FAILURE MAP
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FA-77966 / Subtitle cue timing / Open access

Minimum gap and chaining between cues: trim trigger · case 01

Cues with a tiny positive gap blink the screen for a couple of frames between lines.

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

ROOT CAUSE

Trimming only happens for overlaps (gap<0), not for gaps shorter than the minimum.

THE FAILURE

Trimming only happens for overlaps (gap<0), not for gaps shorter than the minimum.

Unsuccessful approach: Including touching cues still leaves every positive sub-minimum gap untouched.

Case contract

For sorted cues [start,end], compare each cue with the next start. If gap = next_start - end is below min_gap, the end is trimmed to next_start - min_gap but never below start+1. If min_gap <= gap < chain, the end is extended to next_start - min_gap. Larger gaps are untouched.

Why this case matters

Subtitle timing defects shift, hide or overlap captions that viewers depend on for comprehension and accessibility.

1 / The failure

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

N = 1
observations = []
def solve(cues, min_gap, chain):
    out=[list(c) for c in cues]
    for i in range(len(out)-1):
        cur=out[i]
        nxt_start=out[i+1][0]
        gap=nxt_start-cur[1]
        if gap<0:
            cur[1]=max(cur[0]+1,nxt_start-min_gap)
        elif gap<chain:
            cur[1]=nxt_start-min_gap
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: trim trigger', [[[0, 100], [100, 500], [799, 1199]], 120, 300], [[0, 1], [100, 679], [799, 1199]]), ('regression variant: trim trigger', [[[1000, 3000], [2950, 3050], [3055, 3155], [3904, 4904], [4854, 5854]], 120, 750], [[1000, 2830], [2950, 2951], [3055, 3784], [3904, 4734], [4854, 5854]]), ('partial repair probe: trim trigger', [[[1000, 2000], [2005, 4005], [4305, 4405], [4410, 4810], [5230, 6230]], 120, 300], [[1000, 1885], [2005, 4005], [4305, 4306], [4410, 4810], [5230, 6230]]), ('partial repair variant: trim trigger', [[[0, 400], [900, 1000], [1005, 3005], [3625, 4025], [4525, 4925]], 120, 500], [[0, 400], [900, 901], [1005, 3005], [3625, 4025], [4525, 4925]]), ('boundary control', [[[0, 1000], [1050, 2000]], 100, 500], [[0, 950], [1050, 2000]]), ('boundary control', [[[0, 1000], [900, 2000]], 100, 500], [[0, 800], [900, 2000]]), ('normal control', [[[0, 1000], [1400, 2000]], 100, 500], [[0, 1300], [1400, 2000]]), ('normal control', [[[0, 400], [1400, 2400]], 80, 750], [[0, 400], [1400, 2400]]), ('normal control', [[[0, 100], [183, 2183], [3183, 3283], [3784, 5784]], 83, 500], [[0, 100], [183, 2183], [3183, 3283], [3784, 5784]])], [('regression: trim trigger', [[[0, 1000], [1300, 1700], [1700, 2100], [2221, 2321], [2321, 2421]], 120, 300], [[0, 1000], [1300, 1580], [1700, 2101], [2221, 2222], [2321, 2421]]), ('regression variant: trim trigger', [[[1000, 2000], [2005, 4005], [4305, 4405], [4410, 4810], [5230, 6230]], 120, 300], [[1000, 1885], [2005, 4005], [4305, 4306], [4410, 4810], [5230, 6230]]), ('partial repair probe: trim trigger', [[[0, 400], [900, 1000], [1005, 3005], [3625, 4025], [4525, 4925]], 120, 500], [[0, 400], [900, 901], [1005, 3005], [3625, 4025], [4525, 4925]]), ('partial repair variant: trim trigger', [[[1000, 2000], [2121, 3121], [3421, 4421], [4426, 4526], [4531, 6531]], 120, 300], [[1000, 2001], [2121, 3121], [3421, 4306], [4426, 4427], [4531, 6531]]), ('boundary control', [[[0, 1000], [1400, 2000]], 100, 500], [[0, 1300], [1400, 2000]]), ('boundary control', [[[0, 1000], [1050, 2000]], 100, 500], [[0, 950], [1050, 2000]]), ('normal control', [[[0, 1000], [1005, 1105]], 100, 750], [[0, 905], [1005, 1105]]), ('normal control', [[[1000, 1400], [1499, 1899], [2398, 2498], [2399, 2799], [2900, 3900]], 100, 500], [[1000, 1399], [1499, 2298], [2398, 2399], [2399, 2800], [2900, 3900]]), ('normal control', [[[1000, 2000], [2030, 2430]], 83, 300], [[1000, 1947], [2030, 2430]])], [('regression: trim trigger', [[[1000, 1100], [1050, 1150], [1155, 1255], [1376, 1476]], 120, 750], [[1000, 1001], [1050, 1051], [1155, 1256], [1376, 1476]]), ('regression variant: trim trigger', [[[1000, 1100], [1130, 1230], [1230, 3230]], 100, 500], [[1000, 1030], [1130, 1131], [1230, 3230]]), ('partial repair probe: trim trigger', [[[1000, 2000], [2121, 3121], [3421, 4421], [4426, 4526], [4531, 6531]], 120, 300], [[1000, 2001], [2121, 3121], [3421, 4306], [4426, 4427], [4531, 6531]]), ('partial repair variant: trim trigger', [[[1000, 2000], [3000, 5000], [5030, 6030], [6781, 6881], [6886, 8886]], 120, 750], [[1000, 2000], [3000, 4910], [5030, 6030], [6781, 6782], [6886, 8886]]), ('boundary control', [[[0, 1000], [1500, 2000]], 100, 500], [[0, 1000], [1500, 2000]]), ('boundary control', [[[0, 1000], [1400, 2000]], 100, 500], [[0, 1300], [1400, 2000]]), ('normal control', [[[0, 100], [199, 1199], [999, 1999], [2004, 3004]], 100, 750], [[0, 99], [199, 899], [999, 1904], [2004, 3004]]), ('normal control', [[[0, 400], [1270, 1370], [2240, 2340]], 120, 750], [[0, 400], [1270, 1370], [2240, 2340]]), ('normal control', [[[1000, 3000], [4000, 6000], [6030, 6430], [6230, 8230], [8030, 10030]], 80, 750], [[1000, 3000], [4000, 5950], [6030, 6150], [6230, 7950], [8030, 10030]])], [('regression: trim trigger', [[[0, 2000], [3000, 3400], [3800, 3900], [3900, 4900]], 100, 300], [[0, 2000], [3000, 3400], [3800, 3801], [3900, 4900]]), ('regression variant: trim trigger', [[[1000, 1100], [1100, 1200], [1319, 1419], [1419, 1819]], 120, 500], [[1000, 1001], [1100, 1199], [1319, 1320], [1419, 1819]]), ('partial repair probe: trim trigger', [[[1000, 2000], [3000, 5000], [5030, 6030], [6781, 6881], [6886, 8886]], 120, 750], [[1000, 2000], [3000, 4910], [5030, 6030], [6781, 6782], [6886, 8886]]), ('partial repair variant: trim trigger', [[[1000, 1100], [1050, 1150], [1155, 1255], [1376, 1476]], 120, 750], [[1000, 1001], [1050, 1051], [1155, 1256], [1376, 1476]]), ('boundary control', [[[0, 1000], [900, 2000]], 100, 500], [[0, 800], [900, 2000]]), ('boundary control', [[[0, 1000], [1500, 2000]], 100, 500], [[0, 1000], [1500, 2000]]), ('normal control', [[[0, 2000], [2499, 3499], [3598, 3698]], 100, 500], [[0, 2399], [2499, 3498], [3598, 3698]]), ('normal control', [[[0, 2000], [2830, 3830], [3911, 4911], [5741, 6141], [6891, 8891]], 80, 750], [[0, 2000], [2830, 3831], [3911, 4911], [5741, 6141], [6891, 8891]]), ('normal control', [[[0, 1000], [2000, 2400], [2899, 2999]], 120, 500], [[0, 1000], [2000, 2779], [2899, 2999]])], [('regression: trim trigger', [[[0, 1000], [1749, 1849], [2719, 3119], [3869, 3969], [3969, 4069]], 120, 750], [[0, 1629], [1749, 1849], [2719, 3119], [3869, 3870], [3969, 4069]]), ('regression variant: trim trigger', [[[0, 1000], [1005, 1105], [1105, 2105]], 120, 500], [[0, 885], [1005, 1006], [1105, 2105]]), ('partial repair probe: trim trigger', [[[1000, 1100], [1050, 1150], [1155, 1255], [1376, 1476]], 120, 750], [[1000, 1001], [1050, 1051], [1155, 1256], [1376, 1476]]), ('partial repair variant: trim trigger', [[[1000, 3000], [2950, 3050], [3055, 3155], [3904, 4904], [4854, 5854]], 120, 750], [[1000, 2830], [2950, 2951], [3055, 3784], [3904, 4734], [4854, 5854]]), ('boundary control', [[[0, 1000], [1050, 2000]], 100, 500], [[0, 950], [1050, 2000]]), ('boundary control', [[[0, 1000], [900, 2000]], 100, 500], [[0, 800], [900, 2000]]), ('normal control', [[[0, 2000], [2083, 4083], [4113, 4513], [4896, 4996], [5295, 6295]], 83, 300], [[0, 2000], [2083, 4030], [4113, 4513], [4896, 5212], [5295, 6295]]), ('normal control', [[[1000, 1400], [2151, 4151], [3951, 5951], [5751, 6751], [6870, 6970]], 120, 750], [[1000, 1400], [2151, 3831], [3951, 5631], [5751, 6750], [6870, 6970]]), ('normal control', [[[0, 2000], [2000, 4000], [3950, 4950]], 100, 750], [[0, 1900], [2000, 3850], [3950, 4950]])]]
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: trim trigger[[0, -20], [100, 679], [799, 1199]][[0, 1], [100, 679], [799, 1199]]Failed
regression variant: trim trigger[[1000, 2830], [2950, 2935], [3055, 3784], [3904, 4734], [4854, 5854]][[1000, 2830], [2950, 2951], [3055, 3784], [3904, 4734], [4854, 5854]]Failed
partial repair probe: trim trigger[[1000, 1885], [2005, 4005], [4305, 4290], [4410, 4810], [5230, 6230]][[1000, 1885], [2005, 4005], [4305, 4306], [4410, 4810], [5230, 6230]]Failed
partial repair variant: trim trigger[[0, 400], [900, 885], [1005, 3005], [3625, 4025], [4525, 4925]][[0, 400], [900, 901], [1005, 3005], [3625, 4025], [4525, 4925]]Failed
boundary control[[0, 950], [1050, 2000]][[0, 950], [1050, 2000]]Passed
boundary control[[0, 800], [900, 2000]][[0, 800], [900, 2000]]Passed
normal control[[0, 1300], [1400, 2000]][[0, 1300], [1400, 2000]]Passed
normal control[[0, 400], [1400, 2400]][[0, 400], [1400, 2400]]Passed
normal control[[0, 100], [183, 2183], [3183, 3283], [3784, 5784]][[0, 100], [183, 2183], [3183, 3283], [3784, 5784]]Passed

SHA-256 / 11ee6e52ba4b1b94c21f6fe021b420a89cf503d1097031bb32eb5134dcb01ac3

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(cues, min_gap, chain):
    out=[list(c) for c in cues]
    for i in range(len(out)-1):
        cur=out[i]
        nxt_start=out[i+1][0]
        gap=nxt_start-cur[1]
        if gap<=0:
            cur[1]=max(cur[0]+1,nxt_start-min_gap)
        elif gap<chain:
            cur[1]=nxt_start-min_gap
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: trim trigger', [[[0, 100], [100, 500], [799, 1199]], 120, 300], [[0, 1], [100, 679], [799, 1199]]), ('regression variant: trim trigger', [[[1000, 3000], [2950, 3050], [3055, 3155], [3904, 4904], [4854, 5854]], 120, 750], [[1000, 2830], [2950, 2951], [3055, 3784], [3904, 4734], [4854, 5854]]), ('partial repair probe: trim trigger', [[[1000, 2000], [2005, 4005], [4305, 4405], [4410, 4810], [5230, 6230]], 120, 300], [[1000, 1885], [2005, 4005], [4305, 4306], [4410, 4810], [5230, 6230]]), ('partial repair variant: trim trigger', [[[0, 400], [900, 1000], [1005, 3005], [3625, 4025], [4525, 4925]], 120, 500], [[0, 400], [900, 901], [1005, 3005], [3625, 4025], [4525, 4925]]), ('boundary control', [[[0, 1000], [1050, 2000]], 100, 500], [[0, 950], [1050, 2000]]), ('boundary control', [[[0, 1000], [900, 2000]], 100, 500], [[0, 800], [900, 2000]]), ('normal control', [[[0, 1000], [1400, 2000]], 100, 500], [[0, 1300], [1400, 2000]]), ('normal control', [[[0, 400], [1400, 2400]], 80, 750], [[0, 400], [1400, 2400]]), ('normal control', [[[0, 100], [183, 2183], [3183, 3283], [3784, 5784]], 83, 500], [[0, 100], [183, 2183], [3183, 3283], [3784, 5784]])], [('regression: trim trigger', [[[0, 1000], [1300, 1700], [1700, 2100], [2221, 2321], [2321, 2421]], 120, 300], [[0, 1000], [1300, 1580], [1700, 2101], [2221, 2222], [2321, 2421]]), ('regression variant: trim trigger', [[[1000, 2000], [2005, 4005], [4305, 4405], [4410, 4810], [5230, 6230]], 120, 300], [[1000, 1885], [2005, 4005], [4305, 4306], [4410, 4810], [5230, 6230]]), ('partial repair probe: trim trigger', [[[0, 400], [900, 1000], [1005, 3005], [3625, 4025], [4525, 4925]], 120, 500], [[0, 400], [900, 901], [1005, 3005], [3625, 4025], [4525, 4925]]), ('partial repair variant: trim trigger', [[[1000, 2000], [2121, 3121], [3421, 4421], [4426, 4526], [4531, 6531]], 120, 300], [[1000, 2001], [2121, 3121], [3421, 4306], [4426, 4427], [4531, 6531]]), ('boundary control', [[[0, 1000], [1400, 2000]], 100, 500], [[0, 1300], [1400, 2000]]), ('boundary control', [[[0, 1000], [1050, 2000]], 100, 500], [[0, 950], [1050, 2000]]), ('normal control', [[[0, 1000], [1005, 1105]], 100, 750], [[0, 905], [1005, 1105]]), ('normal control', [[[1000, 1400], [1499, 1899], [2398, 2498], [2399, 2799], [2900, 3900]], 100, 500], [[1000, 1399], [1499, 2298], [2398, 2399], [2399, 2800], [2900, 3900]]), ('normal control', [[[1000, 2000], [2030, 2430]], 83, 300], [[1000, 1947], [2030, 2430]])], [('regression: trim trigger', [[[1000, 1100], [1050, 1150], [1155, 1255], [1376, 1476]], 120, 750], [[1000, 1001], [1050, 1051], [1155, 1256], [1376, 1476]]), ('regression variant: trim trigger', [[[1000, 1100], [1130, 1230], [1230, 3230]], 100, 500], [[1000, 1030], [1130, 1131], [1230, 3230]]), ('partial repair probe: trim trigger', [[[1000, 2000], [2121, 3121], [3421, 4421], [4426, 4526], [4531, 6531]], 120, 300], [[1000, 2001], [2121, 3121], [3421, 4306], [4426, 4427], [4531, 6531]]), ('partial repair variant: trim trigger', [[[1000, 2000], [3000, 5000], [5030, 6030], [6781, 6881], [6886, 8886]], 120, 750], [[1000, 2000], [3000, 4910], [5030, 6030], [6781, 6782], [6886, 8886]]), ('boundary control', [[[0, 1000], [1500, 2000]], 100, 500], [[0, 1000], [1500, 2000]]), ('boundary control', [[[0, 1000], [1400, 2000]], 100, 500], [[0, 1300], [1400, 2000]]), ('normal control', [[[0, 100], [199, 1199], [999, 1999], [2004, 3004]], 100, 750], [[0, 99], [199, 899], [999, 1904], [2004, 3004]]), ('normal control', [[[0, 400], [1270, 1370], [2240, 2340]], 120, 750], [[0, 400], [1270, 1370], [2240, 2340]]), ('normal control', [[[1000, 3000], [4000, 6000], [6030, 6430], [6230, 8230], [8030, 10030]], 80, 750], [[1000, 3000], [4000, 5950], [6030, 6150], [6230, 7950], [8030, 10030]])], [('regression: trim trigger', [[[0, 2000], [3000, 3400], [3800, 3900], [3900, 4900]], 100, 300], [[0, 2000], [3000, 3400], [3800, 3801], [3900, 4900]]), ('regression variant: trim trigger', [[[1000, 1100], [1100, 1200], [1319, 1419], [1419, 1819]], 120, 500], [[1000, 1001], [1100, 1199], [1319, 1320], [1419, 1819]]), ('partial repair probe: trim trigger', [[[1000, 2000], [3000, 5000], [5030, 6030], [6781, 6881], [6886, 8886]], 120, 750], [[1000, 2000], [3000, 4910], [5030, 6030], [6781, 6782], [6886, 8886]]), ('partial repair variant: trim trigger', [[[1000, 1100], [1050, 1150], [1155, 1255], [1376, 1476]], 120, 750], [[1000, 1001], [1050, 1051], [1155, 1256], [1376, 1476]]), ('boundary control', [[[0, 1000], [900, 2000]], 100, 500], [[0, 800], [900, 2000]]), ('boundary control', [[[0, 1000], [1500, 2000]], 100, 500], [[0, 1000], [1500, 2000]]), ('normal control', [[[0, 2000], [2499, 3499], [3598, 3698]], 100, 500], [[0, 2399], [2499, 3498], [3598, 3698]]), ('normal control', [[[0, 2000], [2830, 3830], [3911, 4911], [5741, 6141], [6891, 8891]], 80, 750], [[0, 2000], [2830, 3831], [3911, 4911], [5741, 6141], [6891, 8891]]), ('normal control', [[[0, 1000], [2000, 2400], [2899, 2999]], 120, 500], [[0, 1000], [2000, 2779], [2899, 2999]])], [('regression: trim trigger', [[[0, 1000], [1749, 1849], [2719, 3119], [3869, 3969], [3969, 4069]], 120, 750], [[0, 1629], [1749, 1849], [2719, 3119], [3869, 3870], [3969, 4069]]), ('regression variant: trim trigger', [[[0, 1000], [1005, 1105], [1105, 2105]], 120, 500], [[0, 885], [1005, 1006], [1105, 2105]]), ('partial repair probe: trim trigger', [[[1000, 1100], [1050, 1150], [1155, 1255], [1376, 1476]], 120, 750], [[1000, 1001], [1050, 1051], [1155, 1256], [1376, 1476]]), ('partial repair variant: trim trigger', [[[1000, 3000], [2950, 3050], [3055, 3155], [3904, 4904], [4854, 5854]], 120, 750], [[1000, 2830], [2950, 2951], [3055, 3784], [3904, 4734], [4854, 5854]]), ('boundary control', [[[0, 1000], [1050, 2000]], 100, 500], [[0, 950], [1050, 2000]]), ('boundary control', [[[0, 1000], [900, 2000]], 100, 500], [[0, 800], [900, 2000]]), ('normal control', [[[0, 2000], [2083, 4083], [4113, 4513], [4896, 4996], [5295, 6295]], 83, 300], [[0, 2000], [2083, 4030], [4113, 4513], [4896, 5212], [5295, 6295]]), ('normal control', [[[1000, 1400], [2151, 4151], [3951, 5951], [5751, 6751], [6870, 6970]], 120, 750], [[1000, 1400], [2151, 3831], [3951, 5631], [5751, 6750], [6870, 6970]]), ('normal control', [[[0, 2000], [2000, 4000], [3950, 4950]], 100, 750], [[0, 1900], [2000, 3850], [3950, 4950]])]]
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: trim trigger[[0, 1], [100, 679], [799, 1199]][[0, 1], [100, 679], [799, 1199]]Passed
regression variant: trim trigger[[1000, 2830], [2950, 2935], [3055, 3784], [3904, 4734], [4854, 5854]][[1000, 2830], [2950, 2951], [3055, 3784], [3904, 4734], [4854, 5854]]Failed
partial repair probe: trim trigger[[1000, 1885], [2005, 4005], [4305, 4290], [4410, 4810], [5230, 6230]][[1000, 1885], [2005, 4005], [4305, 4306], [4410, 4810], [5230, 6230]]Failed
partial repair variant: trim trigger[[0, 400], [900, 885], [1005, 3005], [3625, 4025], [4525, 4925]][[0, 400], [900, 901], [1005, 3005], [3625, 4025], [4525, 4925]]Failed
boundary control[[0, 950], [1050, 2000]][[0, 950], [1050, 2000]]Passed
boundary control[[0, 800], [900, 2000]][[0, 800], [900, 2000]]Passed
normal control[[0, 1300], [1400, 2000]][[0, 1300], [1400, 2000]]Passed
normal control[[0, 400], [1400, 2400]][[0, 400], [1400, 2400]]Passed
normal control[[0, 100], [183, 2183], [3183, 3283], [3784, 5784]][[0, 100], [183, 2183], [3183, 3283], [3784, 5784]]Passed

SHA-256 / 9aacc754a2d16b8eba66a635bbef94d9bddbd15b6fa6a5484c1c46bf2cb85d34

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 9 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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

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Verification & scope

A deterministic bounded teaching model with a stipulated toy contract; it does not claim conformance to any subtitle 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 2026-09-29T14:49:30.736791+00:00.

Case digest / 5d38af11f79b42921e9558c355b443c89cc338205e306d075d8224b2fd4fabc4