ADV7183A_15 Datasheet, PDF (55/104 Pages) Analog Devices – Multiformat SDTV Video Decoder

• GDECAD configures the way in which data is embedded
in the video data stream.
The recovered data is not available through I²C, but is being
inserted into the horizontal blanking period of an ITU-R
BT656-compatible data stream. The data format is intended to
comply with the recommendation by the International Tele-
communications Union, ITU-R BT.1364. See Figure 35. For
more information, see the ITU website at www.itu.ch
The format of the data packet depends on the following criteria:
• Transmission is 1× or 2×.
• Data is output in 8-bit or 4-bit format (see the description
of the GDECAD Gemstar Decode Ancillary Data Format,
Address 0x4C [0] bit).
• Data is Closed Caption (CCAP) or Gemstar-compatible.
Data packets are output if the corresponding enable bit is set
(see the GDECEL and GDECOL descriptions), and if 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. See Figure 35 and Table 150, which show the
overall structure of the data packet.
ADV7183A
Entries within the packet are as follows:
• Fixed preamble sequence of 0x00, 0xFF, 0xFF.
• Data identification word (DID). The value for the DID
marking a Gemstar or CCAP data packet is 0x140 (10-bit
value).
• 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.
• Data count byte, giving the number of user data-words that
follow.
• User data section.
• 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.
Table 150 lists the values within a generic data packet that is
output by the ADV7183A in 8-bit format. In 8-bit systems,
Bits D1 and D0 in the data packets are disregarded.
DATA IDENTIFICATION SECONDARY DATA IDENTIFICATION
00
FF
FF
DID
SDID
DATA
COUNT
USER DATA
OPTIONAL PADDING CHECK
BYTES
SUM
PREAMBLE FOR ANCILLARY DATA
USER DATA (4 OR 8 WORDS)
Figure 35. Gemstar and CCAP Embedded Data Packet (Generic)
Table 150. Generic Data Output Packet
Byte D[9]
D[8] D[7] D[6] D[5] D[4] D[3]
D[2]
D[1] D[0] Description
0
0
0
0
0
0
0
0
0
0
0
Fixed preamble
1
1
1
1
1
1
1
1
1
1
1
Fixed preamble
2
1
1
1
1
1
1
1
1
1
1
Fixed preamble
3
0
1
0
1
0
0
0
0
0
0
DID
4
!EP
EP
EF
2X
line[3:0]
0
0
SDID
5
!EP
EP
0
0
0
0
DC[1] DC[0] 0
0
Data count (DC)
6
!EP
EP
0
0
word1[7:4]
0
0
User data-words
7
!EP
EP
0
0
word1[3:0]
0
0
User data-words
8
!EP
EP
0
0
word2[7:4]
0
0
User data-words
9
!EP
EP
0
0
word2[3:0]
0
0
User data-words
10
!EP
EP
0
0
word3[7:4]
0
0
User data-words
11
!EP
EP
0
0
word3[3:0]
0
0
User data-words
12
!EP
EP
0
0
word4[7:4]
0
0
User data-words
13
!EP
EP
0
0
word4[3:0]
0
0
User data-words
14
!CS[8] CS[8] CS[7] CS[6] CS[5] CS[4] CS[3] CS[2] 0
0
Checksum
Rev. B | Page 55 of 104