ADV7181 AD [Analog Devices], ADV7181 Datasheet - Page 50

• Manufacturer Part Number: ADV7181
• Description: Multiformat SDTV Video Decoder
• Manufacturer: AD [Analog Devices]

ADV7181B
the recommendation by the International Telecommunications
Union, ITU-R BT.1364. See Figure 34. For more information,
see the ITU website at www.itu.ch.
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 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. Figure 34 and Table 62 show the overall
structure of the data packet.
Table 62. Generic Data Output Packet
Byte
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
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
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 34. Gemstar and CCAP Embedded Data Packet (Generic)
SDID
SECONDARY DATA IDENTIFICATION
COUNT
D[5]
0
1
1
0
0
CS[5]
DATA
Rev. 0 | Page 50 of 96
USER DATA (4 OR 8 WORDS)
D[4]
0
1
1
0
0
CS[4]
word1[7:4]
word1[3:0]
word2[7:4]
word2[3:0]
word3[7:4]
word3[3:0]
word4[7:4]
word4[3:0]
USER DATA
line[3:0]
Entries within the packet are as follows:
•
•
•
•
•
•
•
Table 62 lists the values within a generic data packet that is
output by the ADV7181B in 8-bit format. In 8-bit systems,
Bits D1 and D0 in the data packets are disregarded.
D[3]
0
1
1
0
DC[1]
CS[3]
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) 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.
D[2]
0
1
1
0
DC[0]
CS[2]
OPTIONAL PADDING
D[1]
0
1
1
0
0
0
0
0
0
0
0
0
0
0
0
BYTES
0
1
1
0
0
0
0
0
0
0
0
0
0
D[0]
0
0
CHECK
SUM
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
Description