On Sun, Aug 25, 2013 at 12:21:52AM +0200, Tim Goetze wrote: > I'm planning to evade this problem by crossfading between two parallel > static filters. Some phase mismatch issues can probably be expected > when the parameter sweep covers a larger range, but I'm hopeful it > will turn out not to be much of a problem in actual practice, and that > we will find out soon. It really needs a fix. I doubt very much if that will provide a practiacal solution. The state of the filter depends on signal history. Depending on the parameters, this could be quite long. So you would either have to * run the new filter (with the new parameters) for some time before crossfading, which will complicate the code, or * copy the state of the old into the new filter, but with a biquad this can again produce quite heavy spikes wich may last much longer than your crossfade. This can happen even when both the new and old filter are set to 0 dB gain. The simple solution is to smooth the input parameters, limiting their rate of change. Nobody expects an EQ section to change from 100 Hz to 10 kHz in less than half a second (unless it's a synth VCF module, but then you definitely need something else than a biquad). 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-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
