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Thread: Optimize codec for different call types.

  1. #1


    We have a Quadro4x and would like to use different codecs in different situations.
    For calls: PSTN <-> FXO <-> IP Phone
    we want to make sure the SIP segment of the call is using PCM.
    For calls: PSTN <-> ITSP <-> IP Phone
    we want to make sure the codec used id G729, to minimize bandwidth used and therefore allow a greater number of concurrent calls.

    If I set the IP Line extension codec priorities to G729 then the PSTN calls only use G729, but if I set the priority to PCM then the ITSP calls use PCM when I'd rather they use G729 - I also have the ITSP extension codec priorities so G729 is top.

    I am using Aastra 480i IP Phones.

    Any tips on how I can achieve the desired result?

  2. #2


    You can set the preferred codecs of local extensions to G.711u/a. Then
    set the preferred codecs of virtual extension (eg. ext 79) where you
    have setup the ITSP (via VoIP carrier wizard or manually) to G.729a.

    Then in the call routing entries where you would like to use the ITSP
    trunk for outbound calls, select ext 79 in the "Use Extension
    Settings". This way when you make a VoIP call through your ITSP, it
    will use the preferred codec of ext 79, ie. G.729a. Whereas if the call
    is through FXO, the local extension's preferred codec is used, ie.

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