78 lines
2.9 KiB
C++
78 lines
2.9 KiB
C++
/*
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Peacock-8 VA polysynth
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Copyright 2024 Gordon JC Pearce <gordonjcp@gjcp.net>
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "voiceboard.hpp"
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static inline float poly3blep0(float t) {
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float t2 = t * t;
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return 2 * (t * t2 - 0.5f * t2 * t2);
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}
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static inline float poly3blep1(float t) {
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return -poly3blep0(1 - t);
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}
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void Voice::run(float *buffer, uint32_t pos, uint32_t samples) {
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// generate a full block of samples for the oscillator
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float y, t;
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if (subosc > 0) subosc = sub; else subosc = -sub;
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// this uses an adaptation of Mystran's Polyblep oscillator
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for (uint32_t i = 0; i < samples; i++) {
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y = delay;
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delay = 0;
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phase += omega;
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pwrc = ((pw - pwrc) *.01 ) + pwrc;
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// this is the clever bit
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while (true) {
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if (!pulseStage) {
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if (phase < pwrc) break; // it's not time for the PWM output to step
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t = (phase - pwrc) / (lastpw - pwrc + omega); // calculate fractional sample allowing for PW amount
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y -= 0.63 * poly3blep0(t); // magic numbers observed on oscilloscope from real synth
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delay -= 0.63 * poly3blep1(t);
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pulseStage = true;
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}
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if (pulseStage) {
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if (phase < 1) break; // it's not time to reset the saw
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t = (phase - 1) / omega;
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y += poly3blep0(t) * (0.8 * saw + 0.63 - subosc);
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delay += poly3blep1(t) * (0.8 * saw + 0.63 - subosc);
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pulseStage = 0;
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phase -= 1;
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subosc = -subosc;
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}
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}
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delay += saw * (0.8 - (1.6 * phase)); // magic numbers observed on oscilloscope from real synth
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delay += (0.63 - (pwrc * 1.26)) + (pulseStage ? -0.63f : 0.63f); // add in the scaled pulsewidth to restore DC level
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// the DC correction is important because the hardware synth is AC-coupled effectively high-passing
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// the signal at about 10Hz or so, preventing any PWM rumble from leaking through!
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delay += subosc;
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delay += ic29.noise[i+pos];
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lastpw = pwrc;
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buffer[i + pos] = y * 0.707;
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}
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}
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