[Harry van Haaren] >On Mon, Mar 18, 2013 at 11:45 PM, Fons Adriaensen <[email protected]>wrote: >> A critically damped >> second order lowpass with a rise time of 30 ms or so will eliminate all >> audible artefacts. It's very low on CPU and you only need to run it while >> the gain is changing. > >Although I understand the words & their meaning, I have no idea how to >start implementing such a filter. >I've found a 1st order algorithm on musicdsp: [...]
A 2nd-order IIR filter is often called a "biquad"; at musicdsp, look for that instead. There should also be plenty of formulae for computing 2nd-order lowpass filter coefficients. Those following tradition (like RBJ's lovely cookbook at musicdsp) will ask for filter Q, which is 0.5 for critical damping. >How is the "rise time" determined here? As a function of the filter's damping (zeta = 2*Q) and frequency: http://en.wikipedia.org/wiki/Rise_time _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/listinfo/linux-audio-dev
