Added real RFFT functions (execute_real_forward, execute_real_inverse)
to fft.hpp/cpp. These implement the standard algorithm for real-valued
FFT using complex FFT of half size.
Updated buildFirFromMask to use real RFFTs matching the plugin's pipeline:
1. log(mask) → negate
2. forward real RFFT (opB)
3. EXP in-place
4. inverse real RFFT (opC)
5. Window
6. forward real RFFT (opD)
However, the real RFFT implementation makes results worse (10.377 dB vs
1.825 dB default). The plugin's real RFFT likely has subtle differences
(normalization, twiddle factors) that are not captured by the standard
algorithm.
The default path (no FIRCONV) remains the best approach with 1.825 dB
TOTAL error.
Future work: Reverse-engineer the plugin's exact real RFFT implementation
from disassembly (th1a90/th2180) to achieve bit-exact FIR construction.
- Fixed execute_inverse: removed conj bug, now uses positive twiddle only
- Added WOLA normalization factor (wola_sum/hop_ for Hann+hop=N/4)
- New detector model: floor(level) + bell_curve * boost, calibrated from
measured data (summary.md level sweep, 7 data points)
- Transcribed twiddle loader (FUN_18014ec20): Cody-Waite 4-level reduction
with minimax sin/cos polynomial, constants from Frida memory dump
- Added soothe_constants.hpp with extracted polynomial coefficients
- HARNESS parameters updated to match burst500_b1.rpp (depth=0.864)
Results: burst500.wav reduction now -5.8 dB vs Ref -6.8 dB (was -14.4 dB)
Matiq