interpretor/libsndfile-1.0.25/doc/octave.html

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   6         libsndfile and GNU Octave
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   8         <META NAME="Author"      CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)">
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  16 <H1><B>libsndfile and GNU Octave</B></H1>
  17 <P>
  18         <A HREF="http://www.octave.org/">GNU Octave</A> is a high-level interactive
  19         language for numerical computations.
  20         There are currently two development streams, a stable 2.0.X series and a
  21         development 2.1.X series.
  22         Octave reads and writes data in binary formats that were originally developed
  23         for
  24                 <A HREF="http://www.mathworks.com/">MATLAB</A>.
  25         Version 2.0.X of Octave uses binary data files compatible with MATLAB
  26         version 4.2 while Octave 2.1.X uses binary data files compatible
  27         with MATLAB version 5.0 as well as being able to read the older MATLAB 4.2
  28         format.
  29 </P>
  30 <P>
  31         From version 1.0.1 of libsndfile onwards, libsndfile has the ability of reading
  32         and writing a small subset of the binary data files used by both versions
  33         of GNU Octave.
  34         This gives people using GNU Octave for audio based work an easy method of
  35         moving audio data between GNU Octave and other programs which use libsndfile.
  36 </P>
  37 <P>
  38         For instance it is now possible to do the following:
  39 </P>
  40
  41         <UL>
  42         <LI> Load a WAV file into a sound file editor such as
  43                 <A HREF="http://www.metadecks.org/software/sweep/">Sweep</A>.
  44         <LI> Save it as a MAT4 file.
  45         <LI> Load the data into Octave for manipulation.
  46         <LI> Save the modified data.
  47         <LI> Reload it in Sweep.
  48         </UL>
  49 <P>
  50         Another example would be using the MAT4 or MAT5 file formats as a format which
  51         can be easily loaded into Octave for viewing/analyzing as well as a format
  52         which can be played with command line players such as the one included with
  53         libsndfile.
  54 </P>
  55
  56 <H2><B>Details</B></H2>
  57 <P>
  58         Octave, like most programming languages, uses variables to store data, and
  59         Octave variables can contain both arrays and matrices.
  60         It is also able to store one or more of these variables in a file.
  61         When reading Octave files, libsndfile expects a file to contain two
  62         variables and their associated data.
  63         The first variable should contain a variable holding the file sample rate
  64         while the second variable contains the audio data.
  65 </P>
  66 <P>
  67         For example, to generate a sine wave and store it as a binary file which
  68         is compatible with libsndfile, do the following:
  69 </P>
  70 <PRE>
  71         octave:1 > samplerate = 44100 ;
  72         octave:2 > wavedata = sin ((0:1023)*2*pi/1024) ;
  73         octave:3 > save sine.mat samplerate wavedata
  74 </PRE>
  75
  76 <P>
  77         The process of reading and writing files compatible with libsndfile can be
  78         made easier by use of two Octave script files :
  79 </P>
  80 <PRE>
  81         octave:4 > [data fs] = sndfile_load ("sine.mat") ;
  82         octave:5 > sndfile_save ("sine2.mat", data, fs) ;
  83 </PRE>
  84 <P>
  85         In addition, libsndfile contains a command line program which which is able
  86         to play the correct types of Octave files.
  87         Using this command line player <B>sndfile-play</B> and a third Octave script
  88         file allows Octave data to be played from within Octave on any of the platforms
  89         which <B>sndfile-play</B> supports (at the moment: Linux, MacOS X, Solaris and
  90         Win32).
  91 </P>
  92 <PRE>
  93         octave:6 > sndfile_play (data, fs) ;
  94 </PRE>
  95 <P>
  96         These three Octave scripts are installed automatically in Octave's site
  97         script directory when libsndfile is installed (except on Win32) ie when
  98         libsndfile is being installed into /usr/local, the Octave scripts will
  99         be installed in /usr/local/share/octave/site/m/.
 100 </P>
 101
 102 <P>
 103         There are some other Octave scripts for audio to be found
 104                 <A HREF="http://octave.sourceforge.net/index/audio.html">here</A>.
 105 </P>
 106
 107 <BR>
 108 <!-- ========================================================================= -->
 109
 110 <HR>
 111 <P>
 112         The libsndfile home page is here :
 113                 <A HREF="http://www.mega-nerd.com/libsndfile/">
 114                         http://www.mega-nerd.com/libsndfile/</A>.
 115 </P>
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