Mp4 audio out of sync only in Avidemux

[Verosk]

Hi, I am fairly new to avidemux and I am trying to join some mp4 files together using the append function.  However when I open the mp4 file in Avidemux it is out of sync.  The noise plays too soon compared to the actions.

I don't understand why I have this problem only when opening the file in Avidemux because it's fine in VLC media player.

The video is a H264 file   and audio is .mp3 if that helps.  Frame rate 30.

Edit:  Upon further tests the problem lies with stopping and starting the video.  When i hit play it is fine for the first 5 seconds no matter where I am in the video but the sound races ahead of the video eventually.  I am thinking it has something to do with the FPS of my video maybe.  It should be 30 and it shows as 30 when i hit the "i" button.

Thanks

[zakk]

Check your fps with Mediainfo to be sure first.