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

Re: useful units (ACTION-27)

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Tue, 3 Feb 2009 22:14:08 +1100
Message-ID: <2c0e02830902030314m4b35da45t4e44bc6ae76d9efb@mail.gmail.com>
To: Yves Lafon <ylafon@w3.org>
Cc: public-media-fragment@w3.org

On Tue, Feb 3, 2009 at 9:09 PM, Yves Lafon <ylafon@w3.org> wrote:
> On Tue, 3 Feb 2009, Silvia Pfeiffer wrote:
>> I agree with the use of pixels and cm for spatial fragment specifications.
>> Maybe points, too, but I don't really see that as necessary.
> Meaning you are against using percentages ?

Oh no, no. I am happy for them, too. As long as it is clear what they
are calculated against. It should be the explicit or implicit width
and height of the video viewport.

I would not want to deal with one dimension and an aspect ratio,
though, because it becomes rather confusing.The aspect ratio may be
fixed, while the width and height of the video change, which will
resultin a black letterbox, which totally destroys all measurments
that try and stay relative to an aspect ratio.


>> On Tue, Feb 3, 2009 at 2:40 AM, Yves Lafon <ylafon@w3.org> wrote:
>>> 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
> --
> Baroula que barouleras, au tiéu toujou t'entourneras.
>        ~~Yves
Received on Tuesday, 3 February 2009 11:14:43 UTC

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