# US 2022/0286708 A1 · Methods and apparatus on transform and coefficient signaling

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2022/0286708 A1
- Document ID: US20220286708A1
- Status: Published application
- Kind: A1
- Application number: 17/750,169
- Filed: 2022-05-20
- Published: 2022-09-08
- Earliest claimed: 2019-11-21
- Assignees: Beijing Dajia Internet Information Technology Co., Ltd.
- Applicants: Beijing Dajia Internet Information Technology Co., Ltd.
- Inventors: Xiaoyu XIU; Tsung-Chuan MA; Yi-Wen CHEN; Xianglin WANG; Hong-Jheng JHU; Bing YU
- Web page: https://patentgrep.com/patent/US20220286708A1

## CPC

- 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 19/625: using discrete cosine transform [DCT]
- H04N 19/129: Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
- H04N 19/14: Coding unit complexity, e.g. amount of activity or edge presence estimation (H04N19/146 takes precedence)
- 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 19/46: Embedding additional information in the video signal during the compression process (H04N19/517, H04N19/68, H04N19/70 take precedence)
- H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An electronic apparatus performs a method of encoding and decoding video data. The method comprises: receiving bitstream encoding a transform block, wherein the transform block includes a non-zero region and a zero-out region; checking whether there is any non-zero coefficient within the zero-out region; in accordance with a determination that there is no non-zero coefficient within the zero-out region of the transform block: determining a scan order index of a last non-zero coefficient of the transform block along a scanning direction; in accordance with a determination that the scan order index of the last non-zero coefficient is greater than a predefined threshold: receiving, from the bitstream, a value for multiple transform selection (MTS) index; and applying respective transforms to transform coefficients of the transform block in both horizontal and vertical directions based on the value of the MTS index.

## Claims

### Claim 1

A method of decoding video data, the method comprising:
receiving bitstream encoding a transform block, wherein the transform block includes a non-zero region and a zero-out region;
checking whether there is any non-zero coefficient within the zero-out region;
in accordance with a determination that there is no non-zero coefficient within the zero-out region of the transform block:
determining a scan order index of a last non-zero coefficient of the transform block along a scanning direction;
in accordance with a determination that the scan order index of the last non-zero coefficient is greater than a predefined threshold:
receiving, from the bitstream, a value for multiple transform selection (MTS) index; and
applying respective transforms to transform coefficients of the transform block in both horizontal and vertical directions based on the value of the MTS index.

### Claim 2 (depends on 1)

The method of claim 1, further including:
in accordance with a determination that there is non-zero coefficient within the zero-out region of the transform block:
applying a predefined default transform to transform the coefficients of the transform block in both the horizontal and vertical directions.

### Claim 3 (depends on 1)

The method of claim 1, further including:
in accordance with a determination that the scan order index of the last non-zero coefficient is not greater than the predefined threshold:
applying a predefined default transform to transform the coefficients of the transform block in both the horizontal and vertical directions.

### Claim 4 (depends on 1)

The method of claim 1, wherein applying respective transforms to transform coefficients of the transform block in both horizontal and vertical directions based on the value of the MTS index includes:
in accordance with a determination that the MTS index has a first value:
receiving, from the bitstream, a value for a MTS horizontal flag and a value for a MTS vertical flag;
applying a horizontal transform to the coefficients of the transform block in the horizontal direction based on the value for the MTS horizontal flag; and
applying a vertical transform to the coefficients of the transform block after the horizontal transform in the vertical direction based on the value for the MTS vertical flag; and
in accordance with a determination that the MTS index has a second value that is different from the first value:
transforming the coefficients of the transform block using a predefined default transform in both the horizontal and vertical directions.

### Claim 5 (depends on 2)

The method of claim 2, wherein the predefined default transform is DCT-2 transform and the horizontal transform and the vertical transform are either DST-7 transform or DCT-8 transform.

### Claim 6 (depends on 1)

The method of claim 1, wherein checking whether there is any non-zero coefficient within the zero-out region further includes:
checking coded block flags (CBFs) of luma coefficient groups within the zero-out region; and
determining that there is no non-zero coefficient within the zero-out region only if the CBFs of all the luma coefficient groups within the zero-out region are zero.

### Claim 7 (depends on 1)

The method of claim 1, wherein checking whether there is any non-zero coefficient within the zero-out region further includes:
checking horizontal coordinate and vertical coordinate of the last non-zero coefficient; and
determining that there is at least one non-zero coefficient within the zero-out region when either the horizontal coordinate or the vertical coordinate of the last non-zero coefficient is within the zero-out region.

### Claim 8 (depends on 1)

The method of claim 1, wherein chroma residuals of the transform block are coded in joint coding of chroma residuals (JCCR) mode and chroma transform skip mode is enabled for the transform block.

### Claim 9 (depends on 1)

The method of claim 1, wherein the non-zero region is a top-left 16×16 region of the transform block.

### Claim 10 (depends on 1)

The method of claim 1, wherein the scan order is a diagonal scan order.

### Claim 11

An electronic apparatus comprising:
one or more processing units; and
a memory coupled to the one or more processing units and configured to store a plurality of programs executable by the one or more processing units,
wherein the one or more processing units are configured to:
receive bitstream encoding a transform block, wherein the transform block includes a non-zero region and a zero-out region;
check whether there is any non-zero coefficient within the zero-out region;
in accordance with a determination that there is no non-zero coefficient within the zero-out region of the transform block:
determine a scan order index of a last non-zero coefficient of the transform block along a scanning direction;
in accordance with a determination that the scan order index of the last non-zero coefficient is greater than a predefined threshold:
receive, from the bitstream, a value for multiple transform selection (MTS) index; and
apply respective transforms to transform coefficients of the transform block in both horizontal and vertical directions based on the value of the MTS index.

### Claim 12 (depends on 11)

The electronic apparatus of claim 11, wherein the one or more processing units are further configured to:
in accordance with a determination that there is non-zero coefficient within the zero-out region of the transform block:
apply a predefined default transform to transform the coefficients of the transform block in both the horizontal and vertical directions.

### Claim 13 (depends on 11)

The electronic apparatus of claim 11, wherein the one or more processing units are further configured to:
in accordance with a determination that the scan order index of the last non-zero coefficient is not greater than the predefined threshold:
apply a predefined default transform to transform the coefficients of the transform block in both the horizontal and vertical directions.

### Claim 14 (depends on 11)

The electronic apparatus of claim 11, wherein the one or more processing units are further configured to:
in accordance with a determination that the MTS index has a first value:
receive, from the bitstream, a value for a MTS horizontal flag and a value for a MTS vertical flag;
apply a horizontal transform to the coefficients of the transform block in the horizontal direction based on the value for the MTS horizontal flag; and
apply a vertical transform to the coefficients of the transform block after the horizontal transform in the vertical direction based on the value for the MTS vertical flag; and
in accordance with a determination that the MTS index has a second value that is different from the first value:
transform the coefficients of the transform block using a predefined default transform in both the horizontal and vertical directions.

### Claim 15 (depends on 12)

The electronic apparatus of claim 12, wherein the predefined default transform is DCT-2 transform and the horizontal transform and the vertical transform are either DST-7 transform or DCT-8 transform.

### Claim 16 (depends on 11)

The electronic apparatus of claim 11, wherein the one or more processing units are further configured to:
check coded block flags (CBFs) of luma coefficient groups within the zero-out region; and
determine that there is no non-zero coefficient within the zero-out region only if the CBFs of all the luma coefficient groups within the zero-out region are zero.

### Claim 17 (depends on 11)

The electronic apparatus of claim 11, wherein the one or more processing units are further configured to:
check horizontal coordinate and vertical coordinate of the last non-zero coefficient; and
determine that there is at least one non-zero coefficient within the zero-out region when either the horizontal coordinate or the vertical coordinate of the last non-zero coefficient is within the zero-out region.

### Claim 18 (depends on 11)

The electronic apparatus of claim 11, wherein chroma residuals of the transform block are coded in joint coding of chroma residuals (JCCR) mode and chroma transform skip mode is enabled for the transform block.

### Claim 19 (depends on 11)

The electronic apparatus of claim 11, wherein the non-zero region is a top-left 16×16 region of the transform block.

### Claim 20

A non-transitory computer readable storage medium storing a plurality of programs for execution by an electronic apparatus having one or more processing units, wherein the plurality of programs, when executed by the one or more processing units, cause the electronic apparatus to perform a method of decoding video data, the method including:
receiving bitstream encoding a transform block, wherein the transform block includes a non-zero region and a zero-out region;
checking whether there is any non-zero coefficient within the zero-out region;
in accordance with a determination that there is no non-zero coefficient within the zero-out region of the transform block:
determining a scan order index of a last non-zero coefficient of the transform block along a scanning direction;
in accordance with a determination that the scan order index of the last non-zero coefficient is greater than a predefined threshold:
receiving, from the bitstream, a value for multiple transform selection (MTS) index; and
applying respective transforms to transform coefficients of the transform block in both horizontal and vertical directions based on the value of the MTS index.