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// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include <array>
#include <vector>
#include "common/common_types.h"
namespace AudioCore {
/// Digital biquad filter:
///
/// b0 + b1 z^-1 + b2 z^-2
/// H(z) = ------------------------
/// a0 + a1 z^-1 + b2 z^-2
class Filter {
public:
/// Creates a low-pass filter.
/// @param cutoff Determines the cutoff frequency. A value from 0.0 to 1.0.
/// @param Q Determines the quality factor of this filter.
static Filter LowPass(double cutoff, double Q = 0.7071);
/// Passthrough filter.
Filter();
Filter(double a0_, double a1_, double a2_, double b0_, double b1_, double b2_);
void Process(std::vector<s16>& signal);
private:
static constexpr std::size_t channel_count = 2;
/// Coefficients are in normalized form (a0 = 1.0).
double a1, a2, b0, b1, b2;
/// Input History
std::array<std::array<double, channel_count>, 3> in;
/// Output History
std::array<std::array<double, channel_count>, 3> out;
};
/// Cascade filters to build up higher-order filters from lower-order ones.
class CascadingFilter {
public:
/// Creates a cascading low-pass filter.
/// @param cutoff Determines the cutoff frequency. A value from 0.0 to 1.0.
/// @param cascade_size Number of biquads in cascade.
static CascadingFilter LowPass(double cutoff, std::size_t cascade_size);
/// Passthrough.
CascadingFilter();
explicit CascadingFilter(std::vector<Filter> filters_);
void Process(std::vector<s16>& signal);
private:
std::vector<Filter> filters;
};
} // namespace AudioCore
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