demo

py/playbacktest.py

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+#!/usr/bin/env python
+
+## playbacktest.py
+##
+## This is an example of a simple sound playback script.
+##
+## The script opens an ALSA pcm for sound playback. Set
+## various attributes of the device. It then reads data
+## from stdin and writes it to the device.
+##
+## To test it out do the following:
+## python recordtest.py out.raw # talk to the microphone
+## python playbacktest.py out.raw
+
+
+from __future__ import print_function
+
+import sys
+import time
+import getopt
+import alsaaudio
+
+def usage():
+    print('usage: playbacktest.py [-d <device>] <file>', file=sys.stderr)
+    sys.exit(2)
+
+if __name__ == '__main__':
+
+    device = 'default'
+
+    opts, args = getopt.getopt(sys.argv[1:], 'd:')
+    for o, a in opts:
+        if o == '-d':
+            device = a
+
+    if not args:
+        usage()
+
+    f = open(args[0], 'rb')
+
+    # Open the device in playback mode. 
+    out = alsaaudio.PCM(alsaaudio.PCM_PLAYBACK, device=device)
+
+    # Set attributes: Mono, 44100 Hz, 16 bit little endian frames
+    out.setchannels(1)
+    out.setrate(44100)
+    out.setformat(alsaaudio.PCM_FORMAT_S16_LE)
+
+    # The period size controls the internal number of frames per period.
+    # The significance of this parameter is documented in the ALSA api.
+    out.setperiodsize(160)
+
+    # Read data from stdin
+    data = f.read(320)
+    while data:
+        out.write(data)
+        data = f.read(320)
+            
+