Software vs Hardware echo cancelling?

Discussion in 'General' started by oshkosh, Aug 24, 2010.

  1. oshkosh

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    Hey everyone,

    So quick background, I have a Pentium 4 3.06Ghz CPU, 2 GB of ram running Elastix. I have a TDM400p card which is a clone of a Digium card with 4FXO ports and 4 analog lines connected to it.

    I have bad echo on almost all the different software cancellers, only mg2 seems to work but it breaks in and out sometimes, and I have a constant hiss or static on the line which I don't have if I plug a phone directly into the analog line. It's more noticeable to myself and not to external callers. Been playing for a week or so on tweaking settings but even when I get it sort of working, I always have some static and slight echo.

    Because it's a clone of a digium card it unfortunately doesn't look like it has the module to attach the hardware echo canceller to it so I'll have to buy an actual card. Was looking at Sangoma B600D which says it has 4 FXO, 1 FXS and hardware echo cancelleation. Was also looking at Rhino cards or actual Digium ones. The thing is $500+ is a lot to spend, but not really if it means great call quality. I'm just wondering what to expect with a hardware card. For example, does it pretty much mean there will be NO echo at all on the 4 lines? Or is there a chance I'll still get it plug it in and have echo for some random reason? Also does it do anything in terms of the static on the line or strictly echo? Thanks so much!
     
  2. dicko

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    I posted previously on your prior thread:

    http://www.elastix.org/component/kunena ... g=en#58088

    perhaps you didn't follow it.

    very briefly until your 2/4 wire hybrid is balanced neither hard or soft EC will work very well, that's just mathematics and physics.

    Your ear is way more adaptive as to level than the hardware you use (research psycho acoustics)

    When it is balanced, fxotune -i will send a pulse down an open pair of wires, listen to what happens and so allow the tuning of the the FFT (Fast Fourier Transform) either hard or soft to suit when fxotune -s is next run.

    IMHO throw your clone away or maybe put it in a microwave for 30 seconds and send it back for a refund , some are just noisy and inadequate, all cards are not created equal, Digium, Sangoma or Rhino all support their hardware and make quality products.

    If you end up with quality lines from the telco, quality FXO interfaces, an adequate hardware platform to run on (no vm's allowed) and is ONLY running the minimum of services, no OpenFire or GUI for example, everything will work fine, as it does for the rest of us.

    dicko
     
  3. ramoncio

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    Hi oshkosh,
    Read and absorb this document:

    http://www.x100p.com/support/doc/novavo ... issues.pdf

    It is a bit outdated, as it talks about zaptel, but it is really great to help you solve sound quality problems. All zaptel commands have their correspondency in dahdi.
     
  4. oshkosh

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    Dicko I followed it, I did all of that already it didn't help so I posted asking about hardware cards. Fxotune has really no effect, only very little, enough to know that it's definitely enabled but not enough to make it better.
     
  5. netaires

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    I have used fxotune and realy cancel eco. You should leave txgain and rxgain in 0.
    I have one OpenVox card.
     
  6. dicko

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    and the results of your milliwatt testing? what are your current rx and tx gains set at, despite some recent advice around here, dahdi is not part of asterisk, it is a hardware driver, and an asterisk reload is insufficient, you will normally need to successfully stop , and then restart dahdi, for any changes you made in the dahdi conf files to take effect

    dicko
     

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