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Non-CE technical contributions (26)
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Non-CE technical contributions (26)
(Chaired by A. Vetro) 14.1.1.1.1.1.1.1.139JCT3V-G0035 VSP depth access simplification [T. Ikai (Sharp)] This proposal presents a simplification for VSP. Currently VSP applies to 8x4 and 8x4 block basis and access four depth values in each block. However it is asserted such a small block doesn’t need so many accesses and there is more efficient position for coding efficiency. This contribution proposes one position instead of four corners. The experiment result reportedly shows that the BD-rate gain is 0.07 %, 0.07 % and 0.05 % in video, total video and synthesis respectively. With the proposed change, it was asserted that the number of accesses per block is reduced from 4 to 1, but this depends on the implementation. The impact of this change on memory bandwidth and complexity relative to the entire design was not clear, e.g., considering data reuse. The position that was selected seems rather specific and appears to be tuned to the current test set. There was some concern on whether this generalizes to other test content. See additional notes below on G0036. 14.1.1.1.1.1.1.1.140JCT3V-G0179 Crosscheck on VSP depth access simplification (JCT3V-G0035) [Y.-W. Chen, J.-L. Lin (MediaTek)] [late]
This proposal presents a simplified VSP subblock decision. Currently subblock size of VSP is decided based on depth values except of AMP PU. This contribution proposes to further simplify the decision so that depth base decision is applied only to square PUs. With this simplification, the depth access in VSP subblock decision is the same as the DoNBDV depth access since the access point is completely the same (no additional, no less). The experiment result shows that the BD-rate gain is 0.0 %, 0.0 % and 0.0 % in video, total video and synthesis respectively. It was asserted by the proponent that the benefit of this proposal is that the number of access is reduced from 8 to 4. It was remarked that the corner samples that are used to determine the sub-PU division are used to determine the disparity in the current design. The proposed design removes the access to those corner samples for the deciding the division, but it still requires them to determine the disparity. G0035 proposes to reduce the number of samples to determine the disparity to just one sample per sub-PU. Considering the above, this proposal only makes sense in combination with G0035. An updated version of G0035 (of 01-16) intends to clarify benefit of combined simplification (G0035/0036) with more comprehensive analysis. In case of non-square PUs, the number of samples used is reduced from 4 to 1. The worst case is 8x8 PU where it needs to be decided whether a split into 4x8 or 8x4 is made. In the current process, the corner samples of the subblocks are additionally accessed, whereas the proposal suggests to make the decision only based on the 8x8 corner samples and some fewer samples of the 4x4 subblocks. It is claimed that the worst case number of memory accesses in this context is reduced by 25%. However, in an implementation, it is likely that all the samples are available in the current chunk of the cache, such that the saving of memory accesses may be minor. On the other hand, the choice of the additional samples (on a 2x2 grid) appears more irregular and requires a more complicated description in the draft. No action. 14.1.1.1.1.1.1.1.142JCT3V-G0180 Crosscheck on Simplified VSP subblock decision (JCT3V-G0036) [Y.-W. Chen, J.-L. Lin (MediaTek)] [late]
This contribution proposes a frame-level view synthesis prediction. In the proposed scheme, a forward warping based view synthesis is utilized in order to generate a synthesized picture and a hole map, which shows whether synthesized picture is available or not for each pixel. Based on the hole map, each CU is coded by either the normal scheme or the bypassed scheme. In the bypassed scheme, only prediction residuals are coded. Experiments reportedly show bit rate increase of 2.39% on average over all test sequences, but also show significant bit rate reduction for dependent view and total bit rate reduction of around 3% for GT_Fly and Shark sequences. Motivation: consider whether side views extrapolated from center view provide a good prediction with sufficient subjective quality. In the results, the QP values for coding the dependent texture view are increased by 2. One issue with the current design is that the parsing is dependent on the hole map. There may also be other ways to achieve the similar capability, e.g., new slice type that is a virtually decodable slice, or using an SEI message such as texture and depth view packing. Similar proposals were put forward in response to the CfP. With such an approach, PSNR is not likely a good measure of quality. No action, but proponents were encouraged to follow up with further study.
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