W3C home > Mailing lists > Public > public-media-capture@w3.org > April 2013

Re: addTrack/removeTrack on gUM streams and PeerConnection remote streams

From: Harald Alvestrand <harald@alvestrand.no>
Date: Wed, 17 Apr 2013 08:55:48 +0200
Message-ID: <516E4774.5050308@alvestrand.no>
To: public-media-capture@w3.org
On 04/17/2013 01:09 AM, Robert O'Callahan wrote:
> To be concrete, here's what I think we should do:
> -- Introduce a new subtype of MediaStream, let's call it 
> BundleMediaStream but I don't care what it's called. This stream 
> represents a bundle of tracks from other MediaStreams, where the 
> application controls the track set.
> -- Move the current MediaStream constructors to BundleMediaStream.
> -- Move addTrack/removeTrack to BundleMediaStream.
> -- Specify that for MediaStreams other than BundleMediaStream, the UA 
> always controls the track set.
> This means for any MediaStream, either the UA controls the track set, 
> or the application does, but not both. I think this is a helpful 
> simplification for implementations and at the spec level.
> How does that sound?

To me, it sounds unjustified.

The following code:

getUserMedia(... function(inflexibleStream) {
      flexibleStream = BundledMediaStream(inflexibleStream);
      ... the success callback in existing code ....
}... )

will provide a stream with 100% exactly the behaviour we have today. So 
implementations have to support the same behaviour in the new model as 
in the old model - you're not preventing any complexity that we 
currently have.

I don't see what advantage we get by the existence of the intermediate 
object that justifies the complexity of adding it to the model.

> A reasonable alternative that requires less new syntax would be to 
> make addTrack/removeTrack throw an exception when called on a 
> MediaStream that wasn't constructed via a MediaStream constructor. 
> However, I think introducing a new type is cleaner.
> Rob
> -- 
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Received on Wednesday, 17 April 2013 06:56:38 UTC

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