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Re: [SMIL30 LC comment] 7.13.2 MediaPanZoom Module ( LC-1794)

From: <tmichel@w3.org>
Date: Fri, 26 Oct 2007 12:51:03 +0000
To: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Cc: www-smil@w3.org
Message-Id: <E1IlOeV-0000BZ-K7@wiggum.w3.org>

 Dear Dr. Olaf Hoffmann ,

The SYMM Working Group has reviewed the comments you sent [1] on the Last
Call Working Draft [2] of the Synchronized Multimedia Integration Language
(SMIL 3.0) published on 13 Jul 2007. Thank you for having taken the time to
review the document and to send us comments!

The Working Group's response to your comment is included below.

Please review it carefully and let us know by email at www-smil@w3.org if
you agree with it or not before 02 nov 2007. In case of disagreement, you
are requested to provide a specific solution for or a path to a consensus
with the Working Group. If such a consensus cannot be achieved, you will
be given the opportunity to raise a formal objection which will then be
reviewed by the Director during the transition of this document to the
next stage in the W3C Recommendation Track.


For the SYMM Working Group,
Thierry Michel
W3C Staff Contact

 1. http://www.w3.org/mid/200708031220.40108.Dr.O.Hoffmann@gmx.de
 2. http://www.w3.org/TR/2007/WD-SMIL3-20070713/


Your comment on 7.13.2 Elements and Attributes for the MediaPanZoom
> Hello SMIL working group,
> I think, I found a few problems with this module.
> a) General definition
> 'The SMIL MediaPanZoom module integrates the functionality of the SVG
> viewBox 
>  attribute and adapts it for use within the SMIL media framework.'
> I think, it is in the current definition only in some points related to
> the 
> SVG viewBox:
> 'The value of the viewBox attribute is an ordered list of four numbers,
> separated by whitespace and/or a comma:'
> - This indeed fits to the SVG viewBox.
> But:
> ' width
> A non-negative length value (using CSS2 pixel or non-negative
> percentage 
> values) 
> that defines the horizontal dimension of the viewBox. If pixel notation
> is 
> used, 
> the 'px' suffix may be omitted. A negative value is an error. The
> default 
> value of 
> width is auto.'
> - This does not fit to SVG and not to the previous description, because
> the
> value is not a number anymore if it can contain the unit 'px' or can be
> noted
> in percentage. If the default width is 'auto', this is neither a
> number, nor a
> percentage value, nor a length value (a number and a unit).
> This section is inconsistent in itself and 'width' and 'height' are not
> consistent with the SVG definition of viewBox.
> Comparison with SVG:
> -> viewBox on an image element for example does not
> work in SVG as described here for SMIL3.
> In SVG 1.1 or SVG tiny 1.2 CR it is noted:
> 'i.e. the 'image' element has an implicit 'viewBox' of 
> "0 0 raster-image-width raster-image-height"'
> Similar thing we get in SVG tiny 1.2 CR
> for the elements video and animation.
> To conclude, the viewBox described in this draft does not
> have much more in common with the SVG viewBox element as the name.
> It works more or less in a similar way for the elements svg and
> symbol.
> Maybe it is a good idea to change the name of the SMIL attribute to
> avoid confusion, for example what about zoomBox?
> b) The example contains errors:
> '<smil ...>
>   <head>
>   ...
>     <layout>
>       <root-layout height="200" width="300" backgroundColor="red" />
>       <region id="B" top="0" left="0" height="50" width="75"  
> backgroundColor="blue" />
>     </layout>
>   </head>
>   <body>
>     <seq> 
>       <ref id="R0" src="table_233x150.jpg" viewBox="0,0,50,75"
> dur="20s" 
> region="T" fit=""meet" >
>          <animate attributeName="viewBox" 
>                      values="(25,20,50,75);
> (45,55,50,75);(140,40,50,75);
> (35,0,100,150); (0,0,100,150);" 
>                      dur="20s" />
>       </ref>
>       ...
>     </seq>
>   </body>
> </smil>'
> - the animate element, the values attribute:
> -> The last ';' is wrong
> -> the '(' and ')' are not part of the viewBox attribute or the values
> attribute,
>      therefore this is wrong too.  
> -> values="25,20,50,75; 45,55,50,75;140,40,50,75;35,0,100,150;
> 0,0,100,150"
> c) Animation problem (?)
> -> What about calcMode paced for viewBox?
> Due to some wrong formulas in the SVG tiny 1.2 CR
> I already did some calculations about this for several
> attributes with lists of numbers or even with a mixture
> of values of different units. viewBox is either a list of
> two vectors or a list of one vector and two scalars.
> There can be a paced change of the value of a viewBox.
> The procedure can be to expand the value consisting of
> 4 numbers to a list of 4 points or vectors to the corners
> of the viewBox. For each point or vectors a paced change
> can be gained, using the euclidian distance. If this is
> fulfilled, this results in a paced change of each point
> of the viewBox. But because each corner needs to be
> animated separately, this is no interpolation between the
> given values anymore, therefore the condition of calcMode
> paced is not fulfilled, to interpolate between the values.
> Therefore we can be pretty sure, that there is no 
> behaviour completely consistent with the definition of
> calcMode paced. 
> What is the expected correct behaviour? Fallback to 
> calcMode linear?

Working Group Resolution (LC-1794):
The proposed resolutions to individual comments are:

>> A) General definition:

We have changed the name from viewBox to panZoom to highlight the
differences with SVG.

>> B) The examples contain two error
These typo has been fixed.

>> C) Animation problem (?)

Language has been added to highlight the possible problems with a paced

Received on Friday, 26 October 2007 12:51:13 UTC

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