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Re: [presentation-api] Remove getAvailability() url argument unless implemented

From: Mark Foltz via GitHub <sysbot+gh@w3.org>
Date: Tue, 07 Jul 2015 21:26:24 +0000
To: public-secondscreen@w3.org
Message-ID: <issue_comment.created-119347167-1436304382-sysbot+gh@w3.org>
The specific circumstance is when the only display available is 
incapable of rendering generic Web content (i.e. usable in 2-UA mode) 
or a generic video stream (i.e. usable in 1-UA mode).  However, it can
 function as a proxy by mapping a URL resource to a fixed set of 
presentation modes.   This is the case that mwatson2@ alluded to in 
https://github.com/w3c/presentation-api/issues/138#issuecomment-119219557
 for Netflix.  As it happens, this is a common case for users who have
 Internet-connected TVs, set top boxes, game consoles, etc. most of 
which use DIAL [1] to facilitate remote launch of these applications.

Rather than offering the user these displays as generic presentation 
targets but having them fail to render in many circumstances, this 
allows the UA to offer presentation when it has some confidence that 
the request will succeed (by first querying the device for 
compatibility with the DIAL application).  If you are curious about 
the specific mechanism see section 6.1 of the specification [1].

Over time I hope that this is the less common case.  Cast devices will
 all support 1-UA mode initially and there is an active effort to add 
Presentation API support to HBB TV 2.0 in 2-UA mode 
https://github.com/w3c/presentation-api/issues/67#issuecomment-118061074.

Down the road we've discussed expanding the Presentation API to allow 
the controlling page to require more specific capabilities from the 
display like specific codecs, audio/video outputs, or perhaps 
installed applications.  But we don't have a specific proposal yet 
that encompasses all these cases.

[1] http://www.dial-multiscreen.org/dial-protocol-specification

-- 
GitHub Notif of comment by mfoltzgoogle
See 
https://github.com/w3c/presentation-api/issues/138#issuecomment-119347167
Received on Tuesday, 7 July 2015 21:26:25 UTC

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