On Tue, Mar 19, 2013 at 08:15:41PM +0100, Tim Goetze wrote: > [Fons Adriaensen] > >Exactly the same with the form I proposed, w, a, b need to be computed > >just once, not for every gain change. In fact only w depends on the > >sample rate, a and b are fixed constants. > > Ah yes, sorry, I see that now. > > If that extra operation comes around to bite hard enough, I'll be sure > to chain two 1st-order lowpass filters.
There is a much more important (in some use cases) feature of this form: you can change 'w' (cutoff frequency c.q. settling time) instantly without introducing transients into the signal. Doing this with a biquad would generate a step in the output. So it's the ideal form for a 'voltage controlled' filter. In fact the famous 'Moog ladder' is just the same but using four first order sections instead of two. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev