From b2e49bc7e84efd1039253b0485c5c46693cccf3e Mon Sep 17 00:00:00 2001
From: Ivan Cohen <ivan.cohen@musicalentropy.com>
Date: Mon, 7 Dec 2020 17:01:38 +0100
Subject: [PATCH] DSP:  Solved an issue with
 FilterDesign::designFIRLowpassHalfBandEquirippleMethod for low amplitudedB
 and normalisationTransitionWidth close to 0.5

---
 modules/juce_dsp/filter_design/juce_FilterDesign.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/modules/juce_dsp/filter_design/juce_FilterDesign.cpp b/modules/juce_dsp/filter_design/juce_FilterDesign.cpp
index f1acc87af4..6ffb31e65a 100644
--- a/modules/juce_dsp/filter_design/juce_FilterDesign.cpp
+++ b/modules/juce_dsp/filter_design/juce_FilterDesign.cpp
@@ -279,9 +279,14 @@ typename FIR::Coefficients<FloatType>::Ptr
     else
     {
         auto w01 = std::sqrt (kp * kp + (1 - kp * kp) * std::pow (std::cos (MathConstants<double>::pi / (2.0 * n + 1.0)), 2.0));
-        auto om01 = std::acos (-w01);
 
-        NN = -2.0 * result->getMagnitudeForFrequency (om01 / MathConstants<double>::twoPi, 1.0);
+        if (std::abs (w01) <= 1.0)
+        {
+            auto om01 = std::acos (-w01);
+            NN = -2.0 * result->getMagnitudeForFrequency (om01 / MathConstants<double>::twoPi, 1.0);
+        }
+        else
+            NN = 2.0 * result->getMagnitudeForFrequency (0.5, 1.0);
     }
 
     for (int i = 0; i < hh.size(); ++i)