This may be a bit tricky to explain, but I'll do my best.

I record footage with the Elgato software and my commentary with Audacity, the same way I've always done it (previously with an Hauppauge).

The first few times I recorded some videos, it was fine.

I start the Elgato capture, then 5 seconds I start the Audacity capture. Due to this, the duration of the Audacity recording is always 5 seconds BEHIND the Elgato recording. So when I stop the Elgato, Audacity is 5 seconds behind, and I then stop Audacity so that both recordings are the same length. This method helps me sync up the video and commentary tracks.

However, I have no idea if this problem is Audacity or the Elgato software, but what happens is... at a random point in both recordings, the Elgato will fall behind Audacity in recording... when I stop both captures, the Elgato can be 15 seconds short of the recording on Audacity.

For example, it SHOULD be:

Elgato: 11:10:00
Audacity: 11:05:00 ...5 seconds behind during the whole recording.

But most of the time, it's been:

Elgato: 11:10:00
Audacity: 11:25:00 ...gains MORE seconds during the recording?!

Audacity starts off behind, the at an unspecified amount of time later, overtakes the Elgato. It's almost like Audacity is finding 15 extra seconds, or the Elgato is losing 15 seconds somewhere. This does seem to be random, as the last few times I've done it.. its all be perfectly synced. Then out of nowhere, it does it again.

But like I said... I have no idea if Audacity or the Elgato software is at fault.

I used a stopwatch to see if both programs went too fast or slow, but using the recording software on their own, the durations have been spot on. Neither of them have gone too fast or too slow.

It's never done this before until now, nothing has changed with my computer or both softwares... any ideas?