Sync Processing; Vbi Data Recovery; General Setup - Analog Devices ADV7181BCP Manual

ADV7181B

SYNC PROCESSING

The ADV7181B extracts syncs embedded in the video data
stream. There is currently no support for external HS/VS
inputs. The sync extraction has been optimized to support
imperfect video sources such as VCRs with head switches. The
actual algorithm used employs a coarse detection based on a
threshold crossing followed by a more detailed detection using
an adaptive interpolation algorithm. The raw sync information
is sent to a line-length measurement and prediction block. The
output of this is then used to drive the digital resampling
section to ensure that the ADV7181B outputs 720 active pixels
per line.
The sync processing on the ADV7181B also includes the
following specialized postprocessing blocks that filter and
condition the raw sync information retrieved from the digitized
analog video:
•
Vsync Processor. This block provides extra filtering of the
detected Vsyncs to improve vertical lock.
•
Hsync Processor. The Hsync processor is designed to filter
incoming Hsyncs that are corrupted by noise, providing
much improved performance for video signals with stable
time base but poor SNR.

VBI DATA RECOVERY

The ADV7181B can retrieve the following information from the
input video:
•
Wide-screen signaling (WSS)
•
Copy generation management system (CGMS)
•
Closed captioning (CC)
•
Macrovision protection presence
•
EDTV data
•
Gemstar-compatible data slicing
The ADV7181B is also capable of automatically detecting the
incoming video standard with respect to
•
Color subcarrier frequency
•
Field rate
•
Line rate
The ADV7181B can configure itself to support PAL-B/G/H/I/D,
PAL-M/N, PAL-combination N, NTSC-M, NTSC-J, SECAM
50 Hz/60 Hz, NTSC4.43, and PAL60.
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GENERAL SETUP

Video Standard Selection
The VID_SEL[3:0] register allows the user to force the digital
core into a specific video standard. Under normal circumstances,
this should not be necessary. The VID_SEL[3:0] bits default to
an autodetection mode that supports PAL, NTSC, SECAM, and
variants thereof. The Autodetection of SD Modes section
provides more information on the autodetection system.
Autodetection of SD Modes
To guide the autodetect system of the ADV7181B, individual
enable bits are provided for each of the supported video
standards. Setting the relevant bit to 0 inhibits the standard
from being detected automatically. Instead, the system picks the
closest of the remaining enabled standards. The results of the
autodetection block can be read back via the status registers. See
the Global Status Registers section for more information.
VID_SEL[3:0]Address 0x00[7:4]
Table 17. VID_SEL Function
VID_SEL[3:0]
0000 (default)
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
AD_SEC525_EN Enable Autodetection of SECAM 525
Line Video, Address 0x07 [7]
Setting AD_SEC525_EN to 0 (default) disables the
autodetection of a 525-line system with a SECAM style, FM-
modulated color component.
Setting AD_SEC525_EN to 1 enables the detection.
Rev. B | Page 20 of 100
Description
Autodetect (PAL BGHID) <–> NTSC J
(no pedestal), SECAM.
Autodetect (PAL BGHID) <–> NTSC M
(pedestal), SECAM.
Autodetect (PAL N) (pedestal) <–> NTSC J
(no pedestal), SECAM.
Autodetect (PAL N) (pedestal) <–> NTSC M
(pedestal), SECAM.
NTSC J (1).
NTSC M (1).
PAL60.
NTSC 4.43 (1).
PAL BGHID.
PAL N = PAL BGHID (with pedestal).
PAL M (without pedestal).
PAL M.
PAL-Combination N.
PAL-Combination N (with pedestal).
SECAM.
SECAM (with pedestal).