From 4b44b8b4fba5ddfe28e5c6bd418f48ba475eaa79 Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Sun, 12 Aug 2018 19:32:39 +0100
Subject: audio_core: Interpolate

---
 src/audio_core/algorithm/interpolate.h | 43 ++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 src/audio_core/algorithm/interpolate.h

(limited to 'src/audio_core/algorithm/interpolate.h')

diff --git a/src/audio_core/algorithm/interpolate.h b/src/audio_core/algorithm/interpolate.h
new file mode 100644
index 000000000..c79c2eef4
--- /dev/null
+++ b/src/audio_core/algorithm/interpolate.h
@@ -0,0 +1,43 @@
+// Copyright 2018 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <vector>
+#include "audio_core/algorithm/filter.h"
+#include "common/common_types.h"
+
+namespace AudioCore {
+
+struct InterpolationState {
+    static constexpr size_t lanczos_taps = 4;
+    static constexpr size_t history_size = lanczos_taps * 2 - 1;
+
+    double current_ratio = 0.0;
+    CascadingFilter nyquist;
+    std::array<std::array<s16, 2>, history_size> history = {};
+    double position = 0;
+};
+
+/// Interpolates input signal to produce output signal.
+/// @param input The signal to interpolate.
+/// @param ratio Interpolation ratio.
+///              ratio > 1.0 results in fewer output samples.
+///              ratio < 1.0 results in more output samples.
+/// @returns Output signal.
+std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input, double ratio);
+
+/// Interpolates input signal to produce output signal.
+/// @param input The signal to interpolate.
+/// @param input_rate The sample rate of input.
+/// @param output_rate The desired sample rate of the output.
+/// @returns Output signal.
+inline std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input,
+                                    u32 input_rate, u32 output_rate) {
+    const double ratio = static_cast<double>(input_rate) / static_cast<double>(output_rate);
+    return Interpolate(state, std::move(input), ratio);
+}
+
+} // namespace AudioCore
-- 
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