www.pudn.com > PcmTesting.rar > PCM_Testing.m

% Removing all variables, functions, and MEX-files from memory, leaving the 
% workspace empty. 
clear all 
 
 
% Deleting all figures whose handles are not hidden. 
close all 
 
 
% Deleting all figures including those with hidden handles. 
close all hidden 
 
 
% Clearing all input and output from the Command Window display giving us a clean screen. 
clc 
 
 
% Opening the file 'TEOTH.mp3' in the read access mode. 
fid = fopen ('TEOTH.mp3','r'); 
 
 
% Generating the input signal 'm(t)' by reading the binary data in 16 bit 
% integer format from the specified file and writing it into a matrix 
% 'm(t)'. 
m = fread (fid,'int16'); 
 
 
% Defining the count for efficiency. 
count = 8500; 
 
 
% Calculating maximum value of the input signal 'm(t)'. 
Mp = max (m) 
 
 
% Setting number of bits in a symbol. 
bits = 8; 
 
 
% Defining the number of levels of uniform quantization. 
levels = 2^bits; 
 
 
% Calculating the step size of the quantization. 
step_size = (2*Mp)/levels 
 
 
% Setting the sampling frequency. 
% because the audio signal has a maximum frequency of 4K and according to 
% Nyquist criteria, we get the following sampling frequency. 
Fs = 8000; 
 
 
% Setting the sampling instant. 
Ts = 1; 
 
 
% Setting the number of samples to be used. 
No_Samples = (2*Fs)+Ts; 
 
 
% Define the time vector for the calculations. 
time = [1:Fs/64]; 
 
 
% Calculating the bit rate. 
bit_rate = 8000*bits; 
 
 
% Quantizing the input signal 'm(t)'. 
for k = 1:No_Samples, 
    samp_in(k) = m(k*Ts); 
    quant_in(k) = samp_in(k)/step_size; 
    error(k) = (samp_in(k) - quant_in(k))/No_Samples; 
end 
 
 
% Indicating the sign of the input signal 'm(t)' and calculating the 
% quantized signal 'quant_out'. 
signS = sign (m); 
quant_out = quant_in; 
for i = 1:count, 
    S(i) = abs (quant_in(i)) + 0.5; 
    quant_out(i) = signS(i)*round(S(i))*step_size; 
end 
 
 
% Calculating the quantization noise 'Nq'. 
Nq = ((Mp)^2)/(3*((levels)^2)) 
 
 
% Calculating signal to noise ratio 'SNR'. 
SNR = 1.5*((levels)^2) 
Gms = log10(SNR) 
 
 
% Plotting the input signal 'm(t)'. 
%figure; 
subplot(4,1,1); 
plot(time,m(time)); 
title('Message Signal'); 
xlabel('Time'); 
ylabel('m(t)'); 
grid on; 
 
 
% Plotting the quantized signal 'quant_in(t)'. 
%figure; 
subplot(4,1,2); 
stem(time,quant_in(time),'r'); 
title('Quantized Speech Signal'); 
xlabel('Time'); 
ylabel('Levels'); 
grid on; 
 
 
% Plotting the PCM signal 's_out(t)'. 
%figure; 
subplot(4,1,3); 
plot(time,quant_out(time)); 
title('PCM Speech Signal'); 
xlabel('Time'); 
ylabel('PC Signal'); 
grid on; 
 
 
% Plotting the error signal 'error(t)'. 
subplot(4,1,4); 
plot(time,error(time)); 
title('Error Signal'); 
xlabel('Time'); 
ylabel('Error(t)'); 
grid on; 
 
 
% Removing all variables, functions, and MEX-files from memory, leaving the 
% workspace empty. 
clear all