[whatwg] Apple Proposal for Timed Media Elements

ddailey ddailey at zoominternet.net
Thu Apr 5 04:53:00 PDT 2007

I understand that some here have reasons not to be happy with SMIL, but its 
implementation within SVG really is quite nice and understandable. So far as 
I can see, the discontent with it stems primarily from the fact SMIL seems 
to have alternative specifications. Since the SVG implementation is the one 
which seems to have met with fairly wide adoption, why not just converge 
with the attribute set used there to control an animation?

Instead of media-loop-count it uses repeatCount. "dur" controls the 
duration, "begin" controls when it starts, "end" controls when it stops.
Just for fun, one can add things like "begin=object.click" or 
"begin=M.begin+1" to allow control to be passed declaratively, and to 
synchronize multiple events, hence avoiding the need for copious script. If 
one had multiple media elements on a page, controlling the synchronization 
of those elements is quite within the province of SMIL(SVG).

All the timing mechanisms that are discussed here, are I believe, covered in 
SMIL, each with a different set of attribute names.
It even has spline interpolations on the timing elements. In Opera or IE 
with the Adobe plugin http://srufaculty.sru.edu/david.dailey/svg/smil.htm
shows some of the range of extant behavior.

Sorry if this horse is already dead, and copious apologies about my 
cluelessness when it comes to how to read and write specifications, but 
there are already authors and developers who are fluent in SVG/SMIL, so why 
reinvent wheels?

----- Original Message ----- 
From: "Maciej Stachowiak" <mjs at apple.com>
To: "Vladimir Vukicevic" <vladimir at pobox.com>
Cc: <whatwg at whatwg.org>
Sent: Wednesday, April 04, 2007 10:58 PM
Subject: Re: [whatwg] Apple Proposal for Timed Media Elements

> On Apr 4, 2007, at 7:31 PM, Vladimir Vukicevic wrote:
>> Maciej Stachowiak wrote:
>>> CSS Timed Media Module proposal - http://webkit.org/specs/ 
>>> Timed_Media_CSS.html
>> Some feedback on my initial reading..  the CSS properties specified  seem 
>> like a good set that will cover most common functionality.   Some 
>> comments about the spec, though:
> Thanks for reading over this part.
>> 1. 'media-loop-count' is an awkward name, especially with "The  default 
>> value of 1 means the item will play through once but will  not loop."  We 
>> went through this with APNG, and ended up renaming  that member.  I would 
>> suggest 'media-play-count' instead -- that  way there is no ambiguity 
>> with what the number means.
> We considered 'media-repeat-count' instead of 'media-loop-count', but 
> that turned out to be more confusing. We really wanted all the 
> looping-related properties to have consistent naming, and I don't  think 
> 'play' would work in the other places mentioned.
>> 2. The descriptions for 'media-loop-start-time' and 'media-loop-end- 
>> time' don't match; start-time says "sets the time at which the  media 
>> item begins playing after looping", and end-time says "sets  the time at 
>> which the media item loops for the second and  subsequent repetitions".
>> I would suggest that start-time says "sets the time index at which  the 
>> media item starts playing for the second and subsequent  repetitions", 
>> and that end-time says "sets the time index at which  the media item ends 
>> playing for the second and subsequent  repetitions."  The language for 
>> end-time is still a little awkward,  since "ends playing" could imply 
>> that it simply stops playing (and  does not loop), but it's clearer than 
>> before.
> I think the language might have ended up actually defining it wrong.  The 
> intent of 'media-loop-end-time' is that this is the point where  you end 
> where repeating, but on the last iteration you go all the way  to 
> 'media-end-time'. So if 'media-loop-count' has a value of 3, the  three 
> repetitions would go as follows:
> media-start-time                                    ===>       media- 
> loop-end-time
>                           media-loop-start-time   ===>       media- 
> loop-end-time
>                           media-loop-start- time 
> ===>       media-end-time
> I'll update the spec.
>> 3. 'media-timing' I would get rid of completely; while a shorthand  would 
>> be useful, I don't think that media-timing as specified  really works. 
>> Shorthands for properties such as 'background' are  understandable on 
>> their own; 'media-timing: playing 0s -0.5s 2 2s  -4s 1' is very opaque. 
>> If it's still desirable, I would remove  the setting of start/end times 
>> and change the volume shorthand to  only accept the symbolic names; e.g. 
>> 'media-timing: playing high  4;'... but I think that removing the 
>> shorthand entirely would be  preferable.
> I'll reply in more detail about media-timing in a later message.
> Regards,
> Maciej

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