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Import initial set of sources
author Chris Cannam <cannam@all-day-breakfast.com>
date Mon, 18 Mar 2013 14:12:14 +0000
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cannam@85 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
cannam@85 2 <HTML>
cannam@85 3
cannam@85 4 <HEAD>
cannam@85 5 <TITLE>
cannam@85 6 libsndfile and GNU Octave
cannam@85 7 </TITLE>
cannam@85 8 <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)">
cannam@85 9 <LINK REL="stylesheet" HREF="libsndfile.css" TYPE="text/css" MEDIA="all">
cannam@85 10 <LINK REL="stylesheet" HREF="print.css" TYPE="text/css" MEDIA="print">
cannam@85 11 </HEAD>
cannam@85 12
cannam@85 13 <BODY>
cannam@85 14
cannam@85 15 <BR>
cannam@85 16 <H1><B>libsndfile and GNU Octave</B></H1>
cannam@85 17 <P>
cannam@85 18 <A HREF="http://www.octave.org/">GNU Octave</A> is a high-level interactive
cannam@85 19 language for numerical computations.
cannam@85 20 There are currently two development streams, a stable 2.0.X series and a
cannam@85 21 development 2.1.X series.
cannam@85 22 Octave reads and writes data in binary formats that were originally developed
cannam@85 23 for
cannam@85 24 <A HREF="http://www.mathworks.com/">MATLAB</A>.
cannam@85 25 Version 2.0.X of Octave uses binary data files compatible with MATLAB
cannam@85 26 version 4.2 while Octave 2.1.X uses binary data files compatible
cannam@85 27 with MATLAB version 5.0 as well as being able to read the older MATLAB 4.2
cannam@85 28 format.
cannam@85 29 </P>
cannam@85 30 <P>
cannam@85 31 From version 1.0.1 of libsndfile onwards, libsndfile has the ability of reading
cannam@85 32 and writing a small subset of the binary data files used by both versions
cannam@85 33 of GNU Octave.
cannam@85 34 This gives people using GNU Octave for audio based work an easy method of
cannam@85 35 moving audio data between GNU Octave and other programs which use libsndfile.
cannam@85 36 </P>
cannam@85 37 <P>
cannam@85 38 For instance it is now possible to do the following:
cannam@85 39 </P>
cannam@85 40
cannam@85 41 <UL>
cannam@85 42 <LI> Load a WAV file into a sound file editor such as
cannam@85 43 <A HREF="http://www.metadecks.org/software/sweep/">Sweep</A>.
cannam@85 44 <LI> Save it as a MAT4 file.
cannam@85 45 <LI> Load the data into Octave for manipulation.
cannam@85 46 <LI> Save the modified data.
cannam@85 47 <LI> Reload it in Sweep.
cannam@85 48 </UL>
cannam@85 49 <P>
cannam@85 50 Another example would be using the MAT4 or MAT5 file formats as a format which
cannam@85 51 can be easily loaded into Octave for viewing/analyzing as well as a format
cannam@85 52 which can be played with command line players such as the one included with
cannam@85 53 libsndfile.
cannam@85 54 </P>
cannam@85 55
cannam@85 56 <H2><B>Details</B></H2>
cannam@85 57 <P>
cannam@85 58 Octave, like most programming languages, uses variables to store data, and
cannam@85 59 Octave variables can contain both arrays and matrices.
cannam@85 60 It is also able to store one or more of these variables in a file.
cannam@85 61 When reading Octave files, libsndfile expects a file to contain two
cannam@85 62 variables and their associated data.
cannam@85 63 The first variable should contain a variable holding the file sample rate
cannam@85 64 while the second variable contains the audio data.
cannam@85 65 </P>
cannam@85 66 <P>
cannam@85 67 For example, to generate a sine wave and store it as a binary file which
cannam@85 68 is compatible with libsndfile, do the following:
cannam@85 69 </P>
cannam@85 70 <PRE>
cannam@85 71 octave:1 > samplerate = 44100 ;
cannam@85 72 octave:2 > wavedata = sin ((0:1023)*2*pi/1024) ;
cannam@85 73 octave:3 > save sine.mat samplerate wavedata
cannam@85 74 </PRE>
cannam@85 75
cannam@85 76 <P>
cannam@85 77 The process of reading and writing files compatible with libsndfile can be
cannam@85 78 made easier by use of two Octave script files :
cannam@85 79 </P>
cannam@85 80 <PRE>
cannam@85 81 octave:4 > [data fs] = sndfile_load ("sine.mat") ;
cannam@85 82 octave:5 > sndfile_save ("sine2.mat", data, fs) ;
cannam@85 83 </PRE>
cannam@85 84 <P>
cannam@85 85 In addition, libsndfile contains a command line program which which is able
cannam@85 86 to play the correct types of Octave files.
cannam@85 87 Using this command line player <B>sndfile-play</B> and a third Octave script
cannam@85 88 file allows Octave data to be played from within Octave on any of the platforms
cannam@85 89 which <B>sndfile-play</B> supports (at the moment: Linux, MacOS X, Solaris and
cannam@85 90 Win32).
cannam@85 91 </P>
cannam@85 92 <PRE>
cannam@85 93 octave:6 > sndfile_play (data, fs) ;
cannam@85 94 </PRE>
cannam@85 95 <P>
cannam@85 96 These three Octave scripts are installed automatically in Octave's site
cannam@85 97 script directory when libsndfile is installed (except on Win32) ie when
cannam@85 98 libsndfile is being installed into /usr/local, the Octave scripts will
cannam@85 99 be installed in /usr/local/share/octave/site/m/.
cannam@85 100 </P>
cannam@85 101
cannam@85 102 <P>
cannam@85 103 There are some other Octave scripts for audio to be found
cannam@85 104 <A HREF="http://octave.sourceforge.net/index/audio.html">here</A>.
cannam@85 105 </P>
cannam@85 106
cannam@85 107 <BR>
cannam@85 108 <!-- ========================================================================= -->
cannam@85 109
cannam@85 110 <HR>
cannam@85 111 <P>
cannam@85 112 The libsndfile home page is here :
cannam@85 113 <A HREF="http://www.mega-nerd.com/libsndfile/">
cannam@85 114 http://www.mega-nerd.com/libsndfile/</A>.
cannam@85 115 </P>
cannam@85 116
cannam@85 117 </BODY>
cannam@85 118 </HTML>