W3C home > Mailing lists > Public > public-webrtc@w3.org > June 2013

Re: SDP wrapper? Object-oriented API?

From: tim panton <thp@westhawk.co.uk>
Date: Mon, 17 Jun 2013 11:38:33 +0100
Message-Id: <8A862DDC-AEBF-4814-9484-1177D0DCD4C5@westhawk.co.uk>
To: public-webrtc <public-webrtc@w3.org>
Here's a concrete example that came up a while back.
Imagine I have a webRTC app which wants to use the opus codec 
irrespective of the preferences of the far end device for Alaw because I've been getting quality complaints. 

Currently as a javascript coder I have to :
0) intercept the offer
1) look for an m=audio line
2) look for a subsequent a=rtpmap lines
3) remove all a=rtpmap lines that don't contain OPUS or telephone-event
4) rewrite the m=audio line so that it only contains the types for opus and telephone-event
5) make sure 2->4 only apply to lines before a subsequent m= line.
6) set the re-written offer as a  local description and send it.

That requires an excessive amount of telephony knowledge IMHO.

By the way, we have written a wrapper that makes this a bit easier:

https://github.com/phono/PhonoSDK/blob/master/modules/phono-js/src/main/js/phono.sdp.js 

but it still leaks SDP concepts.

Kaufman is not quite right in saying "y'all soundly rejected it" - I didn't, it was clear to me 
at the time that this would be a problem. All we can now do is try to mitigate it.


T.
Received on Monday, 17 June 2013 10:38:57 UTC

This archive was generated by hypermail 2.3.1 : Monday, 23 October 2017 15:19:33 UTC