[cisco-voip] Cm4.1-G729-VAD

[Bob A. Bowie]

What happens on calls to my H.323 PBX gateway, where I believe the VAD is 'enabled' by default?

Do you have a link to describe the difference in G.729, G.729a, G.729ab?

Is there any other option to improve or obtain the best quality on the G.729 codec?


Thanks,
Bob


  ----- Original Message ----- 
  From: Kevin Thorngren 
  To: Bob A. Bowie 
  Cc: cisco-voip at puck.nether.net 
  Sent: Wednesday, January 11, 2006 11:05 PM
  Subject: Re: [cisco-voip] Cm4.1-G729-VAD


  You will want to look at these CallManager Service Parameters:

  Silence Suppression : This parameter determines whether silence suppression is utilized. Valid values specify True (silence suppression is enabled for all devices) or False (silence suppression is disabled). 
  This is a required field.
  Default: false.

  Silence Suppression for Gateways : This parameter determines whether silence suppression for gateways is utilized. Valid values specify True (enable silence suppression for all devices on gateways) or False (disable silence suppression). 
  This is a required field.
  Default: false.

  Strip G.729 Annex B (Silence Suppression) from Capabilities : THIS PARAMETER MUST BE SET TO THE SAME VALUE ON EVERY NODE IN THE CLUSTER. This parameter determines whether the system will advertise or negotiate Annex B for G.729 codecs. Valid values specify True or False. If the parameter is set to True, the system will not advertise or negotiate Annex B for G.729 codecs, unless that is the only matching codec (G.729b or G.729ab). Annex B provides silence suppression. If you are using a device that only advertises G.729b and/or G.729ab, the potential exists for the call to fail due to a capabilities mismatch. If the system can detect the mismatch, it will try to connect the call with Annex B anyway; however, if the call involves an intercluster trunk, this may not be possible, and a transcoder may be allocated, or the call may fail. As the solution, reconfigure the device to support other capabilities (such as G.729 or G.729a) if possible. Also, remember that this service parameter works independently from the other systemwide parameters Silence Suppression and Silence Suppression for Gateways. Those parameters only determine whether silence suppression is enabled in Skinny (SCCP) and MGCP, but this setting does not affect the capabilities negotiation. Some devices will override the value of this parameter on the basis of the negotiated capability. 
  This is a required field.
  Default: false 

  Kevin
  On Jan 11, 2006, at 10:07 PM, Bob A. Bowie wrote:


    Is vad enabled when I use G.729 for the codec on the Call manager?
    If so, is there a way to diable it as on the router?
     
    Thanks,
    B_______________________________________________
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