Re: [LAU] USB device gives wrong data?

On Mon, Oct 22, 2007 at 10:17:50AM -0700, william estrada wrote:

> Yes, the format is U8, it is a simple recording program to make '.wav'
> files. The filtering does work when adjusting the 'silence byte'. It
> appears that the device drivers are not consistent with this value?
> So I will be adding an option to change the value of the 'silence byte'.
>
> How do I use the RMS value to remove noise? A URL that I could read?

It's probably not worth the effort for 8 bits. What you see is a simple
DC offset. Probably the easy approach is to consider a range of values
e.g. 0x7E...0x82 as silence. Any value outside the range starts the
recording, until you find a long series of samples within the silence
range.

So the algo would be:

  If you find a value in the silence range, increment a counter.
  If the counter reaches a certain value, stop.
  If you find a value outside the range, start and reset the
  counter.

You could also use a counter to avoid too many false starts.

Ciao

-- 
FA
Laboratorio di Acustica ed Elettroacustica
Parma, Italia
Lascia la spina, cogli la rosa.
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