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220 lines
7.9 KiB
C++
220 lines
7.9 KiB
C++
//
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// FilteringSpeaker.h
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// Clock Signal
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//
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// Created by Thomas Harte on 15/12/2017.
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// Copyright © 2017 Thomas Harte. All rights reserved.
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//
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#ifndef FilteringSpeaker_h
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#define FilteringSpeaker_h
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#include "../Speaker.hpp"
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#include "../../../SignalProcessing/Stepper.hpp"
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#include "../../../SignalProcessing/FIRFilter.hpp"
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#include "../../../ClockReceiver/ClockReceiver.hpp"
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#include "../../../Concurrency/AsyncTaskQueue.hpp"
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#include <cstring>
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namespace Outputs {
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namespace Speaker {
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/*!
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The low-pass speaker expects an Outputs::Speaker::SampleSource-derived
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template class, and uses the instance supplied to its constructor as the
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source of a high-frequency stream of audio which it filters down to a
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lower-frequency output.
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*/
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template <typename T> class LowpassSpeaker: public Speaker {
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public:
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LowpassSpeaker(T &sample_source) : sample_source_(sample_source) {}
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// Implemented as per Speaker.
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float get_ideal_clock_rate_in_range(float minimum, float maximum) {
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// return twice the cut off, if applicable
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if( filter_parameters_.high_frequency_cutoff > 0.0f &&
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filter_parameters_.input_cycles_per_second >= filter_parameters_.high_frequency_cutoff * 3.0f &&
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filter_parameters_.input_cycles_per_second <= filter_parameters_.high_frequency_cutoff * 3.0f)
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return filter_parameters_.high_frequency_cutoff * 3.0f;
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// return exactly the input rate if possible
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if( filter_parameters_.input_cycles_per_second >= minimum &&
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filter_parameters_.input_cycles_per_second <= maximum)
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return filter_parameters_.input_cycles_per_second;
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// if the input rate is lower, return the minimum
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if(filter_parameters_.input_cycles_per_second < minimum)
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return minimum;
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// otherwise, return the maximum
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return maximum;
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}
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// Implemented as per Speaker.
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void set_output_rate(float cycles_per_second, int buffer_size) {
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filter_parameters_.output_cycles_per_second = cycles_per_second;
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filter_parameters_.parameters_are_dirty = true;
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output_buffer_.resize(static_cast<std::size_t>(buffer_size));
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}
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/*!
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Sets the clock rate of the input audio.
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*/
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void set_input_rate(float cycles_per_second) {
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filter_parameters_.input_cycles_per_second = cycles_per_second;
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filter_parameters_.parameters_are_dirty = true;
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}
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/*!
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Allows a cut-off frequency to be specified for audio. Ordinarily this low-pass speaker
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will determine a cut-off based on the output audio rate. A caller can manually select
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an alternative cut-off. This allows machines with a low-pass filter on their audio output
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path to be explicit about its effect, and get that simulation for free.
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*/
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void set_high_frequency_cutoff(float high_frequency) {
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filter_parameters_.high_frequency_cutoff = high_frequency;
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filter_parameters_.parameters_are_dirty = true;
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}
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/*!
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Advances by the number of cycles specified, obtaining data from the sample source supplied
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at construction, filtering it and passing it on to the speaker's delegate if there is one.
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*/
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void run_for(const Cycles cycles) {
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std::size_t cycles_remaining = static_cast<size_t>(cycles.as_int());
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if(!cycles_remaining) return;
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if(filter_parameters_.parameters_are_dirty) update_filter_coefficients();
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// If input and output rates exactly match, and no additional cut-off has been specified,
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// just accumulate results and pass on.
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if( filter_parameters_.input_cycles_per_second == filter_parameters_.output_cycles_per_second &&
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filter_parameters_.high_frequency_cutoff < 0.0) {
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while(cycles_remaining) {
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std::size_t cycles_to_read = std::min(output_buffer_.size() - output_buffer_pointer_, cycles_remaining);
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sample_source_.get_samples(cycles_to_read, &output_buffer_[output_buffer_pointer_]);
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output_buffer_pointer_ += cycles_to_read;
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// announce to delegate if full
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if(output_buffer_pointer_ == output_buffer_.size()) {
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output_buffer_pointer_ = 0;
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if(delegate_) {
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delegate_->speaker_did_complete_samples(this, output_buffer_);
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}
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}
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cycles_remaining -= cycles_to_read;
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}
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return;
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}
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// if the output rate is less than the input rate, or an additional cut-off has been specified, use the filter.
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if( filter_parameters_.input_cycles_per_second > filter_parameters_.output_cycles_per_second ||
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(filter_parameters_.input_cycles_per_second == filter_parameters_.output_cycles_per_second && filter_parameters_.high_frequency_cutoff >= 0.0)) {
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while(cycles_remaining) {
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std::size_t cycles_to_read = std::min(cycles_remaining, input_buffer_.size() - input_buffer_depth_);
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sample_source_.get_samples(cycles_to_read, &input_buffer_[input_buffer_depth_]);
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cycles_remaining -= cycles_to_read;
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input_buffer_depth_ += cycles_to_read;
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if(input_buffer_depth_ == input_buffer_.size()) {
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output_buffer_[output_buffer_pointer_] = filter_->apply(input_buffer_.data());
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output_buffer_pointer_++;
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// Announce to delegate if full.
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if(output_buffer_pointer_ == output_buffer_.size()) {
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output_buffer_pointer_ = 0;
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if(delegate_) {
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delegate_->speaker_did_complete_samples(this, output_buffer_);
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}
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}
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// If the next loop around is going to reuse some of the samples just collected, use a memmove to
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// preserve them in the correct locations (TODO: use a longer buffer to fix that) and don't skip
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// anything. Otherwise skip as required to get to the next sample batch and don't expect to reuse.
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uint64_t steps = stepper_->step();
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if(steps < input_buffer_.size()) {
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int16_t *input_buffer = input_buffer_.data();
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std::memmove( input_buffer,
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&input_buffer[steps],
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sizeof(int16_t) * (input_buffer_.size() - steps));
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input_buffer_depth_ -= steps;
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} else {
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if(steps > input_buffer_.size())
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sample_source_.skip_samples(steps - input_buffer_.size());
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input_buffer_depth_ = 0;
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}
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}
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}
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return;
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}
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// TODO: input rate is less than output rate
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}
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/*!
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Provides a convenience shortcut for deferring a call to run_for.
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*/
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void run_for(Concurrency::DeferringAsyncTaskQueue &queue, const Cycles cycles) {
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queue.defer([this, cycles] {
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run_for(cycles);
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});
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}
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private:
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T &sample_source_;
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std::size_t output_buffer_pointer_ = 0;
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std::size_t input_buffer_depth_ = 0;
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std::vector<int16_t> input_buffer_;
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std::vector<int16_t> output_buffer_;
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std::unique_ptr<SignalProcessing::Stepper> stepper_;
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std::unique_ptr<SignalProcessing::FIRFilter> filter_;
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struct FilterParameters {
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float input_cycles_per_second = 0.0f;
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float output_cycles_per_second = 0.0f;
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float high_frequency_cutoff = -1.0;
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bool parameters_are_dirty = true;
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} filter_parameters_;
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void update_filter_coefficients() {
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// Make a guess at a good number of taps.
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std::size_t number_of_taps = static_cast<std::size_t>(
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ceilf((filter_parameters_.input_cycles_per_second + filter_parameters_.output_cycles_per_second) / filter_parameters_.output_cycles_per_second)
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);
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number_of_taps = (number_of_taps * 2) | 1;
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filter_parameters_.parameters_are_dirty = false;
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output_buffer_pointer_ = 0;
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stepper_.reset(new SignalProcessing::Stepper(
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static_cast<uint64_t>(filter_parameters_.input_cycles_per_second),
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static_cast<uint64_t>(filter_parameters_.output_cycles_per_second)));
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float high_pass_frequency = filter_parameters_.output_cycles_per_second / 2.0f;
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if(filter_parameters_.high_frequency_cutoff > 0.0) {
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high_pass_frequency = std::min(filter_parameters_.output_cycles_per_second / 2.0f, high_pass_frequency);
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}
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filter_.reset(new SignalProcessing::FIRFilter(
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static_cast<unsigned int>(number_of_taps),
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filter_parameters_.input_cycles_per_second,
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0.0,
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high_pass_frequency,
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SignalProcessing::FIRFilter::DefaultAttenuation));
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input_buffer_.resize(static_cast<std::size_t>(number_of_taps));
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input_buffer_depth_ = 0;
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}
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};
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}
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}
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#endif /* FilteringSpeaker_h */
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