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8083XDS-AD Analog and SD-SDI XDS Encoder
Field 1
CC1
Primary Synchronous Caption Service
CC2
Special Non-synchronous Use Captions
T1
First Text Service
T2
Second Text Service
IRE
H Sync
Color Burst
50
25
0
-40
Page 1-2
The separate data streams are independent of each other in content.
Within each field, the streams are time-multiplexed. Control codes are
transmitted to announce the transition to a different stream. Home viewers
may generally select which data stream to display with their caption
decoders.
The primary Synchronous Caption Service (CC1) is primary language
captioning data that must be in sync with the sound.
Synchronous Caption Service (CC3) is an alternate captioning data
channel in sync with the sound, usually used for a second language.
The special Non-Synchronous channels (CC2, CC4) carry data that is
intended to augment information carried in the program and is not
necessarily in sync with the sound.
The four text services are used to carry general text information that may
not be related to the program content. Text stream T2 is often reserved to
carry URL data for WebTV applications.
Extended Data Service stream contains information about the program
such as program title, length, and V-Chip-compatible program rating
information.
Clock Run-In
Start Bits
S1
S2
S3
b0
Figure 1-1: Typical Line 21 Closed Caption Signal
Revision 1.0.2
Field 2
CC3 Secondary Synchronous Caption Service
CC4 Special Non-synchronous Use Captions
T3
Third Text Service
T4
Fourth Text Service
XDS Extended Data Services
Character One
b1
b2
b3
b4
b5
b6
P1
b0
The Secondary
Character Two
b1
b2
b3
b4
b5
b6
P2
OVERVIEW
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