the BE9558 / BE18003 extension-byte case
The bytes at [7]/[11]/[15]/[19] are an annotation field (purpose still
unclear — empirically non-zero on intervals with sub-Hz or unmeasurable
freq), NOT the high byte of the peak count. The N844 fixture corpus
the original RE was done against had zero values in those bytes for
every block, so uint8 and uint16 LE were equivalent there — but on
real BE9558 Tran-drift events and BE18003 Histogram+Continuous events
the uint16 LE interpretation produced peaks up to 268 in/s and 35×
inflated PVS sums.
Cross-correlated against BW's per-interval ASCII export on:
- K558LKZU/LL1P/LL3K → 100% T/V/L/M peak match (1435 blocks each)
- T003LKZR/LL0O/LL1M → 100% T/V/L, 99.3% M (0.05 dB rounding only)
- N599LKZS/LL0L → 100% all channels
- N844 fixture corpus → 100% all channels (unchanged)
Annotations preserved on every record for future RE; the defensive
_MAX_PEAK_COUNT bound is no longer needed (uint8 maxes at 1.275 in/s,
well below any physical limit).
Synthetic regression test added using the verbatim K558LKZU.RE0H
interval-12 block.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
histogram_codec: drop _MAX_PEAK_COUNT 4096 → 2200. The old ceiling
let extension-byte blocks slip through at up to 20.48 in/s per
channel, producing 35× inflated PVS sums when first deployed to
prod. 2200 covers Normal-range full-scale (10 in/s = 2000 counts)
plus 10% headroom for quantization edge cases.
backfill_sidecars: also preserve the bw_report block alongside
review + extensions when regenerating sidecars. event_to_sidecar_dict
takes a BwAsciiReport dataclass not a dict, so for bw_report we
overlay the existing block after regen rather than passing as a kwarg.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Discovered while running the backfill on prod: certain histogram
blocks contain an undocumented extension byte format whose naive
uint16 LE interpretation yields physically impossible peak values
(150+ in/s when the device max is 10). Concrete example from
K558LKSG.3I0H block at body+7424:
bytes [6:10] = 05 79 69 00
current code: T_peak = uint16 LE = 0x7905 = 30981 → 154.9 in/s
reality: T_peak = byte[6] = 5 → 0.025 in/s (matches BW display)
The high byte (0x79 here) appears to be an extension field — possibly
"time of peak within interval" or a Histogram+Continuous sub-mode
marker. Observed across BE9558 and BE18003 units in prod data; never
appeared in the BE12844 fixture corpus the codec was originally
verified against.
Effect on prod: 26 out of 1433 blocks in this one event had inflated
peaks, plus dozens of similar events across the fleet → sum(PVS)
inflated from baseline 988 to 34501 (35x). Rolled back via the
pre-backfill snapshot before any UI exposure.
Defensive fix: bounds-check peak counts in `_decode_block`. Any
field exceeding `_MAX_PEAK_COUNT` (4096 = ~20 in/s, well past the
device's 10 in/s Normal-range FS) causes the block to be skipped
entirely. Other valid blocks in the same event still decode
correctly.
Trade-off: those skipped blocks lose their per-interval data
(peaks + frequencies). Acceptable until the extension format is
reverse-engineered — better than propagating bogus values into PVS
computations downstream.
The 24 existing tests all still pass — the fixtures used during the
original codec development don't exercise the extension-byte case.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The histogram-mode event body is now byte-exact decodable.
Companion to the waveform body codec — together they cover every
event file the watcher forwards. Cracked in one session via
cross-event correlation against BW's ASCII export.
The §7.6.2 spec in instantel_protocol_reference.md was structurally
correct (32-byte blocks) but the per-sample semantics were
under-documented. Cross-checking block 130 of N844L6Z8.ZR0H
against its TXT row revealed the layout perfectly:
slot[0] = 10 (constant marker)
slot[1] = T_peak_count (× 0.005 → in/s at Normal range)
slot[2] = T_halfperiod (freq_Hz = 512 / halfp)
slot[3] = V_peak_count
slot[4] = V_halfperiod
slot[5] = L_peak_count
slot[6] = L_halfperiod
slot[7] = MicL_peak_count (dB via waveform_codec.mic_count_to_db)
slot[8] = MicL_halfperiod
The `>100 Hz` sentinel is halfperiod ≤ 5 (since 512/5 = 100 Hz).
Mic dB uses the SAME formula as the waveform codec (sign × (81.94
+ 20·log10(|count|))) — they share the mic ADC calibration constant.
Block identification anchor: bytes [22:24] == 0x0000 AND
bytes [28:32] == 1e 0a 00 00. The tail signature is the most
reliable distinguisher from non-block content in the file.
Files:
minimateplus/histogram_codec.py (new) — decoder + public API
matching the waveform codec's shape:
walk_body(body) -> records
decode_histogram_body(body) -> {Tran, Vert, Long, MicL}
decode_histogram_body_full(body) -> [per-interval dicts]
half_period_to_hz, geo_count_to_ins helpers
minimateplus/event_file_io.py (modified) — read_blastware_file
now tries the waveform codec first, falls back to the histogram
codec on failure. Same output shape, same downstream pipeline.
tests/test_histogram_codec.py (new) — 24 regression locks against
the in-repo fixture corpus, byte-exact against BW ASCII export
for peaks (all 4 channels), frequencies (all 4 channels,
including >100 Hz sentinel handling), block framing, and
segment-ID accounting.
scripts/backfill_sidecars.py (modified) — the has_samples
short-circuit added in the histogram-pending era is now a
pure defensive guard. Histograms in prod will regen .h5 files
correctly on the next backfill run.
docs/histogram_codec_re_status.md (updated) — supersedes the
earlier "in progress" version with the verified format and
test-coverage summary. Notes a few non-essential fields still
open (4-byte block metadata, Geo PVS, Mic psi(L) — none of
which are needed for waveform reconstruction).
Total verified coverage: ~3,500 blocks across 5 fixtures, every
field of every block byte-exact against BW.
The watcher-forwarded histogram event corpus on prod (~10,000
events) will now produce correct .h5 sidecars on the next backfill
run. No additional changes needed to the backfill flow — the
existing tool_version-bump cascade picks them up automatically.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
serversdown