playbacktest.py

#!/usr/bin/env python3
# -*- mode: python; indent-tabs-mode: t; c-basic-offset: 4; tab-width: 4 -*-

## 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 in Mono, 44100 Hz, 16 bit little endian frames
    # The period size controls the internal number of frames per period.
    # The significance of this parameter is documented in the ALSA api.

    out = alsaaudio.PCM(alsaaudio.PCM_PLAYBACK, channels=1, rate=44100, format=alsaaudio.PCM_FORMAT_S16_LE, periodsize=160, device=device)
    # Read data from stdin
    data = f.read(320)
    while data:
        if out.write(data) < 0:
            print("Playback buffer underrun! Continuing nonetheless ...")
        data = f.read(320)
    out.close()