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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_
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