Mixed Signals’ Approach to Encoding DTV Closed Captions Mixed Signals’ Approach to Encoding DTV...
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Transcript of Mixed Signals’ Approach to Encoding DTV Closed Captions Mixed Signals’ Approach to Encoding DTV...
Mixed Signals’ Approachto Encoding DTV Closed Captions
Mixed Signals’ Approachto Encoding DTV Closed Captions
Line 21Line 21NTSCNTSC
CaptionsCaptions
TranscoderTranscoder DTVCCDTVCCCaptionsCaptions
““Legacy”Legacy”CaptionsCaptions
EIA-608EIA-608
EIA-708EIA-708
Transcoding
Transcoding at Time-of-Air
AdvantagesAdvantages
• Uses existing line 21 captionsUses existing line 21 captions
• Technique currently in use by dozens of DTV Technique currently in use by dozens of DTV broadcastersbroadcasters
• Works with both Standard Definition and HD Works with both Standard Definition and HD programsprograms
• Low costLow cost
Application #1
Time-of-Air EncodingTime-of-Air EncodingFrom D1 SourceFrom D1 Source
Application #2
Time-of-Air EncodingTime-of-Air EncodingFrom Composite SourceFrom Composite Source
DTV 708Closed Caption
Data Server
SerialDigital
Interface
CompositeVideo
Interface
DTVUpconverter
DTVEncoder /Transport
Multiplexer
AnalogVideo In
MonitorVideo Out
AnalogComposite
Video,NTSC or PAL
CompositeVideo
Monitor
Decoded Captions /On-screen Menus
Video
Data
Application #3
HDTV Live or Off-LineHDTV Live or Off-LineEncodingEncoding
SMPTE 333M Interface
DTV Closed Caption Server to ATSC Encoder InterfaceDTV Closed Caption Server to ATSC Encoder Interface
ObjectivesObjectives
• Ensure captions are displayed at exactly the time Ensure captions are displayed at exactly the time intended by caption creatorintended by caption creator
• Guarantee all four NTSC caption bytes are transmitted Guarantee all four NTSC caption bytes are transmitted each pictureeach picture
• Maintain allowed DTVCC transport rate of 9600 bpsMaintain allowed DTVCC transport rate of 9600 bps
• Minimize complexity on part of DTV encoder/transport Minimize complexity on part of DTV encoder/transport multiplexermultiplexer
DTV 708 DTVCC Data Server
DTV 708Features
>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
Thank You!Thank You!
What can we do to helpWhat can we do to helpDTVCC closed captioning?DTVCC closed captioning?