{"abstract":"An all-zero PCM block advertises arbitrary maximum wasted precision instead of canonical zero shift.","category":"PCM sample encoding","checks":8,"contract":"Losslessly factor the largest capped common trailing-zero count from signed PCM samples; zero samples do not constrain the count and all-silence blocks canonically use zero.","contract_signature":"samples, maximum","evaluation_group":"s3-pcm-pcm-common-trailing-zero-shift","failed_approach":"Processing only silence blocks misses real common trailing zeros.","family":"s3-pcm-pcm-common-trailing-zero-shift-silence-block-canonical","id":"FA-50266","implementations":{"attempt":{"sha256":"73beb615640d42612d136a1d0ebdcac9111875e35252c1d103638c62829e47d3","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(samples, maximum):\n    shift=0\n    nonzero=[abs(x) for x in samples if x!=0]\n    if not nonzero:\n        while shift<maximum and all((x&((1<<(shift+1))-1))==0 for x in nonzero):\n            shift+=1\n    coarse=[x>>shift for x in samples]\n    return [shift,coarse]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([8, -12, 0], 5)), [2, [2, -3, 0]])\ncheck('oracle 2', solve(*([0, 0], 4)), [0, [0, 0]])\ncheck('oracle 3', solve(*([8, 6], 4)), [1, [4, 3]])\ncheck('oracle 4', solve(*([], 3)), [0, []])\ncheck('oracle 5', solve(*([-8, -4], 5)), [2, [-2, -1]])\ncheck('oracle 6', solve(*([16, 32], 2)), [2, [4, 8]])\ncheck('oracle 7', solve(*([3, -8], 4)), [0, [3, -8]])\nif N == 1: check('variant packet 1', solve(*[[8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0]])\nif N == 2: check('variant packet 2', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0]])\nif N == 3: check('variant packet 3', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0]])\nif N == 4: check('variant packet 4', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0]])\nif N == 5: check('variant packet 5', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0]])\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":"7b6d3974e073fa75b6d879c030f61285f83e02d6e409a579401466e44d2d02e5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(samples, maximum):\n    shift=0\n    nonzero=[abs(x) for x in samples if x!=0]\n    if samples:\n        while shift<maximum and all((x&((1<<(shift+1))-1))==0 for x in nonzero):\n            shift+=1\n    coarse=[x>>shift for x in samples]\n    return [shift,coarse]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([8, -12, 0], 5)), [2, [2, -3, 0]])\ncheck('oracle 2', solve(*([0, 0], 4)), [0, [0, 0]])\ncheck('oracle 3', solve(*([8, 6], 4)), [1, [4, 3]])\ncheck('oracle 4', solve(*([], 3)), [0, []])\ncheck('oracle 5', solve(*([-8, -4], 5)), [2, [-2, -1]])\ncheck('oracle 6', solve(*([16, 32], 2)), [2, [4, 8]])\ncheck('oracle 7', solve(*([3, -8], 4)), [0, [3, -8]])\nif N == 1: check('variant packet 1', solve(*[[8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0]])\nif N == 2: check('variant packet 2', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0]])\nif N == 3: check('variant packet 3', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0]])\nif N == 4: check('variant packet 4', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0]])\nif N == 5: check('variant packet 5', solve(*[[8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0, 8, -12, 0], 5]), [2, [2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0, 2, -3, 0]])\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":"Stipulated finite model; no claim of hardware timing or full file-format conformance. 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":"s3-pcm-pcm-common-trailing-zero-shift-silence-block-canonical","generated_at":"2026-09-29T14:45:07.622697+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Offline PCM interchange uses these exact bounded packet and sample representation decisions.","root_cause":"An all-zero PCM block advertises arbitrary maximum wasted precision instead of canonical zero shift.","sha256":"1b4c9a3e7e21c60d255434629f8ee0f5e28d3942c4cc6a761f3f020d516ff49e","title":"Pcm common trailing zero shift: silence block canonical · 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":36.69,"exit_code":1,"observations":[{"actual":[0,[8,-12,0]],"check":"oracle 1","expected":[2,[2,-3,0]],"passed":false},{"actual":[4,[0,0]],"check":"oracle 2","expected":[0,[0,0]],"passed":false},{"actual":[0,[8,6]],"check":"oracle 3","expected":[1,[4,3]],"passed":false},{"actual":[3,[]],"check":"oracle 4","expected":[0,[]],"passed":false},{"actual":[0,[-8,-4]],"check":"oracle 5","expected":[2,[-2,-1]],"passed":false},{"actual":[0,[16,32]],"check":"oracle 6","expected":[2,[4,8]],"passed":false},{"actual":[0,[3,-8]],"check":"oracle 7","expected":[0,[3,-8]],"passed":true},{"actual":[0,[8,-12,0,8,-12,0]],"check":"variant packet 1","expected":[2,[2,-3,0,2,-3,0]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [0, [8, -12, 0]], \"expected\": [2, [2, -3, 0]], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [4, [0, 0]], \"expected\": [0, [0, 0]], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [0, [8, 6]], \"expected\": [1, [4, 3]], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [3, []], \"expected\": [0, []], \"passed\": false}, {\"check\": \"oracle 5\", \"actual\": [0, [-8, -4]], \"expected\": [2, [-2, -1]], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [0, [16, 32]], \"expected\": [2, [4, 8]], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [0, [3, -8]], \"expected\": [0, [3, -8]], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [0, [8, -12, 0, 8, -12, 0]], \"expected\": [2, [2, -3, 0, 2, -3, 0]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":38.248,"exit_code":1,"observations":[{"actual":[2,[2,-3,0]],"check":"oracle 1","expected":[2,[2,-3,0]],"passed":true},{"actual":[4,[0,0]],"check":"oracle 2","expected":[0,[0,0]],"passed":false},{"actual":[1,[4,3]],"check":"oracle 3","expected":[1,[4,3]],"passed":true},{"actual":[0,[]],"check":"oracle 4","expected":[0,[]],"passed":true},{"actual":[2,[-2,-1]],"check":"oracle 5","expected":[2,[-2,-1]],"passed":true},{"actual":[2,[4,8]],"check":"oracle 6","expected":[2,[4,8]],"passed":true},{"actual":[0,[3,-8]],"check":"oracle 7","expected":[0,[3,-8]],"passed":true},{"actual":[2,[2,-3,0,2,-3,0]],"check":"variant packet 1","expected":[2,[2,-3,0,2,-3,0]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [2, [2, -3, 0]], \"expected\": [2, [2, -3, 0]], \"passed\": true}, {\"check\": \"oracle 2\", \"actual\": [4, [0, 0]], \"expected\": [0, [0, 0]], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [1, [4, 3]], \"expected\": [1, [4, 3]], \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": [0, []], \"expected\": [0, []], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [2, [-2, -1]], \"expected\": [2, [-2, -1]], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [2, [4, 8]], \"expected\": [2, [4, 8]], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [0, [3, -8]], \"expected\": [0, [3, -8]], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [2, [2, -3, 0, 2, -3, 0]], \"expected\": [2, [2, -3, 0, 2, -3, 0]], \"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."}}