KR-102961966-B1 - METHOD AND APPARATUS FOR IMAGE ENCODING/DECODING AND RECORDING MEDIUM FOR STORING BITSTREAM

Abstract

The present invention relates to a transformation-based image encoding/decoding method and apparatus. An image decoding method according to the present invention may include the steps of selecting one transformation kernel among a plurality of transformation kernels, performing an inverse transformation on a residual block of a current block based on the selected transformation kernel, and restoring the current block based on the inversely transformed residual block.

Inventors

• 임성창
• 강정원
• 이하현
• 이진호
• 김휘용
• 이영렬
• 김남욱

Assignees

• 한국전자통신연구원
• 세종대학교산학협력단

Dates

Publication Date

20260508

Application Date

20190318

Priority Date

20180328

Claims (20)

1. A step of generating a residual block of the current block by performing an inverse transformation on the residual information of the current block based on a transformation kernel; and It includes the step of restoring the current block based on the remaining block above, and If the above current block is a predicted block within the screen, the transformation kernel is selected based on at least one of the size and shape of the above remaining block, and If the above current block is a predicted block within the screen and the horizontal length of the above remaining block is included within a predetermined range, the horizontal transformation kernel to be applied to the horizontal transformation of the above remaining block is a first transformation kernel, and If the above current block is a predicted block within the screen and the above horizontal length of the above remaining block is not included within the above predetermined range, the horizontal transformation kernel to be applied to the horizontal transformation of the above remaining block is a second transformation kernel, and If the current block is a predicted block within the screen and the vertical length of the remaining block is included within the predetermined range, the vertical transformation kernel to be applied to the vertical transformation of the remaining block is the first transformation kernel, and If the above current block is a predicted block within the screen and the above vertical length of the above remaining block is not included within the above predetermined range, the above vertical transformation kernel to be applied to the vertical transformation of the above remaining block is the above second transformation kernel, and An image decoding method in which the above-mentioned predetermined range is a range from 4 pixels in length to 16 pixels in length.
2. In paragraph 1, The above conversion kernel is an image decoding method selected from a plurality of conversion kernels based on information regarding the conversion kernel included in the bitstream.
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6. In paragraph 1, A video decoding method in which the first conversion kernel is DST-7 and the second conversion kernel is DCT-2.
7. In paragraph 1, When in-screen prediction is performed for each of the multiple sub-blocks included in the above current block, The above conversion kernel is an image decoding method performed based on the size of the above residual block.
8. In paragraph 1, When the above current block is an inter-screen predicted block, and the above transformation is performed on one of the sub-remaining blocks among the blocks obtained by dividing the above current block, The above conversion kernel is an image decoding method selected based on information regarding the division of the current block.
9. In paragraph 8, Information regarding the division of the current block above is, An image decoding method including partition direction information indicating whether the partition direction is vertical partitioning or horizontal partitioning.
10. In paragraph 8, A video decoding method in which information regarding the division of the current block is included in the bitstream and signaled.
11. A step of performing a transformation on the remaining blocks of the current block based on a transformation kernel; and It includes the step of encoding the current block based on the converted residual block, and If the above current block is a predicted block within the screen, the transformation kernel is selected based on at least one of the size and shape of the above remaining block, and If the above current block is a predicted block within the screen and the horizontal length of the above remaining block is included within a predetermined range, the horizontal transformation kernel to be applied to the horizontal transformation of the above remaining block is a first transformation kernel, and If the above current block is a predicted block within the screen and the above horizontal length of the above remaining block is not included within the above predetermined range, the horizontal transformation kernel to be applied to the horizontal transformation of the above remaining block is a second transformation kernel, and If the current block is a predicted block within the screen and the vertical length of the remaining block is included within the predetermined range, the vertical transformation kernel to be applied to the vertical transformation of the remaining block is the first transformation kernel, and If the above current block is a predicted block within the screen and the above vertical length of the above remaining block is not included within the above predetermined range, the above vertical transformation kernel to be applied to the vertical transformation of the above remaining block is the above second transformation kernel, and An image encoding method in which the above predetermined range is a range from 4 pixels in length to 16 pixels in length.
12. In Paragraph 11, The above conversion kernel is selected from among a plurality of conversion kernels, and Information regarding a conversion kernel for specifying the above conversion kernel is included in the bitstream in the image encoding method.
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15. In Paragraph 11, A video encoding method in which the first conversion kernel is DST-7 and the second conversion kernel is DCT-2.
16. In Paragraph 11, When in-screen prediction is performed for each of the multiple sub-blocks included in the above current block, The above conversion kernel is an image encoding method performed based on the size of the above residual block.
17. In Paragraph 11, When the above current block is an inter-screen predicted block, and the above transformation is performed on one of the sub-remaining blocks among the blocks obtained by dividing the above current block, The above conversion kernel is an image encoding method selected based on information regarding the division of the current block.
18. In Paragraph 17, Information regarding the division of the current block above is, An image encoding method including division direction information indicating whether the division direction is vertical division or horizontal division.
19. In Paragraph 17, A video encoding method in which information regarding the division of the current block is included in a bitstream and signaled.
20. A computer-readable recording medium storing a bitstream received by a video decoding device and used to restore a current block contained in a video, The above bitstream includes residual information of the current block, and A residual block of the current block is generated based on an inverse transformation and transformation kernel using the residual information of the current block, and The above remaining block is used to restore the above current block, and If the above current block is a predicted block within the screen, the transformation kernel is selected based on at least one of the size and shape of the above remaining block, and If the above current block is a predicted block within the screen and the horizontal length of the above remaining block is included within a predetermined range, the horizontal transformation kernel to be applied to the horizontal transformation of the above remaining block is a first transformation kernel, and If the above current block is a predicted block within the screen and the above horizontal length of the above remaining block is not included within the above predetermined range, the horizontal transformation kernel to be applied to the horizontal transformation of the above remaining block is a second transformation kernel, and If the current block is a predicted block within the screen and the vertical length of the remaining block is included within the predetermined range, the vertical transformation kernel to be applied to the vertical transformation of the remaining block is the first transformation kernel, and If the above current block is a predicted block within the screen and the above vertical length of the above remaining block is not included within the above predetermined range, the above vertical transformation kernel to be applied to the vertical transformation of the above remaining block is the above second transformation kernel, and A computer-readable recording medium in which the above-mentioned predetermined range is a range from 4 pixels in length to 16 pixels in length.

Description

Method and apparatus for image encoding/decoding and recording medium for storing bitstream The present invention relates to a method and apparatus for encoding/decoding images, and more specifically, to a method and apparatus for encoding/decoding video images based on transform, shuffling, rearrangement, and flipping. Recently, the demand for high-resolution, high-quality video, such as HD (High Definition) and UHD (Ultra High Definition) video, has been increasing across various application fields. As video data becomes higher in resolution and quality, the relative volume of data increases compared to conventional video data; consequently, transmission and storage costs increase when video data is transmitted using existing wired or wireless broadband lines or stored using existing storage media. To address these issues arising from the increase in video data resolution and quality, high-efficiency video encoding and decoding technologies for video with higher resolution and quality are required. Various video compression technologies exist, such as inter-frame prediction technology that predicts pixel values in the current picture from previous or subsequent pictures, intra-frame prediction technology that predicts pixel values in the current picture using pixel information within the current picture, transformation and quantization technology for compressing the energy of residual signals, and entropy coding technology that assigns short codes to values with high frequency and long codes to values with low frequency; by utilizing these video compression technologies, video data can be effectively compressed for transmission or storage. FIG. 1 is a block diagram showing the configuration according to one embodiment of an encoding device to which the present invention is applied. FIG. 2 is a block diagram showing the configuration according to one embodiment of a decoding device to which the present invention is applied. Figure 3 is a diagram schematically showing the segmentation structure of an image when encoding and decoding an image. Figure 4 is a diagram illustrating an example of an in-screen prediction process. Figure 5 is a diagram illustrating an example of an inter-frame prediction process. Figure 6 is a diagram illustrating the process of transformation and quantization. FIG. 7 is a diagram illustrating the basis vector in the frequency domain of DCT-2 according to the present invention. FIG. 8 is a diagram illustrating the basis vectors in each frequency domain of DST-7 according to the present invention. Figure 9 is a diagram showing the distribution of average residual values according to the position within the 2Nx2N prediction unit (PU) of the 8x8 coding unit (CU) predicted in inter mode, obtained by experimenting with the “Cactus” sequence in a Low Delay-P profile environment. Figure 10 is a three-dimensional graph showing the residual signal distribution characteristics within the 2Nx2N prediction unit (PU) of the 8x8 coding unit (CU) predicted in inter-mode prediction. FIG. 11 is a diagram illustrating the distribution characteristics of residual signals in the 2Nx2N prediction unit (PU) mode of a coding unit (CU) according to the present invention. FIG. 12 is a diagram illustrating the residual signal distribution characteristics before and after shuffling of a 2Nx2N prediction unit (PU) according to the present invention. FIG. 13 is a diagram illustrating an example of 4x4 residual data rearrangement of a subblock according to the present invention. FIGS. 14(a) and FIGS. 14(b) are drawings for illustrating an example of a conversion unit (TU) splitting structure of a coding unit (CU) according to a prediction unit (PU) mode and a shuffling method of a conversion unit (TU). Figure 15 is a diagram illustrating the results of performing DCT-2 transformation and SDST transformation according to the residual signal distribution of the 2Nx2N prediction unit (PU). FIG. 16 is a diagram illustrating the SDST process according to the present invention. FIG. 17 is a diagram illustrating the distribution characteristics of the size of the division of the conversion unit (TU) and the residual absolute value according to the partition mode of the prediction unit (PU) of the inter-frame predicted coding unit (CU) according to the present invention. FIG. 18 is a diagram illustrating the residual signal scanning sequence and relocation sequence of a conversion unit (TU) with a depth of 0 within a prediction unit (PU) according to one embodiment of the present invention. FIG. 19 is a flowchart illustrating the DCT-2 or SDST selective encoding process through rate-distortion optimization (RDO) according to the present invention. FIG. 20 is a flowchart illustrating the process of selecting and decoding DCT-2 or SDST according to the present invention. FIG. 21 is a flowchart illustrating a decoding process using SDST according to the present invention. FIGS. 22 and FIGS. 23 each show the locations wher