# US 9,521,430 B2 · Method and apparatus for determining a context model for transform coefficient level entropy encoding and decoding

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- Number: US 9,521,430 B2
- Document ID: US9521430B2
- Status: Granted
- Kind: B2
- Application number: 14/678,664
- Filed: 2015-04-03
- Published: 2015-07-30
- Granted: 2016-12-13
- Earliest claimed: 2011-10-31
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Samsung Electronics Co., Ltd.
- Inventors: Yin-ji Piao; Jung-hye Min
- Web page: https://patentgrep.com/patent/US9521430B2

## CPC

- H04N 19/60: using transform coding
- 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 19/91: Entropy coding, e.g. variable length coding [VLC] or arithmetic coding
- H04N 19/13: Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Provided are a method and apparatus for determining a context model for entropy encoding and decoding of a transformation coefficient. According to the method and apparatus, a context set index ctxset is obtained based on color component information of a transformation unit, a location of a current subset, and whether there is a significant transformation coefficient having a value greater than a first critical value in a previous subset, and a context offset c1 is obtained based on a length of a previous transformation coefficient having consecutive 1s. Also, a context index ctxids for entropy encoding and decoding of a first critical value flag is determined based on the obtained context set index and the context offset.

## Claims

### Claim 1

A method of determining a context model for entropy decoding, the method comprising:
determining a current transform unit based on size information of a transform unit, wherein the size information is obtained from a bitstream;
when the current transform unit is a transform unit of a chroma component, determining a context set of a current sub-block in the current transform unit independently of a position of the current sub-block;
when the current transform unit is a transform unit of a luminance component, determining the context set of the current sub-block in the current transform unit based on the position of current sub-block;
determining a context model for obtaining first threshold value information based on the context set of the current sub-block; and
determining a context model for obtaining second threshold value information based on the context set of the current sub-block,
wherein the first threshold value information indicates whether a current transformation coefficient in the current sub-block is greater than a first threshold value, and the second threshold value information indicates whether a current transformation coefficient in the current sub-block is greater than a second threshold value.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first threshold value is 1, and the second threshold value is 2.