Organisation internationale de normalisation

SCC text development (4)

1.1.1.1.1.1.1.1.15JCTVC-U0038 Proposed editorial improvements to HEVC Screen Context Coding Draft Text 3 [R. Joshi (Qualcomm), J. Xu (Microsoft), S. Liu (MediaTek), Y. Ye (InterDigital)] [late]

(Consideration of this topic was chaired by GJS on Sunday 06-21, 17:30-18:00.)

For the first section of the document:

In the discussion, it seemed that the indexing for palette_transpose_flag is not needed. The editors were also requested to review indexing for merge index and CBF in regard to indexing. In any case, this is just an editorial matter.

Decision (Ed.): Editorial input delegated to the editors.

Second section: Basis text, forgotten DRAP and coded region completion SEI messages, ticket #1388 text integration error (also see JNB comment).

Decision (Ed.): Agreed as editorial issues to be fixed by the editors.

Third section:

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  IBC usage relationship to IRAP pictures? IRAP pictures allow P and B slices that use IBC, and it previously during the meeting, it was agreed to also allow traditional I slices when IBC is enabled.
  
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  Is IBC referencing prohibited for biprediction? Addressed previously during the meeting, this has been fixed. Referencing for bipred (in either or both lists) will be allowed.
  
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  Should the definition of I slice exclude IBC usage? There was previously a CU-level flag to select between IBC and ordinary intra, which was removed as part of the "unification" effort. See the notes for U0079. After the action taken in response to U0079, the definition of "I slice" excludes IBC, but an IRAP picture can contain I, P and B slices (in which the only picture that is used for reference is the current picture).
  

1.1.1.1.1.1.1.1.16JCTVC-U0055 High-level syntax refinement in monochrome signalling [C. Gisquet, G. Laroche, P. Onno (Canon)]

(Consideration of this topic was chaired by GJS on Tuesday 06-23, 12:45-13:00.)

During the editorial integration of JCTVC-T0048, related to palette syntax in the PPS SCC extension, support for monochrome and bit depths higher than 8 bits was considered and added. However, it is asserted this syntax may cause nonsensical signalling. This contribution proposes a modification of the PPS-level syntax to make the monochrome information more generic to address this issue. Specifically, the flag monochrome_palette_flag is proposed to be removed and a monochrome_flag is proposed to be added, keeping the previous meaning of monochrome_palette_flag, but also impacting the signalling of residual adaptive colour transform syntax. It is asserted this solves such ambiguity as having monochrome palette entries while ACT is active.

In the discussion, it was commented that the change does not seem really necessary and makes the syntax more logically complicated.

No action was taken on this.

In the discussion, it was remarked that we have SPS enabling flags for most new features, but not for the ACT. However, it was also noted that CCP signalling is the same.

1.1.1.1.1.1.1.1.17JCTVC-U0092 Draft Text modifications on palette [P. Lai, J. Ye, J. Kim, X. Xu, S. Liu, S. Lei (MediaTek)]

(Consideration of this topic was chaired by GJS on Tuesday 06-23, 13:00-13:10.)

This contribution presents modifications to the HEVC SCC Draft Text related to palette coding. The modifications are asserted to: 1) Fix errors in the draft text, 2) Resolve mismatches between SCM software and draft text, 3) Remove parts that are not referred to. In the second version of the document, two modifications are added to reflect other issues discussed during the meeting in relation to U0089.

For section 1.5, it was agreed that this constraint is needed. Editors may determine the way it is expressed.

Decision (Ed.): This is purely editorial and adding constraints that are necessary for sensibility. This is delegated to the editors.

1.1.1.1.1.1.1.1.18JCTVC-U0110 Bug fixes and cleanup for the text of palette mode in HEVC SCC draft [Y.-J. Chang, J.-S. Tu, C.-C. Lin, C.-L. Lin (ITRI)]

(Consideration of this topic was chaired by GJS on Tuesday 06-23, 13:10-13:20.)

This contribution presents bug fixes and cleanup issues for the palette mode in HEVC screen content coding draft 3. It is reported that a mismatch of coordinate scales between PaletteEscapeVal[ cIdx ][ xC ][ yC ] and recSamples[ x ][ y ] occurrs when the chroma format is not 4:4:4. This contribution provides two options to fix this bug: the first option is by modifying the syntax, and the second option is by modifying the decoding process of the reconstruction. Additionally, ctxInc of palette_run_type_flag was reportedly assigned to an undefined number.

The first part concerns PaletteEscapeVal. In the discussion, it was said that U0038 may already take care of this.

The second part of the contribution was addressed in 1.4 of U0092.

Decision (Ed.): In any case, this is purely editorial, and is delegated to the editors.

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