[Users] rtp relay & transcoding

Gang Liu gang_l at bol2000.com
Sat Jun 9 10:02:57 CEST 2007


Dear Sir,
    Why you need transcoding? It is heavy job for pc server.and you need pay for G.729 license.

    We use RTP relay too. But we write our own RTP relay server. It could handle more than 300 G.729 calls at once with a USD 800 linux pc. 
 
Best regards,
Gang Liu

  ----- Original Message ----- 
  From: Ryan Mitchell 
  To: Users at openser.org 
  Sent: Friday, June 08, 2007 10:50 PM
  Subject: [Users] rtp relay & transcoding


  Regarding RTP relay (e.g. media proxy), and transcoding --

  This topic has come up many times before in various forms, but I still have not found any obvious solution that's highly scalable and cheap (well sure, I can dream).  We have lots of customers behind various firewalls using various codecs.  Customers call each other (both parties behind firewall) and to/from carriers. 

  Certainly this is a common use-case.  What do you do?  What are best known practices?  Commercial media gateway, or open-source solutions?

  We use both OpenSER and a custom B2BUA written against the NIST Java stack.  We need a way to transcode when needed.  Obviosly mediaproxy module is great, but doesn't transcode. 

  Ideally, what I'm looking for:

  * at the point where our system determines that transcoding or rtp relay is needed, a media gateway is chosen based on network proximity (e.g.: 1/2 our customers are in the U.S., 1/2 in Brazil; should pick a media gateway accordingly to minimize network path).

  * our system then signals the media gateway (mgcp?) to setup the channels, and modifies the SDPs in the SIP path accordingly.

  * even more ideally: the media gateway signals our system with inband or rfc2833 dtmf events, plus rtcp reports when available.

  I think Asterisk could be hacked to do this.

  Does anyone know of a commercial product that's not too expensive?  Thoughts? Advice? 

  thanks,
  -- 
  Ryan Mitchell <rjm at tcl.net>
  Telecom Logic, LLC
  http://www.tcl.net 


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