lost audio sync, please help.
 

Hello,

I am in Pal area (Holland) but recorded with my EX1 in 1080p 30fps (ntsc setting) a live concert
(20 minutes)
The audio was recorded from a Yamaha digital mixer into a Digidesign protools 002 rack
on 11 tracks.We used the adat connection and the 'normal' inputs.

I am very exited about he results, the Ex gives beautifull colours and sharpness.
but I have a problem with the audio that was 'bounced' from Protools because I
can not get it in sync.
After 1 or 2 minutes the 'out of sync' starts.
I am using finalcut and edit in excam format.

Does it have anything to do with the PAL-NTSC?

Anybody..
Thanks

Siep Dijkstra

You need to tell us about that audio file from protools.
Could it have been locked to a 25fps frame rate or . . . ?

Thanks Graig,

I don't know, it was a recording in 48kz and 24 bit.
it sounds great and I hope to make a dvd/blue ray disk
from it.

Somewhere on the net in a forum I read about that the canon 5d mark2, that 'only'
records video in 1080p setting on 30fps, was not really suited for the PAL market for
different reasons.

One thing is, if you record from an external audio device the audio sync was a problem.
Why and how to solve it, was not mentioned.

Maybe some one recognizes this?

Thanks for any input,

Siep Dijkstra

I've recorded audio into my Edirol R-4 at 48KHz/24bit along side my EX1 and held sync to less than 1 frame error over 1 hour. I'm certain that's partly just good luck as the same audio recorder was not so close to the V1 I'd used before. That was around 6 frames off per hour.
To be getting noticeably out of sync after 1 or two minutes something is seriously out of kilter. Although it was recorded at 48KHz they didn't bump that down to 44.1KHz did they.

To answer your concern, both PAL and NSTC run the audio sample clock at 48KHz however keep in mind that the NTSC frame rate is not exactly 30fps although this should be quite irrelevent in this case, the audio clock is still 48KHz.

You may be able to fix this quite easily.

I know I can in Digital performer (many audio programs do this without changing pitch). Find a sync mark in the beginning of the video and one in the end (a rim shot or something obvious).

Then do a time stretch/shrink on the audio file to match the video. Save the file and then use the new file as your audio, I have had to do this a few times when matching different cameras and tape decks, they all drift unless you can genlock them. It works very well and does not degrade the audio (at least in Digital performer).

Thanks Bob and Olaf,


Time stretching, I can try that in protools.

What should happen if I make the movie 25 fps?

Thanks,

Siep Dijkstra

Converting vision from 30p to 25p is no simple task. You could try After Effects pixel by pixel method but it can break.

The audio should need nothing done to it as the movie will remain exactly the same length.