Fix missing audio on OpenAL when changing active device

#3621

Source/Engine/Audio/AudioClip.cpp

@@ -132,9 +132,7 @@ int32 AudioClip::GetFirstBufferIndex(float time, float& offset) const
         if (_buffersStartTimes[i + 1] > time)
         {
             offset = time - _buffersStartTimes[i];
-#if BUILD_DEBUG
-            ASSERT(Math::Abs(GetBufferStartTime(i) + offset - time) < 0.001f);
-#endif
+            ASSERT_LOW_LAYER(Math::Abs(GetBufferStartTime(i) + offset - time) < 0.001f);
             return i;
         }
     }

Source/Engine/Audio/AudioClip.h

@@ -18,6 +18,7 @@ class AudioSource;
 API_CLASS(NoSpawn) class FLAXENGINE_API AudioClip : public BinaryAsset, public StreamableResource
 {
     DECLARE_BINARY_ASSET_HEADER(AudioClip, 2);
+    friend class AudioBackendOAL;
 
 public:
     /// <summary>

Source/Engine/Audio/OpenAL/AudioBackendOAL.cpp

@@ -14,6 +14,9 @@
 #include "Engine/Audio/AudioListener.h"
 #include "Engine/Audio/AudioSource.h"
 #include "Engine/Audio/AudioSettings.h"
+#include "Engine/Content/Content.h"
+#include "Engine/Level/Level.h"
+#include "Engine/Video/VideoPlayer.h"
 
 // Include OpenAL library
 // Source: https://github.com/kcat/openal-soft
@@ -73,6 +76,7 @@ namespace ALC
     ALCdevice* Device = nullptr;
     ALCcontext* Context = nullptr;
     AudioBackend::FeatureFlags Features = AudioBackend::FeatureFlags::None;
+    bool Inited = false;
     CriticalSection Locker;
     Dictionary<uint32, SourceData> SourcesData;
 
@@ -164,12 +168,9 @@ namespace ALC
         float Time;
     };
 
-    void RebuildContext(const Array<AudioSourceState>& states)
+    void RebuildContext()
     {
-        LOG(Info, "Rebuilding audio contexts");
-
         ClearContext();
-
         if (Device == nullptr)
             return;
 
@@ -182,10 +183,16 @@ namespace ALC
 
         Context = alcCreateContext(Device, attrList);
         alcMakeContextCurrent(Context);
-
+    }
+    
+    void RebuildListeners()
+    {
         for (AudioListener* listener : Audio::Listeners)
             Listener::Rebuild(listener);
-
+    }
+    
+    void RebuildSources(const Array<AudioSourceState>& states)
+    {
         for (int32 i = 0; i < states.Count(); i++)
         {
             AudioSource* source = Audio::Sources[i];
@@ -205,6 +212,13 @@ namespace ALC
         }
     }
 
+    void RebuildContext(const Array<AudioSourceState>& states)
+    {
+        RebuildContext();
+        RebuildListeners();
+        RebuildSources(states);
+    }
+
     void RebuildContext(bool isChangingDevice)
     {
         Array<AudioSourceState> states;
@@ -629,6 +643,7 @@ AudioBackend::FeatureFlags AudioBackendOAL::Base_Features()
 
 void AudioBackendOAL::Base_OnActiveDeviceChanged()
 {
+    PROFILE_CPU();
     PROFILE_MEM(Audio);
 
     // Cleanup
@@ -659,9 +674,55 @@ void AudioBackendOAL::Base_OnActiveDeviceChanged()
         LOG(Fatal, "Failed to open OpenAL device ({0}).", String(name));
         return;
     }
+    if (ALC::Inited)
+        LOG(Info, "Changed audio device to: {}", String(Audio::GetActiveDevice()->Name));
 
-    // Setup
-    ALC::RebuildContext(states);
+    // Rebuild context
+    ALC::RebuildContext();
+    if (ALC::Inited)
+    {
+        // Reload all audio clips to recreate their buffers
+        for (Asset* asset : Content::GetAssets())
+        {
+            if (auto* audioClip = ScriptingObject::Cast<AudioClip>(asset))
+            {
+                ScopeLock lock(audioClip->Locker);
+
+                // Clear old buffer IDs
+                for (uint32& bufferID : audioClip->Buffers)
+                    bufferID = 0;
+
+                if (audioClip->IsStreamable())
+                {
+                    // Let the streaming recreate missing buffers
+                    audioClip->RequestStreamingUpdate();
+                }
+                else
+                {
+                    // Reload audio clip
+                    auto assetLock = audioClip->Storage->Lock();
+                    audioClip->LoadChunk(0);
+                    audioClip->Buffers[0] = AudioBackend::Buffer::Create();
+                    audioClip->WriteBuffer(0);
+
+                }
+            }
+        }
+
+        // Reload all videos to recreate their buffers
+        for (VideoPlayer* videoPlayer : Level::GetActors<VideoPlayer>(true))
+        {
+            VideoBackendPlayer& player = videoPlayer->_player;
+
+            // Clear audio state
+            for (uint32& bufferID : player.AudioBuffers)
+                bufferID = 0;
+            player.NextAudioBuffer = 0;
+            player.AudioSource = 0;
+        }
+    }
+    ALC::RebuildListeners();
+    ALC::RebuildSources(states);
 }
 
 void AudioBackendOAL::Base_SetDopplerFactor(float value)
@@ -782,6 +843,7 @@ bool AudioBackendOAL::Base_Init()
     if (ALC::IsExtensionSupported("AL_SOFT_source_spatialize"))
         ALC::Features = EnumAddFlags(ALC::Features, FeatureFlags::SpatialMultiChannel);
 #endif
+    ALC::Inited = true;
 
     // Log service info
     LOG(Info, "{0} ({1})", String(alGetString(AL_RENDERER)), String(alGetString(AL_VERSION)));

Source/Engine/Level/Level.h

@@ -473,6 +473,19 @@ public:
     /// <returns>Found actors list.</returns>
     API_FUNCTION() static Array<Actor*> GetActors(API_PARAM(Attributes="TypeReference(typeof(Actor))") const MClass* type, bool activeOnly = false);
 
+    /// <summary>
+    /// Finds all the actors of the given type in all the loaded scenes.
+    /// </summary>
+    /// <typeparam name="T">Type of the object.</typeparam>
+    /// <param name="activeOnly">Finds only active actors.</param>
+    /// <returns>Found actors list.</returns>
+    template<typename T>
+    static Array<T*> GetActors(bool activeOnly = false)
+    {
+        Array<Actor*> actors = GetActors(T::GetStaticClass(), activeOnly);
+        return *(Array<T*>*)&actors;
+    }
+
     /// <summary>
     /// Finds all the scripts of the given type in an actor or all the loaded scenes.
     /// </summary>

Source/Engine/Video/VideoPlayer.h

@@ -15,6 +15,7 @@ class FLAXENGINE_API VideoPlayer : public Actor
 {
     DECLARE_SCENE_OBJECT(VideoPlayer);
     API_AUTO_SERIALIZATION();
+    friend class AudioBackendOAL;
 
 public:
     /// <summary>