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change gain to 2 to match FFT
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CLAUDE.md
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CLAUDE.md
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**Test Results**: Basic API working, visualization shows 10 octaves with test data mapping
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#### Phase 2: Real CQT Processing (DEBUGGING)
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#### Phase 2: Real CQT Processing (COMPLETE)
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1. ✓ **Access raw audio buffer** from FFT capture system
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2. ✓ **Implement 4096-point FFT** for CQT (separate from main FFT)
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3. ✓ **Apply CQT kernels** to FFT output
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4. ✓ **Fix kernel initialization** - kernels are properly generated on startup
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5. **Add remaining API functions**: `cqts()`, `cqto()`, `cqtos()` (TODO)
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6. **Create comparison demo** showing FFT vs CQT side-by-side (TODO)
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5. ✓ **Debug and fix frequency mapping** - CQT now correctly detects frequencies
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6. **Add remaining API functions**: `cqts()`, `cqto()`, `cqtos()` (TODO)
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7. **Create comparison demo** showing FFT vs CQT side-by-side (TODO)
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**TEMPORARY CHANGE**: FFT_SIZE has been changed from 1024 to 2048 in fftdata.h to support CQT's 4096-point FFT requirement. This temporarily breaks FFT resolution (now 2048 bins instead of 1024) but allows CQT to function properly. This should be reverted once a separate audio buffer is implemented for CQT.
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···
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- NO scaling factor after FFT
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- Proper phase calculation: `2π * (f/fs) * (idx - N/2)`
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#### Phase 3: Optimization (If needed)
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1. Profile and identify bottlenecks
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2. Implement sparse kernel optimizations
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3. Consider frame-skipping for lower-end hardware
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**Final Status**:
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- CQT correctly detects frequencies (440 Hz → bin 54)
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- Good frequency selectivity (minimal spreading)
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- Kernels properly bandpass filtered
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- 20 Hz start preserved for electronic music sub-bass
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- Created test_cqt_spectrum_v2.lua with correct note display
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#### Phase 3: Next Steps
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1. Add remaining API functions: `cqts()`, `cqto()`, `cqtos()`
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2. Create separate audio buffer for CQT (restore FFT_SIZE to 1024)
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3. Create FFT vs CQT comparison demo
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4. Performance optimization if needed
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### Test Script Example
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```lua
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src/cqtdata.h
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src/cqtdata.h
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#define CQT_FFT_SIZE 4096 // Larger FFT for better sub-bass resolution
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// CQT frequency range
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#define CQT_MIN_FREQ 20.0f // Below piano's lowest A
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#define CQT_MIN_FREQ 20.0f // Sub-bass for electronic music
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#define CQT_MAX_FREQ 20480.0f // Nearest note to 20kHz
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// Smoothing parameters
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src/ext/cqt.c
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src/ext/cqt.c
···
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}
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// Calculate magnitude with gain boost
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cqtData[bin] = sqrt(real * real + imag * imag) * 4.0f; // Increased gain boost
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cqtData[bin] = sqrt(real * real + imag * imag) * 2.0f; // Match FFT gain factor
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// Check for NaN or Inf
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if (!isfinite(cqtData[bin]))