File: mu2lin.sci

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function [y]=mu2lin(mu)
//Utility fct: converts mu-law encoding to linear signal.
//   y=mu2lin(mu) converts mu-law encoded 8-bit audio signals,
//   stored in the range 0 <= mu <= 255, to
//   linear signal amplitude in the range -s < y < s where
//   s = 32124/32768 ~= .9803.  The input mu is often obtained 
//   using mget(...,'uc') to read byte-encoded audio files.
//  Translation of C program by:
//  Craig Reese: IDA/Supercomputing Research Center
//  Joe Campbell: Department of Defense
//  29 September 1989
  SCALE = 1/32768;
  ETAB = [0,132,396,924,1980,4092,8316,16764];
  mu = 255-mu;
  sig = mu>127;
  e = fix(mu/16)-8*bool2s(sig)+1;
  f = mu-fix(mu./16).*16;
  y = f.*2.^(e+2);
  e(:) = ETAB(e);
  y = SCALE*(1-2*bool2s(sig)) .* (e+y);
endfunction