TECHNICAL FIELD

The present disclosure relates to a video encoding/decoding method and apparatus.

BACKGROUND ART

As a demand for high-resolution and high-definition video has recently increased, a need for a high-efficiency video compression technology for next-generation video services has emerged. Based on this need, ISO/IEC MPEG and ITU-T VCEG, which jointly standardized H.264/AVC and HEVC video compression standards, formed JVET (Joint Video Exploration Team) and conducted research and exploration to establish a new video compression standard from October 2015. In April 2018, a new video compression standardization was started with an evaluation of a responses to a new video compression standard CfP (Call for Proposal).

In a video compression technique, a block division structure means a unit that performs encoding and decoding, and a unit to which major encoding and decoding techniques such as prediction and transformation are applied. As video compression technology develops, the size of blocks for encoding and decoding is gradually increasing, and more various division types are supported as a block division type. In addition, video compression is performed using not only units for encoding and decoding, but also units subdivided according to the role of blocks.

In the HEVC standard, video encoding and decoding are performed using a unit block subdivided according to a quad-tree type block division structure and a role for prediction and transformation. In addition to the quad-tree type block division structure, various types of block division structures such as QTBT (Quad Tree plus Binary Tree) in the form of combining a quad-tree and a binary-tree, and MTT (Multi-Type Tree) in which a triple-tree is combined therewith have been proposed to improve video coding efficiency. Through the support of various block sizes and various types of block division structures, one picture is divided into multiple blocks, and information in units of coding units such as a coding mode, motion information, and intra prediction direction information corresponding to each block is expressed in various ways, so the number of bits expressing this is increasing significantly.

DISCLOSURE

Technical Problem

An image encoding/decoding method and apparatus according to the present disclosure provides a limited bidirectional prediction method.

An image encoding/decoding method and apparatus according to the present disclosure defines various inter modes for improving an efficiency of inter prediction, and provides a method of inducing motion information according to each inter mode.

An image encoding/decoding method and apparatus according to the present disclosure provides a method of adaptively limiting consumption of a memory bandwidth by using a plurality of motion vectors.

An image encoding/decoding method and apparatus according to the present disclosure provides a hierarchical division method of a picture.

Technical Solution

An image encoding/decoding method and apparatus according to the present disclosure may derive motion information for bidirectional prediction of a current block, based on an inter mode pre-defined in an image decoding apparatus, and perform inter prediction on the current block based on the motion information.

In the image encoding/decoding method and apparatus according to the present disclosure, according to the pre-defined inter mode, the motion information for the bidirectional prediction may be adjusted to motion information for unidirectional prediction.

In the image encoding/decoding method and apparatus according to the present disclosure, when the pre-defined inter mode is a merge mode, the motion information for the bidirectional prediction may be adjusted to motion information for unidirectional prediction, and when the pre-defined inter mode is an affine mode, the motion information for the bidirectional prediction may be not adjusted to motion information for unidirectional prediction.

In the image encoding/decoding method and apparatus according to the present disclosure, when the pre-defined inter mode is a merge mode, the motion information for the bidirectional prediction may be adjusted to motion information for unidirectional prediction in consideration of a size of the current block.

In the image encoding/decoding method and apparatus according to the present disclosure, when the pre-defined inter mode is a merge mode, the deriving of the motion information may comprise constructing a merge candidate list of the current block, and deriving motion information of the current block from the merge candidate list.

In the image encoding/decoding method and apparatus according to the present disclosure, the merge candidate list may include at least one of a spatial merge candidate, a temporal merge candidate, or a combined merge candidate.

In the image encoding/decoding method and apparatus according to the present disclosure, when the pre-defined inter mode is an affine mode, the deriving of the motion information may comprise generating a candidate list consisting of affine candidates of the current block, deriving a control point vector of the current block based on the candidate list and a candidate index, and deriving a motion vector of the current block based on the control point vector of the current block.

In the image encoding/decoding method and apparatus according to the present disclosure, the affine candidates may include at least one of a spatial candidate, a temporal candidate, or a configured candidate.

In the image encoding/decoding method and apparatus according to the present disclosure, in consideration of a size of a predetermined reference region, a motion vector of the current block is derived, and the reference region includes a reference block specified by motion vectors of n sub-blocks and a pixel used to interpolate a fractional pel of the reference block.

In the image encoding/decoding method and apparatus according to the present disclosure, when the size of the reference region is less than or equal to a threshold value, the motion vector of the current block may be derived for each sub-block, and when the size of the reference region is greater than the threshold value, one motion vector may be derived for the current block.

In the image encoding/decoding method and apparatus according to the present disclosure, the motion vector of the current block may be derived based on an affine motion parameter, and the affine motion parameter may be calculated based on the control point vector of the current block.

In the image encoding/decoding method and apparatus according to the present disclosure, the current block may belong to a predetermined sub-picture, and the sub-picture may be defined as a group of grids having the same index among a plurality of grids constituting one picture.

Advantageous Effects

The present disclose may allow bidirectional prediction only when a predetermined condition is satisfied, or may reduce the consumption of a memory bandwidth by adjusting a motion vector.

According to the present disclosure, an efficiency of inter prediction may be improved by using a combined merge candidate in addition to spatial/temporal merge candidates.

According to the present disclosure, an efficiency of image encoding/decoding may be improved through inter prediction based on an affine motion model.

According to the present disclosure, an efficiency of image encoding/decoding may be improved by dividing one picture into multi-level fragment regions.

