16 bits to 8 -- Re: [sdiy] Sunsyn,PPG wavetable oscillator.

[Antti Huovilainen]

On Mon, 19 Jan 2004, Glen wrote:

> Dithering increases ambient noise levels, in an effort to hide a small
> amount of distortion. Personally, I never thought it was worth putting up
> with the added noise, but I seem to be in the minority.

Simple quantization creates audible distortion. Dithering eliminates this
distortion but trades off in increased noise (around 6dB which is not
that much). If you use noise-shaping, you can move most of the noise to
frequencies where ear is much less sensitive, so you can make the noise
almost inaudible even with just 8 bit resolution.

The simplest noise shaped dither would be
y[n] = quantize(x[n] + (noise[n] - noise[n-1])).

This makes the noise power be same but moves some of it to higher
frequencies at which ear is less sensitive.

Antti

Give a man a fire, and he'll be warm that day,
Set him alight and he'll be warm for the rest of his life