to activate video codec is not enough:
install mpv-rpi and ffmpeg-mmal from AUR, ffmpeg from extra repo, has --enable-omx only, to use mmal (mpeg video codec license mmal) i have to install from aur: ffmpeg-mmal and mpv-rpi, where there is
$this->bbcode_second_pass_code('', '--enable-mmal \
--enable-omx \
--enable-omx-rpi \
')
but i have to downgrade kernel and firmware and bootloader packages, or mpv will crash (but maybe is a problem in my system only), i dont know how to enable VC1 on ffmpeg, i suppose is another --enable... from PKGBUILD.
here is my latest downgrade working.
$this->bbcode_second_pass_code('', 'linux-raspberrypi-4.19.50-1-armv7h.pkg.tar.xz
linux-raspberrypi-headers-4.19.50-1-armv7h.pkg.tar.xz
raspberrypi-bootloader-20190611-1-any.pkg.tar.xz
raspberrypi-bootloader-x-20190611-1-any.pkg.tar.xz
raspberrypi-firmware-20190611-1-armv7h.pkg.tar.xz
')
.. to use mmal accel in mpv there is some line to add on mpv.conf
try to uncomment some of these lines and see what happens:
$this->bbcode_second_pass_code('', '# vo=rpi
# hwdec=mmal
# hwdec-codecs=mpeg4,h264,mpeg2
# hwdec-codecs=all
')
You should see hardware decoding on terminal when you run
$this->bbcode_second_pass_code('', 'mpv --vo=rpi --hwdec=mmal --hwdec-codecs=all /dev/sr0 # /dev/sr0 should be dvd usb device
')
(to check wich line to add on mpv.conf) run mpv --hwdec=help should be helpful to change options or mpv --vo=help ... and so on.
I dont know if vlc is ready for hardware acceleration, i know only how to use mpv. If there is a faster set up, let me know please.

ciao.