Datasheet

Functional Description
8
May 2006SLES043A
An adaptive 4-line comb filter separates UV from Y based on the unique property of color phase shift from line
to line. Chroma is remodulated through another quadrature modulator and subtracted from the line-delayed
composite video to generate luma. This form of Y/C separation is completely complementary and thus loses
no information. However, in some applications, it is desirable to limit the U/V bandwidth to avoid crosstalk. In
that case, notch filters can be turned on. To accommodate some viewing preferences, a peaking filter is also
available in the luma path. Contrast, brightness, hue, saturation, and sharpness are programmable via I
2
C.
The Y/C separation is bypassed for S-video input. For S-video, the remodulation path is disabled. Since Y and
C are already separated at the inputs, the only requirement is to digitize them and enable the same processing
as the composite signal after Y/C separation.
Line
Delay
−
Peaking
Quadrature
Modulation
Quadrature
Demodulation
Notch
Filter
Color
LPF
3- or 4-Line
Adaptive
Comb
Filter
Burst
Accumulator
(V)
Notch
Filter
Notch
Filter
Notch
Filter
Delay
Contrast
Brightness
Saturation
Adjust
Delay
V
Y
U
UV
Y
Burst
Accumulator
(U)
Delay
Color
LPF
Composite
+Delay
X
Gain Factor
Bandpass
Peak
Detector
Composite
U
V
Figure 3−1. Composite Processing Block Diagram
3.6 Adaptive Comb Filtering
Y/C separation can be performed using adaptive 4-line (3-H delay), fixed 3-line, fixed 2-line comb filters, or
a chroma trap filter. Characteristics of 4-line and 3-line comb filters are shown in Figure 3−2.