iChat's echo cancellation (was Re: Output Capture)
iChat's echo cancellation (was Re: Output Capture)
- Subject: iChat's echo cancellation (was Re: Output Capture)
- From: Andrew Kimpton <email@hidden>
- Date: Wed, 18 Jul 2007 19:21:15 -0400
iChat works entirely with public APIs and their own echo cancellation
code. No private APIs are used.
You speak as if we have access to the iChat code, so it's not a given
at all that just because iChat can do something, so can we.
Why would you need access to the iChat code? Echo Cancellation is a
major research area in signal processing. It is written about in
numerous text books and papers every year. I'm sure you can dig up
something useful with even a casual Google search.
If it's the case that iChat only uses public APIs, how about some of
that code gets pasted into a new Sample Code project and put on ADC?
That would seem to make the most sense since people like us
repeatedly are looking for a cold, hard solution. And if you don't
won't to do that, could you help us understand why not? If the
reason is that it would be unsupported code, then we'd say back that
we understand and acknowledge that and we assume the consequences of
that.
Since we don't provide an Echo Cancellation library, obviously there
won't be any sample code for that. But that aside, there is all sorts
of sample code for all the APIs that iChat uses out of Core Audio.
Some folk here seem (from my reading of the messages) to want access to
the audio emitted by the computer itself in order to eliminate it from
captured audio as part of an echo cancellation process ? They seem to be
strengthening the argument by suggesting that iChat does the same thing ?
But does it ? Perhaps iChat's audio enhancement and echo cancellation
doesn't use the computers own current output at all ? But relies on
other approaches ? If I recall correctly the iSight for example employs
two microphones with beam shaping to enhance the quality of the sound
on the basis that the persona talking is in front of the camera. Similar
knowledge of the physical layout of two microphones in a notebook
(assuming true stereo input) could also be used to achieve a similar effect.
Andrew 8-)
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