From help-octave-request at bevo dot che dot wisc dot edu Tue Dec 11 10:10:34 2001
Subject: Re: audio problems
From: Paul Kienzle <pkienzle at jazz dot ncnr dot nist dot gov>
To: Matthew Flax <flatmax at cse dot unsw dot edu dot au>,    Drew Krause <drkrause@mindspring.com>
Cc: help-octave at bevo dot che dot wisc dot edu
Date: Tue, 11 Dec 2001 11:10:22 -0500

When you are downsampling, you will want to low-pass filter
your input first.  E.g., to downsample by a factor of q
  [b, a] = cheby1(n, 0.05, 1/q);
  y = filter(b,a,x);
  y = y(1:q:length(x));
The function cheby1 is available from octave-forge at octave.sf.net

Also, /dev/dsp may be expecting mulaw encoded data.
In that case you will need to do playaudio(lin2mu(y)).

Paul Kienzle
pkienzle at users dot sf dot net

On Tue, Dec 11, 2001 at 06:50:55PM +1100, Matthew Flax wrote:
> Hi there,
> 
> I am just writing to let you know that the audio output is alwayse  at  8 
> bit, 8 KHz
> The way to use this is to make sure your signal (x) is :
> %# scale x to max 8 bit levels
> x=x/max(x)*128;
> %# resample x to the correct sampling freq.
> fs=44100
> playaudio(x(1:(fs/x):length(x)))
> 
> that should work I believe
> -- 
> Matt
> 
> For electronic musicians ...
> Vector Bass          : http://mffmvectorbass.sourceforge.net/
> For developers ...
> TimeScale Audio Mod  : http://mffmtimescale.sourceforge.net/
> Multimedia Time Code : http://mffmtimecode.sourceforge.net/
> 3D Audio Library     : http://mffm3daudiolib.sourceforge.net/
> 
> 
> 
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> 
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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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