Re: iChat's echo cancellation (was Re: Output Capture)
Re: iChat's echo cancellation (was Re: Output Capture)
- Subject: Re: iChat's echo cancellation (was Re: Output Capture)
- From: email@hidden
- Date: Thu, 19 Jul 2007 10:06:36 -0600
On Jul 19, 2007, at 9:50 AM, Matthew Xavier Mora wrote:
At 7:21 PM -0400 7/18/07, Andrew Kimpton wrote:
rary, 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 ?
I'm assuming iChat's algorithm does not cancel out all audio coming
out of the computer, only the audio it receives from the other end.
(the computer could be playing music via itunes and the other end
may want to hear that) Since it is highly likely that the audio
coming in from the network will be played out the speakers and thus
reappear on the input signal, you can make the assumption that they
would keep that audio around as a hint of what will likely need to
be canceled a few milliseconds from now. What they do need is a
good latency estimator, then they can estimate how long to wait
before the audio they just played is likely to come back in again.
Hmmm that's an interesting point, I hadn't thought of that. In my
case, I don't want the game's music to come through, or speech from
other people on the web, but maybe I do want people to be able to
play music to show their friends, including from itunes. So it just
comes down to eliminating the audio from my app. I was hoping for an
easy way to just grab that audio, but it sounds like I should use a
graph to mix instead. Anyway, thanx for the idea, I think it made my
whole day.
--Zack
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