implement openal hrtf audio support

- upgrade openal version
        - add support to create openal context with hrtf enabled
        - add option in audio settings for hrtf enablement
        - add static property on Audio class for runtime toggling of hrtf
	- fix bug with left/right and front/back being reversed

Source/Engine/Audio/Audio.cpp

@@ -57,6 +57,7 @@ namespace
     float Volume = 1.0f;
     int32 ActiveDeviceIndex = -1;
     bool MuteOnFocusLoss = true;
+    bool UseHRTFWhenAvailable = true;
 }
 
 class AudioService : public EngineService
@@ -94,6 +95,7 @@ void AudioSettings::Apply()
     if (AudioBackend::Instance != nullptr)
     {
         Audio::SetDopplerFactor(DopplerFactor);
+        Audio::SetUseHRTFWhenAvailable(UseHRTFWhenAvailable);
     }
 }
 
@@ -141,6 +143,17 @@ void Audio::SetDopplerFactor(float value)
     AudioBackend::SetDopplerFactor(value);
 }
 
+bool Audio::GetUseHRTFWhenAvailable()
+{
+    return UseHRTFWhenAvailable;
+}
+
+void Audio::SetUseHRTFWhenAvailable(bool value)
+{
+    UseHRTFWhenAvailable = value;
+    AudioBackend::Listener::ReinitializeAll();
+}
+
 void Audio::OnAddListener(AudioListener* listener)
 {
     ASSERT(!Listeners.Contains(listener));

Source/Engine/Audio/Audio.h

@@ -13,7 +13,7 @@
 /// </summary>
 API_CLASS(Static) class FLAXENGINE_API Audio
 {
-DECLARE_SCRIPTING_TYPE_NO_SPAWN(Audio);
+    DECLARE_SCRIPTING_TYPE_NO_SPAWN(Audio);
     friend class AudioStreamingHandler;
     friend class AudioClip;
 
@@ -90,6 +90,17 @@ public:
     /// <param name="value">The value.</param>
     API_PROPERTY() static void SetDopplerFactor(float value);
 
+    /// <summary>
+    /// Gets the preference to use HRTF audio when available.  Default is true.
+    /// </summary>
+    API_PROPERTY() static bool GetUseHRTFWhenAvailable();
+
+    /// <summary>
+    /// Sets the preference to use HRTF audio when available.  Default is true.
+    /// </summary>
+    /// <param name="value">The value.</param>
+    API_PROPERTY() static void SetUseHRTFWhenAvailable(bool value);
+
 public:
 
     static void OnAddListener(AudioListener* listener);

Source/Engine/Audio/AudioBackend.h

@@ -25,6 +25,7 @@ private:
     virtual void Listener_OnRemove(AudioListener* listener) = 0;
     virtual void Listener_VelocityChanged(AudioListener* listener) = 0;
     virtual void Listener_TransformChanged(AudioListener* listener) = 0;
+    virtual void Listener_ReinitializeAll() = 0;
 
     // Source
     virtual void Source_OnAdd(AudioSource* source) = 0;
@@ -94,6 +95,11 @@ public:
         {
             Instance->Listener_TransformChanged(listener);
         }
+
+        FORCE_INLINE static void ReinitializeAll()
+        {
+            Instance->Listener_ReinitializeAll();
+        }
     };
 
     class Source

Source/Engine/Audio/AudioSettings.h

@@ -31,6 +31,14 @@ public:
     API_FIELD(Attributes="EditorOrder(200), DefaultValue(true), EditorDisplay(\"General\", \"Mute On Focus Loss\")")
     bool MuteOnFocusLoss = true;
 
+    /// <summary>
+    /// Enables/disables HRTF audio for in-engine processing of 3d audio.
+    /// If enabled, the user should be using two-channel/headphones audio output and have all other surround virtualization disabled (Atmos, DTS:X, vendor specific, etc.)
+    /// Note: this is currently only available with the OpenAL audio backend.
+    /// </summary>
+    API_FIELD(Attributes="EditorOrder(300), DefaultValue(true), EditorDisplay(\"Spatial Audio\")")
+    bool UseHRTFWhenAvailable = true;
+
 public:
 
     /// <summary>
@@ -46,5 +54,6 @@ public:
         DESERIALIZE(DisableAudio);
         DESERIALIZE(DopplerFactor);
         DESERIALIZE(MuteOnFocusLoss);
+        DESERIALIZE(UseHRTFWhenAvailable);
     }
 };

Source/Engine/Audio/None/AudioBackendNone.cpp

@@ -22,6 +22,10 @@ void AudioBackendNone::Listener_TransformChanged(AudioListener* listener)
 {
 }
 
+void AudioBackendNone::Listener_ReinitializeAll()
+{
+}
+
 void AudioBackendNone::Source_OnAdd(AudioSource* source)
 {
     source->Restore();

Source/Engine/Audio/None/AudioBackendNone.h

@@ -18,6 +18,7 @@ public:
     void Listener_OnRemove(AudioListener* listener) override;
     void Listener_VelocityChanged(AudioListener* listener) override;
     void Listener_TransformChanged(AudioListener* listener) override;
+    void Listener_ReinitializeAll() override;
     void Source_OnAdd(AudioSource* source) override;
     void Source_OnRemove(AudioSource* source) override;
     void Source_VelocityChanged(AudioSource* source) override;

Source/Engine/Audio/OpenAL/AudioBackendOAL.cpp

@@ -17,10 +17,11 @@
 //#define AL_LIBTYPE_STATIC
 #include <OpenAL/al.h>
 #include <OpenAL/alc.h>
+#include <OpenAL/alext.h>
 
 #define ALC_MULTIPLE_LISTENERS 0
 
-#define FLAX_POS_TO_OAL(vec) ((ALfloat)vec.X * -0.01f), ((ALfloat)vec.Y * 0.01f), ((ALfloat)vec.Z * -0.01f)
+#define FLAX_POS_TO_OAL(vec) ((ALfloat)vec.X * -0.01f), ((ALfloat)vec.Y * 0.01f), ((ALfloat)vec.Z * 0.01f)
 #if BUILD_RELEASE
 #define ALC_CHECK_ERROR(method)
 #else
@@ -55,7 +56,6 @@
 namespace ALC
 {
     ALCdevice* Device = nullptr;
-    bool AL_EXT_float32 = false;
     Array<ALCcontext*, FixedAllocation<AUDIO_MAX_LISTENERS>> Contexts;
 
     bool IsExtensionSupported(const char* extension)
@@ -156,7 +156,7 @@ namespace ALC
 
     void RebuildContexts(bool isChangingDevice)
     {
-        LOG(Info, "Rebuild audio contexts");
+        LOG(Info, "Audio: Rebuilding audio contexts");
 
         if (!isChangingDevice)
         {
@@ -180,7 +180,18 @@ namespace ALC
         }
 #else
         Contexts.Resize(1);
-        Contexts[0] = alcCreateContext(Device, nullptr);
+
+        if (Audio::GetUseHRTFWhenAvailable())
+        {
+            LOG(Info, "Audio: Enabling OpenAL HRTF");
+
+            ALCint attrs[] = { ALC_HRTF_SOFT, ALC_TRUE };
+            Contexts[0] = alcCreateContext(Device, attrs);
+        }
+        else
+        {
+            Contexts[0] = alcCreateContext(Device, nullptr);
+        }
 #endif
 
         // If only one context is available keep it active as an optimization.
@@ -315,6 +326,11 @@ void AudioBackendOAL::Listener_TransformChanged(AudioListener* listener)
     alListener3f(AL_POSITION, FLAX_POS_TO_OAL(position));
 }
 
+void AudioBackendOAL::Listener_ReinitializeAll()
+{
+    ALC::RebuildContexts(false);
+}
+
 void AudioBackendOAL::Source_OnAdd(AudioSource* source)
 {
     ALC::Source::Rebuild(source);
@@ -567,7 +583,7 @@ void AudioBackendOAL::Buffer_Write(uint32 bufferId, byte* samples, const AudioDa
     {
         if (info.BitDepth > 16)
         {
-            if (ALC::AL_EXT_float32)
+            if (ALC::IsExtensionSupported("AL_EXT_float32"))
             {
                 const uint32 bufferSize = info.NumSamples * sizeof(float);
                 float* sampleBufferFloat = (float*)Allocator::Allocate(bufferSize);
@@ -688,7 +704,6 @@ void AudioBackendOAL::Base_OnActiveDeviceChanged()
     }
 
     // Setup
-    ALC::AL_EXT_float32 = ALC::IsExtensionSupported("AL_EXT_float32");
     ALC::RebuildContexts(true);
 }
 
@@ -800,7 +815,6 @@ bool AudioBackendOAL::Base_Init()
     }
 
     // Init
-    ALC::AL_EXT_float32 = ALC::IsExtensionSupported("AL_EXT_float32");
     SetDopplerFactor(AudioSettings::Get()->DopplerFactor);
     ALC::RebuildContexts(true);
     Audio::SetActiveDeviceIndex(activeDeviceIndex);

Source/Engine/Audio/OpenAL/AudioBackendOAL.h

@@ -18,6 +18,7 @@ public:
     void Listener_OnRemove(AudioListener* listener) override;
     void Listener_VelocityChanged(AudioListener* listener) override;
     void Listener_TransformChanged(AudioListener* listener) override;
+    void Listener_ReinitializeAll() override;
     void Source_OnAdd(AudioSource* source) override;
     void Source_OnRemove(AudioSource* source) override;
     void Source_VelocityChanged(AudioSource* source) override;

Source/Engine/Audio/XAudio2/AudioBackendXAudio2.cpp

@@ -331,6 +331,11 @@ void AudioBackendXAudio2::Listener_TransformChanged(AudioListener* listener)
     }
 }
 
+void AudioBackendXAudio2::Listener_ReinitializeAll()
+{
+    // TODO: Implement XAudio2 reinitialization; read HRTF audio value from Audio class
+}
+
 void AudioBackendXAudio2::Source_OnAdd(AudioSource* source)
 {
     // Skip if has no clip (needs audio data to create a source - needs data format information)

Source/Engine/Audio/XAudio2/AudioBackendXAudio2.h

@@ -18,6 +18,7 @@ public:
     void Listener_OnRemove(AudioListener* listener) override;
     void Listener_VelocityChanged(AudioListener* listener) override;
     void Listener_TransformChanged(AudioListener* listener) override;
+    void Listener_ReinitializeAll() override;
     void Source_OnAdd(AudioSource* source) override;
     void Source_OnRemove(AudioSource* source) override;
     void Source_VelocityChanged(AudioSource* source) override;