1971368 - Problems with some videos buffering or stuttering on YouTube when logged in

Status: UNCONFIRMED

(Core :: Audio/Video: Playback, defect)

Description

[Lara Hansen]

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:139.0) Gecko/20100101 Firefox/139.0

Steps to reproduce:

Ubuntu 24.04, AMD Ryzen 5900X, NVIDIA RTX 4070 SUPER, 32GB RAM

1. Navigate to any of these videos on YouTube: https://www.youtube.com/watch?v=ZT-C-Fn6GoQ https://www.youtube.com/watch?v=jBTq2CWwGkg https://www.youtube.com/watch?v=sc1yZr4jtxo
2. Attempt playback at 1080p60 or above.

Actual results:

After about 5 seconds of playback, the video begins to buffer or stutter. The problem seems to affect these videos in particular. All of these videos are encoded with AV1, however other videos (such as this one: https://www.youtube.com/watch?v=DlgWsFJScU8) which are also encoded with AV1 at 1080p do not have stuttering or buffering issues. This problem does not appear to occur with videos encoded with VP9 at any resolution, and only occurs on YouTube (I tried sample AV1 and VP9 footage playback on other websites at 1080p and 1440p and no issues occurred during playback on those sites). I also tried this on a new Firefox profile and the same issues occurred. This issue also does not occur under Windows, nor under any other browser (tried Brave and Chrome).

Expected results:

Expected playback to be smooth across all videos at all resolutions.

Comment 1

[Karl Tomlinson (:karlt)]

Thank you for the report. I haven't been able to reproduce with mozregression --repo release --launch 139.0 on an Intel Linux system.

Does toggling media.hardware-video-decoding.enabled to false workaround the stuttering?

Does a build from https://www.mozilla.org/en-US/firefox/new/ show the same stuttering?

A profile with media logging would identify more about what is happening. See bug 1935757 comment 2.

Comment 2

[Lara Hansen]

After more testing, I found that the issue seems to stop if I am logged out of my Google account. For some reason, being logged in causes YouTube to throttle the connection speed, on any browser. Signing out fixed the issue. I have since reported this to Google, and am awaiting their response.

Comment 3

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

The severity field is not set for this bug.
:jimm, could you have a look please?

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