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RE: Some comments on the requirements

From: <Johnb@screen.subtitling.com>
Date: Wed, 5 Feb 2003 11:44:40 -0000
Message-ID: <11E58A66B922D511AFB600A0244A722E093EAD@NTMAIL>
To: glenn@xfsi.com, bert@w3.org
Cc: public-tt@w3.org

Bert Bos wrote some comments on the requirements...

> 2 Have a valid XML representation

> Apart from the fact that this contradicts the first requirement
> ("simple and easy"), I think that limiting the syntax up front is
> not very useful. Especially so, because of the timed-text formats
> (and proposed formats) that I have seen so far, those that were
> not based on XML were by far the most elegant. (E.g, those of
> Quicktime and Mplayer.)

Have to agree - an XML representation might bring advantages - but it should
not be a pre-requisite. Would it be possible to have an XML representation
(with external documents?) that has a streamable format that is more
efficient and elegant than its XML representation?

> 8 Allow the language of the text to be identified using xml:lang

> A corollary of the previous comment. The language should indeed be
> identified somehow, but it could be by other means than XML.
> Indeed, it could be outside the document itself, e.g., in an HTTP
> header.

If the representation is XML - then XML should be fully utilised - but TT
should IMHO support multiple language streams.

> 11 Have a default UNICODE font

> Is it really a requirement to have a standard font? What font
> would that be? Arial? Maybe the intention was to require that the
> format supports all Unicode characters, rather than a specific font?

Somewhere in the charter it says that font is something to be left out of
TT. TT should require support for Unicode **characters**.

> 18 Allow motion [...]

> I think this requirements makes the format too complicated and
> makes it approach SMIL and SVG too much. Those formats already
> exist. What's needed here is something simple, as requirement 1 says.

Could motion be part of the style rather than the text?

> 19 Use SVG, MathML, XHTML or other language for complex font displays

> I agree with this requirement as such (as I said in the previous
> comment), but its appearance here seem to suggest something more,
> viz., that UAs that support timed text also have to support SVG,
> MathML and XHTML. That seems rather pointless to me. If the UA
> already supports those three, then there is no need anymore for
> timed text. I thought the purpose of timed text was precisely to
> have something that is simpler than those formats and still does
> the job in 95% of the cases.

Absolutely, though it would be nice to be able to transfer glyphs that have
no unicode representation by some mechanism within TT (e.g. trademarks and
logos). Could this be by private data inclusion? Reference to external
streams?

> 22 Adopt SMIL 2.0 as a base language.

> Like requirement 2 ("XML"), this puts too many a priori
> restrictions on the format. Besides, unless you subset SMIL so
> much that it doesn't look like SMIL anymore, it would not be
> simple and easy, as required by requirement 1.

AFAIK SMIL also doesn't allow the implementation of all of the buffering and
timing models (outlined by Glenn A. Adams) that are probably required.

regards 

	John Birch

The views and opinions expressed are the author's own and do not necessarily
reflect the views and opinions of Screen Subtitling Systems Limited.
Received on Wednesday, 5 February 2003 06:35:57 GMT

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