{"abstract":"The reconstruction midpoint is omitted in the lowest segment.","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":"Adding a full step instead of half step biases every decoded code.","family":"s3-pcm-alaw-expansion-half-step-offset","id":"FA-48996","implementations":{"attempt":{"sha256":"5de8f54fdaf6b6df7c9091d8556e051ee1f8b0397775a9d7f38e50c740911521","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)+16\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"},"broken":{"sha256":"fe1089bd81e4a927db7e7105c2aaf6c902c3ee35bfd667934d1f08c959a738ca","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)\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-half-step-offset","generated_at":"2026-09-29T14:44:55.778184+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 half step offset.","root_cause":"The reconstruction midpoint is omitted in the lowest segment.","sha256":"1f9dd5183a96327cdf94e8dd09116a80058a97706990f8b2ac0190ec14f5117d","title":"Alaw expansion: half step offset · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":40.448,"exit_code":1,"observations":[{"actual":[16,-16,32,-32],"check":"oracle 1","expected":[8,-8,24,-24],"passed":false},{"actual":[272,-272,544,-544],"check":"oracle 2","expected":[264,-264,528,-528],"passed":false},{"actual":[17408,-17408,8704,-8704],"check":"oracle 3","expected":[16896,-16896,8448,-8448],"passed":false},{"actual":[-5632,5632,864],"check":"oracle 4","expected":[-5504,5504,848],"passed":false},{"actual":[],"check":"oracle 5","expected":[],"passed":true},{"actual":[64,-64,288,-288],"check":"oracle 6","expected":[56,-56,280,-280],"passed":false},{"actual":[2176,-2176,4352,-4352],"check":"oracle 7","expected":[2112,-2112,4224,-4224],"passed":false},{"actual":[16,-16,32,-32,16,-16,32,-32],"check":"variant packet 1","expected":[8,-8,24,-24,8,-8,24,-24],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [16, -16, 32, -32], \"expected\": [8, -8, 24, -24], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [272, -272, 544, -544], \"expected\": [264, -264, 528, -528], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [17408, -17408, 8704, -8704], \"expected\": [16896, -16896, 8448, -8448], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [-5632, 5632, 864], \"expected\": [-5504, 5504, 848], \"passed\": false}, {\"check\": \"oracle 5\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [64, -64, 288, -288], \"expected\": [56, -56, 280, -280], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [2176, -2176, 4352, -4352], \"expected\": [2112, -2112, 4224, -4224], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [16, -16, 32, -32, 16, -16, 32, -32], \"expected\": [8, -8, 24, -24, 8, -8, 24, -24], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.281,"exit_code":1,"observations":[{"actual":[0,0,16,-16],"check":"oracle 1","expected":[8,-8,24,-24],"passed":false},{"actual":[256,-256,512,-512],"check":"oracle 2","expected":[264,-264,528,-528],"passed":false},{"actual":[16384,-16384,8192,-8192],"check":"oracle 3","expected":[16896,-16896,8448,-8448],"passed":false},{"actual":[-5376,5376,832],"check":"oracle 4","expected":[-5504,5504,848],"passed":false},{"actual":[],"check":"oracle 5","expected":[],"passed":true},{"actual":[48,-48,272,-272],"check":"oracle 6","expected":[56,-56,280,-280],"passed":false},{"actual":[2048,-2048,4096,-4096],"check":"oracle 7","expected":[2112,-2112,4224,-4224],"passed":false},{"actual":[0,0,16,-16,0,0,16,-16],"check":"variant packet 1","expected":[8,-8,24,-24,8,-8,24,-24],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [0, 0, 16, -16], \"expected\": [8, -8, 24, -24], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [256, -256, 512, -512], \"expected\": [264, -264, 528, -528], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [16384, -16384, 8192, -8192], \"expected\": [16896, -16896, 8448, -8448], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [-5376, 5376, 832], \"expected\": [-5504, 5504, 848], \"passed\": false}, {\"check\": \"oracle 5\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [48, -48, 272, -272], \"expected\": [56, -56, 280, -280], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [2048, -2048, 4096, -4096], \"expected\": [2112, -2112, 4224, -4224], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [0, 0, 16, -16, 0, 0, 16, -16], \"expected\": [8, -8, 24, -24, 8, -8, 24, -24], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":36.824,"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"}