start of procedural synth reimplementation

synth/synth.h

@@ -0,0 +1,89 @@
+#pragma once
+
+#include <cstddef>
+#include <memory>
+#include <vector>
+
+using namespace std;
+
+namespace trnr {
+
+enum m_event_type {
+	note_on = 0,
+	note_off,
+	pitch_wheel,
+	mod_wheel
+};
+
+struct m_event {
+	m_event_type type;
+	int offset;
+	int midi_note;
+	float velocity;
+	double data;
+};
+
+template <typename voice>
+struct synth {
+	vector<shared_ptr<voice>> voice_ptrs;
+	int active_voice_count;
+};
+
+template <typename voice>
+void synth_init(const synth<voice>& s, size_t num_voices, double samplerate)
+{
+	s.active_voice_count = 0;
+	s.voice_ptrs.reserve(num_voices);
+	for (size_t i = 0; i < num_voices; ++i) { s.voice_ptrs.emplace_back(make_shared<voice>()); }
+}
+
+template <typename voice, typename sample>
+void synth_process_block(const synth<voice>& s, sample** audio, const vector<m_event>& midi_events, int frames)
+{
+	int current_frame = 0;
+	int event_index = 0;
+
+	for (const auto& ev : midi_events) {
+
+		int event_frame = ev.offset;
+		int voice_index = -1;
+
+		switch (ev.type) {
+		case note_on:
+			for (size_t i = 0; i < s.active_voice_count; ++i) {
+				// attempt to find a free voice
+				if (!s.voice_ptrs[i]->is_busy) { voice_index = i; }
+			}
+			// if no free voice is found, steal one
+			if (voice_index < 0) {
+				// Try to find a voice that is not gated (not playing a note)
+				for (size_t i = 0; i < s.active_voice_count; ++i) {
+					if (!s.voice_ptrs[i]->gate) { voice_index = i; }
+				}
+				// If all voices are gated, steal one round-robin
+				voice_index = s.index_to_steal;
+				s.index_to_steal = (s.index_to_steal + 1) % s.active_voice_count;
+			}
+
+			// If a voice is found, remember index
+			// if (voice_index >= 0) { v->note_on(ev.midi_note, ev.velocity); }
+			break;
+		case note_off:
+			break;
+		case pitch_wheel:
+			break;
+		case mod_wheel:
+			break;
+		}
+
+		// process all voices from current frame to event frame
+		for (int i = 0; i < s.active_voice_count; i++) {
+			auto& v = s.voice_ptrs[i];
+			if (i == voice_index) { v.midi_event = ev; }
+			if (current_frame < event_frame) { v->process_block(audio, current_frame, event_frame); }
+		}
+
+		current_frame = event_frame;
+	}
+}
+} // namespace trnr