Sound "compression" when recording

[matts2cant]

Hi,

I'm using an external audio controler (Behringer UCA200) to record my guitar. I noticed that, when playing over backing tracks, the track was recorded a bit faster than i played it: In rythme at the beginning of the song, but 2 or 3 seconds late at the end.

I made a test, generating a Click-track and playing over it in rythm :

- At the beginning, no problème :


- At the end, almost 1/2 second late :


Does the problem comes from the audio controller or is it Audacity ? Is there a way to fix it ?

PS: I tested all the sample rate configurations : 48000kHz, 44100kHz, it doesn't solve the problem.

[kozikowski]

I's not unusual for cheap sound cards to do this. There's no effort to synchronize the timer signals between the capture and the play back. They're designed to play YouTube and perform VOIP phone calls. No sync needed.

This device uses ASIO drivers and Audacity only has very shaky support for that, if at all.

You can get this when the computer isn't up to the speed needed for the work. Real Time capture and playback are stressy for a computer. It's not like bookkeeping where the computer has time to comb its hair and brush its teeth between spreadsheets.

There are other postings of people having all sorts of production problems what vanished on a different, we assume slightly faster machine.

Koz

[steve]

I've come across this issue with on-board sound cards, and as Koz explained it is generally caused by the clock signal in the sound card for playback running at a slightly different speed to when it is recording. However I have not come across this before with these Behringer devices, and certainly the one that I use does not do it.

There are a couple of possibilities that come to mind. One is that you have a UCA 202 that is a bit "off" (not working as well as it should) - if this is the case there is not much you can do about it other than ask the shop where you bought it to replace it.
The other option is that there is a data bottleneck in the computer that is preventing the UCA to run at the correct speed. If this is the case I would expect there to be crackling, or small gaps in the recording. Try recording some music that has continuous sound, or perhaps some test tones and check that the sound is not breaking up when you have a few tracks going.