[sdiy] Looking for cheap lowpass filter algorithm

[Antti Huovilainen]

On Wed, 16 Aug 2006, Seb Francis wrote:

> So I'm looking for a cheap way in software to filter the high 
> frequencies to make the distortion less noticeable.  Any pointers?

Any digital signal processing book will tell you how.

You want a sharp lowpass filter both at the input and at the output 
(output filter is slightly less critical). Typically a FIR filter is used 
for this. What this means in practise is at least 2*16 multiplies per 
sample. If you tell us how cheap is cheap, I could easily design the 
filters for you.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova