71 lines
2.1 KiB
C++
71 lines
2.1 KiB
C++
// Copyright 2018 yuzu Emulator Project
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#define _USE_MATH_DEFINES
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#include <algorithm>
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#include <cmath>
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#include <vector>
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#include "audio_core/algorithm/interpolate.h"
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#include "common/common_types.h"
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#include "common/logging/log.h"
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namespace AudioCore {
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/// The Lanczos kernel
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static double Lanczos(std::size_t a, double x) {
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if (x == 0.0)
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return 1.0;
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const double px = M_PI * x;
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return a * std::sin(px) * std::sin(px / a) / (px * px);
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}
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std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input, double ratio) {
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if (input.size() < 2)
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return {};
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if (ratio <= 0) {
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LOG_CRITICAL(Audio, "Nonsensical interpolation ratio {}", ratio);
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ratio = 1.0;
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}
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if (ratio != state.current_ratio) {
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const double cutoff_frequency = std::min(0.5 / ratio, 0.5 * ratio);
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state.nyquist = CascadingFilter::LowPass(std::clamp(cutoff_frequency, 0.0, 0.4), 3);
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state.current_ratio = ratio;
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}
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state.nyquist.Process(input);
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constexpr std::size_t taps = InterpolationState::lanczos_taps;
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const std::size_t num_frames = input.size() / 2;
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std::vector<s16> output;
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output.reserve(static_cast<std::size_t>(input.size() / ratio + 4));
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double& pos = state.position;
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auto& h = state.history;
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for (std::size_t i = 0; i < num_frames; ++i) {
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std::rotate(h.begin(), h.end() - 1, h.end());
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h[0][0] = input[i * 2 + 0];
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h[0][1] = input[i * 2 + 1];
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while (pos <= 1.0) {
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double l = 0.0;
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double r = 0.0;
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for (std::size_t j = 0; j < h.size(); j++) {
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l += Lanczos(taps, pos + j - taps + 1) * h[j][0];
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r += Lanczos(taps, pos + j - taps + 1) * h[j][1];
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}
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output.emplace_back(static_cast<s16>(std::clamp(l, -32768.0, 32767.0)));
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output.emplace_back(static_cast<s16>(std::clamp(r, -32768.0, 32767.0)));
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pos += ratio;
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}
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pos -= 1.0;
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}
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return output;
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}
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} // namespace AudioCore
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