GRASS VALLEY XIP-3901, Руководство пользователя

Страница: 300 / 308

300
BBC HLG Look-Up Table
Scene-Light versus Display-Light Conversions
code value 940) (required for ITU-R BT.814 HDR PLUGE and ITU-R BT.2111 HDR Color Bars),
so are most suitable for broadcast TV applications.
Fig. A-1: Type II signal scaling, intended for full-range input signals (for example, S-Log3)
Fig. A-2: Type III signal scaling, primarily intended for hardware-based LUT applications
The Type II “full-range mode” LUT is used to convert full-range PQ and S-Log3 signals to
HLG. So full-range Type II versions of the PQ1000, PQ4000, S-Log3 (100%) and S-Log3
(200%) conversion LUTs are provided.
We recommended only using narrow-range signals with HLG, to improve interoperability,
maintain signal fidelity and reduce the likelihood of errors in production. So even when a
hardware LUT device is operated in full-range mode, the HLG output signal is always offset
and scaled within the full-range “container”, to lie within the usual narrow signal range of 64
to 940 (10-bits).
Scene-Light versus Display-Light Conversions
Most SDR/HDR format conversions are based on “display-light”. By that we mean that the
conversion calculates the light produced by the original signal on a reference display
operating in the original format, and attempts to produce a similar light output on a
reference display operating in the new output format. Display-light conversions are
designed to preserve the artistic intent of the pictures after conversion. So display-light
conversions work well for graded content. An example of a display-light conversion for
BT.709 to BT.2100 HLG is shown in the Figure below.
Fig. A-3: SDR to HDR Display-Light Conversion
For live production, however, it is usually more important to color match signals produced
in different formats – for example a native BT.2100 HLG camera with an SDR BT.709 super
3D-LUT
Matrix
1023
0
Y
'
C
'
B
C
'
R
Input Signal Range:
Full
LUT Mode:
Full
1023
0
R
'
G
'
B
'
0
1
940
64
Matrix
1023
0
R
'
G
'
B
'
940
64
1023
0
Y
'
C
'
B
C
'
R
Scale Output
(0 - 1023)
Output Signal Range:
Narrow
940
64
1019
4
Clip to SDI
Range
Y
'
C
'
B
C
'
R
Type II
Normalisation
(0 - 1)
Input
Input signal and
processing range
Output
Nominal output
signal range
Processing
range
3D-LUT
940
64
Matrix
1023
0
Y
'
C
'
B
C
'
R
Input Signal Range:
Narrow
LUT Mode:
Full
940
64
1023
0
R
'
G
'
B
'
0
1
940
64
Matrix
1023
0
R
'
G
'
B
'
940
64
1023
0
Y
'
C
'
B
C
'
R
Output Signal Range:
Narrow
Input
940
64
1019
4
Clip to
SDI Range
Y
'
C
'
B
C
'
R
Type III
Scale Output
(0 - 1023)
Normalisation
(0 - 1)
Nominal input
signal range
Output
Nominal output
signal range
Processing
range
SDR BT.709
signal
BT.1886 EOTF
L
W
=100 cd/m
2
BT.709
to BT.2020
Colour
SDR BT.709
display‐light
Optional
brightness
adjustment
Inverse HLG
EOTF
L
W
=1000 cd/m
2
HDR display‐light
HDR BT.2100
HLG signal
SDR BT.2020
display‐light
Optional
highlight
expansion