adv7188 Analog Devices, Inc., adv7188 Datasheet - Page 70

• Manufacturer Part Number: adv7188
• Description: Multiformat Sdtv Video Decoder With Fast Switch Overlay Support
• Manufacturer: Analog Devices, Inc.

ADV7188
The format of the data packet depends on the following criteria:
•
•
•
Data packets are output if the corresponding enable bit is
set (see the GDECEL [15:0], Gemstar Decoding Even Lines,
Address 0x48 [7:0], Address 0x49 [7:0] and the GDECOL [15:0],
Gemstar Decoding Odd Lines, Address 0x4A [7:0], Address
0x4B [7:0] sections) and the decoder detects the presence of
data. This means that for video lines where no data has been
decoded, no data packet is output, even if the corresponding line
enable bit is set.
Each data packet starts immediately after the EAV code of the
preceding line. Figure 43 and Table 84 show the overall
structure of the data packet.
Table 84. Generic Data Output Packet
Byte
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Transmission is Gemstar 1× or Gemstar 2×.
Data is output in 8-bit or 4-bit format (see the GDECAD,
Gemstar Decode Ancillary Data Format, Address 0x4C [0]
section).
Data is closed captioning (CC) or Gemstar compatible.
D [9]
0
1
1
0
EP
EP
EP
EP
EP
EP
EP
EP
EP
EP
CS[8]
PREAMBLE FOR ANCILLARY DATA
00
D [8]
0
1
1
1
EP
EP
EP
EP
EP
EP
EP
EP
EP
EP
CS [8]
DATA IDENTIFICATION
FF
D [7]
0
1
1
0
EF
0
0
0
0
0
0
0
0
0
CS [7]
FF
DID
D [6]
0
1
1
1
2X
0
0
0
0
0
0
0
0
0
CS [6]
Figure 43. Gemstar and CC Embedded Data Packet (Generic)
SDID
SECONDARY DATA IDENTIFICATION
COUNT
DATA
D [5]
0
1
1
0
0
CS [5]
USER DATA (FOUR OR EIGHT WORDS)
Rev. A | Page 70 of 112
D [4]
0
1
1
0
0
CS [4]
USER DATA
word1 [7:4]
word1 [3:0]
word2 [7:4]
word2 [3:0]
word3 [7:4]
word3 [3:0]
word4 [7:4]
word4 [3:0]
line [3:0]
Entries within the packet are as follows:
•
•
•
•
•
•
•
Table 84 lists the values within a generic data packet that are
output by the ADV7188 in 10-bit format.
D [3]
0
1
1
0
DC [1]
CS [3]
A fixed preamble sequence of 0x00, 0xFF, and 0xFF.
The data identification word (DID) (10-bit value), the
value of which is 0x140 for a Gemstar or CC data packet.
The secondary data identification word (SDID), which
contains information about the video line from which data
was retrieved, whether the Gemstar transmission was of 1×
or 2× format, and whether it was retrieved from an even or
odd field.
The data count byte, which provides the number of user
data-words that follow.
User data section. This contains the user data, which can
be four or eight words of data.
Optional padding to ensure that the length of the user
data-word section of a packet is a multiple of four bytes
(requirement, as set in ITU-R BT.1364).
Checksum byte. This contains the checksum of the packet.
D [2]
0
1
1
0
DC [0]
CS [2]
OPTIONAL PADDING
BYTES
D [1]
0
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
D [0]
0
0
0
0
0
0
0
0
0
0
0
CHECKSUM
Description
Fixed preamble
Fixed preamble
Fixed preamble
DID
SDID
Data count (DC)
User data-words
User data-words
User data-words
User data-words
User data-words
User data-words
User data-words
User data-words
Checksum