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FA-49991 / PCM sample encoding / Open access

Pcm tdm active slots: slot mask order · case 01

Active TDM mask is interpreted with reversed slot numbering.

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

ROOT CAUSE

Active TDM mask is interpreted with reversed slot numbering.

THE FAILURE

Active TDM mask is interpreted with reversed slot numbering.

Unsuccessful approach: AND against slot index rather than its bit cannot select correct lanes.

Case contract

Stipulated TDM PCM extractor: active mask bits name ascending physical slots; ignore mask bits above slot count and reject incomplete physical frames.

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(frames, active_mask, slots):
    channels=[i for i in range(slots) if active_mask&(1<<(slots-1-i))]
    out=[]
    for frame in frames:
        if len(frame)<slots:
            out.append(None)
            continue
        out.append([frame[i] if i<len(frame) else None for i in channels])
    return [channels,out]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([[10, 20, 30, 40], [1, 2, 3, 4]], 10, 4)), [[1, 3], [[20, 40], [2, 4]]])
check('oracle 2', solve(*([[1, 2]], 8, 4)), [[3], [None]])
check('oracle 3', solve(*([[1, 2, 3]], 0, 3)), [[], [[]]])
check('oracle 4', solve(*([], 3, 4)), [[0, 1], []])
check('oracle 5', solve(*([[1, 2, 3, 4]], 9, 4)), [[0, 3], [[1, 4]]])
check('oracle 6', solve(*([[1, 2]], 1, 2)), [[0], [[1]]])
check('oracle 7', solve(*([[1, 2, 3, 4]], 16, 4)), [[], [[]]])
if N == 1: check('variant packet 1', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 2: check('variant packet 2', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 3: check('variant packet 3', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 4: check('variant packet 4', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 5: check('variant packet 5', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
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, 2], [[10, 30], [1, 3]]][[1, 3], [[20, 40], [2, 4]]]Failed
oracle 2[[0], [None]][[3], [None]]Failed
oracle 3[[], [[]]][[], [[]]]Passed
oracle 4[[2, 3], []][[0, 1], []]Failed
oracle 5[[0, 3], [[1, 4]]][[0, 3], [[1, 4]]]Passed
oracle 6[[1], [[2]]][[0], [[1]]]Failed
oracle 7[[], [[]]][[], [[]]]Passed
variant packet 1[[0, 2], [[10, 30], [1, 3], [10, 30], [1, 3]]][[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]]Failed

SHA-256 / d5e66d8e1aee64638c32f16e4d7cb05824608860417a8e5ff0d198afdd25ecc0

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(frames, active_mask, slots):
    channels=[i for i in range(slots) if active_mask&i]
    out=[]
    for frame in frames:
        if len(frame)<slots:
            out.append(None)
            continue
        out.append([frame[i] if i<len(frame) else None for i in channels])
    return [channels,out]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([[10, 20, 30, 40], [1, 2, 3, 4]], 10, 4)), [[1, 3], [[20, 40], [2, 4]]])
check('oracle 2', solve(*([[1, 2]], 8, 4)), [[3], [None]])
check('oracle 3', solve(*([[1, 2, 3]], 0, 3)), [[], [[]]])
check('oracle 4', solve(*([], 3, 4)), [[0, 1], []])
check('oracle 5', solve(*([[1, 2, 3, 4]], 9, 4)), [[0, 3], [[1, 4]]])
check('oracle 6', solve(*([[1, 2]], 1, 2)), [[0], [[1]]])
check('oracle 7', solve(*([[1, 2, 3, 4]], 16, 4)), [[], [[]]])
if N == 1: check('variant packet 1', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 2: check('variant packet 2', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 3: check('variant packet 3', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 4: check('variant packet 4', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
if N == 5: check('variant packet 5', solve(*[[[10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4], [10, 20, 30, 40], [1, 2, 3, 4]], 10, 4]), [[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4], [20, 40], [2, 4]]])
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[[2, 3], [[30, 40], [3, 4]]][[1, 3], [[20, 40], [2, 4]]]Failed
oracle 2[[], [None]][[3], [None]]Failed
oracle 3[[], [[]]][[], [[]]]Passed
oracle 4[[1, 2, 3], []][[0, 1], []]Failed
oracle 5[[1, 3], [[2, 4]]][[0, 3], [[1, 4]]]Failed
oracle 6[[1], [[2]]][[0], [[1]]]Failed
oracle 7[[], [[]]][[], [[]]]Passed
variant packet 1[[2, 3], [[30, 40], [3, 4], [30, 40], [3, 4]]][[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]]Failed

SHA-256 / 8c50367b4272edfeef47696af168a37b5180ad8204a5a841f8175956a7e357a3

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 2026-09-29T14:45:05.254644+00:00.

Case digest / 74031e4a4f1cd9548cbdfefdeca8c5c09b18914a87620fdd847e22733adbd2b9