WO2011071316A2 - Appareil et procédé d'encodage d'image, appareil et procédé d'encodage par transformée, appareil et procédé pour générer une base de transformée, et appareil et procédé de décodage d'image associés - Google Patents

Appareil et procédé d'encodage d'image, appareil et procédé d'encodage par transformée, appareil et procédé pour générer une base de transformée, et appareil et procédé de décodage d'image associés Download PDF

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WO2011071316A2
WO2011071316A2 PCT/KR2010/008777 KR2010008777W WO2011071316A2 WO 2011071316 A2 WO2011071316 A2 WO 2011071316A2 KR 2010008777 W KR2010008777 W KR 2010008777W WO 2011071316 A2 WO2011071316 A2 WO 2011071316A2
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intra prediction
prediction error
prediction mode
unit
intra
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WO2011071316A3 (fr
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김수년
임정연
이규민
최재훈
김용구
최윤식
최영호
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에스케이텔레콤 주식회사
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Priority to US13/514,552 priority Critical patent/US9271000B2/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/11—Selection of coding mode or of prediction mode among a plurality of spatial predictive coding modes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/12—Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264
    • H04N19/122—Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/593—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial prediction techniques
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
    • H04N19/61—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding in combination with predictive coding

Definitions

  • Embodiments of the present invention relate to an image encoding apparatus and method, a transform encoding apparatus and method used therein, a converter generating apparatus and method, and an image decoding apparatus and method. More specifically, by transform-coding the intra prediction error by adaptively generating the transformer according to the characteristic change of the image as well as the intra prediction mode for the specific coding unit, the performance of the intra prediction coding is greatly increased without adding any additional information.
  • a video encoding apparatus and method which can be improved, a transform encoding apparatus and method used therein, a converter generating apparatus and method, and a video decoding apparatus and method.
  • the basic principle of compressing data is to eliminate redundancy in the data. Spatial overlap, such as the same color or object repeating in an image, temporal overlap, such as when there is almost no change in adjacent frames in a movie frame, or the same note over and over in audio, or high frequency of human vision and perception Data can be compressed by removing the psychological duplication taking into account the insensitive to.
  • H.264 is a digital video codec standard with a very high data compression ratio, also called MPEG-4 Part 10 or Advanced Video Coding (AVC).
  • AVC Advanced Video Coding
  • This standard is based on the Video Coding Experts Group (VCEG) of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and the International Standardization Organization / International Electrotechnical Commission (ISO / IEC). This is the result of MPEG jointly forming and standardizing a Joint Video Team.
  • VCEG Video Coding Experts Group
  • ITU-T International Telecommunication Union Telecommunication Standardization Sector
  • ISO / IEC International Electrotechnical Commission
  • the temporal prediction is performed by referring to a reference block 122 of another temporal frame 120 that is adjacent in time when predicting the current block 112 of the current frame 110. to be. That is, in inter-prediction of the current block 112 of the current frame 110, the adjacent reference frame 120 is searched for in time, and the reference block (the most similar to the current block 112 in the reference frame 120) 122).
  • the reference block 122 is a block that can best predict the current block 112, and the block having the smallest sum of absolute difference (SAD) with the current block 112 may be the reference block 122.
  • the reference block 122 becomes a prediction block of the current block 112, and generates a residual block by subtracting the reference block 122 from the current block 112.
  • the generated residual block is encoded and inserted into the bitstream.
  • the relative difference between the position of the current block 112 in the current frame 110 and the position of the reference block 122 in the reference frame 120 is called a motion vector 130, and the motion vector 130 is also a residual block.
  • Temporal prediction is also referred to as inter prediction or inter prediction.
  • Spatial prediction is to obtain the prediction pixel value of the target block by using the reconstructed pixel value of the reference block adjacent to the target block in one frame, and directional intra-prediction (hereinafter referred to simply as intra prediction) It is also called intra prediction.
  • intra prediction directional intra-prediction
  • H.264 specifies encoding / decoding using intra prediction.
  • Intra prediction is a method of predicting values of a current subblock by copying in a predetermined direction by using adjacent pixels in up and left directions for one sub-block, and encoding only the difference.
  • the prediction block for the current block is generated based on another block having the previous coding order.
  • a value obtained by subtracting the current block and the prediction block is coded.
  • the video encoder according to H.264 selects, for each block, a prediction mode in which the difference between the current block and the prediction block is minimal among the prediction modes.
  • Intra prediction according to the H.264 standard is illustrated in FIG. 2 in consideration of the position of adjacent pixels and the direction of the prediction used to generate predicted pixel values of 4 x 4 luma blocks and 8 x 8 luma blocks.
  • Nine prediction modes as defined. The nine prediction modes are vertical prediction mode (prediction mode 0), horizontal prediction mode (prediction mode 1), DC prediction mode (prediction mode 2), Diagonal_Down_Left prediction mode (prediction mode 3), Diagontal_Down_Right prediction mode (depending on the prediction direction).
  • Prediction mode 4 Vertical_Right prediction mode (prediction mode 5), Horizontal_Down prediction mode (prediction mode 6), Vertical_Left prediction mode (prediction mode 7), and Horizontal_Up prediction mode (prediction mode 8).
  • the DC prediction mode uses an average value of eight adjacent pixels.
  • prediction mode 3 is that.
  • the same four prediction modes are also used for intra prediction processing on 8 x 8 chroma blocks.
  • FIG. 3 shows an example of labeling for explaining the nine prediction modes of FIG. 2.
  • a prediction block (region including a to p) for the current block is generated using the samples A to M that are decoded in advance. If E, F, G, and H cannot be decoded in advance, E, F, G, and H can be virtually generated by copying D to their positions.
  • FIG. 4 is a diagram for describing nine prediction modes of FIG. 2 using FIG. 3.
  • the prediction block predicts the pixel value with the same pixel value for each vertical line. That is, the pixels of the prediction block predict the pixel value from the nearest pixels of the reference block located above the prediction block, and the reconstructed pixel values of the adjacent pixel A are converted into the first column pixels a, pixel e, pixel i and Set to the predicted pixel value for pixel m.
  • second column pixel b, pixel f, pixel j and pixel n are predicted from the reconstructed pixel values of adjacent pixel B
  • third column pixel c, pixel g, pixel k and pixel o are Predicted from the reconstructed pixel values
  • fourth column pixel d, pixel h, pixel l and pixel p predicts from the reconstructed pixel values of adjacent pixel D.
  • a prediction block is generated in which the prediction pixel values of each column are the pixel values of pixel A, pixel B, pixel C and pixel D.
  • the prediction block predicts the pixel value with the same pixel value for each horizontal line. That is, the pixels of the prediction block predict the pixel value from the nearest pixels of the reference block located to the left of the prediction block, and the reconstructed pixel value of the adjacent pixel I is determined by the first row of pixels a, pixel b, pixel c and Set to the predicted pixel value for pixel d.
  • the second row pixels e, pixel f, pixel g and pixel h are predicted from the reconstructed pixel values of adjacent pixel J
  • the third row pixel i, pixel j, pixel k and pixel l are Predicted from the reconstructed pixel values
  • the fourth row pixel m, pixel n, pixel o and pixel p predicts from the reconstructed pixel values of adjacent pixel D.
  • a prediction block is generated in which the prediction pixel values of each row are the pixel values of pixel I, pixel J, pixel K, and pixel L.
  • the pixels of the prediction block are equally replaced by the average of the pixel values of the upper pixels A, B, C and D and the left pixels I, J, K and L.
  • the pixels of the prediction block in the prediction mode 3 are interpolated in the lower left direction at a 45 ° angle between the lower-left and the upper-right, and the prediction in the prediction mode 4
  • the pixels of the block are extrapolated in the lower right direction at a 45 ° angle.
  • the pixels of the prediction block in the prediction mode 6 are extrapolated in the lower right direction at an angle of about 26.6 ° horizontally, and the pixels of the prediction block in the prediction mode 7 are in the lower left direction at about 26.6 ° angle from the vertical Extrapolated, the pixels of the predictive block in the case of the prediction mode 8 are interpolated in an upward direction of about 26.6 degrees from the horizontal.
  • the pixels of the prediction block may be generated from a weighted average of pixels A to M of the reference block to be decoded in advance.
  • the pixel d located at the top right of the prediction block may be estimated as in Equation 1.
  • round () is a function that rounds to integer places.
  • the 16 ⁇ 16 prediction model for the luminance component includes four modes of prediction mode 0, prediction mode 1, prediction mode 2, and prediction mode 3.
  • prediction mode 1 the pixels of the prediction block are extrapolated from the upper pixels, and in prediction mode 1, the pixels are extrapolated from the left pixels.
  • prediction mode 2 the pixels of the prediction block are calculated as an average of upper pixels and left pixels.
  • prediction mode 3 a linear "plane" function is used that fits the upper and left pixels. This mode is more suitable for areas where the luminance changes smoothly.
  • the pixel value of the prediction block is generated according to the direction corresponding to each mode based on the adjacent pixels of the prediction block to be currently encoded.
  • the prediction error between the prediction value predicted by each prediction mode and the current pixel value is transform-coded using a discrete cosine transform (DCT) based integer transform method, which is 4x4 and 16x16 intra prediction modes according to the block size.
  • DCT discrete cosine transform
  • an integer transformation of 4x4 unit is applied, and when using an 8x8 intra prediction mode, an integer transformation of 8x8 unit is applied.
  • ITU-T's Video Coding Expert Group has evolved to further improve the performance of intra prediction coding, including Shiodera Taichiro, Akiyuki Tanizawa, Takeshi Chujoh, and tomoo Yamakage (“Improvement of Bidirectional Intra Prediction”, ITU-T SG16 / Q.6 Doc.VCEG-AG08, Oct. 2007) further diversifies the orientation of pixel values used for intra prediction to increase the number of intra prediction modes, and introduces intra prediction techniques by weighted sum of the two intra prediction modes. Improved the performance of the encoding.
  • this technique has the disadvantage that as the number of intra prediction modes to be considered is increased by four times, the amount of computation for finding the optimal mode is greatly increased, and the amount of additional information for encoding the same is increased.
  • an embodiment of the present invention is to effectively remove spatial redundancy remaining in the prediction error to obtain a higher energy concentration effect, and to more efficiently transform-code the prediction error after intra prediction.
  • An object of the present invention is to provide a transform encoding apparatus and method, a converter generating apparatus and method, and a video decoding apparatus and method used therein.
  • an image encoding apparatus includes an intra prediction error that aggregates prediction errors of blocks having the same intra prediction mode among macroblocks of a predetermined unit encoded before a current macroblock. Confluence; A converter generator generating unit for generating a converter for each intra prediction mode based on the prediction error collected by the intra prediction error collector; An intra predictor for predicting a pixel value of a current pixel using neighboring pixels of a target block in a current frame according to a directional intra prediction mode, and generating a prediction error based on a difference from the current pixel; And a transform encoding unit for transform encoding the prediction error generated by the intra prediction unit by using the transformer generated by the transformer generation unit.
  • the transformer bottom generator includes a correlation matrix calculator that calculates an autocorrelation matrix for a set of prediction errors collected by the intra prediction error collector.
  • the transducer generation generator generates a Karhunen-Loeve Transform (KLT) based transducer based on the autocorrelation matrix calculated by the correlation matrix calculator.
  • KLT Karhunen-Loeve Transform
  • the transformer bottom generation unit may further include a correlation matrix calculation unit that calculates an autocorrelation matrix for a set of prediction errors collected by the intra prediction error aggregation unit; And an eigenvector calculator for calculating an eigenvector from the autocorrelation matrix calculated by the correlation matrix calculator.
  • the transform encoder preferably transform-codes the prediction error generated by the intra predictor using the calculated eigenvectors.
  • the transform encoding apparatus in the transform encoding apparatus for transforming and encoding the prediction error generated by the difference between the pixel predicted by the intra prediction apparatus and the current pixel, An intra prediction error aggregation unit that aggregates prediction errors of blocks having the same intra prediction mode among macroblocks encoded in a predetermined unit before the current macroblock; And a converter bottom generator for generating a converter for each intra prediction mode based on the prediction error collected by the intra prediction error collector.
  • the transform encoding apparatus preferably transform-codes the prediction error generated by the intra prediction apparatus by using the transformer generated by the transformer generation unit.
  • the intra prediction error aggregation unit aggregates the prediction errors into a set as in the following equation,
  • Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock Indicates the number of blocks determined as Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock.
  • the transform encoding apparatus may further include a correlation matrix calculation unit configured to calculate an autocorrelation matrix for a set of prediction errors collected by the intra prediction error aggregation unit based on the following equation.
  • the transducer generation generator generates the transducer using the calculated autocorrelation matrix.
  • Intra prediction mode Represents a 4x4 autocorrelation matrix for a column vector signal of 4x4 intra prediction error determined as Has a value from 0 to 8 as an index pointing to the number of 4x4 intra prediction modes, Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock. Indicates the number of blocks determined as Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock. Represents a set of 4x4 prediction error blocks of the blocks determined as of The fourth element represents one 4x4 prediction error block.
  • the transform encoding apparatus may further include a correlation matrix calculation unit configured to calculate an autocorrelation matrix for a set of prediction errors collected by the intra prediction error aggregation unit based on the following equation.
  • the transducer generation generator generates the transducer using the calculated autocorrelation matrix.
  • Intra prediction mode Represents a 4x4 autocorrelation matrix for a row vector signal of 4x4 intra prediction error determined as Has a value from 0 to 8 as an index pointing to the number of 4x4 intra prediction modes, Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock. Indicates the number of blocks determined as Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock. Represents a set of 4x4 prediction error blocks of the blocks determined as of The fourth element represents one 4x4 prediction error block.
  • a converter generator generating apparatus includes a converter block generating apparatus for generating a converter for an intra prediction mode, wherein macroblocks of a predetermined unit encoded before a current macroblock are encoded.
  • An intra prediction error aggregation unit that aggregates prediction errors of blocks having the same intra prediction mode among them;
  • a correlation matrix calculator for calculating an autocorrelation matrix for a set of prediction errors collected by an intra prediction error collector;
  • an eigenvector calculator for calculating an eigenvector from the autocorrelation matrix calculated by the correlation matrix calculator.
  • the converter generation device generates a converter for each intra prediction mode based on the eigenvectors calculated by the eigenvector calculator.
  • the transducer generation apparatus generates a KLT based transducer based on the autocorrelation matrix and the eigenvector.
  • an intra prediction apparatus predicts pixel values of a current pixel using neighboring pixels of a target block in a current frame according to a directional intra prediction mode.
  • An intra predictor which generates a prediction error through a difference of?
  • an intra prediction error aggregation unit that aggregates prediction errors of blocks having the same intra prediction mode among macroblocks encoded in a predetermined unit before the current macroblock.
  • the intra prediction apparatus may predict the prediction error for the macroblocks of a predetermined unit encoded before the current macroblock aggregated by the intra prediction error aggregation unit together with the prediction error for the current frame generated by the intra prediction unit. It is preferable to output.
  • an image decoding apparatus includes an intra prediction error that aggregates prediction errors of blocks having the same intra prediction mode among macroblocks of a predetermined unit decoded before the current macroblock.
  • Confluence A converter generator generating unit for generating a converter for each intra prediction mode based on the prediction error collected by the intra prediction error collector;
  • An intra prediction mode reading unit which reads an intra prediction mode of a target block to be decoded with respect to an input bitstream;
  • An inverse transformer for inversely transforming a prediction error for a target block by using a transformer corresponding to the intra prediction mode read by the intra prediction mode reading unit among the transformers generated by the transformer bottom generating unit; And predict the pixel value of the current pixel using the neighboring pixels of the target block in the current frame according to the intra prediction mode read by the intra prediction mode reading unit, and add a prediction error value inversely transformed by the inverse transform unit to add the current block.
  • It comprises a current block recovery unit for restoring the
  • the transformer bottom generation unit may include a correlation matrix calculation unit that calculates an autocorrelation matrix for aggregation of prediction errors aggregated by an intra prediction error aggregation unit; And an eigenvector calculator for calculating an eigenvector from the autocorrelation matrix calculated by the correlation matrix calculator. It is preferable to generate a KLT-based converter based on the autocorrelation matrix and the eigenvector.
  • an image encoding method aggregates prediction errors of blocks having the same intra prediction mode among macroblocks of a predetermined unit encoded before a current macroblock, and collects a current frame. Predicting the value of the current pixel using the neighboring pixels of the target block according to the directional intra prediction mode for and generating a prediction error through a difference between the predicted value and the value of the current pixel; Generating a transducer for each intra prediction mode based on the prediction error aggregated by the prediction error aggregation step; And transcoding the prediction error generated for the current frame using the converter generated by the converter generation step.
  • a transform encoding method is a transform encoding method for transforming and encoding a prediction error generated by a difference between a pixel predicted by an intra prediction apparatus and a current pixel. Aggregating prediction errors of blocks having the same intra prediction mode among macroblocks encoded in a predetermined unit before the macroblock; And generating a transducer for each intra prediction mode based on the prediction error aggregated by the prediction error aggregation step.
  • the transform encoding method preferably transform-codes the prediction error generated by the intra prediction apparatus by using the transformer generated by the transformer generation step.
  • the transform encoding method may further include calculating an autocorrelation matrix for a set of prediction errors aggregated by the prediction error aggregation step. In this case, it is preferable to generate the transducer bottom using the calculated autocorrelation matrix.
  • an image decoding method comprises the steps of: aggregating prediction errors of blocks having the same intra prediction mode among macroblocks of a predetermined unit decoded before the current macroblock; Generating a transformer for each intra prediction mode based on the prediction error aggregated by the intra prediction error step; Reading an intra prediction mode of a target block to be decoded with respect to an input bitstream; Inversely converting a prediction error for a target block by using a converter corresponding to the intra prediction mode read out by the intra prediction mode reading unit among the converters generated by the converter generation step; And predict the pixel value of the current pixel using the neighboring pixels of the target block in the current frame according to the intra prediction mode read by the intra prediction mode reading step, and add the prediction error value inversely transformed by the inverse transform step to add the current block. It characterized in that it comprises a step of restoring.
  • the transformer generation step may include calculating an autocorrelation matrix for aggregation of prediction errors aggregated by an intra prediction error aggregation step; And calculating an eigenvector from the autocorrelation matrix calculated by the correlation matrix calculation step.
  • transform information is encoded by adding an additional prediction information.
  • the performance of the intra prediction encoding is greatly improved, thereby greatly improving the compression efficiency of the video compression apparatus or the quality of the reconstructed image.
  • 1 is a diagram illustrating a general inter prediction.
  • FIG. 2 is a diagram illustrating directionality of the intra prediction mode.
  • FIG. 3 is a diagram illustrating an example of labeling for explaining an intra prediction mode of FIG. 2.
  • FIG. 4 is a diagram illustrating each of the intra prediction modes of FIG. 2.
  • FIG. 5A is a diagram illustrating the prediction mode 0 of the intra prediction modes of FIG. 2
  • FIG. 5B is a diagram illustrating the prediction mode 1 of the intra prediction modes of FIG. 2. to be.
  • FIG. 6 is a diagram schematically illustrating an image encoding apparatus according to an embodiment of the present invention.
  • FIG. 7 is a flowchart illustrating an image encoding method by the image encoding apparatus of FIG. 6.
  • FIG. 8 is a flowchart illustrating a transform encoding method according to another embodiment of the present invention.
  • FIG. 9 is a diagram illustrating an example of a structure of a bitstream generated by the video encoding apparatus of FIG. 6.
  • FIG. 10 is a diagram schematically illustrating an image decoding apparatus according to an embodiment of the present invention.
  • FIG. 11 is a flowchart illustrating an image decoding method by the image decoding apparatus of FIG. 10.
  • the image encoding apparatus 600 includes an intra prediction error converging unit 610, a transformer generator 620, an intra predictor 630, and a transform encoder 640.
  • the intra prediction error converging unit 610, the converter low generator 620, and the transform encoder 640 may also be referred to as a transform encoder.
  • the intra prediction error aggregation unit 610 aggregates prediction errors of blocks having the same intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock. That is, the intra prediction error aggregation unit 610 receives macroblocks encoded before a current macroblock in order to generate a transform basis for various intra prediction modes, and then selects the same intra prediction mode among the blocks for which the intra prediction mode is determined. Aggregate the prediction errors of blocks with In this case, since 9 types of intra prediction modes are defined in 4x4 intra mode and 8x8 intra mode, 9 types of 4x4 intra prediction error and 8x8 intra prediction error may be aggregated. In addition, since the 16x16 intra prediction mode is defined as four types of intra prediction modes, 16x16 intra prediction errors may be aggregated into four types. For example, the intra prediction errors for the 4x4 intra prediction mode may be aggregated into a set such as Equation 2.
  • the number of blocks determined as follows.
  • the converter generation unit 620 generates a converter for each intra prediction mode based on the size of the intra prediction block and the prediction error aggregated by the intra prediction error aggregation unit 610 according to the intra prediction mode.
  • the converter bottom is preferably generated based on the Karhunen-Loeve Transform (KLT), which is known to have the best energy concentration efficiency.
  • KLT Karhunen-Loeve Transform
  • the converter generation unit 620 may be implemented as an independent component, or may be configured to include a correlation matrix calculator 622 and an eigenvector calculator 624 as shown.
  • an intra prediction error converging unit 610, a correlation matrix calculating unit 622, and an eigenvector calculating unit 624 may be included to form a transformer generator.
  • the correlation matrix calculation unit 622 calculates an autocorrelation matrix for a set of prediction errors aggregated by the intra prediction error aggregation unit 610.
  • the intra prediction error block in Equation 2 Since is a two-dimensional signal, we need to create two transformation bases for the column vector signal and the row vector signal.
  • an autocorrelation matrix of intra prediction error In order to generate the KLT basis, an autocorrelation matrix of intra prediction error must be obtained, which can be obtained as in Equation 3 and Equation 4.
  • Intra prediction mode Represents a 4x4 autocorrelation matrix for a column vector signal of 4x4 intra prediction error determined as Is an index indicating the number of 4x4 intra prediction modes and has a value of 0 to 8. Also, Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock. Indicates the number of blocks determined as Is an intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock. Represents a set of 4x4 prediction error blocks of the blocks determined as of The fourth element represents one 4x4 prediction error block. Also, in Equation 4 Intra prediction mode It represents a 4x4 autocorrelation matrix for the row vector signal of the 4x4 intra prediction error determined by.
  • the KLT basis for the 4x4 intra prediction error block can be obtained by using an eigenvector of an autocorrelation matrix.
  • the eigenvector calculator 624 calculates Equation 3 and equations calculated by the correlation matrix calculator 622. From the autocorrelation matrix such as 4, an eigenvector can be calculated as shown in Equations 5 and 6.
  • Equation (5) Is Means the eigenvector of Is Eigenvalue. Also, in Equation 6, Is Means the eigenvector of Is Eigenvalue. The eigenvectors satisfying the equations (5) and (6) are obtained and expressed as matrices, as in Equations 7 and 8.
  • Intra prediction mode KLT basis for the column vector signal of the prediction error block corresponding to Intra prediction mode The KLT basis for the row vector signal of the prediction error block corresponding to.
  • the intra predictor 630 predicts pixel values of the prediction block by using neighboring pixels of the target block in the current frame according to the directional intra prediction mode. In addition, the intra predictor 630 generates a prediction error through a difference between the pixel value of the target block and the pixel value of the prediction block. That is, the intra predictor 630 includes a difference unit (not shown) that calculates a difference between the target block and the prediction block.
  • the transform encoder 640 transform-codes the prediction error generated by the intra predictor 630 using the transformer generated by the transformer generator 620. Conversion of the two-dimensional signal using the above-described KLT basis is performed as in Equation (9).
  • Intra prediction mode Means a prediction error signal of silver Means the signal converted by KLT.
  • the method of generating the KLT basis for the intra prediction error of the 8x8 intra prediction mode is the same as that of the 4x4 intra prediction mode, and the KLT for the intra prediction error of the 16x16 intra prediction mode.
  • the basis generation method also reduces the number of intra prediction error sets and the number of KLT basis to four types, and the method is the same as that of the 4x4 intra prediction mode.
  • the KLT basis generated by the transformer generator 620 is not a transducer optimized for the prediction error generated by the intra predictor 630, there is a high correlation between the current frame and the previous frame due to the characteristics of a general video signal. Therefore, there is no big difference in performance with the translator optimized for the current frame and there is no need to transmit any additional information about the base for decoding by generating the translator among a predetermined number of macroblocks encoded before the current macroblock.
  • the intra prediction unit 630 is described as being configured independently of the intra prediction error aggregation unit 610, but the intra prediction unit 630 may be configured to include the intra prediction error aggregation unit 610. have. That is, the intra predictor 630 predicts pixel values of the prediction block by using the neighboring pixels of the target block in the current frame according to the directional intra prediction mode and generates a prediction error through a difference from the pixel values of the target block.
  • the intra prediction mode of the macroblocks of the predetermined unit encoded before the current macroblock may be implemented to aggregate the prediction errors of the blocks having the same intra prediction mode among the determined blocks and to output the prediction error with respect to the current frame. It may be.
  • FIG. 7 is a flowchart illustrating an image encoding method by the image encoding apparatus of FIG. 6.
  • the intra prediction error aggregation unit 610 aggregates the prediction errors of blocks having the same intra prediction mode among macroblocks of a predetermined unit encoded before the current macroblock (S701).
  • the prediction error for the macroblocks of a predetermined unit encoded before the current macroblocks aggregated as described above may be represented in the form of a set as in Equation 2.
  • the transformer generator 620 calculates an autocorrelation matrix for a set of intra prediction modes based on the prediction error aggregated by the intra prediction error aggregation unit 610 (S703). 4x4 intra prediction error block Since is a two-dimensional signal, the translator must generate two types of column vector signals and row vector signals.
  • the autocorrelation matrix may be calculated as shown in Equations 3 and 4 below.
  • the KLT basis may be calculated through the eigenvectors of the autocorrelation matrix as shown in Equations 5 and 6 (S705).
  • the calculated eigenvectors may be represented by matrices such as Equations 7 and 8.
  • the intra predictor 630 predicts a pixel value of the current pixel using neighboring pixels of the target block in the current frame according to the directional intra prediction mode, and estimates a prediction error through a difference between the predicted pixel and the current pixel. It generates (S707).
  • the transform encoder 640 transform-codes the prediction error generated by the intra predictor 630 as shown in Equation 9 by using the transformer generated by the transformer generator 620 (S709).
  • FIG. 8 is a flowchart illustrating a transform encoding method according to another embodiment of the present invention.
  • the intra predictor 630 is configured to be independent of the intra prediction error converging unit 610, the converter low generator 620, and the transform encoder 640, the intra predictive error converging unit 610 and the transform low
  • the generator 620 and the transform encoder 640 may be referred to as components of a transform encoding apparatus.
  • steps S801 to S805 of the transform encoding apparatus are performed in the same process as steps S701 to S705 of FIG. 7, and transforms the prediction error independently generated by the intra prediction unit 630 using the generated transformer.
  • Encode (S807) is performed in the same process as steps S701 to S705 of FIG. 7, and transforms the prediction error independently generated by the intra prediction unit 630 using the generated transformer.
  • bitstream 9 is a diagram illustrating an example of a structure of a bitstream generated by the video encoding apparatus of FIG. 6.
  • bitstreams are encoded in slice units.
  • the bitstream includes a slice header 910 and a slice date 920, and the slice data 920 includes a plurality of macroblock data (MBs) 921 to 924.
  • macroblock data 923 may be composed of an mb_type field 930, an mb_pred field 935, and a texture data field 939.
  • a value indicating the type of macroblock is recorded in the mb_type field 930. That is, it indicates whether the current macroblock is an intra macroblock or an inter macroblock.
  • a detailed prediction mode according to the type of the macroblock is recorded.
  • information of a prediction mode selected during intra prediction is recorded, and in case of an inter macroblock, information of a reference frame number and a motion vector is recorded for each macroblock partition.
  • the mb-pred field 935 is divided into a plurality of block information 941 to 944, and each block information 942 is a value of the main mode described above. It is divided into a main_mode field 945 for recording a sub-mode field 946 for recording a value of the above-described sub-mode.
  • the encoded residual image that is, the texture data
  • the texture data field 939 is recorded in the texture data field 939.
  • FIG. 10 is a diagram schematically illustrating an image decoding apparatus according to an embodiment of the present invention
  • FIG. 11 illustrates an image decoding method by the image decoding apparatus of FIG. 10.
  • the configuration and operation of the video decoding apparatus 600 will be described in detail with reference to the drawings.
  • the image decoding apparatus 1000 may include an intra prediction error converging unit 1010, a converter generation unit 1020, a prediction mode reading unit 1030, an inverse transform unit 1040, and a current block reconstruction unit 1050.
  • the transformer generator 1020 may include a correlation matrix calculator 1022 and an eigenvector calculator 1024.
  • the intra prediction error aggregation unit 910 aggregates prediction errors of blocks having the same intra prediction mode among predetermined macroblocks decoded before the current macroblock (S1101). That is, the intra prediction error converging unit 910, like the intra prediction error converging unit 610 of FIG. 6, processes a predetermined number of macroblocks decoded before the current macroblock to generate a transform basis for various intra prediction modes. Receives the prediction errors of the blocks having the same intra prediction mode among the blocks for which the intra prediction mode is determined. In this case, since 9 types of intra prediction modes are defined in 4x4 intra mode and 8x8 intra mode, 9 types of 4x4 intra prediction error and 8x8 intra prediction error may be aggregated. In addition, since the 16x16 intra prediction mode is defined as four types of intra prediction modes, 16x16 intra prediction errors may be aggregated into four types. For example, the intra prediction errors for the 4x4 intra prediction mode may be aggregated into a set such as Equation 2.
  • the converter generation unit 920 generates a converter for each intra prediction mode based on the prediction error aggregated by the intra prediction error aggregation unit 910.
  • the transducer may be generated based on KLT, which is known to have the best energy concentration efficiency in theory.
  • the converter generation unit 920 may be implemented as an independent component.
  • the converter generation unit may include an intra prediction error aggregation unit 910, a correlation matrix calculation unit 922, and an eigenvector calculation unit 924. It may be implemented as.
  • the correlation matrix calculation unit 922 calculates an autocorrelation matrix for a set of prediction errors aggregated by the intra prediction error aggregation unit 910 (S1103).
  • the intra prediction error block in Equation 2 Since is a two-dimensional signal, as in the case of the image encoding apparatus 600, two transformation bases for a column vector signal and a row vector signal must be generated.
  • an autocorrelation matrix of an intra prediction error in order to generate a KLT basis, an autocorrelation matrix of an intra prediction error must be obtained, which can be obtained as shown in Equations 3 and 4 below.
  • the KLT basis for the 4x4 intra prediction error block may be obtained through an eigenvector of an autocorrelation matrix.
  • the eigenvector calculator 924 may be calculated by Equation 3 calculated by the correlation matrix calculator 922 and From the autocorrelation matrix as shown in Equation 4, an eigenvector can be calculated as shown in Equations 5 and 6 (S1105).
  • the converter generation unit 1020 may obtain a eigenvector satisfying Equation 5 and Equation 6, and may generate a KLT-based converter low by expressing it as a matrix such as Equation 7 and Equation 8 (S1107). ).
  • the prediction mode reading unit 1030 reads the intra prediction mode of the target block to be decoded from the bitstream structure as shown in FIG. 9 (S1109). That is, the prediction mode reading unit 1030 receives the bitstream generated by the image encoding apparatus 600 and reads the intra prediction mode of the target block to be decoded of the current frame.
  • the inverse converter 1040 is received through the bitstream using a converter corresponding to the intra prediction mode read by the intra prediction mode reader 1030 of the converter generated by the converter generator 1020.
  • the prediction error is inversely transformed (S1111).
  • the intra prediction mode reader 1030 determines the intra prediction mode of the target block to be decoded of the current frame from the input bitstream, and the inverse transformer 1040 reads the intra prediction mode reader 1030.
  • An inverse transform is performed on the prediction error by applying a transformer corresponding to the intra prediction mode.
  • the inverse transformation of the 2D signal using the above-described KLT-based converter may be performed as shown in Equation 10.
  • Intra prediction mode Means that the prediction error of the transform-coded signal
  • KLT Means the inverted signal.
  • the inverse matrix of the KLT basis should be used for the inverse transformation, but since the KLT basis is an orthogonal matrix made of eigenvectors, the inverse matrix and the transpose matrix are the same. Therefore, the above-described inverse transformation of the 2D signal may be performed as shown in Equation 11 using the transpose matrix more simply without obtaining an inverse matrix.
  • the current block reconstruction unit 1050 estimates the pixel value of the current pixel by using the neighboring pixels of the target block in the current frame according to the intra prediction mode read by the intra prediction mode reading unit 1030, and the inverse transform unit 1040. In operation S1113, the current block is restored by adding the prediction error value inversely transformed by the "
  • the image decoding apparatus 600 Since image encoding and decoding are performed in this manner, the image decoding apparatus 600 generates a different adaptive converter according to an intra prediction mode by referring to a previous frame and performs transform encoding. In operation 1000, an exact same adaptive converter may be generated with reference to the previous frame where decoding is completed, thereby performing inverse transform and decoding.
  • embodiments of the present invention are applied to fields such as encoders, decoders, and image compression apparatuses that use intra prediction, so that prediction errors as well as intra prediction modes are used to more efficiently transform-code prediction errors after intra prediction. It is a very useful invention to generate an effect that can increase the compression efficiency of intra prediction coding by adaptively generating a converter low according to the local characteristic change of and using it for transform coding of prediction error.

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Abstract

La présente invention concerne un appareil et un procédé d'encodage d'image, un appareil et un procédé d'encodage par transformée, un appareil et un procédé pour générer une base de transformée, et un appareil et un procédé de décodage d'image associés. L'appareil d'encodage d'image selon un mode de réalisation de la présente invention comprend : une unité de collecte d'erreur de prédiction interne, qui collecte les erreurs de prédiction de blocs ayant le même mode de prédiction interne à partir de macro-blocs d'une unité prédéterminée encodés avant l'encodage du macro-bloc actuel ; une unité de génération de base de transformée, qui génère des bases de transformée pour chaque mode de prédiction interne en se basant sur les erreurs de prédiction collectées par l'unité de collecte d'erreur de prédiction interne ; une unité de prédiction interne, qui prédit la valeur du pixel actuel en utilisant les pixels périphériques existant autour d'un bloc cible dans la trame actuelle en fonction d'un mode de prédiction interne directionnel, et génère une erreur de prédiction en utilisant la différence entre la valeur de pixel actuelle et la valeur de pixel prédite ; et une unité d'encodage par transformée, qui encode par transformée l'erreur de prédiction générée par l'unité de prédiction interne en utilisant la base de transformée générée par l'unité de génération de base de transformée. Selon la présente invention, les bases de transformée sont générées de manière adaptative en fonction de la variation des caractéristiques des images, et les erreurs de prédiction interne sont encodées par transformée en utilisant les bases de transformée ainsi générées, ce qui permet d'améliorer significativement les performances d'encodage de prédiction interne sans ajouter de quelconques informations supplémentaires, et d'améliorer remarquablement le rendement de compression d'un appareil de compression vidéo ou la qualité d'une image restituée.
PCT/KR2010/008777 2009-12-09 2010-12-09 Appareil et procédé d'encodage d'image, appareil et procédé d'encodage par transformée, appareil et procédé pour générer une base de transformée, et appareil et procédé de décodage d'image associés WO2011071316A2 (fr)

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EP2795897A4 (fr) * 2011-12-21 2015-08-05 Intel Corp Compression sans perte perceptuelle de données d'image permettant de réduire la bande passante de la mémoire et le stockage
WO2016167538A1 (fr) * 2015-04-12 2016-10-20 엘지전자(주) Procédé de codage et de décodage de signal vidéo, et appareil associé
TWI761551B (zh) * 2017-07-13 2022-04-21 美商松下電器（美國）知識產權公司 編碼裝置、編碼方法、解碼裝置及解碼方法
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EP3820151B1 (fr) * 2019-06-25 2023-06-14 Guangdong Oppo Mobile Telecommunications Corp., Ltd. Procédé de codage d'image, procédé de décodage d'image, codeur, décodeur et support de stockage

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