US-12621430-B2 - Method and apparatus for encoding/decoding in-screen prediction mode

US12621430B2US 12621430 B2US12621430 B2US 12621430B2US-12621430-B2

Abstract

Provided are method and apparatus methods and apparatuses for encoding an intra-prediction mode based on a secondary IPM. The present invention may comprises a first decision step of determining whether an intra-prediction mode of a current block is included in a first candidate mode set including M candidate modes (M is an integer equal to or greater than 1); a second decision step of determining whether the intra-prediction mode of the current block is included in a second candidate mode set including N candidate modes (N is an integer equal to or greater than 1) based on a first determination result representing a determination result of the first decision step; and an intra prediction mode encoding step of encoding the intra-prediction mode of the current block based on the first determination result or a second determination result representing a determination result of the second decision step.

Inventors

Dong San Jun
Jung Won Kang
Sung Chang LIM
Hyun Suk KO
Jin Ho Lee
Hui Yong KIM
Jin Soo Choi

Assignees

LX SEMICON CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20240722
Priority Date: 20151119

Claims (6)

1 . An image decoding method performed by an image decoding apparatus, the method comprising: decoding flag information indicating that an intra prediction mode of a current block is in a candidate mode set; decoding index information indicating the intra prediction mode of the current block from among candidate modes in the candidate mode set; deriving the intra prediction mode of the current block based on the index information; and generating a predicted block of the current block based on the intra prediction mode of the current block, wherein the candidate mode set includes a candidate mode derived based on an intra prediction mode of a left block adjacent to the current block and an intra prediction mode of an upper block adjacent to the current block, wherein based on a case that (i) the intra prediction mode of the left block is equal to the intra prediction mode of the upper block and (ii) the intra prediction mode of the left block is a planar mode or a DC mode, the candidate mode set includes a candidate mode for a mode number corresponding to a mode number 50 of a vertical mode plus 4 and a candidate mode for a mode number corresponding to a mode number 50 of the vertical mode minus 4.
2 . The method of claim 1 , wherein the index information is configured by up to 4 bits.
3 . An image encoding method performed by an image encoding apparatus, the method comprising: determining an intra prediction mode of a current block; encoding flag information indicating that the intra prediction mode of the current block is in a candidate mode set; and encoding index information indicating the intra prediction mode of the current block from among candidate modes in the candidate mode set; wherein the candidate mode set includes a candidate mode derived based on an intra prediction mode of a left block adjacent to the current block and an intra prediction mode of an upper block adjacent to the current block, wherein based on a case that (i) the intra prediction mode of the left block is equal to the intra prediction mode of the upper block and (ii) the intra prediction mode of the left block is a planar mode or a DC mode, the candidate mode set includes a candidate mode for a mode number corresponding to a mode number 50 of a vertical mode plus 4 and a candidate mode for a mode number corresponding to a mode number 50 of the vertical mode minus 4.
4 . The method of claim 3 , wherein the index information is configured by up to 4 bits.
5 . A transmission method for image data, the method comprising: obtaining a bitstream generated by an image encoding method, wherein the image encoding method comprises determining an intra prediction mode of a current block, encoding flag information indicating that the intra prediction mode of the current block is in a candidate mode set, and encoding index information indicating the intra prediction mode of the current block from among candidate modes in the candidate mode set; and transmitting the image data comprising the bitstream, wherein the candidate mode set includes a candidate mode derived based on an intra prediction mode of a left block adjacent to the current block and an intra prediction mode of an upper block adjacent to the current block, wherein based on a case that (i) the intra prediction mode of the left block is equal to the intra prediction mode of the upper block and (ii) the intra prediction mode of the left block is a planar mode or a DC mode, the candidate mode set includes a candidate mode for a mode number corresponding to a mode number 50 of a vertical mode plus 4 and a candidate mode for a mode number corresponding to a mode number 50 of the vertical mode minus 4.
6 . The method of claim 5 , wherein the index information is configured by up to 4 bits.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of application Ser. No. 18/296,344 filed Apr. 5, 2023 (now U.S. Pat. No. 12,088,785 issued on Sep. 10, 2024), which is a continuation of application Ser. No. 17/886,154 filed on Aug. 11, 2022 (now U.S. Pat. No. 12,069,237 issued on Aug. 20, 2024), which is a continuation of application Ser. No. 15/772,284 filed on Apr. 30, 2018 (now U.S. Pat. No. 11,451,767 issued on Sep. 20, 2022), which is a U.S. National Stage Application of International Application No. PCT/KR2016/013363, filed on Nov. 18, 2016, which claims the benefit under 35 USC 119(a) and 365(b) of Korean Patent Application No. 10-2015-0162747, filed on Nov. 19, 2015, and Korean Patent Application No. 10-2016-0089419, filed on Jul. 14, 2016 in the Korean Intellectual Property Office. TECHNICAL FIELD The present invention relates generally to a method and apparatus for encoding/decoding for signaling an intra prediction mode in an image encoding/decoding. BACKGROUND ART As broadcasting having High Definition (HD) resolution broadcasting is extended and provided nationwide and worldwide, many users have become accustomed to images having high resolution and high picture quality. Accordingly, many institutions are providing an impetus for the development of the next generation image devices. Furthermore, as there is a growing interest in Ultra High Definition (UHD), which has a resolution for times higher than HDTV, there is a need for technology in which an image having higher resolution and higher picture quality can be compressed and processed. As an image compression technology, there are various technologies such as an inter-prediction technology in which pixel values included in a current picture are predicted from pictures before or after the current picture, an intra-prediction technology in which pixel values included in a current picture are predicted using pixel information in the current picture, a transformation and quantization technology for compressing energy of residual signals, and an entropy encoding technology in which a short code is allocated to a value having high appearance frequency and a long code is allocated to a value having low appearance frequency. The image data may be transmitted and stored in a state in which it is effectively compressed using these image compression technologies. In order to transmit all information generated while encoding/decoding, an amount of bits required to be transmitted may be increased. In particular, while encoding a slice in an intra mode in a low bit rate environment, the amount of bits for intra prediction mode is predicted to occupy a large portion of the total amount of bits, so an improvement plan is required. DISCLOSURE Technical Problem The present invention is intended to propose a method and apparatus for efficiently encoding/decoding an image. In addition, the present invention provides a method and apparatus for efficiently encoding/decoding an intra-prediction mode. In addition, the present invention provides a method and apparatus for reducing an amount of bits required for a transmission of an intra-prediction mode. In addition, the present invention provides a method and apparatus for reducing an amount of bits generated for transmitting intra-prediction modes when an intra-prediction mode of a current encoding block is determined through a rate-distortion optimization process as the number of the intra-prediction modes is increased. Technical Solution According to one aspect of the present invention, there is provided a method for encoding an image, the method including: a first decision step of determining whether an intra-prediction mode of a current block is included in a first candidate mode set including M candidate modes (M is an integer equal to or greater than 1); a second decision step of determining whether the intra-prediction mode of the current block is included in a second candidate mode set including N candidate modes (N is an integer equal to or greater than 1) based on a first determination result representing a determination result of the first decision step; and an intra prediction mode encoding step of encoding the intra-prediction mode of the current block based on the first determination result or a second determination result representing a determination result of the second decision step. According to the encoding method of the present invention, when the intra-prediction mode of the current block is determined to be included in the first candidate mode set at the first decision step, the intra prediction mode encoding step may encode result information about the first determination result and first indication information for indicating a candidate mode which is the same as the intra-prediction mode of the current block among the M candidate modes included in the first candidate mode set. According to the encoding method of the present invention, when the intra-prediction mode