{"abstract":"A-law polarity uses the opposite convention from the decoder.","category":"PCM sample encoding","checks":8,"contract":"Decode eight-bit A-law codes into signed integer PCM using alternating-bit mask85, midpoint reconstruction and explicit segment rules.","evaluation_group":"s3-pcm-alaw-expansion","failed_approach":"Testing a wire mantissa bit makes polarity depend on magnitude.","family":"s3-pcm-alaw-expansion-polarity-bit","id":"FA-49011","implementations":{"attempt":{"sha256":"f26fab8bc6d9254d7493de1ddf91e0f265cfd82149c6d30670032fb6488521af","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(codes):\n    out=[]\n    for raw in codes:\n        code=raw^85\n        segment=(code>>4)&7\n        mantissa=code&15\n        amplitude=(mantissa<<4)+8\n        if segment:\n            amplitude+=256\n        if segment>1:\n            amplitude<<=segment-1\n        out.append(amplitude if raw&1 else -amplitude)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([213, 85, 212, 84],)), [8, -8, 24, -24])\ncheck('oracle 2', solve(*([197, 69, 245, 117],)), [264, -264, 528, -528])\ncheck('oracle 3', solve(*([165, 37, 181, 53],)), [16896, -16896, 8448, -8448])\ncheck('oracle 4', solve(*([0, 128, 255],)), [-5504, 5504, 848])\ncheck('oracle 5', solve(*([],)), [])\ncheck('oracle 6', solve(*([214, 86, 196, 68],)), [56, -56, 280, -280])\ncheck('oracle 7', solve(*([149, 21, 133, 5],)), [2112, -2112, 4224, -4224])\nif N == 1: check('variant packet 1', solve(*[[213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24])\nif N == 2: check('variant packet 2', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 3: check('variant packet 3', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 4: check('variant packet 4', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 5: check('variant packet 5', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\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":"f6d8cab891597a0a100498b1dfbaea43aae9384a5cc7f3bcf980347a60e37ae5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(codes):\n    out=[]\n    for raw in codes:\n        code=raw^85\n        segment=(code>>4)&7\n        mantissa=code&15\n        amplitude=(mantissa<<4)+8\n        if segment:\n            amplitude+=256\n        if segment>1:\n            amplitude<<=segment-1\n        out.append(-amplitude if code&128 else amplitude)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([213, 85, 212, 84],)), [8, -8, 24, -24])\ncheck('oracle 2', solve(*([197, 69, 245, 117],)), [264, -264, 528, -528])\ncheck('oracle 3', solve(*([165, 37, 181, 53],)), [16896, -16896, 8448, -8448])\ncheck('oracle 4', solve(*([0, 128, 255],)), [-5504, 5504, 848])\ncheck('oracle 5', solve(*([],)), [])\ncheck('oracle 6', solve(*([214, 86, 196, 68],)), [56, -56, 280, -280])\ncheck('oracle 7', solve(*([149, 21, 133, 5],)), [2112, -2112, 4224, -4224])\nif N == 1: check('variant packet 1', solve(*[[213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24])\nif N == 2: check('variant packet 2', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 3: check('variant packet 3', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 4: check('variant packet 4', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 5: check('variant packet 5', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\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"},"fixed":{"sha256":"86375ee9ce48759ec2ddcfd7d48f2426685fdacd10c9765d2fc3ad0ce12d7296","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(codes):\n    out=[]\n    for raw in codes:\n        code=raw^85\n        segment=(code>>4)&7\n        mantissa=code&15\n        amplitude=(mantissa<<4)+8\n        if segment:\n            amplitude+=256\n        if segment>1:\n            amplitude<<=segment-1\n        out.append(amplitude if code&128 else -amplitude)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([213, 85, 212, 84],)), [8, -8, 24, -24])\ncheck('oracle 2', solve(*([197, 69, 245, 117],)), [264, -264, 528, -528])\ncheck('oracle 3', solve(*([165, 37, 181, 53],)), [16896, -16896, 8448, -8448])\ncheck('oracle 4', solve(*([0, 128, 255],)), [-5504, 5504, 848])\ncheck('oracle 5', solve(*([],)), [])\ncheck('oracle 6', solve(*([214, 86, 196, 68],)), [56, -56, 280, -280])\ncheck('oracle 7', solve(*([149, 21, 133, 5],)), [2112, -2112, 4224, -4224])\nif N == 1: check('variant packet 1', solve(*[[213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24])\nif N == 2: check('variant packet 2', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 3: check('variant packet 3', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 4: check('variant packet 4', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\nif N == 5: check('variant packet 5', solve(*[[213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84, 213, 85, 212, 84]]), [8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24, 8, -8, 24, -24])\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-alaw-expansion-polarity-bit","generated_at":"2026-09-29T14:44:55.955821+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.","repair":"Use the stated conversion contract at polarity bit.","root_cause":"A-law polarity uses the opposite convention from the decoder.","sha256":"b991c1da01286cc6078f02e6d86a4ec809dd07f1bd0907dcb140f79aa352cb83","title":"Alaw expansion: polarity bit · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":40.251,"exit_code":1,"observations":[{"actual":[8,8,-24,-24],"check":"oracle 1","expected":[8,-8,24,-24],"passed":false},{"actual":[264,264,528,528],"check":"oracle 2","expected":[264,-264,528,-528],"passed":false},{"actual":[16896,16896,8448,8448],"check":"oracle 3","expected":[16896,-16896,8448,-8448],"passed":false},{"actual":[-5504,-5504,848],"check":"oracle 4","expected":[-5504,5504,848],"passed":false},{"actual":[],"check":"oracle 5","expected":[],"passed":true},{"actual":[-56,-56,-280,-280],"check":"oracle 6","expected":[56,-56,280,-280],"passed":false},{"actual":[2112,2112,4224,4224],"check":"oracle 7","expected":[2112,-2112,4224,-4224],"passed":false},{"actual":[8,8,-24,-24,8,8,-24,-24],"check":"variant packet 1","expected":[8,-8,24,-24,8,-8,24,-24],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [8, 8, -24, -24], \"expected\": [8, -8, 24, -24], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [264, 264, 528, 528], \"expected\": [264, -264, 528, -528], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [16896, 16896, 8448, 8448], \"expected\": [16896, -16896, 8448, -8448], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [-5504, -5504, 848], \"expected\": [-5504, 5504, 848], \"passed\": false}, {\"check\": \"oracle 5\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [-56, -56, -280, -280], \"expected\": [56, -56, 280, -280], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [2112, 2112, 4224, 4224], \"expected\": [2112, -2112, 4224, -4224], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [8, 8, -24, -24, 8, 8, -24, -24], \"expected\": [8, -8, 24, -24, 8, -8, 24, -24], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":42.396,"exit_code":1,"observations":[{"actual":[-8,8,-24,24],"check":"oracle 1","expected":[8,-8,24,-24],"passed":false},{"actual":[-264,264,-528,528],"check":"oracle 2","expected":[264,-264,528,-528],"passed":false},{"actual":[-16896,16896,-8448,8448],"check":"oracle 3","expected":[16896,-16896,8448,-8448],"passed":false},{"actual":[5504,-5504,-848],"check":"oracle 4","expected":[-5504,5504,848],"passed":false},{"actual":[],"check":"oracle 5","expected":[],"passed":true},{"actual":[-56,56,-280,280],"check":"oracle 6","expected":[56,-56,280,-280],"passed":false},{"actual":[-2112,2112,-4224,4224],"check":"oracle 7","expected":[2112,-2112,4224,-4224],"passed":false},{"actual":[-8,8,-24,24,-8,8,-24,24],"check":"variant packet 1","expected":[8,-8,24,-24,8,-8,24,-24],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [-8, 8, -24, 24], \"expected\": [8, -8, 24, -24], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [-264, 264, -528, 528], \"expected\": [264, -264, 528, -528], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [-16896, 16896, -8448, 8448], \"expected\": [16896, -16896, 8448, -8448], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [5504, -5504, -848], \"expected\": [-5504, 5504, 848], \"passed\": false}, {\"check\": \"oracle 5\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [-56, 56, -280, 280], \"expected\": [56, -56, 280, -280], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [-2112, 2112, -4224, 4224], \"expected\": [2112, -2112, 4224, -4224], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [-8, 8, -24, 24, -8, 8, -24, 24], \"expected\": [8, -8, 24, -24, 8, -8, 24, -24], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":40.927,"exit_code":0,"observations":[{"actual":[8,-8,24,-24],"check":"oracle 1","expected":[8,-8,24,-24],"passed":true},{"actual":[264,-264,528,-528],"check":"oracle 2","expected":[264,-264,528,-528],"passed":true},{"actual":[16896,-16896,8448,-8448],"check":"oracle 3","expected":[16896,-16896,8448,-8448],"passed":true},{"actual":[-5504,5504,848],"check":"oracle 4","expected":[-5504,5504,848],"passed":true},{"actual":[],"check":"oracle 5","expected":[],"passed":true},{"actual":[56,-56,280,-280],"check":"oracle 6","expected":[56,-56,280,-280],"passed":true},{"actual":[2112,-2112,4224,-4224],"check":"oracle 7","expected":[2112,-2112,4224,-4224],"passed":true},{"actual":[8,-8,24,-24,8,-8,24,-24],"check":"variant packet 1","expected":[8,-8,24,-24,8,-8,24,-24],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [8, -8, 24, -24], \"expected\": [8, -8, 24, -24], \"passed\": true}, {\"check\": \"oracle 2\", \"actual\": [264, -264, 528, -528], \"expected\": [264, -264, 528, -528], \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": [16896, -16896, 8448, -8448], \"expected\": [16896, -16896, 8448, -8448], \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": [-5504, 5504, 848], \"expected\": [-5504, 5504, 848], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [56, -56, 280, -280], \"expected\": [56, -56, 280, -280], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [2112, -2112, 4224, -4224], \"expected\": [2112, -2112, 4224, -4224], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [8, -8, 24, -24, 8, -8, 24, -24], \"expected\": [8, -8, 24, -24, 8, -8, 24, -24], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}