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44.1 KHz audio in 48 KHz timeline

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Bobby Hall
44.1 KHz audio in 48 KHz timeline
on Sep 15, 2015 at 1:56:19 am
Last Edited By Bobby Hall on Sep 15, 2015 at 1:59:26 am

I'm editing a music video in FCP 7 and the song is a 44.1 KHz 24-bit .wav file. The sequence settings for the video are 23.98 fps and 48 KHz 16-bit audio. I haven't experienced any sync issues. I was just wondering why the length of the song seems to change. When I right click the song on the timeline, it's about 10 frames shorter than it says in the browser. So I was just wondering, if you drag 44.1 KHz audio onto a 48 KHz sequence, does it change the speed of the song? If it does, I can't tell by listening.

I wanted to test what would happen if I dragged the song onto a sequence that didn't already have sequence settings matching footage, and it listed the correct time of the song. It showed the same length as in the browser. Even though the song is 44.1 KHz the sequence settings show 48 KHz. I thought it would've asked me if I wanted to match the settings to the file but I guess it doesn't ask you that with audio...?

Anyway, I thought the difference in sample rate might be the reason for the different lengths of the song, but both sequences are 48 KHz 16-bit, so that can't be the reason. The only other reason I can think of is that the first sequence, the one with the footage, has a frame rate of 23.98, and the second sequence I made was 29.97. Is the difference in frame rate the reason why it's showing me different lengths for the song? And is it actually slowing down the song?

I'm confused by what's going on because everything is perfectly in sync. The only reason why I was curious about this is because I noticed the different length of the song on the timeline compared to the browser. Thanks!


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David Roth Weiss
Re: 44.1 KHz audio in 48 KHz timeline
on Sep 15, 2015 at 3:01:16 am

Don't sweat it Bobby, the only thing issue you may have is possibly having to render the audio. If you're really concerned, open the 44.1khz track in QT Player and export from there at 48khz.

David Roth Weiss
Director/Editor/Colorist & Workflow Consultant
David Weiss Productions
Los Angeles


David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.


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Bobby Hall
Re: 44.1 KHz audio in 48 KHz timeline
on Sep 15, 2015 at 4:55:34 am
Last Edited By Bobby Hall on Sep 15, 2015 at 5:14:20 am

Thanks David! I don't have Quicktime pro, just the regular Quicktime 10. But I do have Soundtrack Pro and Compressor.

I'm not worried about rendering or any sync issues. I was just worried that the song might be slightly slowed down because I noticed the length was slightly different. Is that just FCP displaying it improperly?

It only changed the length when I dropped in the song on the timeline after already having dropped in footage. That's why I thought the 23.98 frame rate was the reason why the length of song was slightly shorter than how it's listed in the browser.

When I double click a song from the browser and load it into the viewer, it takes 30 frames for it to count to one second. But when it's in a 23.98 sequence and I open it from the timeline, it takes 24 frames for it to count to one second. So I was thinking maybe the length of the song hasn't changed and that it's just being displayed incorrectly.

The only reason why I'd convert it to 48 KHz would be so that the speed of the song won't change. But does converting 44.1 Khz audio to 48 change the speed anyway? If so, then I'll just leave it at 44.1

Update: I just exported the song as 48 KHz in Soundtrack Pro and when I added it to my sequence and right clicked it on the timeline, it showed the length being 10 "frames" shorter than in the browser. So I'm pretty sure the length of the audio has nothing at all to do with the the song being 44.1 KHz in a 48 KHz timeline. I think it must have to do with the frame rate.

So either putting the song on a 23.98 sequence changes the speed of the song (which I just can't believe) or FCP is just displaying the length incorrectly on the timeline.


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Dave LaRonde
Re: 44.1 KHz audio in 48 KHz timeline
on Sep 15, 2015 at 5:41:34 pm

Sometimes wav files can have frame rates associated with them in the metadata. Not all the time. Sometimes. It all depends on the file's provenance.

But to eliminate the possibility, just open it soundtrack pro, export a 48khz aiff file, use it in FCP and edit merrily away.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Bobby Hall
Re: 44.1 KHz audio in 48 KHz timeline
on Sep 15, 2015 at 6:23:14 pm
Last Edited By Bobby Hall on Sep 15, 2015 at 6:30:56 pm

Thanks Dave. I saved a copy as AIFF 48 KHz in Soundtrack Pro and when I put it on the timeline, and right clicked it to see how long it was, it was still several frames shorter than the length listed in the browser. So either the time is incorrectly displayed on the timeline or incorrectly displayed in the browser. I just wanted to be certain that the speed wasn't changed in any way. I'm not really sure what's going on right now though.

Edit: I just noticed when I looked at how long the song was under the duration tab in the browser, I right-clicked it and it had "drop frame" checked. When I changed it to "Non-Drop-Frame" it said the length of the song was 03:05:28. Before it said 3:06;04. Could this have anything to do with it? The song on the timeline still doesn't match either of these two times though.


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Dave LaRonde
Re: 44.1 KHz audio in 48 KHz timeline
on Sep 16, 2015 at 5:18:33 pm
Last Edited By Dave LaRonde on Sep 16, 2015 at 5:21:18 pm

I'm thinkin' you might have a frame rate mismatch someplace. Double-check the video and the timeline to make sure it's all at 23.976, or as FCP incorrectly calls it, 23.98.

Might you also have been mislead by trying out the original 44.1 file in FCP, noted its duration, but experienced a frequency sampling error?

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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