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  #1  
Old 01-20-2022, 01:53 PM
Jazzvibe Jazzvibe is offline
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Default Upsample Audio Duration

I have a PT session with three audio tracks (separate sources) of a live video performance.

Two audio sources are 48Hz 24bit which matches the PT session. A third audio source is 44.1 hz 16 bit. It had to be converted/upsampled to import into the session. All of the audio sources have different problems so I'm trying to work on the sources separatly (separate tracks) to then blend a final output.

However the third audio source that was upsampled does not seem to line up with the other audio. Does upsampling change the duration of the audio in any way or why would this happen?
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  #2  
Old 01-20-2022, 02:58 PM
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JFreak JFreak is offline
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Default Re: Upsample Audio Duration

Hi, welcome to the community.

Your post count is so low your posts may go to manual approval for some time. Do not repost should that happen. It will ease over time.
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  #3  
Old 01-20-2022, 03:17 PM
BScout BScout is offline
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Default Re: Upsample Audio Duration

Quote:
Originally Posted by Jazzvibe View Post
Does upsampling change the duration of the audio in any way
No. Resampling (sample rate conversion) of 44.1 > 48k will not change length.
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  #4  
Old 01-20-2022, 05:52 PM
Darryl Ramm Darryl Ramm is online now
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Default Re: Upsample Audio Duration

And the most likely reason things don't line up is you are misunderstanding what sample rates content is actually at or accidentally applying an incorrect correction. Pro Tools does not get this wrong. But you can use Pro Tools to measure say apparent drift, is that ratio 48/44.1? Lots of cases in the past where folks here have misunderstood what sample rate things are running at, including when applying external clocking that causes the interface to change sample rate. Some interfaces make it really easy to get confused.
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Old 01-20-2022, 08:30 PM
Jazzvibe Jazzvibe is offline
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Default Re: Upsample Audio Duration

Now I am confused. I just looked at the PT import window again. This time I noticed that when I choose the file to import a message comes up just above the "clips to import" box that says the file "can be added to the current session but it will playback at the wrong speed".

If it's not the sample rate, is it the bit rate change (16 bit to 24 bit) causing the problem?

Is there a way to make this work?

P.S. JFreak sorry for the repost but when I posted the first time a screen flashed by so fast I barely saw it and then nothing happened. I reposted and the same screen blasted by, again so fast I couldn't read it. I'm guessing that window may have some useful information about posting but it doesn't stay visible long enough to know what it says.
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  #6  
Old 01-20-2022, 11:48 PM
Darryl Ramm Darryl Ramm is online now
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Default Re: Upsample Audio Duration

No bit depth here is irrelevant.

Pro Tools is saying that it thinks that file is the wrong sample rate. And Pro Tools may well be wrong about that if the file has the wrong sample rate in it's header. You normally see this if you don't select SRC and the file is marked with a sample rate different than the session. I'm not following exactly what you are doing here when you see the dialog.

The way to make this work is for you to work out what you are doing wrong. Nobody here can really offer you any advice because you have not described anything you are doing in detail.

And again these sorts of problems are almost certainly caused by user mistakes, source files that are not the sample rate you think, including potentially source files with the wrong sample rate in their headers, etc. if you apply SRC to a file and it comes out the wrong duration vs. other files where you can line things up then you simply got something wrong. If you are importing to the clip list you won't be the first person to then pick the wrong clip and place it on a track. Have you tried this import before... make sure you are picking the .1, .2, .whatever file that is the correct one. Pro Tools just will not get converting sample rates wrong. If it did people would be screaming about it here (recent version(s?) seem to have issues with MP3 input at times causing clicks and pops but that is not relevant here).

At a minimum: Go back to the source material and play it outside of Pro Tools and confirm the sample rate. Create a new empty session and do nothing else in it except import the three files and import them directly to tracks. Try applying the SRC you think is correct, if that is not correct try applying none. And in any case where things don't line up use Pro Tools to measure precisely what that time change ratio is... is that 48/44.1? or some similar likely ratio?

If after doing that you are still stuck tell us what you see when you do all the above things.

And provide the usual type of expected info including:
What computer/OS version?
What exact version of Pro Tools?
What format audio file are you importing? Mono? Stereo?
What sample rates do you think these files are at? Why do you think that?
Where did the files come from? e.g. were they exported from a video? How?
What sample rate is the session at?

Last edited by Darryl Ramm; 01-21-2022 at 12:00 AM.
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Old 01-21-2022, 10:33 AM
Jazzvibe Jazzvibe is offline
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Default Re: Upsample Audio Duration

Daryl thanks for your reply here are more details if it helps.

As stated in my original post I’m working with, two 48 khz 24bit and one 44.1 khz 16 bit files. I confirmed this from the beginning by viewing the Mac OS file info window (I’m always careful to check sample and bit rates of files I work with).

What I failed to mention is that the PT session is 48khz 24 bit. It’s a fresh session for this project and has only three stereo tracks plus a master bus.

I imported the stereo files using the command-shift-I import window to add them to the session clip list. The 44.1 khz 16 bit file needed to be converted or upsampled for the session. SRC was checked and the tweak head slowest option was used.

All three files are stereo .wav
The only difference is the sample and bit rate of the one file
The 48 khz 24 bit files were exported from FinalCut Pro as audio only
One video/audio source is a Pro video camera the other is a zoom camera
The 44.1 khz 16 bit file is from a zoom audio recorder

I’m running ProTools 2021.12.0
Mac OS Catalina on a 16” 2019 MacBook Pro 8 core i9 2.4 ghz 64 gigs ram
Focusrite Clarett 4 Pre interface

After converting and importing the 44.1 khz 16 bit file I noticed that is was not lining up with the 48 khz 24 bit files of the same audio.

It seems I’ve answered my own question now that I see the message in PT saying the 44.1 khz 16 bit file can be converted and imported but that it won’t playback at the correct speed.

So apparently upsampling does change the duration of the audio.

Given that, my question is if there’s a way to work with these three audio sources (of the same live performance) together?
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  #8  
Old 01-21-2022, 11:34 AM
daeron80 daeron80 is offline
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Default Re: Upsample Audio Duration

If the 44.1 file is the right pitch but the wrong speed, that could be a real pain. It's possible to use some sort of TC (Avid TC/E, Elastic Audio, Melodyne, Serato, etc) to time compress/expand by eye/ear. But it will never really be right, and will have artifacts. The last time that happened to me, I sent the file back to the keyboard player with instructions on how to get his sound card's sample rate and clocking set right and made him re-export his parts. But that wouldn't be possible for a live performance. If TC didn't prove workable with a couple of tries, the best plan would be to live without that track.
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  #9  
Old 01-21-2022, 01:22 PM
Jazzvibe Jazzvibe is offline
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Default Re: Upsample Audio Duration

dearon80 , yes the 44.1k 16 bit audio is the correct pitch in the 48k 24 bit session but is the wrong length or speed just as the ProTools import window indicates.

I've worked with time stretching before and as you say it's never really right. The audio problems here are already difficult so that unfortunately would just add to the problems.

I was hoping for a way to upsample that one audio source that does not change its duration but so far that seems not to be possible.

The only other thing I can think of is to bounce the 48k 24 bit files down to 44.1k 16 bit and see if things line up in a 44.1k 16 bit PT session. I wonder if down sampling changes the duration. If that worked I'd then have to figure out how to deal with getting the audio into and out of FinalCut.
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  #10  
Old 01-21-2022, 02:49 PM
daeron80 daeron80 is offline
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Default Re: Upsample Audio Duration

Unfortunately, the problem is likely that the device that recorded the 44.1 file was incorrectly clocked. I think the only hope would be to play it back from that device via its analog outputs and record that into a device that is correctly clocked. That may solve most of it.

There will still be some degree of problem, though, because that any time you record to more than one device at the same time, there will be drift unless the devices were properly synced with timecode, word clock, or both. That's the case whether the devices are analog, digital, or some combination. So expect to still have to do a bit of manual time manipulation, even if you succeed in recapturing the audio from the original device.
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