wavio 0.0.9

Examples

The following examples are also found in the docstring of wavio.write.

Create a 3 second 440 Hz sine wave, and save it in a 24-bit WAV file.

>>> import numpy as np
>>> import wavio

>>> rate = 22050           # samples per second
>>> T = 3                  # sample duration (seconds)
>>> n = int(rate*T)        # number of samples
>>> t = np.arange(n)/rate  # grid of time values

>>> f = 440.0              # sound frequency (Hz)
>>> x = np.sin(2*np.pi * f * t)

x is a single sine wave with amplitude 1, so we can use the default scale.

>>> wavio.write("sine24.wav", x, rate, sampwidth=3)

Create a file that contains the 16 bit integer values -10000 and 10000 repeated 100 times. Use a sample rate of 8000.

>>> x = np.empty(200, dtype=np.int16)
>>> x[::2] = -10000
>>> x[1::2] = 10000
>>> wavio.write("foo.wav", x, 8000)

Check that the file contains what we expect. The values are checked for exact equality. The input was an integer array, so the values are not scaled.

>>> w = wavio.read("foo.wav")
>>> np.all(w.data[:, 0] == x)
True

Write floating point data to a 16 bit WAV file. The floating point values are assumed to be within the range [-2, 2], and we want the values 2 and -2 to correspond to the full output range, even if the actual values in the data do not fill this range. We do that by specifying scale=2.

T, rate and t are from above. The data is the sum of two sinusoids, with frequencies 440 and 880 Hz, modulated by a parabolic curve that is zero at the start and end of the data.

>>> envelope = (4/T**2)*(t * (T - t))
>>> omega1 = 2*np.pi*440
>>> omega2 = 2*np.pi*880
>>> y = envelope*(np.sin(omega1*t) + 0.3*np.sin(omega2*t + 0.2))
>>> y.min(), y.max()
(-1.1745469775555515, 1.093833464065767)

Write the WAV file, with scale=2.

>>> wavio.write('harmonic.wav', y, rate, sampwidth=2, scale=2)

Check the minimum and maximum integers that were actually written to the file:

>>> w = wavio.read("harmonic.wav")
>>> w.data.min(), w.data.max()
(-19243, 17921)

If we want the WAV file to use as much of the range of the output integer type as possible (while still mapping 0.0 in the input to 0 in the output), we set scale=”auto”.

>>> wavio.write('harmonic_full.wav', y, rate, sampwidth=2, scale="auto")

>>> w = wavio.read('harmonic_full.wav')
>>> w.data.min(), w.data.max()
(-32768, 30517)

Author: Warren Weckesser

Repository: https://github.com/WarrenWeckesser/wavio

License: BSD 2-clause (http://opensource.org/licenses/BSD-2-Clause)