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+# 🔴 A 6-channel PulseAudio capture SCRAMBLES AND DUPLICATES channels unless the maps match
+
+**Classification: measured**, on the capture chain itself rather than on the
+game. Recorded because a capture taken with this defect was handed to the port
+as evidence, cost them a full controlled analysis, and the negative they
+correctly reported was **my instrument, not the guest**.
+
+## What happened
+
+`adv-game-output-6ch.wav` was captured from Canary through a PulseAudio null
+sink and shared as "what the game emits during `ADV`". The port could not match
+it against **anything** — the `ADV` bed, any of the three XMA voice streams,
+`BGM_103`, `S00A` — with best-vs-runner-up margins of 0.001–0.016 everywhere,
+i.e. plateaux rather than peaks. They controlled that three ways (their
+instrument finds `bed` vs `bed` at r=1.000 margin +0.115; their `.ogv` reference
+matches the disc's `.wmv` at r=1.000 margin +0.114; and drift was excluded by
+windowed lags scattering across the movie). They also observed that **capture
+channels 3 and 6 were byte-identical, same MD5**.
+
+That duplicate pair is the tell, and it is reproducible without the emulator.
+
+## The control I should have run first
+
+Six channels, each a **different** tone, so any reorder, drop or duplication
+shows up as a wrong frequency. Played to the sink with `paplay`, recorded from
+its monitor with the same `parec` invocation the `ADV` capture used.
+
+**Sink map `FL,FR,RL,RR,FC,LFE`, i.e. NOT the stream's map — the original setup:**
+
+| channel | expected | captured | |
+|---|---|---|---|
+| 0 | 400 Hz | 400 Hz | ok |
+| 1 | 800 Hz | **3200 Hz** | wrong |
+| 2 | 200 Hz | 200 Hz | ok |
+| 3 | 1600 Hz | **800 Hz** | wrong |
+| 4 | 3200 Hz | **800 Hz** | wrong |
+| 5 | 6400 Hz | **200 Hz** | wrong |
+
+`ch2 == ch5`, **byte-identical** — the same artefact the port found. The 6400 Hz
+and 1600 Hz channels are **gone entirely**, replaced by duplicates.
+
+**Sink map made identical to Canary's own stream map**
+(`front-left,front-right,front-center,lfe,rear-left,rear-right`), and the same
+map given to `parec` explicitly:
+
+| channel | expected | captured |
+|---|---|---|
+| 0–5 | 400 / 800 / 200 / 1600 / 3200 / 6400 | **400 / 800 / 200 / 1600 / 3200 / 6400** |
+
+No duplicates. **CONTROL PASSED.**
+
+## The rule
+
+⚠️ **A null sink whose `channel_map` differs from the client's makes PulseAudio
+remap, and a 6-channel remap silently loses channels and duplicates others.**
+There is no error, no warning, and the WAV has the right length, the right
+channel count and plausible per-channel levels. Set the sink's map to the
+client's, and pass the same map to `parec`:
+
+```bash
+MAP=front-left,front-right,front-center,lfe,rear-left,rear-right
+pactl load-module module-null-sink sink_name=cap channels=6 channel_map=$MAP
+parec -d cap.monitor --channels=6 --rate=48000 --format=s16le --channel-map=$MAP …
+```
+
+## 🔴 What this withdraws
+
+* **`adv-game-output-6ch.wav` is withdrawn as evidence.** Its channels are
+  scrambled and one pair is a duplicate. Nothing should be concluded from it,
+  in either direction — it is not evidence that the game emits something
+  unexpected, and the port's inability to match it is fully explained.
+* **"All six channels carry signal"** — withdrawn. One of the six was a copy of
+  another.
+* **"The surround and LFE channels are not zero, which a stereo guest padded
+  into a 6-channel frame would give"** — withdrawn. It was offered as weak
+  support for the 5.1 reading of a voice cue's three streams
+  ([`voice-three-streams-are-concurrent.md`](structures/voice-three-streams-are-concurrent.md)),
+  and it is worth nothing. The port said a duplicated channel is not an
+  independent one, and they were right before this control existed.
+
+✅ **Unaffected:** the three-XMA-context concurrency result. That is read from
+the emulator's own log, not from the audio path, and it reproduced on two
+independent boots.
+
+## The lesson, in the form it should have been applied
+
+The corpus's own rule is *run your instrument through a control first*. Here the
+control needed no emulator, no disc and 30 seconds: **play a known signal through
+the capture chain and check that it comes back.** It was not run, an artefact was
+published, and the person who found the defect was the one who could not see the
+instrument. ⚠️ **A capture is an instrument, not just an output** — the same
+scrutiny a parser or an estimator gets.