matlab code for musical note recognition based on frequency

i am working on a project to identify the musical note based on frequencies using window methods i need help to write the code and understanding it . ihave a code but its to advanced to understand......

clear;
clc;
close all;
% Note Recognition
%% Note Initialization
mainNames = char('C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B');
names = char('A0', 'A#0' ,'B0');
A0 = 27.5;
ind = 4;
for i = 0:87
    data(i+1) = A0 * (2^(1/12))^i;
    if i>2
         a = [mainNames( rem((ind - 4), 12)+1,:)  num2str(fix((ind - 4)/12)+1)];
         names = char(names, a);
         ind = ind + 1;
    end
end

% Band Initialization
bands(1) = 20;
for i = 1:87
    bands(i+1) = +7+(data(i) + data(i+1))/2;
end
bands(89) = 4500;

%%
fileName = 'c.wav';  % File name
[y, Fs] = audioread(fileName);            % Read audio file
y = (y(:,1) + y(:,2))*4;                % Decrease 2 channels to 1 
%y = (y(:,1));
y(1:2:end) = 0;   %from big vector take only odd index values         % Do decimation(decreace the no of samples)

frameLength = 4410*2; % 2 Güzel oldu

endPart = frameLength*ceil(length(y)/frameLength);  % complete the last frame %ceil is to round off to nearest integer

y(length(y)+1 : endPart) = 0;

f = linspace(1,Fs,frameLength); %creates linearly spaced vector 

%%
harmonics = 0;
for i = 1:round(length(y)/frameLength)      % For each frame
    % Divide audio into frames
    frames(i, 1:frameLength) = y( (frameLength*(i-1)+1):(frameLength*i) )';
    
    frame = y( (frameLength*(i-1)+1):(frameLength*i) )';
    frame = frame .* hamming(length(frame))';   % Hamming Window
    fframe = abs(fft(frame));                   % FFT
    
    fp = sum(fframe);
    p = sum(abs(frame));
    b = true;
    if(p < 200 || fp < 1000) % Put a threshold for processing
       b = false; 
    end
    
    % Bands
    for i=1:88
        freqBand(i) = mean(fframe( round(bands(i)/(Fs/frameLength) ):round(bands(i+1)/(Fs/frameLength))))^2;
    end
    
    % Plotting
    subplot(3,1,1)
    stem(freqBand)
    subplot(3,1,2)
    plot(fframe)
    xlim([0,500])
    subplot(3,1,3)
    plot(fframe)
    ylim([-1 1])
    
    hold off
    pause(0.1)
    sound(fframe,Fs)
    
    
    % Desicion
    m = find(freqBand == max(freqBand(:)));
    if(b) disp(names(m,:));     % Print the result
    else disp('.'); end
    
    if(b)
        index = 1;
        for i = 1:88
            if(freqBand(i) > 2000)
                harmonics(index) = i;
                index = index+1;
            end 
        end
    
    end

end

this is the code.....

[Paavan Kumar Dornadula]

how to verify is above code is correct or not?

Answer 1

[Thiago Henrique Gomes Lobato]

To really undestand the method, first try to define how exactly you gonna get the frequencies. Your main steps are :

1. Define your notes and which frequency do they have (Line 5-23)
2. Read your sound data and define the window size to evaluate the sound (Line 24-33). Here your code has some flaws. Ex: Decimation change the sampling rate, so you can't simply do it to "decrease number of samples" and don't compensate it afterwards. If you want a mono channel from a stereo recording you normally take the mean, not the sum times 4.
3. For each evaluation window, take the FFT and check which note has the frequency closest to the maximum amplitude (Line 34-86). In your code the FFT is summed in bands so each note has its "own" band and then you can just check the strongest band.

The algorithm is quite simple, but the way it was implemented in your code is indeed not so optimal. I would suggest you to try to implement it yourself in a more clean way based in those main steps. This should also help you to better internalize it.

[varun taliparambe vitel]

thank you

i will try implementing myself but i dont know why those formulas used

Answer 2

[Geetesh Mokhare]

endPart = frameLength*ceil(length(y)/frameLength

WHAT IS THE MEANING OF THIS?

[varun taliparambe vitel]

We are trying to define the last part of the frame

[Geetesh Mokhare]

One more help Can you tell me the application of this code in 5-6 lines ? Please request