a-law

1 definition found

a-law - Free On-line Dictionary of Computing (26 May 2007) :

  A-law
  
     <standard> The ITU-T standard for nonuniform quantising logarithmic compression
     .
  
     The equation for A-law is
  
           |    A
           | ------- (m/mp)                   |m/mp| =< 1/A
           | 1+ln A
       y = |
           | sgn(m)
           | ------ (1 + ln A|m/mp|)   1/A =< |m/mp| =< 1
           | 1+ln A
  
     Values of u=100 and 255, A=87.6, mp is the Peak message value,
     m is the current quantised message value.  (The formulae get
     simpler if you substitute x for m/mp and sgn(x) for sgn(m);
     then -1 <= x <= 1.)
  
     Converting from u-LAW to A-LAW introduces quantising errors
     .  u-law is used in North America and Japan, and A-law
     is used in Europe and the rest of the world and international
     routes.
  
     [The Audio File Formats FAQ]
  
     (1995-02-21)