Claude
6ac126e05c
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).
21 lines
789 B
Python
21 lines
789 B
Python
"""Walk blocks of the new 5-11-26 events and look at what comes after Tran block."""
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import sys
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sys.path.insert(0, ".")
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from minimateplus.waveform_codec import walk_body, find_data_start
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def main():
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for stem in ("M529LL1A.SP0", "M529LL1A.SS0", "M529LL1A.SV0"):
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with open(f"decode-re/5-11-26/{stem}", "rb") as f:
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raw = f.read()
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body = raw[43:-26]
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start = find_data_start(body)
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blocks = walk_body(body, start)
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print(f"\n=== {stem} === body={len(body)} start={start} blocks walked={len(blocks)}")
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for i, b in enumerate(blocks[:20]):
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print(f" block[{i:>2}] @ {b.offset:>5} tag={b.tag_hi:02x} NN=0x{b.tag_lo:02x}({b.tag_lo}) len={b.length} data[:24]={b.data[:24].hex(' ')}")
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if __name__ == "__main__":
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main()
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