EP-4742666-A1 - IMAGE ENCODING/DECODING METHOD AND APPARATUS, AND RECORDING MEDIUM STORING BITSTREAM

Abstract

An image decoding method and apparatus according to the present disclosure may: acquire residual information from a bitstream; derive transform coefficients of the current block on the basis of the residual information; derive residual samples of the current block by performing at least one of dequantization and inverse transform on the transform coefficients of the current block; and reconstruct the current block on the basis of the residual samples of the current block. Here, the inverse transform may be performed on the basis of at least one of a non-separable primary transform, a low-frequency non-separable transform, and a separable primary transform.

Inventors

• Koo, Moonmo
• LIM, JAEHYUN
• KIM, SEUNGHWAN

Assignees

• LG Electronics Inc.

Dates

Publication Date

20260513

Application Date

20240703

Claims (14)

1. An image decoding method, comprising: obtaining residual information from a bitstream; deriving transform coefficients of a current block based on the residual information; deriving residual samples of the current block by performing at least one of dequantization or inverse transform on the transform coefficients of the current block; and reconstructing the current block based on the residual samples of the current block, wherein the inverse transform is performed based on at least one of non-separable primary transform (NSPT), low frequency non-separable transform (LFNST), or separable primary transform, wherein pre-defined allowed transform block sizes are divided into a plurality of groups, and wherein the plurality of groups include at least two of a first group including block sizes that a minimum value of a width and a height is 4, a second group including block sizes that the minimum value of the width and the height is 8, a third group including block sizes that the minimum value of the width and the height is 16, a fourth group including block sizes greater than or equal to 16x16, a fifth group including block sizes greater than or equal to 32x32, or a sixth group including block sizes greater than or equal to 8x8.
2. The method of claim 1, wherein one of the plurality of groups includes one or more block sizes to which the NSPT is applicable.
3. The method of claim 2, wherein the one of the plurality of groups includes one or more block sizes to which the NSPT and the LFNST are not applied.
4. The method of claim 2, wherein the one of the plurality of groups includes one or more block sizes to which the LFNST is applicable.
5. The method of claim 1, wherein the NSPT is applicable to a 4xL block and an Lx4 block (4≤L≤32) belonging to the first group, and wherein the NSPT and the LFNST are not applied to a 4xM block and an Mx4 block (M>32) belonging to the first group.
6. The method of claim 1, wherein the NSPT is applicable to a 4x4 block belonging to the first group, and wherein the LFNST is applicable to a 4xL block and an Lx4 block (L≥8) belonging to the first group.
7. The method of claim 1, wherein the NSPT is applicable to a 4x4 block belonging to the first group, and wherein the NSPT and the LFNST are not applied to a 4xL block and an Lx4 block (L≥8) belonging to the first group.
8. The method of claim 1, wherein the NSPT is applicable to an 8xL block and an Lx8 block (8≤L≤32) belonging to the second group, and wherein the NSPT and the LFNST are not applied to an 8xM block and an Mx8 block (M>32) belonging to the second group.
9. The method of claim 1, wherein the NSPT is applicable to an 8x8 block belonging to the second group, and wherein the LFNST is applicable to an 8xL block and an Lx8 block (L≥16) belonging to the second group.
10. The method of claim 1, wherein the NSPT is applicable to an 8x8 block belonging to the second group, and wherein the NSPT and the LFNST are not applied to an 8xL block and an Lx8 block (L≥16) belonging to the second group.
11. The method of claim 1, wherein the NSPT is not applied to at least one of the third group to the sixth group.
12. An image encoding method, comprising: deriving residual samples of a current block; deriving transform coefficients of the current block by performing at least one of transform or quantization on the residual samples of the current block; and encoding the transform coefficients of the current block, wherein the transform is performed based on at least one of non-separable primary transform (NSPT), separable primary transform, or low frequency non-separable transform (LFNST), wherein pre-defined allowed transform block sizes are divided into a plurality of groups, and wherein the plurality of groups include at least two of a first group including block sizes that a minimum value of a width and a height is 4, a second group including block sizes that the minimum value of the width and the height is 8, a third group including block sizes that the minimum value of the width and the height is 16, a fourth group including block sizes greater than or equal to 16x16, a fifth group including block sizes greater than or equal to 32x32, or a sixth group including block sizes greater than or equal to 8x8.
13. A computer-readable storage medium storing a bitstream generated by the image encoding method according to claim 12.
14. A method for transmitting data, comprising: obtaining a bitstream for image information, wherein the bitstream is generated by deriving residual samples of a current block, deriving transform coefficients by performing at least one of transform or quantization on the residual samples of the current block, and encoding a transform coefficient of the current block; and transmitting data including the bitstream, wherein the transform is performed based on at least one of non-separable primary transform (NSPT), separable primary transform, or low frequency non-separable transform (LFNST), wherein pre-defined allowed transform block sizes are divided into a plurality of groups, and wherein the plurality of groups include at least two of a first group including block sizes that a minimum value of a width and a height is 4, a second group including block sizes that the minimum value of the width and the height is 8, a third group including block sizes that the minimum value of the width and the height is 16, a fourth group including block sizes greater than or equal to 16x16, a fifth group including block sizes greater than or equal to 32x32, or a sixth group including block sizes greater than or equal to 8x8.

Description

[Technical Field] The present disclosure relates to an image encoding/decoding method and apparatus, and a recording medium storing a bitstream. [Background Art] Recently, the demand for high-resolution and high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images has been increasing in various application fields, and accordingly, highly efficient image compression technologies are being discussed. There are a variety of technologies such as inter-prediction technology that predicts a pixel value included in a current picture from a picture before or after a current picture with video compression technology, intra-prediction technology that predicts a pixel value included in a current picture by using pixel information in a current picture, entropy coding technology that allocates a short sign to a value with high appearance frequency and a long sign to a value with low appearance frequency, etc. and these image compression technologies may be used to effectively compress image data and transmit or store it. [Disclosure] [Technical Problem] The present disclosure is to provide a method and an apparatus for performing a transform by using a non-separable primary transform. The present disclosure is to provide a method and an apparatus for performing a transform by using a non-separable primary transform kernel of a reduced dimension. The present disclosure is to provide a method and an apparatus for determining/signaling a non-separable transform kernel based on an encoding parameter. [Technical Solution] An image decoding method and apparatus according to the present disclosure may obtain residual information from a bitstream, derive transform coefficients of a current block based on the residual information, derive residual samples of the current block by performing at least one of dequantization or inverse transform on the transform coefficients of the current block and reconstruct the current block based on the residual samples of the current block. In an image decoding method and apparatus according to the present disclosure, the inverse transform may be performed based on at least one of non-separable primary transform (NSPT), low frequency non-separable transform (LFNST) or separable primary transform. In an image decoding method and apparatus according to the present disclosure, pre-defined allowed transform block sizes may be divided into a plurality of groups, and the plurality of groups may include at least two of a first group including block sizes that a minimum value of a width and a height is 4, a second group including block sizes that the minimum value of the width and the height is 8, a third group including block sizes that the minimum value of the width and the height is 16, a fourth group including block sizes greater than or equal to 16x16, a fifth group including block sizes greater than or equal to 32x32 or a sixth group including block sizes greater than or equal to 8x8. In an image decoding method and apparatus according to the present disclosure, any one of the plurality of groups may include one or more block sizes to which the NSPT is applicable. In an image decoding method and apparatus according to the present disclosure, any one of the plurality of groups may include one or more block sizes to which the NSPT and the LFNST are not applied. In an image decoding method and apparatus according to the present disclosure, any one of the plurality of groups may include one or more block sizes to which the LFNST is applicable. In an image decoding method and apparatus according to the present disclosure, the NSPT may be applied to a 4xL block and an Lx4 block (4≤L≤32) belonging to the first group, and the NSPT and the LFNST may not be applied to a 4xM block and an Mx4 block (M>32) belonging to the first group. In an image decoding method and apparatus according to the present disclosure, the NSPT may be applied to a 4x4 block belonging to the first group, and the LFNST may be applied to a 4xL block and an Lx4 block (L≥8) belonging to the first group. In an image decoding method and apparatus according to the present disclosure, the NSPT may be applied to a 4x4 block belonging to the first group, and the NSPT and the LFNST may not be applied to a 4xL block and an Lx4 block (L≥8) belonging to the first group. In an image decoding method and apparatus according to the present disclosure, the NSPT may be applied to an 8xL block and an Lx8 block (8≤L≤32) belonging to the second group, and the NSPT and the LFNST may not be applied to an 8xM block and an Mx8 block (M>32) belonging to the second group. In an image decoding method and apparatus according to the present disclosure, the NSPT may be applied to an 8x8 block belonging to the second group, and the LFNST may be applied to an 8xL block and an Lx8 block (L≥16) belonging to the second group. In an image decoding method and apparatus according to the present disclosure, the NSPT may be applied to an 8