Subframes, audio alignment

Digital Perfomer in the context of television/film scoring and post-production.

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mesayre
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Subframes, audio alignment

Post by mesayre »

Hi,
I've been wrestling with a little bit of a sync problem for a while, and I'm hoping one of you folks can shed some light on the issue. I often render tracks from virtual instruments in DP, and then prep them for a record/replace session in Pro Tools later on. I then also record an audio click in DP, which begins at a different time (2 bars earlier) than the stems I'd rendered before. The problem is that when I import both the click and those stems into PT, they don't quite line up. The difference is not much, but it is audible. It varies from session to session, .

My theory is that this has something to do with the different ways that DP and PT handle audio that is recorded at a time that's not exactly on a frame. Do any of you know exactly what DP does in that situation? Does it extend the beginning of the recording to make it a full frame? Does it chop off the first few milliseconds to round it down to the nearest frame? Or does it record right at the tick ignore the subframe? If that last one is the situation, then perhaps there is a bit of "extra" audio that causes things to get pushed later when I spot it in PT?

Any ideas?

Thanks,
Mike
DP 10 - Win 10 - Ultralite AVB
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MIDI Life Crisis
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Re: Subframes, audio alignment

Post by MIDI Life Crisis »

I've seen that as well and it can vary widely - throwing everything off sync. I don't know why but a great engineer who helped me with this last year blamed PT10 and how there is a difference in how it reads the data.

The fix was to create an AAF (or OMF) and import that to PT. I haven't had to go to a PT system in a while but will early next month, so it'll be interesting to see if the problem persists in DP 8.06.
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Phil O
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Re: Subframes, audio alignment

Post by Phil O »

I haven't had the pleasure of working with PT for some time now, but the last time I needed to do so (with files created in DP), we had similar issues. As far as I know, DP time stamps are sample accurate, so I think the problem is at PT's end - but I could be wrong.

Anyway, our workaround was to select all soundbites back to time zero (even if they didn't start at zero) and merge, insuring that they all started at exactly zero, then export. The resulting files imported in PT could then easily all be aligned to zero.

PIA, I know, but it worked.

Phil
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MIDI Life Crisis
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Re: Subframes, audio alignment

Post by MIDI Life Crisis »

An AAF will cut out the guesswork and PT can read it w/o the damn lame-ass OMF translator.
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Re: Subframes, audio alignment

Post by Phil O »

Sounds like the way to go. I can't remember why we didn't use it back then. Perhaps it wasn't available on both platforms yet. Don't know. :?

Phil
DP 11.23, 2020 M1 Mac Mini [9,1] (16 Gig RAM), Mac Pro 3GHz 8 core [6,1] (16 Gig RAM), OS 14.3.1/11.6.2, Lynx Aurora (n) 8tb, MOTU 8pre-es, MOTU M6, MOTU 828, Apogee Rosetta 800, UAD-2 Satellite, a truckload of outboard gear and plug-ins, and a partridge in a pear tree.
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