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

[fons adriaensen]

On Sat, Oct 29, 2005 at 05:16:53PM +0200, Jens M Andreasen wrote:

> Suggestion: Invert the phase of the offending microphone. This should
> kill dead feadback in the frequency-band currently annoying you. The
> downside is that it will also emphasize other frequency-bands that did
> not pose a problem before. The theory is that those resonanses will be
> minor relative to your current major problem.

(Somehow I missed Benno's original post)

Good suggestion.

>  Benno Senoner wrote:
> 
> > 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 ?).

There should be no difference: the processing delay has just the same
effect as any delay, for example the one introduced by speaker to mic
distance. It's in a different place in the loop, but loops being what
they are, that doesn't matter.

One thing I learned is that effect processors can make the situation
much worse. So if your problem is with the monitor mix as Jens assumed,
I'd suggest to leave out the effects there. And in that case you could
equally well use zero delay monitoring either from you card or directly
from the mixing desk.

-- 
FA