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).
Claude