Re: [blink-dev] WebVTT vs TTML Features

On Dec 9, 2013, at 11:31 , Glenn Adams <glenn@chromium.org> wrote:

> The real requirement from TTML, and the major source of disadvantage for the current WebVTT approach is that it forces the distribution of information that applies to a WebVTT "document". In essence, it prevents a WebVTT "document" from being self-contained.

The provision of in-line style sheets in the file header is under active discussion and does not seem to be problematic.

> Another significant design difference between TTML and WebVTT comes into play here as well: TTML was designed for smart authoring systems and dumb clients, while WebVTT was designed for dumb authoring systems and smart clients. 

I don’t think this can possibly be true.  The client-side implementation of VTT is vastly simpler than TTML, and indeed does not require profiles, or complicated specification.

> That these design choices are very different will continue to stymy efforts to unify the two intentionally different expressions of timed text content.

Since TTML’s initial “raison d’etre” was as a flexible authoring system, this would seem to be a problem.  I doubt that it’s true.


I also would love to see a report of TTML as *used*, what features are actually used, and so on. It would really help, and perhaps help inform the profile definitions that are currently underway.

David Singer
Multimedia and Software Standards, Apple Inc.

Received on Tuesday, 10 December 2013 18:50:55 UTC