changing the speed of video or audio

Posted by zipperplug 
changing the speed of video or audio
March 18, 2011 03:08PM
Hey folks - I am trying to change the speed of my video and audio to take care of a sync problem.

I figured out that the speed needs to be adjusted to 99.895833% to match the audio which was recorded at a different frame rate, but when I tab to a different field, FCP rounds the number to 99.90%.

Is there a way to stop this?

It happens even when I control-click the clip in the timeline to change the speed.
Re: changing the speed of video or audio
March 18, 2011 03:18PM
You're better off adjusting the audio to match the picture. A video speed change of just a few per cent, performed in FCP, will look awful especially over the course of a long-running clip.


www.derekmok.com
Re: changing the speed of video or audio
March 18, 2011 03:24PM
Thanks Derek,

I tried to adjust the speed of the audio the same way, but I too get the "rounded" percentage number.... It needs to be exactly 99.895833%. Ideas?
Re: changing the speed of video or audio
March 18, 2011 03:25PM
Time stretch the audio in soundtrack pro



www.strypesinpost.com
Re: changing the speed of video or audio
March 18, 2011 05:34PM
one approach to this is to use FIT TO FILL.

i find an accurate sync point as close to the beginning of the clip as possible,
and another one as close to the end of the clip as possible.

generally i'll do this in the timeline, and use markers on the audio

then i mark those sync points with in/out points.
on the pic in the timeline,
and on the sound in the viewer
(as i've added markers in the timeline, i generally double click the timeline version into the viewer, alternatively, i'll trim my sound to the sync points in the timeline, then open in the viewer)

then i do a FIT TO FILL edit, which stretches the sound to fit to the picture.


99.895833% vs 99.90%

that's 1 frame every 100,000 frames,
or a frame over an hour.
how long is your piece?


nick
Re: changing the speed of video or audio
March 19, 2011 01:54PM
The issue is that the video was recorded at 23.976 and the audio was 29.97. There is a noticeable drift after about a minute or so.

I tried the FIT-TO-FILL option, and it did not work. In fact, when I did it, the audio block in the timeline still shows that the audio is playing at 100%, as if no audio was stretched.

The clips are also in WAV format and Soundtrack Pro (which I've never used) is saying it only accepts AAF or OMF? Is that true? Searching on the Soundtrack Pro forums now.....
Re: changing the speed of video or audio
March 19, 2011 05:13PM
That won't be the issue. You probably recorded at 30 fps, not 29.97.



www.strypesinpost.com
Re: changing the speed of video or audio
March 19, 2011 08:56PM
yes 30 FPS - my misake
Re: changing the speed of video or audio
March 21, 2011 06:51AM
Google for convertTo, it's somewhere on the Avid support site.
convertTo is a set of AppleScripts which do allow to change playback speeds of broadcast wave files (BWAV,BWF) without resampling them.
It's done by changing the file header info for the playback sample rate.

Andreas
Re: changing the speed of video or audio
March 21, 2011 07:20AM
Ooh. Now that you mention it, there's wave agent which let's you modify the headers on a WAV file.



www.strypesinpost.com
Re: changing the speed of video or audio
March 21, 2011 07:49AM
You're right. You can change the frame rate and keep TC.

Andreas
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