Waveform Quantization and Compression - Digital Signal Processing: Fundamentals and Applications - page 536

% rvalue ¼ output value from the mu-law expander
%

y ¼ y/vmax; % Normalization
% mu-law expanding
rvalue ¼ sign(y)*(vmax/mu)*((1 þ mu)^abs(y) -1);
Program 11.5. MATLAB function for midread quantizer encoding.

function [indx, pq ] ¼ mtrdenc(NoBits,Xmax,value)

% function pq mtrdenc(NoBits, Xmax, value)

% This routine is created for simulation of midtread uniform quantizer.
%
% NoBits: number of bits used in quantization.
% Xmax: overload value.
% value: input to be quantized.
% pq: output of quantized value
% indx: integer index
%
% Note: the midtread method is used in this quantizer.
%

¼

if NoBits ¼¼ 0
pq ¼ 0;
indx ¼ 0;
else
delta ¼ 2*abs(Xmax)/(2^NoBits-1);
Xrmax ¼ delta*(2^NoBits/2-1);
if abs(value) > ¼ Xrmax

tmp ¼ Xrmax;

else
tmp

¼ abs(value);

end
indx

¼ round(tmp/delta);

indx*delta;
if value < 0
pq ¼ -pq;
indx ¼ -indx;
end
end
Program 11.6. MATLAB function for midtread quantizer decoding.

pq ¼

function pq ¼ mtrddec(NoBits,Xmax,indx)
% function pq ¼ mtrddec(NoBits, Xmax, value)
% This routine is the dequantizer.
%
% NoBits: number of bits used in quantization.
% Xmax: overload value.
% pq: output of quantized value
% indx: integer index
%