Barco - RHDM-2301 - User manual ____________________________________________________ 93
Video signal processing
function is used which includes a linear “tail” at low luminance levels, followed by a scaled
and offset power function for higher luminance levels.
There are several L-V’ encoding standards, such as ITU-R BT.709 (Rec.709), SMPTE
240M, sRGB, xvYCC (based on ITU 1361). They all have the form of the transfer function
described below.
To characterize the encoding function, the following parameters are used:
•
b
r
(the voltage up to which the transfer curve is linear)
•
b
s
(the slope of the linear part:
b
s
=V/L
)
•
g
s
(the gamma correction or exponent of the power function)
In general, we can write any of these encoding standards with the formula:
where
5.3 Video encoding functions
5.3.1 Rec.709
Figure 49: L-V’ for Rec.709
(
)
1
0
1
'
/
1
≤
≤
<
≤
⎩
⎨
⎧
−
+
=
L
b
b
b
b
L
K
L
K
L
b
V
s
r
s
r
g
s
s
(
)
(
)
(
)
(
)
1
/
/
/
1
/
1
−
−
=
s
s
g
s
r
g
s
r
r
b
b
b
b
b
K
1
018
.
0
018
.
0
0
099
.
0
099
.
1
5
.
4
'
45
.
0
709
≤
≤
<
≤
⎩
⎨
⎧
−
=
L
L
L
L
V
