Audio out of sync with video at 45min+ mark

AVERAGEJOE wrote on 2/4/2004, 4:14 PM
(also posted in the DVDA forum, no luck)

I render a live video of a band playing to NTSC DVDA from VV4.
I sync the same DAT audio track to the video and render to AC3.
Then burn the DVD in DVDA

I get sync problems..cymbals/drums/words being hit/sung, but the audio comes out about a half-second later near the 60minute mark and only gets worse as it gets later...VERY unprofessional product to present to people.

All OK at beginning and sort-of-middle..the audio track sine waves are 100% in sync, every audio 'spike' lines up 100% from start to finish, etc. I am getting tired of doing fade-outs around the 60 minute mark on EVERYTHING I do to re-align the video/audio tracks.

I have seen suggestions on here to render both video/DAT to a new AVI track in VV4, but that takes way too long, a lot of space, and double the work. I tried it anyway. SOL.

I tried re-sampling the 44.1 audio to 48, and then used VV4 to Ac3 it. STILL no good.

I tried to render to MPEG2 and see if there still an issue. There is. Video is ahead.

What are we ALL doing wrong? What other suggestion(s) does anyone else have?

XP Pro/AMD2400/1GigRAM/120G 7200

Thanks

Comments

Spot|DSE wrote on 2/4/2004, 9:05 PM
Clocking difference between the camera and the DAT machine. This is fairly common. In the audio side of the world, we've been dealing with this forever. Instead of using a DAT, why not send the mix to the camera? Then you have a constant, it's always locked, and the signal is the same unless you are using a 24 bit/48k dat.
Liam_Vegas wrote on 2/4/2004, 9:29 PM
I don't quite get to userstand your issue fully I think. Within Vegas is the audio completely in sync all the way throughout? Is it only when you render to Mpeg or get DVDA to render then burn your DVD that you notice the problem?

I had a weird issue today with a DVDA project where the video/audio is perfecly in sync in vegas and in the AVI. Rendered to MPEG2 and loaded into DVDA and it sounds/looks perfect in DVDA preview even but on the final disc there is a bit in the middle (29 minutes) that gets slightly out of sync but a few minutes later on the sync is back to normal. Never had that problem before. Not sure if this is a similar issue to what you are experiencing.
farss wrote on 2/4/2004, 9:33 PM
Wouldn't the A/D converters in a DAT be better than the ones in most cameras though? Also this assumes you can bring balanced audio into the cameras as well.
Your other options I guess start to get rather expensive like getting a DAT that'll record TC or running everything off the one SPG.
I'd imagine though that there must be breaks at many points in the concert, the trick would be not to wait until things are noticeable out of sync but resync at the start of every break.
You could speed up/ slow down the audio or video based on how much you're out at the end but that means everything being resampled which may result is a quality hit negating the advantage of recording to DAT in the first place.