Date   : Wed, 19 May 2004 03:41:00 -0700 (PDT)
From   : Charles Ripperton <charlesripperton@...>
Subject: Sound wave representation

Hi Beeb fans,

I've got some queries about BBC Micro sound / playing samples.
My understanding is that the SN76489 is capable of 4-bit sound
sample playback, and that the nybbles used are unsigned. In
other terms, the value 15 means the highest positive wave
amplitude, the value 0 means the lowest negative wave amplitude
and somewhere between the values 8 and 7 is the
'zero displacement'. 

Is this accurate? If I'm incorrect, then please explain what
the true situation is. Cheers.

Charles.



===================================================================
SEE THAT BELOW THERE IS NO ABSOLUTE WAY TO PINPOINT A ZERO-CROSSING.
THE CLOSEST ONE GETS TO IT IS BY USING '7' OR '8'.
===================================================================

 15 (Maximum volume on 'positive' side of wave)
 
 .
 .
 .

 9           *
 
 
        
 8     *           *
   
   
 7                   *           *
 
  
 
 6                         *
 
 .
 . 
 . 
 
 0 (Maximum volume on 'negative' side of wave)


--



       
               
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