This is discrete cosine transform code taken from net , i want to use it but didnt understand what happening in this code specially 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