[cesarb]

How can I confirm whether Firefox is actually using hardware decode for videos on my machine for a given codec? Is there a magic keyword I should search for within the about:support page, or is it recorded somewhere else? Mine shows for instance "VP9_HW_DECODE default available", does this means it's using hardware decode for VP9, or merely that it might be possible for my Firefox version?

[padenot]

We've put a dedicated section called Media in about:support, it has decoding capabilities and other things such as audio IO informations.

If you find that it is not accurate, e.g. by cross-checking via other means, please open a ticket at https://bugzilla.mozilla.org/enter_bug.cgi, component "Audio/Video".

[cesarb]

> We've put a dedicated section called Media in about:support, it has decoding capabilities

I see, I hadn't found it when searching for the codec name because it only said something like "Information not available. Try again after playing a video." After opening a random YouTube video and refreshing about:support, it did show the hardware decoding information, and it was as I had expected given the hardware on this computer.

[shmerl]

At least with AMD GPU, an easy way to do it is to check usage of VCN.

Something like this (assuming your GPU index is 0):

    watch -n 1 sudo cat /sys/kernel/debug/dri/0/amdgpu_pm_info

You should see there:

    VCN: Enabled

If GPU accelerated video is being played.

I think you might need to set this flag to true in Firefox's about:config (or it might be not needed anymore):

    media.ffmpeg.vaapi.enabled

[mattst88]

On an Intel GPU, you can check the 'Video' percentage in `sudo intel_gpu_top` (from the igt-gpu-tools package) while playing a video.