YPbPr color model

The YPbPr - color model is mainly in the analog transmission of video signals from digital YCbCr -farbkodierten sources such as DVD or DVB used the most by component video takes place port. Originally specified and briefly used, it was also used for analog HDTV .

YPbPr is often erroneously referred to as YUV , also in operating instructions and housing labels from device manufacturers. YUV is a related analog color model, but based on different conversion formulas. Contrary to popular belief, YUV is not used for component video connections, but only for analog PAL television (via antenna, satellite and cable) and for PAL transmission via composite video or S-video .

Since the YPbPr signal transmits the brightness / luminance information Y and the two color difference / chrominance information Pb and Pr separately, no modulation or quadrature amplitude modulation is necessary. As a result, YPbPr offers a better picture than the color picture blanking sync signal FBAS or the video signal Y / C or S-Video .

YPbPr is - like its digital counterpart YCbCr - described as a possible implementation in the ITU-R BT 601 standard (formerly CCIR 601). There are also different implementations of this that follow other standards with different calculation coefficients.

Calculation of the YPbPr values ​​from the gamma-corrected ( i.e. linear in brightness) color triple R'G'B ':

${\displaystyle {\begin{bmatrix}Y'\\Pb\\Pr\end{bmatrix}}\approx {\begin{bmatrix}0{,}299&0{,}587&0{,}114\\-0{,}168736&-0{,}331264&0{,}5\\0{,}5&-0{,}418688&-0{,}081312\end{bmatrix}}\cdot {\begin{bmatrix}R'\\G'\\B'\end{bmatrix}}}$

Calculation of the R'G'B 'values ​​from YPbPr values:

${\displaystyle {\begin{bmatrix}R'\\G'\\B'\end{bmatrix}}\approx {\begin{bmatrix}1&0&1{,}402\\1&-0{,}344136&-0{,}714136\\1&1{,}772&0\end{bmatrix}}\cdot {\begin{bmatrix}Y'\\Pb\\Pr\end{bmatrix}}}$

The matrices apply to the constants K _B and K _R from ITU-R BT 601:

${\displaystyle K_{B}=0{,}114}$

${\displaystyle K_{R}=0{,}299}$

Expressed in terms of the constants, the formulas for the conversion to Y'PbPr are in general:

${\displaystyle Y'=K_{R}\cdot R'+(1-K_{B}-K_{R})\cdot G'+K_{B}\cdot B'}$

${\displaystyle P_{B}={\frac {1}{2}}\cdot {\frac {B'-Y'}{1-K_{B}}}}$

${\displaystyle P_{R}={\frac {1}{2}}\cdot {\frac {R'-Y'}{1-K_{R}}}}$

And for the conversion to R'G'B ':

${\displaystyle R'=2\ (1-K_{R})\ P_{R}+Y'}$

${\displaystyle B'=2\ (1-K_{B})\ P_{B}+Y'}$

${\displaystyle G'={\frac {2\ K_{B}\ (1-K_{B})}{K_{B}+K_{R}-1}}\ P_{B}+{\frac {2\ K_{R}\ (1-K_{R})}{K_{B}+K_{R}-1}}\ P_{R}+Y'}$

Web links

• ColorFAQ by Charles Poynton (English)

See also

• Color space (further color spaces, color space systems, color models)