re(media): the disc ships movies in TWO audio profiles, and 28 of them are 5.1

Probed all 97 movies. 28 are wmapro 48 kHz 6-channel 5.1 -- ADV.wmv and every
S*.wmv story cutscene; the other 69 are wmav2 48 kHz stereo, every RT*.wmv and
hokyu_*.wmv. The split is cinematics vs in-mission radio chatter.

Both movies the menu milestone needs, ADV.wmv (the boot/attract intro) and
S00A.wmv (the new-game intro), are in the SURROUND group.

Why it matters: one ffmpeg command over dat/movie/ produces two different kinds
of result and records neither. The 69 stereo files pass through unchanged; the 28
surround files get downmixed 5.1 -> stereo by ffmpeg's DEFAULT matrix, folding
centre-channel dialogue into L/R at a weighting nobody chose and which is not
stable across ffmpeg versions. That is a content decision inherited by accident,
so it should be stated explicitly and recorded beside the command.

Credit where due: found by the human while checking a transcode, verified
independently here and widened from one file to the whole disc.

Two METHOD entries from the same episode, both about measurement rather than
format: don't probe a file another process is still writing (a half-written
transcode reported 33 s against a 137 s source, no error, nearly a filed bug),
and a difference-signal RMS is meaningless before cross-correlation alignment
(-34.2 dB against a -25.3 dB source looks like failure and is inconclusive).

docs/re/METHOD.md

@@ -880,3 +880,19 @@ agent's loop prompt, i.e. nowhere durable. See [`README.md`](README.md) for the
   stuck before it was timed. If the change under test is not in the mesh path,
   `build-reborn t -p <crate>` scopes around it — note that `build-reborn test`
   itself passes `--workspace` and will ignore a `-p`.
+
+* **Never measure a file another process is still writing.** `ffprobe` on a
+  half-written transcode reported 33 s against a 137 s source — the shape of
+  catastrophic truncation, with no error and no warning, and it nearly became a
+  filed bug. The tell was the mtime and a climbing packet count, not anything in
+  the tool's output. Before comparing an artifact you did not produce, check that
+  whoever produces it has finished; across two agents sharing a repo this is a
+  race, not an edge case.
+
+* **A difference-signal RMS means nothing until the two are aligned.** Comparing a
+  transcode against its source gave source RMS −25.3 dB and difference RMS
+  −34.2 dB — only ~9 dB down, which looks like a failure. It is inconclusive: a
+  one-sample offset makes the difference nearly as loud as the source. Any such
+  test needs cross-correlation to align first and an agreed downmix, and only then
+  is a pass mark like ">40 dB down" meaningful. Reporting the 9 dB as a result
+  would have been a confident wrong number.

docs/re/data/movie-audio-layouts.csv

@@ -0,0 +1,97 @@
+ADV.wmv,wmapro,48000,6,5.1
+RT01A.wmv,wmav2,48000,2,unknown
+RT01B.wmv,wmav2,48000,2,unknown
+RT01C_1.wmv,wmav2,48000,2,unknown
+RT01C_2.wmv,wmav2,48000,2,unknown
+RT02A.wmv,wmav2,48000,2,unknown
+RT02B.wmv,wmav2,48000,2,unknown
+RT02C.wmv,wmav2,48000,2,unknown
+RT02D_1.wmv,wmav2,48000,2,unknown
+RT02D_2.wmv,wmav2,48000,2,unknown
+RT03A.wmv,wmav2,48000,2,unknown
+RT03B.wmv,wmav2,48000,2,unknown
+RT03C.wmv,wmav2,48000,2,unknown
+RT03D.wmv,wmav2,48000,2,unknown
+RT04A.wmv,wmav2,48000,2,unknown
+RT04B.wmv,wmav2,48000,2,unknown
+RT05A.wmv,wmav2,48000,2,unknown
+RT05B.wmv,wmav2,48000,2,unknown
+RT05C.wmv,wmav2,48000,2,unknown
+RT06A.wmv,wmav2,48000,2,unknown
+RT06B.wmv,wmav2,48000,2,unknown
+RT06C.wmv,wmav2,48000,2,unknown
+RT06D.wmv,wmav2,48000,2,unknown
+RT07A.wmv,wmav2,48000,2,unknown
+RT07B.wmv,wmav2,48000,2,unknown
+RT07C.wmv,wmav2,48000,2,unknown
+RT08A.wmv,wmav2,48000,2,unknown
+RT08B.wmv,wmav2,48000,2,unknown
+RT08C.wmv,wmav2,48000,2,unknown
+RT09A.wmv,wmav2,48000,2,unknown
+RT09B.wmv,wmav2,48000,2,unknown
+RT09C.wmv,wmav2,48000,2,unknown
+RT09D.wmv,wmav2,48000,2,unknown
+RT10A.wmv,wmav2,48000,2,unknown
+RT10B.wmv,wmav2,48000,2,unknown
+RT11A.wmv,wmav2,48000,2,unknown
+RT11B.wmv,wmav2,48000,2,unknown
+RT11C.wmv,wmav2,48000,2,unknown
+RT12A.wmv,wmav2,48000,2,unknown
+RT12B_1.wmv,wmav2,48000,2,unknown
+RT12B_2.wmv,wmav2,48000,2,unknown
+RT13A.wmv,wmav2,48000,2,unknown
+RT13B_1.wmv,wmav2,48000,2,unknown
+RT13B_2.wmv,wmav2,48000,2,unknown
+RT14A.wmv,wmav2,48000,2,unknown
+RT14B.wmv,wmav2,48000,2,unknown
+RT14C.wmv,wmav2,48000,2,unknown
+RT15A.wmv,wmav2,48000,2,unknown
+RT15B.wmv,wmav2,48000,2,unknown
+RT15C.wmv,wmav2,48000,2,unknown
+RT16C.wmv,wmav2,48000,2,unknown
+S00A.wmv,wmapro,48000,6,5.1
+S01A.wmv,wmapro,48000,6,5.1
+S02A.wmv,wmapro,48000,6,5.1
+S02B.wmv,wmapro,48000,6,5.1
+S02C.wmv,wmapro,48000,6,5.1
+S03A.wmv,wmapro,48000,6,5.1
+S04A.wmv,wmapro,48000,6,5.1
+S04B.wmv,wmapro,48000,6,5.1
+S05A.wmv,wmapro,48000,6,5.1
+S06A.wmv,wmapro,48000,6,5.1
+S06B.wmv,wmapro,48000,6,5.1
+S07A.wmv,wmapro,48000,6,5.1
+S07B.wmv,wmapro,48000,6,5.1
+S09B.wmv,wmapro,48000,6,5.1
+S10B.wmv,wmapro,48000,6,5.1
+S11A.wmv,wmapro,48000,6,5.1
+S11C.wmv,wmapro,48000,6,5.1
+S12A.wmv,wmapro,48000,6,5.1
+S12B.wmv,wmapro,48000,6,5.1
+S12C.wmv,wmapro,48000,6,5.1
+S13A.wmv,wmapro,48000,6,5.1
+S13B.wmv,wmapro,48000,6,5.1
+S14A.wmv,wmapro,48000,6,5.1
+S15A.wmv,wmapro,48000,6,5.1
+S15B.wmv,wmapro,48000,6,5.1
+S15C.wmv,wmapro,48000,6,5.1
+S16A.wmv,wmapro,48000,6,5.1
+hokyu_DS_s02A.wmv,wmav2,48000,2,unknown
+hokyu_DS_s07A.wmv,wmav2,48000,2,unknown
+hokyu_DS_s07H.wmv,wmav2,48000,2,unknown
+hokyu_DS_s08A.wmv,wmav2,48000,2,unknown
+hokyu_DS_s13A.wmv,wmav2,48000,2,unknown
+hokyu_DS_s14H.wmv,wmav2,48000,2,unknown
+hokyu_LS_s02A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s02H.wmv,wmav2,48000,2,unknown
+hokyu_LS_s03A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s03H.wmv,wmav2,48000,2,unknown
+hokyu_LS_s06A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s06H.wmv,wmav2,48000,2,unknown
+hokyu_LS_s09A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s09H.wmv,wmav2,48000,2,unknown
+hokyu_LS_s11A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s14A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s15A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s24A.wmv,wmav2,48000,2,unknown
+hokyu_LS_s27A.wmv,wmav2,48000,2,unknown

docs/re/structures/movie-audio-channels.md

@@ -0,0 +1,47 @@
+# ✅ The disc ships movies in **two** audio profiles — and one of them is 5.1
+
+**Status:** ✅ `DECODED`, disc-wide (97 of 97 movies probed). Found while checking
+a transcode, not while looking for it.
+
+## The split
+
+```
+$ ffprobe -select_streams a -show_entries stream=codec_name,sample_rate,channels,channel_layout
+```
+
+| profile | count | codec | rate | channels | which |
+|---|---|---|---|---|---|
+| **surround** | **28** | `wmapro` | 48 kHz | **6 (5.1)** | `ADV.wmv` + every `S*.wmv` story cutscene |
+| stereo | 69 | `wmav2` | 48 kHz | 2 | every `RT*.wmv` and `hokyu_*.wmv` |
+
+Full list in [`data/movie-audio-layouts.csv`](../data/movie-audio-layouts.csv).
+
+The split is not arbitrary: the **cinematics** are 5.1 and the **in-mission radio
+chatter** is stereo. `ADV.wmv` (137.714 s) and `S00A.wmv` — the boot/attract intro
+and the new-game intro, i.e. **both movies the menu milestone needs** — are in the
+surround group.
+
+## ⚠️ Why this matters to anything that transcodes
+
+A single `ffmpeg` command over `dat/movie/` produces **two different kinds of
+result** and records neither:
+
+* the 69 stereo files pass through channel-wise unchanged;
+* the 28 surround files are **downmixed 5.1 → stereo by ffmpeg's default matrix**,
+  folding centre-channel dialogue into L/R at a weighting nobody chose.
+
+That default is a *content* decision — it sets how loud the dialogue is against
+the music — and it is **not stable across ffmpeg versions**. A pipeline that wants
+a reproducible result has to state the downmix explicitly rather than inherit it,
+and record it beside the command.
+
+🟡 Whether the game itself plays these in surround, and with what downmix when the
+console is set to stereo, is **not established here**. This page is about what is
+on the disc.
+
+## How it was found, and the trap next to it
+
+Checking a transcode against its source, `ffprobe` reported the output as 33 s
+against the source's 137 s — which reads as catastrophic truncation and is not:
+the file was **being written at that moment**. Measuring a live write produces a
+confident wrong answer with no error. See [`../METHOD.md`](../METHOD.md).