Alaw

1 definition found

From The Free On-line Dictionary of Computing (27 SEP 03) [foldoc]:

  A-law
       
           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)