Add audio interpolation helpers

include/audio/hle_mixer.hpp

@@ -0,0 +1,50 @@
+#pragma once
+#include <array>
+
+#include "audio/dsp_shared_mem.hpp"
+#include "helpers.hpp"
+
+namespace Audio {
+	using SampleFormat = HLE::SourceConfiguration::Configuration::Format;
+	using SourceType = HLE::SourceConfiguration::Configuration::MonoOrStereo;
+
+	class DSPMixer {
+	  public:
+		template <typename T, usize channelCount = 1>
+		using Sample = std::array<T, channelCount>;
+
+		template <typename T, usize channelCount>
+		using Frame = std::array<Sample<T, channelCount>, 160>;
+
+		template <typename T>
+		using MonoFrame = Frame<T, 1>;
+
+		template <typename T>
+		using StereoFrame = Frame<T, 2>;
+
+		template <typename T>
+		using QuadFrame = Frame<T, 4>;
+
+		// Internally the DSP uses four channels when mixing.
+		// Neatly, QuadFrame<s32> means that every sample is a uint32x4 value, which is particularly nice for SIMD mixing
+		using IntermediateMix = QuadFrame<s32>;
+
+	  private:
+		using ChannelFormat = HLE::DspConfiguration::OutputFormat;
+		// The audio from each DSP voice is converted to quadraphonic and then fed into 3 intermediate mixing stages
+		// Two of these intermediate mixers (second and third) are used for effects, including custom effects done on the CPU
+		static constexpr usize mixerStageCount = 3;
+
+	  public:
+		ChannelFormat channelFormat = ChannelFormat::Stereo;
+		std::array<float, mixerStageCount> volumes;
+		std::array<bool, 2> enableAuxStages;
+
+		void reset() {
+			channelFormat = ChannelFormat::Stereo;
+
+			volumes.fill(0.0);
+			enableAuxStages.fill(false);
+		}
+	};
+}  // namespace Audio