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FCP7 not recognizing video after replacing audio with ffmpeg

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Kahlil Robinson
FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 13, 2014 at 9:29:30 pm

I work with audio and video that are recorded with separate devices. I use ffmpeg to replace the bad camera audio with a clean track without re-encoding anything so it's completely lossless.
ffmpeg -i INPUT.MOV -i INPUT.WAV -map 0:0 -map 1 -c copy OUTPUT.MOV
Once in awhile, I run into a batch of video that FCP7 won't recognize after replacing the audio. It drives me crazy because in this scenario, I have to manually sync the audio in Final Cut, which renders the waveforms totally wrong so I have to actually listen and adjust. Takes up a lot of extra time and if the audio is accidentally moved out of place, there won't be an offset count to catch my eye.

There is no system but GNU and Linux is one of its kernels.


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Nick Meyers
Re: FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 14, 2014 at 12:01:29 am

cant help wot the ffmpeg part,

but in response to this:
"if the audio is accidentally moved out of place, there won't be an offset count to catch my eye."

after syncing, you select video and audio and LINK them (command L)
gotta do it one at a time.

to be totally thorough, copy the new linked clips into new bin.
These are your new master clips.
Then edit back into the timeline


"Takes up a lot of extra time"

how so?
why is ffmpeg so fast?
what is it using to sync the audio?
maybe FCP has something similar you are not aware of. (although i doubt it)


nick


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Kahlil Robinson
Re: FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 14, 2014 at 7:18:39 pm

Takes extra time because I have to manually sync the audio for every video clip that I want to use, and the waveform for standalone WAV/AIFF audio almost always renders wrong, which also creates problems when I mess with the audio. Works fine if I'm using the audio in a video file.

ffmpeg is a command line tool for manipulating audio and video. I use it to copy the video stream and new audio stream into a MOV container. Since the streams are copied and not encoded, it doesn't take very long. Usually only a few seconds unless it's a huge file. Maybe I should repost or have a moderator move this to the ffmpeg section (is there one?). I suspect there is some proprietary QuickTime data that is being missed by ffmpeg, but it usually works fine.

There is no system but GNU and Linux is one of its kernels.


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Nick Meyers
Re: FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 15, 2014 at 12:54:21 am

But my main question is how do you establish sync in ffmpeg?

Does TC match? Then you can use that in FCP, too
Do they have the same start point? Then you can use that in FCP
Maybe you are using waveforms to sync, in which case you can do that in fcp via Pluraleyes,
Or in FCP X

Nick


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Kahlil Robinson
Re: FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 15, 2014 at 1:09:12 am

I use Audacity to sync and process the audio (noise removal and dynamic range compression) then use ffmpeg to dump the video stream and new audio stream into a new MOV file (then pray that FCP will accept it). The audio is just raw PCM, 16-bit 48KHz so it's not a codec issue.

There is no system but GNU and Linux is one of its kernels.


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Matt Lyon
Re: FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 15, 2014 at 12:40:47 pm

Before you address the ffmpeg issue, I think you need to figure out why FCP is drawing the waveforms wrong. That shouldn't happen. It probably means the audio is being imported incorrectly (assuming their isn't an issue with the files themselves). Incorrectly drawn waveforms might point to a frame rate mismatch issue, which I discuss in my tutorial: https://library.creativecow.net/lyon_matt/fixing-fcp-assets/1

But for syncing, I wouldn't mess with ffmpeg. Since it sounds like you are simply syncing the clips to the first frame of each media file, the workflow in FCP is pretty quick: Import the processed audio tracks in to FCP. Then you can strip the "bad" audio tracks off the video clips by throwing the files on to a timeline, deleting the audio tracks, then throw the "clean" clips into a new bin, then use the "merge clips" command to sync the video-only-clips with the new audio files. It doesn't take that much longer then typing out a terminal command.

Matt Lyon
Editor
Toronto


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Kahlil Robinson
Re: FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 15, 2014 at 11:46:34 pm

ffmpeg doesn't sync anything, it merely replaces one audio stream with another (which are perfectly synced in Audacity and are identical lengths with same bit depth and sample rate). Every file that I've done this with opens fine and plays correctly in QuickTime. Sync is good, no lag or dropped frames (ffmpeg would have given me warnings beforehand). It's just the occasional batch of clips that FCP won't accept after this process. I would guess it has something to do with the type of camera and how it encodes the video. Perhaps in the future I will make an ffmpeg log of each file and see if there's any kind of pattern.

There is no system but GNU and Linux is one of its kernels.


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Michael Gissing
Re: FCP7 not recognizing video after replacing audio with ffmpeg
on Nov 17, 2014 at 8:37:13 pm

Could the issue be the codec of the video?

Quicktime pro also allows you to add or replace an audio track with a new one without transcoding.


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