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Need tips for syncing A/V for multicam

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Andrew Kimery
Need tips for syncing A/V for multicam
on Mar 10, 2018 at 4:26:51 am

Looking for some multicam tips. I have a series of interviews (three so far) that are single camera, but have external audio. They were not TC jammed, but the camera recorded reference audio. The camera and audio recorder stop/start a few times during each interview.

When I try to use X's multicam tool to sync by audio it only manages to sync about half of the clips. I've given everything an angle and selected the option to tell X to use the angle info (as opposed to leaving it on "automatic"). Someone on FB suggested adding a marker near all the slate points, but I haven't had a chance to try that yet. Someone else suggested PluralEyes, but this is just a side gig so dropping $299 on PE isn't viable. Any others suggestions to help this automated process be more accurate?

I tried the same clips in PPro and it had no problem syncing it all up (and in less time). I XML'ed the synced A/V from PPro into X and it gives me a project w/all the A/V in sync so is there a way to turn that FCP X project into a multicam clip?


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Tangier Clarke
Re: Need tips for syncing A/V for multicam
on Mar 10, 2018 at 4:59:55 am

Andrew it seems like your problem may be just syncing the correct pieces of video with the correct pieces of audio. Since you have start and stop situations my suggestion would be this:

  • In icon view identify each interviewee and give them separate angles. So you may have Angle A for all clips of person A, B for person B, etc.
  • You won't be able to visually identify audio the same way so quickly, but hopefully your clocks were close on the camera and audio recorder. So switch to list view and sort by date created. and you should see some sort of a pattern where you'd be able to identify which audio goes with the appropriate interviewee.
  • Select those audio pieces for one person and give them an angle (A-Audio perhaps)
  • Repeat for isolating person B audio, person, C, etc.
  • Once you're done you should be able to select all of the elements for one person and create a multicam. Repeat for each person.


This is all assuming you're trying to break down your interview clips this way. When I first read your post I thought, there should be no problem if you're just looking for a multicam of everything. Just make all the video angle A and all of the audio angle B and FCP X shouldn't have any issues figuring it out. I've done this many times, thought I do tend to break my own down into separate interviews like above.

I've never had too much success with multi cams from PluralEyes. Not a big fan of it. It tend to give me a timeline of everything when what I actually need are individual multicam clips in the browser.


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Andrew Kimery
Re: Need tips for syncing A/V for multicam
on Mar 10, 2018 at 7:44:57 am

Thank you for the post, Tangier. Unfortunately I already tried just doing one person's A/V at a time and didn't have much luck with it.


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Joe Marler
Re: Need tips for syncing A/V for multicam
on Mar 10, 2018 at 1:04:38 pm

[Andrew Kimery] "I've given everything an angle and selected the option to tell X to use the angle info (as opposed to leaving it on "automatic")"

Are you sure you did this for *all* clips? Each audio recorder must have all its clips uniquely labeled in Inspector under Camera Name or Camera Angle. Obviously you can select the entire batch of clips in the Event Browser from a single camera or a single audio recorder and label them.

Provided they are labeled correctly I've had pretty good results with FCPX syncing multicams via audio -- using fully automatic. However I usually have an unbroken channel from an audio recorder.

You are correct you can use *both* "First Marker On Angle" *and* audio sync. The markers will fine-tune the area FCPX uses to examine for audio sync. These markers need not be placed exactly: https://support.apple.com/kb/PH12585?locale=en_US

If you have several short "junk" clips, try omitting those from the sync. Those can throw off the sync attempt.

You can open the MC clip and check the sync and attempt a selective re-sync inside the clip. To do this:

- Inside MC clip select monitoring angle by clicking the little TV icon at the left of its timeline. This can be audio or video and need not be the same for each re-sync attempt. You're basically telling it "within this MC, sync this clip to that one".

- Click a different clip you want to re-sync. Then click the clip label at left and select "Sync Selection to Monitoring Angle". It will re-sync only the selected clip to the monitoring angle.

If you didn't have an unbroken audio channel, you may need to repeat this to sync each group of clips that were running at a given time.

I previously tested FCPX's audio sync vs Premiere on some difficult cases and they seemed roughly equivalent. However Premiere would tell me if a clip failed to sync, whereas FCPX would silently guess and place it somewhere on the timeline.

Even if audio *levels* are OK but one audio source contains lots of echo and other noise, sometimes the sync will fail. E.g, at a concert or large wedding reception where two cameras both have good audio levels but are widely separated. If one is close to a PA speaker and the other highly echoed slightly time-delayed sound, the audio sync may fail.

PluralEyes is better at this but it can be a hassle to use since it doesn't support syncing from the FCPX Event Browser, which is the normal workflow. You have to start with your media in Plural Eyes, sync and import to FCPX, or start in FCPX with your media on the timeline and round trip to Plural Eyes. It is designed for the typical track oriented NLE workflow.

That said, Plural Eyes is very powerful and can match hundreds of clips in a single batch. If your audio recorders were not set to the correct date/time and the clips were not placed in correct folders, Plural Eyes can search across every A/V clip from an entire project and sync them. It also does continuous sync drift correction.

The Plural Eyes audio search is many-to-many, and can be pretty slow if matching hundreds of clips. Normally you don't need that but sometimes you have a lost audio clip without correct date/time and need to find what matches it. I have requested they add a feature to search for a waveform match between one selected clip vs a large pool of candidate clips. This should be possible at much higher performance.


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Andrew Kimery
Re: Need tips for syncing A/V for multicam
on Mar 11, 2018 at 3:08:45 pm

Thanks for all the info, Joe. I'll give your suggests a shot and report back.

I'll also submit a feature request asking Apple to improve their sync-by-audio feature so hopefully it can become more on par with PPro and PluralEyes.

I started using PPro CC regularly about four years I routinely give it 100+ clips to sync (I think the most I've done is 250) and it nails it 99% of the time. What I don't like about PPro is the work I need to do to clean things up after the sync. I was hoping X would save me time on this front, but if I have to do a comparable amount of prep prior to sync in X then it's a bit of a wash time wise. We'll see though.

Worst case I'll just use PPro for this project (since I do have a bit of a deadline) and I'll save X for some other projects that don't have hard deadlines (so I won't have to worry as much about the learning curve).


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Joe Marler
Re: Need tips for syncing A/V for multicam
on Mar 12, 2018 at 1:42:03 pm

[Andrew Kimery] "What I don't like about PPro is the work I need to do to clean things up after the sync. I was hoping X would save me time on this front, but if I have to do a comparable amount of prep prior to sync in X then it's a bit of a wash time wise. "

With FCPX you normally have to tag all clips with a camera name or angle name before doing the sync. If a camera emits metadata that FCPX understands, this isn't required, but usually it must be done. It's a quick procedure if each batch of clips has a unique filename convention or you tagged them on import. In the Event Browser using List View, just group select all clips from a given camera and enter a unique camera name or angle name. IOW if you have three cameras you can batch-tag all clips for a multi-day shoot in only three steps.

If they are properly labeled, usually FCPX does fairly well. Like Premiere, FCPX does not compensate for sync drift. Premiere notifies you of a clip sync failure, whereas FCPX just takes its best shot and places it on the timeline, intermixed with all the other successful syncs.

With any of these audio-sync products they work better if you have longer clips or ideally a continuous audio channel the other cameras and recorders can sync against. So one solution is just leave an audio recorder running.

We shoot a lot of three-camera interviews and if multiple takes are required we might stop the multichannel audio recorder in between. Some cameras may have a false start as the operators adjust them, but even with all this it's uncommon to have more than about 15 clips per interview.

Some cameras will segment logically contiguous clips into separate files, which can be harder to manage. Where possible we configure the cameras to not segment files.

In a succession of multi-cam interviews I always sync each one separately. If we have back-to-back interviews with the same setup, I don't try to sync multiple interviews in one pass.

100 to 200 clips is a lot to sync in one operation. I would normally use Plural Eyes for that. It requires no prep whatsoever, you can just drag in a huge pile of clips and it will try to figure out how many cameras and recorders. However if you have multiple similar cameras, e.g, GH4 and G7 or A6500 and A7RII, the files internally look alike -- bitrate, bit depth, chroma sampling, codec id, etc. are identical and there's no differentiating data in the video header. Even Plural Eyes cannot always put them in the right group. So some form of manual organization before import is often needed.


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