EP-4742658-A1 - ENCODING METHOD, ENCODING APPARATUS, DECODING METHOD, AND DECODING APPARATUS FOR IMAGE

EP4742658A1EP 4742658 A1EP4742658 A1EP 4742658A1EP-4742658-A1

Abstract

Provided are an image decoding method, an image decoding apparatus, an image encoding method, and an image encoding apparatus, the image decoding method including: when a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, determining the reference block in the current image including the current block; when all samples of the reference block are reconstructed, reconstructing the current block using the reference block; and when at least some samples of the reference block are not reconstructed, determining the at least some unreconstructed samples using reconstructed samples of the current image; and reconstructing the current block using the reference block including the determined at least some samples.

Inventors

PARK, MINSOO
PARK, MINWOO
PARK, JEEYOON
CHOI, Kwangpyo

Assignees

Samsung Electronics Co., Ltd.

Dates

Publication Date: 20260513
Application Date: 20240527

Claims (15)

An image decoding method comprising: when a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, determining the reference block in the current image including the current block, wherein at least some samples of the reference block are reconstructed; when all samples of the reference block are reconstructed, reconstructing the current block using the reference block; and when at least some samples of the reference block are not reconstructed, determining the at least some unreconstructed samples using reconstructed samples of the current image; and reconstructing the current block using the reference block including the determined at least some samples.
The image decoding method of claim 1, wherein the determining of the reference block comprises: when the prediction mode of the current block is a block copy mode, identifying a block vector indicating the reference block; and determining the reference block using the block vector.
The image decoding method of claim 1, wherein the determining of the reference block comprises: when the current block is in a template matching-based prediction mode, determining a reference template similar to a template of the current block; and determining the reference block based on the reference template.
The image decoding method of claim 1, wherein an upper left sample of the reference block is a reconstructed sample of the current image.
The image decoding method of claim 1, further comprising: identifying a reconstructed region of the current image; when a lower right sample of the reference block is included in the reconstructed region, identifying that all samples of the reference block are reconstructed; and when the lower right sample of the reference block is not included in the reconstructed region, identifying that at least some samples of the reference block are not reconstructed.
The image decoding method of claim 1, wherein the determining of the at least some unreconstructed samples comprises determining the at least some unreconstructed samples using at least one of a reconstructed left sample and a reconstructed upper sample adjacent to the at least some unreconstructed samples.
The image decoding method of claim 6, wherein the determining of the at least some unreconstructed samples comprises determining the at least some unreconstructed samples using a weighted sum of the reconstructed left sample and the reconstructed upper sample adjacent to the at least some unreconstructed samples.
The image decoding method of claim 1, wherein the determining of the at least some unreconstructed samples comprises determining the at least some unreconstructed samples using a bit depth of the current image.
The image decoding method of claim 1, wherein the determining of the at least some unreconstructed samples comprises: determining a reconstructed reference sample adjacent to the at least some unreconstructed samples; and determining the at least some unreconstructed samples by performing intra prediction using the reconstructed reference sample.
The image decoding method of claim 9, wherein the intra prediction is performed using at least one of a DC mode, a planar mode, a most probable mode (MPM) of the current block, an intra prediction mode of reconstructed samples of the reference block, template-based intra mode derivation (TIMD), or decoder side intra mode derivation (DIMD).
The image decoding method of claim 3, further comprising, when there are undetermined samples in the current block after at least a part of the current block is determined based on the reference block, determining the undetermined samples using at least one of template matching or intra prediction.
The image decoding method of claim 1, further comprising: determining a first reference block and a second reference block; and determining the reference block using a weighted sum of the first reference block and the second reference block, wherein, when both a sample of the first reference block and a sample of the second reference block are reconstructed, weights thereof are determined to be same, and when at least one of the sample of the first reference block and the sample of the second reference block is not reconstructed, a weight of the at least one unreconstructed sample is determined to be 0.
The image decoding method of claim 1, wherein the mode for determining the reference block in the current image comprises at least one of an intra block copy mode or a template matching-based intra prediction mode.
An image encoding method comprising: when a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, determining the reference block in the current image including the current block, wherein at least some samples of the current block are reconstructed; when all samples of the reference block are reconstructed, reconstructing the current block using the reference block; and when at least some samples of the reference block are not reconstructed, determining the at least some unreconstructed samples using reconstructed samples of the current image; and reconstructing the current block using the reference block including the determined at least some samples.
A computer-readable storage medium storing a bitstream encoded by an image encoding method, the image encoding method comprising: when a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, determining the reference block in the current image including the current block, wherein at least some samples of the reference block are reconstructed; when all samples of the reference block are reconstructed, reconstructing the current block using the reference block; and when at least some samples of the reference block are not reconstructed, determining the at least some unreconstructed samples using reconstructed samples of the current image; and reconstructing the current block using the reference block including the determined at least some samples.

Description

TECHNICAL FIELD The present disclosure relates to the field of image encoding and decoding. More particularly, the present disclosure relates to an apparatus and method for encoding and decoding an image by using a reference block. BACKGROUND ART In image encoding and decoding, an image is split into blocks, and each block is prediction-encoded and prediction-decoded through inter prediction or intra prediction. Inter prediction is a technique for compressing an image by removing temporal redundancy between images. In inter prediction, blocks of a current image are predicted by using a reference image. A reference block that is most similar to a current block may be searched for within a certain search range in the reference image. The current block is predicted based on the reference block, and a prediction block generated as a result of the prediction is subtracted from the current block to generate a residual block. Intra prediction is a technique for compressing an image by removing spatial redundancy within the image. Intra prediction generates a prediction block based on neighboring pixels of a current block according to a prediction mode. Then, the prediction block is subtracted from the current block to generate a residual block. A residual block generated through inter prediction or intra prediction is transformed, quantized, and then transmitted to a decoder. The decoder inversely quantizes and inversely transforms the residual block, and reconstructs a current block by combining a prediction block of a current block with the residual block. The decoder may filter the reconstructed current block to remove artifacts within the reconstructed current block. DISCLOSURE OF INVENTION SOLUTION TO PROBLEM An image decoding method according to an embodiment of the present disclosure is provided. When a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, the method may include determining the reference block in the current image including the current block. At least some samples of the reference block may be reconstructed. When all samples of the reference block are reconstructed, the method may include reconstructing the current block by using the reference block. When at least some samples of the reference block are not reconstructed, the method may include determining the at least some unreconstructed samples by using reconstructed samples of the current image. The method may include reconstructing the current block by using the reference block including the determined at least some samples. An image decoding apparatus according to an embodiment of the present disclosure is provided. The image decoding apparatus may include at least one processor. When a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, the at least one processor may be configured to determine the reference block in the current image including the current block. At least some samples of the reference block may be reconstructed. When all samples of the reference block are reconstructed, the at least one processor may be configured to reconstruct the current block by using the reference block. When at least some samples of the reference block are not reconstructed, the at least one processor may be configured to determine the at least some unreconstructed samples by using reconstructed samples of the current image. The at least one processor may be configured to reconstruct the current block by using the reference block including the determined at least some samples. According to an embodiment of the present disclosure, an image encoding method is provided. When a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, the method may include determining the reference block in the current image including the current block. At least some samples of the reference block may be reconstructed. When all samples of the reference block are reconstructed, the method may include reconstructing the current block by using the reference block. When at least some samples of the reference block are not reconstructed, the method may include determining the at least some unreconstructed samples by using reconstructed samples of the current image. The method may include reconstructing the current block by using the reference block including the determined at least some samples. An image encoding apparatus according to an embodiment of the present disclosure is provided. The image encoding apparatus may include at least one processor. When a prediction mode of a current block is a mode for determining a reference block in a current image including the current block, the at least one processor may be configured to determine the reference block in the current image including the current block. At least some samples of the reference block may