[asterisk-users] Maybe a little OT---USB Handset

[Rob Hillis]

I doubt that chan_oss/chan_alsa directly support echo cancelling. 
However depending on exactly how you are using the inputs and outputs on
a sound card, you could very well need echo cancellation.

90% of the time, echo is generated at the junction between a channel
that separates received and transmitted audio and one that receives and
transmits on the same physical channel - an analogue line is the usual
culprit.  If your link to the PSTN is via an E1/T1 channel, chances are
good that you'll still have an analogue line at the end of your call so
the echo moves beyond your direct control.  That's the normal scenario
for requiring echo cancellation.

The remaining 10% of the time, echo is generated by sound "leaking" from
a speak to a microphone on a handset or by some other means.  This is
where echo cancellation /may/ be required for a chan_oss/chan_alsa
channel.  If your headset mic is too sensitive and the volume on the
headset speakers is a little too loud, all of a sudden you've got echo.


Tzafrir Cohen wrote:
> Do any of the above support cancelling acustic echo? Is it actually
> needed in this case?
>
>   
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