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Mixed Signals’ Approach to Encoding DTV Closed Captions

Mixed Signals’ Approach to Encoding DTV Closed Captions. Transcoding. EIA-708. EIA-608. DTVCC Captions. Transcoder. Line 21 NTSC Captions. “Legacy” Captions. Transcoding at Time-of-Air. Advantages Uses existing line 21 captions

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Mixed Signals’ Approach to Encoding DTV Closed Captions

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  1. Mixed Signals’ Approach to Encoding DTV Closed Captions

  2. Transcoding EIA-708 EIA-608 DTVCC Captions Transcoder Line 21 NTSC Captions “Legacy” Captions

  3. 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

  7. 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

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

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