Raspberry Pi 3 hardware accelerated video playback

About how to play video with hardware video decode on RPi3 and a Wayland desktop environment.

Motivation🔗

• hardware video decode uses less CPU and is more power efficient
• old MMAL isn't supported now
  • everyone have switched to standard V4L2 APIs (see raspberrypi/userland)
• standard mpv shipped with ArchLinux ARM do support hardware video decode on RPi3, BUT:
  • need to use --hwdec=v4l2m2m-copy
  • only compatible with --vo=gpu on Wayland(Sway), not --vo=dmabuf-wayland

So, in order to play video smoothly on Wayland, run mpv --vo=gpu video.mp4, but CPU load will be very high. To play with lower CPU usage, use mpv --hwdec=v4l2m2m-copy --vo=gpu video.mp4, but the playback will be choky. None of them is ideal.

Solution🔗

Build mpv against rpi-ffmpeg which implements v4l2m2m(w/o -copy) for Raspberry Pi, and that will be compatible with dmabuf-wayland, which gives a decent performance.

So my procedure is:

• clone mpv-build
• run ./update in mpv-build's folder
• add rpi-ffmpeg as a remote for freshly cloned ffmpeg repository and switch to release/5.1/main(mpv requires ffmpeg 4.4 or later)
• add extra ffmpeg options to ffmpeg_options under mpv-build's folder(see content below)
• run ./build -j4 in mpv-build's folder
• then you can utilize hardware video decode with something like mpv --vo=dmabuf-wayland --hwdec=v4l2m2m video.mp4

Content for ffmpeg_options(not all necessary but I haven't tested it):

--enable-libx264
--enable-libmp3lame
--enable-libfdk-aac
--enable-libdrm
--enable-opengl
--enable-outdev=vout_drm
--enable-hwaccels
--enable-v4l2_m2m
--enable-nonfree
--enable-sand
--enable-v4l2-request

Appendix🔗

The hardware decode node for RPi3 is /dev/video10. To see supported formats, run v4l2-ctl --list-formats-out -d 10.