Re: ISSUE-346: Need ttp:mediaDuration parameter [TTML2]

On Thu, Sep 25, 2014 at 4:11 AM, Nigel Megitt <nigel.megitt@bbc.co.uk>
wrote:

> No processing requirements that use ttp:mediaDuration are stated either in
> the ttp:mediaDuration section at [1]  or anywhere else in the document,
> right now.


Be patient, it will be.


> Taken in isolation this would suggest that it is metadata and
> should not be in the parameter namespace, however I think it is merely a
> reflection of work in progress.
>
> [1]
> https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#paramete
> r-attribute-mediaDuration
>
> My expectation is that, regardless of how they are calculated, the
> effective media begin time and media end time will be used to define the
> temporal period within which any ISDs should be created for display
> alongside the related media, and that mediaDuration would therefore be
> referenced in the Intermediate Synchronic Document Construction process at
> [2]. There's an editorial note on that section - possibly when that note
> has been resolved into spec text this will become clearer.
>
> [2]
> https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#semantic
> s-region-layout-step-1
>
> I've proposed in the "Issue-270 and Issue-335" thread that starts at [3]
> that this period might better be defined explicitly in terms of mediaBegin
> and mediaEnd parameters expressed in the time base of the document. If
> mediaDuration is needed and the time base and marker modes permit time
> calculations (e.g. it is not SMPTE - discontinuous) then it can be
> calculated as (mediaEnd - mediaBegin).
>
> [3] http://lists.w3.org/Archives/Public/public-tt/2014Sep/0065.html
>
>
> I'm interested in the requirement/use case though: when you say "allows
> time values within a document to be 'offset' relative to the start of
> associated media", what calculations are you envisaging that a processor
> should perform, exactly, and in what circumstances might they be useful?
>
>
> Kind regards,
>
> Nigel
>
>
> On 25/09/2014 10:38, "John Birch" <John.Birch@screensystems.tv> wrote:
>
> >I am uncertain about the 'requirement' for a duration parameter?
> >What is the current situation... does TTML1 work as if the media duration
> >is 'indefinite' ?
> >In which case what additional benefit does having a defined duration
> >bring?
> >
> >Of far more importance (IMHO) is a media start value - that allows time
> >values within a document to be 'offset' relative to the start of
> >associated media.
> >
> >Best regards,
> >John
> >
> >John Birch | Strategic Partnerships Manager | Screen
> >Main Line : +44 1473 831700 | Ext : 2208 | Direct Dial : +44 1473 834532
> >Mobile : +44 7919 558380 | Fax : +44 1473 830078
> >John.Birch@screensystems.tv | www.screensystems.tv |
> >https://twitter.com/screensystems
> >
> >Visit us at
> >SMPTE Annual Technical Conference, Loews Hollywood Hotel, Stand 107,
> >October 21-23
> >Languages & the Media, Hotel Radission Blu, Berlin, November 5-7
> >
> >P Before printing, think about the environment-----Original Message-----
> >From: Timed Text Working Group Issue Tracker
> >[mailto:sysbot+tracker@w3.org]
> >Sent: 21 September 2014 13:35
> >To: public-tt@w3.org
> >Subject: ISSUE-346: Need ttp:mediaDuration parameter [TTML2]
> >
> >ISSUE-346: Need ttp:mediaDuration parameter [TTML2]
> >
> >http://www.w3.org/AudioVideo/TT/tracker/issues/346
> >
> >Raised by: Glenn Adams
> >On product: TTML2
> >
> >In order to perform ISD processing, it is necessary to know the duration
> >of root external extent. When associate with a related media object, this
> >is the simple duration of the related media object. If this is known at
> >authoring time, then it is an important parameter that should be
> >specified. I propose defining a ttp:mediaDuration parameter attribute
> >that takes either an offset-time form of a time expression or the keyword
> >"indefinite", where the latter is used (or implied) when no related media
> >object exists or its simple duration is unknown or indefinite. If this
> >parameter is not specified, then it would be treated as if indefinite
> >were specified.
> >
> >
> >
> >
> >This message may contain confidential and/or privileged information. If
> >you are not the intended recipient you must not use, copy, disclose or
> >take any action based on this message or any information herein. If you
> >have received this message in error, please advise the sender immediately
> >by reply e-mail and delete this message. Thank you for your cooperation.
> >Screen Subtitling Systems Ltd. Registered in England No. 2596832.
> >Registered Office: The Old Rectory, Claydon Church Lane, Claydon,
> >Ipswich, Suffolk, IP6 0EQ
>
>