From 6c09b268d860f5cf13e79a3d9db6b0be00f7af40 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Fri, 8 Feb 2019 12:22:08 +1100
Subject: [PATCH] Filter: fixed crash on zero cutoff frequency

this fixes #10435
---
 libraries/Filter/LowPassFilter2p.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/libraries/Filter/LowPassFilter2p.cpp b/libraries/Filter/LowPassFilter2p.cpp
index f823829a2e..653c3a4a62 100644
--- a/libraries/Filter/LowPassFilter2p.cpp
+++ b/libraries/Filter/LowPassFilter2p.cpp
@@ -35,6 +35,10 @@ template <class T>
 void DigitalBiquadFilter<T>::compute_params(float sample_freq, float cutoff_freq, biquad_params &ret) {
     ret.cutoff_freq = cutoff_freq;
     ret.sample_freq = sample_freq;
+    if (!is_positive(ret.cutoff_freq)) {
+        // zero cutoff means pass-thru
+        return;
+    }
 
     float fr = sample_freq/cutoff_freq;
     float ohm = tanf(M_PI/fr);
@@ -83,6 +87,10 @@ float LowPassFilter2p<T>::get_sample_freq(void) const {
 
 template <class T>
 T LowPassFilter2p<T>::apply(const T &sample) {
+    if (!is_positive(_params.cutoff_freq)) {
+        // zero cutoff means pass-thru
+        return sample;
+    }
     return _filter.apply(sample, _params);
 }