[sdiy] Looking for cheap lowpass filter algorithm

[Seb Francis]

paul.maddox.mail-list at synth.net wrote:
> Seb,
>
>> So I'm looking for a cheap way in software to filter the high 
>> frequencies to make the distortion less noticeable.  Any pointers?
>>
>
> Lowpass filter on the input, *before* the ADC?
>

I thought someone might come up with an analog suggestion ;)

Unfortunately this is not practical as most of the time the software 
will use 48kHz sampling rate, and only switched in software to use 24kHz 
when delay time needs to be more than the RAM can hold.

Seb