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Re: [Bug 23220] Add 'zoom' constraint to VideoStreamTrack

From: Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com>
Date: Tue, 1 Oct 2013 09:51:43 +0000
To: Rob Manson <roBman@mob-labs.com>
CC: "public-media-capture@w3.org" <public-media-capture@w3.org>, "public-ar@w3.org" <public-ar@w3.org>
Message-ID: <1447FA0C20ED5147A1AA0EF02890A64B1C3990DC@ESESSMB209.ericsson.se>
On 2013-09-30 02:37, Rob Manson wrote:
> I drew this diagram recently in an attempt to put together a clear
> picture of how all the flows work/could work together.  It seems to
> resonate with quite a few people I've discussed it with.
> NOTE: This was clearly from the perspective of the post-processing
> pipeline scenarios we were exploring.
> Code:
> https://github.com/buildar/getting_started_with_webrtc#image_processing_pipelinehtml
> Slides:
> http://www.slideshare.net/robman/mediastream-processing-pipelines-on-the-augmented-web-platform
> But the question marks in this diagram really relate directly to this
> discussion (at least in the write direction).
> It would be very useful in many scenarios to be able to programatically
> generate a Stream (just like you can with the Web Audio API). Plus all
> the other scenarios this type of overall integration would unlock (zoom,
> etc).
> And then we would be able to use this Stream as the basis of a MediaStream.
> And then we would be able to pass this MediaStream to a PeerConnection
> like normal.
> There's a lot of discussion in many different threads/working groups and
> amongst many of the different browser developers about exactly this type
> of overall Stream based architecture...and the broader implications of this.
> I think this overall integration is a key issue that could gain good
> support and really needs to be looked into.  I'd be happy to put
> together a more detailed overview of this model and gather
> recommendations if there's no strong objections?
> It seems like this would most sensibly fit under the Media Capture
> TF...is this correct home for this?

If you look at the charter [1], the fit is not that good. The WebRTC WG 
charter [2] mentions “API functions for encoding and other processing of 
those media streams” - which could be interpreted to fit.

On the other hand the WebRTC WG has a lot on its plate already and needs 
to focus.

A third option could be to form some new group - community or working - 
for this work.

Perhaps the best thing to do is to use this list to probe the interest 
(e.g. by putting together the detailed overview you mention), and if 
there is interest we can discuss where to take the work.


[2] http://www.w3.org/2011/04/webrtc-charter.html

> PS: I'm about to present this pipeline work as part of a workshop at the
> IEEE ISMAR in Adelaide so I'll share the slides once they're up.
> roBman
> On 30/09/13 09:59, Silvia Pfeiffer wrote:
>> On Mon, Sep 30, 2013 at 8:17 AM, Harald Alvestrand <harald@alvestrand.no> wrote:
>>> On 09/29/2013 06:39 AM, Silvia Pfeiffer wrote:
>>>> FWIW, I'd like to have the capability to zoom into a specific part of
>>>> a screen share and only transport that part of the screen over to the
>>>> peer.
>>>> I'm not fuzzed if it's provided in version 1.0 or later, but I'd
>>>> definitely like to see such functionality supported eventually.
>>> I think you can build that (out of strings and duct tape, kind of) by
>>> screencasting onto a canvas, and then re-screencasting a part of that
>>> canvas. I'm sure there's missing pieces in that pipeline, though - I
>>> don't think we have defined a way to create a MediaStreamTrack from a
>>> canvas yet.
>> Interesting idea.
>> It would be possible to pipe the canvas back into a video element, but
>> I'm not sure if we can as yet take video element content and add it to
>> a MediaStream.
>>> It takes more than a zoom constraint to do it, however; at minimum you
>>> need 2 coordinate pairs (for a rectangular viewport).
>> True. I also think we haven't standardised screensharing yet, even if
>> there is an implementation in Chrome.
>> Silvia.

Received on Tuesday, 1 October 2013 09:52:08 UTC

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