Re: [LAU] [alsa-devel] USB device gives wrong data? - Linux-audio-user

25 Oct 2007

Now that is helpfull.  Thanks, I will try it when I get a chance.

Thanks Gordon.

William Estrada
MrUmunhum(a)popdial.com
Mt-Umunhum-Wireless.net ( http://Mt-Umunhum-Wireless.net )
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...
  Message: 1
 Date: Wed, 24 Oct 2007 11:05:35 +0100
 From: Gordon JC Pearce &lt;gordonjcp(a)gjcp.net&gt;
 Subject: Re: [LAU] [alsa-devel] USB device gives wrong data?
 To: linux-audio-user(a)lists.linuxaudio.org
 Message-ID: &lt;200710241105.35908.gordonjcp(a)gjcp.net&gt;
 Content-Type: text/plain;  charset="iso-8859-1"

 On Tuesday 23 October 2007 00:05:13 James Cameron wrote:

   How would
you filter out noise?  You can filter out DC offset by measuring the offset you
have, and
 subtracting this measurement from your samples.  
 A better way would be to use a highpass filter.

 Use something like:

 for (i=0; i<=NUM_SAMPLES; i++) {
   hp_last = 0.9999f * hp_last + in[i] - hp_last_in;
   hp_last_in = in[i];
   out[i] = hp_last;
 }

 You could optimise that a bit.

 Gordon