## YDbDr (Colorspaces VI)

Also an analog colorspace, YDbDr was used in SÉCAM (quentielle ccouleur à mémoire), the French analog TV standard that was also used in Germany, Greece and the Middle east, among others. YDbDr, like the others, use the luminance, Y, and two chrominance components: Db, Dr (for différence bleue and différence rouge).

$\begin{bmatrix} 0.299 & 0.587 & 0.114\\ -0.450 & -0.883 & -1.333\\ 1.333 & -1.109 & -0.217\\ \end{bmatrix} \begin{bmatrix} r\\ g\\ b\\ \end{bmatrix} = \begin{bmatrix} Y\\ D_B\\ D_R\\ \end{bmatrix}$

with inverse

$\begin{bmatrix} 1 & 0 & 0.526\\ 1 & -0.129 & -0.268\\ 1 & 0.665 & 0\\ \end{bmatrix} \begin{bmatrix} Y\\ D_B\\ D_R\\ \end{bmatrix} = \begin{bmatrix} r\\ g\\ b\\ \end{bmatrix}$

What’s unusual with this one is how the chrominance components are scaled. Unlike the other colorspaces we’ve seen so far, this one stretches the two chrominance components quite a bit, giving it a squished appearance. Why? It may be that it buys the scheme some tolerance to the frequency modulation used to encode the chrominance components—but I haven’t found anything on this. In fact, just finding documentation on SÉCAM is hard.