diff --git a/src/audio_core/algorithm/interpolate.cpp b/src/audio_core/algorithm/interpolate.cpp
index a58f24169d..49ab9d3e15 100644
--- a/src/audio_core/algorithm/interpolate.cpp
+++ b/src/audio_core/algorithm/interpolate.cpp
@@ -8,13 +8,14 @@
#include <climits>
#include <cmath>
#include <vector>
+
#include "audio_core/algorithm/interpolate.h"
#include "common/common_types.h"
#include "common/logging/log.h"
namespace AudioCore {
-constexpr std::array<s16, 512> curve_lut0 = {
+constexpr std::array<s16, 512> curve_lut0{
6600, 19426, 6722, 3, 6479, 19424, 6845, 9, 6359, 19419, 6968, 15, 6239,
19412, 7093, 22, 6121, 19403, 7219, 28, 6004, 19391, 7345, 34, 5888, 19377,
7472, 41, 5773, 19361, 7600, 48, 5659, 19342, 7728, 55, 5546, 19321, 7857,
@@ -56,7 +57,7 @@ constexpr std::array<s16, 512> curve_lut0 = {
19403, 6121, 22, 7093, 19412, 6239, 15, 6968, 19419, 6359, 9, 6845, 19424,
6479, 3, 6722, 19426, 6600};
-constexpr std::array<s16, 512> curve_lut1 = {
+constexpr std::array<s16, 512> curve_lut1{
-68, 32639, 69, -5, -200, 32630, 212, -15, -328, 32613, 359, -26, -450,
32586, 512, -36, -568, 32551, 669, -47, -680, 32507, 832, -58, -788, 32454,
1000, -69, -891, 32393, 1174, -80, -990, 32323, 1352, -92, -1084, 32244, 1536,
@@ -98,7 +99,7 @@ constexpr std::array<s16, 512> curve_lut1 = {
32551, -568, -36, 512, 32586, -450, -26, 359, 32613, -328, -15, 212, 32630,
-200, -5, 69, 32639, -68};
-constexpr std::array<s16, 512> curve_lut2 = {
+constexpr std::array<s16, 512> curve_lut2{
3195, 26287, 3329, -32, 3064, 26281, 3467, -34, 2936, 26270, 3608, -38, 2811,
26253, 3751, -42, 2688, 26230, 3897, -46, 2568, 26202, 4046, -50, 2451, 26169,
4199, -54, 2338, 26130, 4354, -58, 2227, 26085, 4512, -63, 2120, 26035, 4673,
@@ -146,10 +147,10 @@ std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input,
if (ratio <= 0) {
LOG_CRITICAL(Audio, "Nonsensical interpolation ratio {}", ratio);
- ratio = 1.0;
+ return input;
}
- const int step = static_cast<int>(ratio * 0x8000);
+ const s32 step{static_cast<s32>(ratio * 0x8000)};
const std::array<s16, 512>& lut = [step] {
if (step > 0xaaaa) {
return curve_lut0;
@@ -160,28 +161,37 @@ std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input,
return curve_lut2;
}();
- std::vector<s16> output(static_cast<std::size_t>(input.size() / ratio));
- int in_offset = 0;
- for (std::size_t out_offset = 0; out_offset < output.size(); out_offset += 2) {
- const int lut_index = (state.fraction >> 8) * 4;
+ const std::size_t num_frames{input.size() / 2};
- const int l = input[(in_offset + 0) * 2 + 0] * lut[lut_index + 0] +
- input[(in_offset + 1) * 2 + 0] * lut[lut_index + 1] +
- input[(in_offset + 2) * 2 + 0] * lut[lut_index + 2] +
- input[(in_offset + 3) * 2 + 0] * lut[lut_index + 3];
+ std::vector<s16> output;
+ output.reserve(static_cast<std::size_t>(input.size() / ratio + InterpolationState::taps));
- const int r = input[(in_offset + 0) * 2 + 1] * lut[lut_index + 0] +
- input[(in_offset + 1) * 2 + 1] * lut[lut_index + 1] +
- input[(in_offset + 2) * 2 + 1] * lut[lut_index + 2] +
- input[(in_offset + 3) * 2 + 1] * lut[lut_index + 3];
+ for (std::size_t frame{}; frame < num_frames; ++frame) {
+ const std::size_t lut_index{(state.fraction >> 8) * InterpolationState::taps};
- const int new_offset = state.fraction + step;
+ std::rotate(state.history.begin(), state.history.end() - 1, state.history.end());
+ state.history[0][0] = input[frame * 2 + 0];
+ state.history[0][1] = input[frame * 2 + 1];
- in_offset += new_offset >> 15;
- state.fraction = new_offset & 0x7fff;
+ while (state.position <= 1.0) {
+ const s32 left{state.history[0][0] * lut[lut_index + 0] +
+ state.history[1][0] * lut[lut_index + 1] +
+ state.history[2][0] * lut[lut_index + 2] +
+ state.history[3][0] * lut[lut_index + 3]};
+ const s32 right{state.history[0][1] * lut[lut_index + 0] +
+ state.history[1][1] * lut[lut_index + 1] +
+ state.history[2][1] * lut[lut_index + 2] +
+ state.history[3][1] * lut[lut_index + 3]};
+ const s32 new_offset{state.fraction + step};
- output[out_offset + 0] = static_cast<s16>(std::clamp(l >> 15, SHRT_MIN, SHRT_MAX));
- output[out_offset + 1] = static_cast<s16>(std::clamp(r >> 15, SHRT_MIN, SHRT_MAX));
+ state.fraction = new_offset & 0x7fff;
+
+ output.emplace_back(static_cast<s16>(std::clamp(left >> 15, SHRT_MIN, SHRT_MAX)));
+ output.emplace_back(static_cast<s16>(std::clamp(right >> 15, SHRT_MIN, SHRT_MAX)));
+
+ state.position += ratio;
+ }
+ state.position -= 1.0;
}
return output;
diff --git a/src/audio_core/algorithm/interpolate.h b/src/audio_core/algorithm/interpolate.h
index 1b9831a753..ab1a31754e 100644
--- a/src/audio_core/algorithm/interpolate.h
+++ b/src/audio_core/algorithm/interpolate.h
@@ -6,12 +6,17 @@
#include <array>
#include <vector>
+
#include "common/common_types.h"
namespace AudioCore {
struct InterpolationState {
- int fraction = 0;
+ static constexpr std::size_t taps{4};
+ static constexpr std::size_t history_size{taps * 2 - 1};
+ std::array<std::array<s16, 2>, history_size> history{};
+ double position{};
+ s32 fraction{};
};
/// Interpolates input signal to produce output signal.