# prd.md — Project Requirements Document

## 1. Project Overview

**Name**: `soothe2-re` — bit-exact reverse engineering of **oeksound soothe2** (VST3, Windows x64)

**Goal**: Reproduce the plugin's DSP core (level detector, mask computation, filter application) in C++17, byte-for-byte identical to the native binary.

**Status**: ~95% decompiled. Current best metric: **0.341 dB TOTAL** (structural 48k chain). Target: **<0.05 dB** (bit-exact gate).

**Golden rule**: Every parameter must have a source (decomp address / live table). Empirical fits must be flagged `EMPIRICAL`.

---

## 2. Repository Structure

```
re-tools/
├── prd.md                    ← THIS FILE (project overview)
├── README.md                 ← TOTAL metric source (single source of truth)
├── AGENTS.md                 ← runbook: build, env flags, tooling hazard
├── BITEXACT_PLAN.md          ← path to byte-exact (3 steps, criteria)
├── roadmap.md                ← historical B-phase log (archived)
│
├── dsp/                      ← C++17 DSP reconstruction (THE CANON)
│   ├── framed_model.{cpp,hpp} ← MAIN: mask-apply chain (empirical bridge)
│   ├── render48k.cpp          ← 48k/4096 structural pipeline (resample→chain→resample)
│   ├── spectral.{cpp,hpp}     ← STFT/ISTFT processor + FIR builder
│   ├── fn529fe0.{cpp,hpp}     ← structural chain 9–19 (FUN_180529fe0)
│   ├── fnfaith.{cpp,hpp}      ← faithful detector cascade (BLOCKMAP transcription)
│   ├── fft{,_plan,_stage}.cpp/hpp ← FFT engine (canonical + RFFT bit-exact)
│   ├── twin.{cpp,hpp}         ← twin resonator (FUN_180535880, float-parity)
│   ├── rt_mask_tables.{hpp,.cpp} ← live IIR A/B coefficients (385K)
│   ├── rt_weights.{hpp,.cpp}  ← live kWarp/kBand768 tables (44K)
│   ├── fftconv.{cpp,hpp}      ← FFT convolution FIR application
│   ├── vlog.{cpp,hpp}         ← fast log2 approximation
│   ├── exp2.{cpp,_tables.cpp,hpp} ← fast exp2 approximation
│   ├── levelpath.{cpp,hpp}    ← level-curve path (xv = log10(am/res))
│   ├── freqpath.{cpp,hpp}     ← frequency-axis warp/freq-domain helpers
│   ├── leveltrack.{cpp,hpp,hpp} ← envelope follower (attack/release tables)
│   ├── log2_ln.{cpp,hpp}      ← log/ln utilities
│   ├── filter.{cpp,hpp}       ← detection kernel (legacy)
│   ├── detect.{cpp,hpp}       ← detector front-end (legacy)
│   ├── phase_table.{cpp,hpp}  ← phase table for FFT
│   ├── ms.hpp                 ← mid-side helpers
│   ├── params.hpp             ← parameter struct
│   ├── rotor_kernel.hpp       ← rotor transform kernel
│   ├── rt_div_tables.hpp      ← division tables
│   ├── soothe_constants.hpp   ← decoded constants
│   ├── cody_waite.hpp         ← Cody-Waite argument reduction
│   ├── twiddle_{builder,loader}.cpp/hpp ← FFT twiddle factors
│   ├── dsp_ctx.hpp            ← DSP context layout
│   ├── framed_test.cpp        ← CLI bridge renderer (44.1k)
│   ├── harness.cpp           ← legacy harness
│   ├── *_check.cpp            ← bit-exact unit test targets
│   └── CMakeLists.txt
│
├── scripts/
│   ├── corpus.py              ← bridge regression harness (62 cases, --compare)
│   ├── corpus_structural.py   ← structural chain harness (--vs-bridge)
│   ├── rendersnap2.py         ← RENDER_FILE stopper (reads from .rpp)
│   ├── campaign.py            ← parameter sweep cell (~8 min)
│   ├── cascade_sim.py         ← numpy step 9–19 simulator
│   ├── disasm_func.py         ← capstone disasm with RIP constants
│   ├── iat_name.py            ← runtime import resolution
│   ├── wine_{chain,stage,ptrace}_trace.py ← ptrace-based live trace
│   ├── dump_dispatch.py       ← table/state dumper
│   ├── probe_{states,mem}.py  ← live state/memory probes
│   ├── hunt2.py               ← ctx-instance hunter
│   ├── scan_{pairs,lutsub}.py ← memory diagnostics
│   ├── fit_vlaw_{params,by_group}.py ← VLAW law calibration
│   ├── lawfit22r.py           ← law fitting (VLAW α/β/c)
│   ├── mk_{dist,far,multi6}.py ← RPP generators
│   └── render_parity.py       ← model-vs-render comparison
│
├── handoff/
│   ├── NOTES_LEVEL.md         ← live journal (head: 24mm5+)
│   ├── NOTES_LEVEL_INDEX.md   ← journal index by date/topic
│   ├── BLOCKMAP_529fe0.md     ← FUN_180529fe0 method map (53K)
│   ├── NOTES_TWIN.md          ← twin reference
│   ├── NOTES_CAPTURE.md       ← live-capture protocol
│   ├── NEXT_PROMPT.md         ← entry point for new sessions
│   ├── SESSION_HANDOFF.md     ← handoff template
│   ├── archive/               ← historical NOTES_LEVEL_*.md, SESSION_HANDOFF_*.md
│   ├── nls_dasm/              ← 183 disassembly files (.dis, .bin)
│   ├── phase1/                ← phase-1 outputs
│   ├── rt*.npy                ← captured runtime tables (48k/44.1k)
│   └── *.py                   ← emit/extract/joint scripts
│
├── *.java                     ← Ghidra scripts (DumpFuns, ImportRtti…)
├── *.{bin,npz,npy,json,txt}   ← datasets, dumps, LUTs (mostly outside git)
└── soothe-bt/                 ← test corpus (~600 renders, outside git)
```

---

## 3. Build System

**Generator**: CMake 3.10+, C++17, GCC/Clang with `-O3 -march=native`.

```cmake
# Key targets
soothe2_dsp          # shared library (all dsp/*.cpp)
framed_test          # CLI bridge renderer (44.1k)
render48k            # structural renderer (48k/48000)
twin_check           # float-parity unit test
tables_check         # live-table verification
fftconv_check        # FIR convolution check
vlog_check           # fast log2 check
leveltrack_check     # envelope follower check
levelpath_check      # level-curve path check
exp2_check           # fast exp2 check
fn529fe0_check       # structural chain check
soothe2_harness      # legacy harness
```

**External deps**: `libsamplerate` (render48k only), `pthread`.

**Tooling hazard**: CMake skips rebuild when source modified within same second. Protocol: `touch` source before build + verify binary mtime.

---

## 4. DSP Architecture

### 4.1 Signal Flow (current canon: structural `render48k`)

```
Host 44.1k → resample → 48k → [per-channel processing] → resample → 44.1k Host
                                              ↓
                                    ┌─────────────────────┐
                                    │  FramedDetector      │
                                    │  (per 4096 block)     │
                                    │                      │
                                    │  am[] ← envelope     │
                                    │  res[] ← twin resp   │
                                    │         ↓            │
                                    │  lvl_raw = am/res·sf │
                                    │         ↓            │
                                    │  [RT_VLAW=1]:        │
                                    │    cut = α·ln1p(L/β) │
                                    │         +c [+Δ]      │
                                    │    mask = 10^(-cut/20)│
                                    │         ↓            │
                                    │  warp: mask *=       │
                                    │    kBand·kWarp·res^rp│
                                    │         ↓            │
                                    │  IIR3 ×2 (bidir)     │
                                    │         ↓            │
                                    │  mask_out → multiply │
                                    │  spectrum[k] *= mask │
                                    └─────────────────────┘
```

### 4.2 Dual Render Path

| Path | File | Grid | Use |
|------|------|------|-----|
| Bridge | `framed_model.cpp` | 44.1k/2048 | Legacy, TOTAL 1.594 |
| Structural | `render48k.cpp` | 48k/4096 | Canon, TOTAL 0.341 |

**Dual-solution env set**: `RT_VLAW=1 RT_SYN=1 RT_NOWARP=1 RT_NOIIR3=1 RT_IIR12=0`

### 4.3 Key Modules

| Module | Responsibility |
|--------|---------------|
| `FramedDetector` | Per-band, per-frame mask computation. Holds `am_`, `res_`, `track_` state. |
| `SpectralProcessor` | STFT/ISTFT, OLA overlap-add, FIR application modes. |
| `fn529fe0` | Structural chain 9–19 (steps 9–19 of FUN_180529fe0): scale→IIR1→IIR2→blend→combine→warp→IIR3→dry/wet. |
| `fnfaith` | Faithful detector cascade transcription (BLOCKMAP). |
| `twin` | Twin resonator `|2B/A|` — frequency response per band. |
| `rt_mask_tables` | Live IIR A/B coefficients (kIIR_A1/A2/A3, kIIR_B1/B2/B3, kRTAtt, kRTRel). |
| `rt_weights` | Live warp weights (kBand768, kWarp). |
| `fft` | Bit-exact RFFT (th1a90/th2180) with `buf548`/`mask598` tables. |
| `fftconv` | FFT-based convolution for FIR application modes. |
| `vlog`/`exp2` | Fast polynomial approximations matching plugin精度. |
| `leveltrack` | Envelope follower with per-bin attack/release tables. |

### 4.4 Detector Cascade (529c60)

```
complex_spectrum × twin_response → |z|
  → Haar smooth [0.25,0.5,0.25] × n_iters
  → peak = max(curve)
  → sin_peak = sin(param·30 − 90) · 0.115129 · peak
  → curve = max(curve, sin_peak)
  → w = -log10(pow(50, ratio·0.001) · ratio·0.001)
  → acc = acc·w + curve·(1-w)
  → bands_curve = acc
```

---

## 5. Environment Flags (experiment control)

| Flag | Effect |
|------|--------|
| `RT_VLAW=1` | Two-stage law: `mask = 10^(−(α·ln1p(lvl/β)+c)/20)` |
| `RT_SYN=1` | STFT without synthesis window (plugin's actual layer) |
| `RT_WIN=0/1/2` | Analysis window: sym-Hann / periodic / rect |
| `RT_NOWARP=1` | Skip warp modulation |
| `RT_NOIIR3=1` | Skip IIR3 ×2 |
| `RT_IIR12=0` | Skip freq-domain IIR1/2 (critical with VLAW) |
| `RT_DUMP_BIN=<f>` | Dump tract binary (frame `RT_DUMP_FRAME`) |
| `RT_VDBG=1` | Print VLAW computations to stderr |
| `RT_FAITHFUL=1` | Use faithful chain (`fnfaith.cpp`) |
| `RT_FIRCONV=1/3` | FIR application mode (1=complex-mul, 3=`1.019·mask^1.8345`) |
| `RT_ENV=live` | Live envelope from kRTAtt/kRTRel tables |
| `RT_KMAP=1` | k-mapping correction (twin/am scaling) |
| `RT_EQ=1` | Pre-detector EQ bell |
| `RT_LUT_OFF=1` | Skip LUT transform |
| `RT_LUT_A/B/G/M` | LUT parameters (A=-24, B=28, gamma=1, mult=4.2) |

---

## 6. Test Corpus & Metrics

**Location**: `/home/m/soothe-bt/` (~600 renders, outside git).

**Key sets**:

| Prefix | Content |
|--------|---------|
| `tone1kq_*` | Single tone, fc-scan, quiet (-18 dBFS) |
| `tone1k_*` | Single tone, fc-scan, loud (0 dBFS) |
| `dual_b1q_*` | Two tones (500+2000), q 0.1…10 |
| `al_*` | Level sweep (fc=1000) |
| `comb_*` | 4-band multiband |
| `burst500_b1` | Primary reference (burst 500 Hz) |

**Metric** (Goertzel steady-state):
```python
err_dB = 20·log1₀( ta(out,1000) / ta(ref,1000) )
# trimmed to last 75% of input, matched to plugin render length
```

**Regression guards**:
```bash
python3 scripts/corpus.py                                    # bridge + guard
python3 scripts/corpus_structural.py                         # structural chain
python3 scripts/corpus.py --compare scripts/baseline_bridge.json --tol 0.25
python3 scripts/corpus_structural.py --vs-bridge scripts/baseline_bridge.json
```

---

## 7. Current Status (2026-08-29, 24mm14)

| Group | Bridge | Structural (VLAW) |
|-------|--------|-------------------|
| t1kq (fc-scan) | 0.226 | 0.426–0.852 |
| t1k (loud) | 1.801 | 0.577–0.930 |
| al (level) | 0.638 | 0.090–0.804 |
| res | 0.628 | 0.395 |
| dual (q-sweep) | 0.726 | **0.193** ✓ |
| comb (4-band) | 10.149 | 2.678–4.335 |
| **TOTAL** | **1.594** | **0.341** |

**Decoded**:
- Layer: STFT without synthesis window, per-bin mask multiply
- Law: `mask = 10^(−(α·ln1p(lvl/β)+c)/20)` with content-aware Δ
- FIR: `exp(0.984·ln(raw))` + Hann + normalize → bit-exact RFFT to df0

**Open gaps**:
1. **Chain 9–19** (priority #1): Dataflow decoded, bigkernel bodies known, I/O format unknown. Target: <0.05.
2. **k-mapping** (priority #2): twin/am scaling `k(q≥2)=0.403`.
3. **Δ second-peak rule** (priority #3): Content-dependent gain, requires live-dump.

---

## 8. Reference Documents

| Doc | Content |
|-----|---------|
| `README.md` | TOTAL metric, reproduction steps |
| `AGENTS.md` | Build commands, env flags, hazard, corpus format |
| `BITEXACT_PLAN.md` | 3-step plan to byte-exact |
| `handoff/BLOCKMAP_529fe0.md` | Method map for FUN_180529fe0 |
| `handoff/NOTES_LEVEL.md` | Live working journal |
| `handoff/NOTES_LEVEL_INDEX.md` | Journal index |
| `handoff/NOTES_TWIN.md` | Twin resonator reference |
| `handoff/NOTES_CAPTURE.md` | Live-capture protocol |
| `handoff/nls_dasm/` | 183 disassembly files |

---

## 9. Reproduction & Development Protocol

1. Install soothe2 VST3 (Windows) under yabridge → `dump_soothe.py` → `soothe_mem.bin`
2. Ghidra headless: `analyzeHeadless <proj> soothe_x64 -process soothe_mem.bin -noanalysis -postScript <X>.java`
3. Renders: `sweep.py` → `.rpp`, `reaper -renderproject` → `.wav`
4. Analysis: `render_parity.py` / `corpus.py`
5. After C++ edit: `touch` source → `cmake --build dsp/build --target framed_test` → run corpus guards