Communicator and Mac Messenger Video Protocol support – H.263

The question that was asked: How come Communicator works with the Polycom HDX solution but not Mac Messenger?

Office Communicator supports both RTVideo and H.263 and it is the later codec that the Polycom HDX solution works with today. The codec is the result of a library being supplied by Intel of which there is no equivalent for the Mac.

<March 23 edit - You never want to omit folks that help you with a discussion and alas I did omit Steve Lessard unintentionally. Thanks Steve >

<March 22 edit - including the additional details below>

Mike Stacy with Polycom followed up with me on this and noted that the client is showing the protocol in the SDP, turns out this is a bug with the shipping 7.x client. The bug being that Mac Messenger advertises the protocol while it does not support it. Here is the log output he shared with me -

User-Agent: UCCP/2.0.6362.0 MM/7.0.4663.2 (Mac Messenger 7.0.2)


 a=rtpmap:121 x-rtvc1/90000

 a=rtpmap:34 H263/90000

 Calling from Mac Messenger to an HDX, the Mac just sends a BYE message with no error code anywhere in the SIP trace.

 Calling from the HDX to Mac Messenger you see the same codec in the invite:

 a=rtpmap:34 H263/90000 

But Mac Messenger rejects it with a 488…

Start-Line: SIP/2.0 488 Not Acceptable Here


User-Agent: UCCP/2.0.6362.0 MM/7.0.4663.2 (Mac Messenger 7.0.2)


Thanks Mike for the follow up.

November 4, 2010 Update - At this time there is no plan to include support for H.253 with the Mac client.


Comments (3)

  1. Anonymous says:


    I am not aware of QuickTime being a workaround/solution to the problem. I will monitor the bug to see what else I can find but this did not come up in the original discussion.

  2. Adam Jacobs says:

    Hi Tom,

    When visiting a Polycom stand at UC Expo, I was informed that whilst the HDX series display presence and contacts etc. it only uses the OCS infrastructure for signalling and video is setup using peer-to-peer H.263.

    They are great devices for any OCS or non-OCS enterprise. I blogged a little about them here

  3. John Heckendorn says:

    Isn’t H.263 encoding/decoding supported through QuickTime? Is there a way for Messenger 7.x to leverage QT for this purpose?

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