1 files changed, 47 insertions, 0 deletions
diff --git a/src/adsr.c b/src/adsr.c
new file mode 100644
index 0000000..8ef2ba9
--- /dev/null
+++ b/src/adsr.c
@@ -0,0 +1,47 @@
+#include "adsr.h"
+#include "synth_engine.h"
+#include "synth_math.h"
+
+float
+adsr_amplitude(adsr_t *adsr, float noteOn, float noteOff, unsigned long long elapsed)
+{
+  float mod = 0.0;
+  float release_amplitude = 0.0;
+
+  float lifetime = elapsed / (float)SAMPLE_RATE;
+  //float time_active = (noteOn  + lifetime) - noteOff;
+  float time_active = noteOn - noteOff + lifetime;
+
+  if (noteOn != 0 && noteOff == 0) {
+    if (lifetime < adsr->a)
+      mod = (lifetime / adsr->a)*(lifetime / adsr->a) * adsr->peak;
+
+    if (lifetime >=  adsr->a && lifetime <= ( adsr->a +  adsr->d))
+      mod = ((lifetime - adsr->a) / adsr->d) * (adsr->s - adsr->peak) + adsr->peak;
+
+    if (lifetime > (adsr->a + adsr->d))
+      mod = adsr->s;
+  }
+  else { // Note is off
+    if (lifetime < adsr->a)
+      release_amplitude = (lifetime / adsr->a)*(lifetime / adsr->a) * adsr->peak;
+
+    if (lifetime >= adsr->a && lifetime <= (adsr->a + adsr->d))
+      release_amplitude = ((lifetime - adsr->a) / adsr->d) * (adsr->s - adsr->peak) + adsr->peak;
+
+    if (lifetime > (adsr->a + adsr->d))
+      release_amplitude = adsr->s;
+
+    mod = (time_active / adsr->r) * (0.0 - release_amplitude) + release_amplitude;
+
+    if (adsr->r < 0) {
+      mod = adsr->s;
+    }
+
+  }
+  // Amplitude should not be negative
+  if (mod <= 0.000)
+    mod = 0.0;
+
+  return clamp(mod);
+}