detect_multi_interval_stride() confirmed a candidate stride on a third block
header whenever the body was long enough to contain one. But a body can exceed
two strides and still hold only two real blocks: a partial final block leaves
trailing padding. BE18193 T193L0XM.CI0H — 51 intervals at 2 s, i.e. one full
30-interval block plus a 21-interval remainder in a 2787-byte body — had every
decisive check pass at stride 612 (header at 0, header at 612, block counter
256 -> 257) and was then rejected for the absent third header at 1224. It
decoded to nothing.
A missing third header now means end-of-stream rather than disqualification.
The block-counter check is untouched — that is the test that prevents the
false positives which once handed 9,082 standard-block files to the
multi-interval walker.
Found by running the full DL2 archive against its preserved Blastware ASCII
exports (14,340 paired files, 11x the previous ground-truth corpus).
Measured over 127,035 archive histogram binaries:
recovered 8 files (strides 92, 252, 612; BE18193, BE18191, BE9557, BE9440)
regressed 0 files
Full-corpus verification: 14,337 -> 14,338 exact of 14,338 decodable pairs
(the 2 excluded are series-4 IDF, a different codec).
Also adds scratch/verify_against_ascii.py (per-sample decoder verification
against BW exports, with a saturation carve-out — BW clamps clipped events to
the range max while the decoder reports true counts) and scratch/offset_scan.py.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
274 series-3 waveform events across 6 episodes on 2 units (BE9558,
BE18438) whose dominant geo axis sits pinned at a DC offset above that
unit's own geo trigger level — the "offset" hardware fault that makes a
unit retrigger continuously and flood the ACH queue.
Detection rule: dominant-axis |mean|/peak > 0.7 AND |mean| >= 0.9 x the
unit's geo trigger level. Bare |mean|/peak is useless on quiet events —
a trace at the 0.010 in/s noise floor clears any ratio threshold.
Not a decode artifact: these reproduce exactly in Blastware's own ASCII
export. Kept as the starting point for the archive-wide analysis.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
The segment-channel scoring analyzer (from scratch/next_experiment_skeleton.py)
ran and immediately confirmed the rotation hypothesis:
SP0 seg 0: best fit Vert 508/508 ✓
SP0 seg 1: best fit Long 508/508 ✓
SP0 seg 3: best fit Tran 508/508 ✓ (Tran continuation)
SP0 seg 5: best fit Long 508/508 ✓
SP0 seg 9: best fit Long 508/508 ✓
V70 seg 0: best fit Vert 508/508 ✓
V70 seg 1: best fit Long 508/508 ✓
Channels rotate Tran → Vert → Long → MicL per 40 02 segment header.
Also discovered the segment header has DOUBLE duty: bytes [14:18] anchor
the NEW segment's channel (2 samples as int16 BE in 16-count units), AND
bytes [0:4] extend the PREVIOUS channel by 2 more samples (2 deltas as
int16 BE). This is the same "2 anchors + delta stream" structure as the
body preamble for Tran.
decode_waveform_v2 now returns full per-channel sample dicts.
Byte-exact verified ranges:
V70: Tran 512, Vert 512, Long 512 (all first segments)
JQ0: Tran 512, Vert 258
SP0: Long 1536 (all 3 L segments)
Still open: the 30 NN block format (high-amplitude packed deltas) —
appears mid-segment when single-byte deltas can't carry the magnitude.
6 new tests bring the count to 46. All passing.
Three things to make pickup smoother:
1. analysis/README.md (NEW): catalogues the ~25 scratch scripts.
Categorizes them as "still useful" / "superseded — keep for
archaeology" / "pure exploration". Tells a fresh engineer which
files to read first and which to ignore.
2. scratch/next_experiment_skeleton.py (NEW): stub + spec for the
segment-channel scoring analyzer. Includes the fixture loader,
block walker, and decode-segment-as-channel helper — just enough
scaffolding that the next pass starts from "fill in
score_segment_against_all_channels()" rather than from scratch.
Already runs and confirms 13 segments per 3-sec event with sample
starts going to 6590 (way past the 3328 actual samples) — strong
evidence that not all segments carry Tran.
3. Removed decode-re/ duplicate. It was a mirror of tests/fixtures/.
Analysis scripts that hardcoded decode-re/ paths updated to point
at tests/fixtures/. CLAUDE.md note updated: future event uploads
go directly into a dated subdirectory under tests/fixtures/.
All 40 tests still pass. Skeleton runs.
serversdownandClaude Opus 5