DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Figure 26.3 CBCR compo-
+112
nents for Rec. 709
R
HDTV are shown in their
mathematical form. At an
8-bit interface, an offset
of +128 is added to each
color difference component.
Yl
-112 0
G
-112
C R axis
The inverse, decoding matrix is this:
⎡R'⎤
⎡
⎤ ⎡709
1 0 1. 5748 Y'
⎤
⎢ ⎥ ⎢
⎥ ⎢ ⎥
⎢G'⎥
= ⎢1
−0. 187324 −0.
468124⎥
• ⎢ PB
⎥
⎢
⎣
B'⎥
⎢
⎥ ⎢ ⎥
⎦ ⎣
1 1. 8556 0
⎦
P
⎣⎢
R ⎦⎥
C B C R components for Rec. 709 HDTV
709Y’C B C R coding is used in component digital HDTV
equipment. In 8-bit systems, luma has an excursion of
219. Color differences C B and C R are coded in 8-bit
offset binary form, with excursions of ±112. The
[C B, C R] plane of HDTV is plotted in Figure 26.3.
In 8-bit systems, a luma offset of +16 is added at the
interface, placing black at code 16 and white at code
235; an offset of +128 is added to C B and C R , yielding
a range of 16 through 240 inclusive. (Following the
convention of the previous chapter, in the equations to
follow I write the offset terms in gray.) HDTV standards
provide for 10-bit components, and 10-bit studio video
equipment is commonplace. In a 10-bit interface, the
8-bit interface levels and prohibited codes are maintained;
the extra two bits are appended as least-significant
bits to provide increased precision.
316 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES
Cy
Mg
B
+112 CB axis
Eq 26.4