Initial commit

audio_python/sound_alsa.py

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+import os
+import sys
+from math import pi, sin, tanh
+
+from keyboard import setup_term
+from pyalsa import Alsa
+
+SAMPLE_RATE = 44_100
+LATENCY = 50_000  # 50ms
+INT16_MAX = 2**15 - 1
+alsa = Alsa(SAMPLE_RATE, LATENCY)
+
+keys = "azertyuiop"
+gain = 0.5
+base_freq = 440.0
+freqs = [0.0] * len(keys)
+phases = [0.0] * len(keys)
+mix_mode = "voice_count"
+buf_size = 512
+
+
+def tanh_mix(voices, gain):
+    sample = tanh(gain * sum(voices))  # apply tanh with gain (soft clipping)
+    return sample
+
+
+def voice_count_mix(voices, gain):
+    sample = sum(voices) / len(voices)  # normalize to [0, 1] range
+    sample = sample * gain
+    return sample
+
+
+def clamp(x, a, b):
+    return max(a, min(b, x))
+
+
+os.set_blocking(sys.stdin.fileno(), False)
+with setup_term():
+    while True:
+        buf = [0] * buf_size
+        for i in range(buf_size):
+            voices = [0.0] * len(keys)
+            for j in range(len(keys)):
+                phase, freq = phases[j], freqs[j]
+                if freq == 0:
+                    continue
+                voices[j] = sin(phase)
+                phases[j] += 2 * pi * freq / SAMPLE_RATE
+
+            if voices == []:
+                continue
+
+            # mixing
+            mixfn = tanh_mix if mix_mode == "tanh" else voice_count_mix
+            mix = int(mixfn(voices, gain) * INT16_MAX)
+            buf[i] = clamp(
+                mix, -INT16_MAX - 1, INT16_MAX
+            )  # final clamp to int16 range, just in case
+        alsa.write(buf)  # this is blocking
+
+        # input handling
+        key = sys.stdin.read(1)
+        if key == "q":
+            break
+        elif key == " ":
+            mix_mode = "tanh" if mix_mode == "voice_count" else "voice_count"
+            print(mix_mode)
+        elif key is not None and key != "" and key in keys:
+            i = keys.index(key)
+            if freqs[i] == 0:
+                freqs[i] = base_freq * (2 ** (i / 12))
+            else:
+                freqs[i] = 0