Yes, as I said in the mail, not only the the time of the delay is very
very short that it would be very difficult for me to find "at hand",
also, as you say, this time would be variable. My system don't work... I
knew it.
I took a look to some pages (*), but I only understand... the title of
the mails and the PDF filename. The texts are chinese for me. I didn't
know that echo cancellation is, as Peter Parker said, "quite a
substantial topic"... and it is out of my hands to try different EC
systems. No time, no knowledge, no time... no time.
Also, there's http://grh.mur.at/software/adaptive.html... but I don't
know how to test it.
I made a diagram of my system... if anyone knows which echo cancellation
system would work for me... I would reallly appreciate it.
Thank you.
(*)
http://comments.gmane.org/gmane.comp.multimedia.puredata.general/63658
https://ccrma.stanford.edu/~eberdahl/Projects/FeedbackCancellation/FeedbackCancellation.pdf
Peter Parker sent me this link, but I have to pay to see it:
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1146062.
El 04/05/15 a las 13:48, Spencer Russell escibió:
You're not likely to get very good results with just a single delay. The
way these systems normally work (e.g. on phones and conferencing
systems) is to continuously estimate the transfer function between the
speaker and the microphone (impulse response in the time domain). Then
you take the received signal, convolve it with the inverse of the
impulse response, and mix it into the signal you receive from the
microphone.
The diagram at the bottom of this page[1] is a pretty good one to
understand what's going on.
-s
http://www.speex.org/docs/manual/speex-manual/node4.html
On Mon, May 4, 2015, at 10:18 AM, Mario Mey wrote:
Hi, there. 2 years ago, I created this thread on the forum:
http://forum.pdpatchrepo.info/topic/7340/echo-supressor. After
talking about dBs, I thought I acchived what I was looking for. But
no. Nor close.
My last non-replied post on september 2014 says:
/Bringing back to life an old thread... I tried to make this patch
work LIVE... and it is not as thought./
/To make this patch work (*1), I should find the perfect delay to
suppress the audio. Using 44100, the delay time can vary in 0.0226ms.
So... it's almost impossible to get that. I only acchieve a flanger,
nothing else./
/In the first Patch-Circle done in Argentina last Saturday, I talked
with Pablo E. Riera about this and he told me about the adaptive
external and the echo cancellation example... but there is no example
like that (only intereference cancellation)./
/I will explain again (*2): the operator has a microphone (using one
channel of input) and it sounds in a LCD (far away) (using one
channel of output). Above the LCD I have a mic (second channel of
input). This mic takes what the audience says and send to the
operator headphones (second channel of output). The operator hears
her own voice (with a delay). I want to supress this "return". It
doesn't matter the latency, I just don't want the operator to hear
her/him voice./
/I would need something that learn from the first microphone and get
rid of what the second mic takes./
/I hope being clear in my explanation. Thanks in advace./
(*1): the patch is in the thread. It does something like this: it
takes the microphone (channel one), invert the wave (by using [*~
-1]), it uses a delayline to synch (because of the latency) and mix
with the output. The intention is, obviously, suppress the microphone
after been listened by the second microphone.
[adc~]
| \
| [delwrite~ echo-supressor-A 1000]
|
[delwrite~ echo-supressor-B 1000]
[Hslider] # to synch. It depends on latency (it would have to be
exact, here is the problem!)
|
[vd~ echo_supressor-A]
|
[*~ -1]
|
| [vd~ echo_supressor-B 1]
| /
[+~]
|
[dac~]
(*2): I just updated the explanation
How can I acchieve an echo suppresor? Is this possible?
If I'm not clear in my explanation, please tell me. Thanks.
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