# US 10,313,667 B2 · Method and apparatus for encoding/decoding image using transform skip flag

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- Number: US 10,313,667 B2
- Document ID: US10313667B2
- Status: Granted
- Kind: B2
- Application number: 15/891,598
- Filed: 2018-02-08
- Published: 2018-06-14
- Granted: 2019-06-04
- Earliest claimed: 2011-10-19
- Assignees: Kt Corporation
- Applicants: Kt Corporation
- Inventors: Bae Keun Lee; Jae Cheol Kwon; Joo Young Kim
- Web page: https://patentgrep.com/patent/US10313667B2

## CPC

- H04N 19/107: between spatial and temporal predictive coding, e.g. picture refresh
- H04N 19/103: Selection of coding mode or of prediction mode
- H04N 19/105: Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
- H04N 19/11: among a plurality of spatial predictive coding modes
- H04N 19/12: 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
- H04N 19/122: Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
- H04N 19/124: Quantisation
- H04N 19/13: Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
- H04N 19/136: Incoming video signal characteristics or properties
- H04N 19/139: Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
- H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/18: the unit being a set of transform coefficients
- H04N 19/186: the unit being a colour or a chrominance component
- H04N 19/439: {using cascaded computational arrangements for performing a single operation, e.g. filtering}
- H04N 19/44: Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
- H04N 19/593: involving spatial prediction techniques
- H04N 19/61: in combination with predictive coding
- H04N 19/182: the unit being a pixel
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Provided is a method for decoding an image. The method includes: deciding a prediction mode that corresponds to a chroma component block; deciding a transform skip mode of the chroma component block from a plurality of transform skip mode candidates, according to the prediction mode that corresponds to the chroma component block; and reverse-transforming the chroma component block on the basis of the transform skip mode that is decided.

## Claims

### Claim 1

A method of decoding, based on loss coding, a video signal having a current block to be decoded with a decoding apparatus, comprising:
obtaining, from the video signal, residual coefficients relating to the current block, the residual coefficients including first residual coefficients relating to luma components of the current block and second residual coefficients relating to chroma components of the current block;
obtaining, from the video signal,
a first transform skip flag relating to the luma components and a second transform skip flag relating to the chroma components;
performing an inverse-quantization on the first residual coefficients and the second residual coefficients of the current block;
obtaining residual samples of the current block by selectively performing an inverse-transform for first inverse-quantized residual coefficients resulting from the inverse quantization of the first residual coefficients and second inverse-quantized residual coefficients resulting from the inverse-quantization of the second residual coefficients,
wherein the first transform skip flag specifies whether the inverse-transform is performed or skipped on the first inverse-quantized residual coefficients resulting from the inverse-quantization of the first residual coefficients, and the second transform skip flag specifies whether the inverse-transform is performed or skipped on the second inverse-quantized residual coefficients resulting from the inverse-quantization of the second residual coefficients, and
wherein whether to perform or skip the inverse-transform on the second inverse-quantized residual coefficients is determined independently of whether to perform or skip the inverse-transform on the first inverse-quantized residual coefficients;
determining a prediction mode of the current block based on prediction mode information, the prediction mode information specifying whether the current block is an inter-coded block or an intra-coded block;
obtaining prediction samples of the current block based on the prediction mode of the current block;
reconstructing the current block by using the residual samples and the prediction samples; and
applying a deblocking filter to reconstructed samples of the current block.

### Claim 2 (depends on 1)

The method of claim 1, wherein the inverse-transform includes a transform on rows of the current block and a transform on columns of the current block.

### Claim 3 (depends on 2)

The method of claim 2, wherein the inverse-transform is performed by using one of a discrete cosine transform and a discrete sine transform.

### Claim 4 (depends on 1)

The method of claim 1, wherein when the prediction mode of the current block is determined to be an intra prediction, an intra prediction mode of the chroma component is determined based on an intra prediction mode of the luma component.

### Claim 5 (depends on 1)

The method of claim 1, further comprising applying a sample adaptive offset filter to the deblocking-filtered reconstructed samples of the current block.

### Claim 6 (depends on 5)

The method of claim 5, wherein applying the sample adaptive offset filter is performed on a sample by sample basis.