Mesa 21.0 Adds Radeon HEVC SAO Encode Support

For the "Video Core Next 2" hardware like Navi as well as Renoir APUs, HEVC "sample adaptive offset" support has landed in Mesa 21.0.

VCN 2.0 initially came with Navi 1x and a feature now being exposed in the Mesa 21.0 Radeon video encode code is support for HEVC/H.265 sample adaptive offset, or SAO for short. As explained at IEEE.org, Sample Adaptive Offset for HEVC is a in-loop filtering technique to reduce sample distortion. From that published data, "it is reported that SAO achieves on average 3.5% BD-rate reduction and up to 23.5% BD-rate reduction with less than 1% encoding time increase and about 2.5% decoding time increase under common test conditions of HEVC reference software version 8.0."

With this commit to Mesa 21.0 for the open-source Radeon Linux driver there is support for HEVC SAO during the GPU-accelerated encode for VCN2 and newer. Yes, this also includes HEVC SAO enabled for CDNA "Arcturus" on VCN2.5 and the Radeon RX 6000 "Navi 2" on the latest VCN3 block.

On the other side of the table, NVIDIA has been supporting HEVC SAO with their proprietary driver stack and NVENC interface since Pascal.