This is discrete cosine code taken from the net. I want to use it but didnt understand whats happening in this code, especially whole for loop Statements.
[A1, f] = wavread('A1.wav');
windowSize = 8192;
samplesHalf = windowSize / 2;
samplesQuarter = windowSize / 4;
samplesEighth = windowSize / 8;
funkyCompressed2 = [];
funkyCompressed4 = [];
funkyCompressed8 = [];
for i=1:windowSize:length(A1)-windowSize
windowDCT = dct(A1(i:i+windowSize-1))
funkyCompressed2(i:i+windowSize-1) = idct(windowDCT(1:samplesHalf), windowSize);
funkyCompressed4(i:i+windowSize-1) = idct(windowDCT(1:samplesQuarter), windowSize);
funkyCompressed8(i:i+windowSize-1) = idct(windowDCT(1:samplesEighth), windowSize);
end
actually this is matlab code as per your code.if u know as well in "C" -language then u can get easily.so it's similar like for loop in "C" language. but if u want to know about more this code then u go step by step in matlab and check it in tab of matlab.i hope u will get clear.
Consult Chapter 12 of the book Numerical Recipes, 2nd edition (Cambridge University Press, 1997), by Press, et al. In the case of the cosine transform, one exploits the fact that the function to be Fourier transformed is an even function of its argument. The program that you have displayed here above essentially carries out a process named 'decimation', of which there are two types, 'decimation-in-time' by Cooley & Tukey and 'decimation-in-frequency', by Sande and Tukey. Lastly, I would strongly recommend all to use the FFTW package, developed by Matteo Frigo and Steven Johnson. I attach below the link to the official website of FFTW.
http://www.fftw.org/
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