Thread Subject: Regarding YCbCr 4:2:0

       I have some doubt in YCbCr 4:2:0 .In my project
the output is in YCbCr4:2:0 format.In that they take 2*2
matrix. From that first we find luminance in that 4 pixels.
(2*2) then the concept given in IEEE Paper is find Cb & Cr
from one pixel in that 2*2 matrix.

       Is it enough to find one Cb & Cr from 4 pixels?
Please anyone help me & explain about YCbCr 4:2:0

"Selwyna Bas" <gracelin@mathworks.com> wrote in message
<fmd6u1$ef0$1@fred.mathworks.com>...
> I have some doubt in YCbCr 4:2:0 .In my project
> the output is in YCbCr4:2:0 format.In that they take 2*2
> matrix. From that first we find luminance in that 4 pixels.
> (2*2) then the concept given in IEEE Paper is find Cb & Cr
> from one pixel in that 2*2 matrix.
>
> Is it enough to find one Cb & Cr from 4 pixels?
> Please anyone help me & explain about YCbCr 4:2:0

YCbCr 4:2:0 is one of sampling formats for three components Y,
Cb, Cr used in image/video coding standards.
Some other formats are YCbCr 4:4:4,YCbCr 4:2:2

4:4:4 for every four luminance samples there are
         four Cb and four Cr samples

Pixel 1 Pixel 2 Pixel 3 Pixel 4
Y,Cb,Cr Y,Cb,Cr Y,Cb,Cr Y,Cb,Cr


4:2:2 for every four luminance samples in the horizontal
         direction there are two Cb and two Cr samples.

Pixel 1 Pixel 2 Pixel 3 Pixel 4
Y,Cb,Cr Y Y,Cb,Cr Y

4:2:0 Cb and Cr each have half the horizontal
         and vertical resolution of Y


Block 4x4 pixels


Y Y Y Y
 Cb,Cr Cb,Cr
Y Y Y Y

Y Y Y Y
 Cb,Cr Cb,Cr
Y Y Y Y

It means that, in 4:2:0 format, 4 pixels in each group 2x2
share the same chroma.

for further information, refer to this illustration

http://en.wikipedia.org/wiki/
Image:Chroma_subsampling_ratios.png

and this link
http://en.wikipedia.org/wiki/Chroma_subsampling

Finally, your question does not have any relation to MATLAB,
so it is better if you post it in image and video community.

HTH
Anh Huy Phan
RIKEN - BSI