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23.98 Sequence, Video, 48khz Audio
Ok, this is going to bore the hell out of some of you, but I can’t make sense of the results I have found while searching for the answer to my query.
Basically here is my situation:
I have 16mm film, (obviously shot at 24fps) it was telecined to HDCAM at 23.98.
The audio was recorded seperately and is 48khz.I am working on a 23.98 sequence now in FCP. Do I need to fiddle with audio speed or not?
It’s surprising how unclear this is in the documentation.
Does fcp do an automatic sound pulldown of 0.1% when you dump 48khz into a 23.98 timeline?Cheers.
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5 Replies
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If the audio is brodcast wav file, then in theory FCP should apply pulldown when it goes into a 23.98 timeline. This is the reason FCp applies a frame rate to wavs which is the single greatest contributor to posts here about drifting sync.
Try it and see if it actually does it right, but my inner cynic has doubts. If it doesn’t and the audio drifts, you know the fix is to change the speed to 99.9%.
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Problem is, I don’t know if it drifts. Most of my shots are quite short and the audio tracks only go from Clapper to end of shot. There is no second sync point of reference betweeen video and audio after the first clap. I know this means that I shouldn’t really worry about the audio in this case, that 0.1% over a short shot will not be that noticeable, but you know I want it to sound as good as possible obviously.
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You would need a shot at least a minute long before you would have a 1 frame sync drift. If you don’t then there is nothing to worry about. Also .1% has no appreciable effect on pitch.
If you want to be sure, have a look at the frame rate column and see what it reports for the audio.
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The audio has no frame rate column once it is put into the sequence, however if I look at the actual clip in the bin, ie. not in any sequence, it says TK speed 24 and timecode 30.
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My experience in the past with FCP real-time pulldown has not been good. Although it theoretically can do the job, it will often be inaccurate, especially on short shots. Because FCP is frame based, it can’t always mathematically do a perfect .1% pulldown, if the frame range of the shot is not sufficiently large or a proper multiple of desired speed change. I did this on a project and noticed it was rounding the speed change numbers off target.
So my advice would be to use compressor or Protools or similar to batch process your audio.
Also, make sure you have a 23.98 based SEQUENCE preset selected as your default in the “AUDIO/VIDEO SETTINGS” menu before you import you audio files. (look for the checkmark next to the sequence setting) This will ensure your audio clips are applied the right timebase upon import.
hope this helps,
Matt Lyon
Editor
Toronto
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