PyRtAudio: demo of how to use numpy

contrib/python/pyrtaudio/PyRtAudioTest.py

@@ -30,6 +30,41 @@ class callback:
             print('.')
             return 1
 
+try:
+    # if we have numpy, replace the above class
+    import numpy as np
+    class callback:
+        def __init__(self, gen):
+            print('Using Numpy.')
+            self.freq = 440.
+            t = np.arange(256, dtype=np.float32) / 48000.0
+            self.phase = 2*np.pi*t
+            self.inc = 2*np.pi*256/48000
+            self.k = 0
+        def __call__(self, playback, capture):
+            # Calculate sinusoid using numpy vector operation, as
+            # opposed to per-sample computations in the generator
+            # above that must be collected and packed one at a time.
+            self.k += 256
+            if self.k > 48000:
+                self.freq *= 2**(1/12.)
+                self.k = 0
+            self.phase += self.inc
+            samples = 0.5*np.cos(self.phase * self.freq)
+
+            # Ensure result is the right size!
+            assert samples.shape[0] == 256
+            assert samples.dtype == np.float32
+
+            # Use numpy array view to do a once-copy into memoryview
+            # (ie. we only do a single byte-wise copy of the final
+            # result into 'playback')
+            usamples = samples.view(dtype=np.uint8)
+            playback_array = np.array(playback, copy=False)
+            np.copyto(playback_array, usamples)
+except ModuleNotFoundError:
+    print('Numpy not available, using struct.')
+
 dac = rt.RtAudio()
 
 n = dac.getDeviceCount()