RGB Vs YCbCr , Static Globals not allowed in BREW

RGB Vs. YCbCr

I presume you know RGB. Any image is made up of two components, brightness and color information. Brightness information is high frequency information and color is low frequency information. Human Visual System (HVS) is more sensitive to brightness then color. Means it can identify brightness more better then change in color.

Chroma is the color information of the picture. It is determined by seperating luma (Y) value from blue and red signal. If you need a quick formula here it is

For taking advantage of this YCbCr model was developed. In this Y is calculated from weighted R, G and B. And then Cb and Cr are calculated. Then Cb and Cr are comressed more aggresively then Y.
If same principle [compressing low frequency color information] is applied to RGB model, image would  not be of that quality as of JPEG. This is the difference of RGB and YCbCr.

Sources

http://www.impulseadventure.com/photo/jpeg-color-space.html
http://en.wikipedia.org/wiki/Ycbcr

Why static and global varibles in BREW dynamic apps are not allowed ?

Very crude reason : There is no data section in .mod files created by BREW. Static variables are allocated in data segment of programme. And they are offseted from a global "SB" static base register. Now BREW loads application anywhere in memory so if it were to allow static variables it would have to remember SB for evey applet which apparently BREW does not want to do. Though there are some hacks for it. For more information search BREW forums @ Qualcomm.com

Meanwhile Linux server in our company location is still not up and I am waiting for it to compile my QT code.