fft - why DCT transform is preferred over other transforms in video/image compression -


i went through how dct (discrete cosine transform) used in image , video compression standards.

but why dct preferred on other transforms dft or dst?

because cos(0) 1, first (0th) coefficient of dct-ii mean of values being transformed. makes first coefficient of each 8x8 block represent average tone of constituent pixels, start. subsequent coefficients add increasing levels of detail, starting sweeping gradients , continuing increasingly fiddly patterns, , happens first few coefficients capture of signal in photographic images.

sin(0) 0, dsts start offset of 0.5 or 1, , first coefficient gentle mound rather flat plain. unlikely suit ordinary images, , result dsts require more coefficients dcts encode blocks.

the dct happens suit. there it.


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