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FA-49236 / PCM sample encoding / Open access

Pcm delta reconstruction: returned seed · case 01

Cross-packet continuation returns the old seed.

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

ROOT CAUSE

Cross-packet continuation returns the old seed.

THE FAILURE

Cross-packet continuation returns the old seed.

Unsuccessful approach: Resetting continuation to zero introduces a DC discontinuity.

Case contract

Reconstruct bounded delta-coded PCM from a seed and explicit sample-index resets before residual application, returning the continuation predictor.

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(deltas, initial, reset_positions):
    previous=initial
    out=[]
    for i,delta in enumerate(deltas):
        if i in reset_positions:
            previous=initial
        previous+=delta
        out.append(previous)
    return [out,initial]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([2, -1, 3], 10, [])), [[12, 11, 14], 14])
check('oracle 2', solve(*([1, 2, 3, 4], 5, [2])), [[6, 8, 8, 12], 12])
check('oracle 3', solve(*([], 7, [])), [[], 7])
check('oracle 4', solve(*([0, 0], -3, [0])), [[-3, -3], -3])
check('oracle 5', solve(*([-2, 4, -1], 0, [1])), [[-2, 4, 3], 3])
check('oracle 6', solve(*([3], 2, [])), [[5], 5])
check('oracle 7', solve(*([1, 1, 1], 1, [0, 1, 2])), [[2, 2, 2], 2])
if N == 1: check('variant packet 1', solve(*[[2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18], 18])
if N == 2: check('variant packet 2', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22], 22])
if N == 3: check('variant packet 3', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22, 24, 23, 26], 26])
if N == 4: check('variant packet 4', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22, 24, 23, 26, 28, 27, 30], 30])
if N == 5: check('variant packet 5', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22, 24, 23, 26, 28, 27, 30, 32, 31, 34], 34])
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[[12, 11, 14], 10][[12, 11, 14], 14]Failed
oracle 2[[6, 8, 8, 12], 5][[6, 8, 8, 12], 12]Failed
oracle 3[[], 7][[], 7]Passed
oracle 4[[-3, -3], -3][[-3, -3], -3]Passed
oracle 5[[-2, 4, 3], 0][[-2, 4, 3], 3]Failed
oracle 6[[5], 2][[5], 5]Failed
oracle 7[[2, 2, 2], 1][[2, 2, 2], 2]Failed
variant packet 1[[12, 11, 14, 16, 15, 18], 10][[12, 11, 14, 16, 15, 18], 18]Failed

SHA-256 / 1d2342ebb71bbd27e6ad2ed45292e181961ee89dae79d4aeb986935e1a29b6b4

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(deltas, initial, reset_positions):
    previous=initial
    out=[]
    for i,delta in enumerate(deltas):
        if i in reset_positions:
            previous=initial
        previous+=delta
        out.append(previous)
    return [out,0]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([2, -1, 3], 10, [])), [[12, 11, 14], 14])
check('oracle 2', solve(*([1, 2, 3, 4], 5, [2])), [[6, 8, 8, 12], 12])
check('oracle 3', solve(*([], 7, [])), [[], 7])
check('oracle 4', solve(*([0, 0], -3, [0])), [[-3, -3], -3])
check('oracle 5', solve(*([-2, 4, -1], 0, [1])), [[-2, 4, 3], 3])
check('oracle 6', solve(*([3], 2, [])), [[5], 5])
check('oracle 7', solve(*([1, 1, 1], 1, [0, 1, 2])), [[2, 2, 2], 2])
if N == 1: check('variant packet 1', solve(*[[2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18], 18])
if N == 2: check('variant packet 2', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22], 22])
if N == 3: check('variant packet 3', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22, 24, 23, 26], 26])
if N == 4: check('variant packet 4', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22, 24, 23, 26, 28, 27, 30], 30])
if N == 5: check('variant packet 5', solve(*[[2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3, 2, -1, 3], 10, []]), [[12, 11, 14, 16, 15, 18, 20, 19, 22, 24, 23, 26, 28, 27, 30, 32, 31, 34], 34])
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[[12, 11, 14], 0][[12, 11, 14], 14]Failed
oracle 2[[6, 8, 8, 12], 0][[6, 8, 8, 12], 12]Failed
oracle 3[[], 0][[], 7]Failed
oracle 4[[-3, -3], 0][[-3, -3], -3]Failed
oracle 5[[-2, 4, 3], 0][[-2, 4, 3], 3]Failed
oracle 6[[5], 0][[5], 5]Failed
oracle 7[[2, 2, 2], 0][[2, 2, 2], 2]Failed
variant packet 1[[12, 11, 14, 16, 15, 18], 0][[12, 11, 14, 16, 15, 18], 18]Failed

SHA-256 / c66b37b8da6da2d82c8b4323f4ffd320c27fba5f3dbecdae30d2df99eea3f3d6

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.

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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 2026-09-29T14:44:58.040035+00:00.

Case digest / 49e755d9a1787b881137c47982da10d5274c8ec4d00c8cc6a2f7ad2a6b3cad1d