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 –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)

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

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

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

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

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

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