From help-request at octave dot org Thu Dec 23 03:53:36 2004
Subject: Re: Audio i/o
From: edA-qa mort-ora-y <eda-qa at disemia dot com>
To: Jose Colmenares <jbcolmena at yahoo dot es>
CC: help at octave dot org
Date: Thu, 23 Dec 2004 10:55:03 +0100

Jose Colmenares wrote:
> I want to play, using my soundcard, a certain signal.
> I could generate the signal, and play it using the
> playsound command. Nevertheless, how do I put the
> vector in the correcto format? I've searched the web,

Do you need to play them from directly within Octave? If not, then here 
is a solution.  If yes, then well, use the same advice and simply call 
the "system" function. ;)

If you are generating waveforms it is probably fairly convenient for you 
to use floating point samples.  These samples should be in the range 
[-1,1] as that is what a typical sound-card, and the playing system are 
expecting.  Your vector is a normal Octave vector (one-row) in time 
offset order t(1) is first sample, t(2) is second, ...

Once you have a vector you need to write it to a file.  You can do this 
with a command like:
	fwrite( handle, data, "float" )
The "float" instructs it to write in the float format, which should be 
32-bit floating point.

Now, for Linux:
Once you have a file you can play it using the program "sox" and 
"esdcat".  esdcat is installed on most new Linux installs, sox may need 
to be additionally installed.  RUn this command:
	sox -t raw -l -f -r 44100 filename -c 1 -s -w -t raw - | esdcat -r 44100 -m
This converts your RAW file forward into something esdcat can use, and 
then it plays it.  Replace 44100 with the appropriate byte rate.  The 
docs on sox/esdcat explain the rest of the options.

Now, for Windows:
Well, from the command line I don't know what to do, but maybe esdcat is 
also ported... otherwise open your file in something like CoolEdit and 
let it play it.



-- 
edA-qa mort-ora-y
Idea Architect
http://disemia.com/



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