Bug 16810

Summary:	Firefox YouTube videos occasionally freeze while audio keeps playing
Product:	Mageia	Reporter:	Davide Nifosi <ita84>
Component:	RPM Packages	Assignee:	Thierry Vignaud <thierry.vignaud>
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	Normal	Keywords:	NEEDINFO
Version:	Cauldron
Target Milestone:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Source RPM:	firefox	CVE:
Status comment:
Attachments:	Last 50000 line of Firefox strace output around the time of a freeze

Description Davide Nifosi 2015-09-23 12:56:19 CEST

Description of problem:
Whenever I play a video on YouTube with Firefox, the video sometimes freezes but the audio keeps playing; if I move the pointer (only while over the Firefox window) or press a key the video catches up. This happens at random and often multiple times for a single video. It's like the video is playing but the image isn't refreshed.

This has also happened to be when playing video files with SMPlayer, but only with full screen. Not sure if related, but at about the same time Firefox started doing this, the progress bar pop-ups in Rpmdrake Update start off as completely black windows (only on the inside), and start showing their content only a few seconds later.

I've tried enabling and disabling Firefox hardware acceleration, it doesn't seem to change anything. YouTube is set to use HTML5 videos. This problem doesn't occur with the Vivaldi browser (Chromium-based).

My laptop has an Intel Sandy Bridge i5 (it has a discrete Radeon card, but it's not in use).

How reproducible:
It's random, but it happens pretty often with any YouTube video.

Steps to Reproduce:
1. Open any sufficiently long YouTube video (sometimes it only happens after a minute or so) and let it play without keyboard/mouse input


Reproducible: 

Steps to Reproduce:

Comment 1 Samuel Verschelde 2015-09-28 11:41:25 CEST

I got the same but it was my internet connection that was at fault. The buffer would still contain sound but no more video. Could you monitor your internet connection quality (for example with a simple ping and see if there are packet losses) next time it occurs?

Comment 2 Davide Nifosi 2015-10-01 09:09:46 CEST

Thank you for your reply, but this doesn't seem to be the problem: I've let ping run (on 8.8.8.8) while watching a YouTube video that froze twice in a couple minutes, but there was no packet loss except for a single packet that was lost more or less when I was opening the page. It also wouldn't explain why this never happens with another browser

Comment 3 Samuel Verschelde 2015-10-12 10:35:45 CEST

Do you have interesting logs in console if you start firefox from command line and get the freeze? Does firefox from mozilla.org freeze too?

You could also try to use strace to see what system call is the last one before the freeze (unless it's one that is called repeatedly, which would be an interesting piece of information too).

Keywords: (none) => NEEDINFO
Assignee: bugsquad => thierry.vignaud
Source RPM: (none) => firefox

Comment 4 Davide Nifosi 2015-10-21 07:51:58 CEST

No new message appears on console when the video freezes. Haven't tested the other stuff yet, but I've just tried switching Intel acceleration from SNA to UXA and it doesn't seem to have the issue anymore.

I'll keep testing all options anyway and will let you know

Comment 5 Davide Nifosi 2015-10-21 23:00:16 CEST

I've tried using the mozilla.org Firefox but couldn't seem to reproduce the freezes (tried both with the same profile as the distro Firefox and with a new profile), so this seems to be unique to Mageia.

I've tried running strace and detaching after I saw the freeze; I don't know of a better way to get the trace from exactly when the freeze occurs, so I'm attaching a file with the last 50000 lines of the strace output

Comment 6 Davide Nifosi 2015-10-21 23:01:50 CEST

Created attachment 7156 [details]
Last 50000 line of Firefox strace output around the time of a freeze

Comment 7 Davide Nifosi 2015-11-02 19:48:50 CET

Correction: even with UXA acceleration it can still freeze

Comment 8 Davide Nifosi 2015-11-03 20:44:15 CET

After setting layers.offmainthreadcomposition.enabled to false (see bug 17001, comment 6), I was able to watch a 20 minute video without freezes. I'll check if the new firefox package (disables cairo) fixes this without changing this option, and failing that I'll disable it again and keep you updated

Comment 9 Davide Nifosi 2015-11-05 07:43:30 CET

Haven't had a single video freeze so far with the new firefox package. Marking as fixed

Status: NEW => RESOLVED
Resolution: (none) => FIXED