corpus_structural.py drives render48k (48k/4096 structural chain) across the
full corpus with bridge-compare mode. Results: comb 6.12 vs bridge 10.15
(structural wins multiband already), res better, single-band worse; dual@500
constant -6.7dB q-independent over-cut exposes missing reduction saturation.
Param sweep (gamma x MULT, verified builds) confirms current optimum; curve
SHAPE is the gap -> Step 7 capture or bigkernel input re-examination.
- Add BandConfig A/B/gamma LUT compression (extracted from refs: A=-13.78dB, B=68.29dB, gamma=0.344)
- Add res^rp smoothing term for bridge-parity (RP0=0.0275, DRP=0.2159)
- Calibrate scale_factor to match bridge gain at tone bin (15.0 * 440.95 / 2048 = 3.23)
- Structural 48k: -26.81 dB vs ref -27.23 dB (err +0.426 dB)
- Bridge baseline: intact (0.000 dB degradation)
- All module checks PASS (fn529fe0, exp2, twin, tables, leveltrack, levelpath, fftconv)
- render48k: resample 44100→48000, process via SpectralProcessor(4096,1024,48000),
resample 44100, write 24-bit stereo WAV
- FramedDetector: structural chain (fn529fe0 sequence) runs on 48000/4096 grid,
bridge path unchanged for 44100/2048
- Structural chain: scale→IIR1→copy→IIR2→mirror→blend→exp2→combine→warp→dry/wet
using live tables (kIIR_A1/B1, kIIR_A2/B2, kBand768, kWarp, kRTAtt/kRTRel)
- Bridge baseline intact (0.000 dB degradation)
- 48k tone test: -20.73 dB vs ref -27.23 dB (6.5 dB error, scale factor not yet
calibrated to match bridge domain)
12094f8 replaced the empirical Pchip LUT with the parametric
linear form (CAP_A_LEVEL=-24/B=28/gamma=1). With gamma=1 the
parametric form reduces to identity on xv=log10(am/res), which
breaks the whole mask chain (t1kq fc-scan err jumps to ~7.9 dB).
Re-instating lut_pchip restores the honest baseline:
t1kq mean|err| 0.226 dB (was 7.9). Confirms NOTES_LEVEL F1
closure: no parametric LUT set beats Pchip at fixed bridge
params; the structural A/B/gamma (level-path ctx+0x188) is the
only real path to bytes, not this parametric substitution.
Full dsp/ check sweep green. fft.cpp = numerical radix-2 (std::cos) not bit-exact
0x140a70; split-radix butterfly + plan-gen giant + sin-table loader remain (multi-week
P3). Required only for FFT-conv byte-parity, not for the bridge renderer.
Extracted the 8x16 irrational tables + lead-in -708.4xx series from soothe_mem.bin
into exp2_tables.{hpp,cpp} (P3 bit-exact inputs). exp2_dsp = numerically-correct
double exp2 matching std::exp2 (wiring fallback; NOT bit-exact yet — the plugin
body has special subnormal/overflow branches and a vfmadd213sd poly not yet 1:1).
exp2_check: 2e6-grid PASS (0 cells >1e-13).
Wiring FFT-conv step5 (mask*=win) gives mean 5.2, combine/acc (att/rel from kRTAtt/
kRTRel) gives 4.7 vs base 0.75-0.80 on representative subset. Both belong to the
exp2(mask) structural chain (blend 0.8 + bigkernel) NOT the fitted bridge final-gain.
No code change; bridge + Pchip stays canonical (0.773).
All previously-derived parametric LUT forms (u563a60 A=-13.78/68.29/0.344, lut5/
lut4 gamma-LUT, power-law, linear 0.483/0.717, real extracted points) tested on the
full 59-case honest 24-bit metric within one fixed bridge pipeline. None beat the
committed Pchip (0.773; worst powerlaw 6.8). F1 closed: parametric curve production
was already done, none accepted; structural A/B/gamma from ctx+0x188 remains the only
path to bytes (blocked on level-path object live capture).
Two test RPPs (res_only1_500 4s, t1kq_only1_1000 6s) rendered twice each via
reaper -nosplash CLI. Data chunks identical across runs AND byte-identical to the
committed reference wavs. Whole-file differs only in the bext render-timestamp.
=> bit-exact (bytes) is REACHABLE; the per-run-dithrandization blocker is closed.
Next: exact structural chain + kernels + internal 48000/4096 geometry + live A/B/gamma.
Matiq