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Identical audio tracks, identical waveforms, BUT non-sync playback!
Hi all – I’ve been up all night trying to figure this one out… I’ve shot a video on XDCAM, edited using the native codec in FCP 6.06, graded in Color and sent back to FCP as ProRes 422 (HQ).
Now, here’s the weird one – the original unmixed soundtracks have remained in sync with the graded video, but the mixed track from the sound studio gradually drifts out of sync by about 15 frames after 10 minutes of playback. I figured it was just a sample-rate mismatch but all tracks checked out and are all 48KHz – AND even the graphical waveforms are visually a frame-perfect match to each other. Then I figured it could be hard disc speed or an issue with the Blackmagic card – but an export to DVD via Compressor also produced a disc where the audio gradually slipped out of sync so I’ve pretty much ruled out hardware.
Any guidance would be much appreciated… this thing isn’t giving me any more clues to work with, everything that could be set up incorrectly checks out fine, so I’m banging my head against a wall at the moment! 🙂
Cheers,
TomTom Mountford
Senior Editor
The JMS Group Ltd -
2 Replies
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Try all of the same but with ProRes SQ (i.e. non HQ). There is absolutely nothing gained by using HQ in your case (anything less than 2K files), and HQ often seems to generate many mysterious errors.
David Roth Weiss
Director/Editor
David Weiss Productions, Inc.
Los AngelesPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW’s Apple Final Cut Pro, Business & Marketing, and Indie Film & Documentary forums.
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Cheers for the info David – I’ll bear that in mind regarding HQ over SQ, I’ve found it’s a great codec visually but come to think of it my previously rock-solid system HAS been doing numerous very bizarre things since I started using it on a regular basis. I’m a heavy user of XDCAM-EX but most apps take forever to render graphics etc in that codec so ProRes seemed a pretty good intermediate… but I might reconsider using HQ!
Anyway, I did find a cause and the workaround – the timing reference of the ProRes sequence was being messed around by importing an externally sourced WAV file onto the timeline… sure they were both 48KHz – but creating the soundtrack on another machine brought along with it something buried deep in the data that conflicted with ProRes… the solution was to put the WAV file through Compressor and create a new 48KHz AIFF file… and tah-dah!!! After a sleepless night all my non-sync sound nightmares were solved!
Tom Mountford
Senior Editor
The JMS Group Ltd
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