mirror of
https://gitee.com/openharmony/third_party_libsnd
synced 2024-11-27 12:00:51 +00:00
118 lines
3.9 KiB
HTML
118 lines
3.9 KiB
HTML
<!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">
|
|
</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, MacOSX, 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>
|