Conversion formula from RGB to YCbCr

Question

Whats the real conversion formula for this because I found so many ways on how to convert I don't know which one is real

From wikipedia:

From microsoft https://msdn.microsoft.com/en-us/library/ff635643.aspx :

and microsoft is the same with this conversion site http://www.equasys.de/colorconversion.html:

Can anybody explain the difference of the formula?

Solution

If it still actual they are almost the same. Differences are what value ranges you'll get in the result.

From Wiki's matrix (R',G',B' = 0..1) values will be: Y = 0..219, Cb = -112..112, Cr = -112..112. You can bring it to other matrices with dividing Y formula by 219, and Cb, Cr fomulas by 224.

From Microsoft's one (R,G,B = 0..255) you'll get Y = 0..255, Cb ≈ -127.5 .. 127.5, Cr ≈ -127.5 .. 127.5

The third matrix solves problems with negative numbers by adding 128 to them. The difference from Microsoft's matrix lies in the matrices multiplication.