[whatwg] Introduction of media accessibility features

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Sun Apr 11 17:47:33 PDT 2010

On Mon, Apr 12, 2010 at 7:59 AM, Jonas Sicking <jonas at sicking.cc> wrote:
> On Sun, Apr 11, 2010 at 5:30 AM, Silvia Pfeiffer
> <silviapfeiffer1 at gmail.com> wrote:
> f>> Is it expected that all of TTML will be required? The proposal suggests
>>> 'starting with the simplest profile', being the transformation profile. Does
>>> this mean only the transformation profile is needed to provide subtitle
>>> features equivalent to SRT?
>> That is also something that still has to be discussed further. Initial
>> feedback from browser vendors was that the full TTML spec is too
>> complicated and too much to support from the start. Thus, the
>> implementation path with the TTML profiles is being suggested.
>> However, it is as yet unclear if there should be a native parsing
>> implementation of TTML implemented in browsers or simply a mapping of
>> TTML markup to HTML/CSS/JavaScript. My gut feeling is that the latter
>> would be easier, in particular since such a mapping has been started
>> already with Philippe's implementation, see
>> http://www.w3.org/2009/02/ThisIsCoffee.html . The mapping would need
>> to be documented.
> Personally I'm concerned that if we start heading down the TTML path,
> browsers are ultimately going to end up forced to implement the whole
> thing. Useful parts as well as parts less so. We see this time and
> again where if we implement part of a spec we end up forced to
> implement the whole thing.
> Things like test suites, blogging advocates, authoring tools, etc
> often means that for marketing reasons we're forced to implement much
> more than we'd like. And much more than is useful. This is why spec
> writing is a big responseibility, every feature has a large cost and
> means that implementors will be working on implementing that feature
> instead of something else.

Understood. But what is actually the cost of implementing all of TTML?
The features in TTML all map onto existing Web technology, so all it
takes is a bit more parsing code over time. And if we chose not to
implement TTML, we will have to eventually support some other format
that provides formatting and positioning capabilities, seeing how the
legal landscape has evolved for traditional media (e.g. TV, set-top
box technology). Since TTML was originally developed to be the
exchange format for all such formats, it should have a sensible set of
features for this space. So, I personally think it's not a bad choice
for the purpose. Which other format did you have in mind to replace


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