wasm_audio.h

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// wasm_audio.h - WebAudio Backend Implementation for WASM/Emscripten
// Provides audio output for SNES emulator using browser's WebAudio API
 
#ifndef YAZE_APP_EMU_PLATFORM_WASM_WASM_AUDIO_H
#define YAZE_APP_EMU_PLATFORM_WASM_WASM_AUDIO_H
 
#ifdef __EMSCRIPTEN__
 
#include <atomic>
#include <cstdint>
#include <memory>
#include <mutex>
#include <queue>
#include <string>
#include <vector>
 
#include "app/emu/audio/audio_backend.h"
 
namespace yaze {
namespace emu {
namespace audio {
 
class WasmAudioBackend : public IAudioBackend {
 public:
  WasmAudioBackend();
  ~WasmAudioBackend() override;
 
  // Initialization
  bool Initialize(const AudioConfig& config) override;
  void Shutdown() override;
 
  // Playback control
  void Play() override;
  void Pause() override;
  void Stop() override;
  void Clear() override;
 
  // Audio data submission
  bool QueueSamples(const int16_t* samples, int num_samples) override;
  bool QueueSamples(const float* samples, int num_samples) override;
  bool QueueSamplesNative(const int16_t* samples, int frames_per_channel,
                          int channels, int native_rate) override;
 
  // Status queries
  AudioStatus GetStatus() const override;
  bool IsInitialized() const override;
  AudioConfig GetConfig() const override;
 
  // Volume control (0.0 to 1.0)
  void SetVolume(float volume) override;
  float GetVolume() const override;
 
  // Audio stream resampling support
  void SetAudioStreamResampling(bool enable, int native_rate,
                                int channels) override;
  bool SupportsAudioStream() const override { return true; }
 
  // Backend identification
  std::string GetBackendName() const override { return "WebAudio"; }
 
  // WASM-specific: Handle user interaction for autoplay policy
  void HandleUserInteraction();
 
  // WASM-specific: Check if audio context is suspended due to autoplay
  bool IsContextSuspended() const;
 
 private:
  // Internal buffer management
  struct AudioBuffer {
    std::vector<float> samples;
    int sample_count;
    int channels;
  };
 
  // Helper functions
  void ProcessAudioQueue();
  bool ConvertToFloat32(const int16_t* input, float* output, int num_samples);
  void ApplyVolumeToBuffer(float* buffer, int num_samples);
 
  // JavaScript audio context handle (opaque pointer)
  void* audio_context_ = nullptr;
 
  // JavaScript script processor node handle
  void* script_processor_ = nullptr;
 
  // Configuration
  AudioConfig config_;
 
  // State management
  std::atomic<bool> initialized_{false};
  std::atomic<bool> playing_{false};
  std::atomic<bool> context_suspended_{true};
  std::atomic<float> volume_{1.0f};
 
  // Sample queue for buffering
  std::mutex queue_mutex_;
  std::queue<AudioBuffer> sample_queue_;
  std::atomic<size_t> queued_samples_{0};
 
  // Resampling configuration
  bool resampling_enabled_ = false;
  int native_rate_ = 32000;  // SNES native rate
  int native_channels_ = 2;
 
  // Working buffers
  std::vector<float> conversion_buffer_;
  std::vector<float> resampling_buffer_;
 
  // Performance metrics
  mutable std::atomic<bool> has_underrun_{false};
  std::atomic<size_t> total_samples_played_{0};
 
  // Buffer size configuration
  static constexpr int kDefaultBufferSize = 2048;
  static constexpr int kMaxQueuedBuffers = 16;
  static constexpr float kInt16ToFloat = 1.0f / 32768.0f;
};
 
}  // namespace audio
}  // namespace emu
}  // namespace yaze
 
#endif  // __EMSCRIPTEN__
 
#endif  // YAZE_APP_EMU_PLATFORM_WASM_WASM_AUDIO_H