1--- 2layout: page 3--- 4 5# libsndfile and GNU Octave 6 7[GNU Octave](http://www.octave.org/) is a high-level interactive language for 8numerical computations. There are currently two development streams, a stable 92.0.X series and a development 2.1.X series. Octave reads and writes data in 10binary formats that were originally developed for 11[MATLAB](http://www.mathworks.com/). Version 2.0.X of Octave uses binary data 12files compatible with MATLAB version 4.2 while Octave 2.1.X uses binary data 13files compatible with MATLAB version 5.0 as well as being able to read the older 14MATLAB 4.2 format. 15 16From version 1.0.1 of libsndfile onwards, libsndfile has the ability of reading 17and writing a small subset of the binary data files used by both versions of GNU 18Octave. This gives people using GNU Octave for audio based work an easy method 19of moving audio data between GNU Octave and other programs which use libsndfile. 20 21For instance it is now possible to do the following: 22 23* Load a WAV file into a sound file editor such as 24 [Sweep](http://www.metadecks.org/software/sweep/). 25* Save it as a MAT4 file. 26* Load the data into Octave for manipulation. 27* Save the modified data. 28* Reload it in Sweep. 29 30Another example would be using the MAT4 or MAT5 file formats as a format which 31can be easily loaded into Octave for viewing/analyzing as well as a format which 32can be played with command line players such as the one included with 33libsndfile. 34 35## Details 36 37Octave, like most programming languages, uses variables to store data, and 38Octave variables can contain both arrays and matrices. It is also able to store 39one or more of these variables in a file. When reading Octave files, libsndfile 40expects a file to contain two variables and their associated data. The first 41variable should contain a variable holding the file sample rate while the second 42variable contains the audio data. 43 44For example, to generate a sine wave and store it as a binary file which is 45compatible with libsndfile, do the following: 46 47 octave:1 > samplerate = 44100 ; 48 octave:2 > wavedata = sin ((0:1023)*2*pi/1024) ; 49 octave:3 > save sine.mat samplerate wavedata 50 51The process of reading and writing files compatible with libsndfile can be made 52easier by use of two Octave script files: 53 54 octave:4 > [data fs] = sndfile_load ("sine.mat") ; 55 octave:5 > sndfile_save ("sine2.mat", data, fs) ; 56 57In addition, libsndfile contains a command line program which which is able to 58play the correct types of Octave files. Using this command line player 59**sndfile-play** and a third Octave script file allows Octave data to be played 60from within Octave on any of the platforms which **sndfile-play** supports (at 61the moment: Linux, MacOS X, Solaris and Win32). 62 63 octave:6 > sndfile_play (data, fs) ; 64 65These three Octave scripts are installed automatically in Octave's site script 66directory when libsndfile is installed (except on Win32) ie when libsndfile is 67being installed into /usr/local, the Octave scripts will be installed in 68/usr/local/share/octave/site/m/. 69 70There are some other Octave scripts for audio to be found 71[here](http://octave.sourceforge.net/audio/index.html). 72