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codec-re: 00 NN is RLE; full Tran segment-0 decode (4 of 5 events)

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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
This commit is contained in:
Claude
2026-05-11 22:29:07 +00:00
committed by serversdown
parent 6ac126e05c
commit a0c9a482c7
10 changed files with 7195 additions and 62 deletions
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docs/instantel_protocol_reference.md
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@@ -971,28 +971,64 @@ in the form ``f3/f4/f5`` near ``20 10`` markers strongly resemble
int8 channel-bias values around -12). Detailed decoding of the
trailer is outside the path needed for sample reconstruction.
##### Tran channel codec — CONFIRMED 2026-05-11
##### Tran channel codec — CONFIRMED 2026-05-11 (segment 0)
The first data block (immediately after the 7-byte preamble) carries
Tran-channel deltas starting at sample 2. Two block types in alternation:
After the 7-byte preamble, the body's segment 0 carries Tran deltas
via three block types:
- ``10 NN``: ``NN/2`` bytes of payload. Each byte = two 4-bit signed
nibbles (high nibble first; 0..7 → 0..+7, 8..F → -8..-1). Each
nibble is one Tran delta in 16-count units.
nibble is one Tran delta in 16-count units (LSB = 0.005 in/s).
- ``20 NN``: ``NN`` bytes of payload. Each byte = one int8 signed delta
in 16-count units.
- ``20 NN``: ``NN`` bytes of payload. Each byte = one int8 signed
delta in 16-count units. Used when deltas don't fit in 4 bits.
Verified against all 3 May-11 fixture events:
- ``00 NN``: a 2-byte marker. Run-length-encoded zero deltas — append
NN copies of the current cumulative Tran value (no change). Used
heavily for silent stretches.
| Event | First block | # T samples decoded | Matches truth |
Segment 0 ends at the first ``40 02`` segment header. Segment 0 typically
covers ~510 sample-sets for events with mostly-quiet Tran, fewer for
events with rapid Tran changes.
Verified against all bundled fixture events (5-8 and 5-11 bundles):
| Event | Tran character | Segment 0 size | Matches truth |
|---|---|---|---|
| SP0 | ``10 14`` (10 bytes / 20 nibbles) | 22 (= 2 preamble + 20 deltas) | 22/22 ✓ |
| SS0 | ``10 28`` (20 bytes / 40 nibbles) | 42 | 42/42 ✓ |
| SV0 | ``20 2c`` (44 int8 bytes) | 46 | 46/46 ✓ |
| SP0 (loud all-channels, pretrig=0.25s) | small near sample 0 | 510 | 510/510 ✓ |
| SS0 (loud-from-start) | big from sample 0 | 42* | 42/42 ✓ |
| SV0 (loud-from-start) | big from sample 0 | 58* | 58/58 ✓ |
| JQ0 (Vert-heavy) | near zero | 510 | 510/510 ✓ |
| V70 (Mic-heavy) | near zero | 510 | 510/510 ✓ |
\* SS0 and SV0 decode stops early because their segment 0 contains
``30 04`` blocks whose internal format hasn't been decoded yet (likely
a channel-switch marker for the high-amplitude regime). The two events
where the codec is most complex stop at the first ``30 04``.
Implementation: :func:`minimateplus.waveform_codec.decode_tran_initial`.
##### Segment header T-delta (PARTIAL 2026-05-11)
The 20-byte ``40 02`` segment header has its first 2 bytes ([0:2] of
payload) as an int16 BE Tran delta for the first sample of the new
segment. Verified across V70 (3 segments with 0 deltas) and SP0/JQ0
(1 segment with +1 delta). Other bytes of the segment header payload
are partially understood:
| Payload offset | Field | Status |
|---|---|---|
| [0:2] | T_delta at first sample of new segment (int16 BE) | ✅ confirmed |
| [2:4] | unknown (often 0; not a simple V or T delta) | ❓ open |
| [4:6] | unknown (varies per event; possibly a checksum) | ❓ open |
| [6:8] | byte length to next segment header − 2 (uint16 BE) | ✅ confirmed |
| [8:12] | monotonic uint32 LE counter | ✅ confirmed |
| [12:14] | constant ``02 00`` | ✅ confirmed |
| [14:18] | unknown 4-byte field | ❓ open |
Multi-segment Tran decoding diverges after sample ~512 — the per-segment
channel ordering after the header is still unknown.
##### What's still open
- **Tran past the first data block.** After the first block, the