Added DJ audio track player

synthisizer.cpp

@@ -0,0 +1,33 @@
+#include "synthisizer.h"
+
+#include <cmath>
+
+#include "midicontainers.h"
+
+constexpr double pi = std::acos(-1);
+
+void Synthisizer::writeSamples(frame_t *begin, frame_t *end)
+{
+    if (m_frequency)
+        std::transform(begin, end, begin, [&](frame_t frame){
+            std::transform(std::cbegin(frame), std::cend(frame), std::begin(frame),
+                           [value=std::sin(m_phase)](const sample_t &sample) { return sample + value; });
+
+            m_phase += pi*2./sampleRate*m_frequency;
+            if (m_phase >= pi*2.)
+                m_phase -= pi*2.;
+
+            return frame;
+        });
+}
+
+void Synthisizer::messageReceived(const midi::MidiMessage &message)
+{
+    if (message.cmd == midi::Command::NoteOn)
+        m_frequency = 440.*std::pow(std::pow(2., 1./12.), message.note-48);
+    else if (message.cmd == midi::Command::NoteOff)
+    {
+        if (m_frequency == int16_t(440.*std::pow(std::pow(2., 1./12.), message.note-48)))
+            m_frequency = 0;
+    }
+}