[Cin] av1 hw decoding

[Andrea paz]

I am responding here because the title is more appropriate than in the
other thread.

> you can simply comment out line "remap_video_decoder libaom-av1=libdav1d" in
ffmpeg/decode.opts

Yes, hardware decoding with libaom works. There are no messages on the
terminal. The GPU
is only 8-21% busy but the CPU is only 2-6% busy.
However, if scrolling there are still freezes and artifacts; the
performance seems to me
similar to dav1d and so I don't think it is convenient to use libaom.

Note: again, until I deleted .bcast5, and started from 0, was left
with working libdav1d
instead of libaom.

If you have other ideas/tests for me to do, please let me know.