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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: Sridhar Nag on December 09, 2012, 09:13:13 AM

Title: Audio Application for windows7 for echo cancelling in real time
Post by: Sridhar Nag on December 09, 2012, 09:13:13 AM
Hi all.

I am looking for an software that can cancel echo in real time. I want to use my laptop in place of a feedback destroyer. Can you people pls suggest me a software that can take live sound form a mic as an input and then do feed back and echo cancellation , equalize the sound and then give sound output in real time....

Pls i am in need of it.. Thanks in advance..  :)
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Ivan Beaver on December 09, 2012, 09:17:33 AM
Hi all.

I am looking for an software that can cancel echo in real time. I want to use my laptop in place of a feedback destroyer. Can you people pls suggest me a software that can take live sound form a mic as an input and then do feed back and echo cancellation , equalize the sound and then give sound output in real time....

Pls i am in need of it.. Thanks in advance..  :)
You HAVE to use your full real name on these forums or the thread will get locked.

Echo cancellation is not exactly what you think it might be. It is used in telecommunications and works well, but in a live situation I am not aware of anything (software based or hardware) that can do that-but I could be wrong.

And then you have the whole "what type of mic pre and quality" and how the get the computer inserted into the chain and so forth issue.
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Mark McFarlane on December 10, 2012, 11:05:10 PM
Hi all.

I am looking for an software that can cancel echo in real time. I want to use my laptop in place of a feedback destroyer. ...

Echo and feedback are two very different things.

The apparent echo will change at every single location in a room because it is dependent on the physical distance of the listener to every 'obstruction' that is a reflective surface.  Move 2 inches and the echo you hear is different.

That being said, one could reduce the echo for one listening location by recording/sampling the impulse response of the room at that location (e.g. a balloon pop), inverting the impulse response, and then apply it using a convolution-based reverb.  Although theoretically the result is only valid at one location in the room (where the impulse response was recorded), it may sound reasonable in the neighborhood of the impulse response measurement. Edit: This is really only going to work if there is only a single speaker in the room and you pop the ballon at the speaker location and record at the listeners location.

There are some other techniques one might employ that don't use the impulse response, e.g. using the autocorrelation of the soundfield (in real time) which has the frequency domain signature of the echos embedded.

I've always wanted to try this in live sound to see what happens.  My suspicion is that the high frequencies would be trashed due to noise in the measurement.
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Brad Weber on December 11, 2012, 06:31:52 AM
Hi all.

I am looking for an software that can cancel echo in real time. I want to use my laptop in place of a feedback destroyer. Can you people pls suggest me a software that can take live sound form a mic as an input and then do feed back and echo cancellation , equalize the sound and then give sound output in real time....

Pls i am in need of it.. Thanks in advance..  :)
I believe the simple answer is that there is no such thing that would be effective for large scale live sound reinforcement.
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Tim Halligan on December 11, 2012, 07:14:56 AM
There is also the issue of "real time".

Even if such a thing does exist, the latency involved in the process - not to mention any AD/DA conversions to get in and out of the computer - may make the process unworkable for live use.

Cheers,
Tim
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Mark McFarlane on December 11, 2012, 10:44:23 AM
There is also the issue of "real time".

Even if such a thing does exist, the latency involved in the process - not to mention any AD/DA conversions to get in and out of the computer - may make the process unworkable for live use.

Cheers,
Tim

Since the boundaries are stationary (which really simplifies the problem), if the signal going to the speaker goes through the same AD/DA conversion I don't think latency would be an issue, again with a single speaker on stage.  If you dynamically determined the achos using an autocorrelation approach it would take a few seconds for the algorithm to hone in, but then there is no need to buffer the data very much, you can do the math as the signal flows through.  If the room and speaker layout are symmetrical you might even be able to pull off a typical speaker system tuned for the center of the house.

It would be a fun experiment none the less, and I have some rough ideas about bandlimiting the inverse filter that might help minimize trashing the high frequencies.  If I wasn't so lazy I could build a model to determine how well it would work.  I'm sure ther are a few problems I haven't thought through. 

For those interested you can Google Predictive/Adaptive/Spiking deconvolution to see some of the math.  I've been using this technique in another field for a little over 3 decades, but on band limited data (5-80Hz) and the 'reflectors' change in space/time which makes it a more difficult problem.

A co-worker of mine (the founder of my previous company) invented Autotune, everyone thought he was crazy too.
Title: Audio Application for windows7 for echo cancelling in real time
Post by: Samuel Rees on December 11, 2012, 12:01:46 PM
Doesn't it seem like the OP really meant feedback? :) It just seems more plausible! Though this is fascinating stuff...
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: g'bye, Dick Rees on December 11, 2012, 12:42:12 PM
Hi all.

I am looking for an software that can cancel echo in real time. I want to use my laptop in place of a feedback destroyer. Can you people pls suggest me a software that can take live sound form a mic as an input and then do feed back and echo cancellation , equalize the sound and then give sound output in real time....

Pls i am in need of it.. Thanks in advance..  :)

I use a pair of corporeal audio transducers in conjunction with a cerebro-corteal processor to accomplish such tasks.
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Mark McFarlane on December 11, 2012, 02:57:25 PM
I use a pair of corporeal audio transducers in conjunction with a cerebro-corteal processor to accomplish such tasks.

I can see how that would help with the echos, but what about the feedback? You need to add dual manual digit insertions into the corporeal audio transducers.
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: g'bye, Dick Rees on December 11, 2012, 03:00:09 PM
I can see how that would help with the echos, but what about the feedback? You need to add dual manual digit insertions into the corporeal audio transducers.

Balanced or unbalanced inserts?
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Ivan Beaver on December 11, 2012, 06:41:53 PM
Balanced or unbalanced inserts?
I like the inverted upwards down converters myself.
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Mark McFarlane on December 11, 2012, 10:18:30 PM
I figured someone, somewhere had already tried to write the code, and alas http://www.zynaptiq.com/unveil/overview/ (http://www.zynaptiq.com/unveil/overview/). 4096 samples of latency.  Proposed use is in post, not live.  Free demo.  Target is early reflections only, not 'distinct echos'.
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: Chris Hindle on December 12, 2012, 08:19:05 AM
Balanced or unbalanced inserts?
Balanced of course (one on each side).
Title: Re: Audio Application for windows7 for echo cancelling in real time
Post by: g'bye, Dick Rees on December 12, 2012, 08:47:02 AM
I figured someone, somewhere had already tried to write the code, and alas http://www.zynaptiq.com/unveil/overview/ (http://www.zynaptiq.com/unveil/overview/). 4096 samples of latency.  Proposed use is in post, not live.  Free demo.  Target is early reflections only, not 'distinct echos'.

That's an interesting piece of software.  It looks like it's targeted at film and recording production.  I played with the sample a bit and while it works as advertised, it only allows you to hear and compare results in "real time".  There is still enough processing latency to disqualify if from live use.

And as you twist the virtual knobs to adjust the amount of processing, you inevitably come to the point at which the processing "degrades" the signal to an unacceptable degree.  So it's then "back of the knob and continue".