W3C home > Mailing lists > Public > public-media-fragment@w3.org > February 2009

useful units (ACTION-27)

From: Yves Lafon <ylafon@w3.org>
Date: Mon, 2 Feb 2009 10:40:01 -0500 (EST)
To: public-media-fragment@w3.org
Message-ID: <Pine.LNX.4.64.0902020912130.13725@ubzre.j3.bet>

During our last f2f, we discussed the applicability of some units and the 
need to create a list for them.
We have two axis, the temporal axis, and the display axis.

The temporal axis is currently debated (see the discussions on the list 
regarding seconds (as real numbers) vs frame-oriented units.

For the display axis, we rule out the units relative to the document it 
would be displayed in (as the server has no way to know the document the 
unit is relative to). So it leaves us with units relative to the 
characteristics of the video/image presented:

* Pixels
* percentages (as percentage of width and height)

It would be interesting also to define only one axis (x or y), and define 
an aspect ratio, like aspect(16:9), in that case the aspect ratio could 
be an relative unit (relative to the other unit in use).

* in, cm when the media gives the information about the relationship
   between pixels and in/cm so in general not applicable. Do we want them ?

All other units used in CSS (like pt, pc, em) are dependant on the 
definition of pt, and linked in CSS2 to cm/in (as 1pt = 1/72 in), but a 
fragment might be applicable to renderer not using this default, so I 
would avoid those.

-- 
Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves
Received on Monday, 2 February 2009 15:40:14 GMT

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