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Re:

From: Jack Jansen <Jack.Jansen@cwi.nl>
Date: Fri, 28 May 2010 00:25:06 +0200
Cc: www-smil@w3.org
Message-Id: <96759C4A-A7D5-4F1C-9F6E-FD5606A4A296@cwi.nl>
To: "Sanja C." <sanjac@rocketmail.com>
  
On 27 mei 2010, at 20:14, Sanja C. wrote:

> Hi,
> 
> we're considering a SMIL-based solution for stand-alone multimedia-presentations (i.e. digital signage) in our organisation, but are not sure how well it fits our needs with regards to integrating calendar time range specific content into the "normal flow" of a seq/par-driven presentation.
> 
> We'd be very grateful if some more SMIL-experienced people would comment on the following two scenarios:
> 
> __Scenario 1:__
> 
> Consider a presentation of the following form that continually loops through a number of multimedia pages:
> 
> <seq repeatCount="indefinite">
>     <ref title="Page 1"/>
>     <par>
>         <ref title="Page 2"/>
>         <ref title="specialOverlay"/>
>     </par>
>     <ref title="Page 3"/>
>     <ref title="Page 4"/>
>     ...
> </seq>
> 
> Now, is it possible to add SMIL markup to this presentation that will enforce the following constraints, respectively:
> 
>    example A)  Only show the "specialOverlay" on [Sunday, 30. Mai 2010, 9am - 18am] (or any other specific calendar time range)
>    example B)  Only show the "specialOverlay" on [Sunday, between 9am - 18am] (meaning: *every* sunday)
>    example C)  Only show the "specialOverlay" on holidays (where the data about which days are holidays is supplied through an external file)
> 
> ..without otherwise affecting the behaviour of the seq element?

Sanja,
the short answer is that this is not directly possible with SMIL 3.0. Wallclock timing (see http://www.w3.org/TR/2008/REC-SMIL3-20081201/smil-timing.html#Timing-WallclockSyncValueSyntax) allows you to specify a single time, a single date or a single date+time. Unfortunately things like "every sunday" are not expressible.

The slightly longer answer is that it is possible by using a tiny external agent (or script). SMIL State (see http://www.w3.org/TR/2008/REC-SMIL3-20081201/smil-state.html) was specifically designed with this use in mind (among other things): the whole SMIL presentation is declarative, with some parts based on SMIL State variable(s). This variable is then changed by the external agent.

Your SMIL document would look something like this:
...
 <head>
  <state xmlns="">
   <data>
    <showSpecialOverlay>0</showSpecialOverlay>
   </data>
  </state>
 </head>
 ...
  <par>
   <ref title="Page 2"/>
   <ref expr="showSpecialOverlay"  title="specialOverlay"/>
  </par>
...

Now, specialOverlay will only be shown if, at the time it is eligible to play, the showSpecialOverlay variable is true. So, you would supply a script that sets/clears this variable depending on the date/time. Or you could make it depend on anything else you want (think: attach a camera with face recognition to your billboard and count the number of people watching it, to name something completely different:-).

You could also do things even more declarative, by having the script only filling in relevant parts of date and time, for example every hour, in a data structure like
  <state xmlns="">
    <data>
      <year/>
      <month/>
      <day/>
      <weekday/>
      <hour/>
    </data>
  </state>
your example B could now be coded as
   <ref expr="weekday=7 and hour &gt; 9 and hour &lt; 18" title="specialOverlay"/>

Many more wild things are possible with SMIL State, let me know if you're interested and I can point you to a paper we wrote on the subject.

> 
> __Scenario 2:__
> 
> Consider again a presentation continually looping through a fixed set of pages:
> 
> <seq repeatCount="indefinite">
>     <ref title="Page 1"/>
>     <ref title="Page 2"/>
>     <ref title="Page 3"/>
>     ...
> </seq>
> 
> Imagine this presentation will run around-the-clock, all year long.
> Now, is it possible to specify an alternative <seq></seq> section for a specific calendar time range so that at the beginning of this time range, the normal seq presentation is halted (no matter what it's currently showing), and the alternative <seq></seq> is shown, until the end of the time range, when the normal presentation is resumed? (Note: it would also be acceptable if the original presentation would then re-start at its beginning, instead of resuming exactly where it had left off.)

This is easier, assuming single datetime begin and end points:

  <excl>
    <seq begin="0;wallclock(20100605T1800)" repeatCount="indefinite">... normal seq... </seq>
    <seq begin="wallclock(20100605T0900)" repeatCount="indefinite">...special seq...</seq>
  </excl>

This will play the normal sequence, repeatedly, except from 9AM to 6 PM on June 5th, 2010, when it plays the special sequence.
 
> Is this kind of stuff possible with SMIL 3.0 markup?
> 
> Note that we *don't* want to use scripting, just XML-based markup (if this is not possible with plain SMIL, we'd rather develop a custom non-SMIL-based solution altogether, or our own SMIL-extension, or a "wrapper" that calls/terminates different SMIL presentation at different times).

If you decide on extending SMIL I would be more than happy to provide you with some ideas, the use case for richer specification of wallclock time constraints should be common for digital signage, and I think that it is an important area for SMIL. If you have the time (and inclination) to do this extension in a way that would ease possible integration into a next version of SMIL (if ever there is going to be one) that would be a boon!
--
Jack Jansen, <Jack.Jansen@cwi.nl>, http://www.cwi.nl/~jack
If I can't dance I don't want to be part of your revolution -- Emma Goldman
Received on Thursday, 27 May 2010 22:25:50 GMT

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