From 0fe38c053d8dd827e774fbe0aef121e7aa0a0f28 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Sun, 25 Apr 2021 11:36:37 -0700
Subject: Move some functions to core

And clean up more includes
---
 core/mixer.h | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 core/mixer.h

(limited to 'core/mixer.h')

diff --git a/core/mixer.h b/core/mixer.h
new file mode 100644
index 00000000..309f4224
--- /dev/null
+++ b/core/mixer.h
@@ -0,0 +1,101 @@
+#ifndef CORE_MIXER_H
+#define CORE_MIXER_H
+
+#include <array>
+#include <cmath>
+#include <stddef.h>
+#include <type_traits>
+
+#include "alspan.h"
+#include "ambidefs.h"
+#include "bufferline.h"
+#include "devformat.h"
+
+struct MixParams;
+
+using MixerFunc = void(*)(const al::span<const float> InSamples,
+    const al::span<FloatBufferLine> OutBuffer, float *CurrentGains, const float *TargetGains,
+    const size_t Counter, const size_t OutPos);
+
+extern MixerFunc MixSamples;
+
+
+/**
+ * Calculates ambisonic encoder coefficients using the X, Y, and Z direction
+ * components, which must represent a normalized (unit length) vector, and the
+ * spread is the angular width of the sound (0...tau).
+ *
+ * NOTE: The components use ambisonic coordinates. As a result:
+ *
+ * Ambisonic Y = OpenAL -X
+ * Ambisonic Z = OpenAL Y
+ * Ambisonic X = OpenAL -Z
+ *
+ * The components are ordered such that OpenAL's X, Y, and Z are the first,
+ * second, and third parameters respectively -- simply negate X and Z.
+ */
+std::array<float,MaxAmbiChannels> CalcAmbiCoeffs(const float y, const float z, const float x,
+    const float spread);
+
+/**
+ * CalcDirectionCoeffs
+ *
+ * Calculates ambisonic coefficients based on an OpenAL direction vector. The
+ * vector must be normalized (unit length), and the spread is the angular width
+ * of the sound (0...tau).
+ */
+inline std::array<float,MaxAmbiChannels> CalcDirectionCoeffs(const float (&dir)[3],
+    const float spread)
+{
+    /* Convert from OpenAL coords to Ambisonics. */
+    return CalcAmbiCoeffs(-dir[0], dir[1], -dir[2], spread);
+}
+
+/**
+ * CalcAngleCoeffs
+ *
+ * Calculates ambisonic coefficients based on azimuth and elevation. The
+ * azimuth and elevation parameters are in radians, going right and up
+ * respectively.
+ */
+inline std::array<float,MaxAmbiChannels> CalcAngleCoeffs(const float azimuth,
+    const float elevation, const float spread)
+{
+    const float x{-std::sin(azimuth) * std::cos(elevation)};
+    const float y{ std::sin(elevation)};
+    const float z{ std::cos(azimuth) * std::cos(elevation)};
+
+    return CalcAmbiCoeffs(x, y, z, spread);
+}
+
+
+/**
+ * ComputePanGains
+ *
+ * Computes panning gains using the given channel decoder coefficients and the
+ * pre-calculated direction or angle coefficients. For B-Format sources, the
+ * coeffs are a 'slice' of a transform matrix for the input channel, used to
+ * scale and orient the sound samples.
+ */
+void ComputePanGains(const MixParams *mix, const float*RESTRICT coeffs, const float ingain,
+    const al::span<float,MAX_OUTPUT_CHANNELS> gains);
+
+
+/** Helper to set an identity/pass-through panning for ambisonic mixing (3D input). */
+template<typename T, typename I, typename F>
+auto SetAmbiPanIdentity(T iter, I count, F func) -> std::enable_if_t<std::is_integral<I>::value>
+{
+    if(count < 1) return;
+
+    std::array<float,MaxAmbiChannels> coeffs{{1.0f}};
+    func(*iter, coeffs);
+    ++iter;
+    for(I i{1};i < count;++i,++iter)
+    {
+        coeffs[i-1] = 0.0f;
+        coeffs[i  ] = 1.0f;
+        func(*iter, coeffs);
+    }
+}
+
+#endif /* CORE_MIXER_H */
-- 
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