mirror of
https://github.com/cookiengineer/audacity
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56 lines
1.7 KiB
Plaintext
56 lines
1.7 KiB
Plaintext
; general order-2 IIR filter.
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; a0 is assumed to be unity.
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; for a1 and a2, our sign convention is opposite to Matlab's.
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(EQBANDVVV-ALG
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(NAME "eqbandvvv")
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(ARGUMENTS ("sound_type" "s1") ("sound_type" "hz"))
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;; ("sound_type" "gain") ("sound_type" "width") )
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(START (MIN s1 hz)) ;; gain width))
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(TERMINATE (MIN s1 hz )) ;; gain width))
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(LOGICAL-STOP (MIN s1 hz)) ;; gain width))
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(SAMPLE-RATE (MAX s1))
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(INTERNAL-SCALING s1)
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(ALWAYS-SCALE hz)
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(STEP-FUNCTION hz gain width)
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(STATE ("double" "scale1" "s1->scale")
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("double" "w1" "0.0")
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("double" "sw" "0.0")
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("double" "cw" "0.0")
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("double" "J" "0.0")
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("double" "g" "0.0")
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("double" "b0" "0.0")
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("double" "b1" "0.0")
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("double" "b2" "0.0")
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("double" "a0" "0.0")
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("double" "a1" "0.0")
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("double" "a2" "0.0"))
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(DEPENDS ("w1" "hz" "PI2 * hz / s1->sr")
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("sw" "hz" "sin(w1)")
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("cw" "hz" "cos(w1)")
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("b1" "hz" "-2.0 * cw")
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("a1" "hz" "-b1")
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;; ("J" "gain" "sqrt(gain)")
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;; ("recompute" "width" "true")
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("recompute" "hz" "true")
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;; ("recompute" "gain" "true")
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)
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;; (JOINT-DEPENDENCY (("width" "hz")
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;;"if (recompute) {"
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;;" recompute = false;"
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;;" g = sw * sinh(log_of_2_over_2 * width * w1 / sw);"
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;;" b0 = 1.0 + g * J;"
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;;" b2 = 1.0 - g * J;"
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;;" a0 = 1.0 + g / J;"
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;;" a2 = g / J - 1.0;"
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;;"}"))
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(FORCE-INTO-REGISTER recompute)
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(STEP-FUNCTION hz) ;; gain width)
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(CONSTANT "w1" "sw" "cw" "J" "g" "b0" "b1" "b2" "b3" "a0" "a1" "a2")
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(INNER-LOOP-LOCALS " double z0;")
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(INNER-LOOP "z0 = s + a1*z1 + a2*z2;
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output = (sample_type) (z0*b0 + z1*b1 + z2*b2);
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z2 = z1; z1 = z0")
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)
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