Synchronizing Laserdisc audio to Bluray - missing frames

[Colek]

Hey guys,

So basically, I have two Laserdisc audio rips that I want to sync to Bluray master, but the problem is, that Laserdisc isn't frame-by-frame matching the Bluray, mostly it's missing frames on start/end of some scenes. The problem is, that I really want to sync these audio tracks to that Bluray release. I wanted to know what's your opinion on what should I do with that. I had three ideas:

1. Fill the 'missing' frames with audio from other Laserdisc (already synced, but different master).
2. Stretch audio on these shots, keeping the scenes that are matching - untouched (with preservation of pitch, of course).
3. Simply put silence in missing frames.

[Feallan]

Would the sudden change for a frame or two to that other track sound jarring? How different is it?

[Colek]

Would the sudden change for a frame or two to that other track sound jarring? How different is it?

Not much really, and I did some math and I guess I'll go with it. Shift of like 0.001% shouldn't be noticeable at all for ear.

[Chewtobacca]

I shouldn't add silence.  Stretch the audio or crossfade it back on itself, depending on what's occurring at the edit-point.  Using audio from another mix is all right too, as long as you replace affected sections, not just individual frames, and as long as you don't have to replace too much.

[Colek]

Yep, stretching sounds like the best idea here, gonna be lots of work though

[jerryshadoe]

With the amount of tracks I have synced to each other from different masters, I have to agree with Chew on this one:
don't insert silence (unless silence is there originally and you're just extending it) the best bet is to stretch or crossfade (via dupping a part of the audio) it into itself... if the the transition between different masters isn't jarring, than that will work fine too for filling in gaps

What software are you using to do the syncing work, if I may ask?

[Colek]

Thanks lads, I'll just stretch it out then. I am using Reaper for this.

[Stamper]

Resurrecting this thread, I noticed on old LD masters also differences of frames, not just at the end of reels, or beginning, but within scenes.

If you let it play, you realise that the sync resume itself a scene or two later, so I wouldn't touch them. No one will notice the difference in the audio.

[spoRv]

Well, a frame is ~40ms, and albeit only few will notice a 10ms out of sync, most if not all will notice a 20ms, go figure ~80ms for two frames!

To be sure, though, show it to someone who is not aware where the delays are, and ask to tell you if/when those would be noticed.

[Stamper]

Can you notice within the space of a shot or a couple of them? It's weird though that many scenes have extra frames. It's head scratching. I noticed this on T1 while doing the syncs, the ending scene for example have extras frames there and there. But a few shots later, they realign.