# US 2021/0344907 A1 · Image coding method and device for carrying out mrl-based intra prediction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0344907 A1 - Document ID: US20210344907A1 - Status: Published application - Kind: A1 - Application number: 17/374,274 - Filed: 2021-07-13 - Published: 2021-11-04 - Earliest claimed: 2019-01-13 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Jin HEO; Sunmi YOO; Ling LI; Jangwon CHOI; Jungah CHOI - Web page: https://patentgrep.com/patent/US20210344907A1 ## CPC - H04N 19/105: Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction - H04N 19/11: among a plurality of spatial predictive coding modes - H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction - H04N 19/176: the region being a block, e.g. a macroblock - H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards - H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks - H04N 19/593: involving spatial prediction techniques - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An image decoding method includes: configuring a MPM list including candidate intra prediction modes for a current block; deriving an intra prediction mode of the current block from the MPM list on the basis of MPM index information indicating an intra prediction mode, among the candidate intra prediction modes included in the MPM list, for the current block; generating prediction samples for the current block on the basis of the intra prediction mode; and generating a reconstructed picture for the current block on the basis of the prediction samples, wherein the step for configuring the MPM list comprises, on the basis of the case where the value of reference line index information, representing a reference line used for the intra prediction of the current block, is not zero, deriving a DC mode as one mode among the candidate intra prediction modes, and including same in the MPM list. ## Claims ### Claim 1 An image decoding method performed by a decoding apparatus, the method comprising: constructing a Most Probable Mode (MPM) list including candidate intra prediction modes for a current block; deriving an intra prediction mode of the current block from the MPM list based on MPM index information indicating an intra prediction mode for the current block among the candidate intra prediction modes included in the MPM list; generating prediction samples for the current block based on the intra prediction mode; and generating a reconstructed picture based on the prediction samples, wherein the constructing of the MPM list includes deriving a DC mode as one of the candidate intra prediction modes to include the DC mode in the MPM list, based on a case in which a value of reference line index information indicating a reference line used for intra prediction of the current block is not equal to 0. ### Claim 2 (depends on 1) The method of claim 1, wherein the constructing of the MPM list includes the DC mode on the last order of the MPM list. ### Claim 3 (depends on 1) The method of claim 1, wherein the constructing of the MPM list includes the DC mode on the first order of the MPM list. ### Claim 4 (depends on 1) The method of claim 1, wherein based on a value of the reference line index information being not 0, MPM flag information indicating whether an intra prediction mode of the current block is selected among MPM candidate intra prediction modes is not signaled, and a value of the MPM flag information is derived as 1. ### Claim 5 (depends on 4) The method of claim 4, wherein based on a value of the reference line index information being not 0, and a value of the MPM flag information is derived as 1, the MPM index information is signaled. ### Claim 6 (depends on 1) The method of claim 1, wherein the deriving of the intra prediction mode of the current block derives the DC mode as the intra prediction mode of the current block based on the MPM index information indicating the DC mode among the candidate intra prediction modes included in the MPM list. ### Claim 7 (depends on 6) The method of claim 6, wherein the generating of the prediction samples of the current block comprises: calculating a DC value for the current block by using specific neighboring samples among neighboring samples of the current block, wherein the neighboring samples includes left neighboring samples and top neighboring samples of the current block; and deriving the prediction samples based on the DC value, wherein the specific neighboring samples are determined based on whether the current block is a square block or a non-square block, wherein based on the current block being the square block, the specific neighboring samples used for calculating the DC value includes both the left neighboring samples of the current block and the top neighboring samples of the current block, wherein based on the current block being the non-square block and a width of the current block being greater than a height of the current block, the specific neighboring samples includes used for calculating the DC value includes the top neighboring samples of the current block and do not include the left neighboring samples of the current block, and wherein based on the current block being the non-square block and the width of the current block being less than the height of the current block, the specific neighboring samples used for calculating the DC value includes the left neighboring samples of the current block and do not include the top neighboring samples of the current block. ### Claim 8 (depends on 7) The method of claim 7, wherein based on the current block being the non-square block and the width of the current block being greater than the height of the current block, a number of the top neighboring samples used for calculating the DC value is the same as the width of the current block, and based on the current block being the non-square block and the width of the current block being less than the height of the current block, a number of the left neighboring samples used for calculating the DC value is the same as the height of the current block. ### Claim 9 (depends on 7) The method of claim 7, wherein based on the current block being the non-square block and the width of the current block being greater than the height of the current block, a number of the top neighboring samples used for calculating the DC value is the same as a number of the left neighboring samples, and based on the current block being the non-square block and the width of the current block is less than the height of the current block, a number of the left neighboring samples used for calculating the DC value is the same as a number of the top neighboring samples. ### Claim 10 (depends on 9) The method of claim 9, wherein based on the current block being the non-square block and the width of the current block being greater than the height of the current block, the top neighboring samples used for calculating the DC value include odd-numbered samples or even-numbered samples. ### Claim 11 An image encoding method performed by an encoding apparatus, the method comprising: constructing a Most Probable Mode (MPM) list including candidate intra prediction modes for a current block; deriving an intra prediction mode of the current block based on the candidate intra prediction modes included in the MPM list; generating MPM index information indicating an intra prediction mode of the current block among the candidate intra prediction modes included in the MPM list; and encoding image information including at least one of reference line index information indicating a reference line used for intra prediction of the current block or the MPM index information, wherein the constructing the MPM list includes deriving a DC mode as one of the candidate intra prediction modes to include the DC mode in the MPM list, based on a case in which a value of the reference line index information is not equal to 0. ### Claim 12 (depends on 11) The method of claim 11, wherein the constructing of the MPM list includes the DC mode on the last order of the MPM list. ### Claim 13 (depends on 11) The method of claim 11, wherein the constructing of the MPM list includes the DC mode on the first order of the MPM list. ### Claim 14 (depends on 11) The method of claim 11, wherein based on a value of the reference line index information being not 0, MPM flag information indicating whether an intra prediction mode of the current block is selected among MPM candidate intra prediction modes is not signaled, and a value of the MPM flag information is derived as 1. ### Claim 15 (depends on 14) The method of claim 14, wherein, based on a value of the reference line index information being not 0, and a value of the MPM flag information is derived as 1, the MPM index information is signaled. ### Claim 16 (depends on 11) The method of claim 11, wherein based on an intra prediction mode of the current block being derived as the DC mode included in the MPM list, the MPM index information is generated as an index value indicating the DC mode among the candidate intra prediction modes included in the MPM list. ### Claim 17 (depends on 16) The method of claim 16, further comprising: based on the DC mode being applied to the current block, calculating a DC value for the current block by using specific neighboring samples among neighboring samples of the current block, wherein the neighboring samples includes left neighboring samples and top neighboring samples of the current block; and deriving the prediction samples based on the DC value, wherein the specific neighboring samples are determined based on whether the current block is a square block or a non-square block, wherein based on the current block being the square block, the specific neighboring samples used for calculating the DC value includes both the left neighboring samples of the current block and the top neighboring samples of the current block, wherein based on the current block being the non-square block and a width of the current block being greater than a height of the current block, the specific neighboring samples includes used for calculating the DC value includes the top neighboring samples of the current block and do not include the left neighboring samples of the current block, and wherein based on the current block being the non-square block and the width of the current block being less than the height of the current block, the specific neighboring samples used for calculating the DC value includes the left neighboring samples of the current block and do not include the top neighboring samples of the current block. ### Claim 18 (depends on 17) The method of claim 17, wherein based on the current block being the non-square block and the width of the current block being greater than the height of the current block, a number of the top neighboring samples used for calculating the DC value is the same as the width of the current block, and based on the current block being the non-square block and the width of the current block being less than the height of the current block, a number of the left neighboring samples used for calculating the DC value is the same as the height of the current block. ### Claim 19 (depends on 17) The method of claim 17, wherein based on the current block being the non-square block and the width of the current block being greater than the height of the current block, a number of the top neighboring samples used for calculating the DC value is the same as a number of the left neighboring samples, and based on the current block being the non-square block and the width of the current block is less than the height of the current block, a number of the left neighboring samples used for calculating the DC value is the same as a number of the top neighboring samples. ### Claim 20 A non-transitory computer-readable digital storage medium storing a bitstream generated by a method, the method comprising: constructing a Most Probable Mode (MPM) list including candidate intra prediction modes for a current block; deriving an intra prediction mode of the current block based on the candidate intra prediction modes included in the MPM list; generating MPM index information indicating an intra prediction mode of the current block among the candidate intra prediction modes included in the MPM list; and encoding image information including at least one of reference line index information indicating a reference line used for intra prediction of the current block or the MPM index information, wherein the constructing the MPM list includes deriving a DC mode as one of the candidate intra prediction modes to include the DC mode in the MPM list, based on a case in which a value of the reference line index information is not equal to 0.