| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
| <HTML> |
| |
| <HEAD> |
| <TITLE> |
| libsndfile and GNU Octave |
| </TITLE> |
| <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)"> |
| <LINK REL="stylesheet" HREF="libsndfile.css" TYPE="text/css" MEDIA="all"> |
| <LINK REL="stylesheet" HREF="print.css" TYPE="text/css" MEDIA="print"> |
| </HEAD> |
| |
| <BODY> |
| |
| <BR> |
| <H1><B>libsndfile and GNU Octave</B></H1> |
| <P> |
| <A HREF="http://www.octave.org/">GNU Octave</A> is a high-level interactive |
| language for numerical computations. |
| There are currently two development streams, a stable 2.0.X series and a |
| development 2.1.X series. |
| Octave reads and writes data in binary formats that were originally developed |
| for |
| <A HREF="http://www.mathworks.com/">MATLAB</A>. |
| Version 2.0.X of Octave uses binary data files compatible with MATLAB |
| version 4.2 while Octave 2.1.X uses binary data files compatible |
| with MATLAB version 5.0 as well as being able to read the older MATLAB 4.2 |
| format. |
| </P> |
| <P> |
| From version 1.0.1 of libsndfile onwards, libsndfile has the ability of reading |
| and writing a small subset of the binary data files used by both versions |
| of GNU Octave. |
| This gives people using GNU Octave for audio based work an easy method of |
| moving audio data between GNU Octave and other programs which use libsndfile. |
| </P> |
| <P> |
| For instance it is now possible to do the following: |
| </P> |
| |
| <UL> |
| <LI> Load a WAV file into a sound file editor such as |
| <A HREF="http://www.metadecks.org/software/sweep/">Sweep</A>. |
| <LI> Save it as a MAT4 file. |
| <LI> Load the data into Octave for manipulation. |
| <LI> Save the modified data. |
| <LI> Reload it in Sweep. |
| </UL> |
| <P> |
| Another example would be using the MAT4 or MAT5 file formats as a format which |
| can be easily loaded into Octave for viewing/analyzing as well as a format |
| which can be played with command line players such as the one included with |
| libsndfile. |
| </P> |
| |
| <H2><B>Details</B></H2> |
| <P> |
| Octave, like most programming languages, uses variables to store data, and |
| Octave variables can contain both arrays and matrices. |
| It is also able to store one or more of these variables in a file. |
| When reading Octave files, libsndfile expects a file to contain two |
| variables and their associated data. |
| The first variable should contain a variable holding the file sample rate |
| while the second variable contains the audio data. |
| </P> |
| <P> |
| For example, to generate a sine wave and store it as a binary file which |
| is compatible with libsndfile, do the following: |
| </P> |
| <PRE> |
| octave:1 > samplerate = 44100 ; |
| octave:2 > wavedata = sin ((0:1023)*2*pi/1024) ; |
| octave:3 > save sine.mat samplerate wavedata |
| </PRE> |
| |
| <P> |
| The process of reading and writing files compatible with libsndfile can be |
| made easier by use of two Octave script files : |
| </P> |
| <PRE> |
| octave:4 > [data fs] = sndfile_load ("sine.mat") ; |
| octave:5 > sndfile_save ("sine2.mat", data, fs) ; |
| </PRE> |
| <P> |
| In addition, libsndfile contains a command line program which which is able |
| to play the correct types of Octave files. |
| Using this command line player <B>sndfile-play</B> and a third Octave script |
| file allows Octave data to be played from within Octave on any of the platforms |
| which <B>sndfile-play</B> supports (at the moment: Linux, MacOS X, Solaris and |
| Win32). |
| </P> |
| <PRE> |
| octave:6 > sndfile_play (data, fs) ; |
| </PRE> |
| <P> |
| These three Octave scripts are installed automatically in Octave's site |
| script directory when libsndfile is installed (except on Win32) ie when |
| libsndfile is being installed into /usr/local, the Octave scripts will |
| be installed in /usr/local/share/octave/site/m/. |
| </P> |
| |
| <P> |
| There are some other Octave scripts for audio to be found |
| <A HREF="http://octave.sourceforge.net/index/audio.html">here</A>. |
| </P> |
| |
| <BR> |
| <!-- ========================================================================= --> |
| |
| <HR> |
| <P> |
| The libsndfile home page is here : |
| <A HREF="http://www.mega-nerd.com/libsndfile/"> |
| http://www.mega-nerd.com/libsndfile/</A>. |
| </P> |
| |
| </BODY> |
| </HTML> |