[asterisk-users] The High Performance Echo Canceller (HPEC)

[shadowym]

Of course it is all digital.  It can also do the entire process in one clock
cycle I would imagine.  A CPU, I don't know.  Maybe 100's of thousands.  For
a real time environment that is an important distinction. 

What I am debating is the people who are saying ASIC's and CPU's are the
same thing.  Hardly!

-----Original Message-----
From: Matthew Fredrickson [mailto:creslin at digium.com] 
Sent: Wednesday, February 14, 2007 2:18 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] The High Performance Echo Canceller (HPEC)


On Feb 14, 2007, at 3:12 PM, shadowym wrote:

> The algorithms may be similar but EC is an infinitely variable
> non-linear(analog) process.  A CPU cannot do that.  You can fake it by 
> performing cpu intensive rapid calculations one after another but it 
> is fundamentally not an analog processor.  HWEC is designed to deal 
> with the analog process on an instant by instant basis performing 
> parallel computations.  A CPU cannot do that at ANY clock speed.

I don't think you are seeing this clearly.  The octasic is a processor. 
  It has firmware that loads.  Though it maybe a specialized processor with
instructions that help with echo cancellation, by the time that a HW echo
canceller sees the data it is very much not analog anymore.  It has already
gone through an analog to digital converter and the algorithms and math that
are used to cancel echo are done in the digital domain.  Modern echo
cancellation is not done in continuous time, it is done in the digital,
discrete time.  That means sampled, and coming in through a TDM bus of some
sort.  Not analog.

Matthew Fredrickson