7.7Non-normative: Encoder optimization, decoder speed improvement and cleanup, post filtering, loss concealment, rate control (0)
See notes on JCTVC-Q0077 (effectiveness of the HM Inter Search for Screen Content) and JCTVC-Q0147 (fast inter search method for screen content coding) and JCTVC-Q0148 (RExt Quantization rounding for RDPCM) and JCTVC-Q0056 (weighted prediction parameter optimization).
Joint meetings with the VCEG and MPEG parent bodies were held at the following times:
Mon. 31 March 1600–1800
Tue. 1 April 1600–1800
Thu. 3 April 1500–1630
Topics discussed and outcomes of these joint meetings are recorded as follows:
For HEVC version 1, the following is reported:
The verification testing of HEVC version 1 had been completed with good results, and a report of the outcome would be issued by the JCT-VC and its parent bodies.
Regarding, version 1 defect correction, the previous plan to correct the defect in the MinCR specification for the current high tier was confirmed (a relevant parent-level contribution was m33346).
Regarding the current range extensions work and the future screen content coding (SCC) extensions, various views were expressed in input contributions to the parent bodies on these projects and the appropriate relationship between them and the particular configurations of coding capabilities that should be specified in profiles and levels currently and in the near future (e.g., M32734 (summary of voting), M33347, M32712, JCTVC-Q0113 VCEG-AX12 / M32845, JCTVC-Q0133 / M32868, M33413, JCTVC-Q0051 / M32728, VCEG-AX14 / M33338, M33100, M33337, JCTVC-Q0212 / M33363, M32820, JCTVC-Q0186, M33048). The impact of this discussion on the planning for SCC and the range extensions is reflected below, especially in regard to the specification of a 4:4:4 8 b profile and the "intra block copy" coding feature.
For the screen content coding (SCC) CfP outcome, the following is reported:
The input report (VCEG-AX13 / M33474) of the formal subjective assessment of the submissions in response to the CfP was noted, along with the objective measurements, coding tools analysis, and other information gathered from the study of the submissions themselves (JCTVC-Q0239).
It was agreed that the responses to the joint CfP indicated that the HEVC standard should be extended to include additional coding capabilities for SCC and that additional profiles should be developed to include such technology.
It is anticipated that such profiles will include typical HEVC capabilities for coding camera-captured content as well as additional SCC-oriented coding features
The technical work for development of such SCC extensions should be conducted in the JCT-VC.
The development timeline was agreed such that the completion of the standardization process for the SCC extensions was estimated to occur around the end of 2015 or beginning of 2016, with ISO/IEC CD ballot likely to be issued in February 2015.
Decision: Issue a complete text containing range extensions and errata corrections (in integrated form) as an ISO/IEC FDIS as an output of the current meeting.
Decision: In consideration of new contributions for RExt and SCC indicating a potential lack of adequate maturity, some implementation difficulty, and a potental lack of adequate benefit on a sufficiently broad range of video content, the "intra block copy" coding feature will not be included in the RExt profile specification currently being finalized.
Remove the highest tier previously drafted for the 4:4:4 Intra 16 profile from the text to be produced
Define an all-intra 16 b profile with CABAC bypass alignment required to be enabled by encoders and with decoders not required to decode bitstreams in which CABAC bypass alignment is disabled. The maximum bit rates in each tier of the additional profile will be 12 times the bit rates in the corresponding tier of the 4:4:4 Intra 16 profile (and there will be two tiers, as in other profiles). The specification of this profile will be finalized at the meeting of July 2014 rather than at the current (Valencia, April 2014) meeting.
NOTE Post-meeting observation: Since decoders for this profile would not be required to decode bitstreams from any previously specified profiles, some other features should probably also be given the same treatment as CABAC bypass alignment in this new profile. This would include the modified Rice parameter adaptation rule, high-precision transform processing, and features that could be characterized as bug-fixes for version 1, such as extended-precision weighted prediction, the context for coding the transform skip flag, the rotation of transform skip blocks, large block-size transform skip. It seems less clear what should be done regarding RDPCM and intra smoothing disabling, but suggested by editors GJS and DF that decoders should support both modes for these.
Decision: For all-intra profiles, the CPB size constraint will correspond to 0.5 seconds of the maximum bit rate.
For the all-intra profiles, in the parent-level input contribution M33048, it had been suggested to make the "in loop" filtering processes mandatory for these profiles. After discussion, it was agreed to keep these processes optional in such profiles (although the picture hash SEI message should assume these processes had been applied).
Decision: Regarding the proposed specification of an SEI message to signal a rectangular frame packing arrangement (e.g., JCTVC-Q0256 and IT NB input in parent-level contribution M32734), various aspects of the proposed text were discussed, and it was ultimately agreed to include specification of such an SEI message in the RExt extensions specification. More detailed notes on the subject are found in the section of this report concerning JCTVC-Q0256.
Regarding colour-related aspects for the RExt specification (e.g., SEI and VUI), the actions and plans recorded elsewhere in this report on those topics were reviewed and confirmed as appropriate.
For the scalability extensions, the following is reported:
Various issues were discussed, particularly including JCT-VC and parent-level inputs M32735 (summary of voting), JCTVC-Q0188 / VCEG-AX11 / M33043, M33412, and plans and considerations relating to ROI scalability and the use of an interlaced base layer.
Parent-level input M33171 was noted in regard to a proposed requirement for chroma format scalability, and it was agreed that this should be considered a longer-term issue not for immediate action.
It was noted that a tentative conclusion had been reached in JCT-VC HLS study that the specification of a Monochrome 8 bit profile is needed for purposes of achieving adequate clarity of the specification of decoding requirement capabilities, so that monochrome (e.g. alpha) auxiliary pictures have something specified to conform to. This need was confirmed.
Regarding the 12 b profile proposed in Q0206 and WG 11 parent body document M33427, it was noted that 12 b operation has not been tested in JCT-VC. It was agreed that the subject should be further studied (in AHG 14) and a decision should be reached on the subject at the next meeting.
For 3D extensions, various topics were discussed. Such topics not directly relevant to JCT-VC are recorded in the JCT-3V report.
Regarding future work on HDR (high dynamic range) and WCG (wide colour gamut), e.g., the parent-level input contribution m32771, it was noted that MPEG is planning further study in this area and expected to determine in October 2014 or February 2015 whether significant new standardization work is needed for this.
Regarding the study of interlaced video coding with HEVC and the potential for further enhancing the performance of HEVC on interlaced video content by making core technology modifications specifically to address needs for coding interlaced video (e.g., including parent-level inputs M33407 and M33476), viewing of video content was conducted by the MPEG Requirements subgroup, and it was determined that the evidence was insufficient to identify a need for new technology development (e.g., new profiles) for this purpose. However, it would be desirable to conduct verification testing to confirm the compression capability improvement that already exists for interlaced video content for use of HEVC versus its predecessors. It was remarked that some study in this area had already been done (e.g., by a prior "4EVER" project). A mandate was given for a JCT-VC ad hoc group to study what has already been done in this area and identify what further is needed for performing such a verification test of HEVC capability.
Regarding still image coding using HEVC, the recent reports of the substantial effectiveness of HEVC for this purpose were noted (e.g., JCTVC-Q0229). Further study on the subject was noted to be planned – particularly in the MPEG parent body – and interest in the subject was also noted by VCEG.
