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codec-re: 30 NN block CRACKED — codec fully decoded

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User intuition (16-bit) + 12-bit packing hypothesis + the int16 ADC
range constraint led to the final piece.

30 NN block format (CONFIRMED across all 14 blocks in the fixture
bundle):

  NN 12-bit signed deltas packed as NN/4 groups of 6 bytes each.
  Within each group:
    bytes [0:2] = 16 bits = 4 × 4-bit high nibbles (MSB-first)
    bytes [2:6] = 4 × int8 low bytes
    delta[k] = sign_extend_12((high_nibble[k] << 8) | low_byte[k])

  Block length = NN × 1.5 + 2 bytes (tag included).  Earlier walker
  used NN × 4 which is only correct in the TRAILER section.

Why 12-bit:  ±2047 in 16-count units ≈ ±10 in/s = the geophone's
full-scale range at Normal sensitivity.  The codec sizes its widest
delta to cover the worst-case sample-to-sample change.

Results: every decoded sample across all fixture events matches truth
byte-exact.  ZERO divergences.

  event-a:  9984 samples (full event, all 3 geos)
  event-c:  3840 (full event)
  event-d:  3840 (full event)
  JQ0:      9984 (full event)
  V70:      9984 (full event)
  SP0:      5122 (walker stops early on edge cases)
  SS0:      1758
  SV0:      2114
  event-b:   738

  TOTAL: 47,364 ADC samples verified, zero errors.

Three full 3-sec events decode end-to-end across all three geo
channels.  The events where fewer samples decode (SP0/SS0/SV0/event-b)
are limited by walker robustness issues past the first few segments,
NOT by decoder correctness.

64 tests pass (up from 55).  Files: minimateplus/waveform_codec.py
(new 30 NN decode + corrected walker length), tests/test_waveform_codec.py
(new full-event regression tests), docs/* (updated status everywhere),
analysis/test_30nn_hybrid.py (new — the analysis script that confirmed
the format).
This commit is contained in:
Claude
2026-05-12 05:09:42 +00:00
committed by serversdown
parent d4cdce77fa
commit 2ff2762eec
5 changed files with 309 additions and 119 deletions
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tests/test_waveform_codec.py
+18 -11
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@@ -252,31 +252,38 @@ def test_decode_waveform_v2_returns_dict(event_name):
# for THIS segment's channel plus 2 continuation deltas (bytes [0:4]) for
# the PREVIOUS channel.
MULTICHANNEL_FIXTURES = [
# V70 (Mic-heavy, geos all near zero): perfect decode through first segment of each channel.
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.V70"), "Tran", 512),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.V70"), "Vert", 512),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.V70"), "Long", 512),
# JQ0 (Vert-heavy): first 512 samples per channel decode byte-exact.
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.JQ0"), "Tran", 512),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.JQ0"), "Vert", 258),
# SP0 (loud all): Long all 3 segments byte-exact (1536 samples).
# ALL geo channels fully decoded (3328 samples × 3 = 9984 per event), byte-exact:
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.V70"), "Tran", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.V70"), "Vert", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.V70"), "Long", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.JQ0"), "Tran", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.JQ0"), "Vert", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.JQ0"), "Long", 3328),
# SP0 (loud all-channels with 30 NN blocks): all decoded samples match truth.
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SP0"), "Tran", 2048),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SP0"), "Vert", 1538),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SP0"), "Long", 1536),
# SS0 / SV0 (loud-from-start): walker reaches a limited number of segments
# but every decoded sample matches truth.
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SS0"), "Tran", 734),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SS0"), "Vert", 512),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SS0"), "Long", 512),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SV0"), "Tran", 1024),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SV0"), "Vert", 578),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SV0"), "Long", 512),
# 5-8-26 quiet bundle: events without 30 NN blocks decode FULLY across all channels.
# event-a: 3328 samples × 3 channels = 9984 samples, all byte-exact.
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-a", "M529LKVQ.6S0"), "Tran", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-a", "M529LKVQ.6S0"), "Vert", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-a", "M529LKVQ.6S0"), "Long", 3328),
# event-c: 1280 samples × 3 channels
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-c", "M529LK44.AB0"), "Tran", 1280),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-c", "M529LK44.AB0"), "Vert", 1280),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-c", "M529LK44.AB0"), "Long", 1280),
# event-d: 1280 samples × 3 channels
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-d", "M529LK2V.470"), "Tran", 1280),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",