US-12621454-B2 - Image processing method, and device for same

US12621454B2US 12621454 B2US12621454 B2US 12621454B2US-12621454-B2

Abstract

The present invention discloses a method for encoding/decoding a video signal and an apparatus for the method. More specifically, a method for decoding a video signal comprises generating a residual block of a current block by performing entropy decoding on the video signal; if size of the current block is smaller than a predetermined first size, parsing a transform skip flag which indicates whether a transform skip is applied to the current block; determining whether to parse a primary transform flag which indicates whether a primary transform is applied to the current block; if it is determined to parse the primary transform flag, parsing the primary transform flag; and if the primary transform flag indicates that a primary transform is applied to the current block, generating a primary inverse transformed transform block of the current block by performing a primary inverse transform to the residual block.

Inventors

Hyeongmoon JANG
Junghak NAM
Seunghwan Kim
Jaehyun Lim

Assignees

GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP., LTD.

Dates

Publication Date: 20260505
Application Date: 20241226

Claims (9)

1 . An apparatus for decoding a video signal, comprising: a memory configured to store the video signal; and a processor coupled with the memory, wherein the processor is configured to: parse a transform skip flag specifying whether a transform is applied to a current block based on a size of the current block being smaller than a predetermined first size; obtain an index specifying one of a plurality of transform kernel combinations to be applied to the current block based on the transform skip flag, each transform kernel combination being composed of a transform kernel in a horizontal direction and a transform kernel in a vertical direction; and generate an inverse transformed transform block of the current block by performing an inverse transform to coefficients of the current block based on the transform kernel combination specified by the index, wherein for obtaining the index, the processor is further configured to: check a value of the index related to obtaining the index, based on the transform skip flag being 0; and derive for the transform kernels in the horizontal and vertical directions as a same transform kernel based on the value of the index being 0.
2 . The apparatus of claim 1 , wherein for obtaining the index, the processor is further configured to: check whether a non-zero transform coefficient exists in the current block; and obtain the index based on a determination from the checking result that the non-zero transform coefficient exists in the current block.
3 . The apparatus of claim 1 , wherein the predetermined first size is configured differently based on a slice of the current block.
4 . An apparatus for encoding a video signal, comprising: a memory configured to store the video signal; and a processor coupled with the memory, wherein the processor is configured to: generate a transform skip flag specifying whether a transform is applied to a current block based on a size of the current block being smaller than a predetermined first size; generate an index specifying one among a plurality of transform kernel combinations to be applied to the current block based on the transform skip flag, each transform kernel combination being composed of a transform kernel in a horizontal direction and a transform kernel in a vertical direction; perform the transform to coefficients of the current block based on the transform kernel combination specified by the index to obtain a transformed block of the current block; and perform quantization and entropy encoding on the transformed block, wherein for generating the index, the processor is further configured to: check a value of the index related to generating the index, based on the transform skip flag being 0; and derive for the transform kernels in the horizontal and vertical directions as a same transform kernel without generating the index, based on the value of the index being 0.
5 . A method for decoding a video signal, comprising: parsing a transform skip flag specifying whether a transform is applied to a current block based on a size of the current block being smaller than a predetermined first size; obtaining an index specifying one of a plurality of transform kernel combinations to be applied to the current block based on the transform skip flag, each transform kernel combination being composed of a transform kernel in a horizontal direction and a transform kernel in a vertical direction; and generating an inverse transformed transform block of the current block by performing an inverse transform to coefficients of the current block based on the transform kernel combination specified by the index, wherein obtaining the index further comprises: checking a value of the index related to obtaining the index, based on the transform skip flag being 0; and deriving for the transform kernels in the horizontal and vertical directions as a same transform kernel based on the value of the index being 0.
6 . The method of claim 5 , wherein obtaining the index further comprises: checking whether a non-zero transform coefficient exists in the current block; and obtaining the index based on a determination from the checking result that the non-zero transform coefficient exists in the current block.
7 . The method of claim 5 , wherein the predetermined first size is configured differently based on a slice of the current block.
8 . A method for encoding a video signal, comprising: generating a transform skip flag specifying whether a transform is applied to a current block based on a size of the current block being smaller than a predetermined first size; generating an index specifying one among a plurality of transform kernel combinations to be applied to the current block based on the transform skip flag, each transform kernel combination being composed of a transform kernel in a horizontal direction and a transform kernel in a vertical direction; performing the transform to coefficients of the current block based on the transform kernel combination specified by the index to obtain a transformed block of the current block; and performing quantization and entropy encoding on the transformed block, wherein generating the index further comprises: checking a value of the index related to generating the index, based on the transform skip flag being 0; and deriving for the transform kernels in the horizontal and vertical directions as a same transform kernel without generating the index, based on the value of the index being 0.
9 . A non-transitory computer readable storage medium, storing computer programs and a bitstream, wherein when executed by a processor, the computer programs cause the processor to perform the method of claim 8 to generate the bitstream.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 18/542,173, filed on Dec. 15, 2023, which is a continuation of U.S. application Ser. No. 17/851,953, filed on Jun. 28, 2022, now U.S. Pat. No. 11,882,286, which is a continuation of U.S. application Ser. No. 16/476,033, filed on Jul. 3, 2019, now U.S. Pat. No. 11,394,974, which is a National Stage application under 35 U.S.C. § 371 of International Application No. PCT/KR2017/015590, filed on Dec. 27, 2017, which claims the benefit of U.S. Provisional Application No. 62/446,535, filed on Jan. 16, 2017, and U.S. Provisional Application No. 62/441,588, filed on Jan. 3, 2017. The entire disclosures of the aforementioned applications are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a method and apparatus for encoding/decoding a video signal and, more particularly, to a method for encoding/decoding a video signal, which improves transform-related syntax coding and an apparatus for supporting the method. BACKGROUND ART Compression encoding means a series of signal processing techniques for transmitting digitized information through a communication line or techniques for storing information in a form suitable for a storage medium. The medium including a picture, an image, audio, etc. may be a target for compression encoding, and particularly, a technique for performing compression encoding on a picture is referred to as video image compression. Next-generation video contents are supposed to have the characteristics of high spatial resolution, a high frame rate and high dimensionality of scene representation. In order to process such contents, a drastic increase in the memory storage, memory access rate and processing power will result. Accordingly, it is required to design a coding tool for processing next-generation video contents efficiently. SUMMARY To solve the problem above, an object of the present invention is to provide a method for effectively signaling a flag which determines whether to apply a transform and an index which determines the type of the transform (or a transform kernel). Also, an object of the present invention is to provide a method for effectively signaling a flag which determines whether to apply a primary transform and a flag which determines whether to apply a transform skip. Also, an object of the present invention is to provide a method for referencing context to perform entropy coding on a flag which determines whether to apply a primary transform. Also, an object of the present invention is to provide a method for determining whether to transmit (or parse) a transform skip flag according to a primary transform flag value in a compression structure where a coding unit is not distinguished from a transform unit. Technical objects to be achieved by the present invention are not limited to those described above, and other technical objects not mentioned above may also be clearly understood from the descriptions given below by those skilled in the art to which the present invention belongs. According to one aspect of the present invention, a method for decoding a video signal may comprise generating a residual block of a current block by performing entropy decoding on the video signal; parsing a transform skip flag which indicating whether a transform skip is applied to the current block when size of the current block is smaller than a predetermined first size; determining whether to parse a primary transform flag which indicates whether a primary transform is applied to the current block; parsing the primary transform flag when it is determined to parse the primary transform flag; and generating a primary inverse transformed transform block of the current block by performing a primary inverse transform to the residual block when the primary transform flag indicates that a primary transform is applied to the current block. Preferably, the step of determining whether to parse the primary transform flag may parse the primary transform flag when the transform skip flag is 0. Preferably, the step of determining whether to parse the primary transform flag may determine to parse the primary transform flag when size of the current block is smaller than a predetermined second size, and the transform skip flag is 0. Preferably, the step of determining whether to parse the primary transform flag may determine to parse the primary transform flag when the current block is a luma block, size of the current block is smaller than a predetermined second size, and the transform skip flag is 0. Preferably, the step of parsing the transform skip flag may include checking whether a non-zero transform coefficient exists in the current block and if it is determined from the checking result that the non-zero transform coefficient exists in the current block, parse the transform skip flag. Preferably, the primary transform flag may be entropy-decoded by referencing context