[tests] add script to create sound file with python only

diff --git a/tests/create_tests_source.py b/tests/create_tests_source.py
new file mode 100755 (executable)
index 0000000..a44c0d1
--- /dev/null
+++ b/tests/create_tests_source.py
@@ -0,0 +1,39 @@
+#! /usr/bin/env python
+
+""" Create a simple stereo file containing a sine tone at 441 Hz, using only
+numpy and python's native wave module. """
+
+import wave
+import numpy as np
+
+
+def create_sine_wave(freq, samplerate, nframes, nchannels):
+    """ create a pure tone """
+    # samples indices
+    _t = np.tile(np.arange(nframes), (nchannels, 1))
+    # sine wave generation
+    _x = 0.7 * np.sin(2. * np.pi * freq * _t / float(samplerate))
+    # conversion to int and channel interleaving
+    return (_x * 32767.).astype(np.int16).T.flatten()
+
+
+def create_test_sound(pathname, freq=441, duration=None,
+                      sampwidth=2, framerate=44100, nchannels=2):
+    """ create a sound file at pathname, overwriting exiting file """
+    nframes = duration or framerate  # defaults to 1 second duration
+    fid = wave.open(pathname, 'w')
+    fid.setnchannels(nchannels)
+    fid.setsampwidth(sampwidth)
+    fid.setframerate(framerate)
+    fid.setnframes(nframes)
+    frames = create_sine_wave(freq, framerate, nframes, nchannels)
+    fid.writeframes(frames.tobytes())
+    fid.close()
+    return 0
+
+
+if __name__ == '__main__':
+    import sys
+    if len(sys.argv) < 2:
+        sys.exit(2)
+    sys.exit(create_test_sound(sys.argv[1]))