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Wednesday, September 18, 2013

Mixing: Audio Desync Problem

It seems that Final Cut doesn't like the 23.98 frame rate and since it's the frame rate of all the film's footage, we had a big problem to synchronize the output video file with the audio file after mixing. And since we spent so much time trying to figure it out, we thought of sharing it with everybody in order to avoid it in the future :) So because the camera's frame rate is not actually 24 like cinema cameras but 23.98 like most digital cameras, this 0.02 difference causes an audio "desync" problem with the video file when they are both imported again to final cut for the final export.

The audio mixer Samir Nabil and I, tried to find a solution for this problem and after many days the only thing that worked was to convert the video file's frame rate to 24p using Cinema Tools. The process is called either pull-up or pull-down but I always forget and get confused which is which :) You should either do it to each video file on your timeline or with the final video and this is what we did and we should have done that before starting audio mixing.

The film's quick time video file had to be exported with the codec Apple Pro Res, then opened with Cinema Tools. In Cinema Tools all we had to do was to conform the frame rate to 24p. During the process we also learned that you have to make sure that the Sequence Settings have to match the footage settings, the Audio/Video Settings including the Capture Preset (even if you are not capturing any footage) or you can edit on Avid if you can afford it :)

2 Comments:

Aida Elkashef said...

which camera was that? because most digital cameras are actually 25fp? if it was any of the canon dslrs, then u had to convert the raw material before doing anything to begin with, as final cut does not support H.264 as most ppl think (and even though it is listed in the codecs in FC) and so the best way is to convert the raw material to apple pro-res before logging it to FC.
that if u were using canons. if not then which camera was it?

Mayye Zayed said...

This was the DSLR Canon 550D and I don't really think that most of the current digital cameras shoot in 24p like the blackmagic and FS100. Even the relatively small camera VG20 has 24p as far as I know. Which digital cameras do you mean ? We did convert the material to H.264 but this is not because Final Cut doesn't support it but because it will need to be rendered more often. You can edit with the H.264 if you want. I did this myself many times. So we did convert the footage to Apple Pro Res before logging it but what I'm talking about here in this post is another problem we faced after exporting the video file with a frame rate 23.98.

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