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Re: [presentation-api] 1-UA and 2-UA details

From: Anton Vayvod via GitHub <sysbot+gh@w3.org>
Date: Fri, 21 Aug 2015 13:32:13 +0000
To: public-secondscreen@w3.org
Message-ID: <issue_comment.created-133425841-1440163933-sysbot+gh@w3.org>
1UA means there's only one user agent instance that renders both the 
controlling and presentation pages. This UA instance in running on the
 controlling device and the presentation page is rendered offscreen on
 that device and the pixels are streamed somehow to the second screen.
 There're still two separate pages involved so it's not like mirroring
 (e.g. tab mirroring in Chrome) where there's only one page and it's 
just rendered on two screens. Streaming the offscreen presentation 
page to the second screen sometimes is referred to as mirroring since 
the technologies used for implemeting (e.g. Miracast or Cast 
Streaming) are the same. So mirroring the controlling page is out of 
scope for the API and mirroring the presentation page is just an 
implementation details like the 1UA or 2UA mode.

2UA means there're two instances of the user agent (same as in Chrome 
and Chrome or different, Chrome and Firefox, for instance) involved in
 presenting the page - one renders the controlling page and another 
one renders the presentation page.

Both modes have different advantages and disadvantages, but these are 
just an implementation detail and that's why it's not in the spec. I 
agree that we might introduce the terms to the spec since these became
 so commonly used by the WG.

A Cast device can support both modes: it can render a web page and it 
also supports Cast streaming protocol which allows UA to stream an 
offscreen rendered page to it.

You're more than welcome to try doing a pull request yourself 
following the instructions: 
https://www.w3.org/wiki/Second_Screen/Work_Mode

-- 
GitHub Notif of comment by avayvod
See 
https://github.com/w3c/presentation-api/issues/164#issuecomment-133425841
Received on Friday, 21 August 2015 13:32:15 UTC

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