Syplheed-Reborn/docs/re/capture-harness-status.md

🔴 Why the boot harness stopped reaching the title — screenshot costs 10.8 s

Status: ✅ diagnosed, with a control. Four consecutive runs on 2026-08-28/29 failed to reach the interactive title, across two locales, two launch paths and two display-gamma settings. The cause is none of those.

The measurement

condition	one screenshot call
while Xenia Canary is running	10.8 s
immediately after killing it	0.117 s

92×. The 1-minute load average at the slow measurement was 1.80, so this is contention with the emulator (both go through the same X server), not general system load.

Why that breaks the harness

skip_intro.sh takes two grabs 0.6 s apart per iteration, plus an is_title.py numpy load. Its actual sample timestamps in the last run:

57, 95, 177, 218, 238, 298, 333, 380, 426, 471, 515   → intervals
38, 82, 41, 20, 30, 30, 35, 47, 46, 45, 44, 43, 21, 19  median 41 s

A 41-second sampling interval against a title screen that the corpus already documents as lasting "a few seconds" before auto-returning to the attract loop (wait_title.sh's own header). The harness is not seeing a stuck game; it is blinking slower than the thing it is looking for.

That is also why runs at 16:43–18:05 the same day succeeded and later ones did not — nothing about the game changed.

🔴 What this retracts

Three earlier conclusions were built on these runs and are withdrawn as causes, though the observations stand:

• "the Japanese-locale run never reaches the interactive title" — it may well have appeared, unsampled.
• "neither locale reaches the interactive title without a pad press" — the English control shared the same defect, so it controlled for locale but not for the sampling rate.
• "the game sat in the attract loop for 604 s" — what was observed is that every one of ~15 samples landed on movie content, which at a 41 s interval is a much weaker statement than it reads as.

⚠️ A confound I introduced

Setting kernel_display_gamma_type = 0 makes the frame substantially brighter (a mid-attract frame measured mean 122.8 against 52.5 and 82.8 on comparable phases at type 2). skip_intro.sh classifies movie-vs-static on an absolute rmse threshold of 1500 between two grabs, so a brighter output inflates that difference and biases every frame toward "movie". The capture harness's tuning is coupled to the display settings — changing gamma and capture behaviour in one run confounds both.

🔴 The fix works — and it REFUTES the diagnosis above

Built and measured (tools/re-capture/fast_title_probe.py): one long-lived ffmpeg x11grab stream, raw RGB frames, glyph counted in numpy. No per-sample process startup, no PNG encode, no convert -crop.

probe	seconds per sample, emulator running
the wrapper screenshot	3.98
import -window root → PPM	1.20
long-lived x11grab stream	0.29

13.7× faster, and the counter is control-verified against the committed frames — it returns 753 on live-title-press-a.png and 327 on live-main-menu.png, byte-identical to is_title.py.

Then it was pointed at a running game:

332 frames in  85.3 s = 3.89 fps; max glyph 0
1674 frames in 420.0 s = 3.99 fps; max glyph 0

1 674 consecutive samples over seven unbroken minutes, four per second, and the interactive title never appeared. So the sampling rate was a real defect and not the cause. The hypothesis on this page — that the harness was blinking slower than the event — is mine, and refuted by my own fix.

What that restores

Last iteration I withdrew three conclusions on the strength of that hypothesis. The withdrawal was right at the time (15 samples at 41 s intervals cannot support them) and is now superseded by better evidence: dense sampling says the interactive title genuinely does not appear in a mid-run window. Reinstated as a measurement, with its reach:

• ✅ over 420 continuous seconds, English, gamma_type = 2, ~13 minutes into a run with no pad input, zero frames carried the green Ⓐ glyph.
• ⚠️ Reach: this covers a mid-run window only. It says nothing about the first minutes of boot.

🟡 The leading hypothesis, not confirmed

The corpus already suspects the answer. title_states_capture.sh exists to test "whether the interactive one draws ptbtn00 (the PRESS Ⓐ plate) and the other does not" — i.e. the title appears twice: once at the end of the boot sequence, and again from the attract loop, and only the first may carry the plate. If so, the plate's window is early and one-shot, and no amount of mid-run sampling will ever find it.

That is consistent with everything measured, and it is not confirmed. The test is to start the fast probe before the boot title — from t=0 rather than attaching to a run already in progress.

The original fix note, kept

Make the probe cheap enough to sample faster than the title window: grab a small region rather than the full surface, drop the ImageMagick convert round trip, or keep the glyph test in one long-lived process instead of re-importing numpy per sample. None of that is done — this page is the diagnosis, and it is what every remaining emulator-side question is waiting on.

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🔴 The boot-window hypothesis is refuted too — and the surface is BLACK

2026-08-29, third explanation and third refutation. The named experiment was to attach the fast probe at t = 0 so the boot title could not be missed. Done, on the default config, English:

2391 frames in 600.4 s = 3.98 fps; max glyph 0; hits 0

Ten minutes, sampled four times a second from launch, and the green Ⓐ glyph never appeared. So "the plate only shows in an early boot window I keep missing" is mine, and refuted.

Then the thing I should have checked first. Splitting the raw root grab by band:

band	non-black	mean
y 0–44 (the GTK menu bar)	100 %	210.5
y 45–719 (the game surface)	0.08 %	0.07

The game is rendering black, reproducibly across back-to-back samples, while the guest is alive and polling input (XamInputGetKeystrokeEx past 1 201 calls) and MEM-WATCH keeps reporting. The crop and every pixel oracle were correct; there was nothing on the surface to detect.

⚠️ What this does and does not explain

It does not retroactively explain the earlier failures, and saying so would be the fourth over-reach in a row. Those runs had content: run 2 sampled frames at mean 33.1 (warm), run 3's classifier measured real frame-to-frame rmse, and the gamma_type = 0 run measured mean 122.8. A black surface is this run's symptom.

So the honest reading is that the failure mode changed over the session, and the black screen is a new and worse one.

🟡 Hypothesis for the regression, untested

Canary's shader/pipeline cache at ~/.local/share/Xenia/cache is 47 MB and was last written 23:49 on 2026-08-28 — during the failed runs. This session has kill -9'd the emulator repeatedly, which can leave a partially written cache. A corrupt pipeline cache is a plausible route to a guest that runs while nothing reaches the screen.

The test is one line and one run: move cache* aside and boot again. Not done — it needs a fresh 10-minute run, and this iteration had spent its emulator budget proving the negative above.

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🔴 The fast probe STALLS — and that invalidates its own dense negatives

2026-08-29. The instrument built last iteration is unfit for long runs, found by cross-checking it against an independent grabber while both watched the same screen.

A single long-lived ffmpeg x11grab stream degrades and then freezes:

862 frames in 540.1 s = 1.60 fps          (it starts at 3.98 fps)
t=450s surface mean 5.21 nonblack 10.1%
t=480s surface mean 5.21 nonblack 10.1%
t=510s surface mean 5.21 nonblack 10.1%
t=540s surface mean 5.21 nonblack 10.1%

Four consecutive 30-second marks reporting an identical value. At that same moment an import grab of the same display read surface mean 125.65, and a freshly started ffmpeg stream read 122.43 — agreeing with import to 3 %. So the acquisition, not the analysis, was broken: the stream was replaying a stale frame while the screen was 24× brighter.

🔴 Therefore the previous section's headline is withdrawn. "2 391 frames over 600 s from t=0, max glyph 0" cannot distinguish the title never appeared from the stream froze early and repeated one frame 2 391 times. Its 3.98 fps was measured over the first 20 s, before the degradation.

Fixed in tools/re-capture/fast_title_probe.py: the stream is torn down and restarted every 30 s. Startup costs ~0.3 s, cheap against the title's window, and it buys a guarantee the frames are live.

✅ Clearing the shader cache restored rendering

The cache hypothesis from the previous section was tested: cache, cache0, cache1 and cache_host moved aside (to /tmp/xenia-cache-aside, not deleted), then a fresh boot.

The surface renders again, confirmed with the independent grabber: import reads surface mean 54.8 and 68.6 on successive samples with 100 % non-black warm content, against 0.07 and 0.08 % non-black in the black run. The probe's own summary agrees where it can be trusted — **773 of 862 frames had

2 % non-black**.

🟡 Supported, not proven. One run each side, and the emulator was kill -9'd many times before the black run, so a corrupt pipeline cache is plausible but a single A/B does not exclude run-to-run variation. The old caches are kept in /tmp/xenia-cache-aside if anyone wants to reproduce the failure.

❔ Still no title. Even rendering, max glyph 0 — but that number now comes from a stalling probe, so it establishes nothing either way.