JCTVC-M0262 Crosscheck: AHG-17: complexity and performance analysis of different length up-sampling filters in SHM1.0 [W. Pu (Qualcomm)] [late]
JCTVC-M0051 AHG12: Low Complexity Resampling Filters Forfor SHVC [W. Dai, M. Krishnan, P. Topiwala (FastVDO)]
In place of the existing 8-tap luma and 4-tap chroma upsampling filters in the current SHVC model, this contribution proposes 6-tap luma and 4-tap chroma upsamplers. In this test, the downsampler has not been altered, and the proponent asserted that there is no need to compare performance on the low-resolution signal. The proponent reported the compression performance degradation relative to the 8/4-tap reference filters, which for the test cases was reportedly: (0.7%, 0.8%, 0.9% for AI-2X); (0.4%, 0.5%, 0.6% for RA-2X); (0.1%, 0.6%, 0.7% for LDP-2X).
The filters were primarily designed for the 2X scalability case.
M0088 was noted to be closely related.
The contributor asserted that gain might be achieved if a different downsampling filter is used (a filter selected to be matched to the upsampling filter), but did not have test results for such usage.
The contributor did not advocate adoption at this time, and had primarily brought the contribution for information purposes at this stage.
A participant commented that shortening the filter does not really help average complexity by a significant amount and does not help worst case memory bandwidth at all – since the worst case does not use the upsampling filter.
The contributor suggested that co-design of adaptive downsampling and upsampling could provide some benefit and indicated a desire for further study of that topic. The group encouraged further study of adaptive techniques.
It was remarked that currently SHVC only supports 1.5x and 2x scalability, and questioned whether we should remove this limitation, and it was noted that this issue is addressed in some other contributions.
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