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HEVC and RExt use cases (requirements related)
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HEVC and RExt use cases (requirements related)15.0.0.1.1.1.1.1.129JCTVC-N0291 [AHG21] Best-effort decoding of 10-bit sequences: use cases, requirements and specification methods [D. Flynn, G. Martin-Cocher, D. He (RIM)] (Further discussed with presentation Fri. 2nd.) HEVC, like some other well-known codecs, contains profiles that accommodate the decoding of non-8-bit video sequences. In particular, HEVC contains a 10-bit profile that specifies 10-bit coded video sequences. In JCTVC-M0255, it was demonstrated that it is possible to re-purpose an existing 8-bit decoder design to decode 10-bit bitstreams. It was also reported that management of rounding in the decoder (e.g. round to even) can reduce the accumulation of decoder error to a lesser amount than might otherwise be expected. This contribution proposes a candidate requirements basis and use case information, summarizes the previous work, and suggests methods of text specification. The method was suggested to work better at low fidelity than at high fidelity. The proposal suggested also considering adding data within the bitstream to indicate some intention to enable this usage. Prior discussion
Further suggestions were:
In the described method, the processing is generally performed as if the decoding process used 10 b, but the reference picture storage and reference samples for intra prediction are 8 b, and then the result is rounded after adding prediction and residual, before applying deblocking and SAO, and parts of deblocking and SAO are adjusted to compensate for the differing granularity.
See also JCTVC-N0163. 15.0.0.1.1.1.1.1.130JCTVC-N0179 Selected medical imaging sequences for HEVC development [P. Amon, A. Hutter, U.-E. Martin, B. Heigl (Siemens)] [late] Discussed Thu 1st (GJS): This contribution proposes new test sequences from the medical domain for the development of HEVC, especially for the specification of range extensions. The proposed set contains 8-bit, 12-bit, and 16-bit monochrome image data as well as 8-bit RGB content. Sequences were not available yet. Anticipated copyright terms would allow only for use for the committee's development of standards. It was suggested for the contributor to allow use for promotion of the standards and research and publication of snapshots in academic publications as well.
Discussed Thu 1st (GJS): This document proposes two 4:4:4 game content sequences for use in HEVC Range Extensions development. The primary application represented by these sequences is multiplayer mobile cloud gaming. The format of these 10-second RGB sequences is 1280x720, 30fps, 8 bits per component. The sequences were written directly to files by the content-generation software. These test sequences were proposed for addition to SCC test set (which otherwise has 10 sequences). Suggested as being too easy: CAD waveform, PCB layout, CG Twist tunnel. It was agreed to drop all three of these from the usual tests – keep them available but drop them from usual testing. The contributor said that non-anti-aliased versions would also be provided (but we will focus on the anti-aliased ones for the test set). Other frame rates and resolutions may be possible to generate. These test sequences were available. Members were encouraged to experiment. We are likely to add to our SCC test set at next meeting.
(Reviewed in Track B Fri 26th (JO).) 15.0.0.1.1.1.1.1.132JCTVC-N0031 SCE1: Summary Report of SHVC Core Experiment on support for additional re-sampling phase shifts [E. Alshina, X. Li, J. Dong] This document summarizes the activities and test results performed in SCE3 on support for additional re-sampling filters. Two problems were investigated: enhancement and base layer picture misalignment and relative Luma and Chroma samples misalignment. Solving of both problems requires modification of re-sampling process beyond SHM2.0: additional re-sampling filters are needed. Two types of solutions were studied: fixed predetermined re-sampling filters with additional information about filters choice signalling (so-called category 1 tests) and variable coefficients (so-called category 1 tests). Tools have been evaluated on the test conditions defined in document JCTVC-M1101. Tools listed in the table below were evaluated in this CE. 4 related non-SCE contributions were submitted for this meeting. Non-SCE1 contributions are marked with * in the table below. Table: List of tested tools and cross-checks availability.
Following tables show the average data of AI, LDB, LDP and RA configurations. For the following table, simulations were performed where a phase shift occurs between BL and EL in downsampling, where SHM can only support zero phase shift due to its filters. Performance and complexity summary for tests on EL and BL pictures alignment.
From these results, it becomes evident that if a different phase would be used, the current SHM would suffer. The phase offset in downsampling was taken similar as in SVC, approximately 1/6 for 1.5X. No other phase shifts were tested. Upsampling used rounding to 1/4, 1/8, 1/16, and arbitrary/adaptive Series of tests with 1/4…1/16 accuracy for down-sampling filter phase shift signalling allows to identify relationship between performance and bits needed for down-sampling filter phase shift signalling. Graph on Fig. 2 shows dependency between size of side information signalling (horizontal axis) and gain achieved in non-ctc content (vertical axis). Blue dots show performance of tests with fixed coefficients; red dots – for adaptive filter solutions. No significant gain was observed beyond 1/8 sample precision.
In the last meeting, it was reported that SVC (which uses ½ pel phase shift, e.g. in 2x scalability) had a compression benefit from doing this. However, SVC does not allow signalling the downsampling phase. However, the following table shows that a deviation from the zero position in downsampling (as currently in SHM) is still the best solution in terms of performance Performance and complexity summary vs HM10.1 single layer.
From these results, it is reportedly evident that using another than zero phase position in downsampling would give benefit in terms of compression. In the discussion, the following applications are mentioned:
More evidence required included:
Does the definition of arbitrary phase come for free? Definitely not, as it requires implementation of additional filters at the decoder, signalling of side information. Defining the different phases is not per se necessary from the viewpoint of standardization (as it does not give benefit from the viewpoint of compression performance and memory usage), it would rather be beneficial for encoding devices. More evidence required about the need and benefits for these applications (current CE conditions did not have such applications in mind, could better be done in AHG) A more broad range of phase shifts of downsampling should be tested. Filters for all phases would be needed for arbitrary spatial scalability ratios, that would be included, the arbitrary phase could be implemented with almost no additional cost (is a matter of profiles). No study of arbitrary upsampling ratio performed so far. Further study on these aspects is necessary before any decision could be taken.
Current CTC assumes that the 4:2:0 chroma samples are horizontally aligned with each second luma sample, and vertically between a pair of luma samples (which is not known). 
The following results shows the performance when b is used in downsampling, and a in upsampling (worst case would be a to e). Therefore, slight loss occurs, but this is almost negligible. Further study was encouraged for:
May be tested only in AI.
15.0.0.1.1.1.1.1.133JCTVC-N0045 SCE1: Results of Test 1.1.3 on accurate chroma position alignment [X. Li, J. Chen, L. Guo, M. Karczewicz (Qualcomm), J. Dong, Y. Ye, Y. He (InterDigital), K. Ugur, J. Lainema (Nokia)] 15.0.0.1.1.1.1.1.134JCTVC-N0046 SCE1: Results of Test 1.2.1 on Adaptive Re-Sampling Filter [X. Li, W. Pu, J. Chen, M. Karczewicz (Qualcomm)] 15.0.0.1.1.1.1.1.135JCTVC-N0078 SCE1: Test 2.2 report [K. Minoo, D. Baylon] 15.0.0.1.1.1.1.1.136JCTVC-N0182 SCE1: Results of test 1.1 and 1.2 on sampling offset signalling [J. Dong, Y. Ye, Y. He (InterDigital), X. Li, J. Chen, L. Guo, M. Karczewicz (Qualcomm), K. Ugur, J. Lainema (Nokia)] 15.0.0.1.1.1.1.1.137JCTVC-N0308 SCE1: Verification of test 2.1 on picture and sequence level adaptive re-sampling filter [E. Alshina, A. Alshin (Samsung)] [late]
15.0.0.1.1.1.1.1.138JCTVC-N0193 SCE1: Cross-check for Test 2.2 on phase compensation by signalling filter coefficients at PPS with sample shift [J. Dong, Y. Ye (InterDigital)] 15.0.0.1.1.1.1.1.139JCTVC-N0225 SCE1: Cross-check for Test1.2, The accuracy of signaled up-sampling phase offset [K. Minoo, D. Baylon (Arris)] [late] 15.0.0.1.1.1.1.1.140JCTVC-N0226 SCE1: Cross-check for Test1.3, accurate Chroma position alignment [K. Minoo, D. Baylon (Arris)] [late] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
