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DTV Closed Captioning Bulletin

DTV Closed Captioning Bulletin. The work of CEA R4.3 WG1 TG2 or Why more examples will make a better standard Charlie Dieterich Sarnoff Corporation Princeton, NJ USA. Specifications are Complex!. MPEG 2 Video is 200+ pages EIA 708 B is 92 pages

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DTV Closed Captioning Bulletin

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  1. DTV Closed Captioning Bulletin The work of CEA R4.3 WG1 TG2 or Why more examples will make a better standard Charlie Dieterich Sarnoff Corporation Princeton, NJ USA

  2. Specifications are Complex! • MPEG 2 Video is 200+ pages • EIA 708 B is 92 pages • Each paragraph can have several compliance points! “The window size is specified in numbers of character rows and character columns for all display formats (16:9, 4:3, etc.). For all display formats, 15 is the maximum character row count and 32 is the maximum character column count.” (EIA 708 B §8.4.6)

  3. How To Improve Implementation Consistency • MPEG Video: • Distribute software that implements all feature of the standard • EIA-708 B: • Provide clear and consistent explanations of features • Provide examples of syntax element use • Provide discussion of options where the standard allows flexibility

  4. Why We Must Act Now... • First encoder implementations only use a subset of features • First decoder implementations must support all mandated features

  5. Why We Must Act Now • Subset works, but... • What if other parts of the Spec are not implemented consistently? • Spec is changed to remove those features or • Spec implementation needs “sunset” provisions to allow faulty implementations to go away

  6. How do we make sure implementations are consistent? • Step 1: • Create a document that includes discussion of technical points • Especially the obscure ones! • Step 2: • Include example streams and desired result • EIA 708 B has some examples • We need lots more examples

  7. Types of Examples • Task Group 1: MPEG transport streams with caption sequences • Most useful for decoder testing • Task Group 2: Syntax sequences with the expected result • Useful for encoder and decoder code development

  8. Plan and Timetable • Develop a list of issues to be clarified • Have several engineers look at each paragraph • Develop a set of standard answers in the form of a CEA Bulletin • Have it done by this summer. • Preliminary versions restricted to Working Group members • August 1st R4.3 Meeting Final Release

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