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Implemented WavDumpBackend that renders audio to .wav file instead of
playing on audio device. Useful for debugging audio synthesis, tempo
scaling, and tracker output without needing real-time playback.
New Files:
- src/audio/wav_dump_backend.h: WAV dump backend interface
- src/audio/wav_dump_backend.cc: Implementation with WAV file writing
Features:
- Command line option: --dump_wav [filename]
- Default output: audio_dump.wav
- Format: 16-bit PCM, mono, 32kHz
- Duration: 60 seconds (configurable in code)
- Progress indicator during rendering
- Properly writes WAV header (RIFF format)
Integration (src/main.cc):
- Added --dump_wav command line parsing
- Optional filename parameter
- Sets WavDumpBackend before audio_init()
- Skips main loop in WAV dump mode (just render and exit)
- Zero size impact (all code under !STRIP_ALL)
Usage:
./demo64k --dump_wav # outputs audio_dump.wav
./demo64k --dump_wav my_audio.wav # custom filename
Technical Details:
- Uses AudioBackend interface (from Task #51)
- Calls synth_render() in loop to capture audio
- Converts float samples to int16_t for WAV format
- Updates WAV header with final sample count on shutdown
- Renders 60s worth of audio (1,920,000 samples @ 32kHz)
Test Results:
✓ All 16 tests passing (100%)
✓ Successfully renders 3.7 MB WAV file
✓ File verified as valid RIFF WAVE format
✓ Playback in audio players confirmed
Perfect for:
- Debugging tempo scaling behavior
- Verifying tracker pattern timing
- Analyzing audio output offline
- Creating reference audio for tests
handoff(Claude): WAV dump debugging feature complete
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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