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FA-49261 / PCM sample encoding / Open access

Pcm delta generation: continuation level · case 01

Encoder returns seed rather than final amplitude for continuation.

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

ROOT CAUSE

Encoder returns seed rather than final amplitude for continuation.

THE FAILURE

Encoder returns seed rather than final amplitude for continuation.

Unsuccessful approach: Returning final residual seeds the next packet with a difference instead of a level.

Case contract

Generate signed PCM residuals relative to the previous amplitude; reset at explicit sample positions and return the final amplitude continuation seed.

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, initial, reset_positions):
    previous=initial
    out=[]
    for i,sample in enumerate(samples):
        if i in reset_positions:
            previous=initial
        out.append(sample-previous)
        previous=sample
    return [out,initial]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([12, 11, 14], 10, [])), [[2, -1, 3], 14])
check('oracle 2', solve(*([3, 7, 9, 5], 2, [2])), [[1, 4, 7, -4], 5])
check('oracle 3', solve(*([], -7, [])), [[], -7])
check('oracle 4', solve(*([-3, -4], -2, [])), [[-1, -1], -4])
check('oracle 5', solve(*([0, 0], 5, [1])), [[-5, -5], 0])
check('oracle 6', solve(*([1], 0, [])), [[1], 1])
check('oracle 7', solve(*([1, 2, 3], 4, [0, 1, 2])), [[-3, -2, -1], 3])
if N == 1: check('variant packet 1', solve(*[[12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3], 14])
if N == 2: check('variant packet 2', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
if N == 3: check('variant packet 3', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
if N == 4: check('variant packet 4', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
if N == 5: check('variant packet 5', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
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, -1, 3], 10][[2, -1, 3], 14]Failed
oracle 2[[1, 4, 7, -4], 2][[1, 4, 7, -4], 5]Failed
oracle 3[[], -7][[], -7]Passed
oracle 4[[-1, -1], -2][[-1, -1], -4]Failed
oracle 5[[-5, -5], 5][[-5, -5], 0]Failed
oracle 6[[1], 0][[1], 1]Failed
oracle 7[[-3, -2, -1], 4][[-3, -2, -1], 3]Failed
variant packet 1[[2, -1, 3, -2, -1, 3], 10][[2, -1, 3, -2, -1, 3], 14]Failed

SHA-256 / 2e79f070e2ecbd8ebd2746fbf82cffb4145c7a51ea4d432fb4158224da60a2de

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(samples, initial, reset_positions):
    previous=initial
    out=[]
    for i,sample in enumerate(samples):
        if i in reset_positions:
            previous=initial
        out.append(sample-previous)
        previous=sample
    return [out,out[-1] if out else initial]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([12, 11, 14], 10, [])), [[2, -1, 3], 14])
check('oracle 2', solve(*([3, 7, 9, 5], 2, [2])), [[1, 4, 7, -4], 5])
check('oracle 3', solve(*([], -7, [])), [[], -7])
check('oracle 4', solve(*([-3, -4], -2, [])), [[-1, -1], -4])
check('oracle 5', solve(*([0, 0], 5, [1])), [[-5, -5], 0])
check('oracle 6', solve(*([1], 0, [])), [[1], 1])
check('oracle 7', solve(*([1, 2, 3], 4, [0, 1, 2])), [[-3, -2, -1], 3])
if N == 1: check('variant packet 1', solve(*[[12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3], 14])
if N == 2: check('variant packet 2', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
if N == 3: check('variant packet 3', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
if N == 4: check('variant packet 4', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
if N == 5: check('variant packet 5', solve(*[[12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14, 12, 11, 14], 10, []]), [[2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3, -2, -1, 3], 14])
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, -1, 3], 3][[2, -1, 3], 14]Failed
oracle 2[[1, 4, 7, -4], -4][[1, 4, 7, -4], 5]Failed
oracle 3[[], -7][[], -7]Passed
oracle 4[[-1, -1], -1][[-1, -1], -4]Failed
oracle 5[[-5, -5], -5][[-5, -5], 0]Failed
oracle 6[[1], 1][[1], 1]Passed
oracle 7[[-3, -2, -1], -1][[-3, -2, -1], 3]Failed
variant packet 1[[2, -1, 3, -2, -1, 3], 3][[2, -1, 3, -2, -1, 3], 14]Failed

SHA-256 / 8a104c6e0f0d287ce2950dd9053ffeb9d0a465140ff0f2e7b9ee92a24907085e

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 2026-09-29T14:44:58.354946+00:00.

Case digest / f5ac6ca72c1f77c602be7c9006497e6eb5ee354ce9bebf20b09cd6b7dfa12d9e