Slowed down recording (and fixing it)?

[ramparts]

I have a radio show at the local (college) station, and recorded it this week using Audacity on the in-studio XP machine. I exported to a 128 CBR MP3. Everything recorded fine until a seemingly random point (in the middle of a song), and from there on the rest of the show is significantly slowed down (and the recorded file is about 20 minutes longer than the show). I don't know why this happened but I was trying to fix it with Audacity at home, and it looks like I can fix it by speeding up by about 117% (I'm going to do the exact math later). So my questions are:

-Why (if anyone has seen this before) might this have happened and what can I do to prevent it?
-Is there a way to fix it besides figuring out how much it's been slowed down and manually speeding it back up?
-I have a bunch of .au files, I don't know if they're the project files since I thought I didn't save the project, but will those be more useful to me than the MP3 (besides the fact that working with the MP3 and re-encoding will be lossy)?

[steve]

This is strange - there has recently been a spate of people having this problem, but just in the last month or so.

I'm presuming that you're using Audacity 1.2.6?
This version has been around for ages, so it would not explain why we should be seeing this problem occurring now and not previously.

Changes in speed while recording are usually caused by faulty sound cards, but more commonly it is a gradual drift in speed rather than a sudden jump. I'm wondering if a computer or sound card has recently come on the market with a proneness to this problem. What hardware are you using (make and model of computer and sound card)? Is this a new machine?

Some sound cards have the ability to record at various sample rates, but exhibit stability problems at certain sample rates, while being quite happy at others. What sample rate are you recording at?

Changing the default sample rate (Edit Menu > Preferences > Quality) may prevent the problem.

-Is there a way to fix it besides figuring out how much it's been slowed down and manually speeding it back up?

That would be the way to fix it. (or just a bit of trial and error).

-I have a bunch of .au files, I don't know if they're the project files since I thought I didn't save the project, but will those be more useful to me than the MP3 (besides the fact that working with the MP3 and re-encoding will be lossy)?

The .au files will almost certainly be part of the project data - leave them alone or you will probably destroy the project. Read here to learn more about this: http://audacityteam.org/wiki/index.php? ... ement_Tips

We generally recommend that people make a backup copy of their recordings by Exporting as WAV files (which can be burned to CD if you are short of hard disk space). OK, it's probably too late for this project, but worth keeping in mind for the future.