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#!/usr/bin/env python3
# -*- mode: python; indent-tabs-mode: t; c-basic-offset: 4; tab-width: 4 -*-
## recordtest.py
##
## This is an example of a simple sound capture script.
##
## The script opens an ALSA pcm device for sound capture, sets
## various attributes of the capture, and reads in a loop,
## writing the data to standard out.
##
## To test it out do the following:
## python recordtest.py out.raw # talk to the microphone
## aplay -r 8000 -f S16_LE -c 1 out.raw
#!/usr/bin/env python
from __future__ import print_function
import sys
import time
import getopt
import alsaaudio
def usage():
print('usage: recordtest.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], 'wb')
# Open the device in nonblocking capture mode in mono, with a sampling rate of 44100 Hz
# and 16 bit little endian samples
# The period size controls the internal number of frames per period.
# The significance of this parameter is documented in the ALSA api.
# For our purposes, it is suficcient to know that reads from the device
# will return this many frames. Each frame being 2 bytes long.
# This means that the reads below will return either 320 bytes of data
# or 0 bytes of data. The latter is possible because we are in nonblocking
# mode.
inp = alsaaudio.PCM(alsaaudio.PCM_CAPTURE, alsaaudio.PCM_NONBLOCK,
channels=1, rate=44100, format=alsaaudio.PCM_FORMAT_S16_LE,
periodsize=160, device=device)
loops = 1000000
while loops > 0:
loops -= 1
# Read data from device
l, data = inp.read()
if l:
f.write(data)
time.sleep(.001)
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