Two errors in the series-3 histogram block model, both found by diffing
against the per-interval data table in the preserved Blastware ASCII
exports (1211 files in the prod snapshot — far stronger ground truth
than the header PPV used previously).
1. The block is uniformly BIG-ENDIAN. Peaks and half-periods are uint16
BE (T_peak [5:7], T_halfperiod [7:9], V_peak [9:11], V_halfperiod
[11:13], L_peak [13:15], L_halfperiod [15:17], M_peak [17:19],
M_halfperiod [19:21]); only block_ctr [2:4] is little-endian.
The old uint8-peak model silently CLIPPED any peak above 1.275 in/s:
the final interval of BE18193/T193LQ9K.OE0H reads 8.270 in/s in BW's
export (1654 counts = 0x0676) and decoded as 0x76 = 118 = 0.590.
The byte documented as a per-channel "annotation" was never an
annotation — it is the half-period's high byte, which is exactly why
it was non-zero on the sub-Hz intervals BW renders as "<1.0".
The marker is block[4] alone. Testing [4:6] as a uint16 LE marker
forced block[5] == 0, which is what capped the peak at one byte.
2. The final block of each stream carries tail 9c 06 00 42 instead of
1e 0a 00 00, and holds arbitrary bytes at [21:23]. Rejecting it
dropped the last interval of nearly every histogram — frequently the
interval holding the event peak, so the file's PPV read low.
Verified end to end through the production path: 1211/1211 histograms
decode exactly (interval count + every per-interval peak), plus 842,442
per-interval frequency comparisons with zero mismatches. Previously
1 of 1196 files was fully correct.
decode_histogram_body_full records expose `is_terminal` in place of the
removed `annotations` tuple. +6 tests. No regressions: full-suite
failure list unchanged from baseline.
NOTE: stored histogram .h5 files need regenerating to pick this up.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
serversdownandClaude Opus 5
ef1e99b0a0