MP4 sync problems

BruceDale wrote on 2/24/2008, 5:34 PM
I am trying to use video from the Aiptek GO-HD in Vegas. An amazing little camera, but a challenge to edit in Vegas. At a minimum, you have to take the MOV file you get from the GO-HD, open it in QuickTime and export it to re-encode the audio. (If you don't do this, Vegas will crash.)

The resulting MP4 file will open in Vegas but the audio is out of sync with the video. The size of the discrepancy varies from file to file. One was only two frames, the latest one was 26 frames.

QuickTime seems to be OK with the files, so I suspect the problem is with Vegas. I really don't want to have to re-encode all these files before I can edit them. But figuring out the sync error is hugely time consuming.

Any suggestions?

Bruce

Comments

Who8MyLunch wrote on 2/24/2008, 7:28 PM
I have seen similar problems with my Sanyo Xacti HD700. It puts out 720p mp4 files that I can directly drag into Vegas. I don't need to deal with any Quicktime business, but I do see odd audio synchronization problems. No matter how I set up my project the audio is always out of sync during preview. But once I render to a file the audio seems OK. My system is a quad-core with 2 gigs of ram. The task manager shows about 10% CPU utilization and 1 Mb/s of disk activity during playback at full quality and full size. I don't see any reason for the lag.

This really bugs me, because if I had shifted the audio in Vegas thinking I was correcting a problem, then the audio in the rendered file would be off. How can I trust what I'm editing if the preview does not precisely match the audio of the final rendered file.

Bruce, have you tried rendering some video to a file without compensating for any synchronization? Just to see if it is only an effect of Vegas' preview? Just curious.
BruceDale wrote on 2/24/2008, 8:13 PM
That's a good question, but I'm afraid that the sync issue persists in the rendered file.

Vegas also definitely struggles to preview it too. That's one reason it's incredibly painful to solve the sync problems by hand.

Bruce