[Ogg a11y] Milestones 1&2 for video accessibility project
hsivonen at iki.fi
Wed Nov 26 04:34:04 PST 2008
On Nov 26, 2008, at 13:48, ogg.k.ogg.k at googlemail.com wrote:
>> Henri and I had an interesting conversation about the charset
>> specification in OggText and the sentence about "charset implies
>> directionality". It seems I have looked at the wrong documents for
> I read "charset" originally as "set of characters used by the text we
> are looking at", etc, a range of code points usually, but after
> at the message headers you specify for, eg, language, I also see
> a "charset=utf-8", so I think I may have misunderstood this.
charset in the IETF sense means a character encoding--not a set of
> Unicode defines directionality for *some* ranges, in two "strengths".
> This is what I use (through Pango). The directionality that can be set
> in a Kate stream is used as a weak default only.
> Now, a script may imply a default directionality too. Languages map in
> a fuzzy way to scripts, so you could get a default directionality
> from the
> language, I think.
> So, directionality could be Unicode based if known from the text we're
> parsing, then default to either script or stream declared
> directionality if
> not known.
Markup-like formats should provide functionality corresponding to the
dir attribute in HTML. Non-markup-like text formats should use LEFT-TO-
RIGHT MARK and RIGHT-TO-LEFT mark to give the dominant direction of a
block of text.
I think text track formats in Ogg shouldn't specify their own
directionality handling any further that HTML does and should defer to http://unicode.org/reports/tr9/
for the rest. Whether it's necessary to have exactly as much format-
level directionality control as HTML, I'm not so sure about. (HTML has
markup for declaring the dominant direction of a block (dir='...' on
anything but <bdo>) and markup for overriding the intrinsic
directionality of characters (<bdo dir='...'>).)
> Could there be cases where one might want to override the
> directionality (eg, render English r2l or Arabic l2r ?)
I take it that you mean overriding the intrinsic directionality of
characters. HTML, CSS and W3C TimedText provide this, but *I* can't
think of legitimate captioning use cases off the top of my head.
hsivonen at iki.fi
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