Two different sample rates

Report · Nov 11, 2017

Dear everyone,

I have been recording a podcast on two different computers, but unfortunately we were insanely stupid, and one of us have recorded in 44100 and the other in 48000. This means that when we sync up our audio files in a 44100-project, the 48000 file is a tad longer. Even if I re-encode it to 44100 - the file length stays the same. It starts out by being in sync, but sort of slips out of sync over the progression of the file. The files are about 1.5 hours.

Is there any way to correct this. I've tried speeding up the 48000-file to the same length as the other file, but the problem persists. It still seems to loose sync gradually. I've even tried to record the complete file in to a 41000 file, but since the file is still longer, this doesn't solve the problem.

It's for a podcast, and will in the end be exported in to an mp3, so any solution that effects the quality is also welcome.

Does anyone have any solution for this problem?

Best regards
Jannik Dahl

Report · Nov 11, 2017

jannikp11970011 wrote
Even if I re-encode it to 44100 - the file length stays the same. It starts out by being in sync, but sort of slips out of sync over the progression of the file. The files are about 1.5 hours.

Well, they would, I'm afraid. This is simply because the sample clocks on the two systems weren't locked, and over a longish period (sometimes even over a short one with cheap kit) they will drift apart. If you took a quarter percent difference in clock rates, that would represent a drift of 9 seconds an hour, and that's well within the tolerance of a lot of systems, I'm afraid.

Your only fix is to decide which session's going to be the 'master', look at the length of it and stretch or shrink the other one to be exactly the same length on the same system. It should stay reasonably in time then, and still sound okay because it won't be very much of a stretch/shrink at all. Just make sure that they're the same sample rate before you do it. The easiest way to end up with the file you want is to use Export>File and click on the sample type 'change' box, change the settings there, and then make sure you've saved it with a different name. Then do the time-stretch/shrink.

Report · Nov 12, 2017

Thank you so much for answering my question. Even though the answer was what I feared. 🙂

Do you know any way to automatically sync the two audiofiles, despite of the different lengths. Its really hard to be as precise as necessarry. And Ive tried twice that after shortening the longest Clip, it is still out of sync in the middle. And then goes back intro sync.

is There any software or plugin that can analyse the files, and force them to sync?

best regards!

Report · Nov 12, 2017

jannikp11970011 wrote
Do you know any way to automatically sync the two audiofiles, despite of the different lengths. Its really hard to be as precise as necessarry. And Ive tried twice that after shortening the longest Clip, it is still out of sync in the middle. And then goes back intro sync.
is There any software or plugin that can analyse the files, and force them to sync?

This is, of course, one of the effects of drifting - it's not a constant effect, and because there is no absolute reference on either track, nothing can be done about it - well not in sync terms, at any rate.

The only suggestion I can make (and it might even work...) is to put both files into a multitrack session, select both of them, and with the mouse over the waveform, select 'Automatic Speech Alignment', and follow the on-scree cues. Couple of points: you may need to break the file down into manageable sections to do this, and you may also need to experiment with the 'alignment' settings. But in principle, this should eliminate both of the drifting effects - time and variability.

If this works, incidentally, can you let us know please?

Report · Nov 12, 2017

If that doesn't work you may have to break up one of the clips into shorter sections and stretch each one individually to sync. It may help if you put markers into each version of the audio at the same places. You then have a visual guide to help with the synchronisation.