YDbDr

YDbDr, sometimes written ${\displaystyle YD_{B}D_{R}}$, is the colour space^[1] used in the SECAM (adopted in France and some countries of the former Eastern Bloc) analog colour television broadcasting standard.^[2][3][4] It is very close to YUV (used on the PAL system) and its related colour spaces such as YIQ (used on the NTSC system), YPbPr and YCbCr.^[5][6]

An image along with its ${\displaystyle Y}$, ${\displaystyle D_{B}}$ and ${\displaystyle D_{R}}$ components.

${\displaystyle YD_{B}D_{R}}$ is composed of three components: ${\displaystyle Y}$, ${\displaystyle D_{B}}$ and ${\displaystyle D_{R}}$. ${\displaystyle Y}$ is the luminance, ${\displaystyle D_{B}}$ and ${\displaystyle D_{R}}$ are the chrominance components, representing the red and blue colour differences.^[7]

Formulas

The three component signals are created from an original ${\displaystyle RGB}$ (red, green and blue) source. The weighted values of ${\displaystyle R}$, ${\displaystyle G}$ and ${\displaystyle B}$ are added together to produce a single ${\displaystyle Y}$ signal, representing the overall brightness, or luminance, of that spot. The ${\displaystyle D_{B}}$ signal is then created by subtracting the ${\displaystyle Y}$ from the blue signal of the original ${\displaystyle RGB}$, and then scaling; and ${\displaystyle D_{R}}$ by subtracting the ${\displaystyle Y}$ from the red, and then scaling by a different factor.

These formulae approximate the conversion between the RGB colour space and ${\displaystyle YD_{B}D_{R}}$.

${\displaystyle {\begin{aligned}R,G,B,Y&\in \left[0,1\right]\\D_{B},D_{R}&\in \left[-1.333,1.333\right]\end{aligned}}}$

From RGB to YDbDr:

${\displaystyle {\begin{aligned}Y&=+0.299R+0.587G+0.114B\\D_{B}&=-0.450R-0.883G+1.333B\\D_{R}&=-1.333R+1.116G+0.217B\\{\begin{bmatrix}Y\\D_{B}\\D_{R}\end{bmatrix}}&={\begin{bmatrix}0.299&0.587&0.114\\-0.450&-0.883&1.333\\-1.333&1.116&0.217\end{bmatrix}}{\begin{bmatrix}R\\G\\B\end{bmatrix}}\end{aligned}}}$

From YDbDr to RGB:

${\displaystyle {\begin{aligned}R&=Y+0.000092303716148D_{B}-0.525912630661865D_{R}\\G&=Y-0.129132898890509D_{B}+0.267899328207599D_{R}\\B&=Y+0.664679059978955D_{B}-0.000079202543533D_{R}\\{\begin{bmatrix}R\\G\\B\end{bmatrix}}&={\begin{bmatrix}1&0.000092303716148&-0.525912630661865\\1&-0.129132898890509&0.267899328207599\\1&0.664679059978955&-0.000079202543533\end{bmatrix}}{\begin{bmatrix}Y\\D_{B}\\D_{R}\end{bmatrix}}\end{aligned}}}$

You may note that the ${\displaystyle Y}$ component of ${\displaystyle YD_{B}D_{R}}$ is the same as the ${\displaystyle Y}$ component of ${\displaystyle Y}$${\displaystyle U}$${\displaystyle V}$. ${\displaystyle D_{B}}$ and ${\displaystyle D_{R}}$ are related to the ${\displaystyle U}$ and ${\displaystyle V}$ components of the YUV colour space as follows:

${\displaystyle {\begin{aligned}D_{B}&=+3.059U\\D_{R}&=-2.169V\end{aligned}}}$

See also

• YUV - related colour system