Webm -> H.264 mp4 - audio loses sync toward end

[Kevin]

Is there a known bug or required setting when loading a .webm video and attempting to convert it to an H.264/AAC mp4 file? My resulting file loses audio/video sync as it plays. I noticed that the source file was 30.000 fps, which seems different from what I'm used to seeing (I'm new to webm files).

[mean]

If you mean playback inside avidemux, it is not a very efficient player , especially if you cant benefit from hw accelleration
The important part is : Is the end result file in sync ?

[Kevin]

Yes, both in Avidemux and after saving to either MVF or H.264/aac .MP4, the sync gets increasingly bad as the file plays.

[Jan Gruuthuse]

Avidemux is not intended as video player. Mean is not asking if they play synced in avidemux!

The avidemux saved video clips do these play in VLC synced?

Check you're using the same audio device as VLC.
See Menu -> Edit -> Preferences -> [Audio]
- Local playback downmixing [xxxxxxx]
- Audiodevice [xxxxxxxx]

[Kevin]

Avidemux is not intended as video player. Mean is not asking if they play synced in avidemux!

The avidemux saved video clips do these play in VLC synced?

Sorry, I thought I had made that clear twice. They do NOT play synced (all the way through) when played in VLC after saving in Avidemux. They DO play synced (all the way through) if played in VLC in their original state. I'll check later about audio device but I'm pretty certain it's the same in VLC as in Avidemux. Thanks for continuing patience.