W3C home > Mailing lists > Public > public-web-and-tv@w3.org > February 2013

Re: Liaison Statement to W3C (SC 29 N 13268)

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 21 Feb 2013 14:58:10 +1100
Message-ID: <CAHp8n2mbM31MK4qR73=oaZdXiMpct1c1D00qkB9_XhMG=+cUnQ@mail.gmail.com>
To: Bob Lund <B.Lund@cablelabs.com>
Cc: "Mark Vickers @ Comcast" <mark_vickers@cable.comcast.com>, Jean-Claude Dufourd <jean-claude.dufourd@telecom-paristech.fr>, "<public-web-and-tv@w3.org>" <public-web-and-tv@w3.org>
On Thu, Feb 21, 2013 at 8:37 AM, Bob Lund <B.Lund@cablelabs.com> wrote:

>   1.     The ability to accurately time the playback of different media
> elements (for instance using wall clock time) in the document in a
> declarative manner, i.e. without reverting to scripting in a way similar to
> SMIL. MMT does not require a scripting engine.
>
>  I'm not sure why scripting is optional in MMT. Can someone familiar with
> SMIL describe what declarative form they're looking for here?
>
>

SMIL allows wallcock time synchronization through using wallclock times in
@begin and @end attributes [1] within <par> and <seq> markup. It requires
that the document "start" time has to be associated with a wallclock time
and thus allows the mapping.

The closest effort to this at the W3C FAIK is the Web Animations work [2]
which is planning to introduce a document timeline [3]. It's still in its
early stages, so no browser implementation. Also, I don't know if it will
satisfy the "declarative markup" requirement, because it only introduces a
JS API for now. But it's probably well worth pointing out this effort to
MPEG.

[1]
http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-timing.html#Timing-WallclockSyncValueSyntax
[2] https://dvcs.w3.org/hg/FXTF/raw-file/default/web-anim/index.html
[3]
https://dvcs.w3.org/hg/FXTF/raw-file/default/web-anim/index.html#the-document-timeline

--

Overall, I do wonder about what MMT has to do with these application-level
requirements. IIUC MMT is about delivering packed media, so it's an enabler
of applications. It should not need to look at HTML & the JS APIs for
defining its specifications.

HTH.

Cheers,
Silvia.
Received on Thursday, 21 February 2013 03:58:59 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 17:57:15 UTC