Verified against a second Thor corpus (9-10-26-csv-req: UM11402, UM12947,
UM20147) with per-sample CSV exports: 139/139 waveforms exact
(1,273,380/1,273,380 samples) and 877/877 histograms within 2% of Thor's
reported PPV -- up from 66.9% and 56.6%.
Some units run with the microphone disabled, which changes two structural
things that were both hardcoded to the 4-channel shape:
- Waveform body head sat below the scan floor. A 3-channel unit has a
shorter fixed header and puts its record chain head at 0x0dba, under the
old _BODY_SCAN_FLOOR of 0x0E00. The scan could not see it and fell
through to the Vert segment-0 record, decoding a body shifted one
position around the channel rotation -- Vert came up exactly 512 samples
short. Floor lowered to 0x0C00. The body-offset scoring also had to stop
requiring four channels, or `equal` is permanently False for these events
and the pick falls back to raw sample count.
- Histogram interval record is 56 bytes, not 72. It is
16 * n_channels + 8, and is not inferable from the segment length alone.
The interval count now comes from the segment's cumulative counter
(n = counter - prev_counter) and the stride is derived from it. Assuming
72 read 7 intervals out of every 10-interval segment, then walked off
alignment into garbage that decoded as ~10 in/s peaks -- inflating some
files' PPV by up to 191,000%. Also recovers 4 files that previously
decoded no intervals at all.
Combined across both corpora: 292/292 waveform files,
2,330,916/2,330,916 samples exact. Production IDFW truncations 41 -> 22.
Series-3 unaffected (no shared-codec change in this commit; last full run
14,338/14,338).
Known open, diagnosed but NOT verified: the remaining 22 unequal + 1 failing
production IDFW files (all UM12947, 2025-07-14..09-23) stop the block walker
on tag 40 0c. data_block_len() caps the 40 NN int16 block at NN > 0x08 while
those files use NN up to 196. Both verified corpora only ever use
NN in {1,2,3,4,8}, so the cap is untested there and lifting it leaves both at
100.000% -- which is not evidence it decodes these correctly. Deliberately
not shipped; needs Thor CSV exports for UM12947 in that date range.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
Verified against Thor's own CSV exports, which carry a per-sample
four-column block beside every binary (CSV/<name>.IDFW.csv). Those 1,012
paired files were in the corpus all along; the decoder had been pinned to
a superseded walker on the stated grounds that "Thor has no ASCII ground
truth in the corpus and its geo scaling is separately suspect". Both
premises were false.
IDFW per-sample exact 39.1% -> 100.000% (1,057,536/1,057,536)
IDFW files fully exact 0/153 -> 153/153
IDFW PPV median error -3.32% -> -0.002%
IDFH within 2% of Thor PPV 51.1% -> 100.0% (858/858)
prod IDFW, 8 units -3.3% -> -0.001%
Four independent root causes:
- Geo LSB was 0.0003, the 4-dp *display rounding* of the real
0.000310308 mistaken for the LSB, so every series-4 geophone sample
read 3.3% low. Pinned to +-6e-11 by intersecting 991,415 rounding
constraints; corroborated by the +-full-scale seed (+-32226) left in
unwritten IDFH slots. IDFH had a separate, also wrong, 10.0/32768.
- IDFH histograms were capped at 250 intervals: the segment validator
required the interval counter's high byte to be zero, but the counter
is a uint16 cumulative index, so every segment past interval 255 was
rejected. Runs over ~4 hours lost their tail, often the peak.
540/858 corpus files affected.
- Record mode 00 00 (raw int16, 10-byte header) was unhandled and fell
through the dispatch, silently dropping each channel's first 512
samples -- the long-standing "loud events truncate" symptom.
MODE_ABSOLUTE is now also accepted as a segment-0 preamble.
- The body-offset search matched 00 02 00 *inside* record headers,
selecting a candidate part-way down the chain and decoding a
rotation-shifted body. It now anchors on record headers and takes the
chain head (6 ms/file).
Also fixes the separately tracked "UM-series decodes ~1000x low" bug.
Series-3 re-verified unchanged at 14,338/14,338 exact after the shared
waveform_codec change.
Known open: 41/575 prod IDFW files (7%, mostly UM12947/UM20147) decode
with unequal channel lengths and also fail metadata extraction -- a
different header variant with no Thor export in the store.
NOTE: this is a codec change; the Thor store owes a regeneration via
scripts/backfill_thor_events.py.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
serversdownandClaude Opus 5