channel_spectrum(samples, sps) → the single-sided amplitude spectrum Blastware's
FFT Report draws, and dominant_frequency() picks its peak in the 2–250 Hz band.
Reverse-engineered against 7 BE12844 (MiniMate Plus) events with Blastware FFT
reports as ground truth. Recipe: DC-remove, NO window (a window smears the peak
and worsens the match), zero-pad to 4096 (→ 0.25 Hz bins at 1024 sps — the
resolution every reported dominant frequency lands on), single-sided 2/N
amplitude. Reproduces Blastware's dominant frequency to the exact bin on all
28 channels and the amplitude to report precision.
This is the missing piece for both the USBM RI8507 compliance chart (its scatter
is these (freq, amp) points vs the limit curve) and the FFT view.
Pure numpy, series-agnostic (feed it in/s samples from either decoder). The 7
events land in tests/fixtures as the oracle (force-added past the fixtures
gitignore, matching 5-11-26 / decode-re-5-8-26).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDXjZCr4RqT2U3QvMDhgzf
User uploaded a Vert-heavy event (JQ0) and a Mic-heavy event (V70).
Those two were exactly what was needed to crack the next piece:
- 00 NN block = run-length-encoded zero deltas in the current channel.
Append NN copies of the current cumulative value (no change).
- find_data_start now recognizes 00 NN as a valid first tag (some events
begin with a leading 00 NN RLE block).
- decode_tran_initial now decodes the FULL segment 0 (not just the first
data block).
Results across 5 fixture events:
- M529LL1A.SP0 (loud-all-channels) : 510 / 510 ✓
- M529LL1L.JQ0 (Vert-heavy) : 510 / 510 ✓
- M529LL1L.V70 (Mic-heavy) : 510 / 510 ✓
- M529LL1A.SV0 (loud-from-start) : 58 / 58 ✓
- M529LL1A.SS0 (loud-from-start) : 42 / 502 (stops at first 30 04)
The 30 04 block (only seen in loud-from-start events) hasn't been
decoded yet — likely a channel-switch marker for the high-amplitude
regime.
Also discovered: segment header (40 02) payload bytes [0:2] = T_delta
at first sample of new segment, [6:8] = byte length to next segment.
Multi-segment Tran decoding still diverges after sample 512 because
the per-segment channel ordering after the header is unknown.
Tests: 40 pass (up from 36).
Files:
- minimateplus/waveform_codec.py: find_data_start fix, RLE handling,
full segment-0 decode in decode_tran_initial
- tests/test_waveform_codec.py: synthetic RLE test, full segment 0
tests for JQ0 and V70
- tests/fixtures/5-11-26/: M529LL1L.JQ0, M529LL1L.V70 + TXT exports
- docs/instantel_protocol_reference.md §7.6.1: RLE + segment-header docs
User uploaded 3 high-amplitude events (PPV 6-7 in/s — shook the geophone
hard) to decode-re/5-11-26/. These cracked the Tran codec:
- Preamble bytes [3:5] and [5:7] = Tran[0] and Tran[1] as int16 BE
in 16-count units (LSB = 0.005 in/s). Confirmed across all 7
fixtures.
- First data block carries Tran deltas from sample 2 onward:
* 10 NN block: NN/2 bytes of payload, each byte = two 4-bit signed
nibble deltas (high nibble first)
* 20 NN block: NN int8 signed deltas
Verified 22+42+46 = 110 Tran samples across SP0/SS0/SV0 with 0 errors
against BW's ASCII export.
Why the earlier 96-combination brute force failed: the quiet 5-8
events all had T[0] = T[1] ≈ 0 so the preamble's per-channel encoding
was undetectable. Loud events made the encoding obvious.
What's solved:
- minimateplus.waveform_codec.decode_tran_initial: returns first
N Tran samples in 16-count units for any body.
- Walker length formula for in-data 30 NN blocks (NN*2 instead of NN*4).
- Walker now handles bodies that start with 20 NN (in addition to 10 NN).
What's still open:
- Tran past the first data block (multi-block channel switching).
- Vert / Long / MicL channel encodings.
- Walker correctness past offset ~427 in event-b.
Tests: 36 pass. decode_waveform_v2 still returns None — the full
multi-channel decoder is not wired up. decode_tran_initial is the
new verified entry point.
Files: minimateplus/waveform_codec.py, tests/test_waveform_codec.py
(adds 5-11-26 fixtures + decode_tran_initial tests), and
docs/instantel_protocol_reference.md §7.6.1 (Tran codec spec).
Decoded the structural framing of the Blastware waveform body — the bytes
between the 21-byte STRT record and the 26-byte file footer. The body is
a sequence of tagged variable-length blocks, NOT raw int16 LE. Five tag
types (10/20/00/30/40 NN) and their lengths are now confirmed against the
4-event May 2026 fixture bundle. Body splits cleanly into ~16 segments
(for a 1280-sample event) separated by 40 02 segment headers carrying a
monotonically incrementing uint32 LE counter at bytes [8:12].
What's done:
- minimateplus/waveform_codec.py — block walker, segment splitter, segment
header parser. decode_waveform_v2 is a stub returning None until the
byte-to-sample mapping is solved; client.py is unchanged.
- tests/test_waveform_codec.py — 31 tests covering block detection, lengths,
contiguous-walk, segment splitting, segment-header parsing, and counter
monotonicity. All pass.
- tests/fixtures/decode-re-5-8-26/ — bundled fixtures (4 events, BW binary
+ Blastware ASCII export each).
- docs/instantel_protocol_reference.md §7.6.1 — replaced retraction box
with the verified structural decoding plus an explicit list of what's
still open.
What's still open: the per-byte mapping inside 10 NN / 20 NN blocks. 96
channel-permutation × nibble-order × sign-convention combinations were
brute-force tested; none match BW's ASCII export to within ±1 ADC count.
The codec is more elaborate than uniform 4-bit deltas — likely a hybrid
variable-bit-width scheme with segment-anchor resync points. Next
recommended step: capture an event with a known calibration tone to pin
down magnitude scaling.
Walker also bails out partway through event-b (open issue documented in
both the module and the protocol reference).
serversdownandClaude Opus 4.8