threshold, and the similarity between the prediction blocks is determined based on the comparison result. Judgment,
In the case where the predicted block size after the conversion is determined by the block size determining means and the case where the converted block size after the conversion is determined by the block size determining means, mutually independent values are used as the threshold values. 4. The video compression format conversion apparatus according to claim 3 , wherein A first calculation method including a similarity calculation unit, a similarity determination unit, and a block size determination unit, wherein the unit block size of the encoding process is the first size; A video compression format conversion method in a video compression format conversion apparatus that converts a video compression format to a second compression method that is a second size larger than the size of
A first step in which the similarity calculation means calculates the similarity of the video signal between the prediction blocks using the distance between motion vectors between the prediction blocks adjacent to each other before conversion ;
A second step in which the similarity determination means determines the similarity of video signals between prediction blocks adjacent to each other before the conversion based on the calculation result in the first step;
A video compression format conversion method comprising: a third step in which the block size determination means determines a block size after conversion based on a determination result in the second step. A first calculation method including a similarity calculation unit, a similarity determination unit, and a block size determination unit, wherein the unit block size of the encoding process is the first size; A program for causing a computer to execute a video compression format conversion method in a video compression format conversion apparatus that converts a video compression format to a second compression method that is a second size larger than the size of
A first step in which the similarity calculation means calculates the similarity of the video signal between the prediction blocks using the distance between motion vectors between the prediction blocks adjacent to each other before conversion ;
A second step in which the similarity determination means determines the similarity of video signals between prediction blocks adjacent to each other before the conversion based on the calculation result in the first step;
A program for causing the computer to execute a third step in which the block size determining means determines a block size after conversion based on the determination result in the second step.

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