ADV7181B
Rev. B | Page 19 of 100
STANDARD DEFINITION PROCESSOR (SDP)
DIGITIZED CVBS
DIGITIZED Y (YC)
VIDEO DATA
OUTPUT
STANDARD DEFINITION PROCESSOR
DIGITIZED CVBS
DIGITIZED C (YC)
MACROVISION
DETECTION
VBI DATA
RECOVERY
STANDARD
AUTODETECTION
LUMA
FILTER
LUMA
DIGITAL
FINE
CLAMP
GAIN
CONTROL
LUMA
RESAMPLE
LUMA
2D COMB
SLLC
CONTROL
CHROMA
FILTER
CHROMA
DEMOD
F
SC
RECOVERY
CHROMA
DIGITAL
FINE
CLAMP
GAIN
CONTROL
CHROMA
RESAMPLE
CHROMA
2D COMB
SYNC
EXTRACT
LINE
LENGTH
PREDICTOR
RESAMPLE
CONTROL
AV
CODE
INSERTION
MEASUREMENT
BLOCK (
≥
I
2
C)
VIDEO DATA
PROCESSING
BLOCK
04984-007
Figure 7. Block Diagram of the Standard Definition Processor
A block diagram of the ADV7181B’s standard definition
processor (SDP) is shown in Figure 7.
The ADV7181B can handle standard definition video in CVBS,
YC, and YPrPb formats. It can be divided into a luminance and
chrominance path. If the input video is of a composite type
(CVBS), both processing paths are fed with the CVBS input.
SD LUMA PATH
The input signal is processed by the following blocks:
•
Digital Fine Clamp. This block uses a high precision
algorithm to clamp the video signal.
•
Luma Filter Block. This block contains a luma decimation
filter (YAA) with a fixed response, and some shaping filters
(YSH) that have selectable responses.
•
Luma Gain Control. The automatic gain control (AGC)
can operate on a variety of different modes, including gain
based on the depth of the horizontal sync pulse, peak white
mode, and fixed manual gain.
•
Luma Resample. To correct for line-length errors as well as
dynamic line-length changes, the data is digitally
resampled.
•
Luma 2D Comb. The two-dimensional comb filter
provides YC separation.
•
AV Code Insertion. At this point, the decoded luma (Y)
signal is merged with the retrieved chroma values. AV
codes (as per ITU-R BT.656) can be inserted.
SD CHROMA PATH
The input signal is processed by the following blocks:
•
Digital Fine Clamp. This block uses a high precision
algorithm to clamp the video signal.
•
Chroma Demodulation. This block uses a color subcarrier
(F
SC
) recovery unit to regenerate the color subcarrier for
any modulated chroma scheme. The demodulation block
then performs an AM demodulation for PAL and NTSC,
and an FM demodulation for SECAM.
•
Chroma Filter Block. This block contains a chroma
decimation filter (CAA) with a fixed response, and some
shaping filters (CSH) that have selectable responses.
•
Gain Control. Automatic gain control (AGC) can operate
on several different modes, including gain based on the
color subcarrier’s amplitude, gain based on the depth of the
horizontal sync pulse on the luma channel, or fixed manual
gain.
•
Chroma Resample. The chroma data is digitally resampled
to keep it perfectly aligned with the luma data. The
resampling is performed to correct for static and dynamic
line-length errors of the incoming video signal.
•
Chroma 2D Comb. The two-dimensional, 5-line,
superadaptive comb filter provides high quality YC
separation in case the input signal is CVBS.
•
AV Code Insertion. At this point, the demodulated chroma
(Cr and Cb) signal is merged with the retrieved luma
values. AV codes (as per ITU-R BT.656) can be inserted.
