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diff --git a/src/3rdparty/resonance-audio/resonance_audio/dsp/mono_pole_filter.h b/src/3rdparty/resonance-audio/resonance_audio/dsp/mono_pole_filter.h
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+++ b/src/3rdparty/resonance-audio/resonance_audio/dsp/mono_pole_filter.h
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+/*
+Copyright 2018 Google Inc. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS-IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#ifndef RESONANCE_AUDIO_DSP_MONO_POLE_FILTER_H_
+#define RESONANCE_AUDIO_DSP_MONO_POLE_FILTER_H_
+
+#include "base/audio_buffer.h"
+
+namespace vraudio {
+
+// Class representing a mono pole filter. This class also performs filtering.
+class MonoPoleFilter {
+ public:
+  // Constructs a |MonoPoleFilter| given a single coefficient.
+  //
+  // @param coefficient A single coefficient between 0.0f and 1.0f.
+  explicit MonoPoleFilter(float coefficient);
+
+  // Filter method for use with AudioBuffer::Channel.
+  //
+  // @param input |AudioBuffer::Channel| of input to be processed.
+  // @param output Pointer to output |AudioBuffer::Channel|.
+  // @return Returns false if the filter has an allpass configuration. This
+  //     helps to avoid copies whenever the output is expected to be identical
+  //     to the input.
+  bool Filter(const AudioBuffer::Channel& input, AudioBuffer::Channel* output);
+
+  // Sets the filter's coefficent.
+  //
+  // @param coefficient A mono pole filter coefficient.
+  void SetCoefficient(float coefficient);
+
+ private:
+  // The previous frame computed by the filter.
+  float previous_output_;
+
+  // Represents and maintains the state of the filter in terms of its
+  // transfer function coefficient.
+  float coefficient_;
+};
+
+}  // namespace vraudio
+
+#endif  // RESONANCE_AUDIO_DSP_MONO_POLE_FILTER_H_