Video Acceleration on Gentoo

Posted:: 2023-09-27

Over the past few months, I have found myself gradually spending more time on watching Youtube videos, both for entertainment and learning. I usually watch them on my laptop, which is equipped with an integrated GPU - AMD Radeon Vega 8. This got me thinking about how I can take advantage of it to reduce CPU load.

The media players that I use the most are Firefox and MPV (for watching downloaded Youtube videos). According to the list of video acceleration support across different applications [1], the only method supported by both of them is VA-API, which is an open source application programming interface that allows applications such as VLC media player or GStreamer to use hardware video acceleration capabilities, usually provided by the graphics processing unit (GPU) [2].

Setting up Gentoo Portage

In order to enable VA-API for an AMD GPU, the driver "radeonsi" should be added to the list of video cards [3]:

# ed /etc/portage/make.conf
a
VIDEO_CARDS="amdgpu radeonsi"
.
wq

Also, for programs/applications, such as Firefox and MPV, that support VA-API, the USE flag "vaapi" can be enabled globally [4]:

# ed /etc/portage/make.conf
a
USE="vaapi"
.
wq

Then, update the whole system to apply these changes:

# emerge -av --update --deep --newuse @world

From now on, VA-API has been enabled system-wide. let's then configure VA-API for specific programs/applications.

Configuring MPV

To enable VA-API in MPV, either add hwdec-vaapi to its configuration file, or use the option --hwdec=vaapi while launching it:

Enable VA-API through the configuration file
$ ed ~/.config/mpv/mpv.conf
a
hwdec=vaapi
.
wq

Enable VA-API through the command option
$ mpv --hwdec=vaapi <VIDEO>

To check if VA-API is enabled in MPV, play a video and press the key "i" to view its running details. If it shows "hwdec: vaapi" on the top, then VA-API is enabled:

Configuring Firefox

To enable VA-API in Firefox, open the page about:config, and make sure the below two options are set to true:

gfx.webrender.all             true
media.ffmpeg.vaapi.enabled    true

Note

Strangely, I couldn't find the option media.ffmpeg.vaapi.enable in my Firefox. After channelling my Google-fu, I discovered that:

For ESR, 115 needs the hwcaccel wayland USE flags enabled to get hardware acceleration. X and wayland can be enabled simultaneously.

Since 116, the wayland USE flag isn't needed to get hardware acceleration on supported cards for Rapid. 116 was fixed to have hardware acceleration without wayland support. [5]

As my current version of Firefox was ESR 102, I had to add additional USE flags hwaccel and wayland, and rebuild Firefox:

# ed /etc/portage/package.use/firefox
a
www-client/firefox hwaccel wayland
.
wq
# emerage -av www-client/firefox

To check if Firefox is working with VA-API, run the following command, and if there is any output showing on the screen, then VA-API is enabled:

$ MOZ_LOG="PlatformDecoderModule:5" firefox 2>&1 | grep "VA-API"

check whether VA-API is enabled in Firefox

Thanks for reading :)