Audacity added extra seconds to my record?


I’m using Audacity on macOS Catalina. But I’ve tested it on Windows 10 as well.

Situation is:

  • I’m recording video and sound from one device
  • Video is capturing by OBS. And sound by Audacity
  • On finish, I’m fitting video and audio in video editing program.

Magic starts here: the longer video is, sound becoming more and more desynchronized. It’s like Audacity added extra seconds to audio? I don’t know how to explain it.

Between clicking to start recording in OBS, and second in Audacity, I have a small delay - about 1-3 seconds. I need to switch between programs and click recording. But it’s not a problem - sometimes it takes me 1 second.

The problem is: when recording is done, OBS shows for ex. 1h:5m:15s of recorded video. But in Audacity…it’s like 1h:15s:25s. But…how. OK, I have always a little delay at start. But how’s it’s possible, that Audacity record more time, that video is.

Even if I manually synchronize sound and video in video editing program - it’s great at the begging. But it’s desynchronized after some time. And on start I’ve had 1 second of delay, but after 1 hour of recording, Audacity record for ex. 10 seconds more time than OBS.

I really can’t explain it properly. It’s like Audacity adds extra seconds on records. I really don’t know how to explain it. If my records take 1h:15 seconds, how Audacity could record 1h:15 seconds for example. It’s like a bending in time :wink:

At first I’ve thought that macOS Catalina is the problem, because Audacity have it’s problems on Catalina. But recording on Windows 10…this same strange issue. The longer sounds in capturing, the more seconds it have, more than captured video :-/

It seems that Audacity and OBS are recording at slightly different rates. Tracking down the how and why, then fixing the problem is probably beyond what we can do with a back-and-forth here on the forum.

What you can do is adjust the length of the Audacity recording to exactly match the length of the video recording, before you bring the Audacity recording into the video editor. However, this is tricky. You need events at the beginning and at the end of the video that you can exactly identify in the audio recording.

Let’s say the length of the video recording is 3600 seconds (1 hour) and the length of the audio recording is 3610 seconds (1 hr and 10 seconds). You want the audio recording to change from 3610 seconds to 3600 seconds. Select the entire audio recording in Audacity and do Effect > Change Tempo. In the section headed “Length (seconds)” the first box will read (in this example) “3610”. Enter “3600” in the second box and click “OK”. Export the track with a unique name. Import that new file into the video editor and see if it lines up. If not you’ll need to try again with a slightly different number.

– Bill

I agree that seems the most likely explanation. If this is the case, then the best effect to use for correcting is the “Change Speed” effect (rather than the “Change Tempo” effect).

The “Change Speed” effect is possibly a bit easier to use too, as it has time controls for the current and target lengths: Change Speed and Pitch - Audacity Manual