1902781 - Youtube video switches from AV1 to VP9 for no reason.

Status: RESOLVED WORKSFORME

(Core :: Graphics, defect)

Description

[Manuel Grießmayr]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:127.0) Gecko/20100101 Firefox/127.0

Steps to reproduce:

Go watch this vid in 4K: https://www.youtube.com/watch?v=8BPxtvVJwhw on a Linux System.

Actual results:

Video type changes from AV1 to VP9 at 0:20.

Expected results:

Video should play in AV1 because I have the necessary hardware which is an AMD Radeon RX 6600.

Comment 1

[Manuel Grießmayr]

The issue is reproducible.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Graphics' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 3

[Manuel Grießmayr]

I am on Xubuntu 24.04 with Mesa 24.0.5.

Comment 4

[Ashley Hale [:ahale]]

Attachment: about:support on a Lubuntu 24.04 system with Radeon RX 6700 XT

Comment 5

[Ashley Hale [:ahale]]

I can't repro this here on Lubuntu 24.04 with Mesa 23.2.1-1-ubuntu3.1-22.04.2 (as shown in about:support), I have not tested yet on Mesa 24.0.5, that system has a Radeon RX 6700 XT so it should be similar, and about:support shows support for AV1 decoding in hardware.

What I did see in YouTube's Stats For Nerds (in the right click menu on the video) is that it was VP09 before I pressed play (autoplay is off by default) and buffered ~10 seconds or more of the video in that mode, then pressing play it showed that video format for those 10 seconds and switched to AV1, then I changed to 4K video quality from the dropdown, and it remained AV1 codec, I haven't seen it switch to VP09.

It's possible that my about:support differs from yours, do you mind attaching the text from about:support as that contains some important information on media decoding? To do so, click either of the copy to clipboard buttons at the top, which can be pasted into an attachment on this bug using Attach New File in the Attachments section above.

It is also possible that YouTube are experimenting with VP09 fallback under some circumstances, but I am not familiar with their logic for that - it would certainly make sense to stay on AV1 for 4K video as the bandwidth usage is lower (which is better from their perspective, even if it means software decoding is used).

Comment 6

[Manuel Grießmayr]

Attachment: about support.txt

Comment 7

[Manuel Grießmayr]

For me the video starts with AV1. Maybe this has to do with the Youtube settings. If you login into Youtube and go to the settings available in the sidebar there you find the category "playback and performance". I've set the setting "always prefer AV1".

Comment 8

[Manuel Grießmayr]

Also Youtube starts playing in 4K because Youtube remembers which resolution I preferred the last time in the last video.

Comment 9

[Darkspirit]

AMD VAAPI (bug 1837140) is affected by bug 1902227. May or may not be related.

Comment 10

[Manuel Grießmayr]

@Darkspirit Seems unrelated because I am on Mesa 24.0.5.

Comment 11

[Manuel Grießmayr]

@Ashley Hale [:ahale]: Would you mind if you can try to reproduce this bug with your Lubuntu system?
https://bugzilla.mozilla.org/show_bug.cgi?id=1900215
Many thanks!