US-12621436-B2 - Intra prediction-based video encoding/decoding method and device

US12621436B2US 12621436 B2US12621436 B2US 12621436B2US-12621436-B2

Abstract

A video encoding/decoding method and device according to the present invention may: determine a reference area for the intra prediction of the current block; derive the intra prediction mode of the current block; and decode the current block on the basis of the reference area and the intra prediction mode.

Inventors

Ki Baek Kim

Assignees

B1 INSTITUTE OF IMAGE TECHNOLOGY, INC.

Dates

Publication Date: 20260505
Application Date: 20240905
Priority Date: 20181228

Claims (8)

1 . A method of decoding an image based on an intra prediction with a decoding apparatus, comprising: determining an intra prediction mode of a current chroma block; and predicting the current chroma block based on the intra prediction mode of the current chroma block, wherein determining an intra prediction mode of the current chroma block comprises: selecting one of a first mode group and a second mode group based on a first flag signaled from the encoding apparatus, the first mode group including only inter-components reference-based prediction modes, the second mode group including 67 intra prediction modes pre-defined in the decoding apparatus, the 67 intra prediction modes being composed of 2 non-directional modes and 65 directional modes, and the first flag specifying whether the intra prediction mode of the chroma block belongs to the first mode group or the second mode group; and deriving the intra prediction mode of the current chroma block from the selected mode group, wherein the current chroma block is predicted by a current luma block that is corresponding to the current chroma block, when the intra prediction mode of the current chroma block is derived from the first mode group, to predict the current chroma block based on the current luma block, the method further comprising: determining a predetermined number of sample locations of luma neighboring samples of the current luma block and chroma neighboring samples of the current chroma block; determining the neighboring sample pairs at the sample locations; determining the correlation parameters based on the neighboring sample pairs; and predicting the current chroma block based on the current luma block and the correlation parameters.
2 . The method of claim 1 , wherein in response to the selection that the intra prediction mode of the current chroma block is derived from the second mode group, the intra prediction mode of the current chroma block is determined based on an intra prediction mode of a current luma block corresponding to the current chroma block.
3 . The method of claim 2 , wherein when the intra prediction mode of the luma block is unavailable, the intra prediction mode of the current luma block is set equal to an intra prediction mode pre-defined in the decoding apparatus.
4 . The method of claim 2 , wherein a reference pixel line for the current luma block is determined based on index information signaled from the encoding apparatus and a plurality of reference pixel line candidates, wherein the index information specifies one of the plurality of reference pixel line candidates, and wherein the plurality of reference pixel line candidates include at least one of a first pixel line adjacent to the current luma block, a second pixel line adjacent to the first pixel line, or a third pixel line adjacent to the second pixel line.
5 . The method of claim 4 , wherein determining an intra prediction mode of the current luma block comprises: selecting one of a first MPM candidate group and a second MPM candidate group based on a second flag signaled from an encoding apparatus, the first MPM candidate group including only at least one non-directional mode, the second candidate group including only a plurality of MPM candidates of directional modes, and the second flag specifying whether the intra prediction mode of the current luma block belongs to the first MPM candidate group or the second MPM candidate group; and deriving the intra prediction mode of the current luma block from the selected one.
6 . The method of claim 5 , wherein when the intra prediction mode of the current luma block is derived from the first MPM candidate group, the current luma block is predicted using only the first pixel line adjacent to the current luma block.
7 . A method of encoding an image based on an intra prediction with an encoding apparatus, comprising: determining an intra prediction mode of a current chroma block; and predicting the current chroma block based on the intra prediction mode of the current chroma block, wherein the intra prediction mode of the current chroma block belongs to one of a first mode group and a second mode group, the first mode group including only inter-components reference-based prediction modes, the second mode group including 67 intra prediction modes pre-defined in the encoding apparatus, the 67 intra prediction modes being composed of 2 non-directional modes and 65 directional modes, wherein a first flag for specifying whether the intra prediction mode of the current chroma block belongs to the first mode group or the second mode group is encoded and is included in the bitstream, and wherein the current chroma block is predicted by a current luma block that is corresponding to the current chroma block, when the intra prediction mode of the current chroma block is derived from the first mode group, to predict the current chroma block based on the current luma block, the method further comprising: determining a predetermined number of sample locations of luma neighboring samples of the current luma block and chroma neighboring samples of the current chroma block; determining the neighboring sample pairs at the sample locations; determining the correlation parameters based on the neighboring sample pairs; and predicting the current chroma block based on the current luma block and the correlation parameters.
8 . A non-transitory computer-readable storage medium storing a bitstream that is encoded by an image encoding method, the image encoding method comprising: determining an intra prediction mode of a current chroma block; and predicting the current chroma block based on the intra prediction mode of the current chroma block, wherein the intra prediction mode of the current chroma block belongs to one of a first mode group and a second mode group, the first mode group including only inter-components reference-based prediction modes, the second mode group including 67 intra prediction modes pre-defined in the encoding apparatus, the 67 intra prediction modes being composed of 2 non-directional modes and 65 directional modes, wherein a first flag for specifying whether the intra prediction mode of the current chroma block belongs to the first mode group or the second mode group is encoded and is included in the bitstream, and wherein the current chroma block is predicted by a current luma block that is corresponding to the current chroma block, when the intra prediction mode of the current chroma block is derived from the first mode group, wherein the second mode group comprises a DO mode, a planar mode, a vertical mode, and a horizontal mode, and wherein the second mode group comprises an intra prediction mode of a current luma block that is corresponding to the current chroma block, to predict the current chroma block based on the current luma block, the method further comprising: determining a predetermined number of sample locations of luma neighboring samples of the current luma block and chroma neighboring samples of the current chroma block; determining the neighboring sample pairs at the sample locations; determining the correlation parameters based on the neighboring sample pairs; and predicting the current chroma block based on the current luma block and the correlation parameters.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This Application is a continuation of U.S. patent application Ser. No. 18/310,013 filed on May 1, 2023, which is a continuation of U.S. patent application Ser. No. 17/165,075 filed on Feb. 2, 2021, now U.S. Pat. No. 11,677,933, which is a continuation of U.S. patent application Ser. No. 17/079,784 filed on Oct. 26, 2020, now U.S. Pat. No. 10,951,886, which pursuant to 35 U.S.C. §§ 120 and 365 (c), is a Bypass Continuation of International Application No. PCT/KR2019/018740, filed on Dec. 30, 2019, which claims the benefit under 35 U.S.C. §§ 2018, and Korean Patent Application No. 10-2018-0173228, filed on Dec. 29, 2018 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 a video encoding/decoding method and apparatus. 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 application fields, and accordingly, high-efficiency image compression techniques are being discussed. Various technologies exist, such as the inter prediction technology that predicts pixel values included in a current picture from a picture before or after a current picture using video compression technology, the intra prediction technology that predicts pixel values included in a current picture by using pixel information in a current picture, an entropy encoding technology that allocates a short code to a value with a high frequency of appearance and a long code to a value with a low frequency of appearance. Image data can be effectively compressed by using such image compression technology, and transmitted or stored. DISCLOSURE Technical Problem An object of the present invention is to provide an efficient block division method and apparatus. An object of the present invention is to provide a method and an apparatus for deriving an intra prediction mode. An object of the present invention is to provide a method and an apparatus for determining a reference region for intra prediction. An object of the present invention is to provide an intra prediction method and apparatus according to a component type. Technical Solution A method and an apparatus of encoding/decoding an image of the present invention may determine a reference region for intra prediction of a current block, derive an intra prediction mode of the current block, and decode the current block based on the reference region and the intra prediction mode. In the method and apparatus of encoding/decoding the image of the present invention, the intra prediction modes pre-defined in the encoding/decoding apparatus may be divided into an MPM candidate group and a non-MPM candidate group, and the MPM candidate group may include at least one of a first candidate group or a second candidate group. In the method and apparatus of encoding/decoding the image of the present invention, the intra prediction mode of the current block may be derived from either the first candidate group or the second candidate group. In the method and apparatus of encoding/decoding the image of the present invention, the first candidate group may be composed of a default mode pre-defined in the decoding apparatus, and the second candidate group may be composed of a plurality of MPM candidates. In the method and apparatus of encoding/decoding the image of the present invention, the default mode may be at least one of a planar mode, a DC mode, a vertical mode, a horizontal mode, a vertical mode, or a diagonal mode. In the method and apparatus of encoding/decoding the image of the present invention, the plurality of MPM candidates may include at least one of an intra prediction mode of a neighboring block, a mode obtained by subtracting n value from the intra prediction mode of the neighboring block, or a mode obtained by adding n value to the intra prediction mode of the neighboring block. Herein, n may mean a natural number of 1, 2, or more. In the method and apparatus of encoding/decoding the image of the present invention, the plurality of MPM candidates may include at least one of a DC mode, a vertical mode, a horizontal mode, a mode obtained by subtracting or adding m value to the vertical mode, or a mode obtained by subtracting or adding m value to the horizontal mode. Herein, m may be a natural number of 1, 2, 3, 4 or more. In the method and apparatus of encoding/decoding the image of the present invention, the encoding apparatus may determine a candidate group to which the intra prediction mode of the current block belongs, encode a flag for identifying the candidate group, and the decoding apparatus may select one of the first candidate group or the second candidate group based on a flag signaled from the encoding apparatus. In the method and apparatus of encoding/decoding the image of the present invention, the derived