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Why there is a difference between the dct computed by the MATLAB dct function and one computed by dct matrix multiplication?

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The result is different, though both methods give inverse transform correctly.

Accepted Answer

David Goodmanson
David Goodmanson on 26 Feb 2018
Edited: David Goodmanson on 26 Feb 2018
Hi Mohsin,
x needs to be a column vector as you did, but you don't need to take the transpose of dctmtx:
x = 1:8
y1 = dct(x')
y2 = dctmtx(8)*x'
y1 - y2
x1 = idct(y1)
x2 = dctmtx(8)\y2
Same results, out and back.

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