Editing Y′UV (section)

=== HDTV with BT.709 ===
[[File:CIExy1931 Rec 2020 and Rec 709.svg|thumb|HDTV Rec.&nbsp;709 (quite close to SDTV Rec.&nbsp;601) compared with UHDTV [[Rec. 2020|Rec.&nbsp;2020]]]]

For [[high-definition video|HDTV]] the [[ATSC standards|ATSC]] decided to change the basic values for W<sub>R</sub> and W<sub>B</sub> compared to the previously selected values in the SDTV system. For HDTV these values are provided by [[Rec. 709|Rec.&nbsp;709]]. This decision further impacted on the matrix for the Y′UV↔RGB conversion so that its member values are also slightly different. As a result, with SDTV and HDTV there are generally two distinct Y′UV representations possible for any RGB triple: a SDTV-Y′UV and an HDTV-Y′UV one. This means in detail that when directly converting between SDTV and HDTV, the luma (Y′) information is roughly the same but the representation of the chroma (U & V) channel information needs conversion. Still in coverage of the [[CIE 1931 color space]] the Rec.&nbsp;709 color space is almost identical to Rec.&nbsp;601 and covers 35.9%.<ref name=TVTechnologyDecember2012SuperHiVision>{{cite news |title="Super Hi-Vision" as Next-Generation Television and Its Video Parameters |publisher=Information Display |url=http://www.informationdisplay.org/article.cfm?year=2012&issue=12&file=art6 |access-date=1 January 2013}}</ref> In contrast to this UHDTV with Rec.&nbsp;2020 covers a much larger area and thus its very own matrix was derived for YCbCr (no YUV/Y′UV, since decommissioning of analog TV).

BT.709 defines these weight values:

:<math>\begin{align}
  W_R &= 0.2126, \\
  W_G &= 1 - W_R - W_B = 0.7152, \\
  W_B &= 0.0722 \\
\end{align}</math>
The ''U''<sub>max</sub> and ''V''<sub>max</sub> values are from above.

The conversion matrices for analog form of BT.709 are these, but there is no evidence those were ever used in practice (instead only actually described form of BT.709 is used, the [[YCbCr#ITU-R BT.709 conversion|YCbCr]] form):

:<math>\begin{align}
  \begin{bmatrix} Y' \\ U \\ V \end{bmatrix}
  &=
  \begin{bmatrix}
    0.2126  &  0.7152  &  0.0722 \\
   -0.09991 & -0.33609 &  0.436 \\
    0.615   & -0.55861 & -0.05639
  \end{bmatrix}
  \begin{bmatrix} R' \\ G' \\ B' \end{bmatrix} \\

  \begin{bmatrix} R' \\ G' \\ B' \end{bmatrix}
  &=
  \begin{bmatrix}
  1 &  0       &  1.28033 \\
  1 & -0.21482 & -0.38059 \\
  1 &  2.12798 &  0
  \end{bmatrix}
  \begin{bmatrix} Y' \\ U \\ V \end{bmatrix}
\end{align}</math>