pcm1.rar_PCM matlab_matlab pcm_modulation_pcm抽样_信源pcm编码

% 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 count % 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