[Sumover-dev] Re: an AccessGrid question from Leon...

[Andrew Ford]

Hi,

Yes, software echo cancellation would be incredibly useful! As far as I
know, most hardware echo cancelling solutions (beyond things like personal
tabletop mics like the Chat50) end up being US$2000+, which might not be a
problem for some big-budget institutions, but tends to be an issue for us :)
It may also make things like AG more accessible to people at home due to not
having to buy extra audio equipment, bridge/network issues notwithstanding.

Polycom PVX, the drivers for Logitech webcams that have built-in mics, and
Skype I think, all do software echo cancellation themselves, and I've heard
of a Max/MSP implementation as well (but haven't been able to find much info
on it), so it definitely seems possible.

In fact, I've been toying around with the idea of developing an entire
replacement for RAT (no offense Piers/other UCL devs :) since I think there
are a lot of issues and room for improvement: the Mac audio code needs to be
rewritten to use the new API, it has no way of using multiple audio devices,
even just 2 for separate input/output, it has no way of sending multiple
streams, it doesn't support any kind of routing to external programs (ie
JACK - could be very useful for compression, limiting, EQ), it tends to
crash often (on Windows at least) due to Mbus (side note: are there any
other nice ways for it to communicate with vic or other video apps?), and
the interface should probably be redesigned. Software AEC and JACK-esque
routing to external programs could make things like the XAP, Converge, etc.
entirely unnecessary.

Let me know if there's any opportunity for any project like this - I do have
experience with audio, and I'd love to be able to work on it. I'd start it
up right now if I weren't somewhat busy with video stuff :)

--Andrew

2009/5/29 leon zadorin <leonleon77 at gmail.com>

> Hello AccessGrid developers and visionaries :-)
>
> I have a quick question to ask...
>
> I was thinking of the nature of some R&D projects that I could propose
> to various organisations/universities/etc for undertaking et al and
> recalled the issue of audio 'echo-cancellation' when it comes to
> network-distributed, collaborative meetings.
>
> I am not sure of the current status of 'echo-canceling' solutions but,
> if my memory serves me right, there were numerous attempts to create
> an open-source, software-based solution for 'echo-cancellation' --
> with the majority of such attempts having come short of being
> comparable to hardware-based, proprietary products (in terms of
> quality, dynamic self-tuning etc).
>
> Presuming the above still holds and applying one's 'lateral thinking',
> I was wondering: if I was able to make such a self-tuning,
> dynamically-updating solution (both in software and deployable on
> regular computers -- without the need for any special graphics cards
> for extra processing power) -- how exactly useful or valuable would
> this solution be? I mean -- is there any use for it nowdays at all?
>
> I am asking because I remembered that during my days of
> forensic-analysis work there was a device which was doing a very
> similar thing (in fact such concepts are not new to the digital signal
> processing theory by a long shot and have been in public debate/view
> for quite some time now) and I think know how to make one (i.e. how to
> implement this theory in real-time on a modern computer) -- so there
> is a reasonable degree of expectation for the solution to work (i.e.
> self-tuning -adjusting software-based solution to cancel echoes in
> real-time network collaborations)... to this extent, I suppose, the
> whole uncertainty of "R" in "R&D" is somewhat reduced (albeit not
> completely eliminated).
>
> Anyway -- no point in considering anything unless it is actually
> needed :-) :-) :-)
>
> Kind regards
> Leon Zadorin.
>
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