YDbDr

Short description: Colour space used in the SECAM analog color TV standard

An image along with its $Y$, $D_B$ and $D_R$ components.

YDbDr, sometimes written $Y{D}_B{D}_R$, is the colour space used in the SECAM (adopted in France and some countries of the former Eastern Bloc) and PAL-N (adopted in Argentina, Paraguay and Uruguay) analog colour television broadcasting standards. 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.

$Y{D}_B{D}_R$ is composed of three components: $Y$, $D_B$ and $D_R$. $Y$ is the luminance, $D_B$ and $D_R$ are the chrominance components, representing the red and blue colour differences.

Formulas

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

These formulae approximate the conversion between the RGB colour space and $Y{D}_B{D}_R$.

$\begin{array}{rl}R,G,B,Y& \in [0,1]\\ D_B,D_R& \in [-1.333,1.333]\end{array}$

From RGB to YDbDr:

$\begin{array}{rl}Y& =+0.299R+0.587G+0.114B\\ D_B& =-0.450R-0.883G+1.333B\\ D_R& =-1.333R+1.116G+0.217B\\ \left[\begin{array}{c}Y\\ D_B\\ D_R\end{array}\right]& =\left[\begin{array}{ccc}0.299& 0.587& 0.114\\ -0.450& -0.883& 1.333\\ -1.333& 1.116& 0.217\end{array}\right]\left[\begin{array}{c}R\\ G\\ B\end{array}\right]\end{array}$

From YDbDr to RGB:

$\begin{array}{rl}R& =Y+0.000092303716148D_B-0.525912630661865D_R\\ G& =Y-0.129132898890509D_B+0.267899328207599D_R\\ B& =Y+0.664679059978955D_B-0.000079202543533D_R\\ \left[\begin{array}{c}R\\ G\\ B\end{array}\right]& =\left[\begin{array}{ccc}1& 0.000092303716148& -0.525912630661865\\ 1& -0.129132898890509& 0.267899328207599\\ 1& 0.664679059978955& -0.000079202543533\end{array}\right]\left[\begin{array}{c}Y\\ D_B\\ D_R\end{array}\right]\end{array}$

You may note that the $Y$ component of $Y{D}_B{D}_R$ is the same as the $Y$ component of $Y$$U$$V$. $D_B$ and $D_R$ are related to the $U$ and $V$ components of the YUV colour space as follows:

$\begin{array}{rl}{D}_B& =+3.059U\\ D_R& =-2.169V\end{array}$

References

• Shi, Yun Q. and Sun, Huifang Image and Video Compression for Multimedia Engineering, CRC Press, 2000 ISBN:0-8493-3491-8

See also

• YUV - related colour system
• PAL-N (Argentina, Paraguay and Uruguay) - some information on PAL-N