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Fix for bug 1026

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This commit is contained in:
Steve Daulton
2015-06-19 14:15:59 +01:00
parent 218172d12a
commit 07ca677dc7
2 changed files with 25 additions and 12 deletions
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15
nyquist/dspprims.lsp
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@@ -306,13 +306,20 @@
; remember that snd-biquad uses the opposite sign convention for a_i's
; than Matlab does.
; convenient biquad: normalize a0, and use zero initial conditions.
; convenient biquad: normalize a0, and use zero initial conditions.
(defun nyq:biquad (x b0 b1 b2 a0 a1 a2)
(if (< a0 1.0)
(error (format t "a0 < 1 (unstable parameter) in biquad~%")))
(if (<= a0 0.0)
(error (format nil "a0 < 0 (unstable parameter a0 = ~A) in biquad~%" a0)))
(let ((a0r (/ 1.0 a0)))
(snd-biquad x (* a0r b0) (* a0r b1) (* a0r b2)
(* a0r a1) (* a0r a2) 0 0)))
(setf a1 (* a0r a1)
a2 (* a0r a2))
(if (or (<= a2 -1.0) (<= (- 1.0 a2) (abs a1)))
(error (format nil
"(a2 <= -1) or (1 - a2 <= |a1|) (~A a1 = ~A, a2 = ~A) in biquad~%"
"unstable parameters" a1 a2)))
(snd-biquad x (* a0r b0) (* a0r b1) (* a0r b2)
a1 a2 0 0)))
(defun biquad (x b0 b1 b2 a0 a1 a2)