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

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

From: Robert O'Callahan <robert@ocallahan.org>
Date: Wed, 17 Apr 2013 19:30:45 +1200
Message-ID: <CAOp6jLYeqMiyyMkTp1rYn0-K=7_n69s5fTDQ20HdddKffczN7Q@mail.gmail.com>
To: Harald Alvestrand <harald@alvestrand.no>
Cc: "public-media-capture@w3.org" <public-media-capture@w3.org>
On Wed, Apr 17, 2013 at 6:55 PM, Harald Alvestrand <harald@alvestrand.no>wrote:

> 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.
>


The MediaStream constructor that takes a MediaStream parameter is
underspecified; the spec just says "the given stream is cloned" and does
not say whether the two streams share the underlying track set or not. I
had assumed the track sets would not be shared --- the new stream would
have a copy of the original stream's current track set, and would not be
updated as the original stream's track set changes --- but you have assumed
they will share a single underlying track set.

Note that if the track set is shared then the spec text "separate
MediaStream instances can be manipulated and consumed individually" is
misleading since addTrack/removeTrack on one stream would affect the other
one.

Rob
-- 
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Received on Wednesday, 17 April 2013 07:32:00 UTC

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