vaapidecode: allow output to buffers from downstream pools (userptr)
Submitted by Gwenole Beauchesne
Hardware decoders will always use their native VA surface representation. However, if the downstream element supplies its own bufferpool, and that the VA driver supports userptr wrappings, then it would be possible to use VPP to transfer from that VA surface to the wrapper VA surfaced backed by userptr obtained from that downstream bufferpool.
That way, we could offer HW accelerated decode and transfer to user provided memory buffers in the most common formats, including RGBA.