Yes, I think you can do phase modulation with those filters. They are referred to colloquially as "phasor filters", because their phase is manipulated in order to rotate a vector around the complex plane...
On Tue, Apr 3, 2018 at 8:16 AM, gm <g...@voxangelica.net> wrote: > > Yes it's related, I dont recall if I used one of these filters > in my first implementation which was several years ago. > I used a complex filter before I used the SVF and AP. > > But I think you can't do full phase modulation with such filters? > I think that was my motivation to apply the rotation outside of the filter. > > Either way it seems lighter on cpu when you use the external rotation with > parabolas instead of trig operations since you dont have to constantly > adapt the internal state of the filter. > > A drawback of the method in general with either filter is that > you can cancel the internal state with an impulse. > > I havent figured out what the best excitation signal is. > > The paper you linked suggests to delay the impulse until a zero crossing > but that is not an option in my use cases. > > Am 03.04.2018 um 01:46 schrieb Corey K: > > Your idea seems to bear a few similarities to this (just in case you > haven't seen it already): > https://ccrma.stanford.edu/~jos/smac03maxjos/ > > > > On Mon, Apr 2, 2018 at 2:46 PM, gm <g...@voxangelica.net> wrote: > >> >> I don't know if this idea is new, I had it for some time but have never >> seen it mentioned anywhere: >> >> Use a filter with high q and rotate it's (complex) output by the (real) >> output >> of another filter to obtain a phase modulated sine wave. >> Excite with an impulse or impact signal. >> >> It's basically crossed between modal and phase modulation synthesis. >> >> Now there are some ideas to this to make it practical and a useful >> substitute for phase modulation and FM: >> >> You can use a state variable filter with an additional allpass instead of >> the complex filter to obtain a filter you can pitch modulate in audio >> (useful for drum synthesis ect) (or maybe the 90 shift can be designed >> more efficiently >> into the SVF IDK.) >> >> Instead of expensive trig calculations for the rotation, or using >> the normalized complex signal form the other filter (also expensive) >> just use a very coarse parabolic sine/cosine approximation and the real >> signal, >> the difference is really very small sonically, since the modulator is >> still sine >> and the radius stays around 1 so it's the effect of a small amplitude >> modulation on the modulator >> caused by the slight deviation of the circle. >> I couldnt tell the difference when I tested it first. >> >> You need 7 mults and 4 adds in addition to the SVF for the AP and >> rotation per carrier. >> >> But you save an envelope for each operator and have a pretty efficient >> sine operator with the SVF. >> And you get all the benfits of phase modulation over frequency modulation >> of the >> filter cutoff. >> It's very useful for drum synthesis but also useful for some other >> percussive sounds like "FM" pianos etc. >> >> Here is an audio demo, with cheap "soundboard" and some other fx added: >> https://soundcloud.com/traumlos_kalt/smoke-piano-test-1-01/s-W54wz >> >> I wonder if this idea is new? >> >> _______________________________________________ >> dupswapdrop: music-dsp mailing list >> music-dsp@music.columbia.edu >> https://lists.columbia.edu/mailman/listinfo/music-dsp >> >> > > > _______________________________________________ > dupswapdrop: music-dsp mailing > listmusic-dsp@music.columbia.eduhttps://lists.columbia.edu/mailman/listinfo/music-dsp > > > > _______________________________________________ > dupswapdrop: music-dsp mailing list > music-dsp@music.columbia.edu > https://lists.columbia.edu/mailman/listinfo/music-dsp >
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