Barco - RHDM-2301 - User manual ____________________________________________________ 91
Video signal processing
5 Video signal processing
5.1 General
The general way of encoding light captured from a scene (with a camera) to a video
signal, which serves as input for a display unit, can be described by the following steps:
•
Step 1
: Light from the scene is captured and transferred to linear RGB. This conver-
sion occurs with a given color gamut and white point.
•
Step 2
: The linear RGB signal is transferred to a perceptual uniform R’G’B’ video
signal. This is called the gamma correction.
•
Step 3
: The color channels can be encoded. The encoding transforms the R’G’B’
video signal to an Y’C
b
C
r
video signal to optimize stream capacity. Often a 4:2:2
chroma subsampling is performed. This conversion is not always performed and
unencoded R’G’B’ 4:4:4 can be transmitted as e.g. Dual link HDSDI or 3Gb/s SDI.
Each step is defined by a standard (e.g. Rec.709) The different standards used in the
different steps are listed in the table below:
Table 2: Standards used for video signal generation
Figure 48: From captured light on the scene to the image on the screen
SD signals
480i, 576i
HD signals
720p, 1080i,
1080p
HD 1035i
Step 1
L to RGB
480i: SMPTE RP145
576i: EBU 3213
Rec.709
SMPTE RP145
Step 2
RGB to R’B’G’
Rec.709
Rec.709
SMPTE 240M
Step 3
R’G’B’ to Y’C
b
C
r
ITU-R BT.601 (Rec. 601) Rec.709
SMPTE 240M
