FAILURE MAP
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FA-50231 / PCM sample encoding / Open access

Pcm biphase mark payload: validity output · case 01

PCM payload value is confused with line-code validity.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

PCM payload value is confused with line-code validity.

THE FAILURE

PCM payload value is confused with line-code validity.

Unsuccessful approach: Forcing every cell valid hides missing mandatory boundary transitions.

Case contract

Decode stipulated biphase-mark PCM transport cells: every cell must transition at its start, midcell transition is one, and final physical level carries across packets.

Why this case matters

Offline PCM interchange uses these exact bounded packet and sample representation decisions.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(cells, initial):
    previous=initial
    bits=[]
    valid=[]
    for first,second in cells:
        boundary=first!=previous
        bit=int(first!=second)
        bits.append(bit)
        valid.append(bool(bit))
        previous=second
    return [bits,valid,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([[1, 1], [0, 1], [0, 0]], 0)), [[0, 1, 0], [True, True, True], 0])
check('oracle 2', solve(*([[0, 1], [1, 0]], 1)), [[1, 1], [True, False], 0])
check('oracle 3', solve(*([[0, 0], [1, 1]], 0)), [[0, 0], [False, True], 1])
check('oracle 4', solve(*([], 1)), [[], [], 1])
check('oracle 5', solve(*([[1, 0], [1, 0]], 0)), [[1, 1], [True, True], 0])
check('oracle 6', solve(*([[1, 1]], 1)), [[0], [False], 1])
check('oracle 7', solve(*([[0, 0], [0, 1], [1, 1]], 1)), [[0, 1, 0], [True, False, False], 1])
if N == 1: check('variant packet 1', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0], [True, True, True, True, True, True], 0])
if N == 2: check('variant packet 2', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True], 0])
if N == 3: check('variant packet 3', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True, True, True, True], 0])
if N == 4: check('variant packet 4', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True, True, True, True, True, True, True], 0])
if N == 5: check('variant packet 5', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True, True, True, True, True, True, True, True, True, True], 0])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
oracle 1[[0, 1, 0], [False, True, False], 0][[0, 1, 0], [True, True, True], 0]Failed
oracle 2[[1, 1], [True, True], 0][[1, 1], [True, False], 0]Failed
oracle 3[[0, 0], [False, False], 1][[0, 0], [False, True], 1]Failed
oracle 4[[], [], 1][[], [], 1]Passed
oracle 5[[1, 1], [True, True], 0][[1, 1], [True, True], 0]Passed
oracle 6[[0], [False], 1][[0], [False], 1]Passed
oracle 7[[0, 1, 0], [False, True, False], 1][[0, 1, 0], [True, False, False], 1]Failed
variant packet 1[[0, 1, 0, 0, 1, 0], [False, True, False, False, True, False], 0][[0, 1, 0, 0, 1, 0], [True, True, True, True, True, True], 0]Failed

SHA-256 / 3cc931378ab4f5124d6cf26b0605ac2161b113fad590e80c40aa0b096b195fc9

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(cells, initial):
    previous=initial
    bits=[]
    valid=[]
    for first,second in cells:
        boundary=first!=previous
        bit=int(first!=second)
        bits.append(bit)
        valid.append(True)
        previous=second
    return [bits,valid,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([[1, 1], [0, 1], [0, 0]], 0)), [[0, 1, 0], [True, True, True], 0])
check('oracle 2', solve(*([[0, 1], [1, 0]], 1)), [[1, 1], [True, False], 0])
check('oracle 3', solve(*([[0, 0], [1, 1]], 0)), [[0, 0], [False, True], 1])
check('oracle 4', solve(*([], 1)), [[], [], 1])
check('oracle 5', solve(*([[1, 0], [1, 0]], 0)), [[1, 1], [True, True], 0])
check('oracle 6', solve(*([[1, 1]], 1)), [[0], [False], 1])
check('oracle 7', solve(*([[0, 0], [0, 1], [1, 1]], 1)), [[0, 1, 0], [True, False, False], 1])
if N == 1: check('variant packet 1', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0], [True, True, True, True, True, True], 0])
if N == 2: check('variant packet 2', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True], 0])
if N == 3: check('variant packet 3', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True, True, True, True], 0])
if N == 4: check('variant packet 4', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True, True, True, True, True, True, True], 0])
if N == 5: check('variant packet 5', solve(*[[[1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0], [1, 1], [0, 1], [0, 0]], 0]), [[0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0], [True, True, True, True, True, True, True, True, True, True, True, True, True, True, True, True, True, True], 0])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
oracle 1[[0, 1, 0], [True, True, True], 0][[0, 1, 0], [True, True, True], 0]Passed
oracle 2[[1, 1], [True, True], 0][[1, 1], [True, False], 0]Failed
oracle 3[[0, 0], [True, True], 1][[0, 0], [False, True], 1]Failed
oracle 4[[], [], 1][[], [], 1]Passed
oracle 5[[1, 1], [True, True], 0][[1, 1], [True, True], 0]Passed
oracle 6[[0], [True], 1][[0], [False], 1]Failed
oracle 7[[0, 1, 0], [True, True, True], 1][[0, 1, 0], [True, False, False], 1]Failed
variant packet 1[[0, 1, 0, 0, 1, 0], [True, True, True, True, True, True], 0][[0, 1, 0, 0, 1, 0], [True, True, True, True, True, True], 0]Passed

SHA-256 / a2715ef52ee43724e5fc9be8c419ad1f994e1886525383c67d94fba625f68406

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

Stipulated finite model; no claim of hardware timing or full file-format conformance. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:45:07.297596+00:00.

Case digest / 411bf9d7c0f195dea45a7e48a799e05efffbc2490d33d2d8ec88b67a0d7f971d