IMAGE ENCODING DEVICE, IMAGE DECODING DEVICE, IMAGE ENCODING METHOD, AND IMAGE DECODING METHOD

• US 20160021379A1
• Filed: 04/03/2013
• Published: 01/21/2016
• Est. Priority Date: 04/13/2012
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: MINEZAWA, Akira, SUGIMOTO, Kazuo, HIWASA, Norimichi, SEKIGUCHI, Shunichi
• Granted Patent: US 10,009,616 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/1887 the unit being a variable length codeword
• CPC Class Codes: H04N 19/463 by compressing encoding parameters before transmission
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding
• CPC Class Codes: H04N 19/96 Tree coding, e.g. quad-tree coding

Abstract

A variable length encoding unit 13 variable-length-encodes an index indicating a classification method of carrying out a class classification on each coding block having a largest size, the classification method being determined by a loop filter unit 11, and also variable-length-encodes a parameter about an offset value for each class determined for each coding block having the largest size on the basis of a binarization process using a truncated unary code.

Claims

1-13. -13. (canceled)

14. An image encoding device comprising:

a filter that carries out a filtering process on a local decoded image which is a result of addition of a difference image decoded from compressed data about an inputted image and a prediction image; and

a variable length encoder that variable-length-encodes said compressed data and a filter parameter used when the filtering process is carried out by said filter, and that generates a coded bitstream into which coded data about said compressed data and coded data about said filter parameter are multiplexed,

wherein said filter determines a classification method of carrying out a class classification on each coding block having a largest size, carries out a class classification on each pixel within each coding block having a largest size by using said classification method, calculates an offset value for each class for each coding block having the largest size, and carries out a pixel adaptive offset process of adding said offset value to a pixel value of a pixel belonging to a corresponding class, and said variable length encoder variable-length-encodes an index indicating the classification method of carrying out a class classification on each coding block having the largest size, the classification method being determined by said filter, and also variable-length-encodes a parameter about the offset value for each class determined for each coding block having the largest size on a basis of a binarization process using a truncated unary code.

15. The image encoding device according to claim 14, wherein a maximum of said offset value is determined by a bit depth of said decoded image.

16. The image encoding device according to claim 15, wherein said image encoding device includes:

a slice partitioner that partitions an inputted image into slices which are a plurality of part images;

a coding parameter determinator that determines the largest size of a coding block which is a unit to be processed at a time when an encoding process is carried out and also determines an upper limit on a number of hierarchies at a time when a coding block having the largest size is partitioned hierarchically, and that assigns a coding mode to each of coding blocks which are partitioned hierarchically;

a block partitioner that partitions a slice which is partitioned by said slice partitioner into coding blocks each having the largest size determined by said coding parameter determinator, and that partitions each of said coding blocks hierarchically into blocks until its number of hierarchies reaches the upper limit on the number of hierarchies which is determined by said coding parameter determinator;

a predictor that carries out a prediction process according to the coding mode assigned by said coding parameter determinator on each of the coding blocks which are partitioned by said block partitioner so as to generate a prediction image;

a difference image generator that generates a difference image between each of the coding blocks which are partitioned by said block partitioner and the prediction image generated by said predictor;

an image compressor that carries out a transformation process on the difference image generated by said difference image generator and quantizes transform coefficients of said difference image, and that outputs the transform coefficients quantized thereby as compressed data; and

a local decoded image generator that decodes the difference image from the compressed data outputted from said image compressor, and adds the difference image decoded and the prediction image generated by said predictor so as to generate a local decoded image, wherein said variable length encoder variable-length-encodes header information of each slice including information about the partitioning into the slices by said slice partitioner, the compressed data outputted from said image compressor, the coding mode assigned by said coding parameter determinator, a quantization matrix parameter for generating a quantization matrix used when the transform coefficients are quantized by said image compressor, and the filter parameter used when the filtering process is carried out by said filter so as to generate a coded bitstream into which coded data about said header information, the coded data about said compressed data, coded data about said coding mode, coded data about said quantization matrix parameter, and the coded data about said filter parameter are multiplexed.

17. The image encoding device according to claim 16, wherein when an intra coding mode is assigned, as the coding mode corresponding to a coding block partitioned by the block partitioner, by the coding parameter determinator, the predictor carries out an intra-frame prediction process corresponding to said intra coding mode on each prediction block which is a unit for prediction process at a time of carrying out the prediction process on said coding block so as to generate a prediction image.

18. The image encoding device according to claim 17, wherein when an inter coding mode is assigned, as the coding mode corresponding to a coding block partitioned by the block partitioner, by the coding parameter determinator, the predictor carries out a motion-compensated prediction process on each prediction block which is a unit for prediction process at a time of carrying out the prediction process on said coding block by using a reference image so as to generate a prediction image.

19. The image encoding device according to claim 18, wherein the coding parameter determinator determines both a quantization parameter used when the difference image is compressed and a transformation block partitioning state for each of the coding blocks, and also determines an intra prediction parameter or an inter prediction parameter used when the prediction process is carried out for each prediction block of said coding block, the predictor carries out an intra-frame prediction process by using said intra prediction parameter when an intra coding mode is assigned by said coding parameter determinator and carries out a motion-compensated prediction process by using said inter prediction parameter when an inter coding mode is assigned by said coding parameter determinator, the image compressor carries out the transformation process on the difference image generated by the difference image generator for each transformation block determined by said coding parameter determinator, and also quantizes the transform coefficients of said difference image by using the quantization parameter and the quantization matrix parameter which are determined by said coding parameter determinator and outputs the transform coefficients quantized thereby as the compressed data about said difference image, and, when variable-length-encoding said compressed data, the coding mode, said quantization matrix parameter, the filter parameter, and the header information of each slice, the variable length encoder variable-length-encodes the intra prediction parameter or the inter prediction parameter, which is determined by said coding parameter determinator, and transformation block partitioning information so as to generate the coded bitstream into which the coded data about said compressed data, the coded data about said coding mode, the coded data about said quantization matrix parameter, the coded data about said filter parameter, the coded data about said header information, coded data about said intra prediction parameter or said inter prediction parameter, and coded data about said transformation block partitioning information are multiplexed.

20. An image decoding device comprising:

a variable length decoder that variable-length-decodes compressed data and a filter parameter from coded data multiplexed into a coded bitstream; and

a filter that carries out a filtering process on a decoded image decoded from the compressed data variable-length-decoded by said variable length decoder by using the filter parameter variable-length-decoded by said variable length decoder,

wherein said variable length decoder variable-length-decodes, as a filter parameter, an index indicating a classification method of carrying out a class classification on each coding block having a largest size from the coded data multiplexed into said coded bitstream, and also variable-length-decodes a parameter about an offset value for each class for each coding block having the largest size on a basis of a binarization process using a truncated unary code, and said filter specifies the classification method of carrying out a class classification on each coding block having the largest size by using the index indicating the classification method of carrying out a class classification on each coding block having the largest size, carries out a class classification on each pixel by using the classification method of carrying out a class classification, the classification method specified for each coding block having said largest size, calculates an offset value from the parameter about the offset value for each class for each coding block having the largest size, and carries out a pixel adaptive offset process of adding said offset value to a pixel value of a pixel belonging to a corresponding class.

21. The image decoding device according to claim 20, wherein a maximum of said offset value is determined by a bit depth of said decoded image.

22. The image decoding device according to claim 21, wherein said image decoding device includes:

a variable length decoder that variable-length-decodes header information about each slice, a quantization matrix parameter, and a filter parameter from the coded data multiplexed into the coded bitstream, and that variable-length-decodes compressed data and a coding mode associated with each of coding blocks which are hierarchically partitioned from said coded data;

a predictor that carries out a prediction process according to the coding mode variable-length-decoded by said variable length decoder and associated with the coding block so as to generate a prediction image;

a difference image generator that inverse-quantizes transform coefficients which are compressed data variable-length-decoded by said variable length decoder and associated with the coding block by using a quantization parameter and said quantization matrix parameter which are variable-length-decoded by said variable length decoder, and that inverse-transforms the transform coefficients inverse-quantized thereby so as to generate a difference image before compression; and

a decoded image generator that adds the difference image generated by said difference image generator and the prediction image generated by said predictor so as to generate a decoded image.

23. The image decoding device according to claim 22, wherein when the coding mode variable-length-decoded by the variable length decoder and associated with the coding block is an intra coding mode, the predictor carries out an intra-frame prediction process corresponding to said intra coding mode on each prediction block which is a unit for prediction process at a time of carrying out the prediction process on said coding block so as to generate a prediction image.

24. The image decoding device according to claim 23, wherein when the coding mode variable-length-decoded by the variable length decoder and associated with the coding block is an inter coding mode, the predictor carries out a motion-compensated prediction process on each prediction block which is a unit for prediction process at a time of carrying out the prediction process on the coding block by using a reference image so as to generate a prediction image.

25. The image decoding device according to claim 24, wherein when variable-length-decoding the compressed data, the coding mode, and an adaptation parameter set from the coded data multiplexed into the coded bitstream, the variable length decoder variable-length-decodes an intra prediction parameter or an inter prediction parameter, and transformation block partitioning information, when the coding mode variable-length-decoded by said variable length decoder and associated with the coding block is an intra coding mode, the predictor carries out the intra-frame prediction process by using said intra prediction parameter, and, when the coding mode variable-length-decoded by said variable length decoder and associated with the coding block is an inter coding mode, carries out the motion-compensated prediction process by using said inter prediction parameter, and the difference image generator inverse-transforms the transform coefficients inverse-quantized thereby for each of transformation blocks acquired from the transformation block partitioning information variable-length-decoded by said variable length decoder so as to generate a difference image before compression.

26. An image encoding method comprising:

a filtering process step of a filter carrying out a filtering process on a local decoded image which is a result of addition of a difference image decoded from compressed data about an inputted image and a prediction image; and

a variable length encoding process step of a variable length encoder variable-length-encoding said compressed data and a filter parameter used when the filtering process is carried out in said filtering process step, and generating a coded bitstream into which coded data about said compressed data and coded data about said filter parameter are multiplexed,

wherein said filtering process step includes the steps of determining a classification method of carrying out a class classification on each coding block having a largest size, carrying out a class classification on each pixel within each coding block having the largest size by using said classification method, calculating an offset value for each class, and carrying out a pixel adaptive offset process of adding said offset value to a pixel value of a pixel belonging to a corresponding class, and said variable length encoding process step includes the steps of variable-length-encoding an index indicating the classification method of carrying out a class classification on each coding block having the largest size, the classification method being determined in said filtering process step, and also variable-length-encoding a parameter about the offset value for each class determined for each coding block having the largest size on a basis of a binarization process using a truncated unary code.

27. An image encoding method comprising:

a filtering process step of a filter carrying out a filtering process on a local decoded image which is a result of addition of a difference image decoded from compressed data about an inputted image and a prediction image; and

a variable length encoding process step of a variable length encoder variable-length-encoding said compressed data and a filter parameter used when the filtering process is carried out in said filtering process step, and generating a coded bitstream into which coded data about said compressed data and coded data about said filter parameter are multiplexed,

wherein said filtering process step includes the steps of determining a classification method of carrying out a class classification on each coding block having a largest size, carrying out a class classification on each pixel within each coding block having the largest size by using said classification method, determining a parameter for calculating an offset value for each class and also calculating an offset value for each class from said parameter, and carrying out a pixel adaptive offset process of adding said offset value to a pixel value of a pixel belonging to a corresponding class, and said variable length encoding process step includes the steps of variable-length-encoding an index indicating the classification method of carrying out a class classification on each coding block having the largest size, the classification method being determined by said filtering process step, and also variable-length-encoding a parameter about the offset value for each class determined for each coding block having the largest size on a basis of a binarization process using a truncated unary code.

28. An image decoding method comprising:

a variable length decoding process step of a variable length decoder variable-length-decoding compressed data and a filter parameter from coded data multiplexed into a coded bitstream;

a filtering process step of a filter carrying out a filtering process on a decoded image decoded from the compressed data variable-length-decoded in said variable length decoding process step by using the filter parameter variable-length-decoded in said variable length decoding process step,

wherein said variable length decoding process step includes the steps of variable-length-decoding, as a filter parameter, an index indicating a classification method of carrying out a class classification on each coding block having a largest size from the coded data multiplexed into said coded bitstream, and also variable-length-decoding a parameter about an offset value for each class for each coding block having the largest size on a basis of a binarization process using a truncated unary code, and said filtering process step includes the steps of specifying the classification method of carrying out a class classification on each coding block having the largest size by using the index indicating the classification method of carrying out a class classification on each coding block having the largest size, carrying out a class classification on each pixel by using the classification method of carrying out a class classification, the classification method specified for each coding block having said largest size, calculating an offset value from the parameter for calculating the offset value for each class for each coding block having the largest size, and carrying out a pixel adaptive offset process of adding said offset value to a pixel value of a pixel belonging to a corresponding class.