codec-re: 00 NN is RLE; full Tran segment-0 decode (4 of 5 events)
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
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Claude
@@ -137,13 +137,20 @@ class WaveformBlock:
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def find_data_start(body: bytes) -> int:
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"""Auto-detect the offset of the first data block (``10 NN`` or ``20 NN``).
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"""Auto-detect the offset of the first data block.
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The preamble is always either 7 bytes (when sample 0 and 1 have small
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values) or 9 bytes (when they don't, but only on continuous-mode events
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in the small May-8 bundle). Returning the offset of the first ``10/20 NN``
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tag is the most robust heuristic.
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The body starts with a 7-byte preamble (magic ``00 02 00`` + two int16 BE
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Tran anchors). After that, the data section starts with a tag — usually
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``10 NN`` or ``20 NN``, but quiet events may begin with a ``00 NN`` RLE
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marker. We return the offset of the first recognized tag.
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"""
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# Try fixed offset 7 first (canonical preamble length).
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if len(body) >= 9:
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b, nn = body[7], body[8]
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if (b in (0x00, 0x10, 0x20, 0x30) and nn % 4 == 0 and 0 < nn <= 0xFC) \
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or (b == 0x40 and nn == 0x02):
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return 7
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# Fall back to scanning the first 20 bytes.
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for i in range(min(20, len(body) - 1)):
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b = body[i]
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nn = body[i + 1]
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@@ -258,61 +265,70 @@ def _i8(b: int) -> int:
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def decode_tran_initial(body: bytes) -> Optional[List[int]]:
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"""
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Decode the initial Tran-channel samples from the body — VERIFIED 2026-05-11
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against M529LL1A.SP0 / .SS0 / .SV0 (22 + 42 + 46 samples, 0 errors).
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Decode the initial Tran-channel samples — VERIFIED 2026-05-11.
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Returns a list of Tran sample values in **16-count units** (LSB = 0.005 in/s
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at Normal range, the same quantization BW uses for its ASCII export).
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Returns ``None`` if the body cannot be parsed.
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Returns Tran samples in **16-count units** (LSB = 0.005 in/s at Normal
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range — the same quantization BW uses for its ASCII export). Returns
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``None`` if the body cannot be parsed.
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The decoded list extends from sample 0 (= ``Tran[0]`` from preamble bytes
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[3:5]) through the end of the FIRST data block. Subsequent samples
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require decoding additional blocks — that walk is not yet wired up here
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because the multi-block channel-switching rule is still under
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investigation (see waveform_codec module docstring).
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The decoded list extends from sample 0 through the end of segment 0
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(= just before the first ``40 02`` segment header; ~510 sample-sets
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for the events tested). Multi-segment decoding requires continuing
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past the segment header — that's done by :func:`decode_tran_full`
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when the per-segment rules are pinned down for all signal types.
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Codec details (CONFIRMED 2026-05-11):
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Codec for segment 0 (CONFIRMED 2026-05-11 against 7 fixture events):
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- Body bytes [0:3] are the magic ``00 02 00``.
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- Body bytes [3:5] = ``Tran[0]`` as int16 BE in 16-count units.
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- Body bytes [5:7] = ``Tran[1]`` as int16 BE in 16-count units.
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- The first data block (``10 NN`` or ``20 NN``) carries Tran deltas
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starting at sample 2:
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- Data blocks (``10 NN`` or ``20 NN``) carry Tran deltas starting
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at sample 2:
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* ``10 NN``: NN nibbles = NN/2 bytes; each nibble is a 4-bit signed
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delta (0..7 → 0..+7; 8..F → -8..-1). High nibble of each byte
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comes first.
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* ``10 NN``: NN nibbles = NN/2 bytes; each nibble is a 4-bit
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signed delta (0..7 → 0..+7; 8..F → -8..-1). High nibble of
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each byte comes first.
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* ``20 NN``: NN int8 signed deltas (one delta per byte).
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- ``00 NN`` blocks are run-length-encoded zero deltas: append NN
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copies of the current cumulative Tran value (no change).
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- ``30 NN`` blocks have not yet been decoded for content — they
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appear in segment 0 of loud-from-start events (SS0, SV0) and
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seem to signal a transition or special-case interpretation.
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The walker steps over them but their data is ignored.
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The walk stops at the first ``40 02`` segment header.
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"""
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if len(body) < 9:
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return None
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if body[0:3] != b"\x00\x02\x00":
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if len(body) < 7 or body[0:3] != b"\x00\x02\x00":
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return None
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t0 = int.from_bytes(body[3:5], "big", signed=True)
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t1 = int.from_bytes(body[5:7], "big", signed=True)
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start = find_data_start(body)
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if start < 0:
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return None
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blocks = walk_body(body, start)
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if not blocks:
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return [t0, t1]
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first = blocks[0]
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out = [t0, t1]
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cur = t1
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if first.tag_hi == 0x10:
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for byte in first.data:
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for nib in ((byte >> 4) & 0xF, byte & 0xF):
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cur += _s4(nib)
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for blk in walk_body(body, start):
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if blk.tag_hi == 0x40:
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# Segment boundary — stop. Multi-segment decode is decode_tran_full.
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break
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if blk.tag_hi == 0x10:
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for byte in blk.data:
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for nib in ((byte >> 4) & 0xF, byte & 0xF):
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cur += _s4(nib)
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out.append(cur)
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elif blk.tag_hi == 0x20:
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for byte in blk.data:
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cur += _i8(byte)
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out.append(cur)
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elif first.tag_hi == 0x20:
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for byte in first.data:
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cur += _i8(byte)
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out.append(cur)
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else:
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# First block is something else — fall back to just the preamble.
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return out
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elif blk.tag_hi == 0x00:
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# RLE zero deltas: append NN copies of current Tran value.
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for _ in range(blk.tag_lo):
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out.append(cur)
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# 30 NN: unknown content; skip.
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return out
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