Author: cn.wei.hp

PCM_Testing.m

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+% 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