Search

EP-4122199-B1 - HIGH LEVEL SYNTAX FOR VIDEO CODING AND DECODING

EP4122199B1EP 4122199 B1EP4122199 B1EP 4122199B1EP-4122199-B1

Inventors

  • LAROCHE, GUILLAUME
  • OUEDRAOGO, Naël
  • ONNO, PATRICE

Dates

Publication Date
20260513
Application Date
20210317

Claims (5)

  1. A method of decoding a bitstream, the bitstream comprising (i) video data corresponding to one or more slices in a picture, (ii) a picture header syntax structure, and (iii) a slice header, the method comprising: parsing one or more syntax elements, wherein when a first flag decoded from the slice header indicates that the picture header syntax structure is present in the slice header, subpicture information is not decoded and a value of a second flag, in a sequence parameter set of the bitstream, indicating whether the subpicture information is present is restricted to a value of 0 indicating that the subpicture information is not present, and wherein the picture header syntax structure being present in the slice header is indicative of a picture to be decoded containing only one slice; and decoding said bitstream using said one or more syntax elements, wherein the subpicture information comprises an ID of a subpicture, wherein the ID of the subpicture is decoded from the slice header dependent upon a value of the second flag in the sequence parameter set, and wherein the ID of the subpicture is not decoded from the slice header when (a) a third flag indicates that a raster scan slice mode is enabled, (b) a number of tiles in a picture is greater than one, and (c) a syntax element indicates that a number of tiles in a slice is equal to a number of tiles in the picture.
  2. A method of encoding video data into a bitstream, the bitstream comprising (i) video data corresponding to one or more slices in a picture, (ii) a picture header syntax structure, and (iii) a slice header, the method comprising: encoding one or more syntax elements into the bitstream, wherein when a first flag in the slice header indicates that the picture header syntax structure is present in the slice header, subpicture information is not encoded and a value of a second flag in a sequence parameter set of the bitstream, indicating whether the subpicture information is present is restricted to a value of 0 indicating that the subpicture information is not present, and wherein the picture header syntax structure being present in the slice header is indicative of a picture to be decoded containing only one slice; and encoding a slice into the bitstream, wherein the subpicture information comprises an ID of a subpicture, wherein the ID of the subpicture is encoded into the slice header dependent upon a value of the second flag in the sequence parameter set, and wherein the ID of the subpicture is not encoded into the slice header when (a) a third flag indicates that a raster scan slice mode is enabled, (b) a number of tiles in a picture is greater than one, and (c) a syntax element indicates that a number of tiles in a slice is equal to a number of tiles in the picture.
  3. A device comprising a decoder configured to perform the method of claim 1.
  4. A device comprising an encoder configured to perform the method of claim 2.
  5. A computer program which upon execution causes the method of any of claims 1 or 2 to be performed.

Description

Field of invention The present invention relates to video coding and decoding, and in particular to the high level syntax used in the bitstream. Background Recently, the Joint Video Experts Team (JVET), a collaborative team formed by MPEG and ITU-T Study Group 16's VCEG, commenced work on a new video coding standard referred to as Versatile Video Coding (VVC). The goal of VVC is to provide significant improvements in compression performance over the existing HEVC standard (i.e., typically twice as much as before) and to be completed in 2020. The main target applications and services include - but not limited to - 360-degree and high-dynamic-range (HDR) videos. In total, JVET evaluated responses from 32 organizations using formal subjective tests conducted by independent test labs. Some proposals demonstrated compression efficiency gains of typically 40% or more when compared to using HEVC. Particular effectiveness was shown on ultra-high definition (UHD) video test material. Thus, we may expect compression efficiency gains well-beyond the targeted 50% for the final standard. The JVET exploration model (JEM) uses all the HEVC tools and has introduced a number of new tools. These changes have necessitated a change to the structure of the bitstream, and in particular to the high-level syntax which can have a impact on the overall bitrate of the bitstream. Summary The present invention relates to an improvement to the high level syntax structure, which leads to a reduction in complexity and/or signalling without any significant degradation in coding performance. In a first aspect that is not claimed there is provided a method of decoding video data from a bitstream, the bitstream comprising video data corresponding to one or more slices, the decoding comprising: parsing one or more syntax elements, and not permitting use of a subpicture and/or parsing of subpicture information when at least one syntax element indicates that a picture to be decoded contains one slice; and decoding said bitstream using said syntax elements. In a further aspect that is not claimed there is provided a method of decoding video data from a bitstream, the bitstream comprising video data corresponding to one or more slices, the decoding comprising: parsing one or more syntax elements, and not permitting use of a subpicture and/or parsing of subpicture information in combination with at least one syntax element that indicates that a picture to be decoded contains only one slice; and decoding said bitstream using said syntax elements. In a yet further aspect that is not claimed there is provided a method of decoding video data from a bitstream, the bitstream comprising video data corresponding to one or more slices, said bitstream being constrained so that in a case where the bitstream includes a syntax element having a value indicating that a picture to be decoded contains only one slice, the bitstream also includes a syntax element having a value indicating that no subpicture is used and/or that no subpicture information is present for the picture, the method comprising decoding said bitstream using said syntax elements. This avoids inconsistency in bitstreams. Specifically, a picture which contains subpictures has several slices. If the picture contains only one slice it is a picture which contains only one subpicture. Further, this simplifies the parsing of the slice header for some implementations. The method may further comprise restricting the value of a syntax element indicating the presence of a subpicture to a value indicating that no subpicture is used when at least one syntax element indicates that a picture to be decoded contains one slice. The syntax element indicating the presence of a subpicture may comprise a flag indicating whether subpicture information is present. The syntax element indicating that the picture to be decoded contains one slice may comprise a picture header in slice header syntax element, wherein the picture header being signalled in the slice header is indicative of the picture containing one slice. The at least one syntax element indicating that picture to be decoded includes one slice may include a syntax element indicating that a raster scan slice mode is enabled, may include a syntax element indicating a number of tiles in a picture that is greater than one, and may include a syntax element indicating number of tiles in the slice that is equal to the number of tiles in the picture. In a second aspect according to the invention, there is provided a method of decoding video data from a bitstream, as defined in claim 1. In a third aspect that is not claimed, there is provided a method of decoding video data from a bitstream, the bitstream comprising video data corresponding to one or more slices, the decoding comprising: parsing one or more syntax elements, and not permitting the colour planes of a colour picture to be separated when the picture contains only one slice; and decoding said bitstream usi