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Does audio time code frame rate effect playback in FCPX

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james Lackleter
Does audio time code frame rate effect playback in FCPX
on Feb 16, 2014 at 10:47:07 pm

Does audio time code frame rate effect playback in FCPX. I've seen too many threads stating counter opinions. Would like to just set the record with this one. Thanks.


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Oliver Peters
Re: Does audio time code frame rate effect playback in FCPX
on Feb 16, 2014 at 10:56:43 pm

[james Lackleter] "Does audio time code frame rate effect playback in FCPX"

What do you mean? Playback speed of the audio source file or of the project timeline? My gut feeling is no, but I also see TC that is suspect in terms of the correct numbers when I compare FCP 7, Premiere, FCP X and Media Composer. I trust 7 and MC as far as audio TC are concerned, though some of this might be dependent on the actual audio recorder.

- Oliver

Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com


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james Lackleter
Re: Does audio time code frame rate effect playback in FCPX
on Feb 16, 2014 at 11:08:42 pm
Last Edited By james Lackleter on Feb 16, 2014 at 11:09:00 pm

Hey Oliver, I mean in the project timeline. I here yes and no. From my tests it does not, but I may be wrong. It should not effect the source file correct?

I ask this to clear confusion, and I have a clip that syncs in Avid without resampling, and the same one in FCPX does not sync and requires resampling. I'm trying to finish the project in FCPX as it's almost done and I'd like to avoid recutting.

Thanks


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Oliver Peters
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 12:11:49 am

[james Lackleter] " It should not effect the source file correct? "

I wouldn't think so either.

- Oliver

Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com


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Paul Figgiani
Re: Does audio time code frame rate effect playback in FCPX
on Feb 16, 2014 at 11:45:41 pm

Hey James.

Not trying to be snarky - but have you had a change of heart? I thought you hated everything about FCPX??

"To Editors Thinking Of Switching to FCPX 10.1"

-paul.


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james Lackleter
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 12:51:13 am
Last Edited By james Lackleter on Feb 17, 2014 at 12:58:29 am

No I'm not a fan. There's too many problems, but I do however have a nearly finished project in it that I'd like to finish in it. But yes I have a slew of posts with glitches I've come across, and the fact that XML transfer to Logic is useless is a biggie. But I've tried to leave behind as many solutions to problems that may be encountered to ease use for people forced by budget or w/e to use it.

Anyway I would like to solve this timecode issue, so please any info is appreciated. I'm researching books now because internet forums are so flip flop on the issue to a question that should be simple. I called FCPX support and they didn't seem to grasp the question as usual.

I'm going to post on the Avid forum to see why it's working in there, I'm assuming it's doing something on import.



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Walter Soyka
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 1:22:19 am

[james Lackleter] "Anyway I would like to solve this timecode issue, so please any info is appreciated. I'm researching books now because internet forums are so flip flop on the issue to a question that should be simple."

Frame rates for audio is like DPI for video.

From a quick read of your other thread, it sounds like you changed the duration of your video by conforming it from 24.0 to 23.976, and now you want to change the duration of your dual-system audio to match -- but you don't want to resample it? You can't do that, because math gets in the way.

Duration = Number of samples / Sampling rate

For your video, you changed the duration by changing the sampling rate (keeping the same number of frames, but interpreting them as 23.976 fps instead of 24.0 fps).

For your audio, to change the duration, you must change the number of samples, the sampling rate, or both. However, you cannot practically change the sampling rate, so you must change the number of samples.

Resampling is unavoidable in this case.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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james Lackleter
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 1:33:13 am

Thanks Walter, yes I've resampled it, and because it's so minuscule I don't mind doing it. How about the timecode then. It should not effect playback speed in anyway correct.

Basically I can enter any time code frame rate I wish for audio, even if it's wrong, let's say 23.98 fps video with 30 ND audio timecode framerate, and it will make no difference in Avid or Final Cut in terms or playback and syncing correct?

The only thing it'll effect is the actual timecode numbers, but not playback. Correct?


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Walter Soyka
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 1:52:06 am

[james Lackleter] "Basically I can enter any time code frame rate I wish for audio, even if it's wrong, let's say 23.98 fps video with 30 ND audio timecode framerate, and it will make no difference in Avid or Final Cut in terms or playback and syncing correct? The only thing it'll effect is the actual timecode numbers, but not playback. Correct?"

You said you did a test, right? It read like you didn't believe your own results, so I wanted to provide a little justification for what you're already seeing.

I'm not in front of any NLE at the moment, but my point was that the only way it could possibly affect playback is if it were actually re-sampling the audio for you. You cannot keep the same audio samples and the same audio sampling rate but get a different duration.

Mucking with the TC may have ramifications for interchange with other applications.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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james Lackleter
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 2:49:27 am

okay well that's great, thanks for clarifying. So then Audio Timecode Frame Rate does not effect clip length or playback in Final Cut Pro X or Avid. I did a test importing different TC rates in Avid and all they all synced the same.

I hope people take note of this thread when researching the topic, because there's too many stating that playback is altered which is clearly false. The only way playback would altered is if you're smart slating or jam syncing because the TC will be off.

I'm wondering why the audio is syncing in Avid without resampling. Same deal, importing 24.00 FPS footage into a 23.98 timeline. Audio is syncing perfectly without resampling, even though I'm pulling down the frame rate. Any thoughts on why?


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Jeremy Garchow
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 4:39:32 am

How long is the clip you are syncing?


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james Lackleter
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 4:43:16 am

It's a little over 5 minutes


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Jeremy Garchow
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 4:53:41 am

That should be enough to show any drift.

You are saying these same clips won't sync in X without a resample?

Or are you asking why it syncs in Avid after the 23.976 import?

It's possible a video clip at 24.0 frame rate and an audio clip with 23.9 tc rate can sync if the recordings are unadulterated. The tc of course, won't match after a minute or so.


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james Lackleter
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 5:01:29 am

Im trying to figure out why it's syncing in Avid but requires resampling in FCPX. It's the exact same settings so it's a little baffling to me.


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Jeremy Garchow
Re: Does audio time code frame rate effect playback in FCPX
on Feb 17, 2014 at 1:33:04 pm

Can you tell us about your media exactly?

I'd like to test it.


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Jeremy Garchow
Re: Does audio time code frame rate effect playback in FCPX
on Feb 18, 2014 at 3:59:03 am

Ironically, I was dealing with standards conversion today (23.976 to 25 for broadcast).

Curious to see what FCPX would do with this media, importing the 24p file to a 25 Project cause a noticeable shift in both time and pitch.

I imported the time coded audio separately, and played it against the obviously speed and pitched changed video with embedded audio. The files did not sync.

The audio remained in time and pitch, while the video didn't. So the audio tc doesn't seem to effect playback in FCPX, but video definitely does, and it seems rather buggy.

So, if your video is 24.0 and your audio is 23.98 and you are in a 23.98 timeline, FCPX might be changing the speed of the video without really reporting it. Resetting speed doesn't do anything, hitting "automatic speed" screws it up a bit more (it goes the wrong way). Changing the speed to something like 96% (FCPX reports 96% but I know it's really ((24000/1001)/25) which is just short of 96%. Turning off the "preserve pitch" checkbox actually pitched the audio back to normal.

I didn't create the 24.0 vs 23.9 media that you have, but perhaps you are having similar issues, or a different combination/permutation therein.

But to answer your question, the time coded audio was not changed, only embedded audio.

Jeremy


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Walter Soyka
Re: Does audio time code frame rate effect playback in FCPX
on Feb 18, 2014 at 4:03:29 am

[james Lackleter] "I'm wondering why the audio is syncing in Avid without resampling. Same deal, importing 24.00 FPS footage into a 23.98 timeline. Audio is syncing perfectly without resampling, even though I'm pulling down the frame rate. Any thoughts on why?"

What is your exact Avid workflow here, step-by-step?

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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james Lackleter
Re: Does audio time code frame rate effect playback in FCPX
on Feb 18, 2014 at 5:20:30 am

I think FCPX has jumbled information and automatic pulldown/up is messing up the sync. FCPX seems to have problems with WAVE files in general, I did convert to AIFF which solved nothing.


Let me make a new test with Avid without using the proxies I made in FCPX with the Redcode, because I suspect FCPX pulled the footage and is not reporting it.

I will use RedCine, export the 24 fps clip and 23.98 and load it into 23.98 Avid Project with unaltered BWAVE and see what happens.


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Andreas Kiel
Re: Does audio time code frame rate effect playback in FCPX
on Mar 17, 2014 at 9:50:20 am

I'm a bit late here.

But here some notes which makes things hopefully clearer.

Resampling and changing playback speed are two totally different things.
Samplerate for audio is the same as fps for video (not dpi for video) so let's call it sps.

You can record audio at any sampling rate. But let's take 48 kHz and 32 kHz here.

Record 60 seconds. Once recorded both files as stand alone files will play 60 seconds.

But forced to play back in a NLE timeline with a fixed sps of 48 the first file will playback correctly. The second one will play at 2/3 of the time (32/48). The other way round the 48 sps file will play longer in a 32 sps timeline.

Now for those poor guys who have to work with NTSC:
A real world second is not a second in NTSC video world. Its 1001/1000 seconds.
So selecting a 48k sps audio preset in a timeline preset means that a real world audio of 60 seconds is only 1000/1001x60. That means that those 60 seconds are only 59.94 seconds long. Its too short.

One way - if you stay strictly in NTSC - is to record audio with 48048 Hz. This way a real world 1 second audio will match a 1 second NTSC video.
Next option with BWAVE files is to change the playback settings in the BEXT header of the file. This won't resample the file!!!

Now about the TC. BWAVE doesn't have a TC in a way you're used when handling video. It has a timestamp in the header. This timestamp contains the Samples after Midnight. Based on that the NLE will convert this to TC which can be displayed. So in NTSC world this might give a wrong interpretation.
For example if you have a "Start TC" of 00:10:00:00 (thats what you see on your audio recorder) it means that using 48kHz the timestamp is at 600x48,000 = 28,800,000 samples. Since the real sampling rate in the timeline though is 48048 Hz you have to divide the source stamp by this number. This results in 9.99000999000999 minutes. So for a 23.976 fps project this is a TC of 00:09:59:10.

So setting the Bext header and/or iXML chunk to the correct playback speed will keep everything intact. Again this is without resampling!
Using an AIFF there aren't these options.

So you can edit all the stuff without resampling when using BWAVE. But resampling will happen when you export a final movie.

I wrote a bit 8 years ago when FCP started to read BWAVE metadata. Many of the things are outdated but the article explains a bit what happens with BWAVE.

-Andreas

Spherico
http://www.spherico.com/filmtools
X-Files Pro, tools for working with FCPX
http://www.spherico.com/filmtools/X-Files/index.html

"He who fights with monsters should be careful lest he thereby
become a monster. And if thou gaze long into an abyss, the abyss will
also gaze into thee." - Friedrich Nietzsche, Beyond Good and Evil


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