[asterisk-users] 1.8.3 - IAX - echo - jitterbuffer

[sean darcy]

On Mon, Mar 7, 2011 at 6:53 PM, Dave Platt <dplatt at radagast.org> wrote:
>> I'm using iaxagent on a Droid X to connect by IAX to 1.8.3 at the
>> office. 1.8.3 has sip phones. The audio is fine on the Droid X side. On
>> the office side, they hear an echo of _their_ speech, not mine.
>>
>> The office uses sip-providers generally without any echo problem.
>>
>> Where do I start to figure this out? How do I narrow it down? Can I
>> figure out if it is an iaxagent problem? Could using jitterbuffer cause
>> this?
>
> One thing you must consider, is that this echo they're hearing
> may be entirely an acoustic one, within (or around) the Droid
> itself.
>
> It's very possible for the microphone in a handset to
> pick up sound being emitted by the handset's speaker.  This
> acoustic feedback can occur within the handset itself (sound
> from the speaker "leaks" through the chassis of the handset and
> reaches the microphone from behind), via mechanical coupling
> through the handset body, or by the mic picking up the sound
> from the outside (after it has come out of the speaker
> into the air).
>
> The best way to determine whether this is the case, is
> probably to shut down the speaker and isolate the mic...
> plug in an earphone which has a separate mic on its cord,
> and see if the callers still report the echo.  If they do,
> it's due to electronic or digital goofs somewhere, but if they
> do not, it's due to acoustic feedback at the handset.
>
> There are (in principle) three ways to reduce or eliminate
> the echo:
>
> -  Damp it out physically - block the acoustic feedback
>   pathways.  In a small USB phone handset I have, I found
>   it necessary to "stuff" the open spaces inside the handset
>   with cotton and foam, to block the back-wave from the speaker
>   before it reached the microphone.
>
> -  Use software which has some sort of VOX (voice-operated
>   switch) detection or squelching... so that when the sound
>   level at the microphone is less than you'd get by speaking
>   into the mic, the handset "cuts off" the mic audio pathway
>   entirely, and sends only silence (or sends nothing at all,
>   although Asterisk doesn't always deal gracefully with this).
>
> -  Use a better handset.
>

I get no acoustic echo from the Droid X when I make a standard cell
call, even at full volume. Nor is the blogosphere full of complaints
about echos on Droid X. It's also physically one of the largest, if
not the largest, cell phone.

This may mean that the call function in android has really good echo cancelling.