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Re: Comments CSS For TV (+ attachment)

From: Tantek Çelik <tantek@cs.stanford.edu>
Date: Thu, 13 Jun 2002 21:25:43 -0700
To: "Zdepski, Joel" <JZdepski@opentv.com>, www-style@w3.org
Cc: Sean Hayes <shayes@microsoft.com>, "Glenn A. Adams" <glenn@xfsi.com>, Hċkon Wium Lie <howcome@opera.com>
Message-id: <B92EBE57.E4A6%tantek@cs.stanford.edu>

Joel,

Thank you very much for your review of the CSS TV Profile 1.0 Last Call
Working Draft, and for your comments.

Specifically, the document you enclosed stated:

> There is, however, one small change that we believe will be necessary to
> achieve adequate performance on todayıs set-top boxes.  This change has to do
> with the properties from CSS-3ıs Color Profile that are required and those
> that are optional.   It has been our experience that content designers demand
> the ability to specify transparency on a per-color basis rather than on a
> per-element basis.  CSS-3ıs RGBA would satisfy this demand, yet it is excluded
> from  the CSS TV Profile 1.0, while support for CSS3ıs opacity property is
> required.  It has been our experience that content providers would not
> typically be satisfied with this single transparency attribute; it appears to
> us to be impossible to obtain adequate performance if this property is used in
> conjunction with RGBA on most set-top boxes; and that some lower end set-top
> boxes that are very important in todayıs market cannot support the opacity
> property while they can support at least one semi-transparent color in their
> hardware palette.

From this, we (the CSS working group) gathered that you proposed adding the
"rgba()" color value from the CSS3 Color Module to the CSS TV Profile 1.0.

I agree with your proposal, as does co-editor Glenn Adams.

I brought your feedback to the CSS Working Group, and the Working Group
accepted your proposed change at our teleconference dated 10 June 2002.[1]

The "rgba()" color value will be added to the CR draft of the CSS TV Profile
1.0.

Regarding the difficulty to obtain adequate performance of the
implementation of the "opacity" property on some (or perhaps today most)
set-top boxes, I agree with your statement, and that is specifically why the
opacity property in the CSS3 Color module [2] takes an optional
<priority-index> value.  The intent of this is to take advantage of hardware
acceleration for opacity rendering on boxes that have that capability.

Additionally, it is implied (but not explicitly stated) in the conformance
section of CSS TV Profile 1.0 [3] that it is acceptable for an
implementation to ignore the opacity property due to the [performance, video
etc.] limitations of a particular device:

"The inability of a TV-UA to implement part of this specification due to the
limitations of a particular device (e.g., a TV-UA cannot render colors on a
monochrome monitor or page) SHALL NOT imply non-conformance."

I believe this portion of the conformance statement is sufficient.  If you
think an explicit statement about opacity is needed, please let us know.

Thanks again for your feedback,

Tantek

[1] W3C Member Only Link
 http://lists.w3.org/Archives/Member/w3c-css-wg/2002AprJun/0239.html

[2]
 http://www.w3.org/TR/css3-color/#transparency

[3]
 http://www.w3.org/TR/css-tv#section-conformance

---------------------------------------------------------------------------
Tantek Çelik                                         tantek@cs.stanford.edu
Microsoft Corporation                                 tantekc@microsoft.com
W3C CSS working group representative, W3C HTML working group alternate
---------------------------------------------------------------------------


On 6/7/02 2:28 AM, "Zdepski, Joel    (by way of Bert Bos <bert@w3.org>)"
<JZdepski@opentv.com> wrote:

> Attached is a document with comments to the Draft CSS for TV
> specification recently posted for public comment.
> My company has a lot of experience deploying software to STB's in both
> Pay and Free-to-air television distribution networks.
> The attached comment comes out of the difference in graphics
> capabilities between computers and STB's with advanced graphics, and
> the mass market STB's.   Please contact me if there are any questions
> in our document.
> 
> Regards
> 
> Joel Zdepski
> 
> -----------------------------------------------------------------------
> ---- Joel Zdepski, Ph.D.
> VP, Office of the CTO
> OpenTV, Corp.
> 401 East Middlefield Rd.
> Mountain View  CA, 94043
> Tel: +1 650 429-5592
> Mob: +1 650 575-5502  <--- NEW MOBILE NUMBER
> Fax: +1 650 237-0822
> E-mail: joel.zdepski@opentv.com
> WWW: www.opentv.com
> ------------------------------------------------------------------
> 
>>  <<CSSTVProfile_comments.doc>>
>
>                                                         OpenTV (logo)
> 
> To whom it may concern:
> 
> OpenTV has carefully reviewed the CSS TV Profile 1.0, dated May 15, 2002, that
> is currently in ³Last Call Working Draft² form and that is available on the
> W3C website and this e-mail is sent as an external (public) response to that
> draft.
> 
> Our review centered upon the feasibility of supporting at least the CSS
> selectors and properties that you specified both for rendering directly using
> mid- to high-end set-top boxes as well as for transcoding (assuming static
> cascading rules if there is no return channel) and then displaying on low-end
> set-top boxes.  Additionally, we considered the type of functionality that is
> demanded by designers of content for interactive television who use our
> current, widely fielded products.
> 
> We commend the document drafters for their excellent work.
> 
> There is, however, one small change that we believe will be necessary to
> achieve adequate performance on todayıs set-top boxes.  This change has to do
> with the properties from CSS-3ıs Color Profile that are required and those
> that are optional.   It has been our experience that content designers demand
> the ability to specify transparency on a per-color basis rather than on a
> per-element basis.  CSS-3ıs RGBA would satisfy this demand, yet it is excluded
> from  the CSS TV Profile 1.0, while support for CSS3ıs opacity property is
> required.  It has been our experience that content providers would not
> typically be satisfied with this single transparency attribute; it appears to
> us to be impossible to obtain adequate performance if this property is used in
> conjunction with RGBA on most set-top boxes; and that some lower end set-top
> boxes that are very important in todayıs market cannot support the opacity
> property while they can support at least one semi-transparent color in their
> hardware palette.
> 
> Sincerely,
> 
> Joel Zdepski, Ph.D.
> Vice President
> Office of the CTO
> OpenTV
Received on Friday, 14 June 2002 00:19:44 GMT

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