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[ttml2] Appendix P is overly constrained and does not represent current best practice

From: Michael A Dolan via GitHub <sysbot+gh@w3.org>
Date: Mon, 05 Jun 2017 17:52:36 +0000
To: public-tt@w3.org
Message-ID: <issues.opened-233662037-1496685154-sysbot+gh@w3.org>
mikedo has just created a new issue for https://github.com/w3c/ttml2:

== Appendix P is overly constrained and does not represent current best practice ==
Streaming TTML today consists of short complete TTML documents, not document fragments.  If we want an Appendix like this it should better document how, e.g. FFMPEG, actually works today, not just a theoretical fragmenting mechanism as its example.

And, if we for some reason want to keep this fragmentation example, then the definition of the properties of a progressively decodable document are over constrained, including:

1. the constraint: "does not require dereferencing (and subsequent loading) of any resources other than TTML Content (i.e., no embedded URIs);" is overly constraining and does not consider bundled resources such as the ISO BMFF sample packaging of URI image resources defined in ISO 14496-30.

2. it is not clear why this constraint is necessary: "does not support alternative content forms (e.g., different language, graphics formats, time bases) in a single document;", e.g. what about this example model makes it unable to easily handle alternative content, e.g. tts:altText?

And, overall, why is this definition of "progressively decodable" at odds with IMSC1 6.7.2?

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/384 using your GitHub account
Received on Monday, 5 June 2017 17:52:42 UTC

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