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Overview

IAudioSystem is the abstract interface for audio subsystems in ReXGlue. It provides dependency injection for different audio backends, with SDL as the primary implementation. Header: rex/system/interfaces/audio.h Namespace: rex::system

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Interface Methods

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Setup

virtual X_STATUS Setup(KernelState* kernel_state) = 0;
Initializes the audio system with the kernel state. Parameters:
  • kernel_state - Pointer to the kernel state manager
Returns: X_STATUS - Status code indicating success or failure

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Shutdown

virtual void Shutdown() = 0;
Cleanly shuts down the audio system and releases all resources.

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Concrete Implementation

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SDL Audio System

Class: rex::audio::sdl::SDLAudioSystem Header: rex/audio/sdl/sdl_audio_system.h SDL-based audio implementation providing cross-platform audio support. 
class SDLAudioSystem : public AudioSystem {
public:
  explicit SDLAudioSystem(runtime::Processor* processor);
  ~SDLAudioSystem() override;
  
  static bool IsAvailable() { return true; }
  
  static std::unique_ptr<AudioSystem> Create(runtime::Processor* processor);
  
  X_STATUS CreateDriver(
    size_t index,
    rex::thread::Semaphore* semaphore,
    AudioDriver** out_driver
  ) override;
  
  void DestroyDriver(AudioDriver* driver) override;
  
protected:
  void Initialize() override;
};

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Base AudioSystem Class

The SDL implementation extends rex::audio::AudioSystem, which provides: Key Members:
  • memory() - Access to memory subsystem
  • processor() - Access to CPU processor
  • xma_decoder() - XMA audio decoder instance
Key Methods:
  • Setup(kernel_state) - Initialize audio system
  • Shutdown() - Shutdown audio system
  • RegisterClient(callback, callback_arg, out_index) - Register audio client
  • UnregisterClient(index) - Unregister audio client
  • SubmitFrame(index, samples_ptr) - Submit audio frame for playback
  • Pause() / Resume() - Pause and resume audio playback
  • Save(stream) / Restore(stream) - Save and restore state
Constants:
  • kMaximumClientCount = 8 - Maximum number of simultaneous audio clients

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Example Usage

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Initializing SDL Audio System

#include <rex/audio/sdl/sdl_audio_system.h>
#include <rex/system/kernel_state.h>
#include <rex/runtime/processor.h>

using namespace rex;

// Check availability
if (!audio::sdl::SDLAudioSystem::IsAvailable()) {
  // Handle unavailable audio
  return;
}

// Create the audio system
auto audio = audio::sdl::SDLAudioSystem::Create(processor);

// Setup with kernel state
X_STATUS status = audio->Setup(kernel_state);

if (status != X_STATUS_SUCCESS) {
  // Handle error
}

// Use the audio system...

// Cleanup
audio->Shutdown();

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Registering an Audio Client

// Audio client callback
void AudioCallback(uint32_t arg) {
  // Handle audio callback
}

// Register client
size_t client_index;
X_STATUS status = audio->RegisterClient(
  reinterpret_cast<uint32_t>(&AudioCallback),
  user_data,
  &client_index
);

if (status == X_STATUS_SUCCESS) {
  // Submit audio frames
  audio->SubmitFrame(client_index, samples_ptr);
  
  // Later, unregister when done
  audio->UnregisterClient(client_index);
}

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Pausing and Resuming Audio

// Pause audio playback
if (!audio->is_paused()) {
  audio->Pause();
}

// Resume audio playback
if (audio->is_paused()) {
  audio->Resume();
}

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Using XMA Decoder

// Access XMA decoder for compressed audio
auto* xma = audio->xma_decoder();

// Use XMA decoder for Xbox 360 audio format decoding
// ...

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Audio Driver Interface

The audio system creates and manages AudioDriver instances for each client: 
// Create driver for client
AudioDriver* driver = nullptr;
auto semaphore = std::make_unique<rex::thread::Semaphore>();

X_STATUS status = audio->CreateDriver(
  client_index,
  semaphore.get(),
  &driver
);

if (status == X_STATUS_SUCCESS) {
  // Use driver...
  
  // Destroy when done
  audio->DestroyDriver(driver);
}

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Thread Safety

The audio system uses rex::thread::global_critical_region for thread-safe access to client management and audio frame submission.

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See Also

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