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Re: Resolution changes

From: Harald Alvestrand <harald@alvestrand.no>
Date: Mon, 14 Sep 2015 18:17:49 -0700
To: Martin Thomson <martin.thomson@gmail.com>, "public-webrtc@w3.org" <public-webrtc@w3.org>
Message-ID: <55F771BD.2000605@alvestrand.no>
On 09/14/2015 02:38 PM, Martin Thomson wrote:
> What happens when MediaStreamTrack changes resolution to something
> outside of the negotiated envelope of the session?  There is no
> language in the spec.  Presumably if the resolution can be reduced,
> reduce it.  Increasing resolution might be the only option we have in
> the case that the session has a resolution floor.
Section 5:

Let's look at a slightly different situation starting from the same
point. In this case, instead of the first track attempting to apply a
conflicting constraint, the user physically locks the camera into a mode
where the fill light is on. At this point the source can no longer
satisfy the second track's mandatory constraint that the fill light be
off. The second track is transitioned into the muted state and receives
an |overconstrained|
<http://w3c.github.io/mediacapture-main/getusermedia.html#event-mediastreamtrack-overconstrained> event.

More info in section 11.1.1.

> What happens when aspect ratio changes?  Letterbox & pillars?

That's a better question. I remember discussing this subject in Boston, with one option being that one could have a constraint (or constraint-like setting) that chose one of the defined values for the object-fit CSS attribute: fill, contain, cover, none or scale-down.

https://css-tricks.com/almanac/properties/o/object-fit/

But nobody's suggested text in the intervening 2 years, so I guess it's not that important.
(My suggestion would be to default to "contain", which causes letterbox and pillars.)



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Received on Tuesday, 15 September 2015 01:18:25 UTC

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