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