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Codec setup G.729 phone via SBC to PBX

Discussion in '3CX Phone System - General' started by de13, Feb 20, 2018.

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  1. de13

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    Hi,

    we have a customer that is using a hosted Linux 3CX installation (8 Simultaneous Calls) with the latest version.
    Phones connect to the PBX we use a SBC.
    We experience conversations that are broken down. The Bandwidth at the location is not high, so we switched G.729 on all devices (8). However, there is no change. Should G.729 be activated on the PBX under the siptrunk, Codec Priority? (active: G.711 A-law/ G.711 U-law/ GSM-FR) Or do we miss something else?

    phone (G729) --------> SBC ----------> Linux 3CX v15.5sp3 ------------> Trunk

    Thanks in advance!

    Roger
     
  2. leejor

    leejor Well-Known Member

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    Is recording being utilised? I seem to recall that doing an override on the Codec choice.
     
  3. de13

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    nope, no recording.
     
  4. YiannisH_3CX

    YiannisH_3CX Support Team
    Staff Member 3CX Support

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    Hello @de13

    Do you experience the issue only with calls that come from the provider? How about extension to extension calls? Try registering an extension on a mobile device and connect to the PBX using 3G/4G and try a call to another extension. Do you have bad audio there?

    There are 2 legs to a call going to a provider. The phone to the PBX and the PBX to the provider. These legs could have different codecs with the PBX doing the transcoding. Make sure that the phones have been re-provisioned once the codecs are changed so the changes are applied.
    You should also know if the provider you are using supports G729 or not as not all providers support this codec.
     
  5. leejor

    leejor Well-Known Member

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    Each direction will dictate the Codec used, when a call is initiated, based on the Codec priority, going down the list until one can be agreed upon. You could try eliminating all but G729 in one set, to see if calls are able to be completed (with audio) through the SBC, in both directions. As mentioned, if your trunk provider does not support that Codec, then the Activity Log will show transcoding as G729 is converted to a Codec used by the provider.
     
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