out of sync audio in h264 videos

Problems, bugs, suggestions... anything related to SMPlayer.

out of sync audio in h264 videos

Postby userjazz » Mon Oct 24, 2016 8:02 pm

With many h264/aac videos (whether in mp4/flv/mkv etc container), the audio slowly but progressively gets out of sync, to the point where the video is unwatchable. Seeking to a new position temporarily resets sync and corrects the problem, but audio will just slowly get out of sync again.

In terms of reproducing the problem, unfortunately, it is not consistent across all videos; about 1/3 of my videos seem to manifest this issue. The red flags seem to be h264 w/variable frame rate, and video encoded via Adobe flash (flv videos, even w/constant frame rate, will have the problem).

I am using SMPlayer v16.9 on Linux Mint. This bug only started occuring when I upgraded to 16.9; before that I had never encountered this. It is also not the direct fault of using mpv vs mplayer; if I play back the same video using mpv directly (via command line), the syncing problem does not occur. The problem also does not occur if I play the same videos using other players (Totem, VLC, etc), so the videos themselves are apparently fine. But of course I would much prefer to use SMPlayer, because its interface/usability is so superior.

Anyone else having this problem, or am I just missing something, such as in Preferences settings? Hopefully I'm not alone in this and this is a bug that can be fixed in the next release.
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Re: out of sync audio in h264 videos

Postby rvm » Mon Oct 24, 2016 9:44 pm

If this problem doesn't happen in other players then I would first suggest to try changing the video and/or audio output (preferences -> general -> video, audio).

If that doesn't fix it, you can try to enable the option "allow frame drop" in preferences -> performance.

There are also some options for synchronization that you can try in preferences -> general -> audio.
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Re: out of sync audio in h264 videos

Postby userjazz » Tue Oct 25, 2016 3:41 pm

Thanks for responding. Yes, I've tried changing pretty much all a/v settings, one by one, including frame drop, a/v auto-sync and sync correction, hardware decoding, etc. No difference. I'm pretty much out of options, so it seems like an internal SMP bug and I'm surprised it appears it's only happening on my machine.
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Re: out of sync audio in h264 videos

Postby DVV » Tue Oct 25, 2016 8:04 pm

For me the similar issue was solved by setting "Threads for decoding" to 2 in the Preferences - Performance.
Basically this option allows to use several CPU cores for video processing. For example, a number of 4 can be specified for a 4-core CPU.
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Re: out of sync audio in h264 videos

Postby userjazz » Wed Oct 26, 2016 8:04 am

Thanks for the responses; unfortunately, no amount of tinkering with user settings would solve this problem. I finally just removed SMP completely (including all the config files), then re-installed it from the ppa, and the problem is gone. I then changed all the preferences back to my usual settings, and the problem still did not return. The same exact SMP version (down to rev#) was reinstalled, so I have no idea what the problem was, and probably never will. Maybe I just had a corrupted binary file? Oh well! at least I can enjoy using SMP again.
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Re: out of sync audio in h264 videos

Postby the_departed » Sun Mar 19, 2017 8:31 pm

I had the same problem. As user DVV already said, setting the "Threads for decoding" option to an appropriate value solves the problem. The interesting thing is, in my case it was set to a value too high, 6 on a two-core machine. When I set it to 2, it works perfectly. The moral of the story is: don't be greedy! ;)
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