|
Rockbox mail archiveSubject: Re: DSP: low pass filterRe: DSP: low pass filter
From: Dave Hooper <dave_at_beermex.com>
Date: Sun, 14 Aug 2005 21:27:10 +0100 Hold on, hold on. A low-pass filter is WAY easier than an FFT - FFT is overkill for beat detection. Check out implementations of Butterworth FIR filters, or even just hack something together by averaging a bunch of samples together: at 44.1kHz, if you average 128 samples at a time, you have a rough-and-ready 180Hz filter. The existing peakmeter code looks at peaks over a frame-worth of samples - you just change that so that it builds an average every 128 samples, and then looks at peaks across all of those averages. Should be a piece of cake. ----- Original Message ----- From: "Magnus Holmgren" <lear_at_algonet.se> To: "Rockbox development" <rockbox_at_cool.haxx.se> Sent: Sunday, August 14, 2005 4:55 PM Subject: Re: DSP: low pass filter > Tomas wrote: > >> Ok, then the next problem is... how to make a lowpass filter if I have an >> FFT? (I've found some other FFT sources too) > > What you get out of an FFT is a set of amplitudes for a set of equal-sized > frequency ranges. So just check the right bunch of amplitudes. Wikipedia > should explain the basics... > > Magnus > _______________________________________________ > http://cool.haxx.se/mailman/listinfo/rockbox > _______________________________________________ http://cool.haxx.se/mailman/listinfo/rockbox Received on 2005-08-14 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |