Howto:SAMwin: Potential problem with media negotiation: Difference between revisions

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SAMwin's job is doing media-relay between the caller and the operator phone.
SAMwin's job is doing media-relay between the caller and the operator phone. To easily forward RTP (to avoid transcoding) SAMwin tries to negotiate same audio codec on both call legs (incoming from caller and outgoing to operator phone).


To easily forward RTP (to avoid transcoding) SAMwin tries to negotiate same audio codec on both call legs (incoming from caller and outgoing to operator phone).
We have seen cases where this almost worked, except for the packet size/rate. SAMwin requested 30ms packet sizes, we offered 60ms.  In this situation, SAMwin endlessly tried to negotiate equal packet sizes. This only happens when there are ''LOCAL CODER settings'' the innovaphone configuration.  In this case, we enforce the packet size set in the ''local codec'' configuration.  


That almost worked in this case except for the packet size/rate.
The problem is easily fixed by adjusting the ''local codec config'' to identical values on all innovaphone devices, so that both call legs on held by SAMwin always use the same packet size.
 
The caller (gateway) did not change from 30ms to 60ms and the operator phone did not change from 60ms to 30ms.
 
That was due to different LOCAL CODER CONFIG on gateway and operator phone.
 
Only local coder config overrules the received offer.
 
SAMwin endlessly tried to equal packet interval on the two endpoints.
 
Fixed by ajusting local conder config to identical values.
 
This is a potential risk on all SAMwin scenarios!

Latest revision as of 18:27, 13 February 2012

SAMwin's job is doing media-relay between the caller and the operator phone. To easily forward RTP (to avoid transcoding) SAMwin tries to negotiate same audio codec on both call legs (incoming from caller and outgoing to operator phone).

We have seen cases where this almost worked, except for the packet size/rate. SAMwin requested 30ms packet sizes, we offered 60ms. In this situation, SAMwin endlessly tried to negotiate equal packet sizes. This only happens when there are LOCAL CODER settings the innovaphone configuration. In this case, we enforce the packet size set in the local codec configuration.

The problem is easily fixed by adjusting the local codec config to identical values on all innovaphone devices, so that both call legs on held by SAMwin always use the same packet size.

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