Method and apparatus for encoding/decoding image

Abstract

The present invention relates to a method which can selectively skip a transform to alleviate problems of deterioration in compression rate and image quality which are mainly generated when applying the motion compensation-transform encoding image compression technique which is mainly used currently, to an image having a drastic spatial change in a pixel value such as a computer image, and can skip the transform by comparing a transform size of a current block and the size of a maximum transform skip block with each other, and provides an efficient signaling technique therefor. The method includes the steps of: comparing the size of a current transform unit (TU) with the size of a maximum transform skip block when determining whether to transform a residual signal corresponding to a difference value between the current block and a prediction block; and determining whether to perform the transform on the basis of the comparison information on the size of the TU and the size of the maximum transform skip block.

Description

technical field [0001] The present invention relates to encoding / decoding of images, and more particularly to a method and apparatus for determining whether to skip transformation and performing encoding / decoding. Background technique [0002] Transforms are always performed in accordance with motion compensated transform coding image compression techniques such as H.264 or High Efficiency Video Coding (HEVC). However, if the degree of variation of the spatial pixel values ​​within the corresponding block whose video is to be compressed is very large or sharp, the degree to which video energy is concentrated on low frequencies is not so great even if transformation is performed. In compression processing, if low-frequency components are maintained and high-frequency components are removed or strong quantization is applied to high-frequency components, picture quality may be severely degraded. In particular, such problems are significant in the case of computer-generated art...

AI Technical Summary

Problems solved by technology

If the minimum transform block size (hereinafter referred to as STU) determined by the encoder is 8×8 or larger, the current technology has a technical disadvantage that the execution of the block transform cannot even be skipped under any circumstances.

In other words, in this case, since the transformation efficiency of the blocks within the video is very low, a reduction in the compression ratio or a deterioration of the picture quality must be endured, because there is a problem that although it is more advantageous to skip the transformation, the Transformation cannot be skipped with current technology

In other words, if the inefficiency problem is only considered in the 4×4 transform block and the transform is skipped according to the existing technology, it may cause problems such as reduced compression ratio or picture quality degradation in some videos

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