Polycom Viewstation to IP Phone or VTA

[kbyrd]

I am testing video between an H.323 Polycom Viewstation (version 7.4.5) and Call Manager 4.1.3 SR2. On the Call Manager side, the clients could be an IP Phone for a audio-only connection or with a CVTA for a video conference. I can call from the CVTA to the Polycom with no problem, however, I cannot successfully call from the Polycom to the Call Manager. (fast busy). For testing, I have all endpoints in the same DP with G711u audio. Now, I can call to/from a NetMeeting client with no problem. Here is what I think the problem is and I'm hoping there is a simple resolution: The Polycom has two audio codec setup options: G722 and G728. You establish a Bandwidth threshold in the set up of the Polycom to tell it which codec to use - below the threshold use G728. Above use G722. I think that there is a codec negotiation issue when the Polycom calls the Call Manager and not vice versa. Also note that the Polycom can call to/from the NetMeeting. I have tried defining the Polycom as an H.323 Client and via a Gatekeeper Trunk. Exactly the same issues. The only way I can get it to work is to have a Cisco Gatekeeper (IOS 12.3.12) proxy the call to the Call Manager. Then I can call to/from the Polycom from an IP Phone or the CVTA. This leads me down the path that the Call Manager has a codec negotiation issue if a Call comes in initially as G728 or G722.

I have verified CSSs and PTs. That is not the issue.

With this info, can someone recommend a command on the Polycom to setup calls with G711 - or a Call Manager service parameter tweak that would negotiate to G711u? Thanks.

[jleon22]

This is an interesting question. Maybe a transcoder is needed?

[jcounter]

I'm having the same problem, did you ever get this resolved?

Thanks

JCounter

[kbyrd]

Hi.The version of the Polycom I'm using is a Polycom Viewstation 512K running Release 7.5.4 - 04 Mar 2005. It appears that it will negotiate G729 and G722 when it sets up a call. It will also negotiate G711 when another endpoint calls it. I tried several options...the one that worked is where I found an old 2600 router and made it the Gatekeeper proxy for the Polycom. This is pre IP-IP gateway code. I think I was running 12.3.17a IX code. So I moved the video to it's own Gatekeeper. (The Call Managers have two gatekeepers.) I set up all of the inter-zone configurations....and it worked. There must be some h323 negotiation attribute in the Polycom that breaks the ability to talk to the Call Mgr. Put a Cisco proxy in-between, and things start to work. Sorry I don't have a more technical answer than that.

[jcounter]

Thanks. That helps, as we dont have a Cisco Gtkpr inline yet. Only a Radvision.

Thanks for the explanation!