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Old April 2nd, 2015, 06:37 PM   #1
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Audio Drifting Out Of Sync

This past year I relied heavily on portable recorders such as the Tascam DR-40 and DR-05 during the ceremony and reception. I found that for the most part they made my job a lot easier, but I just filmed a very long Catholic ceremony in December and after about 30-40 minutes the audio had drifted out of sync by an amount that was noticeable (maybe 7-8 frames). I tried using the new "Correct Audio Drift" feature in PluralEyes 3.5 but that actually made the problem worse for some reason.

Does anyone have a good technique for correcting audio drift from recorders that's not too complicated? I've heard that it's possible to bring a WAV file into Adobe Audition and do some magic to correct it but I'm not certain how that is to be done successfully. I'd like to correct the audio drift and then load everything into PluralEyes and let it sync everything up (without using it's "Correct Audio Drift" feature).
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Old April 2nd, 2015, 06:54 PM   #2
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Re: Audio Drifting Out Of Sync

I normally just correct it manually -- just pull it into line again every 20 minutes or whatever.

One dodgy compromise, but you didn't hear it from me: if you make sure it's in sync in the middle of a track, sometimes that will result in acceptable drift at the start and end of the track. It'll still be out, but just by one or two frames.
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Old April 3rd, 2015, 04:54 AM   #3
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Re: Audio Drifting Out Of Sync

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Originally Posted by Michael Silverman View Post
This past year I relied heavily on portable recorders such as the Tascam DR-40 and DR-05 during the ceremony and reception. I found that for the most part they made my job a lot easier, but I just filmed a very long Catholic ceremony in December and after about 30-40 minutes the audio had drifted out of sync by an amount that was noticeable (maybe 7-8 frames). I tried using the new "Correct Audio Drift" feature in PluralEyes 3.5 but that actually made the problem worse for some reason.

Does anyone have a good technique for correcting audio drift from recorders that's not too complicated? I've heard that it's possible to bring a WAV file into Adobe Audition and do some magic to correct it but I'm not certain how that is to be done successfully. I'd like to correct the audio drift and then load everything into PluralEyes and let it sync everything up (without using it's "Correct Audio Drift" feature).
What sampling rate are you using on the tascam? 44.1? The sampling rate for your audio on your camera is probably set at 48k, you can change the tascams to use the same sampling rate as the camera which will help.
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Old April 3rd, 2015, 08:09 AM   #4
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Re: Audio Drifting Out Of Sync

Yes, what Daniel says. If you record to same specs as camera your audio shouldn't drift. I used to record mp3 and it was awful, learned here to change to 48K wav and problems are all over.

In the meantime, you can chop up audio and match it up in pieces OR you can stretch it out or shrink it to match the camera audio (at least in Vegas you can).
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Old April 3rd, 2015, 11:47 AM   #5
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Re: Audio Drifting Out Of Sync

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What sampling rate are you using on the tascam? 44.1? The sampling rate for your audio on your camera is probably set at 48k, you can change the tascams to use the same sampling rate as the camera which will help.
It is set to 48k and actually didn't notice it being much of a problem until this recent wedding. I've heard that higher end devices like the ones by Sound Devices tend to stay in sync better than cheaper portable recorders like Zoom and Tascam. I was very pleased with my Tascams until this past wedding so it's possible this was just an anomaly as the other 26 weddings from last year didn't have this problem.
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Old April 4th, 2015, 05:46 AM   #6
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Re: Audio Drifting Out Of Sync

I got so tired of this happening, I gave up on the entire method. Now I just rely on two wireless mics
for the ceremony and connect a cheap b-cam into the dj both for the reception. Too much wasted time, frustration, and unreliability.
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Old April 4th, 2015, 07:36 AM   #7
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Re: Audio Drifting Out Of Sync

If you know it's 8 frames out, why not change the speed of the audio clip on the timeline, just speed it up by 8 frames? I've done that many times and it's been fine.
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Old April 4th, 2015, 07:44 AM   #8
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Re: Audio Drifting Out Of Sync

If you use Vegas you can stretch or squeeze the audio track to make it line up with the camera audio. They will almost certainly drift unless they are expensive gen locked equipment as the clocks in the various recorders are not locked in sync.

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Old April 4th, 2015, 09:14 AM   #9
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Re: Audio Drifting Out Of Sync

I don't get it. My zoom H1 doesn't get out of sync during full catholic mass. This has been true regardless of the cameras I've used over the last few years. I'm sure, that as Ron says, they will drift, but for me I'm good for about an hour or longer.

If you use the correct setting on a recorder, provided it has a setting that matches your camera, you should not experience any issues for an hour long recording.

If you're using mp3 files you will experience issues for sure.
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Old April 4th, 2015, 11:15 AM   #10
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Re: Audio Drifting Out Of Sync

It is not so much a drift in the particular device but a difference in the clocks used to run the devices. Not important if the file is played back on the same device. The issue comes when the camera file and the audio file are placed on the timeline which is controlled by the PC clock. Then the differences will appear since the NLE will count clocks to present on the timeline. Even a minute difference will be apparent over even a few minutes. To check this just place the camera file and the audio file of the same event on the time line in adjacent tracks and expand to say 10 frame timeline scale and look at the difference in waveform after say 30 mins when they have been aligned at 0.

If one only uses one or the other track for audio then one may not notice a big difference in sync to the picture however if audio is mixed then there will be an echo or reverb to the sound. Vegas can correct this by stretching or squeezing the audio track to match. I still do this in sections as it is easier to match waveforms. This issue by the way is also true if one channel is from a mixing board and the other a mic on the camera though in this case it is of course just an offset due to speed of sound in air compared to signal over wire.

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Old April 5th, 2015, 03:47 AM   #11
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Re: Audio Drifting Out Of Sync

I've had problems with tascam & zoom - use all sony now.

the best way I found was to set up a digital clock on screen that speaks the time and film it with my camera.
I also recorded with each different recorder and worked out the drift on each recorder. I write the amount I need to change the recording (97.88) by on the back of the recorder and alter the recording by that.
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Old April 5th, 2015, 07:27 AM   #12
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Re: Audio Drifting Out Of Sync

There are two things to correct. Clock difference which on the timeline will need to be stretched or squeezed to correct and offset since the camcorder audio is referenced to the video frame sync. So you may not be able to slide the audio into sync on the timeline. You will need a NLE that allows the audio to be offset by audio clock rates to bring into sync with the camcorder audio . Open up the timeline to 1 frame scale and see. Vegas will do both so although my main editor is Edius I do my audio in Vegas. Even if you only use the camcorder audio as a reference ( which is what I do most of the time ) you still need to sync to make sure there is lip-sync on the video.

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Old April 5th, 2015, 02:44 PM   #13
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Re: Audio Drifting Out Of Sync

I've not seen any problems in 1-2 hour recordings with with the Tascam DR-60D or the H1, though I have seen a issue with one (but not all) of my H2n recorders. I put it down to manufacturing tolerances of the frequency oscillator. The problem was easily fixed by changing the speed (not cutting) to be just a few frames shorter for the length of a ceremony.

Alternatively, you can cut at strategic points and just nudge a frame or two as required.
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Old April 5th, 2015, 06:18 PM   #14
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Re: Audio Drifting Out Of Sync

This is really helpful information and also makes me wish that Premiere Pro had the same drift correction feature that Vegas has. I think Dave is probably right in that Tascam and Zoom may tolerate a little more imperfection in their products than Sound Devices or other high end companies. I've contacted Red Giant to see if they can help me trouble shoot their drift correction feature because that would help me out a lot if it starts working correctly. I'm not a fan of cutting and nudging only because I end up sitting there for way too long wondering if I need to nudge one more frame or not. I know the bride probably won't notice if the audio is off by a frame...but it will still bother me if it is :)
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Old April 7th, 2015, 10:33 AM   #15
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Re: Audio Drifting Out Of Sync

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This is really helpful information and also makes me wish that Premiere Pro had the same drift correction feature that Vegas has.
In premiere, right click on the audio clip, select "Speed / Duration" from the popup menu then alter the length by the amount of frames it's drifted. Premiere will alter the clip by speeding it up or slowing it down by fractions of a % in order to make it match the length you want. That should fix your drift issue.
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