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Diffstat (limited to '')
-rw-r--r-- | src/audio_core/algorithm/interpolate.cpp | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/src/audio_core/algorithm/interpolate.cpp b/src/audio_core/algorithm/interpolate.cpp new file mode 100644 index 000000000..11459821f --- /dev/null +++ b/src/audio_core/algorithm/interpolate.cpp @@ -0,0 +1,71 @@ +// Copyright 2018 yuzu Emulator Project +// Licensed under GPLv2 or any later version +// Refer to the license.txt file included. + +#define _USE_MATH_DEFINES + +#include <algorithm> +#include <cmath> +#include <vector> +#include "audio_core/algorithm/interpolate.h" +#include "common/common_types.h" +#include "common/logging/log.h" + +namespace AudioCore { + +/// The Lanczos kernel +static double Lanczos(size_t a, double x) { + if (x == 0.0) + return 1.0; + const double px = M_PI * x; + return a * std::sin(px) * std::sin(px / a) / (px * px); +} + +std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input, double ratio) { + if (input.size() < 2) + return {}; + + if (ratio <= 0) { + LOG_CRITICAL(Audio, "Nonsensical interpolation ratio {}", ratio); + ratio = 1.0; + } + + if (ratio != state.current_ratio) { + const double cutoff_frequency = std::min(0.5 / ratio, 0.5 * ratio); + state.nyquist = CascadingFilter::LowPass(std::clamp(cutoff_frequency, 0.0, 0.4), 3); + state.current_ratio = ratio; + } + state.nyquist.Process(input); + + constexpr size_t taps = InterpolationState::lanczos_taps; + const size_t num_frames = input.size() / 2; + + std::vector<s16> output; + output.reserve(static_cast<size_t>(input.size() / ratio + 4)); + + double& pos = state.position; + auto& h = state.history; + for (size_t i = 0; i < num_frames; ++i) { + std::rotate(h.begin(), h.end() - 1, h.end()); + h[0][0] = input[i * 2 + 0]; + h[0][1] = input[i * 2 + 1]; + + while (pos <= 1.0) { + double l = 0.0; + double r = 0.0; + for (size_t j = 0; j < h.size(); j++) { + l += Lanczos(taps, pos + j - taps + 1) * h[j][0]; + r += Lanczos(taps, pos + j - taps + 1) * h[j][1]; + } + output.emplace_back(static_cast<s16>(std::clamp(l, -32768.0, 32767.0))); + output.emplace_back(static_cast<s16>(std::clamp(r, -32768.0, 32767.0))); + + pos += ratio; + } + pos -= 1.0; + } + + return output; +} + +} // namespace AudioCore |