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RE: Proposal: RtpListener for unsignalled ssrcs

From: Bernard Aboba <Bernard.Aboba@microsoft.com>
Date: Thu, 13 Feb 2014 22:57:22 +0000
To: IƱaki Baz Castillo <ibc@aliax.net>
CC: Emil Ivov <emcho@jitsi.org>, "public-orca@w3.org" <public-orca@w3.org>
Message-ID: <ab84b04304624708bc8e509ab78b6596@SN2PR03MB031.namprd03.prod.outlook.com>
Inaki said: 

"How can the receiver know which media type and codec are in use?

This is:

- Alice signals its media info to Bob, and includes info for Bob to set in the RTP header extension (in case Bob wants to send media to Alice even before Alice receives the media info signaling from Bob).

- Alice starts receiving RTP packets (the N first ones include such a negotiated RTP header extension).

- How can Alice know which codec do those RTP packet include?

Do I miss something?"

[BA]  Since media can arrive prior to receipt of the answer, Alice should configure the RTCRtpReceiver objects, based on the information that it will send in the Offer.  

For example, this would include configuring the Payload Type, Codec and RTP extensions such as the recv-appId (see http://tools.ietf.org/html/draft-even-mmusic-application-token Section 3.1.3).  

Since the SSRC is chosen by the sender, Alice will not know the SSRCs that Bob will be using until the Answer (or media) arrives.  
Received on Thursday, 13 February 2014 22:57:56 UTC

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