[linux-audio-dev] Latency and feedback problems: soundcard with live microphone pass-thru, optimal solution ?

Hi all,
I would like to route a microphone through a sound card and back to
powerful amplified speakers.

As we know in analog PA gear you have the microphone feedback problem
(usually it comes in form
of high pitched whistle sounds).

But if I route a mic from into the soundcard and out to the speakers,
there will be a small delay
due to the audio card buffers. Even if it's only a few msecs it makes
the problem much worse
than in the case of analogue gear because the feedback sound will come
in chunks that's one audio card buffer at time.
For example if I use 64 samples per buffer which gives me acceptable
latency for a live singer, the feedback noise
could possibly generate a much lower pitched signal/interference (I
assume something like 44100/64 Hz) which is I think
not easy to filter out compared to the high pitched feedback (is in the
latter case sufficient to cut some high frequencies using an EQ ?).

How can one solve the feedback problem in case of mic to speaker delays
of let's say 5-10msecs ?
Is an echo canceller algorithm needed ? If yes does this compromise the
quality of the input signal (the singer).

I think this is a very interesting topic and it would be cool if
knowledgable people could come up with topics and ideas.
(for example people that are good at DSP, room correction etc, like Fons
A. etc).

PS: I know that cards like DELTA 1010 and others (RME) can do zero
latency monitoring (hardware pass-thru) but
I'd prefer a software based routing since you can apply effects and
stuff before forwarding the output.

thanks for infos and toughts
Benno

http://www.linuxsampler.org
Received on Fri Oct 28 16:15:07 2005