Re: FFT VS DCT

On Thu, 26 Apr 2007 11:51:25 -0800, glen herrmannsfeldt
<gah@xxxxxxxxxxxxxxxx> wrote:

senthil_lsk wrote:

I see that all are asking why DCT is better than FFT or DFT.
Where FFT is prepered than DCT? Why ? Is it only for phase information?

The difference is boundary conditions. FFT (or DFT) has periodic
boundary conditions. DST has f(0)=f(L)=0, DCT has f'(0)=f'(L)=0.
For image processing the DCT boundary conditions are less noticeable.

(There is an explanation in Numerical Recipes, among others.)

-- glen

And then there's the Hartley transform, which uses cas(x)= sin(x) +
cos(x) as the basis function. The DHT has some interesting
properties of its own and is real-input real-output like the DST and
DCT.

7r4n5f0rm5 R fun!

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
.

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