video stream and audio stream out of sync

Have you read the FAQ and checked for duplicate open issues? Yes, I search with keyword sync, didn’t find related issue

What version of Shaka Player are you using? v3.0.2

Are you using the demo app or your own custom app? Custom app

What browser and OS are you using? GoogleChrome, Ubuntu

Sometimes, when watching long movie, video and audio (using DASH) going out of sync, just half a second or a second (but I can realize that - because character lip movement), fix it by click on the seeking bar, audio and video will sync itself.

I’ve experience this a number times, don’t know how to reliably reproduce them.

On the otherhand, youtube seem to have this problem as well, but they cleverly fix that by either pausing video or speed up the video until it match. (it happen really fast, like in 0.2s - anyone else experience this ?)

Just want to ask is it possible for our library to out of sync video and audio? And we currently don’t have mechanism to periodic autosync, is that right ?

[joeyparrish]

Thanks for the information!

Based on my experience with content issues in general, I would say this is bad content. Even if Firefox plays it, that doesn’t mean it’s necessarily in-spec. Some players or platforms are more forgiving or flexible about their interpretations of things.

My suggestion is to check if you’re using a recent, stable release version of ffmpeg. For example, I see good results with v4.3.1, which I installed from a Debian package. That appears to be the latest release as of August 2020. Before that, I was running v4.2.1 built from source.

Then I would suggest you check that you have a recent stable version of libvpx. I have seen many, varied issues with VP9 content encoded with old versions of libvpx. I’m currently using libvpx v1.8.2 from a Debian package. There’s a newer release out as well, v1.9.0. I have created bad VP9 content before that was fixed by upgrading libvpx, even without upgrading ffmpeg. So I would suggest upgrading if your copy is older than v1.8.2.

With these versions, our own demo and test content seems to be in sync. We encode everything in both H264/AAC and VP9/Opus in the same MPD (using Shaka Streamer).

I hope that helps!

[joeyparrish]

@kocoten1992, thank you for posting the solution! I’m sure this will benefit others in the community having AV sync issues.