Re: [Audacity-nyquist] Removing Echoes

[Chris G. <cgo...@ho...>]

David,

I had been trying to add and remove echoes, but it wasn't working like I
expected.  Adding and removing an echo seems to work for me now, but only on
the simple echo generated with add-echo.ny.  My question is answered, but my
method won't work on real echoes, like Dominic said.

> Chris,
> 
> echo.ny only makes one echo, was that your intent?

Yes.  If there are more echoes it would be simpler, but only for
non-realistic echoes.

> 
> If I apply deecho.ny to that audio (with identical values), it does
> remove the echo, but it also produces several other echos after. Is
> that the problem you're speaking of?

That part is actually ok.  If the audio is cropped to the length of the
original, those won't be there. I just didn't know how to do that.

> 
> How does deecho.ny work if you get echo.ny to generate several
> echoes?

Something like this:

;nyquist plug-in
;version 1
;type process
;name " Add Echo..."
;action "Adding Echo..."
;info "This effect adds an echo."
;control decay "Decay" real "%" 50.0 0.0 100.0
;control delay "Delay" real "seconds" 1.0 0.001 10.0
(defun add-echo (s decay delay n)
    (cond
        ((= n 0) s)
        (t (sum
            (add-echo s decay delay (- n 1))
            (scale (expt (/ decay 100.0) (float n)) (at-abs (* delay n) (cue
s))))))

(add-echo s decay delay 10)

;nyquist plug-in
;version 1
;type process
;name "DeEcho..."
;action "Removing Echo..."
;info "This effect removes an echo."
;control decay "Decay" real "%" 50.0 0.0 100.0
;control delay "Delay" real "seconds" 1.0 0.001 10.0
(diff s (scale (/ decay 100.0) (at-abs delay (cue s))))

> 
> I don't know enough Nyquist/Xlisp yet to understand some of your
> deecho.ny code, nor the math you gave. So I can't help in that
> regard.
> 
> David

Thanks.

Chris