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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_MULTI_CHANNEL_IIR_H_
#define RESONANCE_AUDIO_DSP_MULTI_CHANNEL_IIR_H_
#include <memory>
#include <vector>
#include "base/audio_buffer.h"
namespace vraudio {
// Class that performs IIR filtering on interleaved data. This class can be used
// to implement any order of IIR filter on multichannel data where the number of
// channels is a multiple of the SIMD vector length.
class MultiChannelIir {
public:
// Returns a |MultiChannelIir| given valid parameters.
//
// @param num_channels Number of channels in each input buffer. The number of
// channels must be divisible by |SIMD_LENGTH|.
// @param frames_per_buffer Number of frames in each input buffer.
// @param numerators Numerator coefficients, one set per channel.
// @param denominators Denominator coefficients, should be equal in length to
// the |numerator| vector, one set per channel.
// @return A |MultiChannelIir| instance.
static std::unique_ptr<MultiChannelIir> Create(
size_t num_channels, size_t frames_per_buffer,
const std::vector<std::vector<float>>& numerators,
const std::vector<std::vector<float>>& denominators);
// Processes an interleaved buffer of input data with the given IIR filter.
//
// @param interleaved_buffer A single channel of data containing input in
// interleaved format, this will contain output data in interleaved format
// on return.
void Process(AudioBuffer::Channel* interleaved_buffer);
private:
// Constructs a |MultiChannelIir|.
//
// @param num_channels Number of channels in each input buffer. The number of
// channels must be divisible by |SIMD_LENGTH|.
// @param frames_per_buffer Number of frames in each input buffer.
// @param num_coefficients Number of coefficients in the numerator, which
// equals the number in the denominator.
MultiChannelIir(size_t num_channels, size_t frames_per_buffer,
size_t num_coefficients);
// Number of channels in each input buffer.
const size_t num_channels_;
// Number of frames in each input buffer.
const size_t frames_per_buffer_;
// Number of coefficients in the numerator and denominator polynomials.
const size_t num_coefficients_;
// Current front of the delay line which is circularly indexed.
size_t delay_line_front_;
// Stores numerator coefficients in repeated fashion.
AudioBuffer numerator_;
// Stores denominator coefficients in repeated fashion.
AudioBuffer denominator_;
// Holds previous data computed from the numerator section.
AudioBuffer delay_line_;
};
} // namespace vraudio
#endif // RESONANCE_AUDIO_DSP_MULTI_CHANNEL_IIR_H_
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