Image coding method and device based on geometric partitioning mode (GPM)
A method by which a decoding device decodes an image, according to the disclosure of the present document, comprises the steps of: acquiring, from a bitstream, information related to a geometric partitioning mode (GPM) for the current block; deriving partitions of the current block on the basis of partition index information within the information related to the GPM, wherein the partitions include a first geometric partition and a second geometric partition; deriving first prediction samples for the first geometric partition; deriving second prediction samples for the second geometric partition; generating prediction samples for the current block on the basis of the first prediction samples and the second prediction samples; and generating reconstructed samples on the basis of the prediction samples for the current block.
1 . An image decoding method performed by a decoding apparatus, the image decoding method comprising:
obtaining geometric partitioning mode (GPM) related information for a current block from a bitstream;
deriving partitions of the current block based on partition index information in the GPM related information, wherein the partitions include a first geometric partition and a second geometric partition;
deriving first prediction samples for the first geometric partition;
deriving second prediction samples for the second geometric partition;
generating prediction samples for the current block based on the first prediction samples and the second prediction samples; and
generating reconstructed samples based on the prediction samples for the current block,
wherein the image decoding method further comprises determining whether an intra prediction is allowed to be applied to one of the first geometric partition or the second geometric partition,
wherein the obtaining the GPM related information comprises:
parsing first intra GPM flag information specifying whether the first geometric partition is coded by the intra prediction based on a determination that the intra prediction is allowed to be applied to one of the first geometric partition or the second geometric partition, and
wherein based on a value of the first intra GPM flag information being equal to 1, an inter prediction is applied to the second geometric partition.
2 . The image decoding method of claim 1 , wherein based on the intra prediction being applied to the first geometric partition, the inter prediction is applied to the second geometric partition.
3 . The image decoding method of claim 2 , wherein based on the value of the first intra GPM flag information being equal to 1, second intra GPM flag information specifying whether the second geometric partition is coded by the intra prediction is not parsed.
4 . The image decoding method of claim 1 , wherein the obtaining the GPM related information comprises:
parsing second intra GPM flag information specifying whether the second geometric partition is coded by the intra prediction, based on a value of specific flag information not being equal to 1 and the value of the first intra GPM flag information not being equal to 1,
wherein based on the value of the first intra GPM flag information being equal to 0, and a slice type of a current slice being equal to P slice, the value of the specific flag information is derived as equal to 1, and
wherein based on the value of the first intra GPM flag information being equal to 1, the value of the specific flag information is derived as equal to 0.
5 . The image decoding method of claim 4 , wherein based on the second intra GPM flag information not being parsed,
based on a first case that it is determined that the intra prediction is not allowed to be applied to one of the first geometric partition or the second geometric partition, a value of the second intra GPM flag information is derived as equal to 0,
based on a second case that, other than the first case, the value of the first intra GPM flag information is equal to 1, the value of the second intra GPM flag information is derived as equal to 0,
based on a third case that, other than the first case and the second case, the value of the specific flag information is equal to 1, the value of the second intra GPM flag information is derived as equal to 0, and
based on a case other than the first case, the second case and the third case, the value of the second intra GPM flag information is derived as equal to 0.
6 . The image decoding method of claim 1 , wherein the obtaining the GPM related information comprises:
parsing second intra GPM flag information specifying whether the second geometric partition is coded by the intra prediction, based on a value of specific flag information not being equal to 1 and the value of the first intra GPM flag information not being equal to 1,
wherein based on the value of the first intra GPM flag information being equal to 0, and a maximum number of GPM merge candidates being less than 2, the value of the specific flag information is derived as equal to 1, and
wherein based on the value of the first intra GPM flag information being equal to 1, the value of the specific flag information is derived as equal to 0.
7 . The image decoding method of claim 6 , wherein based on the second intra GPM flag information not being parsed,
based on a first case that it is determined that the intra prediction is not allowed to be applied to one of the first geometric partition or the second geometric partition, a value of the second intra GPM flag information is derived as equal to 0,
based on a second case that, other than the first case, the value of the first intra GPM flag information is equal to 1, the value of the second intra GPM flag information is derived as equal to 0,
based on a third case that, other than the first case and the second case, the value of the specific flag information is equal to 1, the value of the second intra GPM flag information is derived as equal to 0, and
based on a case other than the first case, the second case and the third case, the value of the second intra GPM flag information is derived as equal to 0.
8 . The image decoding method of claim 1 , wherein based on the value of the first intra GPM flag information being equal to 1, the GPM related information includes first merge GPM index information related to a first merge candidate for the GPM.
9 . The image decoding method of claim 1 , wherein based on a value of second intra GPM flag information being equal to 0 and a maximum number of GPM merge candidates being greater than 2, the GPM related information includes second merge GPM index information related to a second merge candidate for the GPM.
10 . The image decoding method of claim 1 , wherein based on the value of the first intra GPM flag information being equal to 1, and a maximum number of GPM merge candidates being greater than 1, the GPM related information includes second merge GPM index information related to a second merge candidate for the GPM.
11 . The image decoding method of claim 1 , wherein as an intra prediction mode for the intra prediction applied to one of the first geometric partition or the second geometric partition, an intra prediction mode derived based on Template based Intra Mode Derivation (TIMD) is used.
12 . The image decoding method of claim 11 , wherein the intra prediction mode derived based on the TIMD is an intra prediction mode of the current block derived based on a template,
wherein the template comprises neighboring samples of the current block, and
wherein the neighboring samples are reconstructed samples.
13 . An image encoding method performed by an encoding apparatus, the image encoding method comprising:
deriving partitions for applying geometric partitioning mode (GPM) for a current block, wherein the partitions include a first geometric partition and a second geometric partition;
deriving first prediction samples for the first geometric partition;
deriving second prediction samples for the second geometric partition;
generating prediction samples for the current block based on the first prediction samples and the second prediction samples;
generating GPM related information for the current block; and
encoding image information including the GPM related information,
wherein the image encoding method further comprises determining whether an intra prediction is allowed to be applied to one of the first geometric partition or the second geometric partition,
wherein based on a determination that the intra prediction is allowed to be applied to one of the first geometric partition or the second geometric partition, the GPM related information includes first intra GPM flag information specifying whether the first geometric partition is coded by the intra prediction, and
wherein based on a value of the first intra GPM flag information being equal to 1, an inter prediction is applied to the second geometric partition.
14 . A non-transitory computer readable digital storage medium storing a bitstream generated by the image encoding method of claim 13 .
15 . A transmission method of data for an image, the transmission method comprising:
obtaining a bitstream, wherein the bitstream is generated based on deriving partitions for applying geometric partitioning mode (GPM) for a current block, wherein the partitions include a first geometric partition and a second geometric partition, deriving first prediction samples for the first geometric partition, deriving second prediction samples for the second geometric partition, generating prediction samples for the current block based on the first prediction samples and the second prediction samples, generating GPM related information for the current block and generating the bitstream by encoding image information including the GPM related information; and
transmitting the data comprising the bitstream,
wherein an intra prediction is applied to one of the first geometric partition or the second geometric partition,
wherein the GPM related information includes first intra GPM flag information specifying whether the first geometric partition is coded by the intra prediction, and
wherein based on a value of the first intra GPM flag information being equal to 1, an inter prediction is applied to the second geometric partition.