Amplify slider

[OurJud]

I've read the wiki entry on this effect and kind of understand it, but it clearly states I can amplify the clip by dragging the slider to the right. However, as soon as I move even the tiniest bit to the right, all the buttons become greyed out.

I can lessen the volume with the slider, and I can increase it if I just go with the defualt setting and press OK, but any movement to the right with the slider greys out the buttons.

What am I missing?

[DVDdoug]

The purpose is to prevent clipping (distorted flat-topped waves). If you in-check the Allow Clipping option, you can go louder, but you may get distortion when you export.

Audacity has pre-scanned your file and it knows the peak value. (Most commercial releases are already normalized/maximized*).

There is a digital limit of 0dBFS for your analog-to-digital converter, digital-to-analog-converter, and most audio file formats such as regular integer WAV files.

Like most audio editors, Audacity uses floating point internally so Audacity itself can go over 0dB. But, if you play the file at full-volume or export to "regular" WAV you'll get clipping.

Note that perceived loudness does not correlate well with peak level so if you normalize/maximize all of your files, some will sound louder than others.




* MP3 is not limited to 0dB and many commercial MP3s will go slightly over 0dB. (MP3 is lossy, the waveshape changes, and some peaks get higher and some peaks get lower.)

[OurJud]

Ah, I see!

Thank you.

[steve]

* MP3 is not limited to 0dB

That is technically true, but if you try exporting a file that goes a long way over 0 dB, and then import it back into Audacity, you will see that it is still clipped. (I presume that this is a limitation of the encoder, or decoder, or both).