The following example shows how to read in a wav file. Reading and Writing Wav Files Using GNU Octave. GNU Octave is a free and open source version of Matlab.

Previous:, Up: [][] 33.5 Audio Data Processing Octave provides a few functions for dealing with audio data. An audio ‘sample’ is a single output value from an A/D converter, i.e., a small integer number (usually 8 or 16 bits), and audio data is just a series of such samples. It can be characterized by three parameters: the sampling rate (measured in samples per second or Hz, e.g., 8000 or 44100), the number of bits per sample (e.g., 8 or 16), and the number of channels (1 for mono, 2 for stereo, etc.). There are many different formats for representing such data. Currently, only the two most popular, linear encoding and mu-law encoding, are supported by Octave. There is an excellent FAQ on audio formats by Guido van Rossum which can be found at any FAQ ftp site, in particular in the directory /pub/usenet/news.answers/audio-fmts of the archive site rtfm.mit.edu.

Octave simply treats audio data as vectors of samples (non-mono data are not supported yet). It is assumed that audio files using linear encoding have one of the extensions lin or raw, and that files holding data in mu-law encoding end in au, mu, or snd.

Function File: lin2mu ( x, n) Convert audio data from linear to mu-law. Mu-law values use 8-bit unsigned integers. Linear values use n-bit signed integers or floating point values in the range -1 ≤ x ≤ 1 if n is 0.

If n is not specified it defaults to 0, 8, or 16 depending on the range of values in x. Function File: mu2lin ( x, n) Convert audio data from mu-law to linear. Mu-law values are 8-bit unsigned integers. Linear values use n-bit signed integers or floating point values in the range -1≤y≤1 if n is 0. Information Systems College Programs.