port: a voice region is three presentations of one take -- keep one stream, sum nothing

Third reading of the same bytes in one session, and the first one that is
decoded rather than inferred.

  1. concatenate  -> 359 s of dialogue for a 137 s movie. Dead on measurement.
  2. sum as Q10's two stems -> refuted here: S00A's second full-length chunk is
     DIGITAL SILENCE and ADV's is 0.60x the first with 26.8 dB of residual. That
     claim was mine, and the Decoder had already adopted it before I tested it;
     it is withdrawn in both places.
  3. keep ONE stream. Decoded disc-wide by the Decoder, counting stream starts
     inside every inter-descriptor span: 258 spans hold one stream, 28 hold
     three, nothing holds two. So 359 = 84.55 + 137.32 + 137.32.

Summing was therefore wrong a third time, and for a third reason: a take plus a
0.60x copy of itself is ~4 dB louder and coloured, not a mix of parts. The filter
is now `[0:a]anull` plus the mono fold -- no gain applied at all.

`check` moves `voice` off the strict peak bound as a consequence. It sat with
`bgm` because it was a sum this exporter produced; it is now a single wave off
the disc, mastered near full scale -- ADV's louder presentation measures +0.0003
dBFS at source -- so refusing that would be refusing the disc's own mastering.

The leading chunk is dropped as a DUPLICATE, not a truncation. It is this
movie's own dialogue (the Decoder, 17 of 17) and I measured it to be the TAIL of
the kept stream: sliding envelope correlation r=0.998 / 0.932 with the lag flush
against that stream's end, controls 1.000 self and 0.289 for a different movie,
confirmed in the sample domain at 16.7 / 23.2 dB of residual.

STILL OPEN, and flagged rather than absorbed: WHICH presentation to keep. Highest
byte rate is the Decoder's recommendation and not a decoded field, and on ADV it
selects the QUIETER of two (-8.3 dBFS against 0.0). Said in the manifest with the
consequence, so it is visible and reversible. A capture of the intro with
dialogue audible settles it.

Not converted, and the Decoder has since withdrawn the ask with a better reason
than mine: its 504464 B anchor constant is structural, not proportional --
identical on all 17 regions, and a proportional prediction lands within 8 bytes
on ADV while being 4305 B out on S00A.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF

docs/port/DECISIONS.md

@@ -2734,3 +2734,59 @@ byte↔time mapping, and the numbers above are the reason there isn't one: chunk
 is 1 118 268 B and chunk 2 is 1 171 516 B for **the same 137.324 s**, so bytes per
 second is not constant even inside a single region. Any figure in seconds off
 that constant would be invented.
+
+## Third reading of a voice region, and this one is decoded: three presentations of one take
+
+`export_voice` has now read the same bytes three ways in one session, and each
+reading was ended by a measurement rather than by an argument:
+
+1. **Concatenate the chunks** — 359 s of dialogue for a 137 s movie.
+2. **Sum them as HANDOFF Q10's two stems** — refuted here: `S00A`'s second
+   full-length chunk is digital silence, `ADV`'s is 0.60 × the first with 26.8 dB
+   of residual.
+3. **Keep one stream.** ✅ This one is decoded, and not by me.
+
+The Decoder settled the shape disc-wide without a decoder, by counting stream
+starts inside every inter-descriptor span: **258 spans hold one stream, 28 hold
+three, and nothing holds two or any other number.** The 95 movie-voice regions
+decompose 70 + 8 + 17, and the 8 are independently the same 8 its first census
+flagged. So a region carries **three presentations of one take** — which is
+exactly `359 = 84.55 + 137.32 + 137.32`, the first clipped by its crate's own
+1.5 MB predecessor guard.
+
+It also cross-checked my correlation by a route needing no decoder: if the
+leading chunk is the tail of a full stream, the whole leading stream should be
+one complete take, and `ADV`'s 504 464 + 808 304 = 1 312 768 B at chunk 0's byte
+rate is **137.323 s against my measured 137.324**. Two instruments, no shared
+assumption.
+
+**So summing was wrong for a third reason:** a take plus a 0.60 × copy of itself
+is ~4 dB louder and coloured, not a mix of parts. The exporter keeps one stream
+and performs no arithmetic on it.
+
+🟡 **Which stream is a recommendation, not a decoded field.** The selector is the
+**highest byte rate** among the equal-duration survivors, on the Decoder's
+advice. Nothing on the disc says which presentation the game plays, and on `ADV`
+this picks the **quieter** of the two — −8.3 dBFS against 0.0. That is in the
+manifest in those words so the choice is visible and reversible; it is the one
+part of this that a capture could still overturn.
+
+`check` moves `voice` off the strict peak bound as a consequence. It sat with
+`bgm` because it was a sum this exporter produced; it is now a single wave off
+the disc, mastered near full scale — `ADV`'s louder presentation measures
+**+0.0003 dBFS at source** — and refusing that would be refusing the disc's own
+mastering.
+
+### The 504 464 B constant: I refused the conversion, and refusing was right
+
+The Decoder asked whether I would spend a decode converting its anchor offset to
+seconds, and I declined because bytes per second is not constant even inside one
+region. It has since found the stronger reason and withdrawn the ask: **the
+constant is structural, not proportional** — identical on all 17 regions despite
+their differing durations. A proportional prediction lands within 8 bytes on
+`ADV`, which is a coincidence, and is **4 305 B out on `S00A`**. A seconds figure
+off that constant would have been invented, and it would have looked corroborated
+on the first movie anybody checked.
+
+❔ **Why the disc stores three presentations at all is unanswered**, by either of
+us.