SDA9280 Datasheet, PDF (14/43 Pages) Siemens Semiconductor Group – ICs for Consumer Electronics

SDA 9280 B22
HP(z)
HCOF
YIN
BP(z)
LP(z)
BCOF
LCOF
Coring
COR
YOUT
UES10247
Figure 4
Luminance Peaking
2.4 Digital Color Transient Improvement (DCTI)
A new digital algorithm is implemented to improve horizontal transitions of the
chrominance signals resulting in a better picture sharpness. A slow change from one
color to another by reason of small chrominance bandwidth is replaced by a steep
transition.
The exact position of a color transition (POS) is calculated by detecting the
corresponding zero transition of the second derivative of both chrominance signals. Low
pass filtering (LPU, LPV, LPUV) is performed to avoid noise sensitivity. The width of a
transition is derived from a threshold detector signal. It indicates an area around the
detected position where the first derivatives of the chrominance signals exceed a
programmable threshold (Ι²C signal: THRESH). The parameter THRESH modifies the
sensitivity of the DCTI-circuit. High values cause that only significant color transitions are
improved. Small color variations remain unchanged. The detected transition width can
be limited by the programmable parameter TRAWID. This parameter performs an
adaption to the input chrominance band width. For signals with small chrominance
bandwidth (e.g. video recorders) the DCTI-performance is optimized using high values
for TRAWID. Input signals with high chrominance bandwidth should be processed with
small values for TRAWID. If standard 4:1:1 video signals are processed, it is
recommended to choose values of the mid range for both parameters THRESH and
TRAWID.
Semiconductor Group
14
1998-02-01