Audio gets out of synch every time ... why?

Yojimbo wrote on 12/1/2002, 5:01 PM

I have been working on a 5 minute trade show demo loop, shot on DVCAM, to be burned to DVD. The footage transferred just fine to disk, and everything plays nicely. Nothing is out of synch to start with.

However, when this project plays, there's a moment when the audio gets out of synch by several frames. It *always* occurs about 4 minutes in. Has anyone run into something like this?

The audio is entirely an on-camera talent. After the video edit was complete, I rendered the voice track as a .wav file, loaded it into Sound Forge, and improved the presence of the talent's voice. The resulting file was then saved to disk, brought back into the project, and placed on a track of its own. The original track has been muted.

It plays/previews perfectly. It's dead on.

However, when rendered, as an MPEG2, uncompressed AVI, or Quicktime MOV, there's always a point where one segment seems to "go off" about 4 minutes in - it starts a frame or two off, and within a few phrases it feels about 4-6 frames off. Then the shot changes and we're into the final card, and that's it.

The project is NTSC DVD 29.97 FPS and I've changed nothing about its frame rate, nor have I employed any audio or video timing changes or effects of any kind. The talent is in mono. The music underneath is stereo.

Is this enough info go go on? I'm stumped. I've even used MyDVD and burned a test DVD, but the problem remains, so I can only assume it's coming from VV this way.

Help. And thanks.

yojimbo

Comments

Tyler.Durden wrote on 12/1/2002, 5:05 PM

Hi Jim,

Please post the sample rates of your audio at each stage of the process, there may be a clue there...

HTH, MPH

Tips:
http://www.martyhedler.com/homepage/Vegas_Tutorials.html

Aje wrote on 12/1/2002, 5:11 PM

I have the same problem but only when burning VCD´s never with DVD´s.
I´ve also tested out that the sync is broken with about 4-6 frames and a bit in the film.
It´s no help to you but now we are two asking for help.
Regards
Aje

vitalforces wrote on 12/1/2002, 6:58 PM

Same problem here. Up to now I was only working with DV AVI and loving it (rendering to tape with no problem). Today I rendered a 2-minute DV AVI file, within VV3, straight to an MPEG-2 file on the hard disk, then played the MPEG-2 back in VV3's own window. (Getting ready to do a test burn with MyDVD.) I had deleted the sound and replaced that track with a .wav music file. Midway through the file, barely over a minute, the music track was 10 seconds behind the video track! To my eye, it's not the audio but the VIDEO that's running too fast and getting 'ahead' of the audio. If the default DVD template needs tweaking, whence to tweak?

Time for an SF monitor to weigh in.

vonhosen wrote on 12/1/2002, 7:12 PM

If you've brought in CD audio material it's gonna be 44.1 kHz . Try converting the .wav file to 48kHz first then bring it into your VV3 project & render to MPEG-2 (which uses 48kHz audio).

Yojimbo wrote on 12/1/2002, 7:50 PM

Here are the audio file specs..

The original audio came in as 48K 16bit stereo with the DVCAM footage.

I rendered this out from Vegas as a 48K 16bit mono file. I compressed and EQ'd to bring out the talent's voice, and saved from SForge. Afterward I dragged the file back into Vegas. Since it had been rendered from Vegas to start, it appeared to line up perfectly with the original audio, and it previews correctly. However this strange attribute remains when I render.

I have one music track, in stereo, under several segments. So my rendered output is set for a 48K 16bit stereo video clip.

One other thing I notice is that all of the video clips are set to Resample and Reduce Interlace Flicker in their properties tabs. Could this be interfering? Seems odd, but at the moment I'm into trying any switch that might have bearing here.

yojimbo

vitalforces wrote on 12/1/2002, 8:22 PM

Thanks for the tip. I love this forum, it's like college without dull professors. By the way, I just realized on reopening my VV3 project that I had deleted a video event and moved everything left (except the audio track) about--yeah, 10 seconds. Gives new meaning to the word DUH. :)

vitalforces wrote on 12/1/2002, 9:11 PM

Further reply for the benefit of anyone following this thread. I just re-rendered eleven minutes of a DV AVI into an MPEG-2 within VV3 and no problem. 'Frame' accurate.