Nayeli Garci-crespo
Forum Replies Created
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Thanks, and it is true!
-Nayeli
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I’m actually now more confused than ever!
I did a conform to the 23.98 video and it’s the same, so it should be 23.98. What also confirms this is that I imported the 29.97 video and the original 24fps/48kHz audio into a regular DV NTSC 29.97 project with 29.97 sequence preset, and it behaves exactly the same as with the 23.98 video. The WAV files that come direct from the Sound Devices 744T have pulldown applied to them by Final Cut (green bar), so they are .1% slower than the video, but that same file converted to AIFF with no pullup or pulldown fits the video perfectly since Final Cut does not apply pulldown (no green bar across sound clip). So it’s definitely not Cinema Tools. Could it be the transfer from HDCAM to DVCAM at the lab? I just can’t think why audio with no pulldown will fit the 23.98 video!
A third test I did was to reverse the 29.97 DVCAM transfer to 24fps, and import the audio witha 24fps preset. In that case, I was really surprised to find that Final Cut did not apply pulldown to the original WAV file (as expected) but DID to all the AIF files I imported (or pullup)! The WAV audio in this case was 1% too long (which makes sense in relation to the other tests). The file that worked was the original file converted to AIF, because Final Cut applied a pullup to it (green bar across clip, and I can tell it’s a pullup instead of a pulldown because it runs faster).
*sigh*
-Nayeli
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“I suggest you try a usenet newsgroup called rec.arts.movies.production.sound. ”
Thanks Ty, I’ll check that out!
-Nayeli
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“23.976 (or 23.98) is the real frame rate that an HD camera is recording when it says 24fps. As I understand it, if you are working with an HD camera shooting at 24fps, you want to be recording at 23.98…the REAL frame rate of the camera. 24fps is ONLY used when you are shooting film and finishing on film (for projection). In other words, not for HD transfer for television.”
Thanks for responding!
I have actually worked on film productions where we do a reverse TK to 23.98 instead of 24 because the post house prefers it that way. In those cases they recorded sound at 24fps/48kHz and relied on Final Cut Pro to do an automatic pulldown so that the audio would match the video running at 23.98. One time it for some reason was only working for second unit sound so we had to do a sample rate conversion in ProTools to the recorded audio.
In any case, my real question I think is, if you record with a 23.976 frame rate, but your sample rate is set to 48kHz, do you get audio that matches video running at 23.98? And if so, how is it different or the same as recording audio with 24fps frame rate but 48048Hz sample rate? It seems to me that in order to have audio that matches video at 23.98 you necessarily have to alter the sample rate, since by definition 48kHz has a reference to real time: 48000 samples per second. Does this make sense?
-Nayeli
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Gary: “As long as there is no video associated to the audio clip on import to the timeline the time of the clip remains unchanged.”
But isn’t that, in Final Cut Pro, determined by the sequence preset, so that in a way, you can’t really have audio that’s unassociated to video? For example, I opened a project that’s set to 23.98, and I imported sound at 48K. When I put that sound in a 23.98 timeline with no video in it, Final Cut slows it down .1%. It will have a green bar across the clip to indicate it….
-Nayeli
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Oliver: “As a test, take one long clip that has been reverse TK’ed and use the Cinema Tools CONFORM function to make this clip have a timebase of 23.98. If it’s indeed 24, then this will change the QT file to be read as 23.98.”
Aaah! Thank you!
I’m about to try putting the audio against the original 29.97 clip and one that has been reverse TKed to 24 instead of 23.98 to see what happens. Had not even considered the conform function!
-Nayeli
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Oliver: “My point was that he said the audio TC was 24fps. My thinking is that this is now the incorrect speed. It should have been 29.97 or 23.98 to match the “video rate” of the camera, not a true 30 or 24, which is what was implied.
In any case, I’m currently cutting a feature in FCP shot with an EX1 and EX3 plus double-system audio as a back-up. The video is all 23.98, but the audio TC is 48K/29.97 and sync is just fine. So 29.97 should be OK in FCP-land as well. ”
Yes, audio TC is 24fps and it’s 48K. What I’m perplexed about is that it is perfectly in sync, without adding pulldown, with my 23.98 video, making me suspect that somehow my video is not running at the right speed.
I have a question about timecode, though. What happens when you have 29.97 or 23.98 timecode when you’re at 48K? Because as far as I know, TC is only base 30 or base 24. If you record at 48K but choose 29.97 timecode, is that like recording at 48048 and stamping it as 48K?
-Nayeli
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Sean: “My guess is that Final Cut is the problem, not CT. When you import any A/V quicktime into Final Cut, the current Easy Setup dictates what sample rate the audio is interpreted as.”
Yes, I’ve run into this before. The sequence preset was and is set to 23.98, we were very careful about that. All audio imported has been under 23.98, which is why Final Cut applies automatic pulldown to the audio, which is recorded straight 48K with 24fps timecode. In this case, we WANTED Final Cut to apply the pulldown (though I do wish it gave you a choice, aside from what your sequence preset is), and it did. The strange thing is that the audio with pulldown is now running 1% slower than the video which is *supposedly* at 23.98. Audio without pulldown runs at precisely the right speed. Which makes me suspect that somehow the video is actually running at 24fps. But I can’t get my head around why that is….
-Nayeli
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“When CT does a reverse TK, split fields are removed and the timebase is changed. So 60 fields/30frames becomes 48 fields/24frames, but 1 second still equals 1 second of duration.”
But that would depend if you reverse to 23.98 or to 24, right?
-Nayeli
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OK, I tried it successfully, but did notice one detail: doing that only changes how the timecode is displayed in the browser (still useful), but not the timecode assignation of the audio itself. To change that you have to use Modify > Timecode.
-Nayeli