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Audio drift specific to Final Cut Pro

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Mathew Medeiros
Audio drift specific to Final Cut Pro
on Jan 6, 2011 at 12:43:36 am

I have a very unusual problem with audio sync that I cannot find information anywhere, so here's hoping the pros have an answer. I'm working on a multi-day corporate training video for DVD, and the first four days (of 16) have a significant audio drift that I can't figure out, and it's driving me insane.

The footage has all been shot on an unknown camera; they just handed us all the footage, and it seems the camera recorded onto memory card. Everything was .mpg in 1080, so it was all converted to ProRes LT, 720x480 through MPEG Streamclip for editorial. The last 12 days have no problems with audio sync at all; the edit and DVD encode/burn is perfect.

The first 4 days however, may have been recorded on a different setting or something in-camera. The .mpg files won't open in Quicktime (7 or X), and the only conversion tool that worked was Handbrake. So I ran them through Handbrake, MPEG-4 codec, source-framerate, 100% constant quality. The resulting file would open in Quicktime and had perfect audio sync. It was then converted through MPEG Streamclip like the other files, only difference again was the SD size. Those transcodes also open in Quicktime with perfect audio.

BUT, when I open those first 4 days' Quicktimes in Final Cut, the audio drifts very quickly. Although the clips line up, it seems FCP is cutting the last few seconds of the audio track (the last few words are missing in the presenter's speech). Exporting the audio to .aiff in Quicktime, and matching the exported audio in the timeline shows that there is a 7-8 second drift between the video file on the timeline and the audio file. I don't know how the audio lost its sync from Quicktime into FCP, but I'm hoping someone knows. Otherwise, I'll be spending the next week manually syncing the video and banging my head against the wall.

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Kenny Miracle
Re: Audio drift specific to Final Cut Pro
on Jan 6, 2011 at 3:39:19 am

This happens with mp3's. AIFF & WAV are usually the safe audio formats.
I encountered a similar issue with an AVI file recently & would be curious what others have to say...


Kenny Miracle

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