From 380658c21d39cf05ac765a9284da246388cca2a4 Mon Sep 17 00:00:00 2001
From: David Marcec <dmarcecguzman@gmail.com>
Date: Sun, 12 Jul 2020 21:59:14 +1000
Subject: audio_core: Apollo Part 1, AudioRenderer refactor

---
 src/audio_core/algorithm/interpolate.cpp | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

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

diff --git a/src/audio_core/algorithm/interpolate.cpp b/src/audio_core/algorithm/interpolate.cpp
index 49ab9d3e1..689a54508 100644
--- a/src/audio_core/algorithm/interpolate.cpp
+++ b/src/audio_core/algorithm/interpolate.cpp
@@ -197,4 +197,36 @@ std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input,
     return output;
 }
 
+void Resample(s32* output, const s32* input, s32 pitch, s32& fraction, std::size_t sample_count) {
+    const std::array<s16, 512>& lut = [pitch] {
+        if (pitch > 0xaaaa) {
+            return curve_lut0;
+        }
+        if (pitch <= 0x8000) {
+            return curve_lut1;
+        }
+        return curve_lut2;
+    }();
+
+    std::size_t index{};
+
+    for (std::size_t i = 0; i < sample_count; i++) {
+        const std::size_t lut_index{(static_cast<std::size_t>(fraction) >> 8) * 4};
+        const auto l0 = lut[lut_index + 0];
+        const auto l1 = lut[lut_index + 1];
+        const auto l2 = lut[lut_index + 2];
+        const auto l3 = lut[lut_index + 3];
+
+        const auto s0 = static_cast<s32>(input[index]);
+        const auto s1 = static_cast<s32>(input[index + 1]);
+        const auto s2 = static_cast<s32>(input[index + 2]);
+        const auto s3 = static_cast<s32>(input[index + 3]);
+
+        output[i] = (l0 * s0 + l1 * s1 + l2 * s2 + l3 * s3) >> 15;
+        fraction += pitch;
+        index += (fraction >> 15);
+        fraction &= 0x7fff;
+    }
+}
+
 } // namespace AudioCore
-- 
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