[Howto] play h265 (hevc) 10-bit video with hardware acceleration

recommendations:

#check, if VDPAU-API is working (h.265 = HEVC.MAIN decoder profile must be supported)
vpdauinfo

#check, if VA-API is working (h.265 'entrypoints' must be listed)
vainfo

problem:

vdpau-driver doesn’t support h.265 10-bit hardware-decoding yet. It falls back to software decoding and the cpu must convert 10-bit to 8-bit colors. (this is a heavy workload)

solution:

the va-driver supports h.265 10-bit hardware decoding, e.g. use the following command:

#movie.mp4 (h.265, 10bit colors, 3840x2160 resolution, yuv420p10)
mpv --hwdec=vaapi --vo=vaapi movie.mp4