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Comment by cesarb | Hacker News Reader

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?

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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".

> 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.

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

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.

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