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

Wed Feb 14 16:14:36 MST 2007

That is why people use FPGA's.

Google FPGA vs ASIC vs CPU if you want to educate yourself.

-----Original Message-----
From: Nic Bellamy [mailto:nicb-lists at vadacom.co.nz] 
Sent: Wednesday, February 14, 2007 1:53 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] The High Performance Echo Canceller (HPEC)

shadowym wrote: 

	I gotta take issue with your comments that a HWEC is just software
running
	on a DSP.  In the case of Octasic, it's an ASIC.  How it does EC is
VERY
	different because.....it's done completely in hardware, not firmware
loaded
	into memory and run on a specialized CPU!  Yes, the ASIC does
contain an DSP
	but it is customized for EC.  You cannot think of it as a CPU. 

You've obviously missed the fact that the Octasic chips have loadable
firmware.

Without being privy to any internal Octasic information, all I can guess is
that their ASIC is a customised DSP core with perhaps more on-chip fast
memory for FIR coefficient storage, and perhaps custom instructions/custom
logic blocks specifically designed to improve the performance for the type
of mathematical operations required for echo cancellation.

Nobody in their right mind is going to do this entirely in custom circuitry
- if you find a bug in your algorithm, or a way to improve things, what then
- spend a few million on getting your chip rebatched and tell your users get
their soldering irons out?

Anyway, I'm going to shut up now before I get carried away and start a flame
war :-)

Cheers,
    Nic.

	-----Original Message-----
	From: Nic Bellamy [mailto:nicb-lists at vadacom.co.nz] 
	Sent: Tuesday, February 13, 2007 5:43 PM
	To: Asterisk Users Mailing List - Non-Commercial Discussion
	Subject: Re: [asterisk-users] The High Performance Echo Canceller
(HPEC)

	shadowym wrote:

		Interesting,

		Is this just a more advanced software echo canceller or
software with 
		hardware hooks or software with hardware assisted
processing?

	A more advanced software canceller (there's no magical thing that
makes
	"hardware" echo cancellers better, it's still software, but it's
running on
	a DSP so it has more grunt available to it).

	It's licensed from Adaptive Digital Technologies - G.168 compliant,
and
	supports up to 1024 taps (128ms) of tail coverage. Comes as a binary
blob,
	but such is life.

		How would it compare to a true hardware echo canceller like
the one 
		Sangoma uses.  Besides the extra CPU cycles required.

	Quite comparable - not sure if Octasic (as used by Sangoma and the
latest
	Digium cards) or ADT would win in a shootout, but they're both in
the same
	quality class.

	The main issue is going to be CPU usage - getting this going at 1024
taps on
	a full T1/E1 span would likely require two fast CPUs with the
interrupts
	distributed evenly between them... and even then, *shrug*

	Cheers,
	    Nic.

		-----Original Message-----
		From: Nic Bellamy [mailto:nicb-lists at vadacom.co.nz]
		Sent: Tuesday, February 13, 2007 12:41 PM
		To: Asterisk Users Mailing List - Non-Commercial Discussion
		Subject: Re: [asterisk-users] The High Performance Echo
Canceller 
		(HPEC)

		Larry Shields wrote:

			I recently read about the following new technologies
from Digium.  
			Has anyone tried the new HPEC or knows when it will
be available?

		It's out now, and I've tried it - the difference between
HPEC and MG2 
		from trunk is stunning - in situations with bad echo where
MG2 can 
		take ten or more seconds to converge to a reasonable degree,
HPEC does 
		it in perhaps 300ms - converging on my intake of breath
before I say 
		"hello", and absolutely no echo after that unless I
purposefully go 
		out of my way to screw it up (whistling/blowing into the
handpiece for 
		instance - even then, the malfunction is minimal).

		You can now buy it from the Digium website (US$10 per
channel), or if 
		you have an in-warranty Digium card, email through the
serial numbers 
		to Digium support and they'll give you a key (this is what I
did).

		You'll need Zaptel 1.2.13 to make it go.

		It does take quite a bit of CPU though - perhaps 70% more
compared to 
		MG2-trunk for the same number of taps from my rough
measurements.

		Cheers,
		    Nic.

		--
		Nic Bellamy,
		Head Of Engineering, Vadacom Ltd - http://www.vadacom.co.nz/

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	Nic Bellamy,
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Nic Bellamy,
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