[AG-TECH] interesting slashdot .. software echo cancellation
mngay at purdue.edu
Thu May 9 08:21:42 CDT 2002
The Gentners, ASPIs and others are expensive because they are
small/niche market items. I do beleive this will go down as the
technology becomes less expensive and development costs are
Software echo cancellation is really an interesting term because it
actually is all software! The difference is the platform the code runs
on, either an embedded DSP processor or a PC platform. The
embedded device or "appliance" device uses a DSP chip, which is
simply a microprocessor optimized for the implimentation of DSP
algorithms. Typically these use what is know as Harvard
Architecture which can perform multiple operations during one
clock cycle. Pentiums are based on the Von Neuman
architecture. This architecture is not optimized for performing real
time digital signal processing, but accomplishes the task using
brute force (lots of horsepower and CPU cycles).
This is comparable to how a sleek sprots car with a 6 cylinder
engine could outrun a tractor-trailer semi rig with a much larger and
more powerful engine. The semi must pull a lot more to go the
same distance but can haul a variety of things while the sports car
was built for speed and hauling only one thing...from which I shall
refrain from typing on a public list.
For beginners in DSP, I have written a paper which you can access
It was written with broadcast engineers in mind and speaks mostly
of audio compression rather than echo cancellation, but a lot of the
basic premises are the same. I also focus more on embedded
"appliance" DSP because I am an embedded programmer more-so
than a PC programmer. Any DSP veterans out there are welsome
to correct any gross innacuracies which might have eluded me.
Also, for those who want to see the rest fo the site, pardon the fact
that the web site has not been updated in some time. Real work
always seems to get in the way.
Now that I have bored you all to tears, back to PC echo
For small venues, I see no reason why some smart PC
programmer out there in the AG community could not write a
multichannel echo canceller and take advantage of the six audio
channels used as standard input for the AG audio encoder. This
would allow five to six echo cancelled channels without the use of
an outboard canceller. Not practical for a large room system but
such a method could be more inline with a small venue budget.
On 8 May 2002, at 15:19, Jay Beavers wrote:
> Actually, software echo cancellation, automatic gain control, and noise
> reduction is already in Windows XP and used in the Windows Messenger
> conferencing app.
> However, once you enter AG-like scenarios with multiple microphones,
> large spaces, and audio processing you're in a specialized, small market
> that is well served by Gentner et al.
> - jcb
> -----Original Message-----
> Is anyone working on such a thing? The gentners are expensive pieces of
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