[whatwg] on codecs in a 'video' tag.

Bjoern Hoehrmann derhoermi at gmx.net
Tue Mar 27 09:48:27 PDT 2007

* James Graham wrote:
>The pain of having things that "everyone knows" are needed to make a useful HTML 
>reading device but are not documented as such. A specification is documentation 
>both of the language and what needs to be done to implement a UA to read it and 
>I see no reason to arbitarily limit the scope to those parts that can be 
>expressed in pure markup.

Documentation would be, for example, "As of 2007, popular image formats
used in conjunction with HTML documents include GIF, JPEG, ICO and PNG";
specifications, that is, the normative parts of it, define what is
necessary and sufficient to conform to the specification. What you, or
Anne for that matter, are proposing is that certain applications that
implement HTML should be non-conforming if they do not support GIF, or
certain other formats.

>In the case of image formats it's probably not overwhelmingly important (only 
>because "everyone knows" what is needed; in the case of audio and video I think 
>it is very important) but I can't see how it's harmful in the way you suggest.

Then I suggest you write the specification text using a sufficiently
narrow conformance class and use MUST instead of SHOULD, complete with
normative references and such, making it sufficiently robust to with-
stand various questions one might ask, like

  * do I have to implement those features of JPEG that are not commonly
    implemented in popular open source JPEG libraries?

  * is it sufficient to support display of GIF images by allowing users
    to configure an external application that would be launched on re-

  * where exactly (img, object, video, iframe, favicons, inline SVG) is
    such support required?

  * does IE6' implementation of PNG conform to your requirements?

  * when do I have to animate animated GIF images, and what should be
    done if I may and do not want to animate them, for example, in the
    bookmark list where favicons would be shown?

It is okay, of course, if you make certain things implementation-
defined, you can than judge how close you are to your goal to avoid
having the "everyone knows" bits in your specification. For the first
item you might start with <http://www.w3.org/TR/SVGMobile12/jpeg.html>.
Then tell us why you did not write some useful test cases instead.

>In any case this discussion is probably not very useful.

Well, more useful than having the "HTML specification" mandate some
unqualified level of GIF support.
Björn Höhrmann · mailto:bjoern at hoehrmann.de · http://bjoern.hoehrmann.de
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