FA-11206 / Media timeline seeking / Open access
Presentation order distinct from decode · case 01
Decoded B-frames are displayed in decode order instead of presentation order.
ROOT CAUSE
Decoded B-frames are displayed in decode order instead of presentation order.
VERIFIED REPAIR
Preserve the media contract: Frames are [decode timestamp,presentation timestamp,payload]. Return stable presentation order, retaining input order for equal presentation timestamps.
Unsuccessful approach: Sorting decode timestamps explicitly preserves the wrong temporal order.
Case contract
Frames are [decode timestamp,presentation timestamp,payload]. Return stable presentation order, retaining input order for equal presentation timestamps.
Why this case matters
A deterministic local media controller stage; metadata and downloaded data are supplied explicitly. No external player, service or codec is required.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(frames):
return list(frames)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[0, 0, 'I'], [1, 2, 'P'], [2, 1, 'B']],)),[[0, 0, 'I'], [2, 1, 'B'], [1, 2, 'P']])
check('fixture 2',solve(*([],)),[])
check('fixture 3',solve(*([[2, 0, 'a'], [1, 0, 'b']],)),[[2, 0, 'a'], [1, 0, 'b']])
check('fixture 4',solve(*([[0, 1, 'a']],)),[[0, 1, 'a']])
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, 'I'], [1, 2, 'P'], [2, 1, 'B']] | [[0, 0, 'I'], [2, 1, 'B'], [1, 2, 'P']] | Failed |
| fixture 2 | [] | [] | Passed |
| fixture 3 | [[2, 0, 'a'], [1, 0, 'b']] | [[2, 0, 'a'], [1, 0, 'b']] | Passed |
| fixture 4 | [[0, 1, 'a']] | [[0, 1, 'a']] | Passed |
SHA-256 / 9165d3187cd57f856d77719ddf599011dee539e208ce1f4f54161114e49ad06f
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(frames):
return sorted(frames,key=lambda f:f[0])
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[0, 0, 'I'], [1, 2, 'P'], [2, 1, 'B']],)),[[0, 0, 'I'], [2, 1, 'B'], [1, 2, 'P']])
check('fixture 2',solve(*([],)),[])
check('fixture 3',solve(*([[2, 0, 'a'], [1, 0, 'b']],)),[[2, 0, 'a'], [1, 0, 'b']])
check('fixture 4',solve(*([[0, 1, 'a']],)),[[0, 1, 'a']])
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, 'I'], [1, 2, 'P'], [2, 1, 'B']] | [[0, 0, 'I'], [2, 1, 'B'], [1, 2, 'P']] | Failed |
| fixture 2 | [] | [] | Passed |
| fixture 3 | [[1, 0, 'b'], [2, 0, 'a']] | [[2, 0, 'a'], [1, 0, 'b']] | Failed |
| fixture 4 | [[0, 1, 'a']] | [[0, 1, 'a']] | Passed |
SHA-256 / 1345cc4cb6d1d14634d6a7cfedcf5180ebece535c119076e80c5b85215a7b2f4
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(frames):
return sorted(frames,key=lambda f:f[1])
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[0, 0, 'I'], [1, 2, 'P'], [2, 1, 'B']],)),[[0, 0, 'I'], [2, 1, 'B'], [1, 2, 'P']])
check('fixture 2',solve(*([],)),[])
check('fixture 3',solve(*([[2, 0, 'a'], [1, 0, 'b']],)),[[2, 0, 'a'], [1, 0, 'b']])
check('fixture 4',solve(*([[0, 1, 'a']],)),[[0, 1, 'a']])
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, 'I'], [2, 1, 'B'], [1, 2, 'P']] | [[0, 0, 'I'], [2, 1, 'B'], [1, 2, 'P']] | Passed |
| fixture 2 | [] | [] | Passed |
| fixture 3 | [[2, 0, 'a'], [1, 0, 'b']] | [[2, 0, 'a'], [1, 0, 'b']] | Passed |
| fixture 4 | [[0, 1, 'a']] | [[0, 1, 'a']] | Passed |
SHA-256 / a4135958fcff2f968434bc00ab2fe84cbbff02fc7ec9fbec3f5d19900b02d0c2
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 2026-09-29T14:38:45.939253+00:00.
Case digest / 9ae2e3a17a5c7fe7ddf6232aaf0afef514f657ad62b04c65716d17dade8c3ea9