mixed signals’ approach to encoding dtv closed captions
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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 - PowerPoint PPT PresentationTRANSCRIPT
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?