twitch low latency playback issue
Categories
(Core :: Audio/Video: Playback, enhancement, P3)
Tracking
()
People
(Reporter: muumiperuna, Unassigned)
References
(Blocks 1 open bug)
Details
Attachments
(3 files)
twitchissues.png
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:135.0) Gecko/20100101 Firefox/135.0
Steps to reproduce:
view any stream from twitch https://www.twitch.tv/directory/all/tags/unity
enable Low Latency mode and Source quality in twitch player.
Actual results:
Video cycles between source quality to lowest resolution constantly and drops frames too. This started happening sometime last year (2024).
Screenshot comparison in Firefox vs. Chrome.
Expected results:
In other browsers (Chrome, Edge), low latency plays normally, no dropped frames.
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Comment 1•28 days ago
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The Bugbug bot thinks this bug should belong to the 'Core::Audio/Video: Playback' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.
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Comment 2•28 days ago
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Hi, uuxx
- Would you please attach the contents of your "about:support"? Use the "Copy text to clipboard" button and paste that text as an attachment to this bug.
- Is it possible for you to use https://mozilla.github.io/mozregression/ (you can use the GUI version of this tool) to bisect help identify the change that would have caused this issue for you?
still happening on 123.0a1 (2024-01-01) (64-bit) with mozregression.
i think its possible that twitch has changed something that breaks firefox..
there is another issue with certain streams https://webcompat.com/issues/149124 (only in firefox)
Tested on Edge and Chrome again, no issues.
New guess:
If low latency viewer has skipped frames,
edge survives it better, without dropping stream resolution, but firefox drops to lower resolution always?
Also noted, when firefox plays source quality, codec is "avc1.64002A,mp4a.40.2"
when it drops to lower quality, codec is "avc1.4D401F,mp4a.40.2" (not sure if related)
tested on 107.0a1 (2022-10-03) (64-bit, same issue.
attached new image with firefox and chrome running side by side,
firefox is failing to play in full resolution..
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Comment 7•15 days ago
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(In reply to uuxx from comment #4)
Hi uuxx, thanks for the report.
Also noted, when firefox plays source quality, codec is "avc1.64002A,mp4a.40.2"
when it drops to lower quality, codec is "avc1.4D401F,mp4a.40.2" (not sure if related)
These are H264 codec information:
- avc1.64002A: High Profile with Level: 4.2
- avc1.4D401F: Main Profile with Level: 3.1
The frame-dropping may happen when the video cannot keep up with the audio. According your about:support info, your machine should support both hardware and software H264 decoding. Hardware decoding should be fast enough. Does frame dropping issue only happen with certain audio devices like "Oculus Virtual Audio Device"? Can this be reproduced with your "Realtek Digital Output device" or "ROG PG278QR (NVIDIA High Definition Audio)"?
(In reply to C.M.Chang[:chunmin] from comment #7)
The frame-dropping may happen when the video cannot keep up with the audio. According your about:support info, your machine should support both hardware and software H264 decoding. Hardware decoding should be fast enough. Does frame dropping issue only happen with certain audio devices like "Oculus Virtual Audio Device"? Can this be reproduced with your "Realtek Digital Output device" or "ROG PG278QR (NVIDIA High Definition Audio)"?
I didnt notice any difference so far, but i'll test again on a different pc.
some additional comments, was looking at same stream in FF and chrome,
in FF latency seems to increase over time? Also FPS is not stable.
Firefox:
FPS is 28-32
Buffer Size: 3.43 sec.
Latency To Broadcaster: 5.54 sec.
Chrome:
FPS is stable at 30
Buffer Size: 1.87 sec.
Latency To Broadcaster: 2.12 sec.
(this is in twitch low latency mode)
Description
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