FA-50006 / PCM sample encoding / Open access

Pcm tdm active slots: active selection · case 01

Inactive physical slots are mistaken for dense PCM channels.

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

ROOT CAUSE

Inactive physical slots are mistaken for dense PCM channels.

VERIFIED REPAIR

Use the stated conversion contract at active selection.

Unsuccessful approach: Reversing selected channels changes the declared ascending-slot order.

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<<i)]
    out=[]
    for frame in frames:
        if len(frame)<slots:
            out.append(None)
            continue
        out.append(list(frame[:len(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 fixture	Actual	Expected	Outcome
oracle 1	`[[1, 3], [[10, 20], [1, 2]]]`	`[[1, 3], [[20, 40], [2, 4]]]`	Failed
oracle 2	`[[3], [None]]`	`[[3], [None]]`	Passed
oracle 3	`[[], [[]]]`	`[[], [[]]]`	Passed
oracle 4	`[[0, 1], []]`	`[[0, 1], []]`	Passed
oracle 5	`[[0, 3], [[1, 2]]]`	`[[0, 3], [[1, 4]]]`	Failed
oracle 6	`[[0], [[1]]]`	`[[0], [[1]]]`	Passed
oracle 7	`[[], [[]]]`	`[[], [[]]]`	Passed
variant packet 1	`[[1, 3], [[10, 20], [1, 2], [10, 20], [1, 2]]]`	`[[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]]`	Failed

SHA-256 / eb5c2772d42548310d249035d158443dfc404562ff08cd158aa0748f328bc7d7

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&(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 reversed(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 fixture	Actual	Expected	Outcome
oracle 1	`[[1, 3], [[40, 20], [4, 2]]]`	`[[1, 3], [[20, 40], [2, 4]]]`	Failed
oracle 2	`[[3], [None]]`	`[[3], [None]]`	Passed
oracle 3	`[[], [[]]]`	`[[], [[]]]`	Passed
oracle 4	`[[0, 1], []]`	`[[0, 1], []]`	Passed
oracle 5	`[[0, 3], [[4, 1]]]`	`[[0, 3], [[1, 4]]]`	Failed
oracle 6	`[[0], [[1]]]`	`[[0], [[1]]]`	Passed
oracle 7	`[[], [[]]]`	`[[], [[]]]`	Passed
variant packet 1	`[[1, 3], [[40, 20], [4, 2], [40, 20], [4, 2]]]`	`[[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]]`	Failed

SHA-256 / f5641dda6072d44dac7d0f1d7b53fff569109ccc9d5576b123b7f2e20f3816a9

3 / The verified repair

Exit 0

"""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<<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 fixture	Actual	Expected	Outcome
oracle 1	`[[1, 3], [[20, 40], [2, 4]]]`	`[[1, 3], [[20, 40], [2, 4]]]`	Passed
oracle 2	`[[3], [None]]`	`[[3], [None]]`	Passed
oracle 3	`[[], [[]]]`	`[[], [[]]]`	Passed
oracle 4	`[[0, 1], []]`	`[[0, 1], []]`	Passed
oracle 5	`[[0, 3], [[1, 4]]]`	`[[0, 3], [[1, 4]]]`	Passed
oracle 6	`[[0], [[1]]]`	`[[0], [[1]]]`	Passed
oracle 7	`[[], [[]]]`	`[[], [[]]]`	Passed
variant packet 1	`[[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]]`	`[[1, 3], [[20, 40], [2, 4], [20, 40], [2, 4]]]`	Passed

SHA-256 / f7693ccfc98bcfd5d45aa20328bb98c97199afaebe2b84622681230993d219e2

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 2026-09-29T14:45:05.132519+00:00.

Case digest / f869490782fa307e19ee83a8f48c9c0c3dc4675174a3009af0b0ec68bc2a7617