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

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Voltarian
Voltarian 2020-4-1
回答： Geoff Hayes 2020-4-3
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

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回答（1 个）

Geoff Hayes
Geoff Hayes 2020-4-3
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

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