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Re: useful units (ACTION-27)

From: Yves Lafon <ylafon@w3.org>
Date: Tue, 3 Feb 2009 08:24:27 -0500 (EST)
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
cc: public-media-fragment@w3.org
Message-ID: <Pine.LNX.4.64.0902030823400.17743@ubzre.j3.bet>

On Tue, 3 Feb 2009, Silvia Pfeiffer wrote:

> 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.

I agree, aspect ration should be one particular transformation, like a 
fixed crop based on the center of the frame, with no other confusing 
options (if it is at all needed).

> Cheers,
> Silvia.
>
>
>>>
>>> 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
>>
>>
>

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

         ~~Yves
Received on Tuesday, 3 February 2009 13:24:35 GMT

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