[FFmpeg-user] ffmpeg recording RTSP stream with audio out of sync
dha4t.ffmpeg at gmail.com
Tue Jul 19 16:01:30 EEST 2016
> I am having a problem with the video / audio sync when recording from an
> RTSP stream with ffmpeg.
> The result seems leave the video and audio out of sync in Windows Media
> Player (which unfortunately is the application I need to use for this), where
> as VLC seems to be able to cope with this and rectifies the problem.
I have a similar (if not exact same) problem when copying an RTSP stream. I've also verified the different behavior in Windows Media Player and VLC. The workaround I found was to run the resultant video through an ffmpeg process using -ss 0 -i input -c copy which seems to bring the audio and video back into sync. It's a quick "copy" process. No need to find the exact offset as -ss 0 seemed to work no matter what amount of offset there was. My theory is that ffmpeg waits until a keyframe before copying video, but audio starts copying right away which causes audio to lag video (video is pulled forward to fill the non-keyframe gap). The -copyinkf (copy initial non-keyframe) parameter didn't have any affect for me. Again, only a theory. I'm just a user, not a developer.
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