{"abstract":"Left amplitude subtracts the recovered base channel.","category":"PCM sample encoding","checks":8,"contract":"Invert the stipulated reversible PCM midpoint/side code, rejecting parity-mismatched triples and preserving L,R destination order.","contract_signature":"triples","evaluation_group":"s3-pcm-pcm-mid-side-unlifting","failed_approach":"Using midpoint as residual increases common-mode amplitude.","family":"s3-pcm-pcm-mid-side-unlifting-left-recovery","id":"FA-49306","implementations":{"attempt":{"sha256":"58e261047796770ab9d6c804704cdc338c0b798f8f9f0a8e53ab53e90063a9b4","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(triples):\n    out=[]\n    for mid,side,parity in triples:\n        if parity!=(side&1):\n            out.append(None)\n            continue\n        right=mid-side//2\n        left=mid+right\n        out.append([left,right])\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([[3, 3, 1], [3, -3, 1]],)), [[5, 2], [2, 5]])\ncheck('oracle 2', solve(*([[0, 0, 0], [1, 0, 0]],)), [[0, 0], [1, 1]])\ncheck('oracle 3', solve(*([[0, -5, 1]],)), [[-2, 3]])\ncheck('oracle 4', solve(*([],)), [])\ncheck('oracle 5', solve(*([[3, 2, 1], [3, 2, 0]],)), [None, [4, 2]])\ncheck('oracle 6', solve(*([[-2, -1, 1], [4, 1, 1]],)), [[-2, -1], [5, 4]])\ncheck('oracle 7', solve(*([[3, 0, 1]],)), [None])\nif N == 1: check('variant packet 1', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 2: check('variant packet 2', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 3: check('variant packet 3', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 4: check('variant packet 4', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 5: check('variant packet 5', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\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":"29a84297bf8b8318fc2828c24d79694fe9ec56355bc18ff80859100b68253981","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(triples):\n    out=[]\n    for mid,side,parity in triples:\n        if parity!=(side&1):\n            out.append(None)\n            continue\n        right=mid-side//2\n        left=side-right\n        out.append([left,right])\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([[3, 3, 1], [3, -3, 1]],)), [[5, 2], [2, 5]])\ncheck('oracle 2', solve(*([[0, 0, 0], [1, 0, 0]],)), [[0, 0], [1, 1]])\ncheck('oracle 3', solve(*([[0, -5, 1]],)), [[-2, 3]])\ncheck('oracle 4', solve(*([],)), [])\ncheck('oracle 5', solve(*([[3, 2, 1], [3, 2, 0]],)), [None, [4, 2]])\ncheck('oracle 6', solve(*([[-2, -1, 1], [4, 1, 1]],)), [[-2, -1], [5, 4]])\ncheck('oracle 7', solve(*([[3, 0, 1]],)), [None])\nif N == 1: check('variant packet 1', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 2: check('variant packet 2', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 3: check('variant packet 3', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 4: check('variant packet 4', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\nif N == 5: check('variant packet 5', solve(*[[[3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1], [3, 3, 1], [3, -3, 1]]]), [[5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5], [5, 2], [2, 5]])\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-mid-side-unlifting-left-recovery","generated_at":"2026-09-29T14:44:58.899341+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":"Left amplitude subtracts the recovered base channel.","sha256":"df0afe570677de4f40d3f3e5b235912ef3eb94d4c9967a16c25c1d3b87149220","title":"Pcm mid side unlifting: left recovery · 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":41.587,"exit_code":1,"observations":[{"actual":[[5,2],[8,5]],"check":"oracle 1","expected":[[5,2],[2,5]],"passed":false},{"actual":[[0,0],[2,1]],"check":"oracle 2","expected":[[0,0],[1,1]],"passed":false},{"actual":[[3,3]],"check":"oracle 3","expected":[[-2,3]],"passed":false},{"actual":[],"check":"oracle 4","expected":[],"passed":true},{"actual":[null,[5,2]],"check":"oracle 5","expected":[null,[4,2]],"passed":false},{"actual":[[-3,-1],[8,4]],"check":"oracle 6","expected":[[-2,-1],[5,4]],"passed":false},{"actual":[null],"check":"oracle 7","expected":[null],"passed":true},{"actual":[[5,2],[8,5],[5,2],[8,5]],"check":"variant packet 1","expected":[[5,2],[2,5],[5,2],[2,5]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[5, 2], [8, 5]], \"expected\": [[5, 2], [2, 5]], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[0, 0], [2, 1]], \"expected\": [[0, 0], [1, 1]], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [[3, 3]], \"expected\": [[-2, 3]], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [null, [5, 2]], \"expected\": [null, [4, 2]], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[-3, -1], [8, 4]], \"expected\": [[-2, -1], [5, 4]], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [null], \"expected\": [null], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [[5, 2], [8, 5], [5, 2], [8, 5]], \"expected\": [[5, 2], [2, 5], [5, 2], [2, 5]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.608,"exit_code":1,"observations":[{"actual":[[1,2],[-8,5]],"check":"oracle 1","expected":[[5,2],[2,5]],"passed":false},{"actual":[[0,0],[-1,1]],"check":"oracle 2","expected":[[0,0],[1,1]],"passed":false},{"actual":[[-8,3]],"check":"oracle 3","expected":[[-2,3]],"passed":false},{"actual":[],"check":"oracle 4","expected":[],"passed":true},{"actual":[null,[0,2]],"check":"oracle 5","expected":[null,[4,2]],"passed":false},{"actual":[[0,-1],[-3,4]],"check":"oracle 6","expected":[[-2,-1],[5,4]],"passed":false},{"actual":[null],"check":"oracle 7","expected":[null],"passed":true},{"actual":[[1,2],[-8,5],[1,2],[-8,5]],"check":"variant packet 1","expected":[[5,2],[2,5],[5,2],[2,5]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[1, 2], [-8, 5]], \"expected\": [[5, 2], [2, 5]], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[0, 0], [-1, 1]], \"expected\": [[0, 0], [1, 1]], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [[-8, 3]], \"expected\": [[-2, 3]], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [null, [0, 2]], \"expected\": [null, [4, 2]], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[0, -1], [-3, 4]], \"expected\": [[-2, -1], [5, 4]], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [null], \"expected\": [null], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [[1, 2], [-8, 5], [1, 2], [-8, 5]], \"expected\": [[5, 2], [2, 5], [5, 2], [2, 5]], \"passed\": false}], \"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."}}