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EP-4738825-A2 - HIGH LEVEL SYNTAX FOR VIDEO CODING AND DECODING

EP4738825A2EP 4738825 A2EP4738825 A2EP 4738825A2EP-4738825-A2

Abstract

The disclosure relates to a method of decoding video data from a bitstream, the bitstream comprising video data corresponding to one or more slices. The bitstream comprises a picture header comprising syntax elements to be used when decoding one or more slices, and a slice header comprising syntax elements to be used when decoding a slice. The decoding comprises parsing, in the picture header at least one syntax element indicating whether a decoding tool may be used in the picture. When the decoding tool is used in the picture, at least one APS ID related syntax element is parsed for the decoding tool in the picture header. The decoding also comprises parsing, in a slice header, at least one syntax element indicating whether the decoding tool is to be used or not for that slice prior to syntax elements relating to other decoding tools. A bitstream is decoded using said syntax elements. Related encoding methods, devices and computer programs are also disclosed.

Inventors

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

Assignees

  • Canon Kabushiki Kaisha

Dates

Publication Date
20260506
Application Date
20210226

Claims (5)

  1. A method of decoding video data from a bitstream, the bitstream comprising video data corresponding to one or more slices, wherein the bitstream comprises a picture header comprising syntax elements to be used when decoding a picture including one or more slices, and a slice header comprising syntax elements to be used when decoding a slice, the method comprising: parsing, from the picture header, at least one syntax element indicating whether a decoding tool of Luma Mapping with Chroma Scaling, LMCS, is enabled for the picture; parsing, from the picture header, at least one syntax element indicating whether a decoding tool of Scaling List is enabled for the picture; when the decoding tool of LMCS is enabled for the picture, parsing, from the picture header, at least one syntax element related to an ID of an LMCS Adaptation Parameter Set, APS, for the decoding tool of LMCS; when the decoding tool of Scaling List is enabled for the picture, parsing, from the picture header, at least one syntax element related to an ID of a Scaling List Adaptation Parameter Set, APS, for the decoding tool of Scaling List; when the decoding tool of LMCS is enabled for the picture, parsing from a slice header at least one syntax element indicating whether the decoding tool of LMCS is to be used for the slice immediately after a syntax element related to an ID of an Adaptive Loop Filter, ALF, APS in the slice header when the ALF tool is enabled for the slice, and prior to syntax elements related to one or more decoding tools; when the decoding tool of Scaling List is enabled for the picture, parsing, from the slice header, at least one syntax element indicating whether the decoding tool of Scaling List is to be used for the slice, immediately after the at least one syntax element indicating whether the decoding tool of Luma Mapping with Chroma Scaling, LMCS, is to be used and prior to syntax elements related to one or more decoding tools, the one or more decoding tools including the decoding tool of SAO; and decoding the video data from the bitstream using said syntax elements.
  2. A method of encoding video data into a bitstream, the bitstream comprising video data corresponding to one or more slices, wherein the bitstream comprises a picture header comprising syntax elements to be used when decoding a picture including one or more slices, and a slice header comprising syntax elements to be used when decoding a slice, the method comprising: encoding, in the picture header, at least one syntax element indicating whether a decoding tool of Luma Mapping with Chroma Scaling, LMCS, is enabled for the picture; encoding, in the picture header, at least one syntax element indicating whether a decoding tool of Scaling List is enabled for the picture; when the decoding tool is enabled for the picture, encoding in the picture header, at least one syntax element related to an ID of LMCS Adaptation Parameter Set, APS, for the decoding tool of LMCS; when the decoding tool of Scaling List is enabled for the picture, encoding, in the picture header, at least one syntax element related to an ID of a Scaling List Adaptation Parameter Set, APS, for the decoding tool of Scaling List; when the decoding tool of LMCS is enabled for the picture, encoding in a slice header at least one syntax element indicating whether the decoding tool of LMCS is to be used for the slice immediately after a syntax element related to an ID of Adaptive Loop Filter, ALF, APS in the slice header when the ALF tool is enabled for the slice, and prior to syntax elements related to one or more decoding tools; and when the decoding tool of Scaling List is enabled for the picture, encoding, in the slice header, at least one syntax element indicating whether the decoding tool of Scaling List is to be used for the slice, immediately after the at least one syntax element indicating whether the decoding tool of Luma Mapping with Chroma Scaling, LMCS, is to be used and prior to syntax elements related to one or more decoding tools, the one or more decoding tools including the decoding tool of SAO.
  3. A device for decoding video data from a bitstream, the decoder comprising means configured to perform the method of claim 1.
  4. A device for encoding video data into a bitstream, the encoder comprising means configured to perform the method of claim 2.
  5. A computer program comprising instructions which, when the program is executed by a computer, causes the computer to carry out the method of claim 1 or 2.

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. One significant change to the high-level syntax is the introduction of a 'picture header' into the bitstream. A picture header is a header specifying syntax elements to be used in decoding each slice in a specific picture (or frame). The picture header is thus placed before the data relating to the slices in the bitstream, the slices each having their own 'slice header'. This structure is described in more detail below with reference to Figure 6. Document JVET-P0239 of the 16th Meeting: Geneva, CH, 1-11 October 2019, titled 'AHG17: Picture Header' proposed the introduction of a mandatory picture header into VVC, and this was adopted as Versatile Video Coding (Draft 7), uploaded as document JVET _P2001. However, this header has a large number of parameters, all of the which need to be parsed in order to use any specific decoding tool. Document JVET-Q0379 of the 17th Meeting: Brussels, BE, 7-17 January 2020, titled 'AhG9: On the position of APS Ids in Picture Header' proposed to move the LMCS APS ID and Scaling list APS ID up to a higher position in the picture header and to move the ALF APS ID up to a higher position in the picture header or slice header. Document JVET-Q2001-vD, being the Versatile Video Coding (Draft 8) discloses, when the decoding tool of LMCS is enabled for the picture, signalling in the slice header a syntax element indicating whether the decoding tool of LMCS is to be used for the slice. SUMMARY The present invention relates to an improvement to the structure of the picture header to simplify this parsing process, which leads to a reduction in complexity without any degradation in coding performance. In particular, by setting syntax elements relating to APS ID information at the beginning of the picture header these elements can be parsed first, which may preclude the need to parse the remainder of the header. Similarly, in the case that there are syntax elements relating to APS ID information in the slice header, these are set at the beginning of the slice header. In one example, it is proposed to move the syntax elements related to the APS ID at an early stage of the Picture header and Slice header. The aim of this modification is to reduce the parsing complexity for some streaming applications that need to track the APS ID in the Picture header and Slice header to remove unused APS. The proposed modification has no impact on the BDR performance. This reduces the parsing complexity for streaming applications where the APS ID information may be all that is required from the header. Other streaming-related syntax elements may be moved towards the top of the header for the same reason. It should be appreciated that the term 'beginning' does not mean the very first entry in the respective header as there may be a number of introductory syntax elements prior to the syntax elements relating to APS ID information. The detailed description sets out various examples, but a general definition is that the syntax elements relating to APS ID information are provided prior to syntax elements relating to decoding tool. In one particular example, the syntax elements related to the APS ID of ALF, LMCS and Scaling list are set just after the poc_msb_val syntax element. According to a first aspect of the invention there is provided a method of decoding video data from a bitstream, the bitstream comprising video data corresponding to one or more slices. The bitstream comprises a picture header comprising syntax elements to be used when decoding one or more slices, and a slice header comprising syntax elements to be used when decoding a slice. The decoding