US-20260129234-A1 - METHOD AND APPARATUS FOR ENCODING/DECODING RESIDUAL DATA BASED ON A PLURALITY OF TRANSFORMATIONS

Abstract

An image decoding method according to the present invention can comprise the steps of: acquiring residual coefficients of a current block; dequantizing the residual coefficients; performing secondary inverse transformation on the dequantized residual coefficients; and performing primary inverse transformation on the performance result of the secondary inverse transformation. The secondary inverse transformation can be performed for a partial region of the current block.

Inventors

• Bae Keun Lee

Assignees

• KT CORPORATION

Dates

Publication Date

20260507

Application Date

20251008

Priority Date

20180608

Claims (8)

1. 1 - 15 . (canceled)
2. 16 . A method of decoding an image, comprising: obtaining prediction samples of a current block; determining a horizontal transform type and a vertical transform type of the current block from a transform set including two transform type candidates; performing an inverse-transform on the current block based on the horizontal transform type and the vertical transform type; and reconstructing the current block by summing residual samples, resulting from the inverse-transform, and the prediction samples, wherein the horizontal transform type is determined based on whether a width of the current block is in a predefined range, wherein the vertical transform type is determined based on whether a height of the current block is in the predefined range, wherein when the current block has a square shape, in which the width and the height are the same, the horizontal transform type and the vertical transform type are mutually the same, and wherein when the current block has a non-square shape, in which the width is in the predefined range while the height is not in the predefined range, the horizontal transform type and the vertical transform type are different from each other.
3. 17 . The method of claim 16 , wherein the pre-defined range is defined as a range of 4 to 16.
4. 18 . The method of claim 16 , wherein one of the two transform type candidates is representative of one of DCT-II or DST-VII and the other of the two transform type candidates is representative of the other of DCT-II or DST-VII.
5. 19 . The method of claim 16 , wherein a prediction mode of the current block is intra prediction.
6. 20 . The method of claim 16 , wherein whether to decode index information from a bitstream to determine the transform set of the current block is determined based on a partition type of a coding block including the current block.
7. 21 . A method of encoding an image, comprising: obtaining prediction samples of a current block; deriving residual samples of the current block by subtracting the prediction samples from original samples; determining a horizontal transform type and a vertical transform type of the current block from a transform set including two transform type candidates; performing a transform on the residual samples of the current block based on the horizontal transform type and the vertical transform type; performing quantization on transform coefficients obtained by the transform; and encoding quantized transform coefficients, wherein the horizontal transform type is determined based on whether a width of the current block is in a predefined range, wherein the vertical transform type is determined based on whether a height of the current block is in the predefined range, wherein when the current block has a square shape, in which the width and the height are the same, the horizontal transform type and the vertical transform type are mutually the same, and wherein when the current block has a non-square shape, in which the width is in the predefined range while the height is not in the predefined range, the horizontal transform type and the vertical transform type are different from each other.
8. 22 . A method for transmitting a bitstream generated by an encoding method, the encoding method comprising: obtaining prediction samples of a current block; deriving residual samples of the current block by subtracting the prediction samples from original samples; determining a horizontal transform type and a vertical transform type of the current block from a transform set including two transform type candidates; performing a transform on the residual samples of the current block based on the horizontal transform type and the vertical transform type; performing quantization on transform coefficients obtained by the transform; and encoding quantized transform coefficients, wherein the horizontal transform type is determined based on whether a width of the current block is in a predefined range, wherein the vertical transform type is determined based on whether a height of the current block is in the predefined range, wherein when the current block has a square shape, in which the width and the height are the same, the horizontal transform type and the vertical transform type are mutually the same, and wherein when the current block has a non-square shape, in which the width is in the predefined range while the height is not in the predefined range, the horizontal transform type and the vertical transform type are different from each other.

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for processing video signal. BACKGROUND ART Recently, demands for high-resolution and high-quality images such as high definition (HD) images and ultra-high definition (UHD) images have increased in various application fields. However, higher resolution and quality image data has increasing amounts of data in comparison with conventional image data. Therefore, when transmitting image data by using a medium such as conventional wired and wireless broadband networks, or when storing image data by using a conventional storage medium, costs of transmitting and storing increase. In order to solve these problems occurring with an increase in resolution and quality of image data, high-efficiency image encoding/decoding techniques may be utilized. Image compression technology includes various techniques, including: an inter-prediction technique of predicting a pixel value included in a current picture from a previous or subsequent picture of the current picture; an intra-prediction technique of predicting a pixel value included in a current picture by using pixel information in the current picture; an entropy encoding technique of assigning a short code to a value with a high appearance frequency and assigning a long code to a value with a low appearance frequency; etc. Image data may be effectively compressed by using such image compression technology, and may be transmitted or stored. In the meantime, with demands for high-resolution images, demands for stereographic image content, which is a new image service, have also increased. A video compression technique for effectively providing stereographic image content with high resolution and ultra-high resolution is being discussed. DISCLOSURE Technical Problem An object of the present invention is to provide a method and an apparatus for encoding/decoding residual data based on a plurality of transformations. An object of the present invention is to provide a method and an apparatus for performing the secondary transformation on a partial region of a block on which the primary transformation has been performed. The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems. And, other technical problems that are not mentioned will be apparently understood to those skilled in the art from the following description. Technical Solution A video signal decoding method and apparatus according to the present invention may acquire residual coefficients of a current block, inverse quantize the residual coefficients, perform a secondary inverse transformation on the inverse quantized residual coefficients, and perform a primary inverse transformation on a result of performing the secondary inverse transformation. In this case, the secondary inverse transformation is performed on a partial region of the current block. A video signal encoding method and apparatus according to the present invention may perform a primary transformation on residual samples, perform a secondary transformation on primary transform coefficients generated as a result of the primary transformation, quantize secondary transform coefficients generated as a result of the secondary transformation, and encode the quantized transform coefficients. In this case, the secondary transformation is performed on a partial region of a current block. In the method and apparatus for encoding/decoding a video signal according to the present invention, the secondary transformation/inverse transformation is performed using a transform matrix and a one-dimensional matrix generated by arranging the inverse quantized residual coefficients included in the partial region in one dimension. In the method and apparatus for encoding/decoding a video signal according to the present invention, a number of rows or columns of the transform matrix is smaller than a number of samples included in the partial region. In the method and apparatus for encoding/decoding a video signal according to the present invention, a size or shape of the partial region is determined based on a size or shape of the current block. In the method and apparatus for encoding/decoding a video signal according to the present invention, a transform/inverse transform type for the primary inverse transformation is determined based on index information signaled through a bitstream. In the method and apparatus for encoding/decoding a video signal according to the present invention, the index information specifics any one of a plurality of transform sets, a first transform type candidate included in the transform set is determined as a horizontal direction transform type of the current block, and a second transform type candidate included in the transform set is determined as a vertical direction transform type of the current block. In the method and apparatus for encoding/decoding a video signal according to the present invention, a tr