FAILURE MAP
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FA-78261 / Subtitle cue timing / Open access

Pop-on caption buffer timing: text load target · case 01

Multi-part caption loads keep only the last text fragment.

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

ROOT CAUSE

Each TEXT command replaces non-displayed memory instead of appending.

THE FAILURE

Each TEXT command replaces non-displayed memory instead of appending.

Unsuccessful approach: Writing directly into displayed memory behaves like paint-on captions and breaks pop-on timing.

Case contract

Commands [frame,cmd] at integer fps (time = frame*1000//fps). TEXT:x appends x to the non-displayed memory; ENM erases non-displayed memory; EOC swaps displayed and non-displayed memories; EDM erases displayed memory. Whenever non-empty displayed text is replaced (EOC) or erased (EDM), emit [shown_since_ms, now_ms, text].

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(events, fps):
    shown=''
    hidden=''
    since=None
    out=[]
    for frame,cmd in events:
        t=frame*1000//fps
        if cmd.startswith('TEXT:'):
            hidden=cmd[5:]
        elif cmd=='ENM':
            hidden=''
        elif cmd=='EOC':
            if shown:
                out.append([since,t,shown])
            shown,hidden=hidden,shown
            since=t
        elif cmd=='EDM':
            if shown: out.append([since,t,shown])
            shown=''
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: text load target', [[[3, 'TEXT: there'], [32, 'TEXT: there'], [33, 'TEXT: there'], [48, 'EOC'], [78, 'EOC'], [123, 'TEXT: there']], 25], [[1920, 3120, ' there there there']]), ('regression variant: text load target', [[[30, 'TEXT:Hi'], [75, 'TEXT:Hi'], [120, 'EOC'], [135, 'TEXT:Hi'], [164, 'EDM'], [193, 'TEXT:Hi'], [238, 'EOC'], [267, 'EOC']], 25], [[4800, 6560, 'HiHi'], [9520, 10680, 'HiHi']]), ('partial repair probe: text load target', [[[0, 'EOC'], [7, 'TEXT:Bye'], [52, 'EDM'], [59, 'TEXT:Bye'], [74, 'EOC']], 24], []), ('partial repair variant: text load target', [[[30, 'TEXT: there'], [31, 'EDM']], 24], []), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[30, 'EOC'], [30, 'TEXT:Hi'], [37, 'ENM']], 24], []), ('normal control', [[[3, 'EDM'], [32, 'EOC']], 29], []), ('normal control', [[[0, 'ENM'], [0, 'EOC'], [30, 'TEXT:Hi']], 24], [])], [('regression: text load target', [[[3, 'TEXT:Hi'], [48, 'EOC'], [49, 'EOC'], [49, 'TEXT:Hi'], [94, 'TEXT:Bye'], [123, 'EOC'], [130, 'EDM']], 25], [[1920, 1960, 'Hi'], [4920, 5200, 'HiHiBye']]), ('regression variant: text load target', [[[30, 'TEXT:Hi'], [31, 'TEXT:Bye'], [61, 'EOC'], [91, 'TEXT:Bye'], [92, 'TEXT: there'], [93, 'ENM'], [93, 'TEXT:Hi'], [122, 'EOC']], 24], [[2541, 5083, 'HiBye']]), ('partial repair probe: text load target', [[[30, 'TEXT:Bye'], [37, 'EOC'], [52, 'EDM'], [52, 'ENM'], [67, 'EDM']], 30], [[1233, 1733, 'Bye']]), ('partial repair variant: text load target', [[[3, 'TEXT: there'], [32, 'TEXT: there'], [33, 'TEXT: there'], [48, 'EOC'], [78, 'EOC'], [123, 'TEXT: there']], 25], [[1920, 3120, ' there there there']]), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[0, 'EOC'], [7, 'EDM'], [14, 'EOC'], [59, 'EOC'], [104, 'EOC'], [133, 'EOC'], [162, 'EOC'], [207, 'EOC']], 25], []), ('normal control', [[[3, 'TEXT:Hi'], [10, 'TEXT:Bye']], 30], []), ('normal control', [[[3, 'EOC'], [18, 'EOC'], [19, 'EOC']], 25], [])], [('regression: text load target', [[[0, 'TEXT:Bye'], [29, 'TEXT: there'], [44, 'TEXT: there'], [44, 'EOC'], [51, 'EOC']], 29], [[1517, 1758, 'Bye there there']]), ('regression variant: text load target', [[[30, 'EOC'], [45, 'TEXT: there'], [75, 'TEXT:Hi'], [105, 'EOC'], [105, 'EOC']], 24], [[4375, 4375, ' thereHi']]), ('partial repair probe: text load target', [[[0, 'EOC'], [30, 'TEXT:Bye'], [31, 'EOC'], [46, 'EOC'], [91, 'TEXT:Hi'], [92, 'TEXT: there'], [99, 'EDM'], [129, 'ENM']], 30], [[1033, 1533, 'Bye']]), ('partial repair variant: text load target', [[[30, 'EOC'], [31, 'TEXT: there'], [31, 'EDM'], [76, 'TEXT:Bye'], [76, 'ENM'], [91, 'EDM']], 30], []), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[0, 'EOC'], [7, 'TEXT:Bye'], [14, 'TEXT:Bye']], 25], []), ('normal control', [[[30, 'EOC'], [60, 'TEXT: there']], 29], []), ('normal control', [[[0, 'EOC'], [1, 'EOC'], [30, 'ENM'], [37, 'TEXT:Bye']], 30], [])], [('regression: text load target', [[[30, 'TEXT:Hi'], [30, 'TEXT:Bye'], [60, 'TEXT:Bye'], [105, 'EOC'], [120, 'EOC'], [165, 'EOC'], [180, 'TEXT: there'], [195, 'EDM']], 24], [[4375, 5000, 'HiByeBye'], [6875, 8125, 'HiByeBye']]), ('regression variant: text load target', [[[0, 'EOC'], [0, 'TEXT: there'], [45, 'TEXT:Hi'], [46, 'EOC'], [91, 'EDM'], [120, 'TEXT:Hi'], [127, 'TEXT: there']], 25], [[1840, 3640, ' thereHi']]), ('partial repair probe: text load target', [[[30, 'TEXT:Hi'], [31, 'TEXT: there'], [61, 'EDM'], [106, 'TEXT: there'], [121, 'ENM'], [136, 'TEXT:Hi'], [166, 'EOC']], 24], []), ('partial repair variant: text load target', [[[30, 'TEXT:Bye'], [59, 'EOC'], [66, 'TEXT:Bye'], [111, 'EOC']], 24], [[2458, 4625, 'Bye']]), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[0, 'EDM'], [15, 'TEXT:Bye']], 29], []), ('normal control', [[[3, 'EOC'], [48, 'ENM']], 30], []), ('normal control', [[[3, 'TEXT:Bye'], [48, 'TEXT:Hi']], 24], [])], [('regression: text load target', [[[3, 'EOC'], [3, 'TEXT: there'], [4, 'TEXT: there'], [34, 'EDM'], [64, 'EOC'], [71, 'EOC'], [78, 'TEXT: there'], [78, 'TEXT: there']], 30], [[2133, 2366, ' there there']]), ('regression variant: text load target', [[[0, 'TEXT: there'], [29, 'TEXT:Bye'], [44, 'EDM'], [73, 'EOC'], [118, 'EOC'], [163, 'TEXT: there'], [192, 'ENM']], 25], [[2920, 4720, ' thereBye']]), ('partial repair probe: text load target', [[[30, 'TEXT: there'], [30, 'EOC'], [59, 'ENM']], 30], []), ('partial repair variant: text load target', [[[0, 'TEXT: there'], [7, 'ENM'], [8, 'EOC'], [9, 'ENM'], [16, 'TEXT:Hi']], 30], []), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[3, 'EOC'], [4, 'EOC'], [19, 'EOC'], [20, 'EOC'], [21, 'EOC'], [51, 'EDM'], [58, 'EDM'], [58, 'EOC']], 24], []), ('normal control', [[[0, 'TEXT:Bye'], [30, 'ENM'], [59, 'TEXT:Bye'], [104, 'ENM'], [119, 'ENM'], [148, 'TEXT:Bye'], [178, 'ENM']], 30], []), ('normal control', [[[3, 'EOC'], [48, 'EOC'], [55, 'TEXT: there']], 24], [])]]
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: text load target[[1920, 3120, ' there']][[1920, 3120, ' there there there']]Failed
regression variant: text load target[[4800, 6560, 'Hi'], [9520, 10680, 'Hi']][[4800, 6560, 'HiHi'], [9520, 10680, 'HiHi']]Failed
partial repair probe: text load target[][]Passed
partial repair variant: text load target[][]Passed
boundary control[][]Passed
normal control[][]Passed
normal control[][]Passed
normal control[][]Passed

SHA-256 / 2e9256284ab8c623e50cbc455e4ebd86fb9a52a9ab04bf530548000ac51fcbc8

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(events, fps):
    shown=''
    hidden=''
    since=None
    out=[]
    for frame,cmd in events:
        t=frame*1000//fps
        if cmd.startswith('TEXT:'):
            shown+=cmd[5:]
        elif cmd=='ENM':
            hidden=''
        elif cmd=='EOC':
            if shown:
                out.append([since,t,shown])
            shown,hidden=hidden,shown
            since=t
        elif cmd=='EDM':
            if shown: out.append([since,t,shown])
            shown=''
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: text load target', [[[3, 'TEXT: there'], [32, 'TEXT: there'], [33, 'TEXT: there'], [48, 'EOC'], [78, 'EOC'], [123, 'TEXT: there']], 25], [[1920, 3120, ' there there there']]), ('regression variant: text load target', [[[30, 'TEXT:Hi'], [75, 'TEXT:Hi'], [120, 'EOC'], [135, 'TEXT:Hi'], [164, 'EDM'], [193, 'TEXT:Hi'], [238, 'EOC'], [267, 'EOC']], 25], [[4800, 6560, 'HiHi'], [9520, 10680, 'HiHi']]), ('partial repair probe: text load target', [[[0, 'EOC'], [7, 'TEXT:Bye'], [52, 'EDM'], [59, 'TEXT:Bye'], [74, 'EOC']], 24], []), ('partial repair variant: text load target', [[[30, 'TEXT: there'], [31, 'EDM']], 24], []), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[30, 'EOC'], [30, 'TEXT:Hi'], [37, 'ENM']], 24], []), ('normal control', [[[3, 'EDM'], [32, 'EOC']], 29], []), ('normal control', [[[0, 'ENM'], [0, 'EOC'], [30, 'TEXT:Hi']], 24], [])], [('regression: text load target', [[[3, 'TEXT:Hi'], [48, 'EOC'], [49, 'EOC'], [49, 'TEXT:Hi'], [94, 'TEXT:Bye'], [123, 'EOC'], [130, 'EDM']], 25], [[1920, 1960, 'Hi'], [4920, 5200, 'HiHiBye']]), ('regression variant: text load target', [[[30, 'TEXT:Hi'], [31, 'TEXT:Bye'], [61, 'EOC'], [91, 'TEXT:Bye'], [92, 'TEXT: there'], [93, 'ENM'], [93, 'TEXT:Hi'], [122, 'EOC']], 24], [[2541, 5083, 'HiBye']]), ('partial repair probe: text load target', [[[30, 'TEXT:Bye'], [37, 'EOC'], [52, 'EDM'], [52, 'ENM'], [67, 'EDM']], 30], [[1233, 1733, 'Bye']]), ('partial repair variant: text load target', [[[3, 'TEXT: there'], [32, 'TEXT: there'], [33, 'TEXT: there'], [48, 'EOC'], [78, 'EOC'], [123, 'TEXT: there']], 25], [[1920, 3120, ' there there there']]), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[0, 'EOC'], [7, 'EDM'], [14, 'EOC'], [59, 'EOC'], [104, 'EOC'], [133, 'EOC'], [162, 'EOC'], [207, 'EOC']], 25], []), ('normal control', [[[3, 'TEXT:Hi'], [10, 'TEXT:Bye']], 30], []), ('normal control', [[[3, 'EOC'], [18, 'EOC'], [19, 'EOC']], 25], [])], [('regression: text load target', [[[0, 'TEXT:Bye'], [29, 'TEXT: there'], [44, 'TEXT: there'], [44, 'EOC'], [51, 'EOC']], 29], [[1517, 1758, 'Bye there there']]), ('regression variant: text load target', [[[30, 'EOC'], [45, 'TEXT: there'], [75, 'TEXT:Hi'], [105, 'EOC'], [105, 'EOC']], 24], [[4375, 4375, ' thereHi']]), ('partial repair probe: text load target', [[[0, 'EOC'], [30, 'TEXT:Bye'], [31, 'EOC'], [46, 'EOC'], [91, 'TEXT:Hi'], [92, 'TEXT: there'], [99, 'EDM'], [129, 'ENM']], 30], [[1033, 1533, 'Bye']]), ('partial repair variant: text load target', [[[30, 'EOC'], [31, 'TEXT: there'], [31, 'EDM'], [76, 'TEXT:Bye'], [76, 'ENM'], [91, 'EDM']], 30], []), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[0, 'EOC'], [7, 'TEXT:Bye'], [14, 'TEXT:Bye']], 25], []), ('normal control', [[[30, 'EOC'], [60, 'TEXT: there']], 29], []), ('normal control', [[[0, 'EOC'], [1, 'EOC'], [30, 'ENM'], [37, 'TEXT:Bye']], 30], [])], [('regression: text load target', [[[30, 'TEXT:Hi'], [30, 'TEXT:Bye'], [60, 'TEXT:Bye'], [105, 'EOC'], [120, 'EOC'], [165, 'EOC'], [180, 'TEXT: there'], [195, 'EDM']], 24], [[4375, 5000, 'HiByeBye'], [6875, 8125, 'HiByeBye']]), ('regression variant: text load target', [[[0, 'EOC'], [0, 'TEXT: there'], [45, 'TEXT:Hi'], [46, 'EOC'], [91, 'EDM'], [120, 'TEXT:Hi'], [127, 'TEXT: there']], 25], [[1840, 3640, ' thereHi']]), ('partial repair probe: text load target', [[[30, 'TEXT:Hi'], [31, 'TEXT: there'], [61, 'EDM'], [106, 'TEXT: there'], [121, 'ENM'], [136, 'TEXT:Hi'], [166, 'EOC']], 24], []), ('partial repair variant: text load target', [[[30, 'TEXT:Bye'], [59, 'EOC'], [66, 'TEXT:Bye'], [111, 'EOC']], 24], [[2458, 4625, 'Bye']]), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[0, 'EDM'], [15, 'TEXT:Bye']], 29], []), ('normal control', [[[3, 'EOC'], [48, 'ENM']], 30], []), ('normal control', [[[3, 'TEXT:Bye'], [48, 'TEXT:Hi']], 24], [])], [('regression: text load target', [[[3, 'EOC'], [3, 'TEXT: there'], [4, 'TEXT: there'], [34, 'EDM'], [64, 'EOC'], [71, 'EOC'], [78, 'TEXT: there'], [78, 'TEXT: there']], 30], [[2133, 2366, ' there there']]), ('regression variant: text load target', [[[0, 'TEXT: there'], [29, 'TEXT:Bye'], [44, 'EDM'], [73, 'EOC'], [118, 'EOC'], [163, 'TEXT: there'], [192, 'ENM']], 25], [[2920, 4720, ' thereBye']]), ('partial repair probe: text load target', [[[30, 'TEXT: there'], [30, 'EOC'], [59, 'ENM']], 30], []), ('partial repair variant: text load target', [[[0, 'TEXT: there'], [7, 'ENM'], [8, 'EOC'], [9, 'ENM'], [16, 'TEXT:Hi']], 30], []), ('boundary control', [[[0, 'EOC'], [5, 'EDM']], 30], []), ('normal control', [[[3, 'EOC'], [4, 'EOC'], [19, 'EOC'], [20, 'EOC'], [21, 'EOC'], [51, 'EDM'], [58, 'EDM'], [58, 'EOC']], 24], []), ('normal control', [[[0, 'TEXT:Bye'], [30, 'ENM'], [59, 'TEXT:Bye'], [104, 'ENM'], [119, 'ENM'], [148, 'TEXT:Bye'], [178, 'ENM']], 30], []), ('normal control', [[[3, 'EOC'], [48, 'EOC'], [55, 'TEXT: there']], 24], [])]]
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: text load target[[None, 1920, ' there there there']][[1920, 3120, ' there there there']]Failed
regression variant: text load target[[None, 4800, 'HiHi'], [4800, 6560, 'Hi'], [4800, 9520, 'Hi'], [9520, 10680, 'HiHi']][[4800, 6560, 'HiHi'], [9520, 10680, 'HiHi']]Failed
partial repair probe: text load target[[0, 2166, 'Bye'], [0, 3083, 'Bye']][]Failed
partial repair variant: text load target[[None, 1291, ' there']][]Failed
boundary control[][]Passed
normal control[][]Passed
normal control[][]Passed
normal control[][]Passed

SHA-256 / 71ef86d8d8e813d227b63774305307fb23e136270fa62c90579459664f626315

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

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 2026-09-29T14:49:33.471885+00:00.

Case digest / d60382b48bf2736a9f02e6cfad9009d406b331beb3e74947754f9b17271bb69e