default sample size for g729

convenientstoreconvenientstore MemberMember Posts: 53 ■■□□□□□□□□
I see conflicting information.

excerpt from "cisco press voip fundamental"

In the Cisco IOS VoIP product, the Digital Signal Processor (DSP) generates a speech sample every 10 ms when using G.729. Two of these speech samples (both with 10 ms of delay) are then placed within one packet. The packet delay is, therefore, 20 ms. An initial look-ahead of 5 ms occurs when using G.729, giving an initial delay of 25 ms for the first speech frame.


In Cisco CallManager, the voice payload size per packet is configurable on a systemwide basis. This attribute is set in Cisco CallManager Administration (Service > Service Parameters > select_server > Cisco CallManager) with the following three service parameters:


PreferredG711MillisecondPacketSize—(Default setting: 20 ms. Available settings: 10, 20, and 30 ms.)

PreferredG729MillisecondPacketSize—(Default setting: 20 ms. Available settings: 10, 20, 30, 40, 50, and 60 ms.)

PreferredG723MillisecondPacketSize—(Default setting: 30 ms. Available settings: 30 and 60 ms.)

I know one is just regarding DSP of any routers vs call manager but which one should be general answer ??


  • mikej412mikej412 Cisco Moderator Member Posts: 10,086 ■■■■■■■■■■
    Unless you are specifically asked about the 1st packet -- 20ms. For the delay and and for the amount of voice data in a packet.

    That's a good link to have bookmarked! icon_thumright.gif
    :mike: Cisco Certifications -- Collect the Entire Set!
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