Clap Your Hands Say WTF

March 6, 2006 7:08 AM

Multi-track recording synchronization issues with Audacity.

I'm trying to record some acoustic demos in my room. I've previously made similar home recordings with Sonar and have had no problems. However, I don't have Sonar on my laptop, so I've been using Audacity (1.3b). I record with a condenser mic into a Presonus TubePre, then into my external Soundblaster Live USB, then into my laptop.

The problem is that nothing I record will be synchronized. If I generate a beat track in Audacity and then record a track of myself clapping along with each click, when I play the track back it begins synchronized and then slowly drifts more and more out of time, as if the length of the clip I just recorded is somehow altered slightly after I record it. The only way around this that I've found is to record only very short clips and then make small adjustments by hand when I need to, but this is obviously far from ideal.

Does anyone know why this is happening? Is it a software or hardware issue? I'm not monitoring what I'm recording and I don't need to, I just want the track to play back at the same tempo I recorded it.

posted by ludwig_van to technology (8 comments total)

Do you see the claps and the beats drifting on Audacity's track display? Have you tried going back to 1.2?
posted by ny_scotsman at 7:23 AM on March 6, 2006

Sounds like a clock issue. I'm not familiar with Audacity, but there's probably a setup dialog there where you can define where Audacity gets its clock from. If it's set to "internal", try setting it to "external" and record some more.
posted by goodnewsfortheinsane at 7:24 AM on March 6, 2006

You could try the soundonsound.com linux forum as well.
posted by lunkfish at 7:25 AM on March 6, 2006

Reducing the size of your audio buffer can correct latency issues, however this may introduce new problens concerning audio artifacts. Oftentimes, a laptop PC isn't beefy enough for this type of work without really tweaking your settings.

What's Audacity's audio driver? Try using ASIO if you can.
posted by sourwookie at 7:50 AM on March 6, 2006

If the tracks gradually drift out of sync, it's possible that Audacity is "skipping" occasionally during the recording because it isn't fast enough to keep up with the incoming data. The Audacity wiki has some tips for avoiding skipping.

You should also make sure that your speakers and microphone are both connected to the same audio device (e.g. if you have both an internal sound card and a USB adapter). Clock chips in different devices might be calibrated slightly differently, and this would cause the same symptoms.
posted by mbrubeck at 9:06 AM on March 6, 2006

(I should've mentioned I'm using WinXP, 512 MB RAM, AMD Athlon 64 3200+)

Do you see the claps and the beats drifting on Audacity's track display?

Yep.

Have you tried going back to 1.2?

No, but I'll give that a shot.

but there's probably a setup dialog there where you can define where Audacity gets its clock from.

I looked, but couldn't find anything that seemed like that.

What's Audacity's audio driver? Try using ASIO if you can.

I did a little reading on ASIO, but I'm a little unsure. Do I download and install a generic ASIO driver, or do I need one for my soundcard? Or do you mean it's just something within the software?

The Audacity wiki has some tips for avoiding skipping.

That sounds like it might work, I'm going to try it out. (It sucks not having the internet in the same place where I do my work.) I also followed the links there to the other audio programs, and I downloaded Krystal Audio Engine.

You should also make sure that your speakers and microphone are both connected to the same audio device

Yup, they are.

Thanks everyone for the advice so far.
posted by ludwig_van at 7:24 AM on March 7, 2006

ASIO is a type of driver available for some sound cards; ASIO drivers are often better at things like latency than the older "WMME" drivers. But because of licensing reasons, we can't distribute Audacity with ASIO support.
posted by mbrubeck at 10:18 AM on March 7, 2006

Whoa, I didn't realize you were a developer for Audacity, mbrubeck. Nice to have someone around who's a little closer to the fire.
posted by goodnewsfortheinsane at 12:24 PM on March 7, 2006