Re: [rtcweb] My Opinion: Why I think a negotiating protocol is a Good Thing

Roman Shpount <roman@telurix.com> Thu, 20 October 2011 03:54 UTC

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Date: Wed, 19 Oct 2011 23:54:06 -0400
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From: Roman Shpount <roman@telurix.com>
To: Hadriel Kaplan <HKaplan@acmepacket.com>
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Subject: Re: [rtcweb] My Opinion: Why I think a negotiating protocol is a Good Thing
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One more reason not to use SDP is that there are non-negotiated CODEC
parameters and media stream parameters that generally come from some sort of
configuration, and not from SDP. Examples would be if audio stream should
run noise suppression, automatic gain control, echo canceller, in iLBC codec
that would be running enhancer, in SILK this would be complexity and
expected packet loss percent. It would make sense to provide some mechanism
to specify this.

As far as data format for media description is concerned we can have
something like this:

List of Media Stream Formats. Each contains:

   -     Media Type
   -     Transport (RTP vs SRTP vs DTLS-SRTP)
   -     List of name/value network attributes (ptime, crypto etc)
   -     List of name/value configuration attributes (AGC, EC, NS)
   -     List of formats. Each contains:


   - RTP payload type
   - Name (PCMU, PCMA, etc)
   - Clock Rate (8000, 16000)
   - Number of channels (mono, stereo, surround)
   - List of name/value network attributes (usedtx, maxaveragebitrate,
   bitrate)
   - List of name/value configuration attributes (iLBC enchancer, SILK
   complexity)

This can be easily mapped to/from SDP, and will provide a easy to work
structure for non-SDP based solutions.
_____________
Roman Shpount