{"abstract":"An unnormalized mid/side matrix doubles channel amplitudes.","category":"Audio channel mixing","checks":4,"contract":"Encode stereo left/right frames as normalized mid=(L+R)/2 and side=(L-R)/2 for a sum/difference channel representation.","contract_signature":"frames","evaluation_group":"xaud-mid-side-encode-normalization","failed_approach":"Reversed subtraction swaps the spatial sign of the side channel.","family":"xaud-mid-side-encode-normalization","id":"FA-11016","implementations":{"attempt":{"sha256":"6b947d37b4134574e7b511ee71ba73f78d2fca09ab748ab3734763e57c2a1c52","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(frames):\n    return [[(left+right)/2,(right-left)/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, 0]])\ncheck('fixture 2',solve(*([[1, -1]],)),[[0, 1]])\ncheck('fixture 3',solve(*([[0, 1]],)),[[0.5, -0.5]])\ncheck('fixture 4',solve(*([],)),[])\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":"2ac788778a9d11777f2a6f7b3a851c2f78a0ba1c7fb8bcdf9806241b784aa283","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(frames):\n    return [[left+right,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, 0]])\ncheck('fixture 2',solve(*([[1, -1]],)),[[0, 1]])\ncheck('fixture 3',solve(*([[0, 1]],)),[[0.5, -0.5]])\ncheck('fixture 4',solve(*([],)),[])\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-mid-side-encode-normalization","generated_at":"2026-09-29T14:38:44.302927+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":"An unnormalized mid/side matrix doubles channel amplitudes.","sha256":"204133ebd885ae53566d16d7d0905ca71ecd4446dc80449c57a33f4a178acb81","title":"Mid side encode normalization · 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":41.896,"exit_code":1,"observations":[{"actual":[[1.0,0.0]],"check":"fixture 1","expected":[[1,0]],"passed":true},{"actual":[[0.0,-1.0]],"check":"fixture 2","expected":[[0,1]],"passed":false},{"actual":[[0.5,0.5]],"check":"fixture 3","expected":[[0.5,-0.5]],"passed":false},{"actual":[],"check":"fixture 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [[1.0, 0.0]], \"expected\": [[1, 0]], \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": [[0.0, -1.0]], \"expected\": [[0, 1]], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [[0.5, 0.5]], \"expected\": [[0.5, -0.5]], \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.289,"exit_code":1,"observations":[{"actual":[[2,0]],"check":"fixture 1","expected":[[1,0]],"passed":false},{"actual":[[0,2]],"check":"fixture 2","expected":[[0,1]],"passed":false},{"actual":[[1,-1]],"check":"fixture 3","expected":[[0.5,-0.5]],"passed":false},{"actual":[],"check":"fixture 4","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [[2, 0]], \"expected\": [[1, 0]], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [[0, 2]], \"expected\": [[0, 1]], \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": [[1, -1]], \"expected\": [[0.5, -0.5]], \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": [], \"expected\": [], \"passed\": true}], \"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."}}