Splitting piano song .wav file into sections is resulting in the same frequency instead of different frequencies.

I'm attempting to split a simple audio file into 1 seccond interval sections but the result is yielding the same frequencies. The code is supposed to break up the audio which then performs a fourier transform on the one seccond time interval and yields a frequency.

clear all;

%Parameters
r = 1; %Max and Min Peak Distances
mpd = r*0.9; 
MPD = r/0.9; 
minpeakheight = 0.2; % Minimum peak height for sampled Piano notes is around 0.2, look at FFT Plot
minpeakdistance = 1; 

%User Finds Audio File 
[file,path] = uigetfile({'*.wav';},'input file');
name = fullfile(path,file);

%Playing Audio
if isequal(file,0)
   disp('User selected Cancel');
else
   disp(['User selected ', fullfile(path,file)]);

   [y, fs] = audioread(name);
    soundsc(y, fs);
end

n = length(y);

t = (1/fs)*(1:length(y)); 
X = fft(y);
Xk = abs(X); 
Xk = Xk(1:length(y)/2); 
f = fs*(0:length(y)/2-1)/length(y); 
x = f; % x-vector 
j = Xk/max(Xk); % y-vector   
    
for k = 1:fs:n
    audioBlock = y(k:min(k + fs - 1, n), :);
    % do something with this block
 
    [peak_vals,peak_locs] = findpeaks(j,x,'MinPeakHeight',minpeakheight,'MinPeakDistance',minpeakdistance);
    [~,index] = max(peak_vals(peak_locs<peak_locs(1)+mpd)); % index of the frequncy peak

    %DisplayFrequency
    new_peak_locs = peak_locs(index); % position peak/Frequency Value
    fprintf('The Frequency of the Note is:')
    f = new_peak_locs 
    new_peak_vals = peak_vals(index);

    %DisplayPitch
    disp('The Pitch is:')
    FrequencyToPitch(f)
    
    audiowrite(name,y,fs);

end

Answer 1

[Geoff Hayes]

Voltarian - since you have the audioBlock (of one second's worth of data) wouldn't you just use the code that you already have to do the FFT on y and do that for the block? Something like

for k = 1:fs:n
    audioBlock = y(k:min(k + fs - 1, n), :);
    
    % <----- replace y with audioBlock
    X = fft(audioBlock);
    Xk = abs(X); 
    Xk = Xk(1:length(audioBlock)/2); 
    f = fs*(0:length(audioBlock)/2-1)/length(audioBlock); 
    x = f; % x-vector 
    j = Xk/max(Xk); % y-vector  
 
    [peak_vals,peak_locs] = findpeaks(j,x,'MinPeakHeight',minpeakheight,'MinPeakDistance',minpeakdistance);
    [~,index] = max(peak_vals(peak_locs<peak_locs(1)+mpd)); % index of the frequncy peak
    %DisplayFrequency
    new_peak_locs = peak_locs(index); % position peak/Frequency Value
    fprintf('The Frequency of the Note is:')
    f = new_peak_locs 
    new_peak_vals = peak_vals(index);
    %DisplayPitch
    disp('The Pitch is:')
    FrequencyToPitch(f)
    
    % do you really want to rewrite the data to the wav file or write the blocks to
    % new files?
    % audiowrite(name,y,fs);
end