{"abstract":"Adding two full-scale channels doubles expected mono loudness.","category":"Audio channel mixing","checks":4,"contract":"Downmix two-channel normalized frames with equal one-half gains and no clipping.","evaluation_group":"xaud-stereo-downmix-average","failed_approach":"Taking only the left channel discards right-only audio.","family":"xaud-stereo-downmix-average","id":"FA-10886","implementations":{"attempt":{"sha256":"7a622d9899b0d2c1a153c7f97d0b566ed69282e18162b2817d6efe970e2a4eea","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(frames):\n    return [left for left,right in frames]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([[1, 1], [1, -1]],)),[1, 0])\ncheck('fixture 2',solve(*([[0.5, 0]],)),[0.25])\ncheck('fixture 3',solve(*([],)),[])\ncheck('fixture 4',solve(*([[0, -1]],)),[-0.5])\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":"4770bea03ae3d1b5956943f7c9bdb7625d53989bdbd52ce13a1cba848beedb3a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(frames):\n    return [left+right for left,right in frames]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([[1, 1], [1, -1]],)),[1, 0])\ncheck('fixture 2',solve(*([[0.5, 0]],)),[0.25])\ncheck('fixture 3',solve(*([],)),[])\ncheck('fixture 4',solve(*([[0, -1]],)),[-0.5])\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"},"fixed":{"sha256":"bb844e511b96924af21e60ec16d18867d4b2c6b34224b05f3b8fd93230292ffb","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(frames):\n    return [(left+right)/2 for left,right in frames]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1',solve(*([[1, 1], [1, -1]],)),[1, 0])\ncheck('fixture 2',solve(*([[0.5, 0]],)),[0.25])\ncheck('fixture 3',solve(*([],)),[])\ncheck('fixture 4',solve(*([[0, -1]],)),[-0.5])\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":" 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-stereo-downmix-average","generated_at":"2026-09-29T14:38:43.114510+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.","repair":"Apply the explicit PCM/playback contract: Downmix two-channel normalized frames with equal one-half gains and no clipping.","root_cause":"Adding two full-scale channels doubles expected mono loudness.","sha256":"ca8df0441d3be8dfd9b6322c6bf57368784cff779c8235172e6c46d4a996f35d","title":"Stereo downmix average · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":38.458,"exit_code":1,"observations":[{"actual":[1,1],"check":"fixture 1","expected":[1,0],"passed":false},{"actual":[0.5],"check":"fixture 2","expected":[0.25],"passed":false},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[0],"check":"fixture 4","expected":[-0.5],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [1, 1], \"expected\": [1, 0], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [0.5], \"expected\": [0.25], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [0], \"expected\": [-0.5], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.737,"exit_code":1,"observations":[{"actual":[2,0],"check":"fixture 1","expected":[1,0],"passed":false},{"actual":[0.5],"check":"fixture 2","expected":[0.25],"passed":false},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[-1],"check":"fixture 4","expected":[-0.5],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [2, 0], \"expected\": [1, 0], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [0.5], \"expected\": [0.25], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [-1], \"expected\": [-0.5], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":36.228,"exit_code":0,"observations":[{"actual":[1.0,0.0],"check":"fixture 1","expected":[1,0],"passed":true},{"actual":[0.25],"check":"fixture 2","expected":[0.25],"passed":true},{"actual":[],"check":"fixture 3","expected":[],"passed":true},{"actual":[-0.5],"check":"fixture 4","expected":[-0.5],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [1.0, 0.0], \"expected\": [1, 0], \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": [0.25], \"expected\": [0.25], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [-0.5], \"expected\": [-0.5], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}