FA-48886 / PCM sample encoding / Open access

Subbyte code reader: reported consumption · case 01

Cursor excludes consumed sync prefix.

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

ROOT CAUSE

Cursor excludes consumed sync prefix.

THE FAILURE

Cursor excludes consumed sync prefix.

Unsuccessful approach: Reporting the whole packet as consumed loses a following unconsumed field.

Case contract

Read up to declared unsigned packed fields after a bit prefix; incomplete fields are ignored, and report cursor in bits from packet start.

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(octets, width, count, prefix_bits):
    bits = [(byte >> (7-j)) & 1 for byte in octets for j in range(8)]
    bits = bits[prefix_bits:]
    available = len(bits)//width
    count = min(count,available)
    values=[]
    for i in range(count):
        values.append(sum(bits[i*width+j] << (width-1-j) for j in range(width)))
    consumed = count*width
    return [values,consumed]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([179, 144], 3, 3, 2)), [[6, 3, 4], 11])
check('oracle 2', solve(*([255], 2, 2, 0)), [[3, 3], 4])
check('oracle 3', solve(*([0], 1, 8, 0)), [[0, 0, 0, 0, 0, 0, 0, 0], 8])
check('oracle 4', solve(*([], 3, 0, 0)), [[], 0])
check('oracle 5', solve(*([160], 3, 1, 1)), [[2], 4])
check('oracle 6', solve(*([18, 52], 4, 2, 4)), [[2, 3], 12])
check('oracle 7', solve(*([255], 3, 5, 1)), [[7, 7], 7])
if N == 1: check('variant packet 1', solve(*[[179, 144, 179, 144], 3, 6, 2]), [[6, 3, 4, 4, 1, 3], 20])
if N == 2: check('variant packet 2', solve(*[[179, 144, 179, 144, 179, 144], 3, 9, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2], 29])
if N == 3: check('variant packet 3', solve(*[[179, 144, 179, 144, 179, 144, 179, 144], 3, 12, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2, 0, 5, 4], 38])
if N == 4: check('variant packet 4', solve(*[[179, 144, 179, 144, 179, 144, 179, 144, 179, 144], 3, 15, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2, 0, 5, 4, 7, 1, 0], 47])
if N == 5: check('variant packet 5', solve(*[[179, 144, 179, 144, 179, 144, 179, 144, 179, 144, 179, 144], 3, 18, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2, 0, 5, 4, 7, 1, 0, 2, 6, 3], 56])
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	`[[6, 3, 4], 9]`	`[[6, 3, 4], 11]`	Failed
oracle 2	`[[3, 3], 4]`	`[[3, 3], 4]`	Passed
oracle 3	`[[0, 0, 0, 0, 0, 0, 0, 0], 8]`	`[[0, 0, 0, 0, 0, 0, 0, 0], 8]`	Passed
oracle 4	`[[], 0]`	`[[], 0]`	Passed
oracle 5	`[[2], 3]`	`[[2], 4]`	Failed
oracle 6	`[[2, 3], 8]`	`[[2, 3], 12]`	Failed
oracle 7	`[[7, 7], 6]`	`[[7, 7], 7]`	Failed
variant packet 1	`[[6, 3, 4, 4, 1, 3], 18]`	`[[6, 3, 4, 4, 1, 3], 20]`	Failed

SHA-256 / 2f53416f7590e73a50b8345c3b158d03f3acf0a08b339ed5317189e251ad2c41

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(octets, width, count, prefix_bits):
    bits = [(byte >> (7-j)) & 1 for byte in octets for j in range(8)]
    bits = bits[prefix_bits:]
    available = len(bits)//width
    count = min(count,available)
    values=[]
    for i in range(count):
        values.append(sum(bits[i*width+j] << (width-1-j) for j in range(width)))
    consumed = prefix_bits+len(octets)*8
    return [values,consumed]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([179, 144], 3, 3, 2)), [[6, 3, 4], 11])
check('oracle 2', solve(*([255], 2, 2, 0)), [[3, 3], 4])
check('oracle 3', solve(*([0], 1, 8, 0)), [[0, 0, 0, 0, 0, 0, 0, 0], 8])
check('oracle 4', solve(*([], 3, 0, 0)), [[], 0])
check('oracle 5', solve(*([160], 3, 1, 1)), [[2], 4])
check('oracle 6', solve(*([18, 52], 4, 2, 4)), [[2, 3], 12])
check('oracle 7', solve(*([255], 3, 5, 1)), [[7, 7], 7])
if N == 1: check('variant packet 1', solve(*[[179, 144, 179, 144], 3, 6, 2]), [[6, 3, 4, 4, 1, 3], 20])
if N == 2: check('variant packet 2', solve(*[[179, 144, 179, 144, 179, 144], 3, 9, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2], 29])
if N == 3: check('variant packet 3', solve(*[[179, 144, 179, 144, 179, 144, 179, 144], 3, 12, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2, 0, 5, 4], 38])
if N == 4: check('variant packet 4', solve(*[[179, 144, 179, 144, 179, 144, 179, 144, 179, 144], 3, 15, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2, 0, 5, 4, 7, 1, 0], 47])
if N == 5: check('variant packet 5', solve(*[[179, 144, 179, 144, 179, 144, 179, 144, 179, 144, 179, 144], 3, 18, 2]), [[6, 3, 4, 4, 1, 3, 1, 6, 2, 0, 5, 4, 7, 1, 0, 2, 6, 3], 56])
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	`[[6, 3, 4], 18]`	`[[6, 3, 4], 11]`	Failed
oracle 2	`[[3, 3], 8]`	`[[3, 3], 4]`	Failed
oracle 3	`[[0, 0, 0, 0, 0, 0, 0, 0], 8]`	`[[0, 0, 0, 0, 0, 0, 0, 0], 8]`	Passed
oracle 4	`[[], 0]`	`[[], 0]`	Passed
oracle 5	`[[2], 9]`	`[[2], 4]`	Failed
oracle 6	`[[2, 3], 20]`	`[[2, 3], 12]`	Failed
oracle 7	`[[7, 7], 9]`	`[[7, 7], 7]`	Failed
variant packet 1	`[[6, 3, 4, 4, 1, 3], 34]`	`[[6, 3, 4, 4, 1, 3], 20]`	Failed

SHA-256 / 75d3e9e39ccd6d8c9fb55bd82a7c6bb10928e88df733969c55f330ed9b4072b2

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 2026-09-29T14:44:54.777230+00:00.

Case digest / 51008363f680a9fbdcd2c76ecff0d913820e07aa253bce04de55364fada4f020