JP2009302786A - Video decoding device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relax mismatching of image boundary parts in error concealment processing. <P>SOLUTION: Encoded image data is decoded by an entropy decoder 14, an inverse quantizer 16, an inverse DCT device 18 and an adder 28. A parsing part of the decoder 14 outputs an error detection signal, including address information of a block, in which an error occurs to an interpolation processing motion vector calculation device 36 and an interpolation data generator 38. The interpolation processing motion vector calculating device 36 extracts motion vector information of a decoded block in the same frame from a frame memory 32 and supplies the average value or the median value of the motion vector information as an interpolation processing motion vector to the interpolation data generator 38. A selector 30 selects the output of the adder 28 when there is no error, and selects interpolation data from the interpolation data generator 38, when there is an undecodable error, in accordance with a control signal from the interpolation data generator 38. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a video decoding apparatus and method for decoding compressed video data, and more specifically to a video decoding apparatus and method having a function of correcting an error.

  In a video decoding apparatus that decodes compressed video data, that is, encoded data of a moving image, the encoded data may not be normally decoded due to a data transmission error. As a process for concealing or repairing such an error, an error concealment process in MPEG4 is known.

For example, as shown in FIG. 10, the error part is interpolated with the image data of the previous frame at the same position as the block in which the error has occurred (see Patent Document 1). That is, when decoding is impossible in the block X of the frame #N, the data of the block X1 is replaced with the decoded data of the block X2 at the same position on the screen in the previous frame # N-1. To interpolate.
Japanese Patent No. 3396378

  In the error concealment process described in Patent Document 1, in the case of an image with intense motion, the continuity of the image is not maintained at the boundary portion between the block that has been successfully decoded and the block that has undergone the interpolation process. Deviation may occur.

  This problem will be described with reference to FIG. It is assumed that an error has occurred in block A during decoding of the decoding target frame P1, and the blocks subsequent to block A could not be normally decoded. In the conventional technique, interpolation processing is performed on the block A of the frame P1 using the preceding frame P2 as a reference frame and a block at the same position as the block A in which an error has occurred. However, in a video with intense motion, the difference between the decoding target frame and the reference frame is large, and the inconsistency at the boundary portion B becomes large like the interpolated image P3.

  It is an object of the present invention to provide a video decoding apparatus and method that alleviates or eliminates such disadvantages.

  A video decoding apparatus according to the present invention includes a decoding unit that decodes encoded image data, a replacement unit that replaces image data in which an undecodable error has occurred with interpolation data, and output image data of the replacement unit. A video decoding device comprising a frame memory for sequentially storing, a reference frame information added to the encoded image data, a storage means for storing motion vector information or camera information, and a non-decoding error error With respect to the generated image data, the reference frame information and the motion vector information or the camera information of the decoded part in the same screen are extracted from the storage means, and a motion vector for interpolation processing and a representative reference frame are determined. The frame according to the motion vector for interpolation processing and the representative reference frame determined by the determination unit; Characterized by comprising an interpolation data generating means for generating the interpolated data from the image data of the representative reference frame stored in memory for the image data generated in the decoding unrecoverable error.

  A video decoding method according to the present invention is a video decoding method for interpolating data of a block in which an undecodable error has occurred with pictures at different times, the decoding step for decoding encoded image data, Reference frame information added to encoded image data, storage step for storing motion vector information or camera information, and motion in a stream of decoded blocks in the same picture according to the picture type of the picture to be decoded Extracting vector information; calculating a motion vector for interpolation processing from motion vector information in the stream; and interpolating data of a block in which a decoding error has occurred using the motion vector for interpolation processing It is characterized by providing.

  According to the present invention, it is possible to alleviate inconsistencies in image boundary portions in error concealment processing.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram of a schematic configuration of an embodiment of the present invention of a video decoding apparatus compatible with H.264 / AVC.

  Video encoded data (transport stream) is input from the data input terminal 10 to the TS processing / camera information extraction device 12. The data structure of the transport stream is shown in FIG. The TS processing / camera information extraction device 12 extracts a PES (Packetized Elementary Stream) packet 52 shown in FIG. 2 from the input transport stream 50. A PES packet payload 54 is extracted from the PES packet 52, and video encoded data (encoded image data) 56 is extracted from the PES packet payload 54. The TS processing / camera information extraction device 12 supplies the extracted video encoded data 56 to the entropy decoding device 14. Further, the TS processing / camera information extracting device 12 extracts camera information added to SEI (Supplemental Enhancement Information) in the access unit in the stream, and supplies it to the camera information memory 13. The camera information is, for example, information indicating the amount of pan / tilt movement and information indicating acceleration when the camera moves.

  The entropy decoding device 14 includes a CAVLC or CABAC entropy decoding block for decoding the entropy encoded portion of the encoded image data from the TS processing / camera information extracting device 12, and a parsing unit for analyzing the video encoded data 56. including. The parsing unit also functions as an error detection unit that detects a parsing error from the output of the entropy decoding block. Details of the parsing error detection will be described later.

  The motion vector extraction device 15 extracts a motion vector from the entropy decoding device 14 and supplies motion vector information to the motion vector memory 17. Here, the motion vector memory 17 may be the same memory as the camera information memory 13.

  The inverse quantization device 16 inversely quantizes the entropy decoded data output from the entropy decoding device 14, and the inverse DCT device 18 performs inverse discrete cosine transform on the output of the inverse quantization device 16. The output of the inverse DCT device 18 is residual data or difference data indicating a difference from the reference image in the case of predictive coding, and is image data itself in the case of non-predictive coding not using prediction. .

  The intra-screen prediction device 20 generates a reference image in intra-screen prediction from the output of the entropy decoding device 14. The motion compensation device 22 and the weighted prediction device 24 receive the decoded image data from the frame memory 32 and generate a reference frame image in the inter-screen prediction by adding the motion compensation processing and the weighting processing. The selector 26 selects the output data of the intra-screen prediction device 20, the output data of the weighted prediction device 24, or the zero value according to the control signal from the entropy decoding device 14, and supplies the selected data to the adder 28. Specifically, the selector 26 selects a zero value for non-predictive coding. The selector 26 selects the output data of the intra prediction apparatus 20 for intra prediction encoding. The selector 26 selects the output data of the weighted prediction device 24 for inter-screen predictive coding.

  The adder 28 adds the data selected by the selector 26 to the output data of the inverse DCT device 18. The output data of the adder 28 is restored image data regardless of whether it is a target for predictive encoding or a target for non-predictive encoding. The adder 28 outputs the addition result to the selector 30.

  In addition, interpolation data is supplied from the interpolation data generation device 38 to the selector 30. The selector 30 selects the output data of the adder 28 or the interpolation data from the interpolation data generation device 38 in accordance with the control signal from the interpolation data generation device 38.

  When the parsing unit of the entropy decoding device 14 does not detect an error, the interpolation data generation device 38 is notified of no error. The interpolation data generation device 38 causes the selector 30 to select the output data of the adder 28 according to the notification of no error. The output image data of the selector 30, that is, the image data (received image data or interpolation data) selected by the selector 30 is sequentially stored in the frame memory 32. The image data stored in the frame memory 32 is sequentially read and output from the output terminal 34 to the outside.

  An operation when the parsing unit of the entropy decoding device 14 detects an error will be described. The parsing unit outputs an error detection signal including address information of the block in which the error has occurred to the interpolation processing motion vector calculation device 36 and the interpolation data generation device 38. When the interpolation processing motion vector calculation device 36 receives the error detection signal, the motion vector calculation device 36 extracts motion vector information of already decoded blocks in the same frame from the motion vector memory 37. Alternatively, camera information (pan / tilt movement amount and acceleration) is extracted from the camera information memory 13. The motion vector calculation device 36 for interpolation processing also calculates the average value (average) or median value (median) of the motion vectors of the decoded blocks. The calculated average value or median value or camera information (pan / tilt motion amount and acceleration) is supplied to the interpolation data generation device 38 as a motion vector for interpolation processing. Reference frame information is also supplied from the frame memory 32 to the interpolation data generating device 38.

  With reference to FIG. 3, a method of calculating a motion vector for interpolation processing using motion vector information of already decoded blocks in the same frame will be described. FIG. 3 shows the screen configuration of the decoding target frame. Blocks A to O indicate decoded blocks. The block P indicates a block that cannot be decoded due to an undecryptable error. In order to interpolate the data of the block P, the motion vector MV for interpolation processing is calculated using the motion vectors of the decoded blocks A to O. That is, MV = average (A, B, C, D,..., O) or MV = median (A, B, C, D,..., O).

  When receiving the error detection signal from the entropy decoding device 14, the interpolation data generation device 38 reads the decoded reference frame image from the frame memory 32. Then, data of a block moved by the motion vector for interpolation processing is extracted from the decoded reference frame image from the block at the same position as the block that cannot be decoded due to the error that cannot be decoded, and interpolation data is generated. That is, when the value of the motion vector for interpolation processing is 0 (zero), interpolation data is generated using data of a block in the same position as a block that cannot be decoded in a decoded reference frame image. . The interpolation data generation device 38 outputs the generated interpolation data to the selector 30.

  The selector 30 switches between the interpolation data from the interpolation data generation device 38 and the image data from the adder 28 in accordance with the processing of the block in which an error has occurred in accordance with the switching control signal from the interpolation data generation device 38. That is, the selector 30 functions as a replacement unit that replaces the undecodable block of the image data from the adder 28 with the interpolation data.

  An error detection operation in the parsing unit of the entropy decoding device 14 will be described. The parsing unit has a function of detecting a plurality of types of errors. For example, it has a function of detecting errors in limit values of ref_idx_l0 and ref_idx_l1. H. In H.264 / AVC, a plurality of profiles such as a main profile, a high profile, and a baseline profile are defined. The possible range of ref_idx_l0 and ref_idx_l1 is defined for each profile. The parsing unit detects whether the result of the entropy decoding process is outside a predetermined range. The parsing unit also has a function of detecting whether or not the number of processed macroblocks is different from the set number of macroblocks. As described above, the parsing unit has an error detection function for detecting, for each item, whether or not the result of the entropy decoding is out of the standard.

  With reference to the flowchart shown in FIG. 4, the operations of the motion vector calculation device 36 for interpolation processing and the interpolation data generation device 38 will be described.

  The interpolation processing motion vector calculation device 36 and the interpolation data generation device 38 wait for an error detection signal from the entropy decoding device 14 (S1). When no error is detected (S1), the motion vector calculation device for interpolation processing 36 and the interpolation data generation device 38 do not function, and the decoding processing of the block to be decoded by the error-free path described with reference to FIG. (Inverse quantization and inverse DCT) are executed (S2). When the error detection signal is input (S1), the interpolation processing motion vector calculation device 36 determines whether the picture type of the block in which the error has occurred is an I picture (S3). If it is determined that the decoding target block is an I picture (S3), camera information is extracted, and a motion vector for interpolation processing is determined based on the camera information (S4).

  When the decoding target block is not an I picture, that is, a P picture or a B picture (S3), motion vector information of a block that has been normally decoded in the same picture is extracted (S5). Then, the average value or median value of the extracted motion vector information is used as the interpolation motion vector information (S6). Instead of steps S5 and S6, a motion vector for interpolation processing may be determined from the camera information extracted in S4.

  After steps S4 and S6, interpolation data is generated from the block data of the reference picture (or reference frame) at the position shifted by the motion vector for interpolation processing determined in S4 and S6 from the same position as the error occurrence block. (S7). Then, the error block data is replaced with interpolation data.

  The above processing is repeated for all the blocks of the decoding target frame (S8). That is, as long as an unprocessed block remains (S8), S1 and subsequent steps are repeated.

  FIG. 5 shows an operational flowchart for the same purpose as in FIG. 4 in a processing method different from that in FIG.

  The interpolation processing motion vector calculation device 36 and the interpolation data generation device 38 wait for an error detection signal from the entropy decoding device 14 (S11). When no error is detected (S11), the motion vector calculation device for interpolation processing 36 and the interpolation data generation device 38 do not function, and the decoding processing of the block to be decoded by the error-free path described with reference to FIG. (Inverse quantization and inverse DCT) are executed (S12). When the error detection signal is input (S11), the interpolation processing motion vector calculation device 36 determines whether the picture type of the block in which the error has occurred is an I picture (S13). If it is determined that the decoding target block is an I picture (S13), a motion vector for interpolation processing is determined based on the extracted camera information (S15).

  When the decoding target block is not an I picture, that is, when it is a P picture or a B picture (S13), it is determined whether or not the ratio of blocks that have been successfully decoded with respect to the decoding target picture is equal to or greater than a threshold ( S14). When the ratio of the decoded blocks is less than the threshold value (S14), the process proceeds to step S15. If the ratio of the decoded blocks is equal to or greater than the threshold (S14), the motion vector information of the blocks that have been successfully decoded is extracted (S16), and the average or median value of the extracted motion vector information is interpolated. The motion vector information for processing is used (S17).

  After steps S15 and S17, interpolation data is obtained from block data of the reference picture (or reference frame) at the position shifted by the motion vector for interpolation processing determined in S15 and S17 from the same position as the error occurrence block. Generate (S18). Then, the error block data is replaced with interpolation data.

  The above process is repeated for all blocks of the decoding target frame (S19). That is, as long as unprocessed blocks remain (S19), S11 and subsequent steps are repeated.

  In this embodiment, camera information is acquired from information added as SEI of an access unit. An example of the structure of the access unit is shown in FIG. However, the camera information may be defined by another method as long as a motion vector can be obtained. Further, although it has been described that the camera information is acquired from the SEI, the camera information may be embedded and transmitted in other locations, and is not limited to being embedded in the SEI.

  A method of selecting a reference frame when data interpolation is performed on a block that cannot be decoded will be described. H. In H.264 / AVC, a P picture and a B picture do not necessarily have one reference frame. That is, as shown in FIG. 7, two frames R0 and R1 can be used as reference frames for the picture A to be decoded. In this embodiment, the data interpolation reference frame for the undecodable block is the same in the frame in which the error has occurred. For example, one frame most frequently used as a reference frame for a decoded block is a data interpolation reference frame, that is, a representative reference frame. In FIG. 7, the decoded block has the frame R0 or R1 as a reference frame, but has six blocks having the frame R0 as a reference frame and nine blocks having the frame R1 as a reference frame. Therefore, in this case, the frame R1 is adopted as the representative reference frame used for data interpolation of the undecodable block.

  With reference to FIG. 8, the error concealment process of a present Example is demonstrated. In FIG. 8, P1 indicates a decoding target frame. Assume that an error occurs in block A during decoding of frame P1, and blocks after block A cannot be decoded normally. Then, it is assumed that the previous frame P2 is selected as a reference frame for interpolation of an undecodable block. Data of the block at the position moved by the interpolation motion vector from the block at the same position as the block where the error has occurred is extracted from the frame P2 and used for the interpolation processing. In the image P3 after the interpolation processing, mismatching is suppressed at the boundary portion B, and a high-quality image is generated.

  When the interpolation process is performed, a reference image may not exist. A countermeasure for this case will be described. FIG. 9A shows the previous frame (time # N-1) of the frame currently being decoded (time #N), and FIG. 9B shows the frame currently being decoded (time #N). Show.

  In the frame currently being decoded (current frame), decoding is performed from the upper left block, and an error occurs in blocks X, A to D, Y, and E to H surrounded by a thick frame and normal decoding is performed. Is no longer possible. Then, it is assumed that the blocks A to H of the previous frame correspond to the blocks A to H of the current frame and can be used as interpolation data from the motion vectors of the blocks already decoded in the current frame. At this time, interpolation data cannot be obtained for the blocks X and Y of the current frame.

  In this embodiment, such blocks X and Y are interpolated by blocks at the same position in the reference frame. In the example shown in FIG. 9, the blocks X and Y of the current frame are interpolated using the blocks A and E at the same position of the reference frame.

  As other methods, a method of performing interpolation by holding block data at the end of the reference frame in the horizontal direction or the vertical direction, a method of performing interpolation by a value set in a register, and the like can be considered. In addition, other methods may be used as long as the output video does not have a remarkably low image quality.

1 shows a schematic block diagram of an embodiment of the present invention. The data structure of a transport stream is shown. The example of a screen structure of a decoding object frame is shown. It is a flowchart of repair (interpolation) operation | movement of a block which cannot be decoded in a present Example. It is another flowchart of the repair (interpolation) operation | movement of a block which cannot be decoded in a present Example. The structural example of an access unit is shown. It is explanatory drawing of a structure by which the decoding object picture A uses two frame R0, R1 as a reference frame. It is explanatory drawing of the restoration operation | movement of a present Example. In this embodiment, it is an explanatory diagram of a repair operation when there is no corresponding block in the reference frame. It is explanatory drawing of the process which repairs (interpolates) the block which cannot be decoded in a prior art example. It is an explanatory example of the problem of a prior art example.

Explanation of symbols

10: Data input terminal 12: TS processing / camera information extraction device 13: Camera information memory 14: Entropy decoding device 15: Motion vector extraction device 16: Inverse quantization device 17: Motion vector memory 18: Inverse DCT device 20: Screen Inner prediction device 22: motion compensation device 24: weighted prediction device 26: selector 28: adder 30: selector 32: frame memory 34: output terminal 36: motion vector calculation device for interpolation processing 38: interpolation data generation device 50: transport Stream 52: PES (Packetized Elementary Stream) packet 54: PES packet payload 56: Video encoded data

Claims (8)

Video having decoding means for decoding encoded image data, replacement means for replacing image data in which an undecoding error has occurred with interpolation data, and a frame memory for sequentially storing output image data of the replacement means A decryption device comprising:
Reference frame information added to the encoded image data, storage means for storing motion vector information or camera information,
For the image data in which the undecoding error has occurred, reference frame information and motion vector information or camera information of a part that has been decoded within the same screen are extracted from the storage means, and a motion vector for interpolation processing and a representative reference frame are extracted. A determination means for determining
According to the motion vector for interpolation processing and the representative reference frame determined by the determining means, the interpolation data for the image data in which the undecoding error has occurred from the image data of the representative reference frame stored in the frame memory Interpolation data generation means for generating a video encoding device.   The determining means calculates the motion vector for interpolation processing from camera information when the picture type of the image data in which the undecoding error has occurred is I picture, and when the picture type is P picture or B picture, 2. The video decoding device according to claim 1, wherein the video decoding device is calculated from an average value or median value of motion vectors of reference frames, or camera information.   When the picture type of the image data in which the undecodable error has occurred is a P picture or a B picture, the determining means performs the interpolation processing motion when the ratio of the decoded block to the number of blocks of the picture is equal to or greater than a threshold value. A vector is calculated using an average value or a median value of the motion vectors, and the motion vector for interpolation processing is calculated from the camera information when the ratio of the decoded blocks is less than the threshold value. The video decoding device according to claim 1 or 2.   2. The video decoding apparatus according to claim 1, wherein, when there are a plurality of reference frames, the determination unit sets a frame referenced most by a decoded block as the representative reference frame. A video decoding method for interpolating data of a block in which an undecodable error has occurred with pictures at different times,
A decoding step of decoding the encoded image data;
A storage step of storing reference frame information added to the encoded image data, motion vector information or camera information;
Extracting motion vector information in a stream of decoded blocks in the same picture according to the picture type of the picture to be decoded;
Calculating a motion vector for interpolation processing from motion vector information in the stream;
And a step of interpolating data of a block in which an undecodable error has occurred using the motion vector for interpolation processing.   When the decoding target picture is an I picture, the motion vector for interpolation processing is calculated from camera information. When the picture to be decoded is a P picture or B picture, the average or median value of the motion vector information in the stream or camera information is used. 6. The video decoding method according to claim 5, wherein the video decoding method is calculated.   When the decoding target picture is a P picture or a B picture, when the ratio of decoded blocks to the number of blocks in the picture is equal to or greater than a threshold, the interpolation motion vector is the average value of the motion vectors in the stream or The video decoding according to claim 5 or 6, wherein the motion vector for interpolation processing is calculated from camera information when the median value is calculated and the ratio of the decoded blocks is less than the threshold value. Method.   6. The video decoding according to claim 5, further comprising means for selecting a reference picture, wherein when there are a plurality of reference pictures, a picture referenced most by a decoded block is used for error concealment processing. Device.

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