Changing bitrate changes length of the file.

I am so frustrated by this because it makes absolutely no sense.

I am exporting audio from camtasia into an mp3 file. It’s at 128 kbps. I proceed to import it to audacity and use the noise gate plug-in to silence the parts where I’m breathing.

Next, I export it as an mp3 at 128 kbps, then import to camtasia. But the audio is not the same length as the original file, even though the plugin doesn’t remove parts, just silences them.

But what’s even more weird is the fact that when I change the bitrate, it’ll change length. The higher the bitrate, the longer the file.

Anyone know what is causing this?

when I change the bitrate, it’ll change length.

When you change the WAV sample rate in Audacity and you do it in the wrong place, then yes, the length of the show will change. So if you try to do it in the management panel to the left of the track, the show length will shift as will the pitch, timbre and speed. However if you change the sample rate with the little window at the bottom of the Audacity Production Window, the Project Rate will change, but it will not change the show length or speed.

Exporting one show as 128 bit rate and then again at 360 bit rate like I just did results in exactly the same length show as each other. They’re not the same length as the original because MP3 has that odd data management thing that it needs to do which is why we tell people never do production in MP3. You can’t do precise timing tasks.


So, I just rendered the video in Camtasia, and it turns out the issue was Camtasia misreading the file somehow in its preview. So it was the correct length, 6:34 when rendered, but it looked wrong on the timeline.

Thanks for the help anyhow :stuck_out_tongue:

How do I delete a post?

Thanks for letting us know.

You can’t delete your own post right now, but it’s OK to leave this topic here because it contains some useful information for others who don’t know that MP3 adds silence padding or that changing sample rate in the track drop-down changes the length.