US-12621479-B2 - Image encoding/decoding method and device therefor

US12621479B2US 12621479 B2US12621479 B2US 12621479B2US-12621479-B2

Abstract

The present invention relates to a video signal decoding method based on a Multiple Transform Selection (MTS). The method may comprise the steps of parsing a first syntax element representing whether MTS applies to the inverse transformation of a current block, wherein the MTS represents a transform mode which uses a transform type other than a default transform type predefined for the current block; by performing inverse quantization on the current block, deriving an inverse-quantized transform coefficient array having the width and the height of the current block; determining, on the basis of the first syntax element, a vertical transform type applying to the vertical direction of the current block, and a horizontal transform type applying to the horizontal direction of the current block; and, by performing inverse transformation on the inverse-quantized transform coefficient array by using the vertical transform type and the horizontal transform type, deriving a residual sample array having the width and the height of the current block.

Inventors

Moonmo KOO
Mehdi Salehifar
Seunghwan Kim
Jaehyun Lim

Assignees

NOKIA TECHNOLOGIES OY

Dates

Publication Date: 20260505
Application Date: 20250203

Claims (7)

1 . An apparatus configured to: obtain syntax elements from a bitstream, wherein the syntax elements include a first syntax element indicating whether a third syntax element could be present in a syntax for an intra coding unit, a second syntax element indicating whether the third syntax element could be present in a syntax for an inter coding unit, and the third syntax element corresponding to one of a plurality of transform combinations, wherein the first and second syntax elements are included in a sequence parameter set (SPS) of the bitstream, derive an inverse quantized transform coefficient array of a current block by performing inverse quantization on the current block, determine a vertical transform type applied to a vertical direction and a horizontal transform type applied to a horizontal direction of the current block based on the third syntax element, and derive a residual sample array of the current block by performing inverse transform on the inverse quantized transform coefficient array based on the vertical transform type and the horizontal transform type, wherein performing the inverse transform includes: performing, based on the vertical transform type, a one-dimensional transform process in the vertical direction on each of columns of the inverse quantized transform coefficient array; and performing, based on the horizontal transform type, a one-dimensional transform process in the horizontal direction on each of rows of an intermediate sample array output by the one-dimensional transform process for each of the columns, wherein performing the one-dimensional transform process in the horizontal direction includes clipping an intermediate sample value output by the one-dimensional transform process for each of the columns based on a minimum value and a maximum value of a predefined coefficient.
2 . The method of claim 1 , wherein the plurality of transform combinations includes at least one of DCT2, DST7, or DCT8.
3 . The method of claim 1 , wherein based on the third syntax element being equal to a value of zero, the vertical transform type and the horizontal transform type are determined as DCT2, and wherein based on the third syntax element being equal to a value of non-zero, each of the vertical transform type and the horizontal transform type is determined as one of DST7 or DCT8.
4 . An apparatus configured to: generate a residual sample array of a current block, determine a vertical transform type applied to a vertical direction of the current block and a horizontal transform type applied to a horizontal direction of the current block, derive a transform coefficient array of the current block by performing transform on the current block based on the vertical transform type and horizontal transform type, derive a quantized transform coefficient array of the current block by performing quantization on the current block, and entropy-encode the quantized transform coefficient array of the current block, wherein syntax elements are encoded into a bitstream, wherein the syntax elements include a first syntax element indicating whether a third syntax element could be present in a syntax for an intra coding unit, a second syntax element indicating whether the third syntax element could be present in a syntax for an inter coding unit, and the third syntax element corresponding to one of a plurality of transform combinations, wherein the first and second syntax elements are included in a sequence parameter set (SPS) of the bitstream, wherein performing the transform on the current block includes: performing, based on the horizontal transform type, a one-dimensional transform process in the horizontal direction on each of rows of the residual sample array; and performing, based on the vertical transform type, a one-dimensional transform process in the vertical direction on each of columns of an intermediate sample array output by the one-dimensional transform process for each of the rows of the residual sample array.
5 . The method of claim 4 , wherein the plurality of transform combinations includes at least one of DCT2, DST7, or DCT8.
6 . The method of claim 4 , wherein the third syntax element is encoded as a value of zero based on the vertical transform type and the horizontal transform type being determined as DCT2, and wherein the third syntax element is encoded as a value of non-zero based on each of the vertical transform type and the horizontal transform type being determined as one of DST7 or DCT8.
7 . An apparatus configured to: obtain a bitstream for an image, wherein the bitstream is generated by: generating a residual sample array of a current block, determining a vertical transform type applied to a vertical direction of the current block and a horizontal transform type applied to a horizontal direction of the current block, deriving a transform coefficient array of the current block by performing transform on the current block based on the vertical transform type and horizontal transform type, deriving a quantized transform coefficient array of the current block by performing quantization on the current block, and entropy-encoding the quantized transform coefficient array of the current block, and transmit data comprising the bitstream, wherein syntax elements are encoded into the bitstream, wherein the syntax elements include a first syntax element indicating whether a third syntax element could be present in a syntax for an intra coding unit, a second syntax element indicating whether the third syntax element could be present in a syntax for an inter coding unit, and the third syntax element corresponding to one of a plurality of transform combinations, wherein the first and second syntax elements are included in a sequence parameter set (SPS) of the bitstream, wherein performing the transform on the current block includes: performing, based on the horizontal transform type, a one-dimensional transform process in the horizontal direction on each of rows of the residual sample array; and performing, based on the vertical transform type, a one-dimensional transform process in the vertical direction on each of columns of an intermediate sample array output by the one-dimensional transform process for each of the rows of the residual sample array.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 18/386,135 filed Nov. 1, 2023, now allowed, which is a continuation of Ser. No. 17/716,772 filed Apr. 8, 2022, now U.S. patent Ser. No. 11/863,778 issued Jan. 2, 2024, which is a continuation of Ser. No. 17/266,407 filed Feb. 5, 2021 now U.S. patent Ser. No. 11/412,242 issued Aug. 9, 2022 a National Stage Application of International Application No. PCT/KR2019/009990, filed on Aug. 8, 2019, which claims priority under 35 U.S.C. 119(e) to a U.S. Provisional Application No. 62/716,355 filed on Aug. 8, 2018, which is hereby incorporated by reference herein in their entirety. TECHNICAL FIELD The present disclosure relates to a method and apparatus for encoding/decoding a video and, more particularly, to a technology for performing a transform/inverse transform based on a Multiple Transform Selection (MTS). BACKGROUND ART Next-generation video content will have characteristics of a high spatial resolution, a high frame rate, and high dimensionality of scene representation. In order to process such content, technologies, such as memory storage, a memory access rate, and processing power, will be remarkably increased. Accordingly, it is necessary to design a new coding tool for more efficiently processing next-generation video content. Particularly, it is necessary to design a more efficient transform in terms of coding efficiency and complexity when a transform is applied. DISCLOSURE Technical Problem The present disclosure is intended to propose an operation algorithm having low complexity for a transform kernel for video compression. The present disclosure is intended to propose a method of designing discrete sine transform-7 (DST7) having low complexity. The present disclosure is intended to propose a method of designing forward DST7 and inverse DST7 as a discrete Fourier transform (DFT). The present disclosure is intended to propose a method of implementing DST7 through a one-dimensional DFT or a two-dimensional DFT. The present disclosure is intended to propose a method of implementing DST7 using only an integer operation by applying various scaling methods. The present disclosure is intended to propose a method of designing DST7 having a length 8, 16, or 32, through a method of implementing DST7 using a DFT and a method of implementing DST7 using only an integer operation. The present disclosure is intended to propose an encoder/decoder structure for incorporating a new transform design. The present disclosure is intended to propose an overall transform process according to an embodiment proposed in the present disclosure. Technical Solution In an aspect of the present disclosure, a method of decoding a video signal based on a Multiple Transform Selection (MTS) may include parsing a first syntax element indicating whether the MTS is applied to an inverse transform of a current block, wherein the MTS indicates a transform mode using another transform type other than a predefined default transform type in the current block, deriving an inverse quantized transform coefficient array with the width and height of the current block by performing inverse quantization on the current block, determining a vertical transform type applied to a vertical direction and horizontal transform type applied to a horizontal direction of the current block based on the first syntax element, and deriving a residual sample array with the width and height of the current block by performing an inverse transform on the inverse quantized transform coefficient array using the vertical transform type and the horizontal transform type. Preferably, the default transform type may be configured as DCT2, and the remaining transform types other than the default transform type may be configured as DST7 and DCT8. Preferably, if the first syntax element indicates that the MTS is not applied to the inverse transform of the current block, the vertical transform type and the horizontal transform type may be determined as DCT2. If the first syntax element indicates that the MTS is applied to the inverse transform of the current block, each of the vertical transform type and the horizontal transform type may be determined as any one of DST7 and DCT8. Preferably, the method further includes parsing a second syntax element indicating whether the MTS is available for an intra coding block and a third syntax element indicating whether the MTS is available for an inter coding block. When the second syntax element is 1, the first syntax element may be present in a transform unit syntax for the intra coding block, and when the third syntax element is 1, the first syntax element may be present in a transform unit syntax for the inter coding block. Preferably, deriving the residual sample array may includes performing a one-dimensional transform process in the vertical direction on each of columns of the inverse quantized transform coefficient array us