FAILURE MAP
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FA-50081 / PCM sample encoding / Open access

Pcm sample validity sideband: validity index · case 01

All PCM samples use the first validity flag.

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

ROOT CAUSE

All PCM samples use the first validity flag.

THE FAILURE

All PCM samples use the first validity flag.

Unsuccessful approach: Reversing the flag array mismatches metadata and amplitudes.

Case contract

Decode PCM with a parallel validity vector, missing flags invalid, holding the most recent valid sample for invalid positions while retaining explicit validity metadata.

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(samples, validity, conceal):
    out=[]
    previous=conceal
    for index,sample in enumerate(samples):
        valid=validity[0] if index<len(validity) else False
        if valid:
            previous=sample
        out.append([sample if valid else previous,bool(valid)])
    return [out,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([1, 9, 3, 8], [True, False, True, False], 0)), [[[1, True], [1, False], [3, True], [3, False]], 3])
check('oracle 2', solve(*([9, 2], [False, True], 7)), [[[7, False], [2, True]], 2])
check('oracle 3', solve(*([1, 2, 3], [True], 0)), [[[1, True], [1, False], [1, False]], 1])
check('oracle 4', solve(*([], [], 4)), [[], 4])
check('oracle 5', solve(*([4, 5], [False, False], -1)), [[[-1, False], [-1, False]], -1])
check('oracle 6', solve(*([1, 2, 3], [False, True, False], 5)), [[[5, False], [2, True], [2, False]], 2])
check('oracle 7', solve(*([0], [True], 8)), [[[0, True]], 0])
if N == 1: check('variant packet 1', solve(*[[1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 2: check('variant packet 2', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 3: check('variant packet 3', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 4: check('variant packet 4', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 5: check('variant packet 5', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
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[[[1, True], [9, True], [3, True], [8, True]], 8][[[1, True], [1, False], [3, True], [3, False]], 3]Failed
oracle 2[[[7, False], [7, False]], 7][[[7, False], [2, True]], 2]Failed
oracle 3[[[1, True], [1, False], [1, False]], 1][[[1, True], [1, False], [1, False]], 1]Passed
oracle 4[[], 4][[], 4]Passed
oracle 5[[[-1, False], [-1, False]], -1][[[-1, False], [-1, False]], -1]Passed
oracle 6[[[5, False], [5, False], [5, False]], 5][[[5, False], [2, True], [2, False]], 2]Failed
oracle 7[[[0, True]], 0][[[0, True]], 0]Passed
variant packet 1[[[1, True], [9, True], [3, True], [8, True], [8, False], [8, False], [8, False], [8, False]], 8][[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3]Failed

SHA-256 / 244bbf3ad00d00ac8a0a61af95bd7bdabbaadd65c027b54692fea595dc4cdf39

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(samples, validity, conceal):
    out=[]
    previous=conceal
    for index,sample in enumerate(samples):
        valid=validity[-1-index] if index<len(validity) else False
        if valid:
            previous=sample
        out.append([sample if valid else previous,bool(valid)])
    return [out,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([1, 9, 3, 8], [True, False, True, False], 0)), [[[1, True], [1, False], [3, True], [3, False]], 3])
check('oracle 2', solve(*([9, 2], [False, True], 7)), [[[7, False], [2, True]], 2])
check('oracle 3', solve(*([1, 2, 3], [True], 0)), [[[1, True], [1, False], [1, False]], 1])
check('oracle 4', solve(*([], [], 4)), [[], 4])
check('oracle 5', solve(*([4, 5], [False, False], -1)), [[[-1, False], [-1, False]], -1])
check('oracle 6', solve(*([1, 2, 3], [False, True, False], 5)), [[[5, False], [2, True], [2, False]], 2])
check('oracle 7', solve(*([0], [True], 8)), [[[0, True]], 0])
if N == 1: check('variant packet 1', solve(*[[1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 2: check('variant packet 2', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 3: check('variant packet 3', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 4: check('variant packet 4', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 5: check('variant packet 5', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
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, False], [9, True], [9, False], [8, True]], 8][[[1, True], [1, False], [3, True], [3, False]], 3]Failed
oracle 2[[[9, True], [9, False]], 9][[[7, False], [2, True]], 2]Failed
oracle 3[[[1, True], [1, False], [1, False]], 1][[[1, True], [1, False], [1, False]], 1]Passed
oracle 4[[], 4][[], 4]Passed
oracle 5[[[-1, False], [-1, False]], -1][[[-1, False], [-1, False]], -1]Passed
oracle 6[[[5, False], [2, True], [2, False]], 2][[[5, False], [2, True], [2, False]], 2]Passed
oracle 7[[[0, True]], 0][[[0, True]], 0]Passed
variant packet 1[[[0, False], [9, True], [9, False], [8, True], [8, False], [8, False], [8, False], [8, False]], 8][[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3]Failed

SHA-256 / cfa0f16b388a5c615fb11544cf55f1051bf1ca9f97bf5a0755e9f7861bf3592c

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 2026-09-29T14:45:05.919362+00:00.

Case digest / c09109fee91b78266840c03f3022bdf2f6046b5c8469c1e206987eda89293d9d