Sync problem with camera files

Posted by harry323 
Sync problem with camera files
March 02, 2011 04:08PM
I have some long interview files recorded on a Focus Enhancements FS-C which works with a Canon XL-H1. It's a hard drive recording device and it's always been reliable.

On this current job, when I play back a shot which lasts about 6 minutes from the Firestore to the Camera's viewfinder, everything is in perfect sync.

But when I download it to my Mac Octo the sound creeps ahead of the video by about 1 frame per minute.

I have tried playing it via Quicktime Pro, Ordinary Quicktime and in Final Cut Pro and I get the same result - at the end of my 6 minute interview file the sound is ahead by 6 frames.

I don't know if this is a new issue because I don't normally record long files like that, but I have a bunch of interview stuff with long takes.

Here are my deets, as the kids say:

Mac Pro Tower OSX 10.6.6 with 8 gigs RAM, Decklink HD Extreme, Final Cut v.6.0.6.

I have trashed prefs, run Disk Warrior and Disk Utility to no avail.

I guess it just hates me.

In any case, I reckon if the Firestore file plays ok to the camera, it's probably not the Firestore. Unless ... ?

Ideas would be welcome. I don't like the idea of going through every file and adding one frame of picture per minute. There are hours of this stuff.


Re: Sync problem with camera files
March 03, 2011 07:14AM

This seems to be a NTSC issue. Though I haven't worked with a FireStore for years. But I can remember that you got several options on how to record the files.
One of those is FCP compatible DV files (.mov). These files have no locked audio -- means the audio uses it's own track and you may get into FCP's NTSC trap for drop frame on video and NDF for audio. A .dv file will have video and audio interleaved and will always stay in sync -- the problem: you always need to render audio. (Or use iMovie smiling smiley)
As I am a happy PAL these problems never occurred here.
Have you tried to open those files in QT Player? Are they in sync?
You may try Compressor to bring the audio into proper NTSC timing -- this might involve a resampling (I never tried to use Compressor for such a job)

Re: Sync problem with camera files
March 03, 2011 01:43PM
Thanks very much for the information, Andreas.

Re: Sync problem with camera files
March 03, 2011 05:32PM
Isn't 6 frames in six minutes less than the difference between NDF and DF timecode for NTSC (29.97 fps)?

Unless my brain is too caffeine-addled right now, I believe that you drop two frames in the first second of each minute, unless that minute is a multiple of ten.

So, for something only six minutes in length, wouldn't that add up to 12 frames offset (if, in fact, the issue is the difference between DF and NDF timecode)?

winking smiley

Re: Sync problem with camera files
March 03, 2011 06:24PM
D-Mac ... interesting diagnosis.

I have found the cause of the problem. I normally record on 2 channels of audio on the camera but on this occasion I was recording on 4 channels. It turns out that, although the internal tape deck of the Canon Xl-H1 camera records all 4 tracks and picture just fine, the Focus Enhancements Firestore hard disk recorder has a problem with 4 channel audio.

Fortunately I was able to transfer the stuff anew from the camera tapes.

Thanks very much for the replies and advice.


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