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Re: Update of Doohickey/AddTrack proposal

From: Justin Uberti <juberti@google.com>
Date: Thu, 19 Dec 2013 14:04:32 -0800
Message-ID: <CAOJ7v-1J2jmK+GhWrmfEo-asgzJQh9_9OuhdfNace=GMdBaM0g@mail.gmail.com>
To: Harald Alvestrand <harald@alvestrand.no>
Cc: "public-webrtc@w3.org" <public-webrtc@w3.org>
Right. I don't understand the distinction between your event.streams and my
suggestion of event.track.streams. Either way, the track learns all the
streams.



On Thu, Dec 19, 2013 at 1:45 PM, Harald Alvestrand <harald@alvestrand.no>wrote:

> On 12/19/2013 07:12 PM, Martin Thomson wrote:
>
>> I think that you need to talk a little bit about how you plan to
>> manage the difference between send and receive tracks.
>>
>> The onaddtrack (which I think would be even clearer as onremotetrack)
>> needs a description of its arguments.  I think that those should be:
>>
>> interface RemoteTrackEvent : Event {
>>    readonly attribute RtpReceiver receiver;
>>    readonly attribute MediaStreamTrack track;
>>    readonly attribute MediaStream[] streams;
>> };
>>
>> The stream here is important.  This makes onaddstream polyfill
>> actually possible.  It's otherwise impossible to learn what stream is
>> being sent.  The fact that a single track can be part of multiple
>> streams means that you need this to be cardinality n.
>>
>
> If the track has a property saying which streams it is in (which our
> implementation found that it needed internally when a track could be a
> member of multiple streams, so it's easy to expose it through the API), the
> RemoteTrackEvent doesn't need the MediaStream[] streams property.
>
>
>
>> On 18 December 2013 19:35, Justin Uberti <juberti@google.com> wrote:
>>
>>> Based on some feedback I've received, I've slightly updated my proposal
>>> (originally inspired by Martin) on doohickeys and replacing AddStream
>>> with
>>> AddTrack. See below:
>>>
>>> ------------------------------------------------------------------------
>>>
>>> I suggest we call the SendDoohickeys RtpSenders and the corresponding
>>> receive-side objects RtpReceivers. 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 RtpSender as a return value from AddTrack (which replaces
>>> AddStream). You get a RtpReceiver as an argument to the new onaddtrack
>>> callback (which replaces onaddstream). The actual track object can be
>>> obtained as a property from the RtpReceiver (see below).
>>>
>>> For getting access to ICE/DTLS info, both RtpSenders and RtpReceivers can
>>> also have a reference to a DtlsTransport 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:
>>>
>>> interface DtlsTransport {
>>>    attribute RTCIceConnectionState state;
>>>    attribute sequence<ArrayBuffer> remoteCertificates;
>>>    //... more stuff as needed
>>> };
>>>
>>> interface RtpSender {
>>>    readonly attribute MediaStreamTrack track;
>>>    readonly attribute DtlsTransport transport;
>>>    // various tweakable attributes
>>>    attribute bool active;  // controls "am I sending RTP"
>>>    attribute PriorityLevel priority;  // for relative bandwidth
>>> allocation
>>>    // for multiple encodings: simulcast (audio or video), layered coding
>>>    // specify the codec to use, resolution, bitrate, and any
>>> dependencies for
>>> each encoding
>>>    attribute sequence<EncodingParams> encodings;
>>> };
>>>
>>> interface RtpReceiver {
>>>    readonly attribute Transport transport;
>>>    readonly attribute MediaStreamTrack track;
>>>    // more stuff as needed
>>> };
>>>
>>> partial interface PeerConnection {
>>>    RtpSender addTrack(MST);  // replaces addStream
>>>    void removeTrack(RtpSender);  // replaces removeStream
>>>    readonly attribute sequence<RtpSender> senders;
>>>    readonly attribute sequence<RtpReceiver> receivers;
>>>    EventHandler onaddtrack;  // replaces onaddstream; onremovestream is
>>> not
>>> needed
>>> };
>>>
>>> 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 ---> Transport ---> (The Internet) --->
>>> Transport ---> 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 Transport; N is controlled by the
>>> policy specified for BUNDLE.
>>>
>>>
>
>
Received on Thursday, 19 December 2013 22:05:20 UTC

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