From a13dd42c2d3c8a705a12fa6687ce620e11d283ae Mon Sep 17 00:00:00 2001 From: sylph-decoder Date: Sat, 29 Aug 2026 17:05:37 +0000 Subject: [PATCH] re: stripping additive padding is exact -- controlled, and only one side needs it The page recorded the substituted-versus-additive distinction as unverified, with the port controlling it. It passes. A real music and SFX bed of 137.37 s, itself carrying 454 genuine zero runs -- which is what makes it an honest control -- had 1149 holes inserted at 8.37 gaps/s to +9.9 percent length, matching the measured ALSA profile, then stripped: original vs itself (ceiling) r 1.000 lag 0.0 s margin +0.141 padded vs original r 0.436 lag -12.2 margin +0.006 stripped vs original r 1.000 lag 0.0 margin +0.142 Two things beyond the yes. It runs the inference forwards: padding at this profile puts correlation squarely in the known-absent regime on a file whose contents are controlled, so the earlier captures were unusable for the reason claimed rather than for some other one -- until now that was reasoning backwards from a failure to a cause. And only one side needs stripping, since the stripped capture matches the UNSTRIPPED source at the ceiling, so a capture needs no preprocessing before being handed over and there is no shared step to get out of sync on. The danger is recorded as the part to repeat: stripping removes genuine silence too and cannot tell the two apart, so it is exact on additive ALSA padding and vandalism on a PulseAudio monitor capture where the silence replaced real audio. Running it on the wrong artefact would look like it worked. Co-Authored-By: Claude Opus 5 (1M context) Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd --- docs/re/audio-capture-alsa-file-tee.md | 34 +++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 4 deletions(-) diff --git a/docs/re/audio-capture-alsa-file-tee.md b/docs/re/audio-capture-alsa-file-tee.md index 7a0d0355..b120fc16 100644 --- a/docs/re/audio-capture-alsa-file-tee.md +++ b/docs/re/audio-capture-alsa-file-tee.md @@ -186,10 +186,36 @@ means even the 0.70×-real-time rendered capture (9.98 % padded) is usable for correlation, where none of the PulseAudio-monitor captures ever were, however they were tuned. -⚠️ **Unverified as of writing** — the port is controlling it before relying on -it, by padding a known source to match and checking the stripped result -correlates back. The mechanism says it should; the control is what will settle -it. +✅ **VERIFIED 2026-08-29.** The port controlled it rather than relying on the +reasoning: a real music+SFX bed (137.37 s, carrying **454 genuine zero runs of +its own**, which is what makes it an honest control) had **1 149 holes inserted +at 8.37 gaps/s to +9.9 % length** — matching the measured ALSA profile — then +stripped: + +| | r | lag | margin | +|---|---|---|---| +| original vs itself (ceiling) | 1.000 | 0.0 s | +0.141 | +| **padded** vs original | **0.436** | −12.2 s | **+0.006** | +| **stripped** vs original | **1.000** | **0.0 s** | **+0.142** | + +Two things beyond the yes: + +* ✅ **It runs the inference forwards.** Padding at this profile puts correlation + squarely in the known-absent regime (margin +0.006) on a file whose contents + are controlled — so the earlier captures were unusable *for the reason claimed* + rather than for some other one. Until now that was reasoning backwards from a + failure to a cause. +* ✅ **Only ONE side needs stripping.** The stripped capture matches the + **unstripped** source at the ceiling, so a capture needs no preprocessing at + all before being handed over — no shared step for two parties to get out of + sync on. + +🔴 **And the danger, which is the part to repeat:** stripping removes *genuine* +silence too and cannot tell the two apart. It is **exact on additive ALSA +padding and vandalism on a PulseAudio monitor capture**, where the silence +replaced real audio. On mostly-silent material the genuine runs would cost +something measurable — here they totalled 0.71 s in 137 s and cost nothing. +⚠️ **Running it on the wrong artefact would look like it worked.** ⚠️ **Consequence for `check-capture`:** its silence/gap-rate rule was built when only *damage* existed, and **cannot distinguish genuine emulator padding from