{"abstract":"About half of all sub-frame tick positions are reported one microsecond later than the stipulated floored time.","category":"MIDI event timing","checks":8,"contract":"Input [division_high_byte, ticks_per_frame, ticks]. The high byte is a negative frame-rate code in two's complement: 24, 25, 29 (meaning 30000/1001 frames per second) or 30. Microseconds = ticks * 1000000 / (rate * ticks_per_frame), floored once. Invalid codes, non-positive ticks per frame or negative ticks return None.","contract_signature":"x","evaluation_group":"w2-midi-event-timing-smpte-division-time","failed_approach":"Dropping the parentheses multiplies by ticks per frame instead of dividing by it.","family":"w2-midi-event-timing-smpte-division-time-microsecond-rounding","id":"FA-81516","implementations":{"attempt":{"sha256":"d1c4b6875dcd3e27f9fd1e190d82a47fffbf7e4ef41016936817d95290a183ae","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(x):\n    if not isinstance(x, list) or len(x) != 3:\n        return None\n    hi, tpf, ticks = x\n    code = 256 - hi\n    rates = {24: Fraction(24), 25: Fraction(25), 29: Fraction(30000, 1001), 30: Fraction(30)}\n    if code not in rates or tpf <= 0 or ticks < 0:\n        return None\n    return int(Fraction(ticks * 1000000) / rates[code] * tpf)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([232, 40, 40], 41666), ([227, 80, 2400], 1001000), ([232, 1, 1], 41666), ([227, 1, 29], 967633), ([233, 40, 40], None), ([228, 40, 40], None), ([232, 0, 10], None), ([232, 40, -1], None)], [([232, 40, 40], 41666), ([231, 40, 1000], 1000000), ([227, 80, 80], 33366), ([227, 80, 2400], 1001000), ([227, 4, 107892], 899999100), ([232, 0, 10], None), ([232, 40, -1], None), ([227, 80, 0], 0)], [([232, 40, 40], 41666), ([231, 40, 1000], 1000000), ([227, 80, 80], 33366), ([227, 80, 2400], 1001000), ([227, 4, 107892], 899999100), ([226, 100, 3000], 1000000), ([226, 100, 7], 2333), ([232, 1, 1], 41666)], [([232, 40, 40], 41666), ([227, 80, 2400], 1001000), ([227, 4, 107892], 899999100), ([226, 100, 3000], 1000000), ([226, 100, 7], 2333), ([232, 1, 1], 41666), ([231, 4, 3], 30000), ([226, 3, 1000001], 11111122222)], [([232, 40, 40], 41666), ([227, 80, 80], 33366), ([227, 4, 107892], 899999100), ([226, 100, 7], 2333), ([232, 1, 1], 41666), ([231, 4, 3], 30000), ([226, 3, 1000001], 11111122222), ([227, 100, 300000], 100100000)]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"oracle %d\" % i, 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":"34169f55bea837f80cb8beb543990988e07a3a8f9083f3453f8644fd674e282b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(x):\n    if not isinstance(x, list) or len(x) != 3:\n        return None\n    hi, tpf, ticks = x\n    code = 256 - hi\n    rates = {24: Fraction(24), 25: Fraction(25), 29: Fraction(30000, 1001), 30: Fraction(30)}\n    if code not in rates or tpf <= 0 or ticks < 0:\n        return None\n    return round(Fraction(ticks * 1000000) / (rates[code] * tpf))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([232, 40, 40], 41666), ([227, 80, 2400], 1001000), ([232, 1, 1], 41666), ([227, 1, 29], 967633), ([233, 40, 40], None), ([228, 40, 40], None), ([232, 0, 10], None), ([232, 40, -1], None)], [([232, 40, 40], 41666), ([231, 40, 1000], 1000000), ([227, 80, 80], 33366), ([227, 80, 2400], 1001000), ([227, 4, 107892], 899999100), ([232, 0, 10], None), ([232, 40, -1], None), ([227, 80, 0], 0)], [([232, 40, 40], 41666), ([231, 40, 1000], 1000000), ([227, 80, 80], 33366), ([227, 80, 2400], 1001000), ([227, 4, 107892], 899999100), ([226, 100, 3000], 1000000), ([226, 100, 7], 2333), ([232, 1, 1], 41666)], [([232, 40, 40], 41666), ([227, 80, 2400], 1001000), ([227, 4, 107892], 899999100), ([226, 100, 3000], 1000000), ([226, 100, 7], 2333), ([232, 1, 1], 41666), ([231, 4, 3], 30000), ([226, 3, 1000001], 11111122222)], [([232, 40, 40], 41666), ([227, 80, 80], 33366), ([227, 4, 107892], 899999100), ([226, 100, 7], 2333), ([232, 1, 1], 41666), ([231, 4, 3], 30000), ([226, 3, 1000001], 11111122222), ([227, 100, 300000], 100100000)]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"oracle %d\" % i, 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 is not a complete Standard MIDI File or MIDI 1.0/2.0 implementation. 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-midi-event-timing-smpte-division-time-microsecond-rounding","generated_at":"2026-09-29T14:50:03.782973+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"MIDI sequencers, file readers and synth drivers depend on exact event ordering and tick/time arithmetic.","root_cause":"The exact quotient is rounded to nearest instead of floored.","sha256":"ca1df9163a957a216e63df9c3f568fd0f3a4403078c8893c405440047a71f672","title":"SMPTE time-division ticks to microseconds: event times rounded to nearest microsecond · 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":42.897,"exit_code":1,"observations":[{"actual":66666666,"check":"oracle 0","expected":41666,"passed":false},{"actual":6406400000,"check":"oracle 1","expected":1001000,"passed":false},{"actual":41666,"check":"oracle 2","expected":41666,"passed":true},{"actual":967633,"check":"oracle 3","expected":967633,"passed":true},{"actual":null,"check":"oracle 4","expected":null,"passed":true},{"actual":null,"check":"oracle 5","expected":null,"passed":true},{"actual":null,"check":"oracle 6","expected":null,"passed":true},{"actual":null,"check":"oracle 7","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 0\", \"actual\": 66666666, \"expected\": 41666, \"passed\": false}, {\"check\": \"oracle 1\", \"actual\": 6406400000, \"expected\": 1001000, \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": 41666, \"expected\": 41666, \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": 967633, \"expected\": 967633, \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": null, \"expected\": null, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.903,"exit_code":1,"observations":[{"actual":41667,"check":"oracle 0","expected":41666,"passed":false},{"actual":1001000,"check":"oracle 1","expected":1001000,"passed":true},{"actual":41667,"check":"oracle 2","expected":41666,"passed":false},{"actual":967633,"check":"oracle 3","expected":967633,"passed":true},{"actual":null,"check":"oracle 4","expected":null,"passed":true},{"actual":null,"check":"oracle 5","expected":null,"passed":true},{"actual":null,"check":"oracle 6","expected":null,"passed":true},{"actual":null,"check":"oracle 7","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 0\", \"actual\": 41667, \"expected\": 41666, \"passed\": false}, {\"check\": \"oracle 1\", \"actual\": 1001000, \"expected\": 1001000, \"passed\": true}, {\"check\": \"oracle 2\", \"actual\": 41667, \"expected\": 41666, \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": 967633, \"expected\": 967633, \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": null, \"expected\": null, \"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."}}