[sdiy] Digital filtering (Oversampling and downsampling)

[Ben Lincoln]

On Mon, August 3, 2009 8:59 am, Tom Wiltshire wrote:

> The final part of an oversampling system is to reduce the internal
> sample rate for output. This is done by applying a digital filter to
> remove any unwanted high frequency content (remember that a signal
> with a sample rate of 384KHz could have frequencies up to 192KHz) and
> then chucking away most of the samples (7 out of 8 to get from 384 to
> 48KHz).

Wouldn't you want to take the average (or median, which would be faster to
compute) for best results? As opposed to just taking every 8th sample
as-is, I mean. Maybe that's what you meant and I misread it.

That's an honest question - I've written some simple digital audio-related
software, but never an actual DSP, so I don't know what the
performance/quality trade off is like for real-time processing.

- Ben