METHOD AND DEVICE FOR ENCODING OR DECODING IMAGE

• US 20180309990A1
• Filed: 10/13/2016
• Published: 10/25/2018
• Est. Priority Date: 10/13/2015
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: ALSHINA, Elena, MISHUROVSKIY, Mikhail, ALSHIN, Alexander
• Granted Patent: US 10,939,104 B2
• Time in Patent Office: Days
• CPC Class Codes: H04N 19/109 among a plurality of temporal predictive coding modes
• CPC Class Codes: H04N 19/11 among a plurality of spatial predictive coding modes
• CPC Class Codes: H04N 19/122 Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
• 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 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• 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 19/182 the unit being a pixel
• CPC Class Codes: H04N 19/194 involving only two passes
• CPC Class Codes: H04N 19/436 using parallelised computational arrangements
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/45 performing compensation of the inverse transform mismatch, e.g. Inverse Discrete Cosine Transform [IDCT] mismatch
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/537 Motion estimation other than block-based
• CPC Class Codes: H04N 19/57 Motion estimation characterised by a search window with variable size or shape
• CPC Class Codes: H04N 19/593 : involving spatial prediction techniques
• CPC Class Codes: H04N 19/61 : in combination with predictive coding
• CPC Class Codes: H04N 19/63 : using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/70 : characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/91 : Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Abstract

An image decoding method and apparatus according to an embodiment may extract, from a bitstream, a quantization coefficient generated through core transformation, secondary transformation, and quantization; generate an inverse-quantization coefficient by performing inverse quantization on the quantization coefficient; generate a secondary inverse-transformation coefficient by performing secondary inverse-transformation on a low frequency component of the inverse-quantization coefficient, the secondary inverse-transformation corresponding to the secondary transformation; and perform core inverse-transformation on the secondary inverse-transformation coefficient, the core inverse-transformation corresponding to the core transformation.

Claims

1. An image decoding method comprising:

extracting, from a bitstream, a quantization coefficient generated through core transformation, secondary transformation, and quantization;

generating an inverse-quantization coefficient by performing inverse quantization on the quantization coefficient;

generating a secondary inverse-transformation coefficient by performing secondary inverse-transformation on a low frequency component of the inverse-quantization coefficient, the secondary inverse-transformation corresponding to the secondary transformation; and

performing core inverse-transformation on the secondary inverse-transformation coefficient, the core inverse-transformation corresponding to the core transformation.

2. The image decoding method of claim 1, further comprising obtaining, from the bitstream, information about whether to perform the secondary inverse-transformation, and

wherein the secondary inverse-transformation is performed based on the information about whether to perform the secondary inverse-transformation.

3. The image decoding method of claim 1, wherein the secondary inverse-transformation is performed on a sub-group unit in a transformation block, and a size of the sub-group unit is determined based on a size of the transformation block or a quantization parameter.

4. The image decoding method of claim 3, wherein a type of the secondary inverse-transformation to be performed on the sub-group unit is determined based on a location of the sub-group unit.

5. An entropy decoding method comprising:

obtaining, from a received bitstream, probability information used in performing arithmetic decoding on a current bin by updating, by using a first probability model and a second probability model, previous probability information that was used in performing arithmetic decoding on a previous bin;

obtaining the current bin by performing arithmetic decoding based on the obtained probability information; and

obtaining a syntax element by de-binarizing the obtained current bin,

wherein the first probability model and the second probability model each use a size of a window indicating a number of bins decoded prior to the current bin, and a size of a window of the first probability model is less than a size of a window of the second probability model.

6. The entropy decoding method of claim 5, wherein the size of the window of the first probability model and the size of the window of the second probability model are obtained from the bitstream.

7. The entropy decoding method of claim 5, wherein one of the size of the window of the first probability model and the size of the window of the second probability model has a fixed value.

8. An image decoding method comprising:

extracting, from a received bitstream, prediction mode information of a current block to be decoded;

generating a first prediction block with respect to the current block based on the extracted prediction mode information;

extracting, from the bitstream, calculation information about a calculation in which each pixel constituting the first prediction block and adjacent pixels of the each pixel are used;

generating a second prediction block by changing a pixel value of the each pixel via a calculation with respect to the each pixel constituting the first prediction block and pixels positioned at upper and left portions of the each pixel, based on the extracted calculation information;

extracting, from the bitstream, and reconstructing a residual corresponding to a difference value between the current block and the second prediction block; and

decoding the current block by adding the residual and the second prediction block,

wherein

the calculation information comprises parameter index information, and

the parameter index information comprises a first weight parameter applied to the each pixel constituting the first prediction block, a second weight parameter applied to a pixel positioned at the upper portion of the each pixel, and a third weight parameter applied to a pixel positioned at the left portion of the each pixel.

9. The image decoding method of claim 8, wherein the parameter index information is defined with respect to each of coding units respectively having 2N×

2N and N×

N sizes.

10. The image decoding method of claim 8, wherein the parameter index information is comprised in the prediction mode information.

11. The image decoding method of claim 8, wherein the parameter index information is obtained from the bitstream at a level of a coding unit or a prediction unit.

12. An image decoding method comprising:

receiving a bitstream;

determining whether to perform pixel unit motion compensation on a current block, based on information about whether the pixel unit motion compensation is limited, the information being extracted from the bitstream;

when the pixel unit motion compensation is performed, extracting, from the bitstream, information about a first motion vector and a second motion vector respectively indicating a first corresponding region and a second corresponding region which are most similar to the current block in a first reference picture and a second reference picture;

performing block unit bi-directional motion compensation on the current block by using the first motion vector and the second motion vector;

performing the pixel unit motion compensation on each pixel of the current block by using pixels of the first reference picture and the second reference picture; and

generating a bi-directional motion prediction value of the current block by using a result of the block unit bi-directional motion compensation and a result of the pixel unit motion compensation.

13. The image decoding method of claim 12, wherein

the information about whether the pixel unit motion compensation is limited comprises at least one of a coded block flag (CBF), information indicating whether to perform motion compensation by using derived motion information, information indicating whether to perform local illumination compensation, and information indicating whether to perform affine motion compensation, and

when the CBF is not 0, the motion compensation is performed by using the derived motion information, the local illumination compensation is performed, or the affine motion compensation is performed, the pixel unit motion compensation is not performed.

14. The image decoding method of claim 13, wherein the performing of the pixel unit motion compensation comprises generating a pixel unit motion compensation value of the each pixel of the current block by using horizontal and vertical direction gradients of a first corresponding pixel of the first reference picture corresponding to the each pixel of the current block, horizontal and vertical direction gradients of a second corresponding pixel of the second reference picture corresponding to the each pixel of the current block, and a horizontal direction displacement vector and a vertical direction displacement vector determined by using the pixels of the first reference picture and the second reference picture.

15. The image decoding method of claim 14, wherein the horizontal direction displacement vector and the vertical direction displacement vector are determined to be horizontal and vertical direction displacement vectors by which a difference value between a first displacement value and a second displacement value becomes a minimum value, wherein the first displacement value is obtained by displacing the first corresponding pixel of the first reference picture in a window region having a predetermined size by using the horizontal and vertical direction displacement vectors and the horizontal and vertical direction gradients of the first corresponding pixel, and the second displacement value is obtained by displacing the second corresponding pixel of the second reference picture by using the horizontal and vertical direction displacement vectors and the horizontal and vertical direction gradients of the second corresponding pixel.