RE: WAY OT: Video Sync

[Alex Stahl <alex@pixar.com>]

Problems like this sometimes stem from confusion surrounding the fact 
that there's both a video frame rate and an audio sample rate 
involved. I very often see pulldown related drift problems, for 
example when a "29.97 non-drop, 44.1kHz" project really turns out to 
be 29.97fps, 44.056kHz. (44056 is to 44100 as 29.97 is to 30). There 
isn't a universal standard for pulling down audio clocks along with 
video rates, afaik. This can be a major headache when cutting a 24fps 
film on video equipment, then mixing it to film.

Unfortunately, the amount of drift you describe is much greater than 
the .1% error typical of video pulldown problems. Nonetheless, if the 
drift seems to be a consistent gradual slippage rather than a few 
sudden jumps, you could hack your way out of sync hell by 
sample-rate-converting the mix and/or tweaking the audio rate 
settings in Nuendo (if there are any!).

-Alex S.

At 4:33 PM -0600 2/6/02, Graham, Lindsay wrote:
>Yeah, --if I understand you correctly-that is exactly what I did.  Mixdown
>the whole project to an AIF file, then replace it in the original 
>QuickTime
>file.  Though I may have been able to get it to resemble being sync'd in
>Nuendo, it sure as hell isn't sync'd after being placed in the QuickTime
>file.
>
>Lindsay Graham
>sonic detritus:
>left of eliot
>http://leftofeliot.iuma.com
>
>  -----Original Message-----
>From:  Stephen P. Goodman [mailto:spgoodman@earthlight.net]
>Sent:  Wednesday, February 06, 2002 4:26 PM
>To:    Loopers-Delight@loopers-delight.com
>Subject:       Re: WAY OT: Video Sync
>
>Perhaps you need to save the file first as a single AVI/etc file, and then
>see.
>
>  > I'm scoring a short (8+ min) local DV project and am having a fit with
>sync
>  > issues.
>  >
>  > Here's the lowdown:
>  >
>  > I was given a QuickTime file of the final visual edit.  I'm using 
>Nuendo
>on
>  > a PC, which can import and display video, so that's cool.  I finish my
>  > preliminary score, making sure certain moments in the audio line up 
>with
>  > certain frames of the video.  Ok, great.  However, even though I took
>great
>  > care to line up an audio event with a video frame-and it does indeed
>appear
>  > to be in sync if I place my cursor at that position in the 
>timeline-if I
>  > play the file from the beginning, the sync drifts.  Ok, so that's 
>strange,
>  > so I make sure I set up my Nuendo project the with the same frame 
>rate as
>  > the QuickTime file.  In the media pool, the QuickTime is described as
>  > 29.97fps, so that's what I set my project to (and my timeline view 
>to).
>  > Same problem: drift.  I talk to the film maker and he says he's 
>editing in
>  > 29.97dfps (drop-frame), so I say, Ok, reconfigure my project, realign 
>all
>  > the audio events and, low and behold, the thing seems to be in sync 
>(or
>was
>  > it when I ignores the drop-frame that it appeared to be in sync-I 
>can't
>  > remember).  That is, up until I replace the audio in the original
>QuickTime
>  > file and now I'm off like eleven seconds over the 8:20 project!
>  >
>  > It's at this point that I took the CD containing the QuickTime file 
>and
>  > tried to swallow it.
>  >
>  > I've hit the Nuendo website and support is thin.  I don't expect a 
>reply
>  > from customer service for a while.
>  >
>  > Anyone with actual hands-on experience know the answer to this?
>  >
>  > Lindsay Graham
>  > sonic detritus:
>  > left of eliot
>  > http://leftofeliot.iuma.com
>  >
>  >
>  >
>  >