{"abstract":"Unsigned PCM silence is interpreted as a positive amplitude.","category":"PCM sample encoding","checks":4,"contract":"Decode unsigned 8-bit PCM byte integers into centered integer amplitudes by subtracting 128.","contract_signature":"samples","evaluation_group":"xaud-unsigned-eight-bit-silence-center","failed_approach":"Centering at 127 shifts every decoded sample by one.","family":"xaud-unsigned-eight-bit-silence-center","id":"FA-10781","implementations":{"attempt":{"sha256":"f47006a1c844dc962e03808c51d1c010b8df55974929fa8d10b3bfbe751732cf","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(samples):\n    return [x-127 for x in samples]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([0, 128, 255],)),[-128, 0, 127])\ncheck('fixture 2',solve(*([128],)),[0])\ncheck('fixture 3',solve(*([],)),[])\ncheck('fixture 4',solve(*([127, 129],)),[-1, 1])\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":"f96dde8e132a95e498227204762f239227bfee1d39c441630221452c4c8be552","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(samples):\n    return list(samples)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([0, 128, 255],)),[-128, 0, 127])\ncheck('fixture 2',solve(*([128],)),[0])\ncheck('fixture 3',solve(*([],)),[])\ncheck('fixture 4',solve(*([127, 129],)),[-1, 1])\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":" 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":"xaud-unsigned-eight-bit-silence-center","generated_at":"2026-09-29T14:38:42.195984+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A pure Python local audio pipeline stage with explicit sample formats and frame conventions; no real-time device or signal-spectrum claims.","root_cause":"Unsigned PCM silence is interpreted as a positive amplitude.","sha256":"39cea7cb3d200acb942e58501937ec690b950f35b5f3379bffb7e9d0b1b18b0d","title":"Unsigned eight bit silence center · 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":45.834,"exit_code":1,"observations":[{"actual":[-127,1,128],"check":"fixture 1","expected":[-128,0,127],"passed":false},{"actual":[1],"check":"fixture 2","expected":[0],"passed":false},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[0,2],"check":"fixture 4","expected":[-1,1],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [-127, 1, 128], \"expected\": [-128, 0, 127], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [1], \"expected\": [0], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [0, 2], \"expected\": [-1, 1], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.984,"exit_code":1,"observations":[{"actual":[0,128,255],"check":"fixture 1","expected":[-128,0,127],"passed":false},{"actual":[128],"check":"fixture 2","expected":[0],"passed":false},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[127,129],"check":"fixture 4","expected":[-1,1],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [0, 128, 255], \"expected\": [-128, 0, 127], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [128], \"expected\": [0], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [127, 129], \"expected\": [-1, 1], \"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."}}