The DL2 export keeps a byte-identical `Sent/` copy of its root, so walking it
counts every binary twice: 127,035 histogram paths are 63,535 distinct files,
and 13,077 waveform paths are 6,577. offset_scan.py now keeps the first
occurrence of each basename.
Corrects the previous commit's changelog claim of 8 recovered files — it is 4:
K440HJCN.3C0H and K557IF1U.8K0H (stride 252), T191HVNP.0S0H (92), T193L0XM.CI0H
(612). Still zero regressions. The per-unit breakdown reading exactly 2-2-2-2
should have given the doubling away.
The 14,338-exact verification result is unaffected: ASCII exports are not
mirrored (14,340 paths, 14,340 distinct names), and the harness enumerates
those rather than the binaries.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
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
serversdownandClaude Opus 5