JP2014096754A - Encoding system conversion device, encoding system conversion method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform H.V. In the transcoding to H.264, the prediction block size and prediction mode specific to HEVC are set to H.264. There is a problem that the encoding efficiency cannot be maintained unless it is appropriately converted to a prediction block size of 264 and a prediction mode.
Decoding means for generating an image by decoding a first encoded stream encoded using a first parameter in a first encoding method, and a first prediction block size included in the first parameter A first determination unit that determines whether the size is equal to or greater than a predetermined size, a second determination unit that determines whether the first prediction mode included in the first parameter is a predetermined mode, and the first and second determination units. Based on the result, a determination unit that determines a second prediction block size, and a second parameter including the second prediction block size determined by the determination unit is used to determine the image generated by the decoding unit using a second parameter. Encoding means for encoding by an encoding method.
[Selection] Figure 1

Description

  The present invention relates to an encoding method conversion apparatus and an encoding method conversion method for decoding a moving image encoded by a first encoding method and converting the encoding method by re-encoding the moving image by a second encoding method. And an encoding system conversion program.

  In recent years, MPEG-2, H.264. There is an increasing demand for a transcoding function for re-encoding a moving image encoded by an encoding method such as H.264 / MPEG-4 AVC (hereinafter referred to as H.264) using another encoding method.

  In Patent Document 1, as a method of transcoding function, H.264 input from the outside is used. A method of converting a H.264 format moving image to a MPEG-2 format moving image has been proposed.

  On the other hand, standardization of High Efficiency Video Coding (hereinafter referred to as HEVC), which is a next-generation coding scheme, is currently underway in JCT-VC (Joint Collaborative Team on Video Coding).

  In HEVC, the size (hereinafter referred to as CU size) of a coding block (CU: Coding unit) that is a unit of a block to be coded is variable. In HEVC, the CU size can take a block size from 64 × 64 pixels to 8 × 8 pixels (either 64 × 64 pixels, 32 × 32 pixels, 16 × 16 pixels, or 8 × 8 pixels). In addition, the size of a prediction block (PU: Prediction unit) that is a block unit for performing intra prediction (intra-screen prediction) and inter prediction (inter-screen prediction) is also variable. The PU size can be a block size from 64 × 64 pixels to 4 × 4 pixels (either 64 × 64 pixels, 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, or 4 × 4 pixels). . Furthermore, the size of a transform block (TU: Transform unit) (hereinafter referred to as TU size), which is a unit of a block for performing transform such as orthogonal transform, is also variable. The TU size can take a block size from 32 × 32 pixels to 4 × 4 pixels (either 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, or 4 × 4 pixels).

  For this reason, it is possible to improve encoding efficiency by appropriately determining the sizes of the CU, PU, and TU at the time of encoding. Note that 16 × 16 pixels indicate a block of 16 pixels in the horizontal direction and 16 pixels in the vertical direction, and in the embodiment of the present invention, this is expressed as 16 × 16 pixels. The same is true even if the number of pixels changes.

JP 2008-148060 A

  In the existing coding schemes other than HEVC, the size of the coding block is fixed, so that the conventional transcode does not need to search for the size of the coding block after the coding method conversion. For example, H.C. In H.264, the size of a macroblock which is an encoded block is only 16 × 16 pixels.

  On the other hand, in HEVC, the CU size (encoded block size) is variable. That is, the LCU (Large Coding Unit) size which is the maximum CU size of HEVC is 64 × 64 pixels, and it is possible to divide the LCU into a plurality of CUs having different sizes and perform encoding. Similarly, a PU can be divided and encoded into a plurality of PUs having different sizes in the LCU.

  Furthermore, the prediction mode of HEVC is H.264. It is more diverse than the H.264 prediction mode, and there are many HEVC specific modes.

  For this reason, from HEVC to H.264. In transcoding to H.264, the prediction block size specific to HEVC and the prediction mode are set as H.264. It was necessary to appropriately convert to a prediction block size of 264 and a prediction mode. H. If the prediction block size in H.264 and the prediction mode are not appropriately used, The prediction error calculated by prediction when re-encoding with H.264 is larger than the prediction error calculated by prediction when encoding with HEVC. That is, from HEVC to H.264. In transcoding to H.264, H.264 If the H.264 prediction block size and the prediction mode are not appropriately used, there is a problem in that a prediction error increases and coding efficiency decreases.

  H. H.264 when re-encoding. When the search is performed for all the prediction block sizes and prediction modes that can be obtained by H.264, the prediction block size and the prediction mode used for encoding by HEVC can be appropriately converted. However, H. Since the search is performed for all prediction block sizes and prediction modes that can be taken by H.264, there is a problem that the processing load (calculation amount) of the search increases and the processing time required for transcoding increases.

  Note that there is a similar problem in transcoding from the first encoding method to the second encoding method in which the size of the encoding block of the first encoding method is variable.

  Based on the above problems, the present invention determines an appropriate prediction block size and prediction mode without increasing the processing load for searching for the prediction block size and prediction mode at the time of re-encoding in transcoding. Objective.

  In order to solve the above-described problems, the encoding method conversion apparatus of the present invention has the following configuration. That is, decoding means for decoding a first encoded stream encoded using the first encoding parameter in the first encoding scheme to generate a decoded image, and the first encoding parameter First determination means for determining whether or not the first prediction block size included is greater than or equal to a predetermined size, and whether or not the first prediction mode included in the first encoding parameter is a predetermined mode A determination for determining a second prediction block size based on a second determination means for determining whether or not, a result determined by the first determination means and a result determined by the second determination means And a code for encoding the decoded image generated by the decoding unit by a second encoding method using a second encoding parameter including a second prediction block size determined by the determining unit And And wherein the Rukoto.

  According to the present invention, it is possible to determine an appropriate prediction block size and prediction mode without increasing a processing load for searching for a prediction block size and a prediction mode at the time of re-encoding in transcoding.

1 is a block diagram of a coding method conversion apparatus according to a first embodiment. 7 is a flowchart illustrating re-encoding parameter determination processing according to the first embodiment. H. The figure showing the prediction mode of H.264 4x4 pixel block prediction and 8x8 pixel block prediction The figure showing the prediction mode of HEVC The figure showing the re-encoding parameter determined in Embodiment 1 The figure showing the encoding parameter determination process which used the table in Embodiment 1. The figure showing the determination process of the prediction block size in Embodiment 1. HEVC PU size and H.264 The figure showing the correspondence with the prediction block size of H.264 HEVC prediction mode and H.264. The figure showing the correspondence with the prediction mode of H.264 Block diagram of encoding system conversion apparatus of embodiment 2 10 is a flowchart illustrating re-encoding parameter determination processing according to the second embodiment. The block diagram of the encoding system converter of Embodiment 3 The figure showing change of PU size inside 64x64 LCU in resolution conversion The flowchart showing the representative prediction mode determination process of Embodiment 3. A flowchart showing the re-encoding parameter determination process of Embodiment 3. The figure showing selection of either 4x4 pixel block prediction or 8x8 pixel block of Embodiment 3 FIG. 1 is a block diagram showing an example of a hardware configuration of a computer applicable to the encoding method conversion apparatus of the present invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. The configurations shown in the following embodiments are merely examples, and the present invention is not limited to the illustrated configurations.

<Embodiment 1>
FIG. 1 is a block diagram of a coding method conversion apparatus according to the first embodiment. The encoding method conversion apparatus according to the present embodiment includes a decoding unit (decoding unit) 101, a re-encoding parameter determination unit 102, and an encoding unit (encoding unit) 103.

  The decoding unit 101 decodes an input encoded stream (hereinafter referred to as a first encoded stream) encoded by the first encoding method. Further, the decoding unit 101 sends the decoding parameters used at the time of decoding the first encoded stream to the re-encoding parameter determination unit 102, and encodes the decoded image obtained by decoding the first encoded stream. The data is sent to the unit 103. Based on the decoding parameter input from the decoding unit 101, the re-encoding parameter determination unit 102 determines a parameter (hereinafter referred to as re-encoding parameter) to be used when re-encoding to the second encoding method. The re-encoded parameters are sent to the encoding unit 103. The encoding unit 103 encodes the decoded image input from the decoding unit 101 based on the re-encoding parameter input from the re-encoding parameter determination unit 102 using the second encoding method, and performs the second encoding. Output a stream.

  Further, each part will be described below. For ease of explanation, the first encoded stream is a stream encoded in HEVC format, and the second encoded stream is H.264. The stream is encoded in the H.264 format.

  The decoding unit 101 inputs a first encoded stream and decodes the input first encoded stream. Further, the decoding unit 101 determines a re-encoding parameter using, as decoding parameters, information on at least the CU size, the PU size at the time of prediction, and the prediction mode among the information obtained at the time of decoding the first encoded stream. Sent to the unit 102. Note that, in the embodiment of the present invention, prediction indicates intra prediction (intra-screen prediction), and hereinafter, intra prediction is simply referred to as prediction. Similarly, in the embodiment of the present invention, the intra prediction mode and the intra prediction block size are also expressed as the prediction mode and the prediction block size.

  Next, the re-encoding parameter determination unit 102 will be described. FIG. 2 is a flowchart illustrating processing for determining a re-encoding parameter in the re-encoding parameter determination unit 102. Note that FIG. 2 illustrates processing when it is determined that the CU to be recoded has been encoded by prediction based on the decoding parameter input to the recoding parameter determination unit 102. It should be noted that various existing techniques can be applied as a method for determining parameters such as PU size and motion vector for a CU that has been encoded by inter prediction (inter-screen prediction). Further, in FIG. 2, the block size is described as 16 × 16, which is synonymous with 16 × 16 pixels. The same is true even if the number of pixels changes. The same applies to the drawings after FIG.

  The re-encoding parameter determination unit 102 starts the process for determining the re-encoding parameter after obtaining the decoding parameters of the block to be re-encoded for at least 1 LCU. In this embodiment, the LCU size is 64 × 64 pixels. In the following description, it is assumed that the re-encoding parameter determination unit 102 has acquired the decoding parameters of the re-encoding target block corresponding to 1 LCU (64 × 64 pixels).

  First, in step S201, the re-encoding parameter determination unit 102 determines the PU size in the prediction of the CU to be re-encoded based on the decoding parameter obtained when the input first encoded stream is decoded. . In step S201 of this embodiment, when the PU size in the prediction of the CU to be re-encoded is smaller than a predetermined size (16 × 16 pixels), step S204 is performed. When the PU size is greater than the predetermined size, step S202 is performed. Each of these processes is performed.

  If the PU size is smaller than 8 × 8 pixels in step S201 (8 × 8 pixels or less) (NO in S201), the recoding parameter determination unit 102 sets the predicted block size at the time of recoding to 16 × 16 pixels. Other than (4 × 4 pixels or 8 × 8 pixels) is set (S204). When the PU size is 16 × 16 pixels or more (any of 16 × 16 pixels, 32 × 32 pixels, or 64 × 64 pixels) in step S201 (YES in S201), the re-encoding parameter determination unit 102 determines the prediction mode. Is determined (S202).

  Here, H. The prediction modes in H.264 and HEVC will be described respectively. FIG. H.264 prediction mode, and FIG. 4 shows HEVC prediction mode.

  As shown in FIG. In H.264, nine modes are defined in 4 × 4 pixel block prediction and 8 × 8 pixel block prediction of luminance samples (hereinafter referred to as luminance). In this embodiment, 4 × 4 pixel block prediction is prediction in a prediction block size of 4 × 4 pixels. The same is true even if the number of pixels changes. FIG. 3B shows a prediction mode of 16 × 16 pixel block prediction of luminance, and FIG. 3C shows a prediction mode of 8 × 8 pixel block prediction of a color difference sample (hereinafter referred to as “color difference”). As shown in FIGS. 3B and 3C, the following four modes are defined in the 16 × 16 pixel block prediction for luminance and the 8 × 8 pixel block prediction for color difference. That is, H.H. In the H.264 luminance 16 × 16 pixel block prediction and the color difference 8 × 8 pixel block prediction, horizontal prediction (Horizontal), vertical prediction (Vertical), average value prediction (DC), and plane prediction (Plane) A mode is defined.

  On the other hand, in HEVC, as shown in FIG. 4, the prediction modes of luminance are PU sizes of 4 × 4 pixels, 8 × 8 pixels, 16 × 16 pixels, 32 × 32 pixels, and 64 × 64 pixels. In addition, 35 modes (0 to 34 in FIG. 4) are defined respectively. As the color difference prediction mode in HEVC, 35 modes defined in the luminance prediction mode can be used. Further, a luminance reference mode that uses the same mode as the luminance prediction mode is defined as a color difference prediction mode.

  H. Of the H.264 luminance predictions, the largest prediction block size is 16 × 16 pixel block prediction. H. In the 16 × 16 pixel block prediction with the H.264 luminance, the number of usable prediction modes is four as shown in FIG. On the other hand, in 16 × 16 pixel block prediction with HEVC luminance, the number of usable prediction modes is 35 as shown in FIG. For this reason, H.C. When the 16 × 16 pixel block prediction is uniformly applied when re-encoding with H.264, an appropriate prediction mode cannot be selected. In other words, the prediction error calculated by using various prediction modes of HEVC is higher than that of the prediction error. There is a possibility that the prediction error calculated by H.264 becomes large and the coding efficiency is lowered. Therefore, from HEVC to H.264. When re-encoding to H.264, it is necessary to select an appropriate prediction mode.

  Returning to FIG. 2, the processing flow in the re-encoding parameter determination unit 102 after step S202 will be described.

  When the prediction mode of HEVC corresponds to the predetermined mode in step S202 (YES in S202), the re-encoding parameter determination unit 102 determines whether the H.264 is H.264. The predicted block size when re-encoding with H.264 is set to 16 × 16 pixels (S203). The predetermined mode includes an average value prediction mode, a vertical prediction mode, and a horizontal prediction mode, and these modes include prediction in HEVC and H.264. H.264 can be used for both predictions. Therefore, in step S202, it is determined whether the prediction mode in HEVC can be applied in re-encoding (H.264) by determining whether the prediction mode of the PU to be re-encoded (HEVC) is a predetermined mode. can do.

  Further, in step S203, as shown in FIG. The predicted block size of H.264 is 16 × 16 pixels. That is, when a 64 × 64 pixel PU (64 × 64 PU) is applied in HEVC (FIG. 7A), the H.C. corresponding to each 16 × 16 pixel block in the 64 × 64 pixel block. For the H.264 macroblock, 16 × 16 pixel block prediction is applied. Similarly, in the case where 32 × 32 PU (FIG. 7B) and 16 × 16 PU (FIG. 7C) are applied in HEVC, for each macroblock having 16 × 16 pixels, * 16 pixel block prediction is applied to each. In the present embodiment, for example, a PU composed of 16 × 16 pixels is also expressed as 16 × 16 PU. Similarly, CU and TU are also expressed as 16 × 16 CU and 16 × 16 TU. The same is true even if the number of pixels changes.

  On the other hand, when the HEVC prediction mode is not a predetermined mode in step S202 (NO in S202), the re-encoding parameter determination unit 102 sets the prediction block size to a value other than 16 × 16 pixels (either 4 × 4 pixels or 8 × 8 pixels). (S204).

  In this case (NO in step S202), the HEVC prediction mode is set to H.264. It cannot be applied to H.264 prediction. For this reason, H.C. If H.264 16 × 16 pixel block prediction is applied, an appropriate prediction mode cannot be selected. H. The number of prediction modes for H.264 4 × 4 pixel block prediction and 8 × 8 pixel block prediction (FIG. 3A) is larger than the number of prediction modes for 16 × 16 pixel block prediction (FIG. 3B). Therefore, in step S204, the H.264 format. Either 4 × 4 pixel block prediction or 8 × 8 pixel block prediction, which has a larger number of prediction modes in H.264 than 16 × 16 pixel block prediction, is assigned. As a result, H.E. is equivalent to the prediction mode of HEVC or closer to the prediction direction. Since an H.264 prediction mode can be selected, an increase in prediction error can be suppressed.

  Hereinafter, in the process of step S204 in FIG. A method of selecting either H.264 4 × 4 pixel block prediction or 8 × 8 pixel block prediction will be described. FIG. 8 shows HEVC PU size and H.264. It is a figure which shows a response | compatibility with the prediction block size of H.264.

  As shown in FIG. 8A, when all of the HEVC 16 × 16 pixel area is 4 × 4 PU, H.264 4 × 4 pixel block prediction is selected. Similarly, as shown in FIG. 8B, when all the 16 × 16 pixel regions of HEVC are 8 × 8 PU, H.264 8 × 8 pixel block prediction is selected.

  On the other hand, as shown in FIG. 8C, when 4 × 4 PU and 8 × 8 PU coexist in the HEVC 16 × 16 pixel region, When re-encoding with H.264, either 4 × 4 pixel block prediction or 8 × 8 pixel block prediction is selected. This is because of H.C. This is because in H.264, 8 × 8 pixel block prediction and 4 × 4 pixel block prediction cannot be used together in one macroblock.

  In this case, based on the result of comparing the number of 4 × 4 PUs and the number of 8 × 8 PUs in the 16 × 16 pixel area of HEVC using the weighting factor, H.264 is used. An H.264 prediction block size may be determined. In order to compare the number of 4 × 4 PUs and the number of 8 × 8 PUs using a weighting factor, for example, Equation 1 is used. In Equation 1, the numbers of 4 × 4 PU and 8 × 8 PU are expressed as num_4 × 4pu and num_8 × 8pu, respectively, and the weighting coefficient is expressed as α.

1/4 × num — 4 × 4pu ≦ α × num — 8 × 8pu (Formula 1)
If Equation 1 holds, If H.264 8 × 8 pixel block prediction is selected and Equation 1 does not hold, H.264 4 × 4 pixel block prediction is selected. In addition, this invention is not limited to this, The weighting coefficient (alpha) does not need to be multiplied by the right side. That is, of course, the weight coefficient α may be multiplied by the left side.

  In FIG. 8C, since 4 × 4 PU exists in 8 × 8 CU0 and 8 × 8 CU3, num_4 × 4pu indicating the number of 4 × 4 PUs is 8. On the other hand, since 8 × 8 PU exists in 8 × 8 CU1 and 8 × 8 CU2, respectively, num_8 × 8pu indicating the number of 8 × 8 PU is 2. Here, for example, when the weighting coefficient α is set to 1.1, Equation 1 is established. When the block to be re-encoded in H.264 is re-encoded, 8 × 8 pixel block prediction is applied.

  Note that the value of the weighting factor α may be a fixed value parameter or a parameter given from the outside of the re-encoding parameter determination unit 102. The value of the weighting factor α is H.264. Parameters may be set adaptively based on a code amount generated as a result of selecting either 4 × 4 pixel block prediction or 8 × 8 pixel block prediction when re-encoding with H.264.

  Then, after setting the prediction block size (S203 or S204), one of the modes equivalent to the prediction mode of HEVC or near the prediction direction is set to H.264. H.264 is determined as a prediction mode for re-encoding (S205), and the process ends.

  Next, in step S205 of FIG. A method for selecting the H.264 prediction mode will be described. FIG. 9 shows the H.264 corresponding to the prediction mode of HEVC. H.264 prediction modes are shown. Note that the H.264 shown in FIG. The prediction modes of H.264 and HEVC correspond to the prediction modes shown in FIGS.

  FIG. 9A shows an H.264 corresponding to the prediction mode of HEVC. It represents a prediction mode of 4 × 4 pixel block prediction and 8 × 8 pixel block prediction with a H.264 luminance. When the prediction mode of HEVC is 1 (DC: average value prediction), 2 (DC) of the H.264 prediction mode is associated. When the prediction mode of HEVC is any of 2 to 8, Of the H.264 prediction modes, 8 that are equivalent or have similar prediction directions are associated. H. mentioned above. Similarly, prediction modes other than 2 to 8 of H.264 are associated with modes equivalent to or similar to the prediction modes of HEVC.

  FIG. 9B shows the HEVC prediction mode and H.264. The correspondence with the prediction mode of the 16 × 16 pixel block prediction with the H.264 luminance is shown.

  FIG. 9C shows the HEVC prediction mode and H.264. The correspondence with the prediction mode of 8 × 8 pixel block prediction of H.264 color difference is shown. 9C, the HEVC color difference luminance reference mode is a mode in which the luminance prediction mode is the same as the color difference prediction mode. There is no equivalent or similar mode in H.264. Therefore, in this embodiment, the color difference prediction mode is estimated from the HEVC luminance prediction mode. For example, when the HEVC luminance prediction mode is 1 (DC: average value prediction), the H.264 color difference prediction mode is associated with 0 (DC). In this way, by referring to the prediction mode (0 to 34) of the luminance of HEVC and associating a mode equivalent to the prediction mode or a mode close to the prediction direction, the H.C. It is possible to reduce the processing load of the prediction mode search when re-encoding with H.264.

  In the present embodiment, the prediction pixel of HEVC color difference is generated with reference to the decoded pixel of luminance, but the present invention is not limited to this. That is, when a pixel of an image is composed of a plurality of components and a predicted pixel of an arbitrary M2th component of the plurality of components is generated with reference to a decoded pixel of the M1 (M1 ≠ M2) th component, Similar processing can be applied.

  As described above, the re-encoding parameter can be determined based on the decoding parameter input to the re-encoding parameter determination unit 102 by executing the processing flow of FIG. Effects can be obtained.

  First, if YES in step S201 of FIG. 2 and YES in step S202, the process of step S203 is performed. With this process, it is possible to reduce the processing load required to search for the predicted block size at the time of re-encoding while suppressing a decrease in encoding efficiency (an increase in prediction error).

  Further, if YES in step S201 of FIG. 2 and NO in step S202, the process of step S204 is performed. Also, if NO in step S201, the process of step S204 is performed. With these processes, H.264 is equivalent to the prediction mode of HEVC or closer to the prediction direction. Since an H.264 prediction mode can be selected, an increase in prediction error can be suppressed.

  That is, according to the present embodiment, HEVC is changed to H.264. When re-encoding to H.264, it is possible to determine an appropriate prediction block size and prediction mode without increasing the processing load for searching for the prediction block size and prediction mode.

  Next, an example of the re-encoding parameter at the time of re-encoding determined based on the decoding parameter by the above processing is shown in FIG. Note that the prediction mode in the example shown in FIG. 5 represents a luminance prediction mode.

  Note that the correspondence relationship between the re-encoding parameter and the decoding parameter shown in FIG. 5 is held in an array in a table format, and the re-encoding parameter determination unit 102 re-encodes by referring to the table based on the decoding parameter. The parameter may be determined.

  In this embodiment, the table shown in FIG. 5 is held by the re-encoding parameter determination unit 102, but the present invention is not limited to this. That is, the table may be held by an external recording device (recording unit), and the re-encoding parameter determination unit 102 may read the table from the recording device.

  Further, FIG. 6 shows the re-encoding stored in the array in the table format based on the index determined from the CU size, PU size, and prediction mode of the block to be re-encoded in the first encoded stream (HEVC). It is a figure which shows the process which refers to an optimization parameter. In FIG. 6, when the decoding parameter obtained by decoding the first encoding parameter is 32 × 32 PU and the predetermined prediction mode, the associated index is determined to be 0. Then, the re-encoding parameter determination unit 102 refers to the array Pred_size [0] storing the predicted block size based on the determined index 0. Pred_size [0] stores information indicating 16 × 16 pixel block prediction, and the recoding parameter determination unit 102 determines the prediction block size at the time of recoding to 16 × 16 pixel block prediction. In this way, the re-encoding parameters are stored in a table format, and the re-encoding parameters are determined at a higher speed than when the processing flow shown in FIG. 2 is realized as a software branch process by referring to the table. It becomes possible.

  The re-encoding parameter determination unit 102 sends information on the prediction block size and the prediction mode determined as described above to the encoding unit 103 as re-encoding parameters.

  Based on the re-encoding parameter sent from the re-encoding parameter determination unit 102, the encoding unit 103 converts the decoded image output from the decoding unit 101 to H.264. It is encoded in the H.264 format.

  Note that the present invention is not limited to this, and the function of the re-encoding parameter determination unit 102 in this embodiment may be provided inside either the decoding unit 101 or the encoding unit 103 shown in FIG. Good.

  Further, in the present embodiment, the re-encoding parameter determination unit 102 performs the 64 × 64 PU, 32 × 32 PU, and 16 × 16 PU of the block to be re-encoded of the first encoded stream encoded by HEVC. It is determined whether or not it is a predetermined prediction mode. However, the present invention is not limited to this, and when applied to a coding scheme other than HEVC, the predicted block size (PU size in HEVC) is replaced with a predicted block size of an arbitrary N × N pixels (N: natural number). It is also possible.

  Further, only a part of the re-encoding parameters determined by the re-encoding parameter determination unit 102 may be used by the encoding unit 103. For example, only the prediction block size among the re-encoding parameters may be used, and the prediction mode may be searched by the encoding unit 103.

  Further, the re-encoding parameter determined by the re-encoding parameter determination unit 102 may be used as an initial value when the encoding unit 103 searches for a more optimal re-encoding parameter. That is, the re-encoding parameter determined by the re-encoding parameter determination unit 102 does not necessarily have to be used when re-encoding by the encoding unit 103, and the re-encoding parameter may be re-determined.

  Furthermore, the method for selecting either 4 × 4 pixel block prediction or 8 × 8 pixel block prediction and the method for determining the weighting coefficient α in Equation 1 are not limited to the methods described in the embodiment. Absent.

  Furthermore, although it is determined in S203 of FIG. 2 whether the average value prediction mode, the horizontal prediction mode, or the vertical prediction mode, the present invention is not limited to this. That is, HEVC's Planar prediction (intra_Planar) mode is set to H.264. It may be considered that it corresponds to the H.264 plane prediction (Plane) mode. That is, in step S203 of FIG. 2, it may be determined whether the mode is the average value prediction mode, the horizontal prediction mode, the vertical prediction mode, or the Planar prediction mode.

  Further, the prediction mode of HEVC shown in FIG. Correspondence with the H.264 prediction mode is also an example, and associations other than those illustrated may be performed.

<Embodiment 2>
Next, Embodiment 2 of the present invention shown in FIG. 10 will be described. In FIG. 10, parts that are not different from those in FIG. 1 of the first embodiment are denoted by the same reference numerals.

  As in the first embodiment, for ease of explanation, the first encoded stream is a stream encoded in the HEVC format, and the second encoded stream is H.264. The stream is encoded in the H.264 format.

  In FIG. 10, a decoding unit (decoding unit) 301 decodes the input first encoded stream, and is used when decoding the first encoded stream, similarly to the decoding unit 101 in FIG. 1 of the first embodiment. The information is sent to the re-encoding parameter determination unit 302 as a decoding parameter. Furthermore, the decoding unit 301 also sends various statistical information obtained by decoding the first encoded stream to the re-encoding parameter determination unit 302 as decoding parameters. In the present embodiment, the statistical information is information including at least one of information on a prediction residual at the time of HEVC decoding, information on the presence / absence of a significant coefficient (non-zero coefficient), and information on the code amount of the HEVC encoded stream. It is. Also, in FIG. 10, the decoding unit 301 sends a decoded image obtained by decoding the first encoded stream to the encoding unit 103, similarly to the decoding unit 101 in FIG. 1.

  The re-encoding parameter determination unit 302 determines the re-encoding parameter according to the flow shown in FIG. 11 based on the decoding parameter acquired from the decoding unit 301. More specifically, the re-encoding parameter determination unit 302 is based on the statistical information obtained by decoding the first encoded stream by the decoding unit 301, based on the H.264 standard. The prediction block size used when re-encoding with H.264 is determined.

  Hereinafter, the re-encoding parameter determination process in the re-encoding parameter determination unit 302 will be described with reference to FIG.

  In FIG. 11, processes that are the same as those in FIG. 2 of the first embodiment are denoted by the same reference numerals. The processing in step S201 and step S202 in FIG. 11 is the same as the processing in step S201 and step S202 in FIG.

  The prediction mode of HEVC is H.264. In the case of the H.264 predetermined prediction mode (any one of the average value prediction mode, the vertical prediction mode, and the horizontal prediction mode) (YES in S202), the statistical information acquired by the decoding unit 301 is compared with a predetermined threshold value. (S1101). If the statistical information is equal to or smaller than the threshold value in step S1101 (YES in S1101), the The predicted block size when re-encoding with H.264 is set to 16 × 16 pixels (S203). On the other hand, when the statistical information is larger than the threshold (NO in S1101), The predicted block size when re-encoding with H.264 is set to 8 × 8 pixels (S1102). In the present embodiment, the case where the statistical information is larger than the threshold means that the number of significant coefficients of the transform coefficient acquired by the decoding unit 301 is equal to or larger than the threshold, but the present invention is not limited to this. Not. That is, prediction residual distribution / SAD (Sum of Absolute Difference) and the number of significant coefficients may be greater than or equal to a threshold, and the code amount of a block to be recoded may be greater than or equal to a threshold. .

  H. In H.264, when either 16 × 16 pixel block prediction or 4 × 4 pixel block prediction is applied, a macroblock is divided into 16 4 × 4 pixel blocks, and each divided 4 × 4 pixel block is divided. Perform orthogonal transformation. On the other hand, H. When the 8 × 8 pixel block prediction is applied to H.264, the macroblock is divided into four 8 × 8 pixel blocks, and orthogonal transformation is performed in units of the divided 8 × 8 pixel blocks.

  Note that the orthogonal transformation of the 8 × 8 pixel block can leave the frequency component more finely than the orthogonal transformation of the 4 × 4 pixel block. That is, in this embodiment, when it is determined in step S1101 that the statistical information is equal to or smaller than the threshold value, the transform block size is 4 × 4 pixels because 16 × 16 pixel prediction is applied. If it is determined in step S1101 that the statistical information is larger than the threshold, the transform block size is 8 × 8 pixels because 8 × 8 pixel prediction is applied. Thereby, the transform block size can be determined based on the statistical information, and when the statistical information is larger than the threshold, a larger transform block size is used than when the statistical information is less than or equal to the threshold. Either encoding efficiency or image quality can be improved.

  After the prediction block size is determined in each of steps S203, S204, and S1102, a mode equivalent to or similar to the prediction mode of HEVC is selected from H.264. H.264 is determined as a prediction mode for re-encoding (S205), and the process ends. Other processes are the same as those in the first embodiment.

  The re-encoding parameter determination unit 302 sends information on the prediction block size and the prediction mode determined as described above to the encoding unit 103 in FIG. 12 as re-encoding parameters.

  Based on the re-encoding parameter input from the re-encoding parameter determination unit 302, the encoding unit 103 converts the decoded image input from the decoding unit 301 to H.264. It is encoded in the H.264 format.

  In the present embodiment, as in the first embodiment, HEVC to H.264. When re-encoding to H.264, it is possible to determine an appropriate prediction block size and prediction mode without increasing the processing load required for searching for the prediction block size and the prediction mode.

  Furthermore, in this embodiment, based on the statistical information obtained by decoding the first encoded stream encoded by HEVC, the H.264 encoding is performed. 16 × 16 pixel block prediction and 8 × 8 pixel block prediction used when re-encoding to H.264 are switched.

  Therefore, in this embodiment, by determining the prediction block size based on the statistical information, it is determined whether either the coding efficiency or the image quality is improved when the orthogonal transformation of the 8 × 8 pixel block is applied. . As a result, when it is estimated that either the coding efficiency or the image quality by the application of the 8 × 8 pixel block is improved, it becomes possible to select the orthogonal transform of the 8 × 8 pixel block. Either the coding efficiency or the image quality at the time can be improved. Here, for example, when the HEVC prediction error distribution is greater than or equal to the threshold, it is estimated that the prediction in HEVC is not efficient. In this case, the 8 × 8 pixel conversion that can leave the frequency component finer than the 4 × 4 pixel conversion is selected. Therefore, the reproducibility of the prediction error is increased, and H.264 is improved. The image quality of an image obtained by re-encoding with H.264 can be improved.

  Note that the present invention is not limited to this, and the function of the re-encoding parameter determination unit 302 in the present embodiment may be provided in either the decoding unit 301 or the encoding unit 103 shown in FIG. Good.

  Further, only a part of the re-encoding parameters determined by the re-encoding parameter determination unit 302 may be used by the encoding unit 103. For example, only the prediction block size among the re-encoding parameters may be used, and the prediction mode may be searched by the encoding unit 103. Alternatively, the re-encoding parameter determined by the re-encoding parameter determination unit 302 may be used as an initial value when the encoding unit 103 searches for a more optimal re-encoding parameter. That is, after the re-encoding parameter determination unit 302 determines the re-encoding parameter, the re-encoding parameter may be searched again.

  In the present embodiment, only one threshold comparison step (S1101) is shown in the flowchart shown in FIG. 11, but the present invention is not limited to this. A threshold comparison may be performed for each piece of statistical information, and the predicted block size may be determined based on the results. One piece of statistical information may be compared with a plurality of threshold values. Further, the threshold value may be fixed, or may be a parameter given from an external module of the re-encoding parameter determination unit 102. H. As a threshold value, a parameter adaptively set based on each code amount generated at the time of re-encoding as a result of selecting an orthogonal transform of either H.264 4 × 4 pixel block or 8 × 8 pixel block.

<Embodiment 3>
Next, Embodiment 3 of the present invention shown in FIG. 12 will be described. In FIG. 12, parts that are the same as those in FIG.

  As in the first embodiment, for ease of explanation, the first encoded stream is a stream encoded in the HEVC format, and the second encoded stream is H.264. The stream is encoded in the H.264 format.

  In FIG. 12, the decoding unit 101 decodes the input first encoded stream, and re-encodes the information used when decoding the first encoded stream as a decoding parameter, as in FIG. 1 of the first embodiment. It is sent to the parameter determination unit 502. Further, the decoding unit 101 sends a decoded image obtained by decoding the first encoded stream to the resolution conversion unit (conversion unit) 504. The resolution conversion unit 504 converts the resolution of the decoded image input from the decoding unit 101 (resolution conversion), and sends the decoded image after the resolution conversion to the encoding unit 103. Further, the resolution conversion unit 504 sends information (resolution conversion information) used when converting the resolution of the decoded image to the re-encoding parameter determination unit 502. The re-encoding parameter determination unit 502 determines re-encoding parameters based on the decoding parameters input from the decoding unit 101 and the resolution conversion information input from the resolution conversion unit 504, and sends them to the encoding unit 103. Based on the re-encoding parameter input from the re-encoding parameter determination unit 502, the encoding unit 103 encodes the decoded image that has been resolution-converted by the resolution conversion unit 504 using the second encoding method. Output the encoded stream.

  Here, the correspondence of the PU size of HEVC before and after resolution conversion of the decoded image by the resolution conversion unit 504 will be described with reference to FIG. In FIG. 13, the portion surrounded by the dotted line indicates the corresponding pixel position before and after the resolution conversion. Here, a case where an LCU having 64 × 64 pixels is input to the resolution conversion unit 504 will be described as an example.

  FIG. 13A shows a state in which a block of 64 × 64 pixels before resolution conversion is divided into PUs. FIG. 13B shows a corresponding PU in a 32 × 32 pixel block obtained by multiplying the 64 × 64 pixel block of FIG. 13A by 1/2 in the horizontal direction and the vertical direction, respectively. Similarly, FIG. 13C shows the division of the corresponding PU in the 16 × 16 pixel block obtained by multiplying the 64 × 64 pixel block of FIG. 13A by 1/4 in the horizontal direction and the vertical direction, respectively. Represent.

  First, the case of halving in the horizontal and vertical directions will be described with reference to FIGS. 13 (a) and 13 (b).

  In FIG. 13A, pixel regions to which 32 × 32 PU, 16 × 16 PU, and 8 × 8 PU (gray portion in FIG. 13) are applied are 16 × 16 PU, It can be considered that 8 × 8 PU and 4 × 4 PU are applied. Further, the prediction mode of each PU after resolution conversion can be regarded as the same as the prediction mode of each corresponding PU before resolution conversion.

  On the other hand, in FIG. 13 (a), 8 × 8 pixels (shaded portions in FIG. 13) encoded with four 4 × 4 PUs are converted into 4 × 4 pixels by resolution conversion as shown in FIG. 13 (b). Converted. For this reason, it is necessary to determine a 4 × 4 PU prediction mode corresponding to the 4 × 4 pixels after resolution conversion. In the present embodiment, a mode (hereinafter referred to as a representative prediction mode) used for prediction after resolution conversion is determined from prediction modes of a plurality of PUs before resolution conversion. Various conventional techniques can be applied to the representative prediction mode determination method.

  Next, the case of ¼ times in the horizontal and vertical directions will be described with reference to FIGS. 13 (a) and 13 (c).

  In FIG. 13A, pixel regions to which 32 × 32 PU and 16 × 16 PU are applied are respectively applied with 8 × 8 PU and 4 × 4 PU as shown in FIG. 13C. Can be considered. Also, the prediction mode of each PU after resolution conversion can be regarded as the same as the prediction mode of each corresponding PU before resolution conversion.

  On the other hand, in FIG. 13A, four 8 × 8 pixels encoded with 4 × 4 PU (the hatched portion in FIG. 13) and three 8 × 8 pixels encoded with 8 × 8 PU (in FIG. 13). As shown in FIG. 13C, the 16 × 16 pixels including the gray portion become 4 × 4 pixels by resolution conversion. For this reason, it is necessary to determine one 4 × 4 PU prediction mode corresponding to the 4 × 4 pixels after resolution conversion. Therefore, the re-encoding parameter determination unit 502 determines a representative prediction mode corresponding to the 4 × 4 pixels after resolution conversion.

  Next, the re-encoding parameter determination unit 502 will be described with reference to FIG. FIG. 14 is a flowchart showing processing for determining the representative prediction mode based on the resolution conversion information input from the resolution conversion unit 504 in the re-encoding parameter determination unit 502.

  When the process is started, the re-encoding parameter determination unit 502 initializes the control variable i (S1401). Next, the re-encoding parameter determination unit 502 determines whether or not (2 ^ i) × (2 ^ i) PU is included in the LCU that is the block to be re-encoded (S1402). Here, 2 ^ i represents 2 to the power of i. For example, when i = 2, (2 ^ i) * (2 ^ i) PU is synonymous with 4 * 4PU.

  When it is determined in step S1402 that (2 ^ i) × (2 ^ i) PU is included in the LCU (YES in S1402), each (2 ^ i) × (2 ^ i existing in the LCU ) Four PUs are grouped together and the corresponding representative prediction mode is determined (S1403). Further, the re-encoding parameter determination unit 502 sets a flag indicating the representative prediction mode (S1404). In step S1404, the re-encoding parameter determination unit 502 sets a flag indicating the representative prediction mode. If n ≧ 2, the re-encoding parameter determination unit 502 sets the flag last in the process in the re-encoding target block illustrated in FIG. The determined mode is determined as the representative prediction mode.

  After the processing of step S1404, or when (2 ^ i) × (2 ^ i) PU is not included in the LCU (NO in S1402), the re-encoding parameter determination unit 502 determines whether the variable i is equal to n + 1. Is determined (S1405). Here, n is resolution conversion information, which means that the resolution conversion unit 504 multiplies the decoded image by 1 / (2 ^ n) in the horizontal direction and the vertical direction, respectively. That is, when n = 1, it indicates that the horizontal and vertical directions are each halved.

  If it is determined in step S1405 that the variable i is equal to n + 1 (YES in S1405), the processing of the LCU that is the block to be re-encoded is terminated. If it is determined in step S1405 that the variable i is not equal to n + 1 (NO in S1405), the variable i is incremented (S1406), and the processing from step S1402 to step S1405 is performed.

  For example, when n = 1, it means that the resolution conversion unit 504 halves the decoded image in the horizontal direction and the vertical direction (FIG. 13B). In this case, before the resolution conversion by the resolution conversion unit 504, the PU of the image before resolution conversion for which the representative prediction mode needs to be obtained is 4 × 4 PU. That is, i = 2. Therefore, in step S1405, i = n + 1, and the process ends.

  Further, when n = 2, it means that the resolution conversion unit 504 multiplies the decoded image by 1/4 in the horizontal direction and in the vertical direction (FIG. 13C). In this case, before the resolution conversion by the resolution conversion unit 504, the PU of the image before the resolution conversion for which the representative prediction mode needs to be obtained is 4 × 4 PU and 8 × 8 PU. That is, i = 3. Therefore, since i ≠ (n + 1) in step S1405, the variable i is incremented (S1406), and the processing from step S1402 to step S1405 is performed on the 8 × 8 PU.

  Next, a case where 4 × 4 PU and 8 × 8 PU are mixed in a 16 × 16 pixel area before resolution conversion (FIG. 13A) will be described. First, when i = 2, in step S1403, the representative prediction mode is determined for 8 × 8 pixels including four 4 × 4 PUs of the image before resolution conversion. Next, when i = 3, in step S1403, the representative prediction mode for 16 × 16 pixels composed of three 8 × 8 PUs and 4 × 4 PUs of the image before resolution conversion is further determined. The same processing is performed when n is 3 or more.

  FIG. 15 is a flowchart illustrating a process for determining a re-encoding parameter in the re-encoding parameter determination unit 502 of the present embodiment. In FIG. 15, the same reference numerals are given to portions that are not different from the first embodiment.

  In this embodiment, H.264 is used. When either H.264 4 × 4 pixel block prediction or 8 × 8 pixel block prediction is selected in the process of step S1501, whether or not there is a flag indicating whether or not the corresponding block prediction mode is the representative prediction mode Use information. Note that when the prediction mode of the corresponding block is the representative prediction mode (when the flag is set), the prediction block size is determined using Equation 2 described later.

  FIG. 16 shows that the re-encoding parameter determination unit 502 performs 4 × 4 pixel block prediction or 8 × 8 pixel block prediction based on the resolution conversion information input from the resolution conversion unit 504 in the process of step S1501 of FIG. It is a figure which shows the method of selecting either.

  FIG. 16A shows 16 × 16 pixels after resolution conversion. The 16 × 16 pixel image shown in FIG. 16A corresponds to the 16 × 16 pixel image shown in FIG. The shaded portion in FIG. 16A is a PU having a representative prediction mode identified from the resolution conversion information input from the resolution conversion unit 504, and the other portions reuse the prediction mode before the resolution conversion. PU.

  Further, when 4 × 4 PU and 8 × 8 PU are mixed in the image after resolution conversion as in the portion indicated by the dotted line in FIG. Before re-encoding with H.264, either 4 × 4 pixel block prediction or 8 × 8 pixel block prediction needs to be selected. As described in the first embodiment, this is because the H.264. This is because in H.264, 8 × 8 pixel block prediction and 4 × 4 pixel block prediction cannot be used together in one macroblock.

  In the present embodiment, the re-encoding parameter determination unit 502 calculates Equation 2 based on the weighted prediction result of the number of 4 × 4 PUs and the number of 8 × 8 PUs in the 16 × 16 pixel region of HEVC. Using H. H.264 prediction block size is determined.

  As in the first embodiment, the numbers of 4 × 4 PU and 8 × 8 PU are expressed as num_4 × 4pu and num_8 × 8pu, respectively. Further, the weighting factor is expressed as β. Note that the weighting factor α is the same as the weighting factor α used in Equation 1 of the first embodiment.

β × num — 4 × 4pu ≦ α × num — 8 × 8pu (Formula 2)
Based on the comparison result according to Expression 2, the re-encoding parameter determination unit 502 selects either 4 × 4 pixel block prediction or 8 × 8 pixel block prediction.

  The weight coefficient β is a coefficient that is variable based on the number of 4 × 4 PUs having the representative prediction mode. In the present embodiment, the re-encoding parameter determination unit 502 selects 8 × 8 pixel block prediction when Expression 2 is satisfied (FIG. 16C), and selects 4 × 4 pixel block prediction when not satisfied. (FIG. 16B).

  Next, an example of selecting a prediction block size in step S1501 of FIG. 15 in the present embodiment will be described with reference to FIG. In FIG. 16, there is one 4 × 4 PU having the representative prediction mode. For example, the weighting coefficient β based on this number is set to 0.2. The weighting factor α is set to α = 1.1 as in the first embodiment. In FIG. 16, since the number of 4 × 4 PUs is 8, num — 4 × 4pu is 8, and since the number of 8 × 8 PUs is 2, num — 8 × 8pu is 2. Therefore, since Equation 2 is satisfied when β = 0.2 and α = 1.1, the re-encoding parameter determination unit 502 selects 8 × 8 pixel block prediction (FIG. 16C). Since Equation 2 is not satisfied when β = 0.3, the recoding parameter determination unit 502 selects 4 × 4 pixel block prediction (FIG. 16B).

  Returning to FIG. 15, the re-encoding parameter determination process by the re-encoding parameter determination unit 502 will be described. The re-encoding parameter determination unit 502 determines the prediction block size used for re-encoding (S1501), and then determines the prediction mode used for re-encoding (S1502). In step S1502, the re-encoding parameter determination unit 502 determines a prediction mode that is the same as the prediction mode (including the representative prediction mode) of each corresponding PU after resolution conversion, or close to the prediction direction, and ends the process. To do.

  Note that the method for determining the weighting coefficient β in Equation 2 is not limited to the method described in the present embodiment. That is, in the present embodiment, the value of the weighting factor β depends on the number of 4 × 4 PUs having the representative prediction mode, but may be variable based on other parameters. For example, not only the number of 4 × 4 PUs having the representative prediction mode, Parameters may be adaptively set based on a code amount generated as a result of selecting either 4 × 4 pixel block prediction or 8 × 8 pixel block prediction at the time of re-encoding to H.264. In the present embodiment, the weighting factor β is multiplied by the left side in Equation 2, but the present invention is not limited to this. That is, of course, the weight coefficient β may be multiplied by the right side of Equation 2.

  As a result, this embodiment can be The prediction block size of HEVC is changed to H.264 without increasing the processing load for searching for the prediction block size when re-encoding to H.264. H.264 can be appropriately converted into a predicted block size for re-encoding. In addition, this embodiment is H.264. The prediction mode of HEVC is changed to H.264 without increasing the processing load for searching for the prediction mode when re-encoding to H.264. H.264 can be appropriately converted into a predicted block size for re-encoding.

  Furthermore, in this embodiment, based on the resolution conversion information used when the resolution conversion is performed on the decoded image obtained by decoding the first encoded stream, the H.264 format is used. A prediction mode to be used when re-encoding with H.264 is selected. This makes it possible to adaptively switch the prediction block size at the time of re-encoding based on the reusability of the prediction mode before resolution conversion. The reusability refers to the HEVC average value prediction mode, horizontal prediction mode, or vertical prediction mode. H.264 16 × 16 pixel prediction can be used, the same mode as the HEVC prediction mode is used in H.264. H.264 is used.

  Note that the present invention is not limited to this, and the function of the re-encoding parameter determination unit 502 is provided inside any one of the decoding unit 101, the encoding unit 103, and the resolution conversion unit 504 shown in FIG. May be.

  Further, only a part of the re-encoding parameters determined by the re-encoding parameter determination unit 502 may be used by the encoding unit 103. For example, only the prediction block size among the re-encoding parameters may be used, and the prediction mode may be searched by the encoding unit 103. In addition, the re-encoding parameter determined by the re-encoding parameter determination unit 502 may be used as an initial value when the encoding unit 103 searches for a more optimal re-encoding parameter. That is, after the re-encoding parameter determination unit 502 determines the re-encoding parameter, the re-encoding parameter may be searched again.

<Embodiment 4>
In the first embodiment, the second embodiment, and the third embodiment, each processing unit illustrated in FIGS. 1, 10, and 12 has been described as being configured by hardware. However, the processing performed by each processing unit shown in these figures may be executed by a computer program.

  FIG. 17 is a block diagram illustrating a configuration example of hardware of a computer that executes processing performed by each processing unit of the coding scheme conversion apparatus according to the first embodiment, the second embodiment, and the third embodiment.

  The CPU 1701 controls the entire computer using computer programs and data stored in the RAM 1702 and the ROM 1703, and executes each process described above as performed by the encoding method conversion apparatus according to the above-described embodiment. That is, the CPU 1701 functions as each processing unit shown in FIGS.

  The RAM 1702 has an area for temporarily storing computer programs and data loaded from the external storage device 1706, data acquired from the outside via an I / F (interface) 1707, and the like. Further, the RAM 1702 has a work area used when the CPU 1701 executes various processes. That is, the RAM 1702 can be allocated as, for example, a frame memory or can provide various other areas as appropriate.

  The ROM 1703 stores setting data and a boot program for the computer.

  The operation unit 1704 is configured by a keyboard, a mouse, and the like, and various instructions can be input to the CPU 1701 by the user of the computer.

  A display unit 1705 displays a processing result by the CPU 1701. Further, the display unit 1705 is constituted by a liquid crystal display, for example.

  The external storage device 1706 is a large-capacity information storage device represented by a hard disk drive device. The external storage device 1706 stores an operating system (OS) and computer programs for causing the CPU 1701 to realize the functions of the units illustrated in FIGS. 1, 10, and 12. Furthermore, each image as a processing target may be stored in the external storage device 1706.

  Computer programs and data stored in the external storage device 1706 are appropriately loaded into the RAM 1702 under the control of the CPU 1701 and are processed by the CPU 1701.

  The I / F 1707 can be connected to a network such as a LAN or the Internet, or another unit such as a projection device or a display device. The computer can acquire various kinds of information via the I / F 1707 and send it out. You can do it.

  A bus 1708 connects the above-described units.

  The operation in the above-described configuration is controlled by the CPU 1701 centering on the operation described in the above flowchart.

<Other embodiments>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (17)

Decoding means for decoding a first encoded stream encoded by using a first encoding parameter in the first encoding scheme and generating a decoded image;
First determination means for determining whether or not a first prediction block size included in the first encoding parameter is equal to or larger than a predetermined size;
Second determination means for determining whether or not the first prediction mode included in the first encoding parameter is a predetermined mode;
Determining means for determining a second predicted block size based on the result determined by the first determining means and the result determined by the second determining means;
Encoding means for encoding the decoded image generated by the decoding means by a second encoding method using a second encoding parameter including the second predicted block size determined by the determining means; ,
A coding method conversion apparatus comprising:   The determining means determines that the first prediction block size is greater than or equal to the predetermined size by the first determination means, and the first prediction mode is the predetermined prediction by the second determination means. 2. The encoding method conversion apparatus according to claim 1, wherein, when it is determined as a mode, the second prediction block size is determined to be the predetermined size. 3.   The determining unit determines that the first prediction block size is smaller than the predetermined size by the first determination unit, or the first prediction mode is set to the predetermined unit by the second determination unit. 3. The code according to claim 1, wherein when it is determined that the mode is not the mode, the second predicted block size is determined to be smaller than the predetermined size. 4. Conversion method converter.   The determining unit determines that the first prediction block size is smaller than the predetermined size by the first determination unit, or the first prediction mode is set to the predetermined unit by the second determination unit. Of the prediction block sizes that can be used in the second encoding method, the number of prediction modes that can be used in the prediction block size is the number of prediction modes in the first encoding method. The prediction block size corresponding to the number of prediction modes that can be used in the first prediction block size is determined as the second prediction block size, according to any one of claims 1 to 2. The encoding method conversion apparatus described. An obtaining unit for obtaining statistical information of the first encoded stream;
A third determination unit that determines whether or not the statistical information acquired by the acquisition unit is equal to or less than a predetermined value;
The determination unit is configured to perform the second encoding based on the result determined by the first determination unit, the result determined by the second determination unit, and the result determined by the third determination unit. The encoding method conversion apparatus according to claim 1, wherein at least one of a second prediction block size and a second conversion block size included in the parameter is determined.   The determining means determines that the first prediction block size is greater than or equal to the predetermined size by the first determination means, and the first prediction mode is the predetermined prediction by the second determination means. When the mode is determined and the statistical information is determined to be equal to or smaller than the predetermined value by the third determination unit, the second predicted block size is determined to be the predetermined size. The encoding method conversion apparatus according to claim 5, wherein:   The determining unit determines that the first prediction block size is smaller than the predetermined size by the first determination unit, or the first prediction mode is set to the predetermined unit by the second determination unit. The second predictive block size is smaller than the predetermined size when it is determined that the mode is not the mode of the above or when the statistical information is determined to be larger than the predetermined value by the third determining unit The encoding method conversion apparatus according to any one of claims 5 to 6, wherein the size is determined. The determining means determines that the first prediction block size is greater than or equal to the predetermined size by the first determination means, and the first prediction mode is the predetermined prediction by the second determination means. The second transform block size is determined to be the first size when the mode is determined and the statistical information is determined to be equal to or smaller than the predetermined value by the third determination unit;
Whether the first determination block size is determined to be smaller than the predetermined size by the first determination unit, or whether the first prediction mode is not the predetermined mode by the second determination unit, Alternatively, when the statistical information is determined to be larger than the predetermined value by the third determination unit, the second transform block size is determined as the second size,
6. The encoding method conversion apparatus according to claim 5, wherein the first size is larger than the second size.   The statistical information is at least one of parameters indicating the code amount of the first encoded stream, the prediction residual, and the presence / absence of a significant coefficient, which is obtained when the decoding unit decodes the first encoded stream. The encoding method conversion apparatus according to any one of claims 5 to 8, wherein the encoding system conversion apparatus includes information including:   The encoding method conversion according to any one of claims 1 to 9, wherein the predetermined mode is any one of an average value prediction mode, a horizontal prediction mode, and a vertical prediction mode. apparatus. Further, the first coding parameter includes a third prediction block size different from the first prediction block size,
The determining means determines the second predicted block size included in the second encoding parameter based on the number of the first predicted block size and the number of the third predicted block size. The encoding method conversion apparatus according to claim 1.   The determination means determines the second prediction mode included in the second encoding parameter based on the first prediction mode included in the first encoding parameter. The encoding system conversion apparatus as described in any one of Claim 1 or Claim 5.   6. The code according to claim 1, wherein the first prediction block size and the second prediction block size are block sizes used in intra prediction. Conversion method converter. Decoding means for decoding a first encoded stream encoded by using a first encoding parameter in the first encoding scheme and generating a decoded image;
Conversion means for converting the resolution of the decoded image generated by the decoding means using resolution conversion information;
Encoding means for encoding the decoded image, the resolution of which has been converted by the conversion means, using the second encoding parameter in the second encoding method;
First determination means for determining a prediction mode included in the second encoding parameter based on the resolution conversion information;
A coding method conversion apparatus comprising:   15. The encoding method conversion apparatus according to claim 14, further comprising second determination means for determining a predicted block size included in the second encoding parameter based on the resolution conversion information. Decoding a first encoded stream encoded using the first encoding parameter in the first encoding scheme to generate a decoded image;
A first determination step of determining whether or not a first prediction block size included in the first encoding parameter is equal to or larger than a predetermined size;
A second determination step of determining whether or not the first prediction mode included in the first encoding parameter is a predetermined mode;
A determination step of determining a second prediction block size based on the result determined by the first determination step and the result determined by the second determination step;
An encoding step of encoding the decoded image generated in the decoding step by a second encoding method using a second encoding parameter including the second predicted block size determined in the determining step; ,
A coding method conversion method characterized by comprising:   The program for functioning a computer as each means of the encoding system converter of Claim 1.

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