MSTs ITV Delivery System

1
Mixed Signals Approach to Encoding DTV Closed
Captions
2
Transcoding
EIA-708
EIA-608
DTVCC Captions
Transcoder
Line 21 NTSC Captions
Legacy Captions
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Transcoding at Time-of-Air

• Advantages
• Uses existing line 21 captions
• Technique currently in use by dozens of DTV
  broadcasters
• Works with both Standard Definition and HD
  programs
• Low cost

4
Application 1
Time-of-Air Encoding From D1 Source
5
Application 2
Time-of-Air Encoding From Composite Source
6
Application 3
HDTV Live or Off-Line Encoding
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SMPTE 333M Interface

• DTV Closed Caption Server to ATSC Encoder
  Interface
• Objectives
• Ensure captions are displayed at exactly the time
  intended by caption creator
• Guarantee all four NTSC caption bytes are
  transmitted each picture
• Maintain allowed DTVCC transport rate of 9600 bps
• Minimize complexity on part of DTV
  encoder/transport multiplexer

8
DTV 708 DTVCC Data Server

• DTV 708
• Features
• Built-in closed caption decoder, LTC time code
  reader, bidirectional GPI
• Easy to use on-screen menus
• Optional modem, LAN interface
• Able to read caption files including emerging
  native EIA-708 files

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Thank You! What can we do to help DTVCC closed
captioning?