WASM Platform-Specific Code

This directory contains WebAssembly/Emscripten-specific implementations for the yaze emulator.

Files

Audio Backend (wasm_audio.h / wasm_audio.cc)

The WASM audio backend provides WebAudio API integration for playing SNES audio in web browsers.

Features

• WebAudio context management with browser autoplay policy handling
• ScriptProcessorNode-based audio playback (compatible with all browsers)
• Sample format conversion (16-bit PCM to Float32)
• Volume control via GainNode
• Audio queue management with buffer limiting
• Automatic context suspension/resumption

Technical Details

• Sample Rate: Configurable, defaults to browser's native rate
• Input Format: 16-bit stereo PCM (SNES native format)
• Output Format: Float32 (WebAudio requirement)
• Buffer Management: Queue-based with automatic overflow protection
• Latency: Interactive mode for lower latency

Browser Compatibility

• Handles browser autoplay restrictions
• Call HandleUserInteraction() on user events to resume suspended contexts
• Check IsContextSuspended() to determine if user interaction is needed

Usage

// Create backend via factory
auto backend = AudioBackendFactory::Create(BackendType::WASM);
 
// Or create directly
WasmAudioBackend audio;
 
// Initialize with config
AudioConfig config;
config.sample_rate = 48000;
config.channels = 2;
config.buffer_frames = 2048;
audio.Initialize(config);
 
// Queue audio samples
int16_t samples[4096];
audio.QueueSamples(samples, 4096);
 
// Start playback
audio.Play();
 
// Handle browser autoplay policy
if (audio.IsContextSuspended()) {
    // On user click/interaction:
    audio.HandleUserInteraction();
}

Build Configuration

The WASM audio backend is automatically included when building for Emscripten:

if(EMSCRIPTEN)
  list(APPEND YAZE_APP_EMU_SRC app/emu/platform/wasm/wasm_audio.cc)
endif()

Implementation Notes

• Uses EM_JS macros for JavaScript integration
• clang-format off is used to prevent formatting issues with EM_JS blocks
• Audio context and processor are managed via global JavaScript objects
• Sample data is copied from WASM memory to JavaScript arrays

Future Improvements

• AudioWorklet support (when browser support is more widespread)
• Dynamic resampling for native SNES rate (32kHz)
• Latency optimization
• WebAudio analyzer node for visualization