Thank you for all the help. Gain loss was finally fixed after normalizing. In an other hand, using fft and inverse effectively gave better results than FIR or IIR. With very rich signals, I can still hear an harmonic difference between WTs. I guess I could fix it by using more WTs than one every octave. I will try every 6 semitones. Best, Alex
De: "alexandre niger" <alexandre.ni...@ensea.fr> À: "music-dsp" <music-dsp@music.columbia.edu> Envoyé: Vendredi 29 Juin 2018 16:17:47 Objet: [music-dsp] wavetable filtering Hello everyone, I just joined the list in order to find help in making a wavetable synth. This synth would do both morphing and frequency wavetables. Morphing is a way to play different waveforms over time and so to get an additional sound dimension. Frequency wavetables are used to avoid aliasing by filtering harmonics the higher the frequency go. I started with the frequency wavetables and then I will do the morphing between different waveforms. As an intern at Rebel Technology, I started making wavetables patches from earlevel articles. In those patches, common waveforms are generated inside the code (tri, square, saw). Now I want to generate some more complex waveforms from an editor called WaveEdit (free). They come as 256 samples single cycle .wav files. Then I change them into static data in a header file. Once I have this, I can start with frequency wavetables. The key point of frequency wavetables is the filtering. I have to filter enough harmonics so the aliased frequencies do not come back under 18KHz (audiable range). But I must not filter too much if I don't want to get gain loss. At the moment I managed to make a 3550 taps FIR to filter every octave wavetables. Unfortunately, with complex harmonic rich waveforms, I still have audiable aliasing from 2kHz and gain/amplitude difference when wavetables cross. So now I am wondering: About aliasing, should I cascade two FIR instead of increasing the taps? That could be a solution if the stop band is not attenuated enough. According to octave fir1, stop band attenuation is 50dB to 70dB. About gain loss, will "harmonic rich signal" always sound lower when filtered even if gain is the same? I haven't normalize wavetables yet. I might have my answer afterwards. You can have a look at the patch code but you won't be able to try it if you don't get Rebel Technology Owl files. https://github.com/alexniger/OLWpatches-RebelTech/blob/master/WTExtWavePatch.hpp All other links are in the readme. Best, Alex
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