added PyAudio direct play example

examples/pyaudio-sstv.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python
+
+"""
+Demonstrates playing the generated samples directly using PyAudio
+Tested on PyAudio 0.2.7 http://people.csail.mit.edu/hubert/pyaudio/
+"""
+
+from __future__ import division
+from sstv import SSTV
+from time import sleep
+from itertools import islice
+import struct, pyaudio
+
+class PyAudioSSTV(object):
+    def __init__(self, sstv):
+        self.pa = pyaudio.PyAudio()
+        self.sstv = sstv
+        self.fmt = '<' + SSTV.BITS_TO_STRUCT[sstv.bits]
+
+    def __del__(self):
+        self.pa.terminate()
+
+    def execute(self):
+        self.sampler = self.sstv.gen_samples()
+        stream = self.pa.open(
+                format=self.pa.get_format_from_width(self.sstv.bits // 8),
+                channels=1, rate=self.sstv.samples_per_sec, output=True,
+                stream_callback=self.callback)
+        stream.start_stream()
+        while stream.is_active():
+            sleep(0.5)
+        stream.stop_stream()
+        stream.close()
+
+    def callback(self, in_data, frame_count, time_info, status):
+        frames = ''.join(struct.pack(self.fmt, b)
+                for b in islice(self.sampler, frame_count))
+        return frames, pyaudio.paContinue
+
+
+def main():
+    from PIL import Image
+    from grayscale import Robot8BW
+
+    img = Image.open("160x120bw.png")
+    sstv = Robot8BW(img, 44100, 16)
+    sstv.vox_enabled = True
+    PyAudioSSTV(sstv).execute()
+
+if __name__ == '__main__':
+    main()