Signal Sampling and Quantization - Digital Signal Processing: Fundamentals and Applications - page 46

disp( ' 20*log10(k) ¼ > ' );
k ¼ 20*log10(k)
bits ¼ input( ' input number of bits ¼ > ' );
lg ¼ length(sig);
for x ¼ 1:lg
[Index(x) pq] ¼ biquant(bits, -5,5, sig(x)); % Output quantized index
end
% transmitted
% received
for x

1:lg
qsig(x)

¼

¼ biqtdec(bits, -5,5, Index(x)); % Recover the quantized value

end
qerr ¼ sig-qsig; % Calculate the quantized error

subplot(3,1,1);plot(t,sig);
ylabel( ' Original speech ' );title( ' we.dat: we ' );
subplot(3,1,2);stairs(t, qsig);grid
ylabel( ' Quantized speech ' )
subplot(3,1,3);stairs(t, qerr);grid
ylabel( ' Quantized error ' )
xlabel( ' Time (sec.) ' );axis([0 0.25 -1 1]);
disp( ' signal to noise ratio due to quantization noise ' )
snr(sig,qsig); % Signal to ratio in dB:

sig ¼ original signal vector,

% qsig ¼ quantized signal vector

we.dat: we

5

0

-5

0 0.05 0.1 0.15 0.2 0.25

5

0

-5

0 0.05 0.1 0.15 0.2 0.25

1

0

-1

0 0.05 0.1 0.15 0.2 0.25

Time (s ec . )

FIGURE 2.34
Original speech, quantized speech using the 4-bit bipolar quantizer, and quantization error.