[linux-audio-dev] scaling audio signal

Hi People, On trying to deal with wave files in python, I came across this article: http://209.85.165.104/search?q=cache:vMIuboZw0BwJ:scipy.mit.edu/tutorials/w… the original pdf http://scipy.mit.edu/tutorials/wave.pdf is not available... The signal scaling is just beyond my understandings, and I can´t find any explanation on the web about it. What is the role of that in the programm? Anyway, I will write here what it does to the audio signal that I don´t understand. By catching code lines in functions it looks like this: '''' mono signal, a list, say a 200Hz sinusoid with 2 seconds): signal=[math.sin(2*math.pi*200*(x/44100.0)) for x in range(88200)] ''' tmp = list( signal ) min_tmp = min(tmp) max_tmp = max(tmp) scalar = (2**16 - 1.0) / (1.0 * (max_tmp - min_tmp)) * volume #for 16 bit, it could be 8 or 32 tmp = map( lambda x: int(scalar*(x-min_tmp)), tmp) signal = tmp if samp_width != 1: signal = map( lambda x: x - 2**(samp_width*8 - 1), signal ) #and then they pack the code, conv_code is 'B' for 8 bit, 'h' for 16 bit, 'i' for 32 bit: f.writeframes( struct.pack( conv_code, signal[i] ) ) Ok. This struct thing I don´t fully understand, but I already know it has to do with C data strings. But the previous part simply doesn´t make sense, and I can´t find any reference to this things on the web. I would really appreciate if anyone could explain me what is happening and/or point me some writings about that. One disturbuing thing about using this script is that sometimes it outputs a wave file with start and end out of center (zero amplitude), even when the singal list had fadings. It seems that it has to do with signals that goes beyond the [-1,1] closed interval, but I don´t know why. thanks guys, Claire