W3C home > Mailing lists > Public > public-media-capture@w3.org > October 2012

RE: Settings API Proposal v3 feedback summary

From: Travis Leithead <travis.leithead@microsoft.com>
Date: Fri, 5 Oct 2012 00:11:53 +0000
To: Stefan Hakansson LK <stefan.lk.hakansson@ericsson.com>, "public-media-capture@w3.org" <public-media-capture@w3.org>
Message-ID: <9768D477C67135458BF978A45BCF9B3853A4BB32@TK5EX14MBXW605.wingroup.windeploy.ntdev.microsoft.com>
> From: Stefan Hakansson LK [mailto:stefan.lk.hakansson@ericsson.com]
> 
> Travis,
> 
> many thanks for putting this together. I think that overall I like this
> a lot.

After reading through this, what I didn't get around to was the examples. I think I'll need to create some, since code samples are a bit easier to follow than interface definitions :)


> Just to make sure I got the main things right, my understanding is:
> 
> * the getUserMedia does not deliver a LocalMediaStream any more, instead
> it is more of a "gate", which once opened leads to the UA building up
> "DeviceListAccess" lists

Not sure you got it... getUserMedia works almost the same as before, but delivers a
generic MediaStream (instead of a LocalMediaStream). It's the tracks in the
MediaStream that are fundamentally different (extended).


> * these lists are "live", devices can come and go, the user more
> approves the use of video or/and audio and not specific devices

If referring to the device lists, then yes, that is the intention. The user
approves the "class" of device, rather than a specific device, since once one
device of a given class has been delivered, all the other related devices
can be easily discovered.

> * to use a device, the app would have to use the MediaStream constructor
> to build a MediaStream (which can then be consumed by a video element, a
> PeerConnection, ...) from the devices in the DeviceListAccess list

No, in the simple case, the MediaStream returned by getUserMedia can be used
directly with a video element, etc., as we've discussed in the past.


> My conclusion thus far: I think it is fine that the app has to construct
> a MediaStream from device tracks (rather than getting a LocalMediaStream
> that is ready to use). It is a bit more cumbersome, but not that much.
> I'm a bit more hesitant to that new devices just populate the
> "DeviceListAccess" and can be used. I have a couple of issues with this:
> 
> 1. Even if the user is OK with video from a cam facing one way it is not
> certain that she/he would be OK with sharing another view (and I think
> the discussion in WhatWG ages ago said that the user should have to
> manually select the devices that the app could use just like for the
> File API to avoid accidental leak of privacy)

If we as a WG still feel this way, the proposal can be simplified to only reveal
the count of devices available, for example, rather than a device list.


> 2. For devices where the underlying system cannot resolve camera
> direction (front, back) the old model allowed the app to e.g. have a
> button "select a front facing cam" which when clicked issue
> "getUserMedia". This will be more difficult in your proposal if I
> understand correctly (I guess that the app could display the video of
> every cam in a small video element and ask the user to click on the
> right one though - so this may be a minor issue, except for:)

Actually, the easiest way to do this, would be to either 1) use an optional
constraint in getUserMedia (which is still possible with this proposal), or
2) get the device list and call select() passing in that constraint, and the
resulting device object (if any) will be given in the event handler. (select()
is pretty much exactly like getUserMedia's constraint system, it just provides
results in an event, instead of returning and activating a MediaStream.)


> 3. When will the devices in the "DeviceListAccess" be reserved (stopping
> other web or native apps from using them)? When they are added to the
> list or when they are used? There was a clear model for this with
> getUserMedia. (And even if they are not reserved until used, there is
> the risk that the app uses all of them to enable the user to select the
> right one, and then never releases them). And when would htey be released?

Good question. I'll need to think about this.


> -------------------------------------------------------------------
> 
> Apart from those issues, that perhaps we can find a way around, I like
> the proposal a lot. Some minor comments:
> 
> Section 1.1: As already stated, I'm not sure that the user giving OK to
> video is the same as allowing any camera to be used. I guess this is a
> privacy and usability question that needs to be discussed more.
> 
> Section 2.1.1: Should not "frameRate" also be (readonly) attribute for
> VideoStreamTrack?

I thought about this--remote media coming from a peer connection might have
a variable rate, and as such you'd want a more complete API for dealing with
that. To keep things simple, I limited it to a video device track only.

> Regarding the Setting/retrieval application, my understanding is that a
> request would lead to that the constraints for the device in question
> are changed. Correct? Does this also mean that the
> constrainterror/success events could be fired as a result?

Yes, those events should be fired in those cases.

> 
> Stefan
> 
> 
> 
> >
> >
> >> -----Original Message-----
> >> From: Travis Leithead
> >> Sent: Monday, October 1, 2012 4:37 PM
> >> To: public-media-capture@w3.org
> >> Subject: Settings API Proposal v3 feedback summary
> >>
> >> Before preparing the 4th version of the settings API proposal, I
> thought
> >> it would be nice to step back and summarize the feedback received on
> v3.
> >> I've not been as responsive to responding to individual threads, so I'm
> >> using this one as an opportunity to aggregate all the feedback into one
> >> location.
> >>
> >> There was lots of positive responses. Thank you!
> >>
> >> I have a v4 that I'll be releasing shortly, so stay tuned.
> >>
> >> -Travis
> >>
> >> 1  Liked the approach/heading in the right direction [Rich-2] [Stefan-
> 1]
> >> [Adam-1]
> >> 2  Are all the various dictionaries values read/write or read-only?
> >> [Stefan-1]
> >> 3  Should the constraints/settings be inlined in the spec? (No strong
> >> preference) [Stefan-1]
> >> 4  Is this proposal and constraints applied to gUM complimentary?
> [Stefan-
> >> 1]
> >> 5  Establishes a nice "source-of-track" pointer [Randell-1]
> >> 6  Derivative of an earlier proposal (suggested in [Randell-2]?)
> >> 7  Doesn't solve multiple consumers competing for changing settings
> >> [Randell-1] (clarified by [Stefan-2/3])
> >> 8  Forces all tracks that want changes to have a MediaDevice
> >> (PeerConnection, Video element src) [Randell-1] [Stefan-2]
> >> 9  Proposal for unified device/track concept (duck-typing) [Rich-2]
> >> (comments [Travis-2])
> >> 10 Liked the prior proposal with immutable track lists over the
> devices-
> >> based LMS [Adam-1] [Adam-3]
> >> 11 takePicture(); how is it related to regular media stream recording?
> >> [Adam-1]
> >> 12 Can the *Info dictionaries be exposed to gUM for early device
> >> filtering? [Adam-1]
> >> 13 Should align with PeerConnection track ideas/ track-subtypes [Adam-
> 2]
> >> 14 Additional settings requested [Giridhar-1]
> >> 15 Proposal on how to scope what settings we expose [Rich-1]
> >> 16 Idea on how to consolidate/group the settings [Josh-1/2] [Jim-1]
> >> [Travis-1]
> >> 17 How do we define interoperable settings (how do we test them)?
> >> [Frederick-1] [Jim-2]
> >> 18 How should UA's optionally surface device-specific settings? [Jim-2]
> >> 19 Re-consider one track-per-type in gUM? [Adam-3]
> >> 20 Don't hide capabilities behind get/changeSettings APIs [Rich-2]
> >> (comments [Travis-2])
> >>
> >> [Stefan-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0000.html
> >> [Stefan-2] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0002.html
> >> [Stefan-3] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0003.html
> >> [Randell-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0001.html
> >> [Randell-2] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Aug/0044.html
> >> [Adam-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0004.html
> >> [Adam-2] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0006.html
> >> [Adam-3] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0005.html
> >> [Giridhar-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0008.html
> >> [Rich-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0013.html
> >> [Rich-2] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Aug/0144.html
> >> [Josh-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0017.html
> >> [Josh-2] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0020.html
> >> [Jim-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0018.html
> >> [Jim-2] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0022.html
> >> [Travis-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0019.html
> >> [Travis-2] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Aug/0146.html
> >> [Frederick-1] http://lists.w3.org/Archives/Public/public-media-
> >> capture/2012Sep/0021.html
> >>
> >> Additionally, I'm thinking about the following:
> >> * How often will settings be changed in bulk vs. one-at-a-time (with
> user
> >> feedback)?
> >> * How will developers know to request another device via gUM? (how will
> >> they know that more devices are available)?
> >
> >
> 
> 
Received on Friday, 5 October 2012 00:12:27 GMT

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