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.

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.

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.

Ron Evans

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.

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

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.

Check out Pluraleyes by Red Giant, made for the purpose. I assume there is an FCP version, it works a treat in Premiere.

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.

Ron Evans

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.

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.

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.

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)

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.

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.

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.

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.
I'm new to fcpx so I can't rule out user error but it wouldn't sync anything. Where as pluraleyes versions 1 partially synced them in fcp6. I was also testing pluraleyes 3. That worked the best but wouldn't import into fcp6 got a xml error. This might be because upgrading to Yosemite broke xml. I see that newer has an audio replace feature ppl were talking about.

I synced a GoPro with audio from a small recorder on a boat and was amazed that FCP-X was able to sync all six clips despite the sound of the engine and the usual muted audio of an encased GoPro.

I posted this elsewhere on the forum, but here's the result with one of the clips.
Test sync - YouTube

This is totally OT, but.......If I found a life preserver in open water I would have spent at least a few minutes looking around the area to see if anything else was floating nearby. You obviously assumed it blew out of a boat which it probably did....but hey, it IS a life preserver.

Steve

We did look. And I radioed it in to the USCG, too.

This is totally OT, but.......If I found a life preserver in open water I would have spent at least a few minutes looking around the area to see if anything else was floating nearby. You obviously assumed it blew out of a boat which it probably did....but hey, it IS a life preserver.

Steve

In this business you either sink or swim. ;-)

You mean sync or swim? :-)

In this business you either sink or swim. ;-)

Sync or sink.

You mean sync or swim? :-)
Lol

I had to stop playing around with trying to do a sync multiclip so I could get this out.

I figured things:
1. Using Fcp6 I extracted the board/shotgun audio from the primary camera movie and exported a stereo pair audio file for each.

2. After I entered the clips angle field fcpx synced it (missed this step before).
In the timeline I used the extracted audio in the previous step, enabling me adjust/mix the ambient and board feed independently.

I really love how fcpx audio level adjustment works. Color of the wave form indicates problem areas and selecting range tool creates the keyframes automatically. So much quicker.