best codec for my hardware

Discussion in '3CX Phone System - General' started by cvdm, Mar 5, 2008.

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  1. cvdm

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    Hi

    Our phone system has the following configuration
    3cx 3.1.2434.0
    gxp2020
    x-lite
    patton sn4960 e1 gateway

    GXP supports the following codecs
    gsm , g.723.1 , g.729a/b , pcmu, pcma, g.726-32, g.722 (wide band), ilbc.

    patton supports transparent, g711alaw64k, g711ulaw64k, g723, g726, g727, netcoder, g729

    3cx supports (from 3cx site)
    * GSM - 13 Kbps (πλήρης ρυθμός μετάδοσης), μέγεθος πλαισίου 20ms
    * iLBC - 15Kbps, μέγεθος πλαισίου 20ms: 13.3 Kbps, μέγεθος πλαισίου 30ms
    * ITU G.711 - 64 Kbps, με βάση το δείγμα. Επίσης γνωστός ως alaw/ulaw
    * ITU G.722 - 48/56/64 Kbps
    * ITU G.723.1 - 5.3/6.3 Kbps, μέγεθος πλαισίου 30ms
    * ITU G.726 -16/24/32/40 Kbps
    * ITU G.728 - 16 Kbps
    * ITU G.729 - 8 Kbps, μέγεθος πλαισίου 10ms
    * Speex - 2.15 έως 44.2 Kbps
    * LPC10 - 2.5 Kbps
    * DoD CELP - 4.8 Kbps


    Which codec do you think is the best for this combination?
     
  2. igor.snezhko

    igor.snezhko Active Member

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    In internal network it is very preferably to use G.711. If you will connect you 3CX to VOIP provider - use G.729
     
  3. SY

    SY Well-Known Member
    3CX Support

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    Please give me a "link" where I can read that following CODECs are supported:
    * ITU G.722 - 48/56/64 Kbps
    * ITU G.723.1 - 5.3/6.3 Kbps, μέγεθος πλαισίου 30ms
    * ITU G.726 -16/24/32/40 Kbps
    * ITU G.728 - 16 Kbps
    * LPC10 - 2.5 Kbps
    * DoD CELP - 4.8 Kbps


    Thanks
     
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  4. bluefox8080

    bluefox8080 New Member

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    Since only Version 5 and up supports G729 I would say your best bet would be:
    G711 for Internal network and iLBC or G711(depending on available bandwidth) to VoIP Providers
     
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  5. cvdm

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    Dear stepan:
    that was the link:
    http://www.3cx.gr/voip-sip/codecs.php
    after reading it again i realized that this is general info on codecs, not codecs supported by 3cx. my mistake

    Dear Hannes
    These is no voip provider. Outgoing calls are routed via e1/pri interface to voice provider. Patton (e1 gateway) is configured with g711ulaw64k as the only available codec, so are gxp (pcmu) and xlite. The selection was based on the fact that this and g711alaw are the only one in common on all three (3cx,patton,gxp). I removed g711a from available codecs, so as to avoid possible negotiation problems or other (my opinion i dont say that i have read or experienced problems). I want to know if this is the best choise.

    Thank you both
     
  6. bluefox8080

    bluefox8080 New Member

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    Hi cvdm,

    Yes, your setup is 100%
    G711 will provide the best voice quality.

    Regards
     
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  7. SY

    SY Well-Known Member
    3CX Support

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    Hi Denis,

    G711 (PCMU/PCMA) provides highest quality and requires almost nothing form CPU. If traffic is not a bottleneck (local area network connection form PBX to gateway ) then use it.

    Thanks
     
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  8. landfiets

    landfiets New Member

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    PCMU is one of the most used codec. Most phones are on default on that one or G729. So use it with PCMU and only in strange probs you change it to PCMA. The difference between those two codecs I wrote in a topic on this forum.


    .....quote.............There are two versions: A-law and U-law. U-law is indigenous to the T1 standard used in North America and Japan. The A-law is indigenous to the E1 standard used in the rest of the world. The difference is in the method the analog signal being sampled. In both schemes, the signal is not sampled linearly, but in a logarithmic fashion. A-law provides more dynamic range as opposed to U-law. The result is a less 'fuzzy' sound as sampling artifacts are better supressed..........
     
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  9. cvdm

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    Maybe then i should change to a-law since my line is e1. Do you think that this would cure my problems (lines drop)?
     
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