from pylab import *

def sgn(v):
    if v >= 0:
        return 1
    else:
        return -1

def ff(x):
    "Forward mu-law"
    return sgn(x) * log(1 + 255 * abs(x)) / log(256)

figure(figsize = (9, 9))

X = arange(0, 1.002, .002)
ORIG = [x * sin(12 * pi * x) for x in X]
MULAW = [ff(y) for y in ORIG]

subplot(211)
plot(X, ORIG)
title ("Original signal")
axis((0, 1, -1, 1))
grid()

subplot(212)
plot(X, MULAW)
title ("Compressed signal (μ-law)")
axis((0, 1, -1, 1))
grid()

savefig("mu-law-demo.svg")

show()