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Re: New API surface - inbound outbound streams/tracks

From: ᛏᚮᛘᛘᚤ <tommyw@google.com>
Date: Mon, 12 Nov 2012 14:08:03 +0100
Message-ID: <CALLKCfM2XBrKRNGhkveoe2S-RukwMAitA8NYCbRz0-+0OwhyHg@mail.gmail.com>
To: Adam Bergkvist <adam.bergkvist@ericsson.com>
Cc: "public-webrtc@w3.org" <public-webrtc@w3.org>, Travis Leithead <travis.leithead@microsoft.com>
You are proposing to introduce an extremely complicated inheritance
structure instead of adding 3 or 4 methods on RTCPeerConnection. How is
that better? And even more important how is this to be explained to our
users?

pc.addStream(stream);
var outboundStream =
pc.localStreams.getStreamById(**stream.id<http://stream.id/>
);
var outboundAudio = outboundStream.audioTracks[0]; // pending syntax
if (outboundAudio.canSendDTMF)
    outboundAudio.insertTones("**123", ...);


Having the same MediaStream magically change type feels just weird. To be
compared to

pc.addStream(stream);
if (pc.canSendDTMF(...))
  pc.sendDTMF(...);


I agree that the second example won't win any prices for "Best designed API
of the year" but it is infinitely simpler and to the point.

On Fri, Nov 9, 2012 at 1:14 PM, Adam Bergkvist
<adam.bergkvist@ericsson.com>wrote:

> Hi
>
> A while back I sent out a proposal [1] on API additions to represent
> streams that are sent and received via a PeerConnection. The main goal was
> to have a natural API surface for the new functionality we're defining
> (e.g. Stats and DTMF). I didn't get any feedback on the list, but I did get
> some offline.
>
> I've updated the proposal to match v4 of Travis' settings proposal [2] and
> would like to run it via the list again.
>
> Summary of the main design goals:
> - Have a way to represent a stream instance (witch tracks) that are sent
> (or received) over a specific PeerConnection. Specifically, if the same
> stream is sent via several PeerConnection objects, the sent stream is
> represented by different "outbound streams" to provide fine grained control
> over the different transmissions.
>
> - Avoid cluttering PeerConnection with a lot of new API that really
> belongs on stream (and track) level but isn't applicable for the local only
> case. The representations of sent and received streams and tracks (inbound
> and outbound) provides the more precise API surface that we need for
> several of the APIs we're specifying right now as well as future APIs of
> the same kind.
>
> Here are the object structure (new objects are marked with *new*). Find
> examples below.
>
> AbstractMediaStream *new*
> |
> +- MediaStream
> |   * WritableMediaStreamTrackList (audioTracks)
> |   * WritableMediaStreamTrackList (videoTracks)
> |
> +- PeerConnectionMediaStream *new*
>     // represents inbound and outbound streams (we could use
>     // separate types if more flexibility is required)
>     * MediaStreamTrackList (audioTracks)
>     * MediaStreamTrackList (videoTracks)
>
> MediaStreamTrack
> |
> +- VideoStreamTrack
> |  |
> |  +- VideoDeviceTrack
> |  |   * PictureDevice
> |  |
> |  +- InboundVideoTrack *new*
> |  |   // inbound video stats
> |  |
> |  +- OutboundVideoTrack *new*
> |      // control outgoing bandwidth, priority, ...
> |      // outbound video stats
> |      // enable/disable outgoing (?)
> |
> +- AudioStreamTrack
>    |
>    +- AudioDeviceTrack
>    |
>    +- InboundAudioStreamTrack *new*
>    |   // receive DTMF (?)
>    |   // inbound audio stats
>    |
>    +- OutboundAudioStreamTrack *new*
>        // send DTMF
>        // control outgoing bandwidth, priority, ...
>        // outbound audio stats
>        // enable/disable outgoing (?)
>
> === Examples ===
>
> // 1. ***** Send DTMF *****
>
> pc.addStream(stream);
> // ...
>
> var outboundStream = pc.localStreams.getStreamById(**stream.id<http://stream.id>
> );
> var outboundAudio = outboundStream.audioTracks[0]; // pending syntax
>
> if (outboundAudio.canSendDTMF)
>     outboundAudio.insertTones("**123", ...);
>
>
> // 2. ***** Control outgoing media with constraints *****
>
> // the way of setting constraints in this example is based on Travis'
> // proposal (v4) combined with some points from Randell's bug 18561 [3]
>
> var speakerStream; // speaker audio and video
> var slidesStream; // video of slides
>
> pc.addStream(speakerStream);
> pc.addStream(slidesStream);
> // ...
>
> var outboundSpeakerStream = pc.localStreams
>         .getStreamById(speakerStream.**id);
> var speakerAudio = outboundSpeakerStream.**audioTracks[0];
> var speakerVideo = outboundSpeakerStream.**videoTracks[0];
>
> speakerAudio.priority.request(**"very-high");
> speakerAudio.bitrate.request({ "min": 30, "max": 120,
>                                "thresholdToNotify": 10 });
> speakerAudio.bitrate.onchange = speakerAudioBitrateChanged;
> speakerAudio.**onconstraintserror = failureToComply;
>
> speakerVideo.priority.request(**"medium");
> speakerVideo.bitrate.request({ "min": 500, "max": 1000,
>                                "thresholdToNotify": 100 });
> speakerAudio.bitrate.onchange = speakerVideoBitrateChanged;
> speakerVideo.**onconstraintserror = failureToComply;
>
> var outboundSlidesStream = pc.localStreams
>         .getStreamById(slidesStream.**id);
> var slidesVideo = outboundSlidesStream.**videoTracks[0];
>
> slidesVideo.priority.request("**high");
> slidesVideo.bitrate.request({ "min": 600, "max": 800,
>                               "thresholdToNotify": 50 });
> slidesVideo.bitrate.onchange = slidesVideoBitrateChanged;
> slidesVideo.onconstraintserror = failureToComply;
>
>
> // 3. ***** Enable/disable on outbound tracks *****
>
> // send same stream to two different peers
> pcA.addStream(stream);
> pcB.addStream(stream);
> // ...
>
> // retrieve the *different* outbound streams
> var streamToA = pcA.localStreams.**getStreamById(stream.id);
> var streamToB = pcB.localStreams.**getStreamById(stream.id);
>
> // disable video to A and disable audio to B
> streamToA.videoTracks[0].**enabled = false;
> streamToA.audioTracks[0].**enabled = false;
>
> ======
>
> Please comment and don't hesitate to ask if things are unclear.
>
> /Adam
>
> ----
> [1] http://lists.w3.org/Archives/**Public/public-webrtc/2012Sep/**
> 0025.html<http://lists.w3.org/Archives/Public/public-webrtc/2012Sep/0025.html>
> [2] http://dvcs.w3.org/hg/dap/raw-**file/tip/media-stream-capture/**
> proposals/SettingsAPI_**proposal_v4.html<http://dvcs.w3.org/hg/dap/raw-file/tip/media-stream-capture/proposals/SettingsAPI_proposal_v4.html>
> [3] https://www.w3.org/Bugs/**Public/show_bug.cgi?id=15861<https://www.w3.org/Bugs/Public/show_bug.cgi?id=15861>
>
>
Received on Monday, 12 November 2012 13:08:31 GMT

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