US-12627815-B2 - Video coding method and device which use sub-block unit intra prediction

US12627815B2US 12627815 B2US12627815 B2US 12627815B2US-12627815-B2

Abstract

The present invention relates to an intra prediction scheme among video coding techniques and, more particularly, relates to a video decoding method and apparatus for diving a block into a plurality of sub-blocks when intra prediction is performed and sequentially performing infra prediction on each of the sub-blocks. The decoding method performed by a video decoding apparatus includes determining whether to perform sub-block-based intra prediction on a current coding unit, dividing the current coding unit into a plurality of sub-blocks, performing intra prediction on each of the sub-blocks when a result of determination of whether to perform sub-block-based intra prediction has a value of “true”, and directly performing block-based intra prediction on the current coding unit without dividing the current coding unit when the result of the determination has a value of “false”.

Inventors

Yong Jo AHN
Ho Chan RYU

Assignees

KONINKLIJKE PHILIPS N.V.

Dates

Publication Date: 20260512
Application Date: 20240828
Priority Date: 20171229

Claims (11)

1 . An image decoding method performed by an image decoding apparatus, comprising: determining whether to perform block-based intra prediction or sub-block-based intra prediction on a current block; and reconstructing the current block by performing intra prediction on the current block based on the block-based intra prediction or the sub-block-based intra prediction, wherein the intra prediction is performed based on reference samples adjacent to the current block, wherein, in response to the sub-block-based intra prediction, the intra prediction is performed on each of sub-blocks resulting from dividing the current block in at least one of a vertical direction or a horizontal direction, wherein, in response to the size of the current block being 8×4, a number of the sub-blocks resulting from dividing the current block is N, wherein, in response to the size of the current block being 16×4, the number of the sub-blocks resulting from dividing the current block is 2N, and wherein N is representative of a multiple of 2.
2 . The method according to claim 1 , wherein the sub-block-based intra prediction is performed based on the size of the current block being less that or equal to a size of a maximum unit that allows the sub-block-based intra prediction.
3 . The method according to claim 2 , wherein, in response to the size of the current block being 8×4, a width of the current block is divided by 2 to obtain the sub-blocks having a width equal to 4, and wherein, in response to the size of the current block being 16×4, the width of the current block is divided by 4 to obtain the sub-blocks having a width equal to 4.
4 . The method according to claim 3 , wherein the intra prediction on the each of sub-blocks is sequentially performed according to a predetermined order.
5 . The method according to claim 1 , wherein reference samples for the block-based intra prediction are defined based on a width and a height of the current block, and wherein reference samples for the sub-block-based intra prediction are defined based on a width and a height of a sub-block included in the current block.
6 . The method according to claim 1 , wherein the current block is obtained by dividing a coding block according to a multi-type partitioning, the multi-type partitioning including at least one of a binary partitioning or a triple partitioning.
7 . The method according to claim 6 , wherein the triple-tree partitioning is a block partitioning structure of dividing one coding block into three coding blocks based on two split lines.
8 . The method according to claim 7 , wherein the two split lines cross a center position of the one coding block, wherein a size of one of the three coding blocks is greater than a size of the other two of the three coding blocks, and wherein the other two of the three coding blocks have the same size.
9 . The method of claim 8 , wherein the size of the one of the three coding blocks is twice the size of the other two of the three coding blocks.
10 . An image encoding method performed by an image encoding apparatus, comprising: determining whether to perform block-based intra prediction or sub-block-based intra prediction on a current block; and encoding the current block by performing intra prediction on the current block based on the block-based intra prediction or the sub-block-based intra prediction, wherein the intra prediction is performed based on reference samples adjacent to the the current block, wherein, in response to the sub-block-based intra prediction, the intra prediction is performed on each of sub-blocks resulting from dividing the current block in at least one of a vertical direction or a horizontal direction, wherein, in response to the size of the current block being 8×4, a number of the sub-blocks resulting from dividing the current block is N, wherein, in response to the size of the current block being 16×4, the number of the sub-blocks resulting from dividing the current block is 2N, and wherein Nis representative of a multiple of 2.
11 . A transmission method of a video signal, comprising: determining whether to perform block-based intra prediction or sub-block-based intra prediction on a current block; encoding the current block by performing intra prediction on the current block based on the block-based intra prediction or the sub-block-based intra prediction; generating a bitstream including the encoded current block; and transmitting the bitstream associated with the video signal, wherein the intra prediction is performed based on reference samples adjacent to the the current block, wherein, in response to the sub-block-based intra prediction, the intra prediction is performed on each of sub-blocks resulting from dividing the current block in at least one of a vertical direction or a horizontal direction, wherein, in response to the size of the current block being 8×4, a number of the sub-blocks resulting from dividing the current block is N, wherein, in response to the size of the current block being 16×4, the number of the sub-blocks resulting from dividing the current block is 2N, and wherein Nis representative of a multiple of 2.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This is a Continuation of U.S. application Ser. No. 18/462,673 filed Sep. 7, 2023, which is a Continuation of U.S. application Ser. No. 17/570,727 filed Jan. 7, 2022, which is a continuation of U.S. application Ser. No. 16/957,933 filed Jun. 25, 2020, which is a U.S. National Stage Application of International Application No. PCT/KR2018/016823, filed on Dec. 28, 2018, which claims the benefit under 35 USC 119(a) and 365(b) of Korean Patent Application No. 10-2017-0183880, filed on Dec. 29, 2017, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. TECHNICAL FIELD The present invention relates to an image processing scheme and, more particularly, to a video compression technology using sub-block-based intra prediction. BACKGROUND ART Recently, as the demand for high-resolution and high-definition video increases, a high-efficiency video compression technology for next-generation video services is required. To meet this need, ISO/IEC MPEG and ITU-T VCEG, which had jointly standardized H.264/AVC and HEVC video compression standards, organized a joint video exploration team (JVET) in October 2015. The JVET has been conducting research and exploration to establish a new video compression standard since then. In video compression technology, a block partition structure refers to the basic unit for image coding and decoding and also refers to the basic unit for principle coding and decoding techniques such as prediction and transform. As the video compression technology advances, the unit size of blocks used for coding and decoding have increased, and more various types of block partition structures have been used for coding and decoding. While blocks are used as units of coding and decoding, finer units than blocks are also used for video compression depending on functions of blocks. In the HEVC standard, video coding and decoding allow sub-block-based processing as well as block-based processing, depending on a quadtree block partition structure of a coding unit and on whether a coding unit is used for coding/decoding, prediction, or transform. In addition to the quadtree block partition structure, various block partition structures (for example, a quad tree plus binary tree (QTBT), which is a combination of a quadtree and a binary tree, and a multi-type tree (MTT), which is a combination of QTBT and a triple tree) have been proposed to improve video coding efficiency. Since various block sizes and various block partition structures are supported, and various coding unit-based information such as coding mode, motion information, and intra prediction direction information for each block within a picture are used, the number of bits used to express the information is greatly increasing. Intra prediction scheme of video compression technology is a technique of performing prediction on a current block to be coded or decoded using pixels spatially adjacent to the current block. The intra prediction includes generation of prediction pixels using pixels spatially adjacent to a current block in various prediction directions and determination of an optimum intra prediction mode. Research on technology for increasing directionality of intra prediction modes or generating prediction mode candidates from which an optimum intra prediction mode is selected has been being conducted to improve coding efficiency of intra prediction. Specifically, regarding intra prediction performed in a video coding method and apparatus using various block partitioning structures, research on techniques for performing intra prediction in different modes depending on block partitioning methods and block sizes is being conducted. DISCLOSURE Technical Problem An objective of the present invention is to provide a video coding method and apparatus. When performing intra prediction on a target block to be coded or decoded, in a case where the target block is large or has a rectangular shape, spatial similarity between pixels is likely to occur during some modes of intra prediction. The method and apparatus can solve this problem and improves coding efficiency. However, technical problems to be solved by the present embodiment are not limited to the one as described above, and other technical problems can be solved by the present invention. Technical Solution In order to accomplish the objective, according to one aspect of the present invention, a video coding method and apparatus include: determining whether to perform sub-block-based intra prediction on a current coding unit; performing sub-block-based intra prediction on the current coding unit when a result of the determining is a value of “true”; and performing block-based intra prediction on the current coding unit when the result of the determining is a value of “false”. In order to accomplish the objective, according to one aspect of the present invention, a video coding method a