FA-49241 / PCM sample encoding / Open access
Pcm delta generation: predictor seed · case 01
Delta PCM starts from zero instead of transmitted predictor seed.
ROOT CAUSE
Delta PCM starts from zero instead of transmitted predictor seed.
VERIFIED REPAIR
Use the stated conversion contract at predictor seed.
Unsuccessful approach: Removing the seed sign breaks negative seeded blocks.
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=0
out=[]
for i,sample in enumerate(samples):
if i in reset_positions:
previous=initial
out.append(sample-previous)
previous=sample
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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| oracle 1 | [[12, -1, 3], 14] | [[2, -1, 3], 14] | Failed |
| oracle 2 | [[3, 4, 7, -4], 5] | [[1, 4, 7, -4], 5] | Failed |
| oracle 3 | [[], 0] | [[], -7] | Failed |
| oracle 4 | [[-3, -1], -4] | [[-1, -1], -4] | Failed |
| oracle 5 | [[0, -5], 0] | [[-5, -5], 0] | Failed |
| oracle 6 | [[1], 1] | [[1], 1] | Passed |
| oracle 7 | [[-3, -2, -1], 3] | [[-3, -2, -1], 3] | Passed |
| variant packet 1 | [[12, -1, 3, -2, -1, 3], 14] | [[2, -1, 3, -2, -1, 3], 14] | Failed |
SHA-256 / 8c60f3cce2cace64887c2848d5838d929bfade79fff606907c734c780bfbb5f6
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=abs(initial)
out=[]
for i,sample in enumerate(samples):
if i in reset_positions:
previous=initial
out.append(sample-previous)
previous=sample
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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| oracle 1 | [[2, -1, 3], 14] | [[2, -1, 3], 14] | Passed |
| oracle 2 | [[1, 4, 7, -4], 5] | [[1, 4, 7, -4], 5] | Passed |
| oracle 3 | [[], 7] | [[], -7] | Failed |
| oracle 4 | [[-5, -1], -4] | [[-1, -1], -4] | Failed |
| oracle 5 | [[-5, -5], 0] | [[-5, -5], 0] | Passed |
| oracle 6 | [[1], 1] | [[1], 1] | Passed |
| oracle 7 | [[-3, -2, -1], 3] | [[-3, -2, -1], 3] | Passed |
| variant packet 1 | [[2, -1, 3, -2, -1, 3], 14] | [[2, -1, 3, -2, -1, 3], 14] | Passed |
SHA-256 / aad55a5c30884f9bebd2590e0515cc086304af4ff748a2e3a9fc73e6bbb8c32a
3 / The verified repair
Exit 0"""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,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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| oracle 1 | [[2, -1, 3], 14] | [[2, -1, 3], 14] | Passed |
| oracle 2 | [[1, 4, 7, -4], 5] | [[1, 4, 7, -4], 5] | Passed |
| oracle 3 | [[], -7] | [[], -7] | Passed |
| oracle 4 | [[-1, -1], -4] | [[-1, -1], -4] | Passed |
| oracle 5 | [[-5, -5], 0] | [[-5, -5], 0] | Passed |
| oracle 6 | [[1], 1] | [[1], 1] | Passed |
| oracle 7 | [[-3, -2, -1], 3] | [[-3, -2, -1], 3] | Passed |
| variant packet 1 | [[2, -1, 3, -2, -1, 3], 14] | [[2, -1, 3, -2, -1, 3], 14] | Passed |
SHA-256 / 636466d6ee47e6fa42469739634988d453e56ae1440e52f5d832f00c21d4db79
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 2026-09-29T14:44:58.221638+00:00.
Case digest / 2131a401045dfcf3eaf09dd679b3b88cd5d5e5c40b306c8c84e967eb98c5e2c5