US-12621421-B2 - Image data encoding/decoding method and apparatus

US12621421B2US 12621421 B2US12621421 B2US 12621421B2US-12621421-B2

Abstract

Disclosed are methods and apparatuses for decoding an image. A method includes receiving a bitstream obtained by encoding the image; dividing a first coding block into a plurality of second coding blocks; generating a prediction block of a second coding block based on syntax information obtained from the bitstream; and reconstructing the second coding block based on the prediction block and a residual block of the second coding block, the residual block being obtained by performing a dequantization and an inverse-transform on quantized transform coefficients from the bitstream. The first coding block has a recursive division structure. The first coding block is divided based on at least one of a quad tree division, a binary tree division or a triple tree division.

Inventors

Ki Baek Kim

Assignees

B1 INSTITUTE OF IMAGE TECHNOLOGY, INC.

Dates

Publication Date: 20260505
Application Date: 20240523
Priority Date: 20161004

Claims (3)

1 . A method of decoding a 360-degree image, the method comprising: receiving a bitstream obtained by encoding the 360-degree image; generating a predicted image with reference to syntax information acquired from the received bitstream; acquiring a decoded image by combining the generated predicted image with a residual image acquired by inversely quantizing and inversely transforming the bitstream; and reconstructing the decoded image to produce a 360-degree image corresponding to a projection format, wherein the generating of the predicted image comprises: obtaining a reference image acquired by restoring the bitstream and by performing image expansion on the reference image; and generating a predicted image with reference to the reference image on which the image expansion is performed, wherein the reference image on which the image expansion is performed includes an expansion region, wherein a size of the expansion region is determined as a value indicated by size information obtained from the bitstream, the size information comprises first width information on a left side of the expansion region and second width information on a right side of the expansion region, a syntax element for the first width information being different from a syntax element for the second width information, wherein sample values in the expansion region are determined according to a padding method selected among a plurality of padding methods including a first padding method which copies sample values of the reference image before the image expansion for the sample values in the expansion region and a second padding method which transforms sample values of the reference image before the image expansion for the sample values in the expansion region, and the padding method for the left side of the expansion region is determined separately from the padding method for the right side of the expansion region.
2 . A method of encoding a 360-degree image, the method comprising: generating a predicted image, syntax information for the predicted image being encoded into a bitstream; acquiring a residual image based on the predicted image; and encoding the residual image into the bitstream by transforming and quantizing the residual image, wherein the residual image and the predicted image being used to reconstruct a decoded image which is used to produce a 360-degree image corresponding to a projection format, wherein the generating of the predicted image comprises: obtaining a reference image among previous images and by performing image expansion on the reference image; and generating a predicted image with reference to the reference image on which the image expansion is performed, wherein the reference image on which the image expansion is performed includes an expansion region, wherein a size of the expansion region is determined as a value indicated by size information encoded into the bitstream, the size information comprises first width information on a left side of the expansion region and second width information on a right side of the expansion region, a syntax element for the first width information being different from a syntax element for the second width information, wherein sample values in the expansion region are determined according to a padding method selected among a plurality of padding methods including a first padding method which copies sample values of the reference image before the image expansion for the sample values in the expansion region and a second padding method which transforms sample values of the reference image before the image expansion for the sample values in the expansion region, and the padding method for the left side of the expansion region is determined separately from the padding method for the right side of the expansion region.
3 . A method of transmitting a bitstream that is generated by a method of encoding a 360-degree image, the method comprising: generating a predicted image, syntax information for the predicted image being encoded into a bitstream; acquiring a residual image based on the predicted image; encoding the residual image into the bitstream by transforming and quantizing the residual image; and transmitting the bitstream, wherein the residual image and the predicted image being used to reconstruct a decoded image which is used to produce a 360-degree image corresponding to a projection format, wherein the generating of the predicted image comprises: obtaining a reference image among previous images and by performing image expansion on the reference image; and generating a predicted image with reference to the reference image on which the image expansion is performed, wherein the reference image on which the image expansion is performed includes an expansion region, wherein a size of the expansion region is determined as a value indicated by size information encoded into the bitstream, the size information comprises first width information on a left side of the expansion region and second width information on a right side of the expansion region, a syntax element for the first width information being different from a syntax element for the second width information, wherein sample values in the expansion region are determined according to a padding method selected among a plurality of padding methods including a first padding method which copies sample values of the reference image before the image expansion for the sample values in the expansion region and a second padding method which transforms sample values of the reference image before the image expansion for the sample values in the expansion region, and the padding method for the left side of the expansion region is determined separately from the padding method for the right side of the expansion region.

Description

RELATED APPLICATIONS This application is a continuation application of U.S. patent application Ser. No. 17/073,225, filed Oct. 16, 2020, which is a continuation application of U.S. patent application Ser. No. 16/372,251, filed Apr. 1, 2019, which is a continuation application of the International Patent Application Serial No. PCT/KR2017/011144, filed Oct. 10, 2017, which claims priority to the Korean Patent Application Serial No. 10-2016-0127883, filed Oct. 4, 2016; the Korean Patent Application Serial No. 10-2016-0129383, filed Oct. 6, 2016; and the Korean Patent Application Serial No. 10-2017-0090613, filed Jul. 17, 2017. All of these applications are incorporated by reference herein in their entireties. TECHNICAL FIELD The present invention relates to image data encoding and decoding technology, and more particularly, to a method and apparatus for encoding and decoding a 360-degree image for realistic media service. BACKGROUND With the spread of the Internet and mobile terminals and the development of information and communication technology, the use of multimedia data is increasing rapidly. Recently, demand for high-resolution images and high-quality images such as a high definition (HD) image and an ultra high definition (UHD) image is emerging in various fields, and demand for realistic media service such as virtual reality, augmented reality, and the like is increasing rapidly. In particular, since multi-view images captured with a plurality of cameras are processed for 360-degree images for virtual reality and augmented reality, the amount of data generated for the processing increases massively, but the performance of an image processing system for processing a large amount of data is insufficient. As described above, in an image encoding and decoding method and apparatus of the related art, there is a demand for improvement of performance in image processing, particularly, image encoding/decoding. SUMMARY It is an object of the present invention to provide a method for improving an image setting process in initial steps for encoding and decoding. More particularly, the present invention is directed to providing an encoding and decoding method and apparatus for improving an image setting process in consideration of the characteristics of a 360-degree image. According to an aspect of the present invention, there is provided a method of decoding a 360-degree image. Here, the method of decoding a 360-degree image may include receiving a bitstream including an encoded 360-degree image, generating a predicted image with reference to syntax information acquired from the received bitstream, acquiring a decoded image by combining the generated predicted image with a residual image acquired by inversely quantizing and inversely transforming the bitstream, and reconstructing the decoded image into the 360-degree image according to a projection format. Here, the syntax information may include projection format information for the 360-degree image. Here, the projection format information may be information indicating at least one of an Equi-Rectangular Projection (ERP) format in which the 360-degree image is projected into a 2D plane, a CubeMap Projection (CMP) format in which the 360-degree image is projected to a cube, an OctaHedron Projection (OHP) format in which the 360-degree image is projected to an octahedron, and an IcoSahedral Projection (ISP) format in which the 360-degree image is projected to a polyhedron. Here, the reconstructing may include acquiring arrangement information according to region-wise packing with reference to the syntax information and rearranging blocks of the decoded image according to the arrangement information. Here, the generating of the predicted image may include performing image expansion on a reference picture acquired by restoring the bitstream, and generating a predicted image with reference to the reference picture on which the image expansion is performed. Here, the performing of the image expansion may include performing image expansion on the basis of partitioning units of the reference picture. Here, the performing of the image expansion on the basis of the partitioning units may include generating an expanded region individually for each partitioning unit by using the reference pixel of the partitioning unit. Here, the expanded region may be generated using a boundary pixel of a partitioning unit spatially adjacent to a partitioning unit to be expanded or using a boundary pixel of a partitioning unit having image continuity with a partitioning unit to be expanded. Here, the performing of the image expansion on the basis of the partitioning units may include generating an expanded image for a region where two or more partitioning units that are spatially adjacent to each other among the partitioning units are combined, using a boundary pixel of the combined region. Here, the performing of the image expansion on the basis of the partitioning units may include gener