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RE: Cloning and sharing of MediaStreamTracks - worth it?

From: Jim Barnett <Jim.Barnett@genesyslab.com>
Date: Fri, 10 May 2013 17:41:17 +0000
To: Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com>
CC: Martin Thomson <martin.thomson@gmail.com>, "public-media-capture@w3.org" <public-media-capture@w3.org>, Harald Tveit Alvestrand <harald@alvestrand.no>, Robert O'Callahan <robert@ocallahan.org>
Message-ID: <57A15FAF9E58F841B2B1651FFE16D28103DFD1@GENSJZMBX02.msg.int.genesyslab.com>
Stefan,
  I agree completely.  I think that there are a few other areas where we will want to do this as well (asking someone to write something up, that is.  We can give Dan a break every now and then...)

1.  Permissions: How long do permissions granted by gUM persist?  If the user wants to grant permanent permissions to a site, is that done through our API or independently through the UA (in either case, the spec needs to say something about it.)
2.  Origin of the media stream:   For the purposes of enforcing cross-origin constraints, what is the origin of a media stream created by gUM?  Ekr gave a clear explanation of this once, but I haven't seen it written down. 
3.  Branching off into WebRTC, what is the origin of a remote stream received over a PeerConnection?  (It may seem obvious that it's the remote site, but we need to make sure that all use cases work correctly if that's the case.)

- Jim 

-----Original Message-----
From: Stefan Håkansson LK [mailto:stefan.lk.hakansson@ericsson.com] 
Sent: Friday, May 10, 2013 1:30 PM
To: Jim Barnett
Cc: Martin Thomson; public-media-capture@w3.org; Harald Tveit Alvestrand; Robert O'Callahan
Subject: Re: Cloning and sharing of MediaStreamTracks - worth it?

Jim,

I think we need to clarify all of this. But perhaps the best way is that Dan - who has been spending a lot of time on this lately - writes up a proposal (taking into account what was said during the telco the other day), and that we take it from there.

Br,
Stefan

On 5/10/13 2:01 PM, Jim Barnett wrote:
> Stefan, From pervious emails, I thought that you were saying that 
> constraints/settings are always applied to the source _object_, i.e.
> that settings are implemented by changing the state of the underlying 
> device.  Martin is saying that they are never applied to the source 
> object (but instead realized in software in the Track.)  The 
> difference is that in your model (as I understood it) a setting 
> applied to one Track will affect the observed output of all other 
> Tracks that share the same source.  In Martin's model, a setting 
> applied to one Track will not affect the output of other Tracks.
>
> And Harald's  model seems to be: maybe it does, maybe it doesn't, who 
> knows? Life is short, it's up to the UA.
>
> I think we need to be clear on which of these models we are using, or 
> the discussion will keep going in circles.  As an example, in 
> Tuesday's call when the 'zoom' setting came up, it was clear that many 
> people wanted it to apply to the camera's native zoom ability, and not 
> to be some post-processing sleight of hand.  In Martin's model that 
> would not be allowed.  If it is allowed, I think that  it would have 
> to affect the output of all Tracks that share the source.
> Which is it?
>
> - Jim
>
> -----Original Message----- From: Stefan Håkansson LK 
> [mailto:stefan.lk.hakansson@ericsson.com] Sent: Friday, May 10, 2013
> 2:17 AM To: Jim Barnett Cc: Martin Thomson; 
> public-media-capture@w3.org; Harald Tveit Alvestrand; Robert 
> O'Callahan Subject: Re: Cloning and sharing of MediaStreamTracks - 
> worth it?
>
> On 5/10/13 12:09 AM, Jim Barnett wrote:
>> Well, we'd better agree on this  soon or we'll be chasing our tails 
>> forever.  People have radically different understandings of what a 
>> Track actually does. I think that's one reason that the discussions 
>> of cloning and constraints/settings never seems to progress.
>
> Jim, I agree fully. But I don't think Martin and I really differ. I 
> think we're both saying that
>
> * enabled and the set of constraints are track properties * mute and 
> the media are source properties. The app can get info about the media 
> currently generated by probing the state of the source serving the
> track:
> http://dev.w3.org/2011/webrtc/editor/getusermedia.html#source-states
>
>
> Stefan
>>
>> -Jim
>>
>> *From:*Martin Thomson [mailto:martin.thomson@gmail.com] *Sent:* 
>> Thursday, May 09, 2013 4:09 PM *To:* Jim Barnett *Cc:* 
>> public-media-capture@w3.org; Harald Tveit Alvestrand; Stefan 
>> Håkansson LK; Robert O'Callahan *Subject:* RE: Cloning and sharing of 
>> MediaStreamTracks - worth it?
>>
>> "Jim Barnett" <Jim.Barnett@genesyslab.com 
>> <mailto:Jim.Barnett@genesyslab.com>> wrote:
>>>
>>> But see Stefan's email; _everything_ is a source attribute except
>> for 'enabled'.  I don't think that Track is doing much work.
>>
>> That isn't the model that I described. A large part of the state of 
>> the source is actually transparent. The set of constraints, enabled, 
>> and, consequently, the precise form of the track output are track 
>> properties.
>>
>> As far as I can tell, the only concrete properties the source has are 
>> invariant: mute, the media itself. The rest are derived from the set 
>> of constraints provided by the enabled tracks that the source serves. 
>> Those are the properties I'm interested in cloning.
>>
>
>
>
Received on Friday, 10 May 2013 17:41:52 UTC

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