Codec Voice Payload Size

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Jun 26th, 2009
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Hi all,

I have a cuscomer that is migrating all branch connection to dsl circuits, since dsl use atm encapsulation and in order to reduce the impact for the atm encapsulation we will change the voice codec paylod size to 30 for g729. My question is:

Thoes the voice codec paylod size must be the same betwen all end points in a voip call ?, we need to change also the paylod size on the mgcp remote gateways and in all the trancoding/conference resources ?

Many Thanks.

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mchin345 Thu, 07/02/2009 - 06:11
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The voice payload size per packet can be configured in Cisco CallManager and Cisco IOS gateways. PreferredG729MillisecondPacketSize-(Default setting: 20 ms. Available settings: 10, 20, 30, 40, 50, and 60 ms.). When you increase the voice payload size the VoIP bandwidth reduces and the overall delay increases.

Configuring Voice Payload Sizes in Cisco CallManager and IOS Gateways:

patcbr600 Thu, 07/02/2009 - 06:22
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My question is that if i have to change it on both ends of a call.If i have a phone that calls to the pstn via a cisco mgcp gateway, if i change the payload size on the callmanager for the ipphone i also have to change on the gateway otherise i will have diferente framing size for both ends of the call.


marshall.d.higg... Thu, 07/02/2009 - 22:54
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Yes, if you do not the transcoders will be used to perform transrating from 20 ms to 30 ms. Not a desireable impact.


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