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FA-49256 / PCM sample encoding / Open access

Pcm delta generation: predictor feedback · case 01

Encoder feeds its residual back as next amplitude predictor.

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

ROOT CAUSE

Encoder feeds its residual back as next amplitude predictor.

THE FAILURE

Encoder feeds its residual back as next amplitude predictor.

Unsuccessful approach: Resetting predictor each sample destroys adjacent-sample differencing.

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-previous
    return [out,previous]
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, 9, 5], 5][[2, -1, 3], 14]Failed
oracle 2[[1, 6, 7, -2], -2][[1, 4, 7, -4], 5]Failed
oracle 3[[], -7][[], -7]Passed
oracle 4[[-1, -3], -3][[-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, 9, 5, 7, 4, 10], 10][[2, -1, 3, -2, -1, 3], 14]Failed

SHA-256 / 3ea318d7880767555de677fa300fd5e8a3afd1e3c0a549f7eb36851b5406bb20

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=initial
    return [out,previous]
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, 4], 10][[2, -1, 3], 14]Failed
oracle 2[[1, 5, 7, 3], 2][[1, 4, 7, -4], 5]Failed
oracle 3[[], -7][[], -7]Passed
oracle 4[[-1, -2], -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, 4, 2, 1, 4], 10][[2, -1, 3, -2, -1, 3], 14]Failed

SHA-256 / 25dbe4ee46a1f003293be1d4fa18517358ec873b4347647d0efaa81a0a6f3556

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

Case digest / 3e8e5412c7e63fb7c65a068674289e5499ec598f00e5691b1e503b29d9ae6d54