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150 Barco - RHDM-2301 - User manual
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 conversion 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 per-
formed. 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
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