Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!apple!netcom!allanh
From: allanh@netcom.COM (Allan N. Hessenflow)
Newsgroups: comp.graphics
Subject: Re: Kodak CD Specs, or what is YCC
Keywords: YCC CD-ROM
Message-ID: <26946@netcom.COM>
Date: 5 Mar 91 17:37:58 GMT
References: <2804@wn1.sci.kun.nl>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 23

In article <2804@wn1.sci.kun.nl> ge@dbf.kun.nl (Ge' Weijers) writes:
>In a German-language photography journal I saw a (nontechical) explanation
>of the forthcoming Kodak Photo-CD. Are the specifications known yet?
>The article mentioned coding pixels in YCC coordinates in stead of
>YIQ or RGB. What is this? The article mentioned that YCC had its advantages
>when the picture was compressed by a lossless method.

It probably should have said YCbCr which is a colourspace defined in CCIR-601
(although I've recently been informed that there are other different 
colourspaces also called YCbCr); it's similar to YIQ in that luma and chroma
are separate.  I don't see any advantage to YCbCr in lossless systems; in 
fact the conversion from to RGB to YCbCr and back is normally lossy in itself.
This is because YCbCr is a larger colourspace than RGB, so if the same number
of bits are used to represent a colour then the transform from YCbCr to RGB can
not produce all possible RGB values.  YCbCr does have advantages for lossy
compression because more information can be thrown away from the chroma
channels than from luma.

allan


-- 
Allan N. Hessenflow   {apple|claris}!netcom!allanh    allanh@netcom.com