audio: switch waveout backend to pull rendering

engine/include/XCEngine/Audio/AudioSystem.h

@@ -7,6 +7,7 @@
 #include <XCEngine/Core/Math/Vector3.h>
 #include <XCEngine/Core/Math/Quaternion.h>
 #include <memory>
+#include <mutex>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
@@ -22,6 +23,7 @@ namespace Audio {
 class AudioSystem {
 public:
     static AudioSystem& Get();
+    static AudioSystem* TryGetExisting();
 
     void Initialize(const AudioConfig& config);
     void Shutdown();
@@ -30,6 +32,9 @@ public:
 
     void SetBackend(std::unique_ptr<IAudioBackend> backend);
     IAudioBackend* GetBackend() const { return m_backend.get(); }
+    [[nodiscard]] std::unique_lock<std::recursive_mutex> AcquireStateLock() {
+        return std::unique_lock<std::recursive_mutex>(m_stateMutex);
+    }
     AudioMixer& GetMasterMixer() { return m_masterMixer; }
     const AudioMixer& GetMasterMixer() const { return m_masterMixer; }
 
@@ -80,8 +85,8 @@ public:
     const Stats& GetStats() const { return m_stats; }
 
 private:
-    AudioSystem() = default;
-    ~AudioSystem() = default;
+    AudioSystem();
+    ~AudioSystem();
 
     AudioSystem(const AudioSystem&) = delete;
     AudioSystem& operator=(const AudioSystem&) = delete;
@@ -89,8 +94,10 @@ private:
     void ProcessSource(Components::AudioSourceComponent* source, float* buffer, uint32 frameCount, uint32 channels, uint32 sampleRate);
     void RenderAudioBlock(uint32 frameCount, uint32 channels, uint32 sampleRate);
     void DetachMixerReferences(AudioMixer* mixer);
+    void UpdateStats();
 
 private:
+    mutable std::recursive_mutex m_stateMutex;
     std::unique_ptr<IAudioBackend> m_backend;
     AudioMixer m_masterMixer;
     AudioMixer* m_listenerReverbMixer = nullptr;

engine/include/XCEngine/Audio/IAudioBackend.h

@@ -1,13 +1,17 @@
 #pragma once
 
 #include "AudioConfig.h"
+#include <functional>
 #include <string>
+#include <vector>
 
 namespace XCEngine {
 namespace Audio {
 
 class IAudioBackend {
 public:
+    using RenderCallback = std::function<void(float*, uint32, uint32, uint32)>;
+
     virtual ~IAudioBackend() = default;
 
     virtual bool Initialize(const AudioConfig& config) = 0;
@@ -26,6 +30,8 @@ public:
 
     virtual void ProcessAudio(float* buffer, uint32 frameCount,
                              uint32 channels, uint32 sampleRate) = 0;
+    virtual bool UsesPullModel() const { return false; }
+    virtual void SetRenderCallback(RenderCallback callback) { (void)callback; }
 
     virtual bool IsRunning() const = 0;
     virtual AudioConfig GetConfig() const = 0;

engine/include/XCEngine/Audio/WindowsAudioBackend.h

@@ -39,6 +39,8 @@ public:
 
     void ProcessAudio(float* buffer, uint32 frameCount,
                      uint32 channels, uint32 sampleRate) override;
+    bool UsesPullModel() const override { return true; }
+    void SetRenderCallback(RenderCallback callback) override;
 
     bool IsRunning() const override { return m_isRunning.load(); }
     AudioConfig GetConfig() const override { return m_config; }
@@ -76,9 +78,6 @@ private:
     WAVEFORMATEX m_waveFormat = {};
     HWAVEOUT m_hWaveOut = nullptr;
 
-    std::vector<float> m_mixBuffer;
-    uint32 m_mixBufferSize = 0;
-
     std::vector<WAVEOUTCAPS> m_waveOutCaps;
     std::string m_deviceName;
     std::string m_requestedDeviceName;
@@ -86,13 +85,13 @@ private:
     static constexpr size_t BufferSize = 8192;
     std::vector<int16_t> m_audioBuffer1;
     std::vector<int16_t> m_audioBuffer2;
-    std::vector<float> m_pendingMixBuffer;
-    bool m_hasPendingMix = false;
+    std::vector<float> m_renderBuffer;
     bool m_buffer1Available = true;
     bool m_buffer2Available = true;
+    RenderCallback m_renderCallback;
 
     std::mutex m_bufferMutex;
-    std::condition_variable m_dataReadyCond;
+    std::condition_variable m_bufferReadyCond;
 
     WAVEHDR m_waveHeader1 = {};
     WAVEHDR m_waveHeader2 = {};