FA-10936 / Audio channel mixing / Open access
Mix bus clear each block · case 01
An uncleared mix bus accumulates audio from the prior callback.
ROOT CAUSE
An uncleared mix bus accumulates audio from the prior callback.
VERIFIED REPAIR
Apply the explicit PCM/playback contract: Mix one new block from equal-length input sources, discarding the previous bus contents. Previous length defines silence when no inputs exist.
Unsuccessful approach: Clearing without accumulating the current sources outputs silence.
Case contract
Mix one new block from equal-length input sources, discarding the previous bus contents. Previous length defines silence when no inputs exist.
Why this case matters
A pure Python local audio pipeline stage with explicit sample formats and frame conventions; no real-time device or signal-spectrum claims.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(previous, inputs):
return [old+sum(frame) for old,frame in zip(previous,zip(*inputs))] if inputs else list(previous)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([5, 5], [[1, 2], [3, 4]])),[4, 6])
check('fixture 2',solve(*([5, 5], [])),[0, 0])
check('fixture 3',solve(*([0], [[2]])),[2])
check('fixture 4',solve(*([], [])),[])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 1 | [9, 11] | [4, 6] | Failed |
| fixture 2 | [5, 5] | [0, 0] | Failed |
| fixture 3 | [2] | [2] | Passed |
| fixture 4 | [] | [] | Passed |
SHA-256 / abe7bb4c7e62bcabc4a55c30ab85d8957ad0341d57555572d4c3a296ded8fad3
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(previous, inputs):
return [0]*len(previous)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([5, 5], [[1, 2], [3, 4]])),[4, 6])
check('fixture 2',solve(*([5, 5], [])),[0, 0])
check('fixture 3',solve(*([0], [[2]])),[2])
check('fixture 4',solve(*([], [])),[])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 1 | [0, 0] | [4, 6] | Failed |
| fixture 2 | [0, 0] | [0, 0] | Passed |
| fixture 3 | [0] | [2] | Failed |
| fixture 4 | [] | [] | Passed |
SHA-256 / 10c901ef523df756e456d8c1e22eb9624cd9b787b3fbff4baf6a4b81a21a03a3
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(previous, inputs):
return [sum(frame) for frame in zip(*inputs)] if inputs else [0]*len(previous)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([5, 5], [[1, 2], [3, 4]])),[4, 6])
check('fixture 2',solve(*([5, 5], [])),[0, 0])
check('fixture 3',solve(*([0], [[2]])),[2])
check('fixture 4',solve(*([], [])),[])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 1 | [4, 6] | [4, 6] | Passed |
| fixture 2 | [0, 0] | [0, 0] | Passed |
| fixture 3 | [2] | [2] | Passed |
| fixture 4 | [] | [] | Passed |
SHA-256 / 529165862341ee68331159b4b0b3506e40f34a9524073cfc8b762c2e88bf3c22
Verification & scope
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.
Observations recorded using Python 3.12.14 at 2026-09-29T14:38:43.552983+00:00.
Case digest / 959b9ab1ab026fbd1a0b4cfa17b54b08ec37fc466d8c0e1affb3aef9b6cbdc0a