For Asterisk users who connect to
the PSTN, the most common type of echo is hybrid echo - the echo
introduced by the impedance mismatch between 2-wire and 4-wire telephone
The echo manifests as a distorted
and delayed reflection of the users voice while in conversation with an
external party through the PSTN. Asterisk itself offers a range of
software-based open source echo cancellation routines that are
moderately effective in eliminating the hybrid mismatch echo that most
Asterisk users experience.
However, there are cases in which
these algorithms are not effective. To combat this, Digium introduced
DSP-based echo cancellation modules for our multi-port T1/E1/J1 cards
and our 24-port analog card.
Now, Digium is pleased to make
available the VPMOCT032 echo cancellation module.
This module, which offers 128ms
(1024 taps) of echo cancellation across all of its channels and provides
the same toll-quality G.168 compliant echo cancellation found in
Digium's HPEC software-based commercial echo canceller.
The VPMOCT032 is immune from any
system CPU spikes that might otherwise affect a software-based solution.