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No audio until caller speaks RRS feed

  • Question

  • We're having a really strange issue on outbound calls. About half of the calls you will not be able to hear the other party speak until you talk. Once you say something audio in both directions works perfectly (either that or there is no audio for the first 4-5 seconds and it's just coincidence). So far I haven't had any reports of this happening on inbound calls.

    There are no errors in the logs and ocslogger isn't showing anything wrong that I can discern. 

    Any ideas?

    Wednesday, April 24, 2013 6:18 PM

All replies

  • Hi,

    what's the PSTN gateway that you use? make sure that it supports Early Media.




    Z-Hire -- Automate Lync User Account creation process ( AD / Exchange / Lync )

    Thursday, April 25, 2013 11:07 PM
  • Hi,

    Looks like something wrong with your gateway. Please restart the gateway device and check the issue again. If still can't work, please update the device firmware.


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    Sean Xiao
    TechNet Community Support

    Friday, April 26, 2013 3:04 AM
  • We're doing SIP trunking straight from our FE to our PTSN provider. We've been using them for years and this has just started recently. We've had some other issues with them recently though, so this could be another config mistake on their end.

    On that note, any good SIP trunking suggestions for Lync 2010 with a data center on the west coast US?


    • Edited by Shaun TPG Friday, April 26, 2013 4:03 PM
    Friday, April 26, 2013 4:02 PM
  • What's a Wireshark / Network Monitor capture of a call look like? Do you see RTP packets from the other side?

    James Waite, UC Consultant - Strencom http://blog.justuc.net

    Friday, April 26, 2013 11:58 PM
  • I must be doing something wrong with Wireshark because I'm not seeing any RTP packets at all and it's not registering that any voip calls happened during the capture. I'm running it from the computer I'm initiating an outbound Lync call from.

    Still having the issue where I need to talk to enable the inbound audio.

    Is there a capture I could get (ocslogger perhaps?) that one of you smarter, more handsome people could take a look at to help me figure this out?


    • Edited by Shaun TPG Tuesday, April 30, 2013 11:29 PM
    Tuesday, April 30, 2013 11:21 PM
  • We ran into the exact same problem with one of our SIP trunk providers. The issue turned out to be a "feature" on their side called NAT detection. Essentially, the SIP trunk provider gateway would ignore the SDP coming from Lync until an actual voice packet was sent so it can detect the public IP address/port the audio was coming from since it assumed the SDP would contain the internal IP address and would thus be wrong. Since Lync uses VAD (voice activity detection) it wouldn't send any voice packets until a user started talking. Of course the user wouldn't start talking until they heard the "Hello" from the callee which never came because the gateway was trying to establish the session based on the caler.

    Turning off the NAT detection and forcing the gateway to use the SDP data solved the issue. Of course your SDP has to be correct (i.e. public IP address and port)

    Monday, May 27, 2013 8:24 PM