JP2018007079A - Encoder, decoder, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve prediction accuracy and encoding efficiency, without increasing the information amount transmitted by the encoder, and without increasing the calculation time on the encoder side.SOLUTION: An encoder 1 includes a composite region determination unit 12 configured to determine a composite region X where a prediction image is generated from adjacent pixels not yet decoded in an encoding object block CU/TU, on the basis of the intra-prediction mode, and an intra-prediction unit 13 configured to change the generation method of a prediction image of each region, on the basis of whether or not included in the composite region X.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an encoding device, a decoding device, and a program.

  In a moving picture coding system represented by H.265 / HEVC (High Efficiency Video Coding), there are two types of inter prediction using temporal correlation between frames and intra prediction using spatial correlation within a frame. After generating a residual signal by performing prediction while switching prediction, a stream obtained by performing orthogonal transform processing, loop filter processing, and entropy coding processing is output.

  In intra prediction in HEVC, a total of 35 types of modes such as Planar prediction, DC prediction, and direction prediction are prepared, and configured to perform intra prediction using adjacent decoded reference pixels according to the mode determined by the encoder. Has been.

  Here, in intra prediction, a specified value (“512” for a 10-bit moving image) is used for a CU that does not have an adjacent decoded reference pixel, such as a CU (Coding Unit) located at the upper left in the frame. By the process of filling in, reference pixels used when generating a predicted image are created.

  Further, in the conventional HEVC, since the encoding process is performed in the order of raster scan from the upper left, the reference pixel may not be decoded. In such a case, a predicted image is generated using a value obtained by extrapolating the nearest decoded reference pixel by zero order.

  The CU is divided into a plurality of blocks (TU: Transform Unit) and subjected to orthogonal transform processing. In HEVC, the intra prediction mode which shows the kind of intra prediction to apply is common within CU, and prediction is performed using the common intra prediction mode with respect to several TU.

  In intra prediction, as shown in FIG. 7, the reference pixel N located in the lower left or upper right of CU # X is often not decoded by the encoding process in the raster scan order. In such a case, the decoding is not completed. When the direction prediction from the direction in which the reference pixel exists is performed, there is a problem that the prediction accuracy is lowered and the encoding efficiency is reduced.

  Hereinafter, this problem will be specifically described with reference to FIGS. 8A to 8D. FIG. 8 shows an example of intra prediction in conventional HEVC.

  In this example, as shown in FIG. 8A, as in the case of the example of FIG. 7, all the reference pixels of CU # A1 (upper left CU in the frame) have been decoded. Similarly, as shown in FIG. 8C, all the reference pixels of CU # A3 (lower left CU in the frame) have been decoded.

  On the other hand, as shown in FIG. 8B, the reference pixels W1 to W3 located in CU # A1 have been decoded, but the reference pixels B1 to B4 located in CU # A3 have not been decoded. Therefore, it cannot be used as a reference pixel when generating a predicted image of CU # A2 (upper right CU in the frame) as it is.

  Therefore, in the conventional HEVC, as shown in FIG. 8B, the value of the reference pixel W1 positioned at the bottom of the decoded reference pixels W1 to W3 positioned in the CU # A1 is set in the CU # A3. Are copied to undecoded reference pixels B1 to B4 located in the same column.

  Similarly, in the conventional HEVC, as shown in FIG. 8D, the value of the reference pixel B1 located at the bottom of the decoded reference pixels B1 to B3 located in CU # A3 is set to the value of CU # A3. It is defined to copy to an undecoded reference pixel P3 located in the same column in the CU existing on the lower side.

  Therefore, when the direction prediction is performed from the lower left to the upper right as in the example of FIG. 8, most of the generated prediction images are configured by undecoded reference pixels filled with copies, and thus the prediction accuracy is high. There is a problem that the coding efficiency is reduced.

  In order to solve such a problem, in intra prediction in which TU partitioning is performed, in addition to raster scan order (for example, Z type), U type and X type as encoding processing order for a plurality of TUs existing in a CU. A technique for improving prediction accuracy by providing a degree of freedom in the encoding order is known (see Non-Patent Document 1).

Mochizuki et al., “Applied Intra Prediction Method Based on Average Coordinates”, Information Processing Society of Japan, Vol. 2012-AVM-77, No. 12

  However, in the technique prescribed in the above-mentioned Non-Patent Document 1, it is necessary to transmit a flag as to what encoding processing order is used in CU units, which increases the amount of information to be transmitted. In order to select which encoding processing order is better from all the encoding processing orders, it is necessary to try all combinations on the encoding apparatus side, which increases the calculation time on the encoding apparatus side. There was a problem.

  Therefore, the present invention has been made to solve the above-described problem, and predicting without increasing the amount of information transmitted by the encoding apparatus and without increasing the calculation time on the encoding apparatus side. An object is to provide an encoding device, a decoding device, and a program capable of improving accuracy and encoding efficiency.

  A first feature of the present invention is an encoding device configured to divide and encode an original image in frame units constituting a moving image into encoding target blocks, and is based on an intra prediction mode. , Based on whether or not included in the synthesis region, a synthesis region determination unit configured to determine a synthesis region in which a predicted image is generated from neighboring pixels that have not been decoded in the encoding target block, The gist is to include an intra prediction unit configured to change a method of generating a predicted image of each region.

  A second feature of the present invention is a decoding device configured to decode an original image in units of frames constituting a moving image into blocks to be encoded, and based on an intra prediction mode, Based on a synthesis region determination unit configured to determine a synthesis region in which a prediction image is generated from neighboring pixels that have not been decoded in the encoding target block, and whether or not each region is included in the synthesis region And an intra prediction unit configured to change the method of generating the predicted image.

  The gist of the third feature of the present invention is a program for causing a computer to function as the encoding device described in the first or second feature.

  The gist of a fourth feature of the present invention is a program for causing a computer to function as the decoding device described in the first or second feature.

  According to the present invention, an encoding apparatus that can improve prediction accuracy and encoding efficiency without increasing the amount of information transmitted by the encoding apparatus and without increasing the calculation time on the encoding apparatus side. A decoding device and a program can be provided.

FIG. 1 is a functional block diagram of an encoding apparatus 1 according to the first embodiment. FIG. 2 is a diagram illustrating an example of how a predicted image is generated in the first embodiment. FIG. 3 is a diagram illustrating an example of how a predicted image is generated in the first embodiment. FIG. 4 is a functional block diagram of the decoding device 3 according to the first embodiment. FIG. 5 is a flowchart showing operations of the encoding device 1 and the decoding device 3 according to the first embodiment. FIG. 6 is a diagram illustrating an example of how a predicted image is generated in the second embodiment. FIG. 7 is a diagram illustrating an example of a state in which a predicted image is generated in conventional HEVC. FIG. 8 is a diagram illustrating an example of a state in which a predicted image is generated in conventional HEVC.

(First embodiment)
Hereinafter, the encoding device 1 and the decoding device 3 according to the first embodiment of the present invention will be described with reference to FIGS. Here, the encoding device 1 and the decoding device 3 according to the present embodiment are configured to support intra prediction in HEVC.

  The encoding device 1 according to the present embodiment is configured to divide and encode a frame-unit original image constituting a moving image into encoding target blocks. In the present embodiment, it is assumed that all pixels adjacent to the left side and the upper side of the encoding target CU have been decoded.

  Also, the encoding device 1 according to the present embodiment may be configured to be able to divide a CU into a plurality of TUs. Therefore, in this embodiment, the encoding target block may be a CU or a TU. Hereinafter, in this embodiment, a case where a CU is used as an encoding target block will be described as an example.

  In this embodiment, the case where the raster scan order (Z type as shown in FIGS. 7 and 8) used in the conventional HEVC is used as the CU encoding order and decoding order is taken as an example. However, as such encoding order and decoding order, other encoding orders and decoding orders such as U type and X type may be used.

  As shown in FIG. 1, the encoding apparatus 1 according to the present embodiment includes an intra prediction mode determination unit 11, a synthesis region determination unit 12, an intra prediction unit 13, a residual signal generation unit 14, an orthogonal transform / A quantization unit 15, an inverse orthogonal transform / inverse quantization unit 16, a local decoded image generation unit 17, a memory unit 18, and an entropy encoding unit 19 are provided.

  The intra prediction mode determination unit 11 is configured to determine an optimal intra prediction mode to be applied to the CU.

  Based on the intra prediction mode determined by the intra prediction mode determination unit 11, the synthesis region determination unit 12 is configured to determine a synthesis region X in which a predicted image is generated from neighboring pixels that have not been decoded in the CU. Yes.

  Specifically, as illustrated in FIG. 2, the synthesis region determination unit 12 determines that the direction of the intra prediction mode determined by the intra prediction mode determination unit 11 is a direction from the lower left to the upper right (that is, from the lower left to the upper right). When the direction prediction is performed), the synthesis region X in which the predicted image is generated from the neighboring pixels B1 to B4 that have not been decoded in the CU # A2 may be determined.

  The present invention is also applicable to the case where the direction of the intra prediction mode determined by the intra prediction mode determination unit 11 is the direction from the upper right to the lower left (that is, the direction prediction is performed from the upper right to the lower left). Although possible, hereinafter, the case where the direction of the intra prediction mode determined by the intra prediction mode determination unit 11 is the direction from the lower left to the upper right (that is, the case where the direction prediction is performed from the lower left to the upper right) is an example. Will be described.

  In the drawings of the present specification, the arrow indicating the direction (prediction direction) of the intra prediction mode is assumed to be directed from the pixel subject to intra prediction to the reference pixel, as described in the HEVC standard (the same applies hereinafter). .

  The intra prediction unit 13 is configured to change the generation method of the predicted image of each region based on whether or not it is included in the synthesis region X determined by the synthesis region determination unit 12.

  Specifically, as illustrated in FIG. 3A, the intra prediction unit 13 is a region that is not included in the synthesis region X in CU # A2 (that is, a region in which the reference pixels W1 to W3 have been decoded). In Y, using the intra prediction mode determined by the intra prediction mode determination unit 11, a prediction image is generated based on the decoded reference pixels W1 to W3.

  On the other hand, as shown in FIG. 3B, the intra prediction unit 13 predefines in the region included in the synthesis region X (that is, the region where the reference pixels B2 to B4 have not been decoded) in CU # A2. The predicted image is generated using the predicted method.

  Here, the prediction method defined in advance includes, for example, a prediction method for generating a prediction image based on an average of values of adjacent decoded reference pixels, in addition to intra prediction such as DC prediction and Planar prediction.

  Note that if the encoding device 1 and the decoding device 3 determine the prediction method in advance, the prediction method is applied from the encoding device 1 to the decoding device 3 regardless of the prediction method used. There is no need to transmit a new flag to indicate.

  Further, since the synthesis region determined by the synthesis region determination unit 12 can be uniquely determined depending on the direction of the intra prediction mode and whether or not the adjacent pixel has been decoded, the encoding device 1 to the decoding device 3 On the other hand, it is not necessary to transmit a flag indicating which region is a new synthesis region.

  For example, as illustrated in FIG. 3B, the intra prediction unit 13 uses the Planar prediction at the position of the pixel X1 in the region included in the synthesis region X in CU # A2, and uses the pixel W3 and the pixel D1. The prediction image may be generated by combining the pixel D2 and the pixel D4. Here, the value of the pixel B4 is copied to the pixel D4, and the value of the pixel W1 is copied to the pixel B4.

  The residual signal generation unit 14 is configured to generate a residual signal based on the difference between the predicted image generated by the intra prediction unit 13 and the original image.

  The orthogonal transform / quantization unit 15 is configured to perform orthogonal transform processing and quantization processing on the residual signal generated by the residual signal generation unit 14 and generate a quantized transform coefficient. .

  The inverse orthogonal transform / inverse quantization unit 16 performs inverse quantization processing and inverse orthogonal transform processing on the quantized transform coefficient generated by the orthogonal transform / quantization unit 15 again to obtain a quantized residual signal. It is configured to generate a difference signal.

  The local decoded image generation unit 17 generates a local decoded image by adding the prediction image generated by the intra prediction unit 13 to the quantized residual signal generated by the inverse orthogonal transform / inverse quantization unit 16. Is configured to do.

  The memory unit 18 is configured to hold the local decoded image generated by the local decoded image generation unit 17 so as to be usable as a reference image.

  The entropy encoding unit 19 is configured to perform entropy encoding processing on the flag information including the intra prediction mode determined by the intra prediction mode determination unit 11 and the quantized transform coefficient and output the stream. Yes.

  In addition, the decoding device 3 according to the present embodiment is configured to decode a frame-unit original image constituting a moving image by dividing it into CUs. Also, the decoding device 3 according to the present embodiment is configured to be able to divide a CU into a plurality of TUs, similarly to the encoding device 1 according to the present embodiment.

  As shown in FIG. 4, the decoding device 3 according to the present embodiment includes an entropy decoding unit 31, a synthesis region determination unit 32, an intra prediction unit 33, an inverse quantization / inverse transform unit 34, and a local decoded image generation. A unit 35 and a memory unit 36 are provided.

  The entropy decoding unit 31 is configured to decode transform coefficients, flag information, and the like from the stream output from the encoding device 1. Here, the transform coefficient is a quantized transform coefficient obtained by the encoding apparatus 1 as a signal encoded by dividing an original image in frame units into CUs. The flag information includes accompanying information such as a prediction mode.

  Based on the intra prediction mode output by the entropy decoding unit 31, the synthesis region determination unit 32 is configured to determine a synthesis region X in which a predicted image is generated from adjacent pixels that have not been decoded in the CU.

  Specifically, as illustrated in FIG. 2, the synthesis region determination unit 32 determines that the direction of the intra prediction mode output by the entropy decoding unit 31 is from the lower left to the upper right (that is, from the lower left to the upper right). In the case where the direction prediction is performed), the synthesis region X in which the predicted image is generated from the neighboring pixels B1 to B4 that have not been decoded in the CU # A2 may be determined.

  The intra prediction unit 33 may be configured to generate a prediction image using the synthesis region X determined by the synthesis region determination unit 32 and the intra prediction mode output by the entropy decoding unit 31.

  Specifically, similarly to the intra prediction unit 13, the intra prediction unit 33 determines the generation method of the predicted image of each region based on whether or not it is included in the synthesis region X determined by the synthesis region determination unit 12. Is configured to change.

  For example, as illustrated in FIG. 3A, the intra prediction unit 33 in CU # A2 includes a region Y that is not included in the synthesis region X (that is, a region in which the reference pixels W1 to W3 have been decoded) Y. The intra prediction mode output by the entropy decoding unit 31 is used to generate a prediction image based on the decoded reference pixels W1 to W3.

  On the other hand, as shown in FIG. 3B, the intra prediction unit 33, in the area included in the synthesis area X in CU # A2 (that is, the area where the reference pixels B2 to B4 have not been decoded), A prediction image is generated using a predetermined prediction method.

  The inverse quantization / inverse transform unit 34 performs an inverse quantization process and an inverse transform process (for example, an inverse orthogonal transform process) on the quantized transform coefficient output from the entropy decoding unit 31 to obtain a residual. It is configured to generate a signal.

  The local decoded image generation unit 35 is configured to generate a local decoded image by adding the prediction image generated by the intra prediction unit 33 and the residual signal generated by the inverse quantization / inverse transformation unit 34. Yes.

  The memory unit 36 is configured to hold the local decoded image generated by the local decoded image generation unit 35 so as to be usable as a reference image for intra prediction and inter prediction.

  FIG. 5 shows a flowchart for explaining an example of an operation for generating a prediction image by the encoding device 1 and the decoding device 3 according to the present embodiment.

  First, with reference to FIG. 5, an example of an operation for generating a prediction image by the encoding device 1 according to the present embodiment will be described.

  As illustrated in FIG. 5, in step S101, the encoding device 1 determines an optimal intra prediction mode to be applied to the CU.

  In step S102, the encoding device 1 determines a synthesis region X in which a predicted image is generated from adjacent pixels that have not been decoded in the CU, based on the intra prediction mode determined in step S101.

  In step S103, the encoding apparatus 1 determines whether or not a region for generating a predicted image is included in the synthesis region in the CU. If “No”, the operation proceeds to step S104. If “Yes”, the operation proceeds to step S105.

  In step S104, the encoding apparatus 1 generates a prediction image based on the decoded reference pixel using the intra prediction mode determined in step S101.

  In step S105, the encoding apparatus 1 generates a prediction image using the above-described predetermined prediction method.

  Secondly, with reference to FIG. 5, an example of an operation for generating a predicted image by the decoding device 3 according to the present embodiment will be described.

  As illustrated in FIG. 5, in step S101, the decoding device 3 determines an intra prediction mode based on information obtained by entropy decoding processing.

  In step S102, the decoding device 3 determines a synthesis region X in which a predicted image is generated from adjacent pixels that have not been decoded in the CU, based on the intra prediction mode determined in step S101.

  In step S103, the decoding device 3 determines whether or not a region for generating a predicted image is included in the synthesis region in the CU. If “No”, the operation proceeds to step S104. If “Yes”, the operation proceeds to step S105.

  In step S104, the decoding device 3 generates a prediction image based on the decoded reference pixels using the intra prediction mode determined in step S101.

  In step S105, the decoding device 3 generates a prediction image using the above-described predetermined prediction method.

  According to the encoding device 1 and the decoding device 3 according to the present embodiment, when an undecoded pixel is included in the reference destination in the direction of the intra prediction mode (prediction direction), the adjacent decoded reference pixel is copied. By generating a new predicted image by combining the predicted image generated using the reference pixel interpolated with the predicted image generated using the predetermined prediction method, it is possible to suppress a decrease in prediction accuracy. .

(Second Embodiment)
Hereinafter, with reference to FIG. 6, the encoding device 1 and the decoding device 3 according to the second embodiment of the present invention are different from the above-described encoding device 1 and the decoding device 3 according to the first embodiment. This will be explained with a focus on.

  In the encoding device 1 according to the present embodiment, the intra prediction unit 13 is configured such that when a predetermined condition is satisfied in a boundary region between a region included in the synthesis region X and a region Y not included in the synthesis region X, A smoothing filter is applied to the predicted image in the boundary region.

  Similarly, in the decoding device 3 according to the present embodiment, the intra prediction unit 33, when a predetermined condition is satisfied in the boundary region between the region included in the synthesis region X and the region Y not included in the synthesis region X In addition, a smoothing filter is applied to the predicted image in the boundary region.

  For example, in the example of FIG. 6, the boundary regions include pixels X1, X2, X3, and X4 in the region included in the combined region X and pixels Y1, Y2, and Y3 in the region Y not included in the combined region X. This corresponds to the area that is located.

  Further, as the predetermined condition, the discontinuity in the boundary region is higher than a predetermined threshold. Here, as the evaluation of discontinuity, for example, there is a method represented by a linear combination such as a horizontal difference, a vertical difference, or a diagonal difference.

  That is, the intra prediction unit 13 and the intra prediction unit 33 apply a smoothing filter to the prediction image of the boundary region when the value of the discontinuity evaluation in the boundary region is higher than a predetermined threshold. It is configured.

  For example, in the example of FIG. 6, the intra prediction unit 13 and the intra prediction unit 33, when the discontinuity evaluation value in the boundary region is higher than a predetermined threshold, the pixels in the region included in the synthesis region X A smoothing filter is configured to be applied to a predicted image in a region where pixels Y1, Y2, and Y3 in a region Y not included in the combined region X and X1, X2, X3, and X4 are located.

  In the example of FIG. 6, the intra prediction unit 13 and the intra prediction unit 33 also apply a smoothing filter to the predicted image in the region where the pixels X5, X6, and X7 in the region included in the synthesis region X are located. It is configured as follows.

  Here, by sharing the above-described predetermined threshold between the encoding device 1 and the decoding device 3, it is not necessary to transmit a new flag from the encoding device 1 to the decoding device 3.

  According to the encoding device 1 and the decoding device 3 according to the present embodiment, the discontinuity of the boundary region caused by changing the prediction image generation method of each region based on whether or not it is included in the synthesis region X Can be reduced, and the encoding performance can be improved.

(Third embodiment)
Hereinafter, with reference to FIG. 6, about the encoding apparatus 1 and the decoding apparatus 3 which concern on the 3rd Embodiment of this invention, the encoding apparatus 1 and the decoding apparatus 3 which concern on the above-mentioned 1st and 2nd embodiment, The difference will be described below.

  In the encoding device 1 and the decoding device 3 according to the present embodiment, the intra prediction unit 13 and the intra prediction unit 33 are prediction images generated using a conventional HEVC prediction method in a region included in the synthesis region X ( Prediction by weighted average of prediction image generated based on undecoded reference pixels embedded by copying) and prediction image generated in synthesis region X (prediction image generated using the above-described predetermined prediction method) It is configured to generate an image.

  Note that, in the encoding device 1 and the decoding device 3 according to the present embodiment, the intra prediction unit 13 and the intra prediction unit 33, in the region included in the synthesis region X, only when the predetermined condition described above is satisfied. A prediction image generated using a prediction method in HEVC (a prediction image generated based on an undecoded reference pixel embedded by copying) and a prediction image generated in the synthesis region X (the above-described predetermined prediction method) The prediction image may be generated by a weighted average of the prediction image generated by using the prediction image.

  In the encoding device 1 and the decoding device 3 according to the present embodiment, the intra prediction unit 13 and the intra prediction unit 33 may be configured to calculate a weighting coefficient used when calculating the weighted average.

  The intra prediction unit 13 and the intra prediction unit 33 may be configured to use a predetermined value as a weighting factor, or the weighting factor using the reliability of the decoded reference pixel when generating the predicted image May be configured to calculate.

  In the example of FIG. 3B, the reliability of the decoded reference pixels W1 to W4 is high, and the reliability of the reference pixels B1 to B4 generated by copying is low. Further, comparing the reliability of the reference pixel B1 and the reliability of the reference pixel B4, the reliability of the reference pixel B4 close to the copy source is higher.

  In addition, the intra prediction unit 13 and the intra prediction unit 33 calculate the weighting factor according to the distance from the boundary region between the region included in the synthesis region X and the region Y not included in the synthesis region X. It may be configured.

  For example, the intra-prediction unit 13 and the intra-prediction unit 33 near the boundary region, the prediction image generated using the prediction method in the conventional HEVC (the prediction generated based on the undecoded reference pixel embedded by copying) The weight of the predicted image (predicted image generated using the above-described predetermined prediction method) generated in the synthesis region X is calculated in a region far from the boundary region. You may calculate so that a coefficient may become strong.

(Other embodiments)
As described above, the present invention has been described by using the above-described embodiment. However, it should not be understood that the description and drawings constituting a part of the disclosure in the embodiment limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  Further, although not particularly mentioned in the above-described embodiment, a program for causing a computer to execute each process performed by the above-described encoding device 1 and decoding device 3 may be provided. Such a program may be recorded on a computer-readable medium. If a computer readable medium is used, such a program can be installed in the computer. Here, the computer-readable medium on which such a program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or a DVD-ROM.

  Alternatively, a chip configured by a memory that stores a program for realizing at least a part of the functions in the encoding device 1 and the decoding device 3 and a processor that executes the program stored in the memory may be provided. Good.

DESCRIPTION OF SYMBOLS 1 ... Coding apparatus 11 ... Intra prediction mode determination part 12 ... Synthesis area | region determination part 13 ... Intra prediction part 14 ... Residual signal generation part 15 ... Orthogonal transformation / quantization part 16 ... Inverse quantization part / inverse orthogonal transformation part 17 ... Local decoded image generation unit 18 ... Memory unit 19 ... Entropy encoding unit 3 ... Decoding device 31 ... Entropy decoding unit 32 ... Synthesis region determination unit 33 ... Intra prediction unit 34 ... Inverse quantization / inverse conversion unit 35 ... Local decoded image Generation unit 36 ... memory unit

Claims (8)

An encoding device configured to divide and encode an original image of a frame unit constituting a moving image into encoding target blocks,
A synthesis region determination unit configured to determine a synthesis region in which a predicted image is generated from neighboring pixels that have not been decoded in the encoding target block, based on an intra prediction mode;
An encoding apparatus comprising: an intra prediction unit configured to change a generation method of a predicted image of each region based on whether or not the region is included in the synthesis region.   The intra prediction unit applies a smoothing filter to a prediction image of the boundary region when a predetermined condition is satisfied in a boundary region between the region included in the synthesis region and the region not included in the synthesis region. The encoding device according to claim 1, wherein the encoding device is configured to be applied.   The intra-prediction unit calculates the prediction image by a weighted average of a prediction image generated based on an undecoded reference pixel embedded by copying and a prediction image generated in the synthesis region in an area included in the synthesis area. The encoding apparatus according to claim 1, wherein the encoding apparatus is configured to generate the encoding apparatus. A decoding device configured to divide and decode an original image of a frame unit constituting a moving image into encoding target blocks,
A synthesis region determination unit configured to determine a synthesis region in which a predicted image is generated from neighboring pixels that have not been decoded in the encoding target block, based on an intra prediction mode;
A decoding apparatus comprising: an intra prediction unit configured to change a generation method of a predicted image of each region based on whether or not the region is included in the synthesis region.   The intra prediction unit applies a smoothing filter to a prediction image of the boundary region when a predetermined condition is satisfied in a boundary region between the region included in the synthesis region and the region not included in the synthesis region. The decoding device according to claim 4, wherein the decoding device is configured to be applied.   The intra-prediction unit calculates the prediction image by a weighted average of a prediction image generated based on an undecoded reference pixel embedded by copying and a prediction image generated in the synthesis region in an area included in the synthesis area. The decoding device according to claim 4, wherein the decoding device is configured to generate the decoding device.   The program for functioning a computer as an encoding apparatus as described in any one of Claims 1 thru | or 3.   The program for functioning a computer as a decoding apparatus as described in any one of Claims 4 thru | or 6.

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