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''' Use this example from an interactive python session, for example:
>>> from isine import change
>>> change(880)
'''
from threading import Thread
from Queue import Queue, Empty
from math import pi, sin
import struct
import alsaaudio
sampling_rate = 44100
format = alsaaudio.PCM_FORMAT_S16_LE
framesize = 2 # bytes per frame for the values above
def digitize(s):
if s > 1.0 or s < -1.0:
raise ValueError
return struct.pack('h', int(s * 32767))
def generate(frequency):
# generate a buffer with a sine wave of frequency
size = int(sampling_rate / frequency)
buffer = ''
for i in range(size):
buffer = buffer + digitize(sin(i/(2 * pi)))
return buffer
class SinePlayer(Thread):
def __init__(self, frequency = 440.0):
Thread.__init__(self)
self.setDaemon(True)
self.device = alsaaudio.PCM()
self.device.setchannels(1)
self.device.setformat(format)
self.device.setrate(sampling_rate)
self.queue = Queue()
self.change(frequency)
def change(self, frequency):
'''This is called outside of the player thread'''
# we generate the buffer in the calling thread for less
# latency when switching frequencies
# More than 100 writes/s are pushing it - play multiple buffers
# for higher frequencies
factor = int(frequency/100.0)
if factor == 0:
factor = 1
buf = generate(frequency) * factor
print 'factor: %d, frames: %d' % (factor, len(buf) / framesize)
self.queue.put( buf)
def run(self):
buffer = None
while True:
try:
buffer = self.queue.get(False)
self.device.setperiodsize(len(buffer) / framesize)
self.device.write(buffer)
except Empty:
if buffer:
self.device.write(buffer)
isine = SinePlayer()
isine.start()
def change(f):
isine.change(f)
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