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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_GAIN_PROCESSOR_H_
#define RESONANCE_AUDIO_DSP_GAIN_PROCESSOR_H_
#include <cmath>
#include <cstddef>
#include <vector>
#include "base/audio_buffer.h"
namespace vraudio {
// Processor class which applies a gain to a vector of samples from an audio
// buffer. A short linear ramp is applied to the gain to reduce audible
// artifacts in the output.
class GainProcessor {
public:
// Default constructor keeps the gain state uninitialized. The first call to
// |ApplyGain| sets the internal gain state.
GainProcessor();
// Constructs |GainProcessor| with some initial gain value.
//
// @param initial_gain Gain value used as starting point for first processing
// period's gain ramping.
explicit GainProcessor(float initial_gain);
// Applies gain supplied to the input samples.
//
// @param target_gain Target gain value.
// @param input Samples to which gain will be applied.
// @param output Samples to which gain has been applied.
// @param accumulate_output True if the processed input should be mixed into
// the output. Otherwise, the output will be replaced by the processed
// input.
void ApplyGain(float target_gain, const AudioBuffer::Channel& input,
AudioBuffer::Channel* output, bool accumulate_output);
// Returns the |current_gain_| value.
//
// @return Current gain applied by the |GainProcessor|.
float GetGain() const;
// Resets the gain processor to a new gain factor.
//
// @param gain Gain value.
void Reset(float gain);
private:
// Latest gain value to be applied to buffer values.
float current_gain_;
// Flag to indiciate if an initial gain has been assigned.
bool is_initialized_;
};
} // namespace vraudio
#endif // RESONANCE_AUDIO_DSP_GAIN_PROCESSOR_H_
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