| JCTVC-B114 [Z. Ma, A. Segall (Sharp Labs)] System for graceful power degradation
The contribution proposes a system that enables the low resolution decoding of a bit-stream without drift. The system consists of a buffer compression algorithm that reduces memory bandwidth for all devices, and a low resolution decoding mode that enables optional, lower power operation. We assert that this lowest power mode is beneficial for battery powered devices and additionally benefits devices with screen resolutions lower than the content resolution. To achieve our goal, we propose to store sub-sampled and compressed versions of reconstructed frames in the decoded picture buffer. We then store prediction and residual data to reconstruct the missing pixels. The result is buffer compression. Additionally, we allow encoders to selectively disable the residual correction for the missing pixels data and transmit the prediction component explicitly. As will be described in the document, this leads to a low resolution decoding functionality.
The basic idea is to be able for decoding either a low or high resolution version of a sequence, switchable on frame by frame basis
Use quincunx sampling for a low-resolution picture and a high-resolution residual. Compressed from 12 to 8 bit; in case where the residual is close to zero, it can also be skipped.
MC is then only applied on low resolution pixels. Also combination possible, i.e. decoding of full resolution, but MC and frame buffering only with low resolution.
Quincunx subsampling is performed without filtering; this can cause aliasing, which is removed by post processing (not in the loop)
It was remarked that quincunx sampling could also potentially introduce color artifacts
Resolution reduction adds another degree of freedom in memory compression. If this would come for free, it would be fine, but needs to be investigated whether this is true (also visually) for various sequences.
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