I get the error 'Subscript indices must either be real positive integers or logicals'? Please help!

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JAE KANG JANG 2015-11-14

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编辑： Stephen23 2015-11-19

Hi,

I am trying to take short parts of hundreds of mp3 files and mix them automatically. It works until about 43rd song but after that I get the error message at the line of "x = x(end-fs*excerptDur:end);". I can't find the solution. Please help.

---------------------------------------------

filenames = dir('*.mp3');
clc
analysis.dur = zeros(1, length(filenames));
fs = 44100;
totalDur = 100;
y        = zeros(1, fs*totalDur);
excerptDur = 2;
hop        = excerptDur/4*fs;
startPtr = 1;
endPtr   =  excerptDur*fs+1;
      warning off
  for i=1:length(filenames)
      [x, fs] = audioread(filenames(i).name);     
      x = mean(x');
      x = x(1:end/10);
      x = x(end-fs*excerptDur:end);
      analysis.dur(i) = round(length(x)/fs*60);
      x1 = hann(length(x)).*x';
      y(startPtr:endPtr) = y(startPtr:endPtr) + x1';
      startPtr = startPtr + hop;
      endPtr   = endPtr + hop;
      disp(filenames(i).name)
  end
y = y(1:endPtr);
warning on
sound(y, fs)
spectrogram(y,2048,2000,'yaxis');

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Answer 1

Stephen23 2015-11-14

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Your index is probably going to zero or negative. Consider if fs*exceptDur is larger than the length of x

x = x(end-fs*excerptDur:end);

then it is equivalent to

x = x(-N:end);

for some whole number N. You could avoid this by using max:

x = x(max(1,end-fs*excerptDur):end);

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JAE KANG JANG 2015-11-19

Thank you so much for your reply. The problem was one of mp3 files had a different sample rate.

I am trying to extract some portions(about 1 second) from a lot of mp3 files(about 1000) then put them in order to create a mix of an audio file. The code extracts in the middle of audio file. However, it would be great if it extracts the beginning of the chorus part. I think the chorus part has the peak or maximum energy in the song and I've been figuring out but I couldn't and I really need help... If you can help me that would be really great.. Thank you so much for your help. I really appreciate it.