FAILURE MAP
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FA-78576 / Broadcast timecode arithmetic / Open access

Reverse telecine field attribution: field order swap · case 01

Lower-field-first material reports the same film frame for both fields.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The swap for lower-first order overwrites instead of exchanging.

VERIFIED REPAIR

Exchange the two field attributions for lower-first order.

Unsuccessful approach: The partial swap duplicates the first field.

Case contract

Fields carry film frames in A2 B3 C2 D3 cadence; film frame 0 has cadence position phase and starts at field 0. Video frame v consists of fields 2v and 2v+1. For order "upper" field 2v is the top field; for "lower" field 2v is the bottom field. Return [film frame in top field, film frame in bottom field, "clean" or "mixed"]; a negative v returns None.

Why this case matters

Timecode arithmetic errors misplace edits, commercial breaks and captions against the broadcast clock.

1 / The failure

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

N = 1
observations = []
def solve(v, phase, order):
    if v<0:
        return None
    base=[0,2,5,7][phase]
    def film(f):
        g,w=divmod(f+base,10)
        return 4*g+[0,0,1,1,1,2,2,3,3,3][w]-phase
    top,bottom=film(2*v),film(2*v+1)
    if order=='lower':
        top=bottom
    return [top,bottom,'clean' if top==bottom else 'mixed']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: field order swap', [2, 0, 'lower'], [2, 1, 'mixed']), ('regression variant: field order swap', [13, 0, 'lower'], [11, 10, 'mixed']), ('partial repair probe: field order swap', [23, 0, 'lower'], [19, 18, 'mixed']), ('partial repair variant: field order swap', [1, 3, 'lower'], [1, 0, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('normal control', [2, 0, 'upper'], [1, 2, 'mixed']), ('normal control', [16, 3, 'upper'], [12, 13, 'mixed']), ('normal control', [10, 2, 'upper'], [8, 8, 'clean'])], [('regression: field order swap', [12, 3, 'lower'], [10, 9, 'mixed']), ('regression variant: field order swap', [21, 3, 'lower'], [17, 16, 'mixed']), ('partial repair probe: field order swap', [28, 2, 'lower'], [23, 22, 'mixed']), ('partial repair variant: field order swap', [2, 1, 'lower'], [2, 1, 'mixed']), ('boundary control', [2, 0, 'upper'], [1, 2, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('normal control', [30, 3, 'lower'], [24, 24, 'clean']), ('normal control', [20, 2, 'upper'], [16, 16, 'clean']), ('normal control', [29, 1, 'lower'], [23, 23, 'clean'])], [('regression: field order swap', [23, 0, 'lower'], [19, 18, 'mixed']), ('regression variant: field order swap', [22, 2, 'lower'], [18, 17, 'mixed']), ('partial repair probe: field order swap', [3, 2, 'lower'], [3, 2, 'mixed']), ('partial repair variant: field order swap', [27, 2, 'lower'], [22, 21, 'mixed']), ('boundary control', [0, 1, 'upper'], [0, 0, 'clean']), ('boundary control', [2, 0, 'upper'], [1, 2, 'mixed']), ('normal control', [1, 0, 'upper'], [1, 1, 'clean']), ('normal control', [25, 0, 'upper'], [20, 20, 'clean']), ('normal control', [22, 3, 'upper'], [17, 18, 'mixed'])], [('regression: field order swap', [28, 2, 'lower'], [23, 22, 'mixed']), ('regression variant: field order swap', [2, 3, 'lower'], [2, 1, 'mixed']), ('partial repair probe: field order swap', [13, 0, 'lower'], [11, 10, 'mixed']), ('partial repair variant: field order swap', [11, 3, 'lower'], [9, 8, 'mixed']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('boundary control', [0, 1, 'upper'], [0, 0, 'clean']), ('normal control', [16, 2, 'lower'], [13, 13, 'clean']), ('normal control', [19, 1, 'lower'], [15, 15, 'clean']), ('normal control', [17, 2, 'upper'], [13, 14, 'mixed'])], [('regression: field order swap', [3, 2, 'lower'], [3, 2, 'mixed']), ('regression variant: field order swap', [1, 3, 'lower'], [1, 0, 'mixed']), ('partial repair probe: field order swap', [21, 3, 'lower'], [17, 16, 'mixed']), ('partial repair variant: field order swap', [27, 3, 'lower'], [22, 21, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('normal control', [25, 2, 'lower'], [20, 20, 'clean']), ('normal control', [6, 2, 'upper'], [5, 5, 'clean']), ('normal control', [19, 2, 'upper'], [15, 15, 'clean'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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
regression: field order swap[2, 2, 'clean'][2, 1, 'mixed']Failed
regression variant: field order swap[11, 11, 'clean'][11, 10, 'mixed']Failed
partial repair probe: field order swap[19, 19, 'clean'][19, 18, 'mixed']Failed
partial repair variant: field order swap[1, 1, 'clean'][1, 0, 'mixed']Failed
boundary control[0, 0, 'clean'][0, 0, 'clean']Passed
boundary control[3, 3, 'clean'][3, 3, 'clean']Passed
normal control[1, 2, 'mixed'][1, 2, 'mixed']Passed
normal control[12, 13, 'mixed'][12, 13, 'mixed']Passed
normal control[8, 8, 'clean'][8, 8, 'clean']Passed

SHA-256 / 1f8689984b4ad3db6f1d7e61c755fabf63d01d606821c18c78a48cb57e9e25b4

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(v, phase, order):
    if v<0:
        return None
    base=[0,2,5,7][phase]
    def film(f):
        g,w=divmod(f+base,10)
        return 4*g+[0,0,1,1,1,2,2,3,3,3][w]-phase
    top,bottom=film(2*v),film(2*v+1)
    if order=='lower':
        bottom,top=top,top
    return [top,bottom,'clean' if top==bottom else 'mixed']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: field order swap', [2, 0, 'lower'], [2, 1, 'mixed']), ('regression variant: field order swap', [13, 0, 'lower'], [11, 10, 'mixed']), ('partial repair probe: field order swap', [23, 0, 'lower'], [19, 18, 'mixed']), ('partial repair variant: field order swap', [1, 3, 'lower'], [1, 0, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('normal control', [2, 0, 'upper'], [1, 2, 'mixed']), ('normal control', [16, 3, 'upper'], [12, 13, 'mixed']), ('normal control', [10, 2, 'upper'], [8, 8, 'clean'])], [('regression: field order swap', [12, 3, 'lower'], [10, 9, 'mixed']), ('regression variant: field order swap', [21, 3, 'lower'], [17, 16, 'mixed']), ('partial repair probe: field order swap', [28, 2, 'lower'], [23, 22, 'mixed']), ('partial repair variant: field order swap', [2, 1, 'lower'], [2, 1, 'mixed']), ('boundary control', [2, 0, 'upper'], [1, 2, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('normal control', [30, 3, 'lower'], [24, 24, 'clean']), ('normal control', [20, 2, 'upper'], [16, 16, 'clean']), ('normal control', [29, 1, 'lower'], [23, 23, 'clean'])], [('regression: field order swap', [23, 0, 'lower'], [19, 18, 'mixed']), ('regression variant: field order swap', [22, 2, 'lower'], [18, 17, 'mixed']), ('partial repair probe: field order swap', [3, 2, 'lower'], [3, 2, 'mixed']), ('partial repair variant: field order swap', [27, 2, 'lower'], [22, 21, 'mixed']), ('boundary control', [0, 1, 'upper'], [0, 0, 'clean']), ('boundary control', [2, 0, 'upper'], [1, 2, 'mixed']), ('normal control', [1, 0, 'upper'], [1, 1, 'clean']), ('normal control', [25, 0, 'upper'], [20, 20, 'clean']), ('normal control', [22, 3, 'upper'], [17, 18, 'mixed'])], [('regression: field order swap', [28, 2, 'lower'], [23, 22, 'mixed']), ('regression variant: field order swap', [2, 3, 'lower'], [2, 1, 'mixed']), ('partial repair probe: field order swap', [13, 0, 'lower'], [11, 10, 'mixed']), ('partial repair variant: field order swap', [11, 3, 'lower'], [9, 8, 'mixed']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('boundary control', [0, 1, 'upper'], [0, 0, 'clean']), ('normal control', [16, 2, 'lower'], [13, 13, 'clean']), ('normal control', [19, 1, 'lower'], [15, 15, 'clean']), ('normal control', [17, 2, 'upper'], [13, 14, 'mixed'])], [('regression: field order swap', [3, 2, 'lower'], [3, 2, 'mixed']), ('regression variant: field order swap', [1, 3, 'lower'], [1, 0, 'mixed']), ('partial repair probe: field order swap', [21, 3, 'lower'], [17, 16, 'mixed']), ('partial repair variant: field order swap', [27, 3, 'lower'], [22, 21, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('normal control', [25, 2, 'lower'], [20, 20, 'clean']), ('normal control', [6, 2, 'upper'], [5, 5, 'clean']), ('normal control', [19, 2, 'upper'], [15, 15, 'clean'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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
regression: field order swap[1, 1, 'clean'][2, 1, 'mixed']Failed
regression variant: field order swap[10, 10, 'clean'][11, 10, 'mixed']Failed
partial repair probe: field order swap[18, 18, 'clean'][19, 18, 'mixed']Failed
partial repair variant: field order swap[0, 0, 'clean'][1, 0, 'mixed']Failed
boundary control[0, 0, 'clean'][0, 0, 'clean']Passed
boundary control[3, 3, 'clean'][3, 3, 'clean']Passed
normal control[1, 2, 'mixed'][1, 2, 'mixed']Passed
normal control[12, 13, 'mixed'][12, 13, 'mixed']Passed
normal control[8, 8, 'clean'][8, 8, 'clean']Passed

SHA-256 / 93eda68412ede8e7f8041f4d65cfab7cf941137ae130c115fb7ed61a129f47a5

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(v, phase, order):
    if v<0:
        return None
    base=[0,2,5,7][phase]
    def film(f):
        g,w=divmod(f+base,10)
        return 4*g+[0,0,1,1,1,2,2,3,3,3][w]-phase
    top,bottom=film(2*v),film(2*v+1)
    if order=='lower':
        top,bottom=bottom,top
    return [top,bottom,'clean' if top==bottom else 'mixed']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: field order swap', [2, 0, 'lower'], [2, 1, 'mixed']), ('regression variant: field order swap', [13, 0, 'lower'], [11, 10, 'mixed']), ('partial repair probe: field order swap', [23, 0, 'lower'], [19, 18, 'mixed']), ('partial repair variant: field order swap', [1, 3, 'lower'], [1, 0, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('normal control', [2, 0, 'upper'], [1, 2, 'mixed']), ('normal control', [16, 3, 'upper'], [12, 13, 'mixed']), ('normal control', [10, 2, 'upper'], [8, 8, 'clean'])], [('regression: field order swap', [12, 3, 'lower'], [10, 9, 'mixed']), ('regression variant: field order swap', [21, 3, 'lower'], [17, 16, 'mixed']), ('partial repair probe: field order swap', [28, 2, 'lower'], [23, 22, 'mixed']), ('partial repair variant: field order swap', [2, 1, 'lower'], [2, 1, 'mixed']), ('boundary control', [2, 0, 'upper'], [1, 2, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('normal control', [30, 3, 'lower'], [24, 24, 'clean']), ('normal control', [20, 2, 'upper'], [16, 16, 'clean']), ('normal control', [29, 1, 'lower'], [23, 23, 'clean'])], [('regression: field order swap', [23, 0, 'lower'], [19, 18, 'mixed']), ('regression variant: field order swap', [22, 2, 'lower'], [18, 17, 'mixed']), ('partial repair probe: field order swap', [3, 2, 'lower'], [3, 2, 'mixed']), ('partial repair variant: field order swap', [27, 2, 'lower'], [22, 21, 'mixed']), ('boundary control', [0, 1, 'upper'], [0, 0, 'clean']), ('boundary control', [2, 0, 'upper'], [1, 2, 'mixed']), ('normal control', [1, 0, 'upper'], [1, 1, 'clean']), ('normal control', [25, 0, 'upper'], [20, 20, 'clean']), ('normal control', [22, 3, 'upper'], [17, 18, 'mixed'])], [('regression: field order swap', [28, 2, 'lower'], [23, 22, 'mixed']), ('regression variant: field order swap', [2, 3, 'lower'], [2, 1, 'mixed']), ('partial repair probe: field order swap', [13, 0, 'lower'], [11, 10, 'mixed']), ('partial repair variant: field order swap', [11, 3, 'lower'], [9, 8, 'mixed']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('boundary control', [0, 1, 'upper'], [0, 0, 'clean']), ('normal control', [16, 2, 'lower'], [13, 13, 'clean']), ('normal control', [19, 1, 'lower'], [15, 15, 'clean']), ('normal control', [17, 2, 'upper'], [13, 14, 'mixed'])], [('regression: field order swap', [3, 2, 'lower'], [3, 2, 'mixed']), ('regression variant: field order swap', [1, 3, 'lower'], [1, 0, 'mixed']), ('partial repair probe: field order swap', [21, 3, 'lower'], [17, 16, 'mixed']), ('partial repair variant: field order swap', [27, 3, 'lower'], [22, 21, 'mixed']), ('boundary control', [0, 0, 'upper'], [0, 0, 'clean']), ('boundary control', [4, 3, 'lower'], [3, 3, 'clean']), ('normal control', [25, 2, 'lower'], [20, 20, 'clean']), ('normal control', [6, 2, 'upper'], [5, 5, 'clean']), ('normal control', [19, 2, 'upper'], [15, 15, 'clean'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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
regression: field order swap[2, 1, 'mixed'][2, 1, 'mixed']Passed
regression variant: field order swap[11, 10, 'mixed'][11, 10, 'mixed']Passed
partial repair probe: field order swap[19, 18, 'mixed'][19, 18, 'mixed']Passed
partial repair variant: field order swap[1, 0, 'mixed'][1, 0, 'mixed']Passed
boundary control[0, 0, 'clean'][0, 0, 'clean']Passed
boundary control[3, 3, 'clean'][3, 3, 'clean']Passed
normal control[1, 2, 'mixed'][1, 2, 'mixed']Passed
normal control[12, 13, 'mixed'][12, 13, 'mixed']Passed
normal control[8, 8, 'clean'][8, 8, 'clean']Passed

SHA-256 / a22d8fcac84cc461f681fa2f6b9b9813df1e2f64bfddf79d9fdec93a7bebd655

Verification & scope

A deterministic bounded teaching model with a stipulated toy contract; it does not claim conformance to SMPTE or any broadcast standard. 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 2026-09-29T14:49:36.640673+00:00.

Case digest / 74628147b79ade0fbd8ef1e9c60467e2aa9c2ba73093b0fffeed9c86284e277f