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

Proposal related to bug 22270 "Adding tracks to MediaStream should only be possible for constructed streams"

From: Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com>
Date: Thu, 24 Oct 2013 11:19:40 +0000
To: "public-media-capture@w3.org" <public-media-capture@w3.org>
Message-ID: <1447FA0C20ED5147A1AA0EF02890A64B1C3C4A7C@ESESSMB209.ericsson.se>
Hi, this relates to bug 22270,
https://www.w3.org/Bugs/Public/show_bug.cgi?id=22270, that proposes to
allow adding/removing tracks from a (by the app) constructed MediaStream 
only. Platform generated MediaStreams (those coming from getUserMedia, 
and on the remote side of a PeerConnection) should not have those methods.

We could spec that by having completely independent IDLs for
"Constructed" and "Platform" MediaStream's, but since there is such a
large overlap between them it seems more efficient to use a base
description that they both extend.

I've sketched on two alternatives. The second one (Alternative B)is 
inspired by Web Worker's (and its AbstractWorker) with an 
AbstractMediaStream which is "implemented" by Platform/Constructed 
MediaStreams. The first one (alternative A) uses inheritance instead of 
"implements".

I'm far from a WEBIdl expert, but to me Alternative A seems better in
that we can specify consumers be able to consume the "BaseMediaStream" 
only, and would not have to worry about updating them if we would ever 
add another type of MediaStream (that inherits from BaseMS). If we go 
with alternative B we would have to spec that every consumer can handle 
two types of MediaStream's for now (PlatfromMediaStream and 
ConstructedMediaStream), and would have to update them if we add another 
type in the future.

Are there any comments or opinions? (And yes, the names are horrible.)

Stefan




Alternative A
=============
interface BaseMediaStream : EventTarget {
             readonly    attribute DOMString    id;
             sequence<MediaStreamTrack> getAudioTracks ();
             sequence<MediaStreamTrack> getVideoTracks ();
             MediaStreamTrack?          getTrackById (DOMString trackId);
             readonly    attribute boolean      active;
                         attribute EventHandler oninactive;
};


interface PlatformMediaStream : BaseMediaStream {
                         attribute EventHandler onaddtrack;
                         attribute EventHandler onremovetrack;
};



[Constructor,
                 Constructor (BaseMediaStream stream),
                 Constructor (MediaStreamTrackSequence tracks)]
interface ConstructedMediaStream : BaseMediaStream  {
             void                       addTrack (MediaStreamTrack track);
             void                       removeTrack (MediaStreamTrack 
track);
};


Alternative B
=============
[NoInterfaceObject]
interface AbstractMediaStream {
            readonly    attribute DOMString    id;
            sequence<MediaStreamTrack> getAudioTracks ();
            sequence<MediaStreamTrack> getVideoTracks ();
            MediaStreamTrack?          getTrackById (DOMString trackId);
            readonly    attribute boolean      active;
                        attribute EventHandler oninactive;
};


interface PlatformMediaStream : EventTarget {
                        attribute EventHandler onaddtrack;
                        attribute EventHandler onremovetrack;
};
PlatformMediaStream implements AbstractMediaStream;


[Constructor,
                Constructor (ConstructedMediaStream stream),
                Constructor (PlatformMediaStream stream),
                Constructor (MediaStreamTrackSequence tracks)]
interface ConstructedMediaStream  : EventTarget {
            void                       addTrack (MediaStreamTrack track);
            void                       removeTrack (MediaStreamTrack track);
};
ConstructedMediaStream implements AbstractMediaStream;

Received on Thursday, 24 October 2013 11:20:08 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 16:26:20 UTC