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known issues about (long) tracks alignment?

Hi everybody.

I just got this problem:

- I import an audio track on which I want to play (from the file selector.) e.g., a drum track.
- I arm a new track for recording, connect my guitar to my soundboard, press rec+play and start recording. No delay, no latency, no strange things in my ears.
- I export my tracks (from the Master output)

I close Qtractor.
When I load my bounce to Audacity, I notice that what I just recorded is not correctly aligned (guitar starts too early)

So I open Qtractor again and now if play all, the tracks are actually non aligned. So I align them and do the bounce again.
Same problem.

I noticed that the track I imported is a mp3 file at 44.1 K frequency, while JAck and Qtractor were set to 96 K. So i thought: "this is the problem".
I set my system (Jack and Qtractor) to 44.1K, started a new session, so everything was now set to 44.1
I recorded again the guitar, I made the bounce and.. same problem. Guitar and drum are not aligned anymore.
But, closing and opening Qtractor again, the guitar seems to start properly now, and after a while, what I recorded (or, how Qtractor was now playing) went out of timing again.

What can I try? Are there some known issues of this kind?
Could it depend on the sound board?
I'm quite sure when I was still using my old (now dead) sound board, this wasn't happening.

Thank you all

rncbc's picture

hi Manu,

my first suspicion will go the mp3 backing track you have in there; please try to convert every pcm audio file to a non-lossy and sample-accurate format (eg. .wav, .flac, etc.) and most important that that, on the same exact nominal sample-rate that you normally run your sound-card device (eg. 96k); i believe you can use Audacity for just that.

also, as a rule, it would be a lot better and always preferable to have any re-sampling out of the equation when exporting to audio; so that you shall have ALL audio pcm files encoded in the very same and precise sample-rate--again, that would be the nominal sample-rate JACK (and the DAC) is running--without any chance to drift apart each other when rolling out an audio export operation.

please let me know if there's any improvement in that regard.

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