synchronizing beds with a live recording HALP

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FevinKraser
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synchronizing beds with a live recording HALP

Post by FevinKraser » Fri Mar 04, 2016 1:22 pm

hello tape op'ers. i've run into a tricky situation and have spent too long trying to do it only on my own.

so i have this musical project called 'livestalk and the bodies'. for the performance, i pre-record acoustic guitar and 4-5 part harmonies and play them thru an mp3 player (guitar L and harms R) while i play drums and sing live.

someone took a professional video of my last set, but the backing tracks are super quiet in the camera's mic. i asked the camera person if they could send me just the audio wav file so i could line it up with my bed tracks at home.

all the songs are one giant track, and each have count in's (that are also audible in the camera mic), so i thought this would be pretty easy to line up.

my problem comes in when i line up any one of the count in sounds, the beds seem to be moving faster than on the camera mics (but the pitch is the same) the result is, it sounds lined up for about thirty seconds and then the beds start to move faster.

originally i thought i might just be mis-alligning them up but i feel like there's something more to this, cos if they're theoretically the same speed, i should be able to set the beds ahead of the beat, and they should be ahead of the beat the whole way thru. i've tested this by putting it intentionally behind, and eventually it lines up and then starts going ahead again.

is it at all possible that when i exported the files it time stretched it? if so how do i prevent this? how do i figure out how much i stretched it so i can alter the beds to line em up

ALTERNATIVELY: if the case is i'm really just not lining it up properly, does anyone have any tools or suggestions to help with a problem like this???

thank yew

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Post by kslight » Fri Mar 04, 2016 2:02 pm

My guess is there is some funky sample rate conversion or clocking going on somewhere between your original export (the file you used live), your MP3 player, or the camera audio.

Just for fun you might play back the MP3 player into your computer and record THAT version of your bed and see if the time on that is similar. Maybe not "ideal" but I'm guessing the offender is either your MP3 player or the camera.

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Drone
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Post by Drone » Fri Mar 04, 2016 2:45 pm

Some audio software allows you to Tempo correct, can you time the beds and then tempo correct the backing tracks to match? Lime I can tell my software make this track 455.87 seconds long, type deal.
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Gregg Juke
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Post by Gregg Juke » Fri Mar 04, 2016 4:33 pm

Yeah, something is definitely going on. Possibilities? Video audio is usually at 48, are you working with audio at 44.1? Also, the MP3 tracks-- Are they actually MP3's? MP3 files and .wav files of the same tracks will not line-up (perfectly and permanently), regardless of program material or if they are at the same pitch. Add to that the fact that there is often drift between camera audio and "wild-tracked" (un-synced) on-set audio, and it looks like you will at least need to cut the tracks at a few points and make a few adjustments to re-align at minimum. Hopefully not too much work in too many places...

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Post by vvv » Fri Mar 04, 2016 4:44 pm

Sometimes those cameras have an auto-limiter, and some might have a compression algorithm; might be a cause?
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A.David.MacKinnon
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Post by A.David.MacKinnon » Fri Mar 04, 2016 7:59 pm

Gregg Juke wrote:Video audio is usually at 48, are you working with audio at 44.1?
GJ
My guess would be this plus a bit of MP3 crappiness (although if it were just mp3 I'd expect the synch to last longer than 30 seconds.

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DrummerMan
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Post by DrummerMan » Sat Mar 05, 2016 6:45 am

My guess would be this has to do with the 48k sample rate that video tends to use. I don't know what software you're using to sync the 2 up but try changing the sample rate of the project without changing the sample rate of the mp3. See if that helps. (Or makes things worse)
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Nick Sevilla
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Post by Nick Sevilla » Sat Mar 05, 2016 8:14 am

Welcome to the wonderful World of unsynced audio.

1. The mp3 player played at a slightly different rate of speed than the video camera recording the show, which is playing back the audio at a different rate of speed than whatever computer you are using to edit your music to the picture audio.

This is how you can fix this, at least try to fix this:

First, write down the sample rate of each of the three devices. Do they match?

Start a brand new project, and make the sample rate match the VIDEO track. It will hopefully be 48kHz 16 bit or 24 bit.

Import the other audio, both the one from the mp3 player, and your audio from your other DAW project. Make SURE this audio is CONVERTED and COPIED into your project into the correct 48kHz sample rate.

Even after you do this, there will be some difference, however it should be a lot less.

I think at some point in your cavorting around, one or more of the audio files got screwed up.

Let us know if this improves the problem. It won't make it 100% disappear, but it should eliminate one possibility.

Cheers
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Post by mwerden » Sat Mar 05, 2016 7:43 pm

Just had a wonderful flashback to my Blueman days. Used to deal with this sort of thing CONSTANTLY. All of the aforementioned things could possibly be true, but what it sounds like to me is pull up/down.

Short story is that video don't care about no timing issues when you convert frame rates, so you get all kinds of nightmare scenarios (harsh? maybe). The end result is audio that seems to be the correct pitch but drifts over time. PT has pull up and down options to compensate in the Import Audio window, source sample rate dropdown. Try 'em out and see which one matches.

I personally never had drift issues with mp3 conversion. Protools used to add a bit of dead air at the end when you bounced to mp3, dunno if it still does.
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Post by vvv » Sun Mar 06, 2016 10:21 am

I've had people send me *.mp3 tracks (like when someone sends a bass track over he net to add to one of my tunes) that, converted to *.wav, won't align.

I see that problem much less lately, but I'm sure it's the compression/conversion process, there.
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vvv
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Post by vvv » Sun Mar 06, 2016 10:21 am

Site hung - double post. :x
Last edited by vvv on Sun Mar 06, 2016 10:28 am, edited 1 time in total.
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vvv
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Post by vvv » Sun Mar 06, 2016 10:21 am

I've had people send me *.mp3 tracks (like when someone sends a guitar track over the net to add to one of my tunes) that, converted to *.wav, won't align.

I see that problem much less lately, but I'm sure it's the compression/conversion process, there.
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Drone
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Post by Drone » Sun Mar 06, 2016 4:59 pm

Triple, but who's counting. The internet is being really weird today. :mrgreen:
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Post by MoreSpaceEcho » Fri Mar 11, 2016 10:38 am

mwerden wrote: Protools used to add a bit of dead air at the end when you bounced to mp3, dunno if it still does.
dead space either at the beginning or end (or both?) of the file is unavoidable when bouncing to mp3.

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Post by mwerden » Fri Mar 11, 2016 3:04 pm

They gotta keep us on our toes somehow, right? Just like when my download code doesn't work and they "fix" it by giving me a temp license that doesn't cover the plugin bundle that was the reason I upgraded in the first place. Bla.
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