init

runtime/include/audio_backend.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <mutex>
+#include <vector>
+
+#include <SDL3/SDL_audio.h>
+
+class AudioBackend {
+public:
+    static AudioBackend& Instance();
+
+    bool Init(uint32_t sampleRate, uint32_t channels);
+    void Shutdown();
+
+    // Wii AI DMA frames are big-endian and ordered right, left. SDL expects
+    // native-endian interleaved left, right samples.
+    bool PushWiiAiSamplesBE16(const uint8_t* data, size_t bytes);
+    bool PushSamplesLE16(const int16_t* samples, size_t sampleCount);
+
+    // Applied to the final host output, covering both AX and direct AI DMA.
+    void SetMasterVolume(float volume);
+    void SetMuted(bool muted);
+
+private:
+    AudioBackend() = default;
+    ~AudioBackend() = default;
+    AudioBackend(const AudioBackend&) = delete;
+    AudioBackend& operator=(const AudioBackend&) = delete;
+
+    bool EnsureInitializedLocked(uint32_t sampleRate, uint32_t channels);
+    bool QueueHasCapacityLocked(int incomingBytes);
+    uint32_t QueueLimitBytesLocked() const;
+    float EffectiveGainLocked() const;
+    void ApplyGainLocked();
+
+    mutable std::mutex m_mutex;
+    SDL_AudioStream* m_stream = nullptr;
+    SDL_AudioSpec m_spec{};
+    uint32_t m_sampleRate = 0;
+    uint32_t m_channels = 0;
+    bool m_initialized = false;
+    float m_masterVolume = 1.0f;
+    bool m_muted = false;
+    bool m_reportedDroppedBlock = false;
+    std::vector<int16_t> m_convertBuffer;
+};