FORUMS: list search recent posts

audio-video synch when moving between MP4, .MOV, and MP4

COW Forums : Apple Final Cut Pro Legacy

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Theo Acorn
audio-video synch when moving between MP4, .MOV, and MP4
on Mar 2, 2012 at 12:49:18 am

I am assembling a montage of footage from a variety of sources and in a variety of resolutions, mostly originating in .mp4. To avoid rendering, I thought it advisable to convert all the footage to 720 x 1280 .mov, so I used Compressor to do this using the ProRes LT codec.

The conversion worked in the sense that the video all dropped into the timeline without the need for rendering. But—strangely, I thought—the audio needed to be rendered. And once I had done so, it appeared to be out of synch from the video. When I examined the item properties of these converted files in Final Cut Pro, I saw that the vid-rates seemed to vary slightly from my 29.97 timebase -- some reading 30.2, some 29.4. I assumed I had done something strange with Compressor (although I can't think what—I used a template setting) so I manually went through and re-synched the audio for each clip by slightly altering it's speed.

At this point the audio and video were synched up for each clip and I was able to edit seamlessly. I went to output—and the file that came out wasn't synched up! More specifically, the sound in the exported file matches the sound in my Canvas, but the video clips don't match. Now it's as if the video itself had been running too fast in the timeline, and the edits I thought I was making actually linked up to different parts of the underlying footage. (A little hard to conceptualize).

I'm not sure what to do because I don't know what is going wrong. Any assistance would be appreciated.

Return to posts index

Michael Gissing
Re: audio-video synch when moving between MP4, .MOV, and MP4
on Mar 2, 2012 at 3:34:07 am

Is all the audio 48khz? FCP will not like audio that is compressed like mp3 or aac and the sample rate must be 48khz and the sequence set to 48khz.

Not sure about the strange frame rates. Don't trust quicktime to report frame rate or frame sizes accurately

Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2018 All Rights Reserved