FA-50246 / PCM sample encoding / Open access

Pcm biphase mark generation: payload transition · case 01

Payload transition convention is inverted.

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

ROOT CAUSE

Payload transition convention is inverted.

VERIFIED REPAIR

Use the stated conversion contract at payload transition.

Unsuccessful approach: Deriving the second half from prior cell level creates the wrong midcell state.

Case contract

Encode PCM transport payload bits as stipulated biphase-mark half-cells with mandatory boundary transitions and explicit initial/final physical levels.

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(bits, initial):
    previous=initial
    cells=[]
    for bit in bits:
        first=1-previous
        second=first if bit else 1-first
        cells.append([first,second])
        previous=second
    return [cells,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([0, 1, 0, 1], 0)), [[[1, 1], [0, 1], [0, 0], [1, 0]], 0])
check('oracle 2', solve(*([1, 1, 1], 1)), [[[0, 1], [0, 1], [0, 1]], 1])
check('oracle 3', solve(*([0, 0], 0)), [[[1, 1], [0, 0]], 0])
check('oracle 4', solve(*([], 1)), [[], 1])
check('oracle 5', solve(*([1], 0)), [[[1, 0]], 0])
check('oracle 6', solve(*([0, 1, 1, 0], 1)), [[[0, 0], [1, 0], [1, 0], [1, 1]], 1])
check('oracle 7', solve(*([0], 1)), [[[0, 0]], 0])
if N == 1: check('variant packet 1', solve(*[[0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 2: check('variant packet 2', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 3: check('variant packet 3', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 4: check('variant packet 4', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 5: check('variant packet 5', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 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 fixture	Actual	Expected	Outcome
oracle 1	`[[[1, 0], [1, 1], [0, 1], [0, 0]], 0]`	`[[[1, 1], [0, 1], [0, 0], [1, 0]], 0]`	Failed
oracle 2	`[[[0, 0], [1, 1], [0, 0]], 0]`	`[[[0, 1], [0, 1], [0, 1]], 1]`	Failed
oracle 3	`[[[1, 0], [1, 0]], 0]`	`[[[1, 1], [0, 0]], 0]`	Failed
oracle 4	`[[], 1]`	`[[], 1]`	Passed
oracle 5	`[[[1, 1]], 1]`	`[[[1, 0]], 0]`	Failed
oracle 6	`[[[0, 1], [0, 0], [1, 1], [0, 1]], 1]`	`[[[0, 0], [1, 0], [1, 0], [1, 1]], 1]`	Failed
oracle 7	`[[[0, 1]], 1]`	`[[[0, 0]], 0]`	Failed
variant packet 1	`[[[1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0]], 0]`	`[[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0]`	Failed

SHA-256 / 7636fd941ad3981e495394faec604c93a006be77f6bb6224ccd1b26539d53247

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(bits, initial):
    previous=initial
    cells=[]
    for bit in bits:
        first=1-previous
        second=1-previous if bit else previous
        cells.append([first,second])
        previous=second
    return [cells,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([0, 1, 0, 1], 0)), [[[1, 1], [0, 1], [0, 0], [1, 0]], 0])
check('oracle 2', solve(*([1, 1, 1], 1)), [[[0, 1], [0, 1], [0, 1]], 1])
check('oracle 3', solve(*([0, 0], 0)), [[[1, 1], [0, 0]], 0])
check('oracle 4', solve(*([], 1)), [[], 1])
check('oracle 5', solve(*([1], 0)), [[[1, 0]], 0])
check('oracle 6', solve(*([0, 1, 1, 0], 1)), [[[0, 0], [1, 0], [1, 0], [1, 1]], 1])
check('oracle 7', solve(*([0], 1)), [[[0, 0]], 0])
if N == 1: check('variant packet 1', solve(*[[0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 2: check('variant packet 2', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 3: check('variant packet 3', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 4: check('variant packet 4', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 5: check('variant packet 5', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 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 fixture	Actual	Expected	Outcome
oracle 1	`[[[1, 0], [1, 1], [0, 1], [0, 0]], 0]`	`[[[1, 1], [0, 1], [0, 0], [1, 0]], 0]`	Failed
oracle 2	`[[[0, 0], [1, 1], [0, 0]], 0]`	`[[[0, 1], [0, 1], [0, 1]], 1]`	Failed
oracle 3	`[[[1, 0], [1, 0]], 0]`	`[[[1, 1], [0, 0]], 0]`	Failed
oracle 4	`[[], 1]`	`[[], 1]`	Passed
oracle 5	`[[[1, 1]], 1]`	`[[[1, 0]], 0]`	Failed
oracle 6	`[[[0, 1], [0, 0], [1, 1], [0, 1]], 1]`	`[[[0, 0], [1, 0], [1, 0], [1, 1]], 1]`	Failed
oracle 7	`[[[0, 1]], 1]`	`[[[0, 0]], 0]`	Failed
variant packet 1	`[[[1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0]], 0]`	`[[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0]`	Failed

SHA-256 / fcde0a964d71f751ab5d81e971196f28f5557115ec36529784f2f3cb57778ea4

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(bits, initial):
    previous=initial
    cells=[]
    for bit in bits:
        first=1-previous
        second=1-first if bit else first
        cells.append([first,second])
        previous=second
    return [cells,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([0, 1, 0, 1], 0)), [[[1, 1], [0, 1], [0, 0], [1, 0]], 0])
check('oracle 2', solve(*([1, 1, 1], 1)), [[[0, 1], [0, 1], [0, 1]], 1])
check('oracle 3', solve(*([0, 0], 0)), [[[1, 1], [0, 0]], 0])
check('oracle 4', solve(*([], 1)), [[], 1])
check('oracle 5', solve(*([1], 0)), [[[1, 0]], 0])
check('oracle 6', solve(*([0, 1, 1, 0], 1)), [[[0, 0], [1, 0], [1, 0], [1, 1]], 1])
check('oracle 7', solve(*([0], 1)), [[[0, 0]], 0])
if N == 1: check('variant packet 1', solve(*[[0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 2: check('variant packet 2', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 3: check('variant packet 3', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 4: check('variant packet 4', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0])
if N == 5: check('variant packet 5', solve(*[[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], 0]), [[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 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 fixture	Actual	Expected	Outcome
oracle 1	`[[[1, 1], [0, 1], [0, 0], [1, 0]], 0]`	`[[[1, 1], [0, 1], [0, 0], [1, 0]], 0]`	Passed
oracle 2	`[[[0, 1], [0, 1], [0, 1]], 1]`	`[[[0, 1], [0, 1], [0, 1]], 1]`	Passed
oracle 3	`[[[1, 1], [0, 0]], 0]`	`[[[1, 1], [0, 0]], 0]`	Passed
oracle 4	`[[], 1]`	`[[], 1]`	Passed
oracle 5	`[[[1, 0]], 0]`	`[[[1, 0]], 0]`	Passed
oracle 6	`[[[0, 0], [1, 0], [1, 0], [1, 1]], 1]`	`[[[0, 0], [1, 0], [1, 0], [1, 1]], 1]`	Passed
oracle 7	`[[[0, 0]], 0]`	`[[[0, 0]], 0]`	Passed
variant packet 1	`[[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0]`	`[[[1, 1], [0, 1], [0, 0], [1, 0], [1, 1], [0, 1], [0, 0], [1, 0]], 0]`	Passed

SHA-256 / 1a49c145d9f1652cf046d3c399ce911012cbf61b4536ba7c02be230603dd8d21

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 2026-09-29T14:45:07.328863+00:00.

Case digest / 18be996907d5495a58ebf3e6c889954bb42ff9318430f287fe63b4190f2f8384