[Opalvoip-user] OLC extendedVideo (SessionId=0) from Polycom, Opal Ack with SessionID=1 - Leading to Audio Failure

[Satya S. <ss...@fu...>]

Hi Robert,

The H2250LogicalChannelAckParameters in src/asn/h245.asn has sessionID
constraints set to 1..255:
sessionID   INTEGER(1..255) OPTIONAL

Due to this the OLC Ack to the extendedVideo OLC from Polycom with
SessionID=0 is responded with sessionID=1.

The gatekeeper sitting between the Polycom and opal on seeing this Ack
starts sending the audio Session 1 RTP to the new destination that was
actually meant for the extendedVideo.

Here is a hack that I applied to force setting the sessionID to a value
other than 1 ensuring the audio continued with the original OLC Ack port.
This hack fixes the problem but this is not the right fix. I tried changing
the constraints but that leads to some Ack failures.

+++ opal-3.14/src/h323/channels.cxx 2014-07-09 19:02:32.236630005 +0530
@@ -563,6 +563,8 @@
   const H245_H2250LogicalChannelParameters & openparam =

open.m_forwardLogicalChannelParameters.m_multiplexParameters;
   unsigned sessionID = openparam.m_sessionID;
+  if(sessionID == 0)
+      sessionID = 100;
   param.m_sessionID = sessionID;

   OnSendOpenAck(param);

Thanks,
-Satya