Does anyone offer VOIP (SIP or IAX) dial-in numbers WITHOUT echocancellation

Discussion in 'UK VOIP' started by jrwalliker@gmail.com, Jul 24, 2008.

  1. Guest

    All I want is a UK (and maybe also a USA) dial-in number which
    forwards A-law (or ulaw in USA) audio packets from the PSTN to my
    asterisk server without changing the audio in any way. This means no
    echo cancellation.

    Can anyone offer such a service?

    I could do it myself with a group of ISDN2 lines or preferably an
    ISDN30 connection, but this is rather expensive.

    In any case, why do VOIP service providers insist on echo cancelling
    their connections when this job is best done at the end points?

    John
    , Jul 24, 2008
    #1
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  2. Dave Higton Guest

    Re: Does anyone offer VOIP (SIP or IAX) dial-in numbers WITHOUT echo cancellation

    In message <>
    wrote:

    > In any case, why do VOIP service providers insist on echo cancelling
    > their connections when this job is best done at the end points?


    I don't know; but here are some points to think about.

    VoIP shouldn't inherently have any echo. The acoustic path from
    earpiece to microphone is at a /very/ low level, surprisingly
    low, unless the incoming audio is on speakers - and in this case
    it would definitely be best done at the endpoint.

    Most echo is caused by imperfect termination of an analogue line.
    Any echo cancellation is easiest performed when the path delay
    is shortest. Look at the segments of a call, see which are
    analogue and which are VoIP, and then work out where the echo is
    best performed.

    Another point: acoustic paths are unpredictable and subject to
    variation as the speaker, microphone and other people and objects
    move around in a room, whereas imperfect analogue termination is
    constant over a very long period.

    Dave
    Dave Higton, Jul 24, 2008
    #2
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  3. wrote:
    > All I want is a UK (and maybe also a USA) dial-in number which
    > forwards A-law (or ulaw in USA) audio packets from the PSTN to my
    > asterisk server without changing the audio in any way. This means no
    > echo cancellation.
    >
    > Can anyone offer such a service?


    we do this

    --
    peter gradwell. gradwell dot com Ltd. http://www.gradwell.com/
    <email/web_hosting/business_voip> <t:01225 800 810>
    Peter Gradwell, Jul 24, 2008
    #3
  4. Guest

    On 24 Jul, 22:47, Peter Gradwell <> wrote:

    > we do this


    Peter,

    I'm very pleased to hear it as I am already one of your customers! I
    emailed your support staff the other day and received the following:

    >Subject: Case Update: 16090 - [g SUPPORT] Inbound uk number without echo cancellation?
    > Status: Closed
    > Link: Click here
    >Response:
    >Hi John,
    >
    >I have checked with our UK DID numbering providers and I am afraid we cannot offer this functionality.
    >
    >We can only disable echo cancellation on an E1 circuit basis and not on a per number basis.
    >
    >Please do let us know if we can assist you any further,
    >Regards,
    >
    >...
    >


    If there really is a way in which you could set some of my inbound
    numbers up (or create new ones specially for this purpose) without e/c
    that would be really useful.

    For the benefit of those who wonder "why?" - I'm doing automated
    testing of mobile handsfree echo cancellers using test software on an
    asterisk server. Having extra cancellers in the way just messes
    things up.

    Regards,

    John
    , Jul 25, 2008
    #4
  5. Guest

    On 24 Jul, 20:18, Dave Higton <> wrote:
    > VoIP shouldn't inherently have any echo.  The acoustic path from
    > earpiece to microphone is at a /very/ low level, surprisingly
    > low, unless the incoming audio is on speakers - and in this case


    With a standard BT badged phone on an "analogue" line I typicall see
    an echo return loss of about -25dB.

    John
    , Jul 25, 2008
    #5
  6. Dave Higton Guest

    Re: Does anyone offer VOIP (SIP or IAX) dial-in numbers WITHOUT echo cancellation

    In message <>
    wrote:

    > On 24 Jul, 20:18, Dave Higton <> wrote:
    > > VoIP shouldn't inherently have any echo.  The acoustic path from
    > > earpiece to microphone is at a /very/ low level, surprisingly
    > > low, unless the incoming audio is on speakers - and in this case

    >
    > With a standard BT badged phone on an "analogue" line I typicall see
    > an echo return loss of about -25dB.


    Sure, but my point is that that's caused by imperfect termination
    of the analogue line, and not by acoustic feedthrough from earpiece
    to microphone.

    Dave
    Dave Higton, Jul 25, 2008
    #6
  7. Guest

    > > With a standard BT badged phone on an "analogue" line I typicall see
    > > an echo return loss of about -25dB.

    >
    > Sure, but my point is that that's caused by imperfect termination
    > of the analogue line, and not by acoustic feedthrough from earpiece
    > to microphone.
    >
    > Dave


    That will depend a lot on the particular phone and line, but my
    experience has been that the echo is often a mixture of mismatch
    reflection and acoustic coupling. It is certainly interesting to
    experiment with the source impedance settings on voip - analogue
    adapters. An incorrect setting here can easily dominate any acoustic
    echo.

    I still wonder why VOIP suppliers seem so keen on echo cancellation,
    when the end points are normally VOIP phones or computers which do the
    echo cancellation themselves. Why spend money on a process which is
    probably not necessary and which if overdone can degrade the signal?

    John
    , Jul 27, 2008
    #7
  8. alexd Guest

    Re: Does anyone offer VOIP (SIP or IAX) dial-in numbers WITHOUTechocancellation

    On Sun, 27 Jul 2008 08:49:27 -0700, jrwalliker wrote:

    > I still wonder why VOIP suppliers seem so keen on echo cancellation,
    > when the end points are normally VOIP phones or computers which do the
    > echo cancellation themselves. Why spend money on a process which is
    > probably not necessary and which if overdone can degrade the signal?


    Perhaps the cost of implementing it across the board is less than the
    cost of fielding support queries from people who do have echo problems.
    Perhaps all the ITSPs you've tested use voice platforms that don't allow
    echo cancellation settings to be set per-extension.

    --
    <http://ale.cx/> (AIM:troffasky) ()
    19:42:25 up 15 days, 22:18, 3 users, load average: 0.08, 0.06, 0.01
    Convergence, n: The act of using separate DSL circuits for voice and data
    alexd, Jul 27, 2008
    #8
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