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

[Nic Bellamy]

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

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