re: 69.8% of banks declare more data than they store -- and that explains TCAF_608

Of the 7586 banks with a RIFF and a data chunk after it, 5296 declare a data
size larger than the pak entry holds; 2290 declare less (the ordinary
multi-sub-wave case); NONE declare exactly what they hold. This contradicts the
decoder comment claiming the declared size 'is honest per sub-wave'. The code
clamps, so it is a documentation defect, not a crash.

It also closes the loose end from the offset work: eng\Voice\VOICE_TCAF_608,
the single bank where neither offset decoded, is 99% short -- there is nothing
there to decode.

Method note recorded: my first pass searched for 'data' from offset 0, which can
match by chance inside the leading audio region. Anchoring the search after the
first RIFF moved the count 5038 -> 5296.

Separately, the 55 'early RIFF' English banks are not an anomaly: all 55 sit at
exactly 1392 behind a zero-filled header -- a zero-length leading region, which
both the old and new code already handle correctly.

docs/re/BACKLOG.md

@@ -31,8 +31,13 @@ mistaken a constant derived from `eng\etc\` for a property of the format. See
 `Pj_Silph.xgs`, named by the same table's `BANK_SE` and `SETTINGS` records —
 `sound.pak` is now 9 519 of 9 519 accounted for.
 
-**Still open**: 55 English banks have their first `RIFF` at or before offset
-1392, and the 28 offset-scan ties.
+**Closed**: the 55 "early `RIFF`" English banks are not an anomaly — all 55 sit
+at *exactly* 1392 behind a zero-filled header, i.e. a zero-length leading
+region, which both the old code and the new derivation already handle.
+
+**Still open**: the 28 offset-scan ties, and ❔ why 69.8 % of banks declare more
+`data` than they store (see
+[`structures/slb-data-offset.md`](structures/slb-data-offset.md)).
 
 ---
 

docs/re/structures/slb-data-offset.md

@@ -51,15 +51,17 @@ must and does reproduce the old behaviour exactly. Individual cases:
     jpn\Voice\VOICE_TCAF_592.slb    2 910 -> 127 178 bytes   (44x)
     eng\etc\VOICE_D_452.slb        30 154 ->  30 154 bytes   (unchanged, control)
 
-## The one counterexample
+## The one counterexample — ✅ explained
 
 `eng\Voice\VOICE_TCAF_608.slb` decodes 2 840 bytes at 1392 and 896 at 1468.
 
-It is worth being precise about what that is and is not. It is **not** a bank
-where the old constant works and the derived offset fails: its leading region is
-38 988 bytes, and *both* offsets yield well under a tenth of a second, i.e. both
-fail. 1392 merely produces marginally more garbage. Whatever is wrong with this
-bank is a separate defect and is **not settled** here.
+It is **not** a bank where the old constant works and the derived offset fails:
+both offsets yield well under a tenth of a second from a 38 988-byte region,
+i.e. both fail, and 1392 merely produces marginally more garbage.
+
+**The reason is that the bank is truncated.** Its `data` chunk declares 759 808
+bytes and the pak entry holds 8 864 — **99 % short**. There is almost nothing
+there to decode at any offset. See the section below.
 
 ## ❌ This withdraws my own claim from earlier the same day
 
@@ -123,10 +125,43 @@ derived from it exactly, never scanned.
 * **Why the offset takes those four values**, and what the bytes before it are.
   There is no length field in the first 64 bytes — banks open on high-entropy
   data — so the offset is derived, not read.
-* **`eng\Voice\VOICE_TCAF_608.slb`**, above.
+
 * **The 28 ties.** The scan cannot separate them and falls back to 1392, which
   is right for roughly a third of that population and wrong for the rest.
 * **Why the offset takes exactly these four values by directory** is still
   unexplained — see above.
 * Nothing here was run **in the game** — this is a decoder-side result measured
   with FFmpeg as the oracle.
+
+
+## 🟡 Most banks declare more `data` than they store
+
+**Measured 2026-08-26.** Of the 7 586 banks that carry both a `RIFF` and a
+`data` chunk after it, **5 296 (69.8 %)** declare a `data` size larger than the
+bytes actually present in the pak entry. The remaining 2 290 declare *less*,
+which is the ordinary multi-sub-wave case. **Not one declares exactly what it
+holds.**
+
+Worst cases run to 99 % short:
+
+    eng\Movie\VOICE_RT16C.slb    declared 1 810 432   available 489 392   -73 %
+    jpn\etc\VOICE_D_589.slb      declared 1 177 600   available   6 708   -99 %
+    eng\Voice\VOICE_TCAF_608.slb declared   759 808   available   8 864   -99 %
+
+This **contradicts a claim in the decoder's own comment**, which says the
+declared size "is honest per sub-wave". It is not, for about seven banks in ten.
+The code is nonetheless safe — it clamps the range with `.min(slb.len())` — so
+this is a documentation defect and an integrity observation, not a crash.
+
+⚠️ **Method note on this measurement.** My first pass searched for `data` from
+offset 0, which can hit those four bytes by chance inside the leading audio
+region and read a garbage length. Re-running it anchored *after* the first
+`RIFF` changed the count from 5 038 to 5 296 — the flaw was slightly
+*under*-counting, but it could as easily have gone the other way, and an
+unanchored chunk search over binary audio is not a safe way to ask this
+question.
+
+❔ **Why** the declared sizes are too large is **not settled**. Plausible
+readings — an authoring-time allocation that was never trimmed, or deliberate
+truncation of unused tails — are guesses; nothing here distinguishes them, and
+the game has not been observed reading one of these banks.