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handoff: deliver the concurrent-streams refutation to the page the port reads

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The finding landed in docs/re/ in the previous commit; an answer not reachable
from HANDOFF is not delivered. States plainly that "take one stream" was mine,
that the port implemented it, and that it is withdrawn -- together with the
caution that summing is not thereby right, because an equal-gain 1/n sum of
channel pairs is not a downmix and the port s measured 6.02 dB loss was real.
Neither rule is established, so the manifest should say the value is authored.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
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sylph-decoder
2026-08-29 15:49:32 +00:00
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@@ -536,6 +536,46 @@ the title**, where it overstates 4.183 s against ~2 s. It does **not** support
arrival-to-arrival timestamps compared against visible spans — the plate-delay
trap in a second place. Recorded on my side too.
## 🔴 2026-08-29 — THE GAME DECODES ALL THREE VOICE STREAMS AT ONCE. "Take one" is withdrawn.
**This overturns an instruction of mine that you implemented.** Full page:
[`voice-three-streams-are-concurrent.md`](../re/structures/voice-three-streams-are-concurrent.md) ·
[probe log](../re/data/voice-three-streams-runtime.txt)
Booted with `--xma_param_probe=true` — the cvar whose own comment says it exists
to reveal *which* sub-wave of a movie's `.slb` the game decodes. It does not
decode one. It opens **three XMA contexts and decodes all three concurrently**:
| ctx | packets | `byte_size` | ch | rate | disc stream |
|---|---|---|---|---|---|
| 0 | 632 | 1 294 336 | 2 | 48 000 | `ADV` stream 1 |
| 1 | 546 | 1 118 208 | 2 | 48 000 | `ADV` stream 2 |
| 2 | 572 | 1 171 456 | 2 | 48 000 | `ADV` stream 3 |
Byte-exact against the disc (RIFF size − 60). Only those three contexts appear.
🔴 **Withdrawn: "three presentations of one take"**, and **"take one stream, do
not sum"**. A consumer picking one discards two thirds of what the game mixes.
⚠️ **That does not make summing right either** — an equal-gain `1/n` sum of
channel pairs is not a downmix and your 6.02 dB complaint was real. **Neither
rule is established. You are authoring, and the manifest should say so.**
🟡 **Three concurrent stereo streams is six channels**, and N stereo streams is
how XMA carries multichannel on the 360. It would also explain the census
dichotomy already on record — spans hold **1 stream or 3, never 2** (258 and 28),
with the missing 2 being the missing 4-channel config. ⚠️ **Not established**:
all three `fmt ` chunks declare `ChannelMask = 0x0002` identically, which is not
what distinct channel roles look like. Hypothesis, with its counter-evidence.
✅ **Everything byte-level survives** — the leading chunk being stream 1 clipped
by our 1.5 MB guard, the 70 + 8 + 17 decomposition, the bank-header
discriminator. Those are about bytes and did not depend on the framing. Your
`S00A` silent-stream and `ADV` 0.60× measurements survive too, and now read as
measurements *of channels*.
⚠️ **Reach: one cue, one boot.** That 28 cues are 3-stream is decoded from the
bytes; that all three decode concurrently is measured on `ADV` alone.
## Status
| | Question | State | Answer / link |