US-12621441-B2 - Method and apparatus for coding intra prediction mode

US12621441B2US 12621441 B2US12621441 B2US 12621441B2US-12621441-B2

Abstract

An image decoding method performed by a decoding apparatus includes: receiving a bitstream including prediction-related information; configuring, on the basis of neighboring blocks of a current block, a list of most probable modes (MPMs) including intra prediction mode candidates for the current block; decoding, from the bitstream, remaining mode information related to remaining intra prediction modes other than the intra prediction mode candidates included in the list of MPMs; deriving an intra prediction mode of the current block on the basis of the remaining mode information; generating prediction samples for the current block on the basis of the intra prediction mode of the current block; and generating reconstructed samples for the current block on the basis of the prediction samples for the current block. On the basis that a decoder side intra mode derivation (DIMD) mode or template based intra mode derivation (TIMD) for the current block can be derived, a plurality of intra prediction modes are derived on the basis of the remaining mode information.

Inventors

Sunmi YOO
Naeri PARK
Junghak NAM
Hyeongmoon JANG
Jangwon CHOI

Assignees

LG ELECTRONICS INC.

Dates

Publication Date: 20260505
Application Date: 20221021
Priority Date: 20211021

Claims (12)

1 . An image decoding method performed by a decoding apparatus, the image decoding method comprising: receiving a bitstream including prediction related information; constructing a Most Probable Modes (MPM) list including intra prediction mode candidates for a current block based on neighboring blocks of the current block; decoding remaining mode information related to remaining intra prediction modes other than the intra prediction mode candidates included in the MPM list from the bitstream; deriving an intra prediction mode of the current block based on the remaining mode information; generating prediction samples for the current block based on the intra prediction mode of the current block; and generating reconstructed samples for the current block based on the prediction samples for the current block, wherein based on a case where a Decoder Side Intra Mode Derivation (DIMD) mode or a Template based Intra Mode Derivation (TIMD) mode is derived from the current block, a plurality of intra prediction modes are derived based on the remaining mode information, wherein one intra prediction mode is selected from among the plurality of intra prediction modes, wherein the selected intra prediction mode is used as the intra prediction mode of the current block, wherein a number of bits representing the remaining mode information is 5, wherein the plurality of intra prediction modes derived based on the remaining mode information include a first intra prediction mode and a second intra prediction mode, wherein based on the case where the DIMD mode is derived for the current block, and wherein a prediction mode with a mode number having a smaller difference from a mode number of the DIMD mode among the first intra prediction mode or the second intra prediction mode is selected as the one intra prediction mode.
2 . The method of claim 1 , wherein based on the case where the TIMD mode is derived for the current block, and wherein a prediction mode having a smaller value of a first Sum of Absolute Transformed Differences (SATD) derived based on the first intra prediction mode or a second SATD derived based on the second intra prediction mode is selected as the one intra prediction mode.
3 . The method of claim 2 , wherein the first SATD is derived based on a first prediction sample and a first reconstructed sample in a template of the current block, and wherein the second SATD is derived based on a second prediction sample and a second reconstructed sample in the template of the current block.
4 . The method of claim 1 , wherein a number of bits representing the remaining mode information is determined based on a size of the current block.
5 . The method of claim 1 , wherein a number of bits representing the remaining mode information is determined based on whether the current block is a square block or a non-square block.
6 . The method of claim 1 , wherein a number of bits representing the remaining mode information is determined based on a prediction mode for a neighboring block of the current block.
7 . The method of claim 1 , wherein whether at least one of the DIMD mode or the TIMD mode is applied is determined based on the size of the current block.
8 . The method of claim 1 , wherein whether at least one of the DIMD mode or the TIMD mode is applied is determined based on whether the current block is a square block or a non-square block.
9 . An image encoding method performed by an encoding apparatus, the image decoding method comprising: constructing a Most Probable Modes (MPM) list including intra prediction mode candidates for a current block based on neighboring blocks of the current block; generating remaining mode information related to remaining intra prediction modes other than the intra prediction mode candidates included in the MPM list; and encoding image information including the remaining mode information, wherein based on a case where a Decoder Side Intra Mode Derivation (DIMD) mode or a Template based Intra Mode Derivation (TIMD) mode is derived from the current block, the remaining mode information represents a plurality of intra prediction modes, wherein one intra prediction mode is selected from among the plurality of intra prediction modes, wherein the selected intra prediction mode is used as the intra prediction mode of the current block, wherein a number of bits representing the remaining mode information is 5, wherein the plurality of intra prediction modes derived based on the remaining mode information include a first intra prediction mode and a second intra prediction mode, wherein based on the case where the DIMD mode is derived for the current block, and wherein a prediction mode with a mode number having a smaller difference from a mode number of the DIMD mode among the first intra prediction mode or the second intra prediction mode is selected as the one intra prediction mode.
10 . The method of claim 9 , wherein based on the case where the TIMD mode is derived for the current block, and wherein a prediction mode having a smaller value of a first Sum of Absolute Transformed Differences (SATD) derived based on the first intra prediction mode or a second SATD derived based on the second intra prediction mode is selected as the one intra prediction mode.
11 . A transmission method of data for an image, the method comprising: obtaining a bitstream for the image, wherein the bitstream is generated based on constructing a Most Probable Modes (MPM) list including intra prediction mode candidates for a current block based on neighboring blocks of the current block, generating remaining mode information related to remaining intra prediction modes other than the intra prediction mode candidates included in the MPM list, and encoding image information including the remaining mode information; and transmitting the data comprising the bitstream, wherein based on a case where a Decoder Side Intra Mode Derivation (DIMD) mode or a Template based Intra Mode Derivation (TIMD) mode is derived from the current block, the remaining mode information represents a plurality of intra prediction modes, wherein one intra prediction mode is selected from among the plurality of intra prediction modes, wherein the selected intra prediction mode is used as the intra prediction mode of the current block, wherein a number of bits representing the remaining mode information is 5, wherein the plurality of intra prediction modes derived based on the remaining mode information include a first intra prediction mode and a second intra prediction mode, wherein the DIMD mode is derived for the current block, and wherein a prediction mode with a mode number having a smaller difference from a mode number of the DIMD mode among the first intra prediction mode or the second intra prediction mode is selected as the one intra prediction mode.
12 . The method of claim 11 , wherein based on the case where the TIMD mode is derived for the current block, and wherein a prediction mode having a smaller value of a first Sum of Absolute Transformed Differences (SATD) derived based on the first intra prediction mode or a second SATD derived based on the second intra prediction mode is selected as the one intra prediction mode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2022/016152, filed on Oct. 21, 2022, which claims the benefit of KR Patent Application No. 10-2021-0141232 filed on Oct. 21, 2021, which is hereby incorporated by reference herein in its entirety. TECHNICAL FIELD The present disclosure relates to image coding technology, and more specifically, to a method and apparatus for coding an intra prediction mode in an image coding system. BACKGROUND Recently, the demand for high resolution, high quality image/video such as 4K, 8K or more Ultra High Definition (UHD) video/image is increasing in various fields. As the video/image resolution or quality becomes higher, relatively more amount of information or bits are transmitted than for conventional video/image data. Therefore, if video/image data are transmitted via a medium such as an existing wired/wireless broadband line or stored in a legacy storage medium, costs for transmission and storage are readily increased. Moreover, interests and demand are growing for virtual reality (VR) and artificial reality (AR) contents, and immersive media such as hologram; and broadcasting of images/videos exhibiting image/video characteristics different from those of an actual video/image, such as game images/videos, are also growing. Therefore, a highly efficient image compression technique is required to effectively compress and transmit, store, or play high resolution, high quality video/image showing various characteristics as described above. SUMMARY According to an embodiment of the present disclosure, an image decoding method performed by a decoding apparatus is provided. The method comprises receiving a bitstream including prediction related information, constructing a Most Probable Modes (MPM) list including intra prediction mode candidates for a current block based on neighboring blocks of the current block, decoding remaining mode information related to remaining intra prediction modes other than the intra prediction mode candidates included in the MPM list from the bitstream, deriving an intra prediction mode of the current block based on the remaining mode information, generating prediction samples for the current block based on the intra prediction mode of the current block, and generating reconstructed samples for the current block based on the prediction samples for the current block, wherein based on a case where a Decoder Side Intra Mode Derivation (DIMD) mode or a Template based Intra Mode Derivation (TIMD) mode is derived from the current block, a plurality of intra prediction modes are derived based on the remaining mode information, wherein one intra prediction mode is selected from among the plurality of intra prediction modes, and wherein the selected intra prediction mode is used as the intra prediction mode of the current block. According to another embodiment of the present disclosure, an image encoding method performed by an encoding apparatus is provided. The method comprises constructing a Most Probable Modes (MPM) list including intra prediction mode candidates for a current block based on neighboring blocks of the current block, generating remaining mode information related to remaining intra prediction modes other than the intra prediction mode candidates included in the MPM list, and encoding image information including the remaining mode information, wherein based on a case where a Decoder Side Intra Mode Derivation (DIMD) mode or a Template based Intra Mode Derivation (TIMD) mode is derived from the current block, the remaining mode information represents a plurality of intra prediction modes, wherein one intra prediction mode is selected from among the plurality of intra prediction modes, and wherein the selected intra prediction mode is used as the intra prediction mode of the current block. According to another embodiment of the present disclosure, a computer-readable digital storage medium is provided. The digital storage medium stores a bitstream generated by a specific method, wherein the specific method comprises constructing a Most Probable Modes (MPM) list including intra prediction mode candidates for a current block based on neighboring blocks of the current block, generating remaining mode information related to remaining intra prediction modes other than the intra prediction mode candidates included in the MPM list, and encoding image information including the remaining mode information, wherein based on a case where a Decoder Side Intra Mode Derivation (DIMD) mode or a Template based Intra Mode Derivation (TIMD) mode is derived from the current block, the remaining mode information represents a plurality of intra prediction modes, wherein one intra prediction mode is selected from among the plurality of intra prediction modes, and wherein the selected intra prediction mode is used as the intra prediction mode of the current block. Accord