Mesa 24.1 Enables AV1 LTR Encode Support For RDNA3 GPUs With VCN4

Building upon the existing AV1 encode support for RDNA3 GPUs within the Mesa RadeonSI Gallium3D driver, AV1 Long-Term Reference "LTR" support is now enabled within Mesa 24.1.

For Radeon GPUs with Video Core Next 4 (VCN4) IP that is the Radeon RX 7000 series, there is now support in Mesa Git for AV1 Long-Term Reference (LTR) support as the latest video encode enhancement. AV1 LTR support can help enhance quality and efficiency of the video encoding.

"Add vcn4 av1 long term reference support.

So that frames can be controlled from application side to refer to the identified reference, which usually could provide better coding efficiency in the case of scene chagne back and forth, just it needs to identify and mark these frames before using them.

We assume 2 long term reference frames should be good in a key frame period, and these long term references can be overwritten by marking new ones."

See this merge request for more details if interested. This code is in Mesa 24.1 that will be released as stable in Q2.