Initial commit

audio_python/synth.py

@@ -0,0 +1,36 @@
+from math import pi, sin
+
+SAMPLE_RATE = 44_100
+INT16_MAX = 2**15 - 1
+
+def synth(note):
+    buf = [0] * 512
+    for i, _ in enumerate(buf):
+        note.phase = (note.phase + note.freq / SAMPLE_RATE) % 1.0
+        # oscillator
+        match note.waveform:
+            case "saw": sample = 2 * note.phase - 1.0
+            case "square": sample = 1.0 if note.phase < 0.5 else -1.0
+            case "sine": sample = sin(2 * pi * note.phase)
+            case "triangle": sample = 4 * abs(note.phase - 0.5) - 1.0
+            case _: sample = 0.0
+        # envelope
+        target = 1 if note.playing else 0
+        if target == 1:
+            note.gain = min(note.gain + 1 / (0.010 * SAMPLE_RATE), 0.2)  # attack
+        else:
+            note.gain = max(note.gain - 1 / (0.050 * SAMPLE_RATE), 0)  # release
+
+        # signal processing
+        if note.waveshaping:
+            drive = 2
+            sample *= abs(sample) * drive
+            #sample = tanh(drive * sample)
+        if note.lowpass:
+            note.lp += 0.05 * (sample - note.lp)
+            sample = note.lp * note.gain
+        else:
+            sample = sample * note.gain
+        # convert to 16-bit signed integer and feed to buffer
+        buf[i] = int(sample * INT16_MAX)
+    return buf