{"abstract":"Both predictor taps retain the newest decoded sample.","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.","evaluation_group":"s3-pcm-pcm-two-tap-predictor","failed_approach":"Never shifting the older tap freezes obsolete history.","family":"s3-pcm-pcm-two-tap-predictor-history-shift","id":"FA-49811","implementations":{"attempt":{"sha256":"3f35b187441d645e515398150d9998e2e5ad6cf7a9430b034fd82bebbb90abb4","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=older,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":"2e974dd8dfa406cda5447ab692baf0f608f7a942883ec09a5c192f02be6d71cd","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=sample,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"},"fixed":{"sha256":"ba7d0315b3a843c45e96018a179224e53d7c27b1fe15d824d8ba802823a86617","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-history-shift","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.","repair":"Use the stated conversion contract at history shift.","root_cause":"Both predictor taps retain the newest decoded sample.","sha256":"d8284a65fa766101cd774763621400da874bca1edfbf7218c6bea820f6c00328","title":"Pcm two tap predictor: history shift · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":39.803,"exit_code":1,"observations":[{"actual":[[6,6,-8,1],1,1],"check":"oracle 1","expected":[[6,5,-12,-7],-7,-12],"passed":false},{"actual":[[0,1,2],2,-3],"check":"oracle 2","expected":[[0,2,3],3,2],"passed":false},{"actual":[[0,0],0,1],"check":"oracle 3","expected":[[0,-2],-2,0],"passed":false},{"actual":[[],5,2],"check":"oracle 4","expected":[[],5,2],"passed":true},{"actual":[[-24,-24,-3],-3,0],"check":"oracle 5","expected":[[-24,-24,-3],-3,-24],"passed":false},{"actual":[[0,-4,-4],-4,3],"check":"oracle 6","expected":[[0,-4,-2],-2,-4],"passed":false},{"actual":[[-1,-1,-3],-3,-1],"check":"oracle 7","expected":[[-1,-2,-4],-4,-2],"passed":false},{"actual":[[6,6,-8,1,3,2,-14,-8],-8,1],"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\": [[6, 6, -8, 1], 1, 1], \"expected\": [[6, 5, -12, -7], -7, -12], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[0, 1, 2], 2, -3], \"expected\": [[0, 2, 3], 3, 2], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [[0, 0], 0, 1], \"expected\": [[0, -2], -2, 0], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [[], 5, 2], \"expected\": [[], 5, 2], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[-24, -24, -3], -3, 0], \"expected\": [[-24, -24, -3], -3, -24], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[0, -4, -4], -4, 3], \"expected\": [[0, -4, -2], -2, -4], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [[-1, -1, -3], -3, -1], \"expected\": [[-1, -2, -4], -4, -2], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [[6, 6, -8, 1, 3, 2, -14, -8], -8, 1], \"expected\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.307,"exit_code":1,"observations":[{"actual":[[6,4,-12,2],2,2],"check":"oracle 1","expected":[[6,5,-12,-7],-7,-12],"passed":false},{"actual":[[0,2,4],4,4],"check":"oracle 2","expected":[[0,2,3],3,2],"passed":false},{"actual":[[0,0],0,0],"check":"oracle 3","expected":[[0,-2],-2,0],"passed":false},{"actual":[[],5,2],"check":"oracle 4","expected":[[],5,2],"passed":true},{"actual":[[-24,-24,-3],-3,-3],"check":"oracle 5","expected":[[-24,-24,-3],-3,-24],"passed":false},{"actual":[[0,-2,1],1,1],"check":"oracle 6","expected":[[0,-4,-2],-2,-4],"passed":false},{"actual":[[-1,-1,-3],-3,-3],"check":"oracle 7","expected":[[-1,-2,-4],-4,-2],"passed":false},{"actual":[[6,4,-12,2,4,2,-14,0],0,0],"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\": [[6, 4, -12, 2], 2, 2], \"expected\": [[6, 5, -12, -7], -7, -12], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[0, 2, 4], 4, 4], \"expected\": [[0, 2, 3], 3, 2], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [[0, 0], 0, 0], \"expected\": [[0, -2], -2, 0], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [[], 5, 2], \"expected\": [[], 5, 2], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[-24, -24, -3], -3, -3], \"expected\": [[-24, -24, -3], -3, -24], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[0, -2, 1], 1, 1], \"expected\": [[0, -4, -2], -2, -4], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [[-1, -1, -3], -3, -3], \"expected\": [[-1, -2, -4], -4, -2], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [[6, 4, -12, 2, 4, 2, -14, 0], 0, 0], \"expected\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":38.492,"exit_code":0,"observations":[{"actual":[[6,5,-12,-7],-7,-12],"check":"oracle 1","expected":[[6,5,-12,-7],-7,-12],"passed":true},{"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":[[-24,-24,-3],-3,-24],"check":"oracle 5","expected":[[-24,-24,-3],-3,-24],"passed":true},{"actual":[[0,-4,-2],-2,-4],"check":"oracle 6","expected":[[0,-4,-2],-2,-4],"passed":true},{"actual":[[-1,-2,-4],-4,-2],"check":"oracle 7","expected":[[-1,-2,-4],-4,-2],"passed":true},{"actual":[[6,5,-12,-7,-3,-3,-19,-13],-13,-19],"check":"variant packet 1","expected":[[6,5,-12,-7,-3,-3,-19,-13],-13,-19],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[6, 5, -12, -7], -7, -12], \"expected\": [[6, 5, -12, -7], -7, -12], \"passed\": true}, {\"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\": [[-24, -24, -3], -3, -24], \"expected\": [[-24, -24, -3], -3, -24], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [[0, -4, -2], -2, -4], \"expected\": [[0, -4, -2], -2, -4], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [[-1, -2, -4], -4, -2], \"expected\": [[-1, -2, -4], -4, -2], \"passed\": true}, {\"check\": \"variant packet 1\", \"actual\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"expected\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}