Hi Frank, Just a minor point, but yes, you want the inverse FFT. (Um, it’s the same thing, pretty much, the main issue being scaling, depending on implementation. Just highlighting that specifying frequency and converting to time domain is “inverse”, the other is plain or “forward”.)
My series on wavetable oscillators may or may not help. But in a nutshell, the FFT gives a vast improvement in the speed of calculating harmonically related sines, and the longer the table, the bigger the win. http://www.earlevel.com/main/category/digital-audio/oscillators/wavetable-oscillators/?order=ASC <http://www.earlevel.com/main/category/digital-audio/oscillators/wavetable-oscillators/?order=ASC> > On Apr 16, 2018, at 8:46 AM, Frank Sheeran <fshee...@gmail.com> wrote: > > RBJ says: > > > are you making wavetables, Frank?? is that what you're doing? > > Well yes. > > More specifically, I'm adding Wavetable SYNTHESIS to my long-standing > software synthesizer. > > It's been generating waveforms the patch-writer specifies by formula, and/or > by setting individual harmonics, and the like, for years. It takes a portion > of a second to do for a single wave. I generate several bandwidth-limited > versions (by default 1/4 octave apart). Some call the resulting data > structure a mipmap, some call it a wavetable, but the salient point is that > there's only one spectrum (at least, at any given pitch range). > > The problem is that now I'd doing it for say 32 or 64 or 256 waveforms at > once it can take a full second on a fast modern CPU. > > So, the simple symmetry-based solution I had before isn't really fit for > purpose. > > > > To all: thanks for all the pointers. I'm not a maths/acoustics guy, just a > humble software developer, but I'll work through all the references and see > how much I understand. > > > > _______________________________________________ > dupswapdrop: music-dsp mailing list > music-dsp@music.columbia.edu > https://lists.columbia.edu/mailman/listinfo/music-dsp
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