Adjust tempo outputs longer than number of seconds entered.

Windows 10 Pro x64, Audacity 2.1.3, EXE installer.

I need to stretch an audio file to exactly 1:57:40 but when I enter 7060 seconds I get an exported file that’s 1:57:46. Why does it make it 6 seconds too long? The video I’m attempting to sync the audio track with is 1:57:43 but the audio cuts off 3 seconds before the end. I have the end of the audio cut precisely at its end.

Why can’t I just enter 1:57:40 instead of having to convert it to seconds? That’s like having to measure one’s height in millimeters.

The “High Quality” option ( gives much better accuracy than the faster “standard” algorithm.

You are probably using the wrong effect. In most cases, syncing tracks should be done with the “Change Speed” effect.
If you tell us exactly what you are doing, where the video / audio came from and why they need sync’ing), then we will be able to say with certainty, which of the two effects is the correct one for the job.

I just tried the Effect > Change Speed function. I entered 1:57:40 and let it do the change. I played some to see how it sounded. Pitch is of course much lower. Then I exported to AC3.

What did I get? 1:57:46 again.

Just did an export of the speed changed file to MP3. Bang on the desired time!

It appears there’s a problem with AC3 export. Perhaps stretching only a very small amount over on short files that adds up to be several seconds extra when the length gets near 2 hours.

More likely it’s a problem with your audio player. What are you using - iTunes? Windows Media Player?
To check the actual length of the audio file, import it back into Audacity.

Another thing; when you export, use a new, unique name - don’t overwrite the original. As you are working with lossy compressed formats, the sound quality will deteriorate a little each time it is re-encoded, so you should always start with the best quality file that you have, do all the processing that you need to, then export in the required format. If you need to export as an intermediate step, use a lossless format such as WAV.

It’s the length shown in the details view in Windows, and in VirtualDub and OpenShot. AC3 export is adding extra length but MP3 export is not.