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Understanding sample rate / sample rate conversion?
Okay. So I think this will be my last question about audio sample rates.
I have a lot of captured files that are 32 kHz because they were shot that way. My sequence is going to be 48 khZ because I do have many 48 khZ files also.
Now, I heard the best thing to do would be to convert all my 32 kHZ files to 48 kHz. Yes, Final Cut does it for you if you don’t, but I read somewhere on the internet that it doesn’t do the best job, so I’m planning on doing that using Soundtrack Pro.
My question is, in converting the 32 khZ files to 48 khZ, will it be off sync with the video at all (even minutely)? I’ll admit I don’t totally understand sample rates, and what a program is doing when it converts them. Is the audio positioning relative to the video CHANGED at all when you convert it to another sampling rate?
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10 Replies
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[zeke meginsky] “My question is, in converting the 32 khZ files to 48 khZ, will it be off sync with the video at all?”
No sync problems.[zeke meginsky] “but I read somewhere on the internet that it doesn’t do the best job, “
In what is based that statement?
I’f I’d believe everything I read in Internet, probably I wouldn’t be using FC.
Don’t waist your time.
rafael -
Okay. So hopefully I’ll do it with Soundtrack Pro and it will be the same..
Yes, they said Final Cut Pro does not do the best job. But if I did use FCP to do it, is it done automatically? I was reading something about an “item level render”, would that just change it to 48 khZ permanently?
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FCP usually does fine with an “item level” render. Its when you let it try to do it on-the-fly without render, where problems sometimes arise.
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Hmm. Okay. I wonder why someone wrote that Final Cut Pro does a bad job (or lower quality). And why this article was written:
https://www.rippletraining.com/resampling_audio_in_soundtrack_pro_new_.html
..if Final Cut Pro can just do it..
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[zeke meginsky] “Hmm. Okay. I wonder why someone wrote that Final Cut Pro does a bad job (or lower quality). And why this article was written:
https://www.rippletraining.com/resampling_audio_in_soundtrack_pro_new_.html
“
He mention nothing on quality.
Hi say that if the sample rates doesn’t match you won’t be able to mix in RT few audio channels.
FC can’t re-sample, render and mix on the fly many channels.
He talk about “CPU overhead”
Nothing on quality.
You are up-sampling 32Khz to 48 Khz. That’s not any kind of “critical” process and any way FC can handle it at 32bFP precision.There is an easier workflow: Set your sequence to 32Khz (you will have full RT).
Before export, change the sequence back to 48 KHX.
rafael -
Well if I converted the sequence to 32 khZ, I could play the 32 khZ clips easily but not the 48 kHz ones, right? So I don’t think that would make things any easier by itself.
Thanks a lot for all your help, that cleared it up for me . So Final Cut Pro should handle it and I don’t even have to convert them if I don’t want to. If that’s true and it’s not going to cause me any problems down the line, then that’s the best answer I could ask for. Or I wanted to convert them i could use Soundtrack Pro or Final Cut Pro’s item level render.
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FCP is not a professional audio editing and mixing system. It is fine to offline sound and it has been said here many times that mixed sample rates or using data compressed formats like mp3 make it click and pop plus sync drift and other RT playback issues are a problem unless all audio is PCM 16 or 24 bit 48khz.
If you want to make you edit process simple without all the common problems I have just mentioned, then convert all you clips with 32 khz sample rate to new quicktimes (same video codec) but change the audio to 48khz. Compressor is a good tool for this.
Do that first before editing and you will find that FCP behaves with audio for your edit. Finishing audio, you should then be exporting to an audio system that has the sub frame accuracy, bus based architecture with decent EQ and effects processing to do a proper job. STP is in my opinion an entry level app to do this and can round trip from FCP.Otherwise export an OMF and pay a pro with the right gear and expertise. It is by far the cheapest way to value add to any production.
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Hmm. What you described kind of sounds much more complicated. I don’t know how to use Compressor to easily convert the files to 48 khZ. And then you’re saying use Soundtrack Pro? To do what? I don’t understand why you’re saying both..
My solution was just going to be using Soundtrack Pro instead of Final Cut to change each clip in the sequence. Is there reason why I shouldn’t do just that?
I’m having trouble understanding..thanks..
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So isn’t it just easier to use Soundtrack Pro to convert each clip to 48 khZ? Why would I use Compressor instead?
If I use Compressor, what is the process I have to do so that literally nothing bad or different happens to the video? I’ve only used Compressor to put files on DVD.. I don’t know how to use it otherwise.
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Buy this program and don’t worry about using compressor or STP.
https://www.digital-heaven.co.uk/loader
Dajen Productions, Santa Barbara, CA
MacPro Two 2.8GHz Quad Core – AJA Kona LHe
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