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VSX 8000 and Graqndstream GVC3200

Occasional Visitor

VSX 8000 and Graqndstream GVC3200



I'm trying to make an audio+video call between a VSX 8000 and a Grandstream GVC3200.


The GVC3200 unit supports H323+H239 and SIP+BFCP.

The VSX 8000 unit is running firmware version


I tried to use SIP to make a call, but it failed to establish. Does the VSX 8000 w/ support SIP with video?


I then tried to make an H323 call, and it actually established. However, there was no audio or video flow (no RTP). There are no network/firewall issues.

I guess they're having trouble negotiating the codecs, or maybe even don't speak the same protocol.

I dumped a packet trace between them, but I'm not an H323 expert. I don't know how to determine what they disagree on. Would it be of any help if I posted the trace here?


Please note that I've successfully called from a GVC3200 to another brand/model, such as Cisco SX20 with both H323 and SIP. I also successfully called the same Cisco SX20 from the VSX 8000 with H323... So I don't see why I can't do the same with VSX 8000 and Grandstream GVC3200.


Thanks in advance,




Message 1 of 5
Polycom Employee & Community Manager

Re: VSX 8000 and Graqndstream GVC3200

Hello @VDP,

welcome to the Polycom Community.

The community's Video FAQ contains this post here:

  • Jun 21,2014 Question: Are there specific Ports in my firewall that I need to open in order to utilize video conferencing?

    Answer: Please check the relevant release notes or admin guide for your device under the section “Inbound and Outbound Ports” or "Port usage" => here <=. 

    In addition check this FAQ post => here <= for more details and troubleshooting suggestions.

The above FAQ post shows a Call Setup in H.323

Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.

Best Regards

Steffen Baier

Polycom Global Services


Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels.
Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's
Message 2 of 5
Occasional Visitor

Re: VSX 8000 and Graqndstream GVC3200



I went through the FAQ (very useful, thanks), and my trace seems to suggest that everything is going as expected until right after the last step in the FAQ.

How many openLogicalChannel and openLogicalChannelAck pairs am I supposed to see in a correct transaction?
I'm seeing several. These are the openLogicalChannel packets I see in sequence::

g711A, h224, g722-64k, genericVideoCapability, h224 (again)

These are the tsapIdentifier values for each one of these:

6005(endpoint1), 6011(endpoint1), 3231(endpoint2), 3233(endpoint2), 3235(endpoint2)

I also see 5 openLogicalChannelAck with the following tsapIdentifier pair values, in sequence:







Does this sound ok?


After the last openLogicalChannelAck packet, I don't see anything outright strange (I'm not an H323 expert though), except for this (repeated several times):


Payload type=RTP Event, Unknown (126)


Further down, I see lots and lots of messages such as:




PT=ITU-T G.722


There's nothing else really, until the call is manually terminated.

During the call, only audio seems to work. No video.


How can I debug this further?









Message 3 of 5
Occasional Visitor

Re: VSX 8000 and Graqndstream GVC3200

I think the VSX 8000 supports H.264 video. However, when it negotiates with the Grandstream GVC3200, it does not offer H.264, but H.263 and H.261 instead. That's according to what I could read in the terminalCapabilitySet exchanges.


Why is that?

How can I force Polycom to advertize H.264?


The Grandstream device offers the following:


standard: (h264 generic-capabilities) - ITU-T Rec. H.241 H.264 Video Capabilities




Message 4 of 5
Occasional Visitor

Re: VSX 8000 and Graqndstream GVC3200

By the way, what should I look for in the traffic trace to find out which video codec was actually selected after the endpoints advertised their capabilities?

I'd like to know if H.264 or H.263 was finally agreed upon, etc..


Message 5 of 5