Hi Frank, I think that your main cpu issue is related to the fact that you don't need to recalculate the coefficients on every sample. You can set a variable/flag that can tell you when a change of the parameters is needed and then use this to trigger the computation. In addition, you can set this on a window/frame-based system. At the beginning of each frame, you can check if a change is needed, and based on that compute and update the parameters.
In the past, I implemented audio classes based on the base class shown in http://www.redwoodaudio.net/Tutorials/juce_for_vst_development__intro6.html at point 3 (end of the page). Maybe you can try to have a look at it. Hope this helps, Davide On Sun, 12 Jan 2020 at 07:07, Frank Sheeran <fshee...@gmail.com> wrote: > I have a couple audio programming books (Zolzer DAFX and Pirkle Designing > Audio Effect Plugins in C++). All the filters they describe were easy > enough to program. > > However, they don't discuss having the frequency and resonance (or > whatever inputs a given filter has--parametric EQ etc.) CHANGE. > > I am doing the expensive thing of recalculating all the coefficients every > sample, but that uses a lot of CPU. > > My questions are: > > 1. Is there a cheaper way to do this? For instance can one pre-calculate > a big matrix of filter coefficients, say 128 cutoffs (about enough for each > semitone of human hearing) and maybe 10 resonances, and simply > interpolating between them? Does that even work? > > 2. when filter coefficients change, are the t-1 and t-2 values in the > pipeline still good to use? I am using them and it SEEMS fine but now and > then the filters in rare cases go to infinity (maybe fast changes with high > resonance?) and I wonder if this is the cause. > > 3. Would you guess that most commercial software is using SIMD or GPU for > this nowadays? Can anyone confirm at least some implementations use SIMD > or GPU? > > Frank > > _______________________________________________ > dupswapdrop: music-dsp mailing list > music-dsp@music.columbia.edu > https://lists.columbia.edu/mailman/listinfo/music-dsp
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