Sub-minute histogram intervals are packed several to a block so that
every block still covers exactly one minute of data:
interval intervals/block stride
1 minute 1 32 <- the standard big-endian block
15 s 4 92
2 s 30 612
stride = 12 + n * 20
Block = [00][segment][ctr uint16 LE][0a][00], then n x 20-byte records of
8 x uint16 LITTLE-endian values (T_peak, T_halfp, V_peak, V_halfp,
L_peak, L_halfp, M_peak, M_halfp) plus a 2-word tail whose first word is
0000 on every real interval, then a 6-byte block trailer.
The standard 32-byte block is BIG-endian; this variant is LITTLE-endian.
The tail-word check matters: a session ending mid-block leaves buffer
garbage in the remaining interval slots, which decoded as peaks
thousands of times the real value. Stride detection also requires at
least 2 records, since a 1-record block would have stride 32 and
collide with the standard block.
Recovers 415 files that decoded to nothing: 216 on BE18193 (2 s
intervals) and 199 on BE9440 (15 s). Before decoding to nothing they
were being accepted by the WAVEFORM codec, which returned garbage
peaking up to 400x the device-reported PPV.
Ground truth BE9440/K440L3AQ.T70H (5,710 intervals) matches its
Blastware ASCII export exactly: 17,130/17,130 geo peaks, 22,840/22,840
frequencies, 5,710/5,710 mic dB(L). Across all 455 affected files,
1,354/1,365 channel peaks (99.2%) match the device-reported PPV; the 11
that don't are under-reads on BE9440 where the walk stops early.
Fixture (binary + ASCII) saved under tests/fixtures/, which is
gitignored per repo practice — the ground-truth test skips when absent.
Tests: 258 passed, failure list unchanged from baseline.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog
serversdownandClaude Opus 5
306104354b