H.264 AVC and SVC UCConfig Modes RRS feed

  • Question

  • The [MSFT-H264UCConfig] doc described the UCConfig Modes 0,1,2,3

    where in the SDP is the UCConfig Mode specified?  For eg.,

    m=video 10010 RTP/AVP 122 121 123
    a=rtcp-fb:* x-message app send:src,x-pli recv:src,x-pli
    a=rtpmap:122 X-H264UC/90000
    a=fmtp:122 packetization-mode=1;mst-mode=NI-TC
    a=rtpmap:121 x-rtvc1/90000
    a=x-caps:121 263:1920:1080:30.0:2000000:1;4359:1280:720:30.0:1500000:1;8455:640:480:30.0:600000:1;12551:640:360:30.0:600000:1;16647:352:288:15.0:250000:1;20743:424:240:15.0:250000:1;24839:176:144:15.0:180000:1
    a=rtpmap:123 x-ulpfecuc/90000

    We are trying to send a SDP to Lync 2013 client to indicate that only UCConfig Mode 0 is supported.

    From what I read UCConfig Mode 0 can be used to inter operate with nodes which does not support H264-SVC. Is this true?


    Monday, January 6, 2014 7:16 PM


All replies

  • Hello Sarbx,
                     Thank you for your inquiry about Lync protocols. One of the Open specifications team member will contact you shortly.

    Sreekanth Nadendla
    Microsoft Windows Open specifications

    Monday, January 6, 2014 8:57 PM
  • Hi sarbx,

    I believe what you are referring to is discussed in [MS-SDPEXT] Representing new Payload Types. Specifcally, the table entry for H264UC. I need to confirm that this corresponds to the UCConfig Mode so I will post again soon to confirm.

    Best regards,
    Tom Jebo
    Escalation Engineer
    Microsoft Open Specifications

    Monday, January 6, 2014 9:50 PM
  • Hello Tom,

    The UCConfig Modes within H264UC are 0,1,2,3 as mentioned in [MSFT-H264UCConfig] 

    The SDPEXT only talks about how to use the payload type H264UC. We are trying to find out how to set the UCConfig modes.

    Please let us know what you find out.


    Friday, January 10, 2014 3:55 AM
  • Thank you for clarifying. 


    Friday, January 10, 2014 5:43 AM
  • Please let us know if you need any more clarifications.


    Thursday, January 16, 2014 1:09 AM
  • Will do sarbx.  I'm still working on it. 


    Thursday, January 16, 2014 3:24 AM
  • We found something in MS-RTP Extensions -> RTCP Feedback message -> Video Source Request (VSR)

    that the UCConfig mode is set in the RTCP feedback messages sent by the receiver,

    UCConfig Mode (1 byte): The maximum UCConfig Mode the receiver supports.

    Is this (RTCP feedback) the way to set the UCConfig mode? and the sender is supposed to use this information and fall back to a lower level?

    Another question is that the same doc says,

    The UCConfig model value is defined as follows:

    0: MUST NOT be used.

    1: UCConfig Mode 1.

    2 or larger: MUST NOT be used.

    Is UCConfig mode 1 the only supported mode?

    Saturday, January 25, 2014 1:37 AM
  • Hi sarbx,

    I've confirmed that only UCConfig mode 1 is supported.  UCConfig mode 0 will not be seen by the sender when going through Lync servers.

    I hope that helps to clarify.


    Tuesday, January 28, 2014 5:17 AM
  • I understand that between 2 Lync client's and Lync Server only UCConfig Mode 1 is used. We are trying to interoperate Lync 2013 with our own MCU and clients which support H264-AVC (UCConfig Mode 0). The UCConfig doc suggests that UCConfig Mode 0 should be used to interoperate with MCU's which only support AVC. But the MS-RTP document is contradicting by suggesting that only mode 1 is supported. So we are still not clear about the following questions,

    - How does the clients negotiate the UCConfig Mode?

    - If they negotiate using the RTCP Feedback message(VSR), then would the sender respect the receiver sending UCConfig Mode 0?

    - We came to know that Cisco VCS 8.1 has interoperated with Lync 2013 with help from Microsoft ( If you can provide some more details on that or some other pointers to interoperate with Lync 2013, that will be really useful.


    Wednesday, January 29, 2014 2:55 AM
  • Hi sarbx,

    Sorry for the delay in getting back to you on this.  I have a follow up question for clarification.  You had mentioned, "The UCConfig doc suggests that UCConfig Mode 0 should be used to interoperate withMCU's which only support AVC." Can you point out the reference(s) which suggest this?


    Monday, February 17, 2014 10:45 PM