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re: the resupply banks really are missing audio — the subtitles prove it

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The corpus said 0.14 s is "far too short for the spoken line". That is a
judgement about audio, and audio judgements cannot be made in this container.
The subtitle tracks settle it without listening: each carries cue START
times, and a subtitle that appears at t seconds cannot sit inside a clip
shorter than t.

FFmpeg-measured (not estimated from a compression ratio -- the first version
of this example used an 8:1 guess, which is not good enough to hang a
conclusion on):

  hokyu_LS_s02A  D_450  cue 4.00 s  audio 1.41 s  MISSING
  hokyu_LS_s09A  D_451  cue 3.70 s  audio 1.81 s  MISSING
  hokyu_LS_s02H  D_453  cue 4.70 s  audio 0.07 s  MISSING
  hokyu_DS_s13A  D_452  cue 0.00 s  audio 1.21 s  no signal
  hokyu_DS_s07H  D_454  cue 0.00 s  audio 0.21 s  no signal

Three of five are decisive; the other two have their only cue at 0.0 s and
say nothing either way. So something is genuinely missing from these banks --
established independently of the leading-region work, and measured rather
than felt.

The fmt-variation probe I recorded as the next step is INCONCLUSIVE and is
written up as such: 36 combinations over VOICE_D_453's 22-packet leading
region all produced 0 PCM bytes, including ones that should be equivalent to
the crate's own synth_xma1_fmt, which does parse. So the probe tested my
hand-built fmt chunk, not the hypothesis, and it is NOT evidence that the
region is non-XMA. The retry should use the crate's helper.

Artifact: examples/voice_len_vs_subs.rs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE
This commit is contained in:
Sylpheed RE agent
2026-08-25 23:45:26 +00:00
parent 49a09a9496
commit af320466bb
3 changed files with 127 additions and 3 deletions
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15
docs/re/BACKLOG.md
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@@ -1057,9 +1057,18 @@ premise was wrong.**
Byte coverage was the wrong success metric. The rule also matches **1524 of
8021** RIFF-bearing `sound.pak` entries, including `RT*` banks that work today,
so it risked a wide regression to not-fix five banks.
▶️ Next cheap probe: vary the synthesised `fmt` (channels / streams / sample
rate) instead of assuming the container. Then a human has to listen; audio
judgement cannot be done here. See
✅ **(same day) Audio really IS missing — proven by the subtitle cue times**,
not by the "sounds too short" impression the docs recorded. A subtitle that
appears at *t* seconds cannot sit inside a clip shorter than *t*, and three of
five banks fail that: `D_450` cue 4.00 s vs 1.41 s decoded, `D_451` 3.70 vs
1.81, `D_453` **4.70 vs 0.07**. The other two have their only cue at 0.0 s and
give no signal. Artifact `examples/voice_len_vs_subs.rs`, FFmpeg-measured.
❔ **The fmt-variation probe was INCONCLUSIVE** — 36 combinations over
`VOICE_D_453`'s leading region all produced 0 PCM bytes, *including* ones
equivalent to the crate's working `synth_xma1_fmt`, so the probe tested my
hand-built `fmt` chunk rather than the hypothesis. Not evidence the region is
non-XMA. ▶️ Retry building the chunk with the crate's own helper and varying
its parameters. See
[`voice-bank-leading-region.md`](voice-bank-leading-region.md).
* ❌ **(2026-08-25) My own boot-nav diagnosis, MEASURED AND WITHDRAWN.** I said
the run died because `skip_intro.sh` gates the title test at `rmse <= 1500`

37
docs/re/voice-bank-leading-region.md
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@@ -120,6 +120,43 @@ it.** Two measurements killed it:
The refuted attempt is recorded in `slb.rs` beside the code, so the next person
does not re-derive the arithmetic and re-make the same change.
## ✅ Audio really is missing — proven by the subtitles, not by impression
The corpus's original wording was that 0.14 s is "far too short for the spoken
line". That is a judgement, and judgements about audio cannot be made in this
container. The subtitle tracks settle it instead: each carries **cue start
times**, and a subtitle that appears at *t* seconds cannot sit inside a clip
shorter than *t*.
Decoded with FFmpeg (measured, not estimated from a compression ratio — the
first version of this used an 8:1 guess and that is not good enough to hang a
conclusion on), artifact `examples/voice_len_vs_subs.rs`:
| movie | bank | last cue | decoded audio | verdict |
|---|---|---|---|---|
| `hokyu_LS_s02A` | `D_450` | 4.00 s | 1.41 s | **audio missing** |
| `hokyu_LS_s09A` | `D_451` | 3.70 s | 1.81 s | **audio missing** |
| `hokyu_LS_s02H` | `D_453` | 4.70 s | **0.07 s** | **audio missing** |
| `hokyu_DS_s13A` | `D_452` | 0.00 s | 1.21 s | no signal |
| `hokyu_DS_s07H` | `D_454` | 0.00 s | 0.21 s | no signal |
Three of the five are decisive; the other two have their only cue at 0.0 s, which
tells us nothing in either direction. So **something is genuinely missing from
these banks** — independent of anything above, and now measured rather than felt.
## ❔ Varying the XMA format — inconclusive, and for a boring reason
The recorded next step was to vary the synthesised `fmt` (channels, streams,
sample rate) rather than assume the container. I tried 36 combinations over
`VOICE_D_453`'s 22-packet leading region and **every one produced 0 PCM bytes** —
including combinations that should be equivalent to the crate's own
`synth_xma1_fmt(2, 2, 48000)`, which does at least parse (it yields 1792 bytes).
That means the probe tested **my hand-built `fmt` chunk**, not the hypothesis. It
is not evidence that the region is non-XMA. The next attempt should build the
chunk with the crate's own helper and vary its parameters, rather than
hand-rolling the WAVEFORMATEX.
## What this does not settle
* ❔ **What the leading region holds.** Its *size* is now exact (1392 + n·2048)