{"abstract":"Files labelled 23.976 accumulate a small drift against the real 24000/1001 video.","category":"Subtitle cue timing","checks":9,"contract":"Cue times authored against a src frame rate are rescaled for playback at dst by t*src/dst, rounded half up to integer ms. Rates are \"N\", \"N/D\", or the aliases \"23.976\"/\"29.97\" meaning (N+1)*1000/1001. The end is rounded independently; an end that does not exceed the start becomes start+1.","contract_signature":"cues, src, dst","evaluation_group":"w2-subtitle-cue-timing-frame-rate-retime","failed_approach":"Rounding the alias up to 24 discards the 1000/1001 pull-down factor completely.","family":"w2-subtitle-cue-timing-frame-rate-retime-ntsc-alias-rate","id":"FA-77926","implementations":{"attempt":{"sha256":"2791fbb2fb08f1c396486afa8f3e6628f45b5154f79c493854f8d70c9f35097b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(cues, src, dst):\n    def rate(r):\n        if '/' in r:\n            a,b=r.split('/')\n            return Fraction(int(a),int(b))\n        if '.' in r:\n            return Fraction(int(float(r)+0.5))\n        return Fraction(int(r))\n    k=rate(src)/rate(dst)\n    out=[]\n    for start,end in cues:\n        rs=math.floor(start*k+Fraction(1,2))\n        re_=math.floor(end*k+Fraction(1,2))\n        if re_<=rs:\n            re_=rs+1\n        out.append([rs,re_])\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('regression: ntsc alias rate', [[[540231, 541231], [0, 3]], '50', '29.97'], [[901285, 902954], [0, 5]]), ('regression variant: ntsc alias rate', [[[0, 1], [489701, 489704], [1001, 1002], [1, 1001]], '29.97', '30'], [[0, 1], [489212, 489215], [1000, 1001], [1, 1000]]), ('partial repair probe: ntsc alias rate', [[[269050, 271051]], '30000/1001', '23.976'], [[336313, 338814]]), ('partial repair variant: ntsc alias rate', [[[999, 1002]], '50', '29.97'], [[1667, 1672]]), ('boundary control', [[[1000, 2000]], '25', '50'], [[500, 1000]]), ('boundary control', [[[1, 2], [3, 4]], '23.976', '25'], [[1, 2], [3, 4]]), ('normal control', [[[1001, 3003]], '24000/1001', '24'], [[1000, 3000]]), ('normal control', [[[268354, 268356], [12345, 14346], [0, 42]], '60', '25'], [[644050, 644054], [29628, 34430], [0, 101]]), ('normal control', [[[1, 4], [7, 9], [12345, 14346], [1001, 1002]], '24000/1001', '12'], [[2, 8], [14, 18], [24665, 28663], [2000, 2002]])], [('regression: ntsc alias rate', [[[559526, 560526], [1, 1001], [3, 2004]], '29.97', '60'], [[279484, 279983], [0, 500], [1, 1001]]), ('regression variant: ntsc alias rate', [[[368223, 369223], [999, 1001], [1001, 3733]], '12', '29.97'], [[147436, 147837], [400, 401], [401, 1495]]), ('partial repair probe: ntsc alias rate', [[[269050, 271051]], '30000/1001', '23.976'], [[336313, 338814]]), ('partial repair variant: ntsc alias rate', [[[3, 6]], '29.97', '24'], [[4, 7]]), ('boundary control', [[[1001, 3003]], '24000/1001', '24'], [[1000, 3000]]), ('boundary control', [[[1000, 2000]], '25', '50'], [[500, 1000]]), ('normal control', [[[1, 4]], '15', '15'], [[1, 4]]), ('normal control', [[[1001, 1003]], '60', '15'], [[4004, 4012]]), ('normal control', [[[7, 9], [3, 6], [0, 3], [1, 4]], '24', '23.976'], [[7, 9], [3, 6], [0, 3], [1, 4]])], [('regression: ntsc alias rate', [[[704417, 706418], [7, 9]], '29.97', '24'], [[879642, 882140], [9, 11]]), ('regression variant: ntsc alias rate', [[[639258, 643831], [3, 4773], [741030, 741031]], '29.97', '50'], [[383172, 385913], [2, 2861], [444174, 444175]]), ('partial repair probe: ntsc alias rate', [[[999, 3000], [3, 1003], [999, 2960]], '23.976', '60'], [[399, 1199], [1, 401], [399, 1183]]), ('partial repair variant: ntsc alias rate', [[[999, 1999]], '23.976', '50'], [[479, 959]]), ('boundary control', [[[5, 6]], '24', '25'], [[5, 6]]), ('boundary control', [[[1001, 3003]], '24000/1001', '24'], [[1000, 3000]]), ('normal control', [[[1, 4]], '23.976', '15'], [[2, 6]]), ('normal control', [[[3, 1003], [999, 1000], [3, 5]], '50', '30'], [[5, 1672], [1665, 1667], [5, 8]]), ('normal control', [[[7, 2008], [1001, 3002]], '50', '12'], [[29, 8367], [4171, 12508]])], [('regression: ntsc alias rate', [[[256578, 256580], [1, 1001], [3, 6], [1, 1315]], '23.976', '15'], [[410115, 410118], [2, 1600], [5, 10], [2, 2102]]), ('regression variant: ntsc alias rate', [[[7, 8], [215573, 215574], [999, 3000]], '29.97', '30'], [[7, 8], [215358, 215359], [998, 2997]]), ('partial repair probe: ntsc alias rate', [[[999, 2714], [12345, 13345], [1, 2002]], '29.97', '30000/1001'], [[999, 2714], [12345, 13345], [1, 2002]]), ('partial repair variant: ntsc alias rate', [[[3, 509], [1, 4], [1, 2847]], '24000/1001', '29.97'], [[2, 407], [1, 3], [1, 2278]]), ('boundary control', [[[1, 2], [3, 4]], '23.976', '25'], [[1, 2], [3, 4]]), ('boundary control', [[[5, 6]], '24', '25'], [[5, 6]]), ('normal control', [[[999, 1001], [1001, 1003], [54677, 54680], [7, 2008]], '48', '25'], [[1918, 1922], [1922, 1926], [104980, 104986], [13, 3855]]), ('normal control', [[[1001, 1004], [7, 9], [999, 1001]], '30', '25'], [[1201, 1205], [8, 11], [1199, 1201]]), ('normal control', [[[821125, 821127], [0, 1]], '30', '30'], [[821125, 821127], [0, 1]])], [('regression: ntsc alias rate', [[[1, 2], [999, 1999], [166350, 167350], [1, 4224]], '50', '29.97'], [[2, 3], [1667, 3335], [277527, 279196], [2, 7047]]), ('regression variant: ntsc alias rate', [[[557345, 559346], [999, 1000]], '23.976', '30'], [[445431, 447030], [798, 799]]), ('partial repair probe: ntsc alias rate', [[[209282, 209284], [999, 1000], [1, 1001]], '12', '29.97'], [[83797, 83798], [400, 401], [0, 401]]), ('partial repair variant: ntsc alias rate', [[[3, 4], [1, 4181], [999, 1001]], '30', '23.976'], [[4, 5], [1, 5231], [1250, 1253]]), ('boundary control', [[[1000, 2000]], '25', '50'], [[500, 1000]]), ('boundary control', [[[1, 2], [3, 4]], '23.976', '25'], [[1, 2], [3, 4]]), ('normal control', [[[3, 2004], [3, 1003], [0, 3]], '30000/1001', '24000/1001'], [[4, 2505], [4, 1254], [0, 4]]), ('normal control', [[[1, 2], [7, 2008], [1001, 1002]], '50', '25'], [[2, 4], [14, 4016], [2002, 2004]]), ('normal control', [[[1, 4]], '24000/1001', '50'], [[0, 2]])]]\nfor label, args, expected in fixtures[N-1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"8e2062c3d10e5ef411d0a92f96f0fec1b37c270e752292c4dfd902f3f3a5ffb5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(cues, src, dst):\n    def rate(r):\n        if '/' in r:\n            a,b=r.split('/')\n            return Fraction(int(a),int(b))\n        if '.' in r:\n            return Fraction(r)\n        return Fraction(int(r))\n    k=rate(src)/rate(dst)\n    out=[]\n    for start,end in cues:\n        rs=math.floor(start*k+Fraction(1,2))\n        re_=math.floor(end*k+Fraction(1,2))\n        if re_<=rs:\n            re_=rs+1\n        out.append([rs,re_])\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('regression: ntsc alias rate', [[[540231, 541231], [0, 3]], '50', '29.97'], [[901285, 902954], [0, 5]]), ('regression variant: ntsc alias rate', [[[0, 1], [489701, 489704], [1001, 1002], [1, 1001]], '29.97', '30'], [[0, 1], [489212, 489215], [1000, 1001], [1, 1000]]), ('partial repair probe: ntsc alias rate', [[[269050, 271051]], '30000/1001', '23.976'], [[336313, 338814]]), ('partial repair variant: ntsc alias rate', [[[999, 1002]], '50', '29.97'], [[1667, 1672]]), ('boundary control', [[[1000, 2000]], '25', '50'], [[500, 1000]]), ('boundary control', [[[1, 2], [3, 4]], '23.976', '25'], [[1, 2], [3, 4]]), ('normal control', [[[1001, 3003]], '24000/1001', '24'], [[1000, 3000]]), ('normal control', [[[268354, 268356], [12345, 14346], [0, 42]], '60', '25'], [[644050, 644054], [29628, 34430], [0, 101]]), ('normal control', [[[1, 4], [7, 9], [12345, 14346], [1001, 1002]], '24000/1001', '12'], [[2, 8], [14, 18], [24665, 28663], [2000, 2002]])], [('regression: ntsc alias rate', [[[559526, 560526], [1, 1001], [3, 2004]], '29.97', '60'], [[279484, 279983], [0, 500], [1, 1001]]), ('regression variant: ntsc alias rate', [[[368223, 369223], [999, 1001], [1001, 3733]], '12', '29.97'], [[147436, 147837], [400, 401], [401, 1495]]), ('partial repair probe: ntsc alias rate', [[[269050, 271051]], '30000/1001', '23.976'], [[336313, 338814]]), ('partial repair variant: ntsc alias rate', [[[3, 6]], '29.97', '24'], [[4, 7]]), ('boundary control', [[[1001, 3003]], '24000/1001', '24'], [[1000, 3000]]), ('boundary control', [[[1000, 2000]], '25', '50'], [[500, 1000]]), ('normal control', [[[1, 4]], '15', '15'], [[1, 4]]), ('normal control', [[[1001, 1003]], '60', '15'], [[4004, 4012]]), ('normal control', [[[7, 9], [3, 6], [0, 3], [1, 4]], '24', '23.976'], [[7, 9], [3, 6], [0, 3], [1, 4]])], [('regression: ntsc alias rate', [[[704417, 706418], [7, 9]], '29.97', '24'], [[879642, 882140], [9, 11]]), ('regression variant: ntsc alias rate', [[[639258, 643831], [3, 4773], [741030, 741031]], '29.97', '50'], [[383172, 385913], [2, 2861], [444174, 444175]]), ('partial repair probe: ntsc alias rate', [[[999, 3000], [3, 1003], [999, 2960]], '23.976', '60'], [[399, 1199], [1, 401], [399, 1183]]), ('partial repair variant: ntsc alias rate', [[[999, 1999]], '23.976', '50'], [[479, 959]]), ('boundary control', [[[5, 6]], '24', '25'], [[5, 6]]), ('boundary control', [[[1001, 3003]], '24000/1001', '24'], [[1000, 3000]]), ('normal control', [[[1, 4]], '23.976', '15'], [[2, 6]]), ('normal control', [[[3, 1003], [999, 1000], [3, 5]], '50', '30'], [[5, 1672], [1665, 1667], [5, 8]]), ('normal control', [[[7, 2008], [1001, 3002]], '50', '12'], [[29, 8367], [4171, 12508]])], [('regression: ntsc alias rate', [[[256578, 256580], [1, 1001], [3, 6], [1, 1315]], '23.976', '15'], [[410115, 410118], [2, 1600], [5, 10], [2, 2102]]), ('regression variant: ntsc alias rate', [[[7, 8], [215573, 215574], [999, 3000]], '29.97', '30'], [[7, 8], [215358, 215359], [998, 2997]]), ('partial repair probe: ntsc alias rate', [[[999, 2714], [12345, 13345], [1, 2002]], '29.97', '30000/1001'], [[999, 2714], [12345, 13345], [1, 2002]]), ('partial repair variant: ntsc alias rate', [[[3, 509], [1, 4], [1, 2847]], '24000/1001', '29.97'], [[2, 407], [1, 3], [1, 2278]]), ('boundary control', [[[1, 2], [3, 4]], '23.976', '25'], [[1, 2], [3, 4]]), ('boundary control', [[[5, 6]], '24', '25'], [[5, 6]]), ('normal control', [[[999, 1001], [1001, 1003], [54677, 54680], [7, 2008]], '48', '25'], [[1918, 1922], [1922, 1926], [104980, 104986], [13, 3855]]), ('normal control', [[[1001, 1004], [7, 9], [999, 1001]], '30', '25'], [[1201, 1205], [8, 11], [1199, 1201]]), ('normal control', [[[821125, 821127], [0, 1]], '30', '30'], [[821125, 821127], [0, 1]])], [('regression: ntsc alias rate', [[[1, 2], [999, 1999], [166350, 167350], [1, 4224]], '50', '29.97'], [[2, 3], [1667, 3335], [277527, 279196], [2, 7047]]), ('regression variant: ntsc alias rate', [[[557345, 559346], [999, 1000]], '23.976', '30'], [[445431, 447030], [798, 799]]), ('partial repair probe: ntsc alias rate', [[[209282, 209284], [999, 1000], [1, 1001]], '12', '29.97'], [[83797, 83798], [400, 401], [0, 401]]), ('partial repair variant: ntsc alias rate', [[[3, 4], [1, 4181], [999, 1001]], '30', '23.976'], [[4, 5], [1, 5231], [1250, 1253]]), ('boundary control', [[[1000, 2000]], '25', '50'], [[500, 1000]]), ('boundary control', [[[1, 2], [3, 4]], '23.976', '25'], [[1, 2], [3, 4]]), ('normal control', [[[3, 2004], [3, 1003], [0, 3]], '30000/1001', '24000/1001'], [[4, 2505], [4, 1254], [0, 4]]), ('normal control', [[[1, 2], [7, 2008], [1001, 1002]], '50', '25'], [[2, 4], [14, 4016], [2002, 2004]]), ('normal control', [[[1, 4]], '24000/1001', '50'], [[0, 2]])]]\nfor label, args, expected in fixtures[N-1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-subtitle-cue-timing-frame-rate-retime-ntsc-alias-rate","generated_at":"2026-09-29T14:49:30.594133+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Subtitle timing defects shift, hide or overlap captions that viewers depend on for comprehension and accessibility.","root_cause":"The decimal alias is parsed literally as 23.976 instead of the exact 24000/1001 rate.","sha256":"8552ae5f2e9593d6522ad3efb8cdb948936b98fa49fa50a76dbb4b0aed81799f","title":"Subtitle frame-rate retiming: ntsc alias rate · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":49.615,"exit_code":1,"observations":[{"actual":[[900385,902052],[0,5]],"check":"regression: ntsc alias rate","expected":[[901285,902954],[0,5]],"passed":false},{"actual":[[0,1],[489701,489704],[1001,1002],[1,1001]],"check":"regression variant: ntsc alias rate","expected":[[0,1],[489212,489215],[1000,1001],[1,1000]],"passed":false},{"actual":[[335977,338475]],"check":"partial repair probe: ntsc alias rate","expected":[[336313,338814]],"passed":false},{"actual":[[1665,1670]],"check":"partial repair variant: ntsc alias rate","expected":[[1667,1672]],"passed":false},{"actual":[[500,1000]],"check":"boundary control","expected":[[500,1000]],"passed":true},{"actual":[[1,2],[3,4]],"check":"boundary control","expected":[[1,2],[3,4]],"passed":true},{"actual":[[1000,3000]],"check":"normal control","expected":[[1000,3000]],"passed":true},{"actual":[[644050,644054],[29628,34430],[0,101]],"check":"normal control","expected":[[644050,644054],[29628,34430],[0,101]],"passed":true},{"actual":[[2,8],[14,18],[24665,28663],[2000,2002]],"check":"normal control","expected":[[2,8],[14,18],[24665,28663],[2000,2002]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression: ntsc alias rate\", \"actual\": [[900385, 902052], [0, 5]], \"expected\": [[901285, 902954], [0, 5]], \"passed\": false}, {\"check\": \"regression variant: ntsc alias rate\", \"actual\": [[0, 1], [489701, 489704], [1001, 1002], [1, 1001]], \"expected\": [[0, 1], [489212, 489215], [1000, 1001], [1, 1000]], \"passed\": false}, {\"check\": \"partial repair probe: ntsc alias rate\", \"actual\": [[335977, 338475]], \"expected\": [[336313, 338814]], \"passed\": false}, {\"check\": \"partial repair variant: ntsc alias rate\", \"actual\": [[1665, 1670]], \"expected\": [[1667, 1672]], \"passed\": false}, {\"check\": \"boundary control\", \"actual\": [[500, 1000]], \"expected\": [[500, 1000]], \"passed\": true}, {\"check\": \"boundary control\", \"actual\": [[1, 2], [3, 4]], \"expected\": [[1, 2], [3, 4]], \"passed\": true}, {\"check\": \"normal control\", \"actual\": [[1000, 3000]], \"expected\": [[1000, 3000]], \"passed\": true}, {\"check\": \"normal control\", \"actual\": [[644050, 644054], [29628, 34430], [0, 101]], \"expected\": [[644050, 644054], [29628, 34430], [0, 101]], \"passed\": true}, {\"check\": \"normal control\", \"actual\": [[2, 8], [14, 18], [24665, 28663], [2000, 2002]], \"expected\": [[2, 8], [14, 18], [24665, 28663], [2000, 2002]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":45.566,"exit_code":1,"observations":[{"actual":[[901286,902955],[0,5]],"check":"regression: ntsc alias rate","expected":[[901285,902954],[0,5]],"passed":false},{"actual":[[0,1],[489211,489214],[1000,1001],[1,1000]],"check":"regression variant: ntsc alias rate","expected":[[0,1],[489212,489215],[1000,1001],[1,1000]],"passed":false},{"actual":[[336313,338814]],"check":"partial repair probe: ntsc alias rate","expected":[[336313,338814]],"passed":true},{"actual":[[1667,1672]],"check":"partial repair variant: ntsc alias rate","expected":[[1667,1672]],"passed":true},{"actual":[[500,1000]],"check":"boundary control","expected":[[500,1000]],"passed":true},{"actual":[[1,2],[3,4]],"check":"boundary control","expected":[[1,2],[3,4]],"passed":true},{"actual":[[1000,3000]],"check":"normal control","expected":[[1000,3000]],"passed":true},{"actual":[[644050,644054],[29628,34430],[0,101]],"check":"normal control","expected":[[644050,644054],[29628,34430],[0,101]],"passed":true},{"actual":[[2,8],[14,18],[24665,28663],[2000,2002]],"check":"normal control","expected":[[2,8],[14,18],[24665,28663],[2000,2002]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression: ntsc alias rate\", \"actual\": [[901286, 902955], [0, 5]], \"expected\": [[901285, 902954], [0, 5]], \"passed\": false}, {\"check\": \"regression variant: ntsc alias rate\", \"actual\": [[0, 1], [489211, 489214], [1000, 1001], [1, 1000]], \"expected\": [[0, 1], [489212, 489215], [1000, 1001], [1, 1000]], \"passed\": false}, {\"check\": \"partial repair probe: ntsc alias rate\", \"actual\": [[336313, 338814]], \"expected\": [[336313, 338814]], \"passed\": true}, {\"check\": \"partial repair variant: ntsc alias rate\", \"actual\": [[1667, 1672]], \"expected\": [[1667, 1672]], \"passed\": true}, {\"check\": \"boundary control\", \"actual\": [[500, 1000]], \"expected\": [[500, 1000]], \"passed\": true}, {\"check\": \"boundary control\", \"actual\": [[1, 2], [3, 4]], \"expected\": [[1, 2], [3, 4]], \"passed\": true}, {\"check\": \"normal control\", \"actual\": [[1000, 3000]], \"expected\": [[1000, 3000]], \"passed\": true}, {\"check\": \"normal control\", \"actual\": [[644050, 644054], [29628, 34430], [0, 101]], \"expected\": [[644050, 644054], [29628, 34430], [0, 101]], \"passed\": true}, {\"check\": \"normal control\", \"actual\": [[2, 8], [14, 18], [24665, 28663], [2000, 2002]], \"expected\": [[2, 8], [14, 18], [24665, 28663], [2000, 2002]], \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}