sylph-decoder 7e12a3b1f9 re: the voice-region third chunk is a different structure from the BGM one
The port hit a 2+1 chunk signature on a resolved movie-voice region and asked
whether the bank-header explanation that closed HANDOFF Q10 also covers it,
rather than assuming it. It does not, and the discriminator is mechanical.

Disc-wide over the 95 English movie-voice regions the manifest binds:

  78 open with a bank header -- bank_header_len fires, 10240 B = 5 packets
     exactly, every time. That is the BGM case.
  17 open with a leading headerless stream -- bank_header_len is None, and all
     17 have length congruent to 1392 mod 2048, the disc s own derived data
     offset. No other residue occurs.
   0 begin at a RIFF.

Counting chunks does not discriminate: 8 bank-header regions also yield three
chunks. slb.rs already predicted this in its own doc comment -- the header
signature has "zero false positives on the 7993 mid-bank windows, where the
leading region IS real" -- and a voice region is a mid-bank window by
construction.

Also tested the obvious defence of dropping the leading chunk, that it is the
predecessor cue s audio: 0 of 17 leading spans lie inside any other resolved
region, 0.0 percent on every one. The test finds overlaps where they exist (16
overlapping pairs among the regions, 60 exactly-adjacent boundaries, 73 of 78
bank-header regions starting where another ends), so the zero is not the
instrument.

Left open, with reach: the census covers movie-voice regions only, and the same
stream carries the in-mission VOICE_D_* cues, which are not enumerated -- the
leading bytes plausibly belong to one of those. Could not be settled by
listening: no XMA1 decoder in this container, and sylpheed-cli audio info
reports these chunks as 16 channels / 4310 Hz / 2-bit, which is visibly wrong.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
2026-08-29 14:56:17 +00:00

Sylpheed

A clean-room reverse engineering and port project for Project Sylpheed: Arc of Deception (Xbox 360, 2007).

Three things live here, in one repository so that a change spanning them lands as one commit:

The decoders crates/sylpheed-formats — the disc's formats, read and verified disc-wide
The port port/ — a Godot 4 project, plus crates/sylpheed-export which converts a disc into the open asset tree it reads
The corpus docs/re/ — what has been reverse engineered, with its evidence, its retractions and its dead ends

You need your own copy of the game. No game content is in this repository and none ever will be. The exporter reads the disc you supply.

The oracle is the real game

sylpheed-cli and the Explorer are tools for verifying our decoding. They are hypotheses under test and they have been wrong. When something must be checked against the truth, the truth is the game running in Xenia Canary, captured — not any renderer of ours.

This is stated first because getting it backwards is the most expensive mistake this project has made.

Layout

crates/
  sylpheed-formats/   the decoders. Disc-wide verified; the corpus is its spec
  sylpheed-cli/       headless tools -- render a screen, dump a table, probe audio
  sylpheed-viewer/    the Explorer: a human's window onto the disc. STATIC data only
  sylpheed-export/    disc -> the open, moddable asset tree
port/                 the Godot 4 project. Reads open formats ONLY
authored/             decisions that are NOT on the disc, each with its reason
data/
  base/               generated by the exporter. Gitignored, never hand-edited
  mods/               drop-in overrides. Yours
docs/
  re/                 the corpus: findings, refutations, method traps
  game/               how the game is navigated -- menus, modals, flight
  port/               the port's mission, its handoff contract, modding rules
  agents/             how the agent team works together
tools/                capture harnesses, probes, the share tool
exchange/             transient inter-agent files. NOT in git
docker/               the agent containers

Where to start

Xenia Canary is a separate repository: it is a fork tracking upstream, and it carries our instrumentation.

Conventions

Confidence is per claim, never per document: CONFIRMED · 🟡 PROBABLE · HYPOTHESIS · REFUTED. A withdrawn result is kept with its reasoning rather than deleted — that is why the numbers here can be trusted.

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