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Re: Update of RTCRtpSender "doohickey" proposal

From: Peter Thatcher <pthatcher@google.com>
Date: Mon, 28 Apr 2014 09:33:04 -0700
Message-ID: <CAJrXDUG0uZWGGo7+xG81JR=sLrbv+bc_v86dUVywG_+S4o6MSA@mail.gmail.com>
To: Justin Uberti <juberti@google.com>
Cc: "public-webrtc@w3.org" <public-webrtc@w3.org>
I like the addition of the streamId to addTrack and stream to
RemoteTrackEvent.  It fixes the issues discussed before about tracks and
streams in a simple way.  Just a few questions about it:

1.  Does the streamId need to be the ID of an already existing stream?  Or
can it be an arbitrary value chosen by the JS?

2.  Would it make sense to allow streamId to be optional, such that it's
possible to simply call addTrack(track) and have it just work?  Or are the
dragons with that?


And I think the RTCRtpEncodingParams on the knobs inside of it are
potentially a very large conversation. I think the
addTrack/RtpSender/RtpReceiver/DtlsTransport is good enough by itself that
it shouldn't be blocked by getting the knobs inside of RTCRtpEncodingParams
perfect.



On Mon, Apr 28, 2014 at 8:58 AM, Justin Uberti <juberti@google.com> wrote:

> Update of the proposal from earlier this year, addressing the feedback
> from the list. Mainly, the issues with AddStream and AddTrack have been
> resolved by adding an explicit |stream| parameter to AddTrack.
>
>
> ------------------------------------------------------------------
>
>
> I suggest we call the SendDoohickeys RTCRtpSenders and the corresponding
> receive-side objects RTCRtpReceivers. These objects allow control of how a
> MediaStreamTrack is encoded and sent on the wire, including "hold" state,
> prioritization, and multiple encodings (e.g. simulcast).
>
> You get a RTCRtpSender as a return value from AddTrack (which replaces
> AddStream). You get a RTCRtpReceiver as an argument to the new onaddtrack
> callback (which replaces onaddstream). The actual track object can be
> obtained as a property from the RTCRtpReceiver (see below).
>
> For getting access to ICE/DTLS info, both RTCRtpSenders and
> RTCRtpReceivers can also have a reference to a RTCDtlsTransport object,
> which will have its own state variables, including the
> RTCIceConnectionState of that particular transport, and the
> .remoteCertificates for the DTLS connection. This allows applications to
> monitor the state of individual transports, as well as inspect the
> certificates for individual transports.
>
> The actual interface is as follows:
>
> // used with RTCRtpSender
>
> interface RTCDtlsTransport {
>
>  attribute RTCIceConnectionState state;
>
>  sequence<ArrayBuffer> getRemoteCertificates();
>
>  //... more stuff as needed
>
> };
>
> // used with RTCRtpSender
>
> interface RTCRtpEncodingParams {
>
>     double               priority = 1.0;  // relative priority of this
> encoding
>
>     unsigned int       maxBitrate = null;  // maximum bits to use for this
> encoding
>
>     boolean             active;  // sending or "paused/onhold"
>
> };
>
> // the "send" doohickey
>
> interface RTCRtpSender {
>
>  readonly attribute MediaStreamTrack track;
>
>  readonly attribute RTCDtlsTransport transport;
>
>  // 1-N encodings; in the future, N can be > 1, for simulcast or layered
> coding
>
>  // Each EncodingParams specifies the details of what to send (e.g.
> bitrate)
>
>  sequence<RTCRtpEncodingParams> getEncodings();
>
> };
>
> // the "receive" doohickey
>
> interface RTCRtpReceiver {
>
>   readonly attribute RTCDtlsTransport transport;
>
>   readonly attribute MediaStreamTrack track;
>
>   // more stuff as needed
>
> };
>
> // parameter to the onaddtrack event
>
> interface RemoteTrackEvent : Event {
>
>  readonly attribute RtpReceiver receiver;
>
>  readonly attribute MediaStreamTrack track;
>
>  readonly attribute MediaStream stream;
>
> };
>
> partial interface RTCPeerConnection {
>
>  // because a track can be part of multiple streams, the id parameter
>
>   // indicates which particular stream should be referenced in signaling
>
>  RtpSender addTrack(track, streamId);  // replaces addStream
>
>
>
>  void removeTrack(RtpSender);  // replaces removeStream
>
>  sequence<RtpSender> getSenders();
>
>  sequence<RtpReceiver> getReceivers();
>
>  EventHandler onaddtrack;  // replaces onaddstream; event object is
> RemoteTrackEvent.
>
>                                         // note that onremovestream is not
> needed, since tracks are 'removed'
>
>                                         // simply by progressing to the
> ENDED state
>
> };
>
> For backcompat, addStream, removeStream, getLocalStreams,
> getRemoteStreams, and onaddstream can be trivially polyfilled in JS, so
> there is minimal impact on current applications.
>
> All together, the pipeline looks like this:
>
> Source ---> MST ---> RtpSender ---> DtlsTransport ---> (The Internet) --->
> DtlsTransport ---> RtpReceiver ---> MST ---> <video/>
>
> Each RtpSender/Receiver references a single MST, although a single
> RtpSender/Receiver can send/receive multiple encodings (e.g. simulcast).
>
> There are N RtpSenders/Receivers per DtlsTransport; N is controlled by the
> policy specified for BUNDLE.
>
>
Received on Monday, 28 April 2014 16:34:12 UTC

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