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FA-49346 / PCM sample encoding / Open access

Pcm channel predictor: feedback channel · case 01

Per-channel predictor update overwrites only the first state lane.

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

ROOT CAUSE

Per-channel predictor update overwrites only the first state lane.

THE FAILURE

Per-channel predictor update overwrites only the first state lane.

Unsuccessful approach: Feeding residual instead of amplitude corrupts later frames.

Case contract

Encode frame-major PCM residuals with independent per-channel amplitude predictors and frame-index resets; preserve residual frame shape.

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(frames, seeds, resets):
    state=list(seeds)
    out=[]
    for index,frame in enumerate(frames):
        if index in resets:
            state=list(seeds)
        residual=[]
        for channel,sample in enumerate(frame):
            residual.append(sample-state[channel])
            state[0]=sample
        out.append(residual)
    return [out,state]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([[5, 10], [7, 9]], [2, 8], [])), [[[3, 2], [2, -1]], [7, 9]])
check('oracle 2', solve(*([[2, 4], [3, 8], [7, 9]], [1, 2], [1])), [[[1, 2], [2, 6], [4, 1]], [7, 9]])
check('oracle 3', solve(*([], [3, 4], [])), [[], [3, 4]])
check('oracle 4', solve(*([[1], [3], [2]], [0], [2])), [[[1], [2], [2]], [2]])
check('oracle 5', solve(*([[-2, 3], [0, 1]], [-1, 4], [])), [[[-1, -1], [2, -2]], [0, 1]])
check('oracle 6', solve(*([[1, 2, 3]], [3, 2, 1], [0])), [[[-2, 0, 2]], [1, 2, 3]])
check('oracle 7', solve(*([[0, 0], [0, 0]], [1, -1], [])), [[[-1, 1], [0, 0]], [0, 0]])
if N == 1: check('variant packet 1', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 2: check('variant packet 2', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 3: check('variant packet 3', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 4: check('variant packet 4', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 5: check('variant packet 5', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
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[[[3, 2], [-3, 1]], [9, 8]][[[3, 2], [2, -1]], [7, 9]]Failed
oracle 2[[[1, 2], [2, 6], [-1, 7]], [9, 2]][[[1, 2], [2, 6], [4, 1]], [7, 9]]Failed
oracle 3[[], [3, 4]][[], [3, 4]]Passed
oracle 4[[[1], [2], [2]], [2]][[[1], [2], [2]], [2]]Passed
oracle 5[[[-1, -1], [-3, -3]], [1, 4]][[[-1, -1], [2, -2]], [0, 1]]Failed
oracle 6[[[-2, 0, 2]], [3, 2, 1]][[[-2, 0, 2]], [1, 2, 3]]Failed
oracle 7[[[-1, 1], [0, 1]], [0, -1]][[[-1, 1], [0, 0]], [0, 0]]Failed
variant packet 1[[[3, 2], [-3, 1], [-4, 2], [-3, 1]], [9, 8]][[[3, 2], [2, -1], [-2, 1], [2, -1]], [7, 9]]Failed

SHA-256 / 1af4740330fc18156a4349aa371c9953b3bde880031db0f9099e7a5a3a7094fc

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(frames, seeds, resets):
    state=list(seeds)
    out=[]
    for index,frame in enumerate(frames):
        if index in resets:
            state=list(seeds)
        residual=[]
        for channel,sample in enumerate(frame):
            residual.append(sample-state[channel])
            state[channel]=sample-state[channel]
        out.append(residual)
    return [out,state]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([[5, 10], [7, 9]], [2, 8], [])), [[[3, 2], [2, -1]], [7, 9]])
check('oracle 2', solve(*([[2, 4], [3, 8], [7, 9]], [1, 2], [1])), [[[1, 2], [2, 6], [4, 1]], [7, 9]])
check('oracle 3', solve(*([], [3, 4], [])), [[], [3, 4]])
check('oracle 4', solve(*([[1], [3], [2]], [0], [2])), [[[1], [2], [2]], [2]])
check('oracle 5', solve(*([[-2, 3], [0, 1]], [-1, 4], [])), [[[-1, -1], [2, -2]], [0, 1]])
check('oracle 6', solve(*([[1, 2, 3]], [3, 2, 1], [0])), [[[-2, 0, 2]], [1, 2, 3]])
check('oracle 7', solve(*([[0, 0], [0, 0]], [1, -1], [])), [[[-1, 1], [0, 0]], [0, 0]])
if N == 1: check('variant packet 1', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 2: check('variant packet 2', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 3: check('variant packet 3', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 4: check('variant packet 4', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
if N == 5: check('variant packet 5', solve(*[[[5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9], [5, 10], [7, 9]], [2, 8], []]), [[[3, 2], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1], [-2, 1], [2, -1]], [7, 9]])
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[[[3, 2], [4, 7]], [4, 7]][[[3, 2], [2, -1]], [7, 9]]Failed
oracle 2[[[1, 2], [2, 6], [5, 3]], [5, 3]][[[1, 2], [2, 6], [4, 1]], [7, 9]]Failed
oracle 3[[], [3, 4]][[], [3, 4]]Passed
oracle 4[[[1], [2], [2]], [2]][[[1], [2], [2]], [2]]Passed
oracle 5[[[-1, -1], [1, 2]], [1, 2]][[[-1, -1], [2, -2]], [0, 1]]Failed
oracle 6[[[-2, 0, 2]], [-2, 0, 2]][[[-2, 0, 2]], [1, 2, 3]]Failed
oracle 7[[[-1, 1], [1, -1]], [1, -1]][[[-1, 1], [0, 0]], [0, 0]]Failed
variant packet 1[[[3, 2], [4, 7], [1, 3], [6, 6]], [6, 6]][[[3, 2], [2, -1], [-2, 1], [2, -1]], [7, 9]]Failed

SHA-256 / 55d2e1144632f911b719c91dfa523cb3f8b03f3baec6cd37f482d47b89a35015

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 2026-09-29T14:44:59.248240+00:00.

Case digest / 309d0ec0a1fe3253a1cbc17b860ed66d97f0dbf2f142ab0c33cfc804e20af57c