«

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

In message <9fde148d-db61-4364-8813->
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

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>

On 24 Jul, 22:47, Peter Gradwell <pe...@gradwell.com> 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

On 24 Jul, 20:18, Dave Higton <davehig...@dsl.pipex.com> 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

In message <6115e09e-b958-42e6-9178->
wrote:

> On 24 Jul, 20:18, Dave Higton <davehig...@dsl.pipex.com> 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

> > 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

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