forked from auracaster/pyalsaaudio
72a31c802a
Added isine as an example for interactive generation of sound. git-svn-id: svn://svn.code.sf.net/p/pyalsaaudio/code/trunk@33 ec2f30ec-7544-0410-870e-f70ca00c83f0
80 lines
2.0 KiB
Python
80 lines
2.0 KiB
Python
''' Use this example from an interactive python session, for example:
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>>> from isine import change
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>>> change(880)
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'''
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from threading import Thread
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from Queue import Queue, Empty
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from math import pi, sin
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import struct
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import alsaaudio
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sampling_rate = 44100
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format = alsaaudio.PCM_FORMAT_S16_LE
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framesize = 2 # bytes per frame for the values above
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def digitize(s):
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if s > 1.0 or s < -1.0:
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raise ValueError
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return struct.pack('h', int(s * 32767))
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def generate(frequency):
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# generate a buffer with a sine wave of frequency
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size = int(sampling_rate / frequency)
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buffer = ''
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for i in range(size):
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buffer = buffer + digitize(sin(i/(2 * pi)))
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return buffer
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class SinePlayer(Thread):
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def __init__(self, frequency = 440.0):
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Thread.__init__(self)
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self.setDaemon(True)
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self.device = alsaaudio.PCM()
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self.device.setchannels(1)
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self.device.setformat(format)
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self.device.setrate(sampling_rate)
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self.queue = Queue()
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self.change(frequency)
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def change(self, frequency):
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'''This is called outside of the player thread'''
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# we generate the buffer in the calling thread for less
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# latency when switching frequencies
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# More than 100 writes/s are pushing it - play multiple buffers
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# for higher frequencies
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factor = int(frequency/100.0)
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if factor == 0:
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factor = 1
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buf = generate(frequency) * factor
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print 'factor: %d, frames: %d' % (factor, len(buf) / framesize)
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self.queue.put( buf)
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def run(self):
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buffer = None
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while True:
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try:
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buffer = self.queue.get(False)
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self.device.setperiodsize(len(buffer) / framesize)
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self.device.write(buffer)
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except Empty:
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if buffer:
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self.device.write(buffer)
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isine = SinePlayer()
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isine.start()
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def change(f):
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isine.change(f)
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