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

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 = |
              | sgnm
              | ------ 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 sgnx for sgnm;
        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
     
     
see also:
itu-t standard nonuniform quantising logarithmic compression u-law quantising errors 

A-Law >> A Words
A-Law, definition of term: A-Law
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