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codec: crack wide-NN blocks (1X NN / 2X NN); loud events now fully decode

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When NN exceeds 0xFC, the codec extends to 12-bit NN by using the
low nibble of the TYPE byte as the high nibble of NN:

    1X NN  →  nibble-delta block, NN = (X << 8) | NN_byte
    2X NN  →  int8-delta block, same NN encoding

Walker and decode_waveform_v2 now handle both narrow (X=0) and wide
(X != 0) forms uniformly.

Discovered while investigating why SP0/SS0/SV0/event-b walkers stopped
mid-event.  SP0 segment 12 (V continuation, cycle 3) starts with
"11 90" — high nibble of byte 0 = 1 (= nibble-delta block type), low
nibble = 1 plus byte 1 = 0x90 → NN = 0x190 = 400 nibble deltas in
202 bytes.  Walker was rejecting "11" as a non-tag.

Sample count went from 47,364 to 72,972 verified byte-exact:

  event-a:  9984 (full)        was 9984 (full)
  event-b:  6912 (full)        was   738
  event-c:  3840 (full)        was 3840 (full)
  event-d:  3840 (full)        was 3840 (full)
  JQ0:      9984 (full)        was 9984 (full)
  V70:      9984 (full)        was 9984 (full)
  SP0:      9984 (full)        was 5122
  SS0:      9222 (-7 tail)     was 1758
  SV0:      9222 (-7 tail)     was 2114

7 of 9 fixtures now decode end-to-end across all 3 geo channels.
The 2 remaining (SS0, SV0) are missing only 1-7 tail samples per
channel — minor walker edge case at the very end.

74 tests pass (was 71).
This commit is contained in:
Claude
2026-05-16 03:29:13 +00:00
committed by serversdown
parent 85f4bcfe86
commit 0466bb4f44
4 changed files with 77 additions and 28 deletions
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tests/test_waveform_codec.py
+24 -15
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@@ -120,9 +120,10 @@ def test_walk_body_produces_blocks(event_name):
body = _bw_body(path)
blocks = walk_body(body)
assert len(blocks) > 0
# All blocks have one of the 5 known tag types.
# All blocks have one of the known tag families. ``1X NN`` / ``2X NN``
# with X in 0..F are valid (X > 0 means wide-NN encoding).
for b in blocks:
assert b.tag_hi in (0x10, 0x20, 0x00, 0x30, 0x40), (
assert (b.tag_hi & 0xF0) in (0x10, 0x20, 0x00, 0x30, 0x40), (
f"unknown tag {b.tag_hi:#04x} at offset {b.offset}"
)
@@ -254,25 +255,25 @@ 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 = [
# ALL geo channels fully decoded (3328 samples × 3 = 9984 per event), byte-exact:
# ALL geo channels fully decoded for every event in the bundle:
(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),
# SP0 (loud all-channels): NOW fully decodes after the wide-NN walker fix.
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SP0"), "Tran", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SP0"), "Vert", 3328),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SP0"), "Long", 3328),
# SS0 / SV0 (loud-from-start): walker now reaches 3072–3078 samples per
# channel (out of 3079 total). A few tail samples still missing.
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SS0"), "Tran", 3078),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SS0"), "Vert", 3072),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SS0"), "Long", 3072),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SV0"), "Tran", 3078),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SV0"), "Vert", 3072),
(os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SV0"), "Long", 3072),
# 5-8-26 quiet bundle: events without 30 NN blocks decode FULLY across all channels.
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-a", "M529LKVQ.6S0"), "Tran", 3328),
@@ -292,6 +293,14 @@ MULTICHANNEL_FIXTURES = [
"event-d", "M529LK2V.470"), "Vert", 1280),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-d", "M529LK2V.470"), "Long", 1280),
# event-b: 2304 samples × 3 — now fully decodes (was the historical
# walker-stop case; fixed by wide-NN tag support).
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-b", "M529LK5Q.RG0"), "Tran", 2304),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-b", "M529LK5Q.RG0"), "Vert", 2304),
(os.path.join(os.path.dirname(__file__), "fixtures", "decode-re-5-8-26",
"event-b", "M529LK5Q.RG0"), "Long", 2304),
]