re g729

Discussion in '3CX Phone System - General' started by callnetcenter, Aug 15, 2007.

  1. callnetcenter

    Aug 15, 2007
    Likes Received:
    I read somewhere, if I don't use the same codec in phone and in softere pbx the voice will be delayed, this seems to be happen with my 3cx. The voice is intrerupt and delayed. I' don't know why!?
    The conection of the internet is 2.5 Mb/s. I read the configure manul of 3cx phone system and the configure in the management console it's ok.
    But the problem with the voice is alwais the same.
    In codec voice I have added all codecs, my voip provider suports this codecs:
    G.711 (64 kbps)
    G.726 (32 kbps)
    G.729 (8 kbps)
    G.723 (5.3 & 6.3 kbps)
    iLBC (20ms & 30ms)
    and my voip phone Grandstream Budge Tone-100
    please tell me how can I choose the codecs on the 3cx system and voip phone to resolve this problem
  2. Anonymous

    Anonymous Guest

    PCM and G711 are one and the same

    So choose g711 in 3CX
    Choose PCMU or PCMA on your phone. Go for PCMA as it is the better one of the two.
  3. callnetcenter

    Aug 15, 2007
    Likes Received:
    a part of problem is resolved

    now, after I set in the voip phone first codec PCMA and in 3cx server I select G711 A, in my voip phone the quality of the sound is great, but the other part hear me to slow, i wait for an ideea

    thanks all
  4. tjabaut

    tjabaut New Member

    Jul 24, 2007
    Likes Received:
    what do you mean that remote party hears you too slow?

    g711 is the same protocol that the Baby Bells have used for years. This is an uncompressed 64Kbit protocol that is what you would find when you pick up an analog POTs line.

    Yes if you are using anything other than the codecs that 3cx supports the system will attempt to use a pass-thru mode where 3cx merely acts as a proxy and handles the call setup and tear-down, but passes that actual voice portion off to your voip provider.

    If you set your phone for instance to g711 and your voip provider ONLY supports gsm than the 3cx box will have to perform a process called transcoding that converts into a negotiated protocol. This would result in a lag, but in milliseconds.

    Your best best is to utilize g711u/a and ensure that you are prioritizing packets that are on your lan side. Once it hits the internet all bets are off as packets are lumped together with everyone else and no priority comes into play.

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