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

[Kevin Thorngren]

Hi Bob,

This link may help to answer some of your questions:
http://www.cisco.com/en/US/tech/tk1077/ 
technologies_tech_note09186a00800b6710.shtml

This link describes the codecs supported by CCM:
http://www.cisco.com/en/US/products/sw/voicesw/ps556/ 
products_qanda_item09186a00801b34cc.shtml

If your H.323 PBX GW supports both G.729a (non-VAD) and G.729ab (VAD)  
then H.245 should be able to negotiate using G.729a to eliminate VAD if  
you set the "Strip G.729 Annex B (Silence Suppression) from  
Capabilities" parameter to true.

HTH,
Kevin

On Jan 12, 2006, at 12:11 AM, Bob A. Bowie wrote:

> 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_______________________________________________
>>> cisco-voip mailing list
>>> cisco-voip at puck.nether.net
>>> https://puck.nether.net/mailman/listinfo/cisco-voip
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: text/enriched
Size: 5012 bytes
Desc: not available
Url : https://puck.nether.net/pipermail/cisco-voip/attachments/20060112/22577a95/attachment.bin