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Old August 3rd, 2015, 09:40 AM   #1
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Syncing Audio

Is it possible to adjust the audio in the video file without recompressing the video?

I record theater work, I put the board feed in one channel and my shotgun mic in the other. The channels are off by 3 frames and when I try to sync it with another camera doesn't work properly. I'd like to adjust and export the audio update the video file with it so now it can be synced as a multiclip with the other camera. Btw this is on a mac fcp.
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Old August 3rd, 2015, 10:08 AM   #2
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Re: Syncing Audio

I don't know very much about FCP except it has very limited audio capabilities.
Otherwise I would figure out the offset you want, and compensate in your favorite audio editor by adding/removing frames/samples from the head. Re-save the audio in the appropriate format and mux it back in with the video.. which is unaffected.

Note: Render an PCM audio copy before hand in case you wish to go back or re-adjust the off-set.
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Old August 3rd, 2015, 10:26 AM   #3
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Re: Syncing Audio

I use a PC but also have the same situation. I export the audio and resync in an audio editing program ( Vegas in my case ) then bring back into my editor ( EDIUS ) Most audio editing programs can shift tracks into sync so you could do the same thing on the Mac.

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Old August 3rd, 2015, 12:44 PM   #4
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Re: Syncing Audio

The "muxing" back into the video is what I'm interested in.

I can offset the tracks in fcp6 timeline but video syncing software such as pluraleyes or internal syncing of FCP X for multi camera editing sync from the source video files. That's why I need to update the video files.
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Old August 3rd, 2015, 12:51 PM   #5
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Re: Syncing Audio

Just get them in sync in the timeline and export a new file. If its like mine its the board sound that will be in sync with video because of the delay of sound getting to your mic on the camera.

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Old August 3rd, 2015, 01:17 PM   #6
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Re: Syncing Audio

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Originally Posted by Ron Evans View Post
Just get them in sync in the timeline and export a new file. If its like mine its the board sound that will be in sync with video because of the delay of sound getting to your mic on the camera.

Ron Evans
I ended up doing that but I'm looking for a more efficient way to avoid reencoding the video, takes a long time and degrades the video a bit. But it's mainly the 3+hr wait to just tweak the audio.
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Old August 3rd, 2015, 02:28 PM   #7
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Re: Syncing Audio

Check out Pluraleyes by Red Giant, made for the purpose. I assume there is an FCP version, it works a treat in Premiere.
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Old August 3rd, 2015, 03:21 PM   #8
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Re: Syncing Audio

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Originally Posted by Pete Cofrancesco View Post
I ended up doing that but I'm looking for a more efficient way to avoid reencoding the video, takes a long time and degrades the video a bit. But it's mainly the 3+hr wait to just tweak the audio.
I end up syncing my multicam manually as all my cameras start and stop at roughly the same time so are easy to sync. As you noted there is a 3 frame difference from board sound so Pluraleyes could also be out by this amount from true sync with audio.

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Old August 3rd, 2015, 05:10 PM   #9
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Re: Syncing Audio

Normally I shoot both cameras continuous but I was experimenting with Dslr that has 14 separate files so I don't want to manually sync.

I also used a Zoom H1 for the first time. I forgot if it drifts over 1hr continuous recording?

Audio for musicals can get complicated. The board feed is only the wireless lavs and doesn't include music or applause and isn't good for action scenes. I also discovered they left on the announcer mic on because I can hear the director whispering during the quiet scenes. My main camera got clipped during loud shouting scenes. I can fix most of this by fading to the best audio source for each situation but man is it a mess just to get the audio right.
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Old August 3rd, 2015, 06:28 PM   #10
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Re: Syncing Audio

I do most of my audio in Vegas because it has the capability to stretch or squeeze tracks to regain sync due to clock differences ( like the Zoom compared to the video camera. I have a H4N and an R16 even video camera to video camera over an hour or so. ) Yes lots of short clips not continuous you need something like Pluraleyes to get sync. I shoot theatre with 4 cameras all started and stopped about the same time so sync the video is not difficult.
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Old August 3rd, 2015, 08:54 PM   #11
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Re: Syncing Audio

I also work in Vegas, where something like a timing difference between the two audio tracks of a video file is extremely easy to adjust.

If you want to avoid the time and degradation of re-rendering a new video source file, can't you just render out the ambient camera mic track as a separate audio-only file?

Then mute the original delayed ambient camera mic track that's part of the original video file. Use only the board feed with the original video and use the new separate audio-only file of the ambient mic as a separate track on the timeline that could be shifted independently.
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Old August 3rd, 2015, 09:43 PM   #12
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Re: Syncing Audio

I think the OP is asking if it's possible to change the audio without re-rendering the video (generational loss).
If this is correct .. Mux in the audio as I previously stated... f__king twice !
(Rick out.. no more comments)
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Old August 3rd, 2015, 11:44 PM   #13
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Re: Syncing Audio

I understand what the OP is asking and I understand your suggestion to remux the audio, I just don't think it's necessary to remux it while working on your own timeline.

Unless there is a need to send the modified video file with newly adjusted audio timing as a complete package, or the NLE being used is audio-crippled, I wouldn't remux.

But that's just my personal preference since I'm doing all my own editing in Vegas and I don't use remuxing programs enough to be 100% confident that I've got all their many settings correct.
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Old August 4th, 2015, 12:00 AM   #14
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Re: Syncing Audio

Sorry, I guess I'm back..
Re-muxing is totally external in my 'PC' world, using a separate application.. be it 'TX muxer' or 'MeGUI'. both of which will replace the audio, w/o re-rendering video content.
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Old August 4th, 2015, 12:17 AM   #15
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Re: Syncing Audio

FCP-X will easily sync multiple sources. As you said, one of the audio tracks is out by 3 frames, and that will create an "offset" for that track.

Otherwise, the sync (using audio as a guide) is quite precise.
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