From da845ddd9c35a1e1fcff03ea342636ae4bb8018b Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Mon, 6 Feb 2023 17:46:32 -0800
Subject: Use an interpolated FIR filter for cubic resampling
Similar to how the bsinc filters work, but optimized for 4-point filtering. At
least the SSE version is notably faster than calculating the coefficients in
real time.
---
core/mixer/mixer_c.cpp | 35 ++++++++++++++++++++++++++---------
1 file changed, 26 insertions(+), 9 deletions(-)
(limited to 'core/mixer/mixer_c.cpp')
diff --git a/core/mixer/mixer_c.cpp b/core/mixer/mixer_c.cpp
index 9ac2a9c4..24b9f0b7 100644
--- a/core/mixer/mixer_c.cpp
+++ b/core/mixer/mixer_c.cpp
@@ -5,7 +5,8 @@
#include <limits>
#include "alnumeric.h"
-#include "core/bsinc_tables.h"
+#include "core/bsinc_defs.h"
+#include "core/cubic_defs.h"
#include "defs.h"
#include "hrtfbase.h"
@@ -20,23 +21,39 @@ struct FastBSincTag;
namespace {
-constexpr uint FracPhaseBitDiff{MixerFracBits - BSincPhaseBits};
-constexpr uint FracPhaseDiffOne{1 << FracPhaseBitDiff};
+constexpr uint BsincPhaseBitDiff{MixerFracBits - BSincPhaseBits};
+constexpr uint BsincPhaseDiffOne{1 << BsincPhaseBitDiff};
+
+constexpr uint CubicPhaseBitDiff{MixerFracBits - CubicPhaseBits};
+constexpr uint CubicPhaseDiffOne{1 << CubicPhaseBitDiff};
+constexpr uint CubicPhaseDiffMask{CubicPhaseDiffOne - 1u};
inline float do_point(const InterpState&, const float *RESTRICT vals, const uint)
{ return vals[0]; }
inline float do_lerp(const InterpState&, const float *RESTRICT vals, const uint frac)
{ return lerpf(vals[0], vals[1], static_cast<float>(frac)*(1.0f/MixerFracOne)); }
-inline float do_cubic(const InterpState&, const float *RESTRICT vals, const uint frac)
-{ return cubic(vals[0], vals[1], vals[2], vals[3], static_cast<float>(frac)*(1.0f/MixerFracOne)); }
+inline float do_cubic(const InterpState &istate, const float *RESTRICT vals, const uint frac)
+{
+ /* Calculate the phase index and factor. */
+ const uint pi{frac >> CubicPhaseBitDiff};
+ const float pf{static_cast<float>(frac&CubicPhaseDiffMask) * (1.0f/CubicPhaseDiffOne)};
+
+ const CubicCoefficients *RESTRICT filter = al::assume_aligned<16>(istate.cubic.filter + pi);
+
+ // Apply the phase interpolated filter.
+ return (filter->mCoeffs[0] + pf*filter->mDeltas[0]) * vals[0]
+ + (filter->mCoeffs[1] + pf*filter->mDeltas[1]) * vals[1]
+ + (filter->mCoeffs[2] + pf*filter->mDeltas[2]) * vals[2]
+ + (filter->mCoeffs[3] + pf*filter->mDeltas[3]) * vals[3];
+}
inline float do_bsinc(const InterpState &istate, const float *RESTRICT vals, const uint frac)
{
const size_t m{istate.bsinc.m};
ASSUME(m > 0);
// Calculate the phase index and factor.
- const uint pi{frac >> FracPhaseBitDiff};
- const float pf{static_cast<float>(frac & (FracPhaseDiffOne-1)) * (1.0f/FracPhaseDiffOne)};
+ const uint pi{frac >> BsincPhaseBitDiff};
+ const float pf{static_cast<float>(frac & (BsincPhaseDiffOne-1)) * (1.0f/BsincPhaseDiffOne)};
const float *RESTRICT fil{istate.bsinc.filter + m*pi*2};
const float *RESTRICT phd{fil + m};
@@ -55,8 +72,8 @@ inline float do_fastbsinc(const InterpState &istate, const float *RESTRICT vals,
ASSUME(m > 0);
// Calculate the phase index and factor.
- const uint pi{frac >> FracPhaseBitDiff};
- const float pf{static_cast<float>(frac & (FracPhaseDiffOne-1)) * (1.0f/FracPhaseDiffOne)};
+ const uint pi{frac >> BsincPhaseBitDiff};
+ const float pf{static_cast<float>(frac & (BsincPhaseDiffOne-1)) * (1.0f/BsincPhaseDiffOne)};
const float *RESTRICT fil{istate.bsinc.filter + m*pi*2};
const float *RESTRICT phd{fil + m};
--
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