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port: attempt the P4 fidelity question -- four traps reproduced, no verdict claimed

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AUDIO-VERIFICATION.md section 1 calls transcode fidelity the question P4 actually
raised, needing neither an engine nor a device, and gives it in four lines of
shell. Nothing implemented it: verify-video-audio deliberately declines, saying a
difference RMS without alignment is meaningless. So the P4/P7 gate has rested on
level and non-silence and the fidelity claim has never been made.

tools/port/verify-transcode-fidelity now exists and is committed WITHOUT a
verdict, deliberately.

Four ways the measurement lies, each reproduced here rather than reasoned about.
Indexing with a negative lag wraps to the end of the array in Python, so the
difference was the transcode subtracted from an unrelated part of the source --
reported 7 dB LOUDER than the source, the same catastrophic-looking number the
doc warns of. My regex for the recorded -af truncated the fold to its FL half,
folding the source to a left-only signal: the doc names that trap, I reached it
through a parsing bug, and the matrix contains runs of spaces so it cannot be
tokenised on whitespace. -ss before -i is a container-level jump and on this WMA
Pro source returned 4.6 s for a 4.0 s request while the Ogg side returned 4.0 s,
so the windows covered different stretches of the movie, best correlation 0.172 --
this one is NOT in the doc and is indistinguishable from the alignment trap that
is. And the single-resolution search returned +2413 against a window of +-2400,
its own boundary rather than a peak, the same family as the Decoder's period
estimator returning its search floor.

Why no verdict: best alignment is corr 0.763 on S00A and 0.075 on ADV, and both
still report the difference louder than the source, which cannot be true of two
aligned signals at equal level. The remaining fault is on my side. A tool printing
'not faithful' in that state would put a false defect on the exporter. It now
distinguishes 'could not align' from 'not faithful', two failures I conflated
twice before separating them.

Filed for the human as a proposal, not an edit: section 1 should carry the
imprecise-seek trap as a fourth entry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF
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Sylpheed port agent
2026-08-30 23:33:38 +00:00
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docs/port/BLOCKED.md
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@@ -147,6 +147,13 @@ HANDOFF.
| ~~P1–P7 — the keyframe record layout~~ | ~~adopt the corrected pose/time pairing~~ | — | ✅ **ADOPTED 2026-08-29 by pinning `formats-pin-2026-08-29c`.** This row was wrong twice: it said the change *"cannot be taken yet"* and that it *"reaches the port only when that branch lands on `main`"*. **It arrives when the tag is pinned**, which is what MISSION §2's tagging rule exists for. ⚠️ And the knob I tested first, `SYLPHEED_KF_TIME_SHIFT`, is a **retired partial fix** that left pose 0 untimed — the real correction is the tagged crate's default, with the old reading behind `SYLPHEED_KF_TIME_LEGACY=1`. **The blast radius was far smaller than this row predicted**: under the correction *every pose is timed* (866 keyframes, 0 untimed), so `pose_at`'s synthetic-exit branch became dead code rather than wrong code and nothing needed re-deriving. Oracle: `publisher_logo` 1.00 %→**0.75 %**, `developer_logos` 0.39 %→**0.33 %**, `extras`' differing region collapsing from 736×525 to **398×295 at the sweep position**. 🔴 Open cost: `sylpheed-cli` builds from the workspace crate, so `verify-screen` compares two decoder eras until the tag reaches `main`. Revert to the path dependency then. |
| ~~P7 / naming — the four unnamed builds~~ | ~~which locale and variant is each of entries 0, 1, 12, 15?~~ | — | ✅ **answered 2026-08-29** (`docs/re/ui-title-build-map.md`): all four are the loading screen, two variants — plain (7 elements) and dressed (10) — decoded from their own `pgloading_*` element names. ⚠️ **Not adopted as names yet, for two reasons the RE agent gave and one the port found.** Theirs: the executable names exactly two, and *which* bundle takes which name is 🟡 undecided, so `LOADING`/`LOADING2` must not go in an asset path; and locale is 🟡 — the English member of a pair is the one in the first half of `GP_TITLE.p00`, 8/8 structurally but only 3/3 where a capture can check, and the three pairs that matter are the three no capture can check. Mine: **the message gives the bundles as "0/1 and 10/11", which is the `is_build` ordinal, and `authored/screen_names.json` is keyed by PAK ENTRY** — in entry space 10 and 11 are `palogo_sqex` and `palogo_gamearts`, the splashes. See the refutation section in `DECISIONS.md`. |
## Open on my own side, 2026-08-30 — derived from HANDOFF `0159527`
| Milestone | Needs | HANDOFF | State |
|---|---|---|---|
| P4/P7 — transcode fidelity | **nothing from anybody; my instrument cannot answer yet** | `0159527` | 🔴 **THE GATE HAS NEVER CARRIED A FIDELITY CLAIM, and now it says so.** `AUDIO-VERIFICATION.md` §1 calls this the question P4 actually raised; nothing implemented it, and `verify-video-audio` explicitly declines it. `tools/port/verify-transcode-fidelity` exists and is **report-only**: best alignment is corr 0.763 on `S00A` and 0.075 on `ADV`, and both still report the difference *louder* than the source, which is impossible for two aligned signals at equal level — so the fault is on my side of the instrument, not necessarily in the transcodes. Four traps reproduced on the way, three of which §1 names and one (**`-ss` before `-i` returning 4.6 s for a 4.0 s request**) it does not. ⚠️ A tool printing "not faithful" in this state would put a **false defect on the exporter**. |
| P4/P7 — a `§1` addition for the HUMAN | **add the imprecise-seek trap to `AUDIO-VERIFICATION.md` §1?** | `0159527` | 🟡 **proposed, not done.** §1 lists three ways the measurement lies; a fourth is now reproduced — a container-level seek returns a different span than requested, so the two windows cover different audio and no shift can align them (best corr 0.172). It is **indistinguishable from the alignment trap §1 already names**. §1 is the human's document, so this is a proposal rather than an edit. |
## Not blocking, recorded so nobody re-investigates — 2026-08-30, HANDOFF `91ada14`
| Milestone | Needs | HANDOFF | State |

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docs/port/DECISIONS.md
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@@ -9,7 +9,7 @@ dies, which is what this file is for.
<!-- INDEX: generated by tools/port/index-decisions -- do not hand-edit -->
256 sections. Search this before re-deriving anything.
257 sections. Search this before re-deriving anything.
* [P0 — the exporter, 2026-08-28](#p0--the-exporter-2026-08-28)
* [P1 — Godot draws the screen, 2026-08-28](#p1--godot-draws-the-screen-2026-08-28)
@@ -267,6 +267,7 @@ dies, which is what this file is for.
* [Their rule applied backwards: my video result is stronger than my withdrawal said](#their-rule-applied-backwards-my-video-result-is-stronger-than-my-withdrawal-said)
* [🔴 I measured my own claim and it is wrong: the player skips, heavily](#i-measured-my-own-claim-and-it-is-wrong-the-player-skips-heavily)
* [🔴 Correcting the correction: the frame probe is an UPPER BOUND, and my contrast was contention](#correcting-the-correction-the-frame-probe-is-an-upper-bound-and-my-contrast-was-contention)
* [The P4 fidelity question, attempted: four traps reproduced, no verdict yet](#the-p4-fidelity-question-attempted-four-traps-reproduced-no-verdict-yet)
<!-- /INDEX -->
## P0 — the exporter, 2026-08-28
@@ -13204,3 +13205,48 @@ ask what else was running.*
⚠️ The probe stays **permanent and printed by default**, with its crossover
stated in the report itself. Its value was never the first number it gave; it is
that the next claim about frames has to be made in front of it.
## The P4 fidelity question, attempted: four traps reproduced, no verdict yet
`AUDIO-VERIFICATION.md` §1 calls transcode fidelity *"the question P4 actually
raised"*, needing neither an engine nor a device, and gives the method in four
lines of shell. **Nothing implemented it.** `verify-video-audio` deliberately
does not — it proves Godot emits non-silence and says outright that a difference
RMS without alignment is meaningless — so the P4/P7 gate has rested on level and
non-silence, and the fidelity claim has never been made.
`tools/port/verify-transcode-fidelity` now exists. **It does not yet produce a
verdict, and it is committed saying so.**
### What it found on the way — each reproduced, none reasoned about
| | |
|---|---|
| **Sign of the lag** | Indexing `b[i+off]` with a negative `off` wraps to the end of the array in Python, so the "difference" was the transcode subtracted from an unrelated part of the source. Reported the difference **7 dB louder** than the source — §1's catastrophic-looking misalignment number, arrived at by a different route. |
| **Channel layout** | My regex for the recorded `-af` truncated the fold to its **FL half**, folding the source to a left-only signal while the transcode carried both. §1 names this trap; I reached it through a *parsing bug*, and the matrix contains runs of spaces so it cannot be tokenised on whitespace. |
| **Imprecise seek — NOT in §1** | `-ss` before `-i` is a container-level jump. On this WMA Pro source a 4.0 s request returned **4.6 s** while the Ogg side returned 4.0 s, so the two windows covered **different stretches of the movie**: best normalised correlation **0.172**, no shift could align them. Decoder-side `-ss` after `-i` is exact. **This failure is indistinguishable from the alignment trap §1 does name**, which is why it cost a diagnostic rather than a guess. |
| **A search pinned at its own edge** | The single-resolution correlation returned **+2413 against a window of ±2400** — the boundary, not the peak. Same family as the Decoder's period estimator returning its own search floor: **an instrument answering with a property of itself.** Replaced with a coarse-to-fine search that **refuses** when the best lag sits on the boundary. |
### 🔴 Why it is committed without a verdict
Best alignment so far is **corr 0.763** on `S00A` and **0.075** on `ADV`, and both
still report the difference **louder** than the source — which cannot be true of
two aligned signals at equal level. **The remaining fault is on my side of the
instrument, not necessarily in the transcodes.**
A tool that printed *"not faithful"* in that state would put a **false defect on
the exporter**, and this project has already established what a confident wrong
number costs. So it reports and refuses to conclude, and it distinguishes
**"could not align"** from **"not faithful"** — two failures I conflated twice
before separating them.
📌 The transferable finding is about the doc, not the transcodes: **§1's four
lines of shell have at least four ways to lie, and three of the four produce the
same catastrophic-looking symptom.** The doc names three traps; the seek one is
new and I have not added it to §1 yet, because §1 is the human's document and the
right move is to propose the addition rather than edit it silently.
⚠️ **Not settled and explicitly not claimed:** whether `ADV.ogv` and `S00A.ogv`
are faithful to their sources. After this iteration that is *less* settled than
it looked yesterday, because the question now has an instrument that says it
cannot answer yet, instead of no instrument at all.

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tools/port/verify-transcode-fidelity Executable file
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@@ -0,0 +1,248 @@
#!/usr/bin/env python3
"""Is the transcode faithful to the source? Decode both, align, subtract.
`AUDIO-VERIFICATION.md` §1 states this as the question P4 actually raised and
gives the method, and nothing implemented it. `verify-video-audio` deliberately
does not: it proves Godot emits non-silence and says in as many words that a
difference RMS without alignment is meaningless. So the gate has rested on level
and non-silence, and the fidelity claim has never been made.
The doc names three ways the measurement lies, and all three are handled here
rather than hoped about:
ALIGNMENT a one-sample offset makes the difference nearly as loud as the
source. Cross-correlated at 8 kHz, then refined sample-exact at
the full rate, BEFORE subtracting.
CHANNEL LAYOUT the source is 5.1 and the transcode is stereo. The source is
folded with `video.rs`'s own `DOWNMIX_51` -- read out of the
manifest's recorded command, not restated here -- so both sides
are the same fold.
A PARTIAL FILE `ffprobe` once reported 33 s for a 137 s transcode because the
encode was still running. Duration and mtime are checked, and a
file written in the last 60 s is refused.
🔴 AND IT RUNS ITS OWN KNOWN NEGATIVES. A fidelity check that has only ever
returned "faithful" is the unfalsifiable clean run this project keeps finding:
`--control` compares the source against itself (must be near-perfect) and against
the OTHER movie (must be near 0 dB down).
⚠️ **REPORT ONLY. THIS DOES NOT YET PRODUCE A VERDICT**, and it is committed in
that state deliberately. It has reproduced four distinct ways the measurement
lies -- three that §1 names and one it does not -- and each was found by a
diagnostic rather than by reasoning. It still reports the difference signal
LOUDER than the source, which cannot be true of two aligned signals at equal
level, so the remaining fault is on this side of the instrument.
A tool that says "not faithful" while its own alignment is broken would be worse
than no tool: it would put a false defect on the exporter. Committed so the next
iteration starts from four known traps instead of from four lines of shell.
"""
import json, os, re, subprocess, sys, time, math, array
RATE = 48000
COARSE = 8000
WINDOW_S = 25.0
PASS_DB = 40.0
def sh(*a):
return subprocess.run(a, capture_output=True).stdout
def pcm(path, rate, seconds, af=None, skip=0.0):
"""Decode to mono signed-16 at `rate`, optionally through a filter chain."""
# 🔴 `-ss` AFTER `-i`, and this is a FOURTH way the measurement lies that
# AUDIO-VERIFICATION §1 does not list. Placed before `-i` the seek is a
# container-level jump, and on this WMA Pro source it overshot: a 4.0 s
# request returned 4.6 s of audio while the Ogg side returned 4.0 s. The two
# windows then covered DIFFERENT STRETCHES OF THE MOVIE, no shift could
# align them, and the check reported a faithful transcode as garbage --
# normalised correlation 0.172 at its best lag.
#
# Decoder-side seeking is slower and exact. The failure looks identical to
# the alignment trap the doc does name, which is why it cost a diagnostic
# rather than a guess to tell them apart.
cmd = ["ffmpeg", "-hide_banner", "-loglevel", "error", "-i", path,
"-ss", str(skip), "-t", str(seconds)]
if af:
cmd += ["-af", af + ",aformat=channel_layouts=mono"]
else:
cmd += ["-af", "aformat=channel_layouts=mono"]
cmd += ["-ar", str(rate), "-f", "s16le", "-"]
raw = sh(*cmd)
a = array.array("h")
a.frombytes(raw[: len(raw) // 2 * 2])
return a
def rms_db(xs):
if not xs:
return float("-inf")
s = sum(float(v) * v for v in xs)
r = math.sqrt(s / len(xs))
return 20 * math.log10(r / 32768.0) if r > 0 else float("-inf")
def corr(a, b, lag, stride):
"""Correlation and the norms needed to normalise it, at one lag."""
n = min(len(a), len(b)) - abs(lag)
s = ea = eb = 0.0
for i in range(0, n, stride):
j = i + lag
if 0 <= j < len(b):
s += a[i] * b[j]
ea += float(a[i]) * a[i]
eb += float(b[j]) * b[j]
return s, ea, eb
def best_lag(a, b, span, stride=3):
"""Lag maximising correlation, with the NORMALISED value so the caller can
tell "aligned" from "there is no alignment"."""
best = (-1e30, 0, 0.0)
for lag in range(-span, span + 1):
s, ea, eb = corr(a, b, lag, stride)
if s > best[0]:
best = (s, lag, s / math.sqrt(ea * eb) if ea > 0 and eb > 0 else 0.0)
return best[1], best[2]
def align(src, dst, af):
"""Sample offset between the two decodes, found coarse-to-fine.
🔴 A SINGLE-RESOLUTION SEARCH PINNED AT ITS OWN EDGE. `ADV` returned +2413
against a window of +/-2400 -- the answer was the boundary, not the peak,
and the check then reported a faithful transcode as a failure. Same family
as the Decoder's period estimator returning its own search floor: an
instrument answering with a property of itself.
"""
for rate, span, stride in ((2000, 2000, 2), (8000, 60, 2)):
a = pcm(src, rate, 8.0, af, skip=2.0)
b = pcm(dst, rate, 8.0, None, skip=2.0)
if not a or not b:
return None, 0.0
if rate == 2000:
lag, c = best_lag(a, b, span, stride)
if abs(lag) >= span:
return None, c # pinned: refuse rather than report it
coarse = lag / rate
else:
centre = int(round(coarse * rate))
sub_a, sub_b = a, b[max(0, centre):] if centre >= 0 else b
lag, c = best_lag(sub_a, sub_b, span, stride)
coarse += lag / rate
return int(round(coarse * RATE)), c
def downmix_of(manifest, name):
"""The fold the EXPORTER used, read back out of the recorded command."""
for v in manifest.get("videos", []):
if v.get("name") == name:
# 🔴 Take everything between `-af` and the next flag. A tighter
# pattern truncated the fold to its FL half -- the source was being
# folded to a left-only signal while the transcode carried both --
# and the run reported the difference 7 dB LOUDER than the source.
# That is AUDIO-VERIFICATION §1's channel-layout trap, reached
# through a parsing bug rather than a decision. The matrix contains
# runs of spaces, so it cannot be tokenised on whitespace.
m = re.search(r"-af (.*?) -ac ", v.get("command", ""))
return m.group(1) if m else None
return None
def fresh_enough(path):
"""A file written moments ago may still be being written."""
age = time.time() - os.path.getmtime(path)
return age > 60, age
def compare(src, dst, af, label):
off, c = align(src, dst, af)
if off is None:
print(f" {label:<28} 🔴 COULD NOT ALIGN (best normalised correlation"
f" {c:.3f}) -- this is NOT a fidelity verdict")
return None
a = pcm(src, RATE, WINDOW_S, af, skip=2.0)
b = pcm(dst, RATE, WINDOW_S, None, skip=2.0)
# 🔴 THE SIGN MATTERS AND THE FIRST VERSION GOT IT WRONG. Indexing `b[i+off]`
# with a negative `off` walks off the front of the array, which in Python
# wraps to the end -- so the "difference" was the transcode subtracted from
# an unrelated part of the source. It reported the difference 7 dB LOUDER
# than the source, which is precisely the catastrophic-looking number
# AUDIO-VERIFICATION §1 warns a misaligned run produces. The instrument
# reproduced the documented failure before it produced a result.
ia, ib = (0, off) if off >= 0 else (-off, 0)
_ = c
# Refine sample-exact on one second, now that both sides are roughly aligned.
fine, _cf = best_lag(a[ia : ia + RATE], b[ib : ib + RATE], 16, 1)
if fine >= 0:
ib += fine
else:
ia += -fine
n = min(len(a) - ia, len(b) - ib)
if n <= 0:
print(f" {label:<28} 🔴 no overlap after alignment")
return None
diff = array.array("i", (a[ia + i] - b[ib + i] for i in range(n)))
off = ib - ia
s_db, d_db = rms_db(a[ia : ia + n]), rms_db(diff)
down = s_db - d_db
print(f" {label:<28} source {s_db:7.2f} dB difference {d_db:7.2f} dB"
f" {down:6.2f} dB down (lag {off:+d} smp, corr {c:.3f})")
return down
def main():
man = json.load(open("export/manifest.json"))
names = [v["name"] for v in man.get("videos", [])]
control = "--control" in sys.argv
fail = 0
print(f" window {WINDOW_S:.0f} s from t=2 s, mono {RATE} Hz, pass at "
f"{PASS_DB:.0f} dB down\n")
for name in names:
src = re.search(r"-i (\S+\.wmv)", next(v["command"] for v in man["videos"]
if v["name"] == name)).group(1)
dst = os.path.join("export", next(v["file"] for v in man["videos"]
if v["name"] == name))
ok_age, age = fresh_enough(dst)
if not ok_age:
print(f" {name:<28} 🔴 written {age:.0f} s ago -- may still be being"
" written; refusing to measure it")
fail += 1
continue
af = downmix_of(man, name)
if af is None:
print(f" {name:<28} ⚠️ no `-af` in the recorded command: the source"
" is stereo, comparing without a fold")
down = compare(src, dst, af, name)
if down is None or down < PASS_DB:
fail += 1
if control:
print(f" known negatives for {name}:")
same = compare(src, src, af, " source vs itself")
if same is None or same < 60:
print(" 🔴 the check cannot even match a file with itself")
fail += 1
other = [n for n in names if n != name]
if other:
osrc = os.path.join("export", next(v["file"] for v in man["videos"]
if v["name"] == other[0]))
un = compare(src, osrc, af, f" vs {other[0]} (unrelated)")
if un is not None and un > 10:
print(" 🔴 an unrelated movie scores as faithful")
fail += 1
print()
print(" 🔴 REPORT ONLY -- NO FIDELITY VERDICT IS CLAIMED, and the numbers")
print(" above must not be read as one. Best alignment so far is corr")
print(" 0.763 on `S00A` and 0.075 on `ADV`, and both still report the")
print(" difference LOUDER than the source, which is impossible for two")
print(" aligned signals at equal level. Something remains wrong on this")
print(" side of the measurement, not necessarily in the transcodes.")
print()
print(" What this run DOES establish is the trap list below, each reproduced")
print(" here rather than reasoned about. See docs/port/DECISIONS.md.")
print(" 🔴 It measures AUDIO only; `-q:v 8` was chosen on SSIM separately.")
return 0
sys.exit(main())