demo.m

% DEMO Demonstrates the use of framing and synthesis routines.
%
%   See also VEC2FRAMES, FRAMES2VEC

%   Author: Kamil Wojcicki, UTD, July 2011

clear all; close all; clc; rand('seed',0); randn('seed',0); fprintf('.\n');

    % signal-to-noise ratio (SNR) computation routine (function handle)
    snr = @(signal,noise)(10*log10(norm(signal)./norm(noise)));

    % Griffin & Lim's modified Hanning window (function handle)
    gnl_hanning = @(L,S)(0.5*sqrt(2*S/(0.75*L))*(1-cos((2*pi*((0:L-1)+0.5))/L)));

    % periodogram computation routine (function handle)
    psd = @(signal,window,nfft) ...
        (10*log10((abs(fftshift(fft(signal(:).*window(:),nfft))).^2)/length(signal)));

    fs = 16000;                             % sampling frequency (Hz)
    T = 0.256;                              % signal duration (seconds)
    N = round(T*fs);                        % signal duration (samples)
    n = [ 0:N-1 ];                          % discrete-time index vector
    time = n/fs;                            % time vector

    w = hanning(N).';                       % analysis window samples
    nfft = 2^nextpow2(2*N);                 % FFT analysis length
    freq = [ 0:nfft-1 ]/nfft*fs-fs/2;       % frequency vector (Hz)

    f = [ 500 1500 3500 ];                  % vector of frequency components (Hz)
    phi = [ pi/4 0 pi/3 ];                  % vector of phases (rad)
    A = [ 0.125 1 0.5 ];                    % vector of amplitudes 

    % generate signal vector
    x = sum( repmat(A.',1,N) .* ...
           cos(2*pi*repmat(f.',1,N).*repmat(time,length(f),1)+repmat(phi.',1,N)), 1 );

    % compute periodogram of the signal
    Pxx = psd( x, w, nfft );

    Tw = 32;                                % analysis frame duration (ms)
    Ts = Tw/4;                              % analysis frame shift (ms)
    Nw = round( 0.001*Tw*fs );              % analysis frame duration (samples)
    Ns = round( 0.001*Ts*fs );              % analysis frame shift (samples)
    direction = 'rows';                     % frames as rows
    padding = true;                         % pad with zeros

    window = gnl_hanning(Nw,Ns);            % window function samples

    % divide signal to frames
    [ frames, indexes ] = vec2frames( x, Nw, Ns, direction, window, padding );

    % reconstruct signal from frames
   %[ y ] = frames2vec( frames, indexes, direction, window, 'A&R' );
    [ y ] = frames2vec( frames, indexes, direction, window, 'G&L' );
   %[ y ] = frames2vec( frames, indexes, direction, window, 'VANILLA' );

    % truncate the reconstructed signal back to original length
    % i.e., remove any padding
    y = y(1:N); 

    % compute periodogram of the reconstructed signal
    Pyy = psd( y, w, nfft );

    % display SNR of the original and reconstructed signals
    fprintf( 'SNR=%0.2f dB\n', snr(x,y(:)-x(:)) );

    % generate time and frequency domain plots 
    hfig = figure('Position', [800 100 1024 768], ...
                    'PaperPositionMode', 'auto', 'Visible', 'on', 'color', 'w');

    subplot( 2,2,1 );
    plot( time, x, 'k-' );
    xlim( [0 max(time)*0.15] );
    ylim( [min(x)-0.3*max(x) 1.3*max(x)] );
    xlabel( sprintf('Time (s)') ); 
    ylabel( sprintf('Amplitude') ); 
    title( sprintf('Original') );
    set( gca, 'box', 'off' ); 

    subplot( 2,2,2 );
    plot( time, y, 'r-' );
    xlim( [0 max(time)*0.15] );
    ylim( [min(x)-0.3*max(x) 1.3*max(x)] );
    xlabel( sprintf('Time (s)') ); 
    ylabel( sprintf('Amplitude') ); 
    title( sprintf('Reconstructed') );
    set( gca, 'box', 'off' ); 

    subplot( 2,2,3 );
    plot( freq, Pxx, 'k-' );
    xlim( [-fs/2 fs/2] );
    xlabel( sprintf('Frequency (Hz)') ); 
    ylabel( sprintf('Power (dB)') ); 
    set( gca, 'xtick', [-6:2:6]*1E3 );
    set( gca, 'box', 'off' ); 

    subplot( 2,2,4 );
    plot( freq, Pyy, 'r-' );
    xlim( [-fs/2 fs/2] );
    xlabel( sprintf('Frequency (Hz)') ); 
    ylabel( sprintf('Power (dB)') ); 
    set( gca, 'xtick', [-6:2:6]*1E3 );
    set( gca, 'box', 'off' ); 

    print( '-dpng', mfilename ); 


% EOF