US-12621448-B2 - Method and apparatus for encoding/decoding image, for performing deblocking filtering by determining boundary strength, and method for transmitting bitstream

US12621448B2US 12621448 B2US12621448 B2US 12621448B2US-12621448-B2

Abstract

An image encoding/decoding method and apparatus are provided. An image decoding method according to the present disclosure may comprise obtaining a reconstructed picture, determining a target boundary of deblocking filtering in the reconstructed picture, determining a boundary strength for the target boundary, and applying deblocking filtering to the target boundary based on the boundary strength. Based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chroma component, the boundary strength may be determined based on whether joint CbCr residual coding is performed on at least one of two blocks adjacent to the target boundary, and the joint CbCr residual coding may correspond to encoding residual samples for a chroma Cb component and a chroma Cr component as a single transform block.

Inventors

Hyeong Moon JANG
Sangheon Lee

Assignees

GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP., LTD.

Dates

Publication Date: 20260505
Application Date: 20240708

Claims (14)

1 . An image decoding method performed by an image decoding apparatus, the image decoding method comprising: obtaining, from a bitstream, a first flag specifying whether joint CbCr residual coding is performed on a first block adjacent a target boundary of deblocking filtering, a second flag specifying whether joint CbCr residual coding is performed on a second block adjacent the target boundary, a third flag specifying whether the first block includes a non-zero transform coefficient level, and a fourth flag specifying whether the second block includes a non-zero transform coefficient level; obtaining a reconstructed picture; determining the target boundary in the reconstructed picture; determining a boundary strength for the target boundary; and applying deblocking filtering to the target boundary based on the boundary strength, wherein based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chroma component, the boundary strength is determined based on the first flag, the second flag, the third flag, and the fourth flag.
2 . The image decoding method of claim 1 , wherein the boundary strength is determined to be 1, based on a sum of the first flag, the second flag, the third flag, and the fourth flag being greater than 0.
3 . The image decoding method of claim 1 , wherein based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a luma component, the boundary strength is determined based on whether at least one of the first block and the second block includes a non-zero transform coefficient level.
4 . The image decoding method of claim 1 , wherein the joint CbCr residual coding corresponds to coding residual samples for a chroma Cb component and a chroma Cr component as a single transform block.
5 . An image encoding method performed by an image encoding apparatus, the image encoding method comprising: generating a reconstructed picture; determining a target boundary in the reconstructed picture; determining a boundary strength for the target boundary; and applying deblocking filtering to the target boundary based on the boundary strength, wherein based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chroma component, the boundary strength is determined based on a first flag specifying whether joint CbCr residual coding is performed on a first block adjacent the target boundary, a second flag specifying whether joint CbCr residual coding is performed on a second block adjacent the target boundary, a third flag specifying whether the first block includes a non-zero transform coefficient level, and a fourth flag specifying whether the second block includes a non-zero transform coefficient level, and wherein the first flag, the second flag, the third flag, and the fourth flag are encoded in a bitstream.
6 . The image encoding method of claim 5 , wherein the boundary strength is determined to be 1, based on a sum of the first flag, the second flag, the third flag, and the fourth flag being greater than 0.
7 . The image encoding method of claim 5 , wherein based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a luma component, the boundary strength is determined based on whether at least one of the first block and the second block includes a non-zero transform coefficient level.
8 . The image encoding method of claim 5 , wherein the joint CbCr residual coding corresponds to coding residual samples for a chroma Cb component and a chroma Cr component as a single transform block.
9 . An image decoding apparatus comprising at least one processor and a memory storing instructions which, when executed by the at least one processor, cause the image decoding apparatus to: obtain, from a bitstream, a first flag specifying whether joint CbCr residual coding is performed on a first block adjacent a target boundary of deblocking filtering, a second flag specifying whether joint CbCr residual coding is performed on a second block adjacent the target boundary, a third flag specifying whether the first block includes a non-zero transform coefficient level, and a fourth flag specifying whether the second block includes a non-zero transform coefficient level; obtain a reconstructed picture; determine the target boundary in the reconstructed picture; determine a boundary strength for the target boundary; and apply deblocking filtering to the target boundary based on the boundary strength, wherein, based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chroma component, the boundary strength is determined based on the first flag, the second flag, the third flag, and the fourth flag.
10 . The image decoding apparatus of claim 9 , wherein the boundary strength is determined to be 1, based on a sum of the first flag, the second flag, the third flag, and the fourth flag being greater than 0.
11 . The image decoding apparatus of claim 9 , wherein based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a luma component, the boundary strength is determined based on whether at least one of the first block and the second block includes a non-zero transform coefficient level.
12 . The image decoding apparatus of claim 9 , wherein the joint CbCr residual coding corresponds to coding residual samples for a chroma Cb component and a chroma Cr component as a single transform block.
13 . An image encoding apparatus comprising at least one processor and a memory storing instructions which, when executed by the at least one processor, cause the image encoding apparatus to perform the image encoding method of claim 5 .
14 . A non-transitory computer-readable storage medium storing a bitstream and a computer program, wherein when executed by a processor, the computer program enables the processor to generate the bitstream according to the image encoding method of claim 5 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 18/206,499, filed on Jun. 6, 2023, which is a continuation of U.S. application Ser. No. 17/914,492, filed on Sep. 26, 2022, which is a U.S. National Stage Entry of International Application No. PCT/KR2021/003309, filed on Mar. 17, 2021, which claims the benefit of U.S. Provisional Application No. 62/994,831, filed on Mar. 25, 2020. The entire disclosures of the aforementioned applications are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to an image encoding/decoding method and apparatus and, more particularly, to an image encoding/decoding method and apparatus for performing deblocking filtering by determining a boundary strength and a method of transmitting a bitstream generated by the image encoding method/apparatus of the present disclosure. BACKGROUND ART Recently, demand for high-resolution and high-quality images such as high definition (HD) images and ultra high definition (UHD) images is increasing in various fields. As resolution and quality of image data are improved, the amount of transmitted information or bits relatively increases as compared to existing image data. An increase in the amount of transmitted information or bits causes an increase in transmission cost and storage cost. Accordingly, there is a need for high-efficient image compression technology for effectively transmitting, storing and reproducing information on high-resolution and high-quality images. DISCLOSURE Technical Problem An object of the present disclosure is to provide an image encoding/decoding method and apparatus with improved encoding/decoding efficiency. Another object of the present disclosure is to provide an image encoding/decoding method and apparatus for performing deblocking filtering. Another object of the present disclosure is to provide an image encoding/decoding method and apparatus for determining a boundary strength of deblocking filtering in order to perform deblocking filtering. Another object of the present disclosure is to provide a method of transmitting a bitstream generated by an image encoding method or apparatus according to the present disclosure. Another object of the present disclosure is to provide a recording medium storing a bitstream generated by an image encoding method or apparatus according to the present disclosure. Another object of the present disclosure is to provide a recording medium storing a bitstream received, decoded and used to reconstruct an image by an image decoding apparatus according to the present disclosure. The technical problems solved by the present disclosure are not limited to the above technical problems and other technical problems which are not described herein will become apparent to those skilled in the art from the following description. Technical Solution An image decoding method according to an aspect of the present disclosure is performed by an image decoding apparatus. The image decoding method comprises obtaining a reconstructed picture; determining a target boundary of deblocking filtering in the reconstructed picture, determining a boundary strength for the target boundary, and applying deblocking filtering to the target boundary based on the boundary strength. Based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chroma component, the boundary strength may be determined based on whether joint CbCr residual coding is performed on at least one of two blocks adjacent to the target boundary, and the joint CbCr residual coding may correspond to encoding residual samples for a chroma Cb component and a chroma Cr component as a single transform block. In the image decoding method according to the present disclosure, whether joint CbCr residual coding may be performed on a block adjacent to the target boundary is determined based on a first flag signaled for the adjacent block. In the image decoding method according to the present disclosure, based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a chroma component, the boundary strength may be determined further based on whether at least one of two blocks adjacent to the target boundary includes a non-zero transform coefficient level. In the image decoding method according to the present disclosure, whether a block adjacent to the target boundary includes at least one non-zero transform coefficient level may be determined based on a second flag signaled for the adjacent block. In the image decoding method according to the present disclosure, based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a chroma component, the boundary strength may be determined based on a sum of two first flags and two second flags for two blocks adjacent to the target boundary. In the image deco