3 video clips slowly go out of sync after a few minutes

[Jim Burns]

Hi TIm,

I’m a newbie too so hopefully my limited experience will be of some help.

I noticed that the audio you recorded is at different sampling rates. I expect that’s where the problem lies. I’ve had this problem before and I needed to strip the audio out and convert it to a different sample rate.

The 44.1 kHz is CD sample rate and the 48 kHz isn’t.

Perhaps you can process the odd footage through compressor and resample the audio? Maybe something like FFMpegX would do that for you too. I’m not sure.

Does that help?

Jim

[Michael Largé]

Jas is correct.

It’s your audio having been recorded at different sampling rates which is causing the problem. I experienced this issue in FCP7 as well. As Jas said, take the audio you recorded separately and convert it to 48 kHz. I used Soundtrack Pro and the whole process took less than 30 seconds to fix.

[Tim Welch]

Hey thanks for the guidance. I have finalcutpro x I don’t (at least I don’t think) I have soundtrack pro. I do have compressor. How do I fix it there?

[Michael Largé]

I have no idea how to do it in compressor without also compressing the footage. Jas did say that FFMpeg might be helpful and it appears that’s exactly what you need.

https://www.ffmpeg.org/index.html

Let us know if it works out.

[Jim Burns]

Hi

Actually, I just re-read your message and wanted to clear something up.

Rather then fix the 44.1 kHz audio you should be able to sort the odd 48 kHz to make it 44.1 kHz.

This one > 1.) Canon HF S20 Codec: H.264, Linear PCM filmed at 60i (1080i 29.97fps)1920X1080 Audio 48kHz

ffmpegx is very simple to use. Just back up the video file so you don’t accidentally mess it up and then you can play around with the copy.

I would just drag the file to ffmpeg and it’ll detect the type and sample rates. Then I’d try to figure out how to save the audio at 44.1 kHz by itself, import it into FCPX, and then detach the existing 48 kHz audio from the video footage and replace it with the 44.1 kHz stuff. I think that would work although I’ve only completed a couple of basic tutorials with FCPX.

Make sure you update the post with your experiences as our friend Michael suggests so that someone who searches can help themselves.

Cheers! and happy editing!

[Tim Welch]

thanks Jas,

I was about to try the FFmpegx solution but I think I might have found a better solution. I don’t need the audio at all that is attachted to that clip. All I need is the video since I am using an external audio recording anyway.

I have currently detached the audio from the footage filmed on the Canon and am exporting it at 720p 30fps just as video, then I will reimport it back into FCPX and see if it now syncs up.

I am still open to suggestions. I’ll let you know as soon as this experiment is over if it worked.

It is probably going to be some solution that is like a simple setting adjustment.

The dude at the apple on the phone said it wasn’t a software problem and after asking for guidance about compressor he actually hung up on me. That was a first! 🙂

Cheers,
Tim

[Tim Welch]

Ok exporting the Canon 48k video at 720p with no audio attached and reimporting it to attempt to sync it did not work. It was still drifting even though the 48k audio wasn’t even involved at all.

I am at about 9 hours trouble shooting this one, and I am fresh out of ideas. Any one else have a recommendation?

thanks so much for your help,

Tim

[Jim Burns]

Hi,

Are you sure that there’s really no audio in that new exported file? I know you exported it that way but…

I’d drag it into FFMpegX and see what it detects.

Failing that, I’m stuck but would probably try transcoding all the footage into ProRes 422 using Compressor and sync again.

Jim

[Paul Dickin]

Hi
29.97 ≠ 30?
By about 0.5 sec in 30 mins…

[Tim Welch]

Yeah I think your right about 30fps not being equal to 29.97 as the problem. Unfortunately though, when I convert the 30fps to 29.97 or vise versa and reimport, it doesn’t fix the problem.

The only solution I have come to at this point is to open up the retiming feature in FCPX and setting it to normal. I sync the first part 1080i Canon (29.97)with the footage of the 720p Flip and iPhone. Then I drag the green bar that retimess the 1080i video clip until the audio at the end of the track matches. It seems to fix it although quite tedious.