FA-49476 / PCM sample encoding / Open access
Riff pcm data spans: format order · case 01
PCM data is exposed before a format declaration is available.
ROOT CAUSE
PCM data is exposed before a format declaration is available.
VERIFIED REPAIR
Use the stated conversion contract at format order.
Unsuccessful approach: Inverting the gate rejects correctly ordered format/data files.
Case contract
Locate PCM spans in a bounded RIFF-like list of chunk descriptors with eight-byte headers and even-byte padding, requiring a preceding format chunk.
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(chunks, base):
cursor=base
spans=[]
format_seen=False
for tag,size in chunks:
data_start=cursor+8
if tag=='fmt ':
format_seen=True
if tag=='data':
spans.append([data_start,size])
cursor=data_start+size+(size&1)
return [spans,cursor]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([['fmt ', 16], ['data', 3], ['data', 2]], 12)), [[[44, 3], [56, 2]], 58])
check('oracle 2', solve(*([['JUNK', 3], ['fmt ', 16], ['data', 4]], 12)), [[[56, 4]], 60])
check('oracle 3', solve(*([['data', 4], ['fmt ', 16], ['data', 2]], 0)), [[[44, 2]], 46])
check('oracle 4', solve(*([], 12)), [[], 12])
check('oracle 5', solve(*([['fmt ', 18], ['LIST', 5], ['data', 0]], 12)), [[[60, 0]], 60])
check('oracle 6', solve(*([['fmt ', 16], ['data', 1], ['JUNK', 0], ['data', 1]], 0)), [[[32, 1], [50, 1]], 52])
check('oracle 7', solve(*([['JUNK', 0]], 0)), [[], 8])
if N == 1: check('variant packet 1', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2]], 104])
if N == 2: check('variant packet 2', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2]], 150])
if N == 3: check('variant packet 3', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2]], 196])
if N == 4: check('variant packet 4', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2], [228, 3], [240, 2]], 242])
if N == 5: check('variant packet 5', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2], [228, 3], [240, 2], [274, 3], [286, 2]], 288])
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 | [[[44, 3], [56, 2]], 58] | [[[44, 3], [56, 2]], 58] | Passed |
| oracle 2 | [[[56, 4]], 60] | [[[56, 4]], 60] | Passed |
| oracle 3 | [[[8, 4], [44, 2]], 46] | [[[44, 2]], 46] | Failed |
| oracle 4 | [[], 12] | [[], 12] | Passed |
| oracle 5 | [[[60, 0]], 60] | [[[60, 0]], 60] | Passed |
| oracle 6 | [[[32, 1], [50, 1]], 52] | [[[32, 1], [50, 1]], 52] | Passed |
| oracle 7 | [[], 8] | [[], 8] | Passed |
| variant packet 1 | [[[44, 3], [56, 2], [90, 3], [102, 2]], 104] | [[[44, 3], [56, 2], [90, 3], [102, 2]], 104] | Passed |
SHA-256 / 9e0b40c335b9288de6a9edd236105433c582aa3c94e7719be136a4e4a13bddd8
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(chunks, base):
cursor=base
spans=[]
format_seen=False
for tag,size in chunks:
data_start=cursor+8
if tag=='fmt ':
format_seen=True
if tag=='data' and not format_seen:
spans.append([data_start,size])
cursor=data_start+size+(size&1)
return [spans,cursor]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([['fmt ', 16], ['data', 3], ['data', 2]], 12)), [[[44, 3], [56, 2]], 58])
check('oracle 2', solve(*([['JUNK', 3], ['fmt ', 16], ['data', 4]], 12)), [[[56, 4]], 60])
check('oracle 3', solve(*([['data', 4], ['fmt ', 16], ['data', 2]], 0)), [[[44, 2]], 46])
check('oracle 4', solve(*([], 12)), [[], 12])
check('oracle 5', solve(*([['fmt ', 18], ['LIST', 5], ['data', 0]], 12)), [[[60, 0]], 60])
check('oracle 6', solve(*([['fmt ', 16], ['data', 1], ['JUNK', 0], ['data', 1]], 0)), [[[32, 1], [50, 1]], 52])
check('oracle 7', solve(*([['JUNK', 0]], 0)), [[], 8])
if N == 1: check('variant packet 1', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2]], 104])
if N == 2: check('variant packet 2', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2]], 150])
if N == 3: check('variant packet 3', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2]], 196])
if N == 4: check('variant packet 4', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2], [228, 3], [240, 2]], 242])
if N == 5: check('variant packet 5', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2], [228, 3], [240, 2], [274, 3], [286, 2]], 288])
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 | [[], 58] | [[[44, 3], [56, 2]], 58] | Failed |
| oracle 2 | [[], 60] | [[[56, 4]], 60] | Failed |
| oracle 3 | [[[8, 4]], 46] | [[[44, 2]], 46] | Failed |
| oracle 4 | [[], 12] | [[], 12] | Passed |
| oracle 5 | [[], 60] | [[[60, 0]], 60] | Failed |
| oracle 6 | [[], 52] | [[[32, 1], [50, 1]], 52] | Failed |
| oracle 7 | [[], 8] | [[], 8] | Passed |
| variant packet 1 | [[], 104] | [[[44, 3], [56, 2], [90, 3], [102, 2]], 104] | Failed |
SHA-256 / a577ee2fb6d42f284daa7d51348a964316b2f91c958fe6f31de760b827b6010f
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(chunks, base):
cursor=base
spans=[]
format_seen=False
for tag,size in chunks:
data_start=cursor+8
if tag=='fmt ':
format_seen=True
if tag=='data' and format_seen:
spans.append([data_start,size])
cursor=data_start+size+(size&1)
return [spans,cursor]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([['fmt ', 16], ['data', 3], ['data', 2]], 12)), [[[44, 3], [56, 2]], 58])
check('oracle 2', solve(*([['JUNK', 3], ['fmt ', 16], ['data', 4]], 12)), [[[56, 4]], 60])
check('oracle 3', solve(*([['data', 4], ['fmt ', 16], ['data', 2]], 0)), [[[44, 2]], 46])
check('oracle 4', solve(*([], 12)), [[], 12])
check('oracle 5', solve(*([['fmt ', 18], ['LIST', 5], ['data', 0]], 12)), [[[60, 0]], 60])
check('oracle 6', solve(*([['fmt ', 16], ['data', 1], ['JUNK', 0], ['data', 1]], 0)), [[[32, 1], [50, 1]], 52])
check('oracle 7', solve(*([['JUNK', 0]], 0)), [[], 8])
if N == 1: check('variant packet 1', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2]], 104])
if N == 2: check('variant packet 2', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2]], 150])
if N == 3: check('variant packet 3', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2]], 196])
if N == 4: check('variant packet 4', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2], [228, 3], [240, 2]], 242])
if N == 5: check('variant packet 5', solve(*[[['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2], ['fmt ', 16], ['data', 3], ['data', 2]], 12]), [[[44, 3], [56, 2], [90, 3], [102, 2], [136, 3], [148, 2], [182, 3], [194, 2], [228, 3], [240, 2], [274, 3], [286, 2]], 288])
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 | [[[44, 3], [56, 2]], 58] | [[[44, 3], [56, 2]], 58] | Passed |
| oracle 2 | [[[56, 4]], 60] | [[[56, 4]], 60] | Passed |
| oracle 3 | [[[44, 2]], 46] | [[[44, 2]], 46] | Passed |
| oracle 4 | [[], 12] | [[], 12] | Passed |
| oracle 5 | [[[60, 0]], 60] | [[[60, 0]], 60] | Passed |
| oracle 6 | [[[32, 1], [50, 1]], 52] | [[[32, 1], [50, 1]], 52] | Passed |
| oracle 7 | [[], 8] | [[], 8] | Passed |
| variant packet 1 | [[[44, 3], [56, 2], [90, 3], [102, 2]], 104] | [[[44, 3], [56, 2], [90, 3], [102, 2]], 104] | Passed |
SHA-256 / eac91c84b33f2cfd7b834d9fec20f96fd86f6e59e5dab3bec33ec23ae4c1b781
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 2026-09-29T14:45:00.327499+00:00.
Case digest / a9934c81b334b43e36650ba1d7deb4f84b92075fd0137fe1717cb5aceb46b4c9