71 lines
1.7 KiB
C++
71 lines
1.7 KiB
C++
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#include "tone.h"
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/**
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* Přidán attack - zmizí rušivé lupání, prodlouží se obsluha tónu.
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* */
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extern "C" const short onePeriod[];
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extern "C" const unsigned int midiTones[];
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extern "C" const unsigned int attackTable[];
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static constexpr unsigned defFall = 16u;
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static constexpr unsigned maxAttack = 127u;
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Tone::Tone() noexcept {
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ampl = 0; freq = 0; base = 0; atck = 0;
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fall = defFall;
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}
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void Tone::setAmpl (unsigned int a) {
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ampl = a;
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}
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void Tone::setFreq (unsigned int f) {
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freq = f;
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}
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void Tone::setMidiOn (unsigned int m) {
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freq = midiTones [m & 0x7F];
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if (freq) atck = maxAttack;
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fall = 1;
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}
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void Tone::setMidiOff (void) {
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fall = defFall;
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/*
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base = 0;
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freq = 0;
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*/
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}
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void Tone::setFall (unsigned int f) {
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fall = f;
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}
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int Tone::step (void) {
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unsigned int k,t;
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int y;
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// Spočteme index x pro přístup do tabulky
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const unsigned x = (base >> 16) & 0xFF;
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y = onePeriod [x]; // vzorek vezmeme z tabulky
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// k je horní půlka amplitudy
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k = ampl >> 16;
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y *= k; // vzorek násobíme amplitudou (tedy tím vrškem)
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y >>= 12; // a vezmeme jen to, co potřebuje DAC
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k *= fall; // Konstanta fall určuje rychlost poklesu amplitudy,
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// čím více, tím je rychlejší. Pokud by bylo 1, pokles je 2^16 vzorků, což už je pomalé.
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base += freq; // časová základna pro další vzorek
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if (atck) { // přidán attack = náběh amplitudy
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t = attackTable [atck]; // z tabulky
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if (t > ampl) ampl = t; // prevence lupání - nemí být skok amplitudy
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atck -= 1; // dočasovat k nule
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} else
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ampl -= k; // exponenciální pokles amplitudy
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// a je to
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return y;
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}
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