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6 September 2019 AV1 In-loop super-resolution framework
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The AV1 codec added a new in-loop super-resolution mode that allows a frame to be encoded at a lower resolution, and then super-resolved normatively to the full resolution, before updating the reference buffers. While encoding at lower resolution and super-resolving to a higher resolution is not a new concept, this is the first time such a mode has been normatively incorporated in a standardized video codec. To this end, AV1 has not only added support for across-scale motion prediction to allow predicting a lower resolution version of a frame from higher resolution reference buffers, but also made various simplifications to the super-resolving process itself after reconstruction to make it both software and hardware-friendly in implementation. Specifically, the super-resolving process in AV1 comprises of normative linear upscaling, followed by a restoration operation to recover the high frequencies using another AV1 tool called loop-restoration that includes a Wiener or Self-guided filter selected in a block switchable manner. Further, in order to enable a cost-effective hardware solution with limited line-buffers, this mode only allows the upscaling/downscaling operation to be horizontal.

In this paper, we provide the details of the super-resolution mode in AV1 and some results showcasing the benefits of the same.
Conference Presentation
© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Urvang Joshi, Debargha Mukherjee, Yue Chen, Sarah Parker, Adrian Grange, and Hui Su "AV1 In-loop super-resolution framework", Proc. SPIE 11137, Applications of Digital Image Processing XLII, 1113718 (6 September 2019);

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