{"abstract":"Delta scale is incorrectly applied to the predicted PCM level.","category":"PCM sample encoding","checks":8,"contract":"Stipulated two-history adaptive PCM decoder with explicit integer predictor coefficients, floor divisor, signed residual nibble and fixed residual amplitude scale.","contract_signature":"codes, last, older, coefficients, divisor, delta","evaluation_group":"s3-pcm-pcm-two-tap-predictor","failed_approach":"Ignoring delta changes residual amplitude units.","family":"s3-pcm-pcm-two-tap-predictor-delta-scale","id":"FA-49806","implementations":{"attempt":{"sha256":"0a552634404bffca9670add12f40e4012450da7fec44a38bbfe41569c7883193","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(codes, last, older, coefficients, divisor, delta):\n    out=[]\n    for code in codes:\n        predicted=(last*coefficients[0]+older*coefficients[1])//divisor\n        signed=code-16 if code&8 else code\n        sample=predicted+signed\n        older,last=last,sample\n        out.append(sample)\n    return [out,last,older]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([1, 15, 8, 7], 3, 1, [3, -1], 2, 2)), [[6, 5, -12, -7], -7, -12])\ncheck('oracle 2', solve(*([1, 2, 3], 2, -3, [1, 1], 3, 1)), [[0, 2, 3], 3, 2])\ncheck('oracle 3', solve(*([0, 0], -2, 1, [1, 2], 3, 4)), [[0, -2], -2, 0])\ncheck('oracle 4', solve(*([], 5, 2, [2, -1], 1, 1)), [[], 5, 2])\ncheck('oracle 5', solve(*([8, 0, 7], 0, 0, [1, 0], 1, 3)), [[-24, -24, -3], -3, -24])\ncheck('oracle 6', solve(*([15, 15, 1], 4, 3, [2, -1], 2, 2)), [[0, -4, -2], -2, -4])\ncheck('oracle 7', solve(*([2, 0, 14], -3, -1, [3, 1], 4, 1)), [[-1, -2, -4], -4, -2])\nif N == 1: check('variant packet 1', solve(*[[1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19])\nif N == 2: check('variant packet 2', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18], -18, -24])\nif N == 3: check('variant packet 3', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23], -23, -29])\nif N == 4: check('variant packet 4', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28], -28, -34])\nif N == 5: check('variant packet 5', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28, -23, -23, -39, -33], -33, -39])\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":"a1b3b772962cc820d4c8667cd553ef048b3bb984b1bc18dc49b737fd049c5e43","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(codes, last, older, coefficients, divisor, delta):\n    out=[]\n    for code in codes:\n        predicted=(last*coefficients[0]+older*coefficients[1])//divisor\n        signed=code-16 if code&8 else code\n        sample=(predicted+signed)*delta\n        older,last=last,sample\n        out.append(sample)\n    return [out,last,older]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([1, 15, 8, 7], 3, 1, [3, -1], 2, 2)), [[6, 5, -12, -7], -7, -12])\ncheck('oracle 2', solve(*([1, 2, 3], 2, -3, [1, 1], 3, 1)), [[0, 2, 3], 3, 2])\ncheck('oracle 3', solve(*([0, 0], -2, 1, [1, 2], 3, 4)), [[0, -2], -2, 0])\ncheck('oracle 4', solve(*([], 5, 2, [2, -1], 1, 1)), [[], 5, 2])\ncheck('oracle 5', solve(*([8, 0, 7], 0, 0, [1, 0], 1, 3)), [[-24, -24, -3], -3, -24])\ncheck('oracle 6', solve(*([15, 15, 1], 4, 3, [2, -1], 2, 2)), [[0, -4, -2], -2, -4])\ncheck('oracle 7', solve(*([2, 0, 14], -3, -1, [3, 1], 4, 1)), [[-1, -2, -4], -4, -2])\nif N == 1: check('variant packet 1', solve(*[[1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19])\nif N == 2: check('variant packet 2', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18], -18, -24])\nif N == 3: check('variant packet 3', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23], -23, -29])\nif N == 4: check('variant packet 4', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28], -28, -34])\nif N == 5: check('variant packet 5', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28, -23, -23, -39, -33], -33, -39])\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-two-tap-predictor-delta-scale","generated_at":"2026-09-29T14:45:03.457660+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":"Delta scale is incorrectly applied to the predicted PCM level.","sha256":"f895af1cc0fc1c5e6b70455bb2d4b7ab11dd9de9431a922b84f9cbb0c4024944","title":"Pcm two tap predictor: delta scale · 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":36.579,"exit_code":1,"observations":[{"actual":[[5,5,-3,0],0,-3],"check":"oracle 1","expected":[[6,5,-12,-7],-7,-12],"passed":false},{"actual":[[0,2,3],3,2],"check":"oracle 2","expected":[[0,2,3],3,2],"passed":true},{"actual":[[0,-2],-2,0],"check":"oracle 3","expected":[[0,-2],-2,0],"passed":true},{"actual":[[],5,2],"check":"oracle 4","expected":[[],5,2],"passed":true},{"actual":[[-8,-8,-1],-1,-8],"check":"oracle 5","expected":[[-24,-24,-3],-3,-24],"passed":false},{"actual":[[1,-2,-2],-2,-2],"check":"oracle 6","expected":[[0,-4,-2],-2,-4],"passed":false},{"actual":[[-1,-2,-4],-4,-2],"check":"oracle 7","expected":[[-1,-2,-4],-4,-2],"passed":true},{"actual":[[5,5,-3,0,2,2,-6,-3],-3,-6],"check":"variant packet 1","expected":[[6,5,-12,-7,-3,-3,-19,-13],-13,-19],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[5, 5, -3, 0], 0, -3], \"expected\": [[6, 5, -12, -7], -7, -12], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[0, 2, 3], 3, 2], \"expected\": [[0, 2, 3], 3, 2], \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": [[0, -2], -2, 0], \"expected\": [[0, -2], -2, 0], \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": [[], 5, 2], \"expected\": [[], 5, 2], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[-8, -8, -1], -1, -8], \"expected\": [[-24, -24, -3], -3, -24], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[1, -2, -2], -2, -2], \"expected\": [[0, -4, -2], -2, -4], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [[-1, -2, -4], -4, -2], \"expected\": [[-1, -2, -4], -4, -2], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [[5, 5, -3, 0, 2, 2, -6, -3], -3, -6], \"expected\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.526,"exit_code":1,"observations":[{"actual":[[10,24,46,128],128,46],"check":"oracle 1","expected":[[6,5,-12,-7],-7,-12],"passed":false},{"actual":[[0,2,3],3,2],"check":"oracle 2","expected":[[0,2,3],3,2],"passed":true},{"actual":[[0,-8],-8,0],"check":"oracle 3","expected":[[0,-2],-2,0],"passed":false},{"actual":[[],5,2],"check":"oracle 4","expected":[[],5,2],"passed":true},{"actual":[[-24,-72,-195],-195,-72],"check":"oracle 5","expected":[[-24,-24,-3],-3,-24],"passed":false},{"actual":[[2,-2,-4],-4,-2],"check":"oracle 6","expected":[[0,-4,-2],-2,-4],"passed":false},{"actual":[[-1,-2,-4],-4,-2],"check":"oracle 7","expected":[[-1,-2,-4],-4,-2],"passed":true},{"actual":[[10,24,46,128,340,890,2314,6066],6066,2314],"check":"variant packet 1","expected":[[6,5,-12,-7,-3,-3,-19,-13],-13,-19],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[10, 24, 46, 128], 128, 46], \"expected\": [[6, 5, -12, -7], -7, -12], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[0, 2, 3], 3, 2], \"expected\": [[0, 2, 3], 3, 2], \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": [[0, -8], -8, 0], \"expected\": [[0, -2], -2, 0], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [[], 5, 2], \"expected\": [[], 5, 2], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[-24, -72, -195], -195, -72], \"expected\": [[-24, -24, -3], -3, -24], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[2, -2, -4], -4, -2], \"expected\": [[0, -4, -2], -2, -4], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [[-1, -2, -4], -4, -2], \"expected\": [[-1, -2, -4], -4, -2], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [[10, 24, 46, 128, 340, 890, 2314, 6066], 6066, 2314], \"expected\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"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."}}