[WM]: =?EUC-KR?B?UmU6IFtXTV06IHdoeSB1c2UgRENUPz8gKHVyZ2VudCk=?=

[=?EUC-KR?B?Ikh5b3VuZyBKb29uZyBLaW0i?= <khj@mail.kangwon.ac.kr>]

The reason why people use DCT is quite simple: It is just because people use it widely.
There are so many transforms you can choose.
You can embed watermarks by using any transform you have in mind.
DCT is not the sole solution for watermarking.
However, the most significant benefit of DCT is, I think, it is a standard compression technique of JPEG/MPEG.
It is efficient in compression performance and relatively fully understood.
At least your embedded watermarks should survive JPEG/MPEG compression.
In short, DCT is used since it is widely used.

cheers,

Hyoung-Joong




----- Original Message -----
From: "Martin Dietze" <di@fh-wedel.de>,
To: <watermarking@watermarkingworld.org>,
Date: 2005-04-18 17:14:41
Subject: Re: [WM]: why use DCT?? (urgent)

On Sun, April 17, 2005, rajan sheth wrote:

> i im implementing visible watermarking using DCT (for color images) 
> and invisible watermarking also using DCT (for grayscale images).
> 
> but i dont know whether DCT have any advantage over other 
> transforms.(especially DWT)

Sorry for asking this question: if you don't know why anyone should use the DCT, why are you then implementing it? I guess you
should study the advantages and disadvantages of different embedding domains before you make a choice.

> can any one tell me why i should use DCT transform over other transforms??

There's much more to say about this than what could be answered in a mailing list posting. Also a lot has already been posted here
regarding this subject.  I suggest you use google to look for relevant papers and check the mailing list archieves for postings on
this subject. 

I don't believe that what anyone could tell you here in a posting to this mailing list list would be enough to base a decision on or
justify it when starting a new project on watermarking.

Cheers,

Martin

--
---- Dipl.Ing. Martin Dietze -- / --- martin.dietze@4g-systems.biz ----------
-- 4G Systeme GmbH Hamburg --- / --- martin@the-little-red-haired-girl.org --



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