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- libsndfile and GNU Octave
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- <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)">
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-<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>
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-<P>
- The libsndfile home page is here :
- <A HREF="http://www.mega-nerd.com/libsndfile/">
- http://www.mega-nerd.com/libsndfile/</A>.
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