[PD] editing pd silence - dither

[Marvin Humphrey]

On Sun, Oct 23, 2011 at 02:20:38PM -0400, Mathieu Bouchard wrote:
> Personally, I don't understand what's the point of dither in audio. Maybe 
> it's just an evil plot to make CD quality sound like 8-track cartridges.

Without dither, truncation error becomes truncation distortion.  It is
correlated with the signal, yet not harmonic.  While under certain
circumstances this can be exploited as a special effect, it is not desirable
when your goal is fidelity.

The use of dither in digital audio is directly analogous to the use of
dither to defeat posterization and achieve the illusion of smooth color
transitions in visual images with limited color levels.

    http://en.wikipedia.org/wiki/File:Colour_banding_example01.png

In that image, the "24-bit gradient" would be analogous to the full width
audio signal prior to bit depth reduction, the "8 bit gradient, dithered"
would be analogous to dithered audio, and the "8 bit gradient" displaying
obvious color banding would be analogous to truncated audio.

Marvin Humphrey