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Vanessa McDonnell
FCP sync problem
on Apr 14, 2011 at 8:09:29 pm

I am having a very mysterious problem with sync in FCP and I would really appreciate some input.

This is what's happening: I'll edit an audio clip or a clip containing synced video and audio into my timeline, I watch/listen and it is normal. Then at a later point I'll notice during playback that, starting at the beginning of a given clip, FCP will be playing back a completely wrong bit of audio which should actually come later on in the clip. Then, partway through playing the clip, it will suddenly start playing the correct portion of audio. I can go back with the playhead and hear the error again and again in the same exact way, so it's not a temporary playback or system glitch.

If I go to the beginning of the clip and hit F for Match Frame, the source clip loads correctly into my viewer and I will hear the normal, correct audio for the clip from beginning to end. If I toggle on visible waveforms in my sequence and examine the clip, I can see that the correct waveforms are there for what I should be hearing, and that the portion of the clip that is playing back incorrectly does NOT match the waveform. If I double click the clip in the sequence so that it loads into my viewer FROM the sequence, the waveforms again are correct for what I SHOULD be hearing, but the audio plays back incorrectly and what I hear does not match the waveform. When I put the playhead to start playing at a point just before my starting IN point there, the correct audio begins to play but then as soon as the playhead reaches my IN point it abruptly starts playing the wrong audio. The wrong audio plays for several seconds, sometimes 3 seconds, sometimes 6, it seems random. If I drag back the in point in the sequence to a point before my in point, the correct audio will play back normally until the playhead crosses my in point, at which point it will be wrong.

It's as if FCP is randomly directing itself to slip or roll and then repeat a portion of audio at the beginning of some clips. The overall percentage of occurence is pretty small, but it is really bothersome because I have thousands of clips and I never know when this might happen.

The only way that I can correct it is by going to the start of the clip in the sequence, hitting match frame and then F10 to overwrite the clip with the source clip, which will then play back correctly.

The vast majority of the material that I'm working with are merged clips, and I assumed this was the problem somehow. However, this has happened to an audio clip that was pulled from a CD. (By merged clips, I mean that I had to manually sync all of my audio to my footage in FCP - I'm working with telecined 16mm footage).

If anyone has had this problem or has any ideas I would love to hear from you!
Thank you,
Vanessa


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Dave LaRonde
Re: FCP sync problem
on Apr 14, 2011 at 8:34:31 pm

Information about your system, external drives & connections, OS version, FCP version, the codec of the video footage being edited, and the file type of any other audio files being used will be a great help in an accurate diagnosis.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Vanessa McDonnell
Re: FCP sync problem
on Apr 14, 2011 at 9:16:12 pm

Thanks Dave. This is my set up:


MacBook Pro
OSX 10.6.4
FCP 6.0.6
Using 1 external drive via FW 800
Drive is a Glyph GT050Q
Video is 23.98 DV/DVCPRO - NTSC (digitized from tape w/FCP)
Most of my production audio consists of 48KHz WAV's, most with 4 discrete tracks (the problem always happens to all tracks). The problem has happened with a stereo AIFF containing 2 tracks as well, however.

The problem always happens in a sequence, never to a source clip (or to the merged clips that I'm treating as source). I can copy and paste the problematic clips into new empty sequences and the problem remains.


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Dave LaRonde
Re: FCP sync problem
on Apr 15, 2011 at 1:53:04 am

Since none seem to be forthcoming, being short of an actual authoritative answer, I would do the following in this order:

Quit FCP, restart and see if the problem persists. If it does....
Restart your machine, open the project, and see if the problem persists. If it does....
Shut down the machine. Go out and have some coffee. Start it up, open the project, and see if the problem persists. If it does....
Trash your FCP preferences, shut down your machine, start it up, open the project, and see if the problem persists.

And if it does, I'm out of answers. Perhaps someone else has one.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Michael Gissing
Re: FCP sync problem
on Apr 15, 2011 at 2:01:37 am

Couple of thoughts. Is the DV audio 48khz or 32khz. Was the DV shot at 23.98? I didn't know that frame rate was available for DV. Check that the frame rate and the sequence matches. Finally absolutely check that all audio is 48khz and only 16 or 24 bit. Any compressed formats like mp3 etc can cause problems. If any audio had to be rendered then that may be a clue that there is a mismatch. Is so fix the files in Compressor and re edit in. Finally trash the audio renders and redo (although it shouldn't be necessary to redo if all matches.

As Dave said, usual maintenance of trashing prefs and repairing permissions may also be in order.


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Vanessa McDonnell
Re: FCP sync problem
on Apr 15, 2011 at 3:01:49 am

Thanks so much Dave and Michael, I appreciate your input.

Dave - I've restarted many times over the long period that I've been working on this project and the problem still pops up periodically. In fact I notice that something that was fine yesterday is not fine today after a restart. But I will definitely try trashing my preferences.

Michael - all of my audio is 48khz and 24bit, and I've never had to render it when putting it into a sequence. That being said, I do know that some of my audio was recorded at 24 fps and some at 30 fps. I actually don't know if that even means anything at all since audio does not exist in frames - but this was a 16mm film shoot with audio recording on a separate digital system and I know that we had a fill-in recordist use a 30 fps setting instead of 24 for part of the shoot. Again I don't know that it means anything, it doesn't even seem as though FCP stores this data.

Our video is 23.98 because I processed it through cinema tools to remove the pulldown. We had our 16mm film telecined and received miniDV tapes. I digitized those and the original clips were 29.97 from tape. Then I processed through Cinema Tools to get the 23.98 video files, which I then synced to our audio and used the Merge Clips function.

99.9% of the audio files I'm working with are the production sound files described above, but I have a few other random audio files that I'm trying out as temporary sound that are from CD's or from a portable digital recorder. The problem affected one of these files for the first time the other day so this made me think that the problem is not related to any specific file type or the fact that I'm working with merged clips. It made me think that it must be some kind of larger, overall FCP problem that can affect any sound file that is within a sequence.

And just as a footnote, I've never had the slightest problem with any of my merged clips drifting out of sync over time.

Thanks again guys!


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Dave LaRonde
Re: FCP sync problem
on Apr 15, 2011 at 5:45:58 pm

[Vanessa McDonnell] "I have a few other random audio files that I'm trying out as temporary sound that are from CD's or from a portable digital recorder. "

...and if these happen to be compressed audio files (mp3, ac3, etc.), they could be the culprits. FCP simply does not play nicely with compressed audio.

If you have such files in the project, convert them to aiff, 48kHz, 16 or 24 bits.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Gregory Scharpen
Re: FCP sync problem
on Jun 6, 2011 at 7:26:25 pm

Hello --

I'm experiencing the exact same audio slip issue; and I've experienced it multiple times in a sequence with audio coming from a variety of sources. Imported audio, dig'd-from-tape material, etc. I'm working with FCP 6.0.6 on a Mac PowerPC G5. I've been having to re-cut in the audio from the original clip to fix the problem; but then it crops up elsewhere in the sequence when my back is turned. I've also noticed that if I have a clip in the sequence, and try to move it a few frames left or right, the problem suddenly inserts itself. Undo that, and the problem goes away. I've had to do some contortions to move everything else in the sequence AROUND that piece of audio to close up gaps and make the edit work, rather than move that one piece of audio, which would be the simpler thing to do.

I haven't had a chance to find any solution or person who'll tell me why this might be happening, but I thought I'd at least let you know you're not alone with that issue.

-Gregory Scharpen


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David Roth Weiss
Re: FCP sync problem
on Jun 6, 2011 at 8:48:37 pm

[Gregory Scharpen] "I've experienced it multiple times in a sequence with audio coming from a variety of sources. Imported audio, dig'd-from-tape material, etc. "

You'll have to be more specific if you want a specific answer to the issue you're facing. The various types of audio sources and their sample rates are important.

In addition, what various video codecs were imported? Were you editing any h.264 or MP4 files in your sequence?

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
http://www.drwfilms.com

POST-PRODUCTION WITHOUT THE USUAL INSANITY ™


Creative COW contributing editor and a forum host of the Business & Marketing and Apple Final Cut Pro forums.


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Vanessa McDonnell
Re: FCP sync problem
on Jun 6, 2011 at 9:57:40 pm

Hi Greg - Although I still don't have an actual explanation for this glitch I was able to stop it from happening by using render manager often to clear out ALL of the audio render files from my project. So most likely it was caused by a bad render file.

It did not work to just clear the render files that corresponded to the sequences where the problem was happening - I had to check-mark the entire project in render manager and delete all the audio render files and then immediately close and reopen the project.

I started doing this at least weekly and the problem hasn't come up again since. My project is massive with hundreds of sequences and many of my sequences contain many tracks of audio, therefore needing to be rendered for playback. Not sure if this applies to your project but I hope this works for you!


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