FA-11216 / Media timeline seeking / Open access
Seek discard preroll presentation · case 01
Decoded preroll frames before the seek target are shown to the viewer.
ROOT CAUSE
Decoded preroll frames before the seek target are shown to the viewer.
VERIFIED REPAIR
Preserve the media contract: After decoding from a preceding keyframe, suppress presentation frames [PTS,payload] before target while retaining an exact-target frame.
Unsuccessful approach: Strict suppression also discards the exact requested presentation timestamp.
Case contract
After decoding from a preceding keyframe, suppress presentation frames [PTS,payload] before target while retaining an exact-target frame.
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, target):
return list(frames)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[8, 'a'], [10, 'b'], [12, 'c']], 10)),[[10, 'b'], [12, 'c']])
check('fixture 2',solve(*([[1, 'a']], 0)),[[1, 'a']])
check('fixture 3',solve(*([[1, 'a']], 2)),[])
check('fixture 4',solve(*([], 0)),[])
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 | [[8, 'a'], [10, 'b'], [12, 'c']] | [[10, 'b'], [12, 'c']] | Failed |
| fixture 2 | [[1, 'a']] | [[1, 'a']] | Passed |
| fixture 3 | [[1, 'a']] | [] | Failed |
| fixture 4 | [] | [] | Passed |
SHA-256 / f218200091fdc1e76be1eb9a9a58200a529cac4d5931dadee57ac3a82881fe51
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(frames, target):
return [f for f in frames if f[0]>target]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[8, 'a'], [10, 'b'], [12, 'c']], 10)),[[10, 'b'], [12, 'c']])
check('fixture 2',solve(*([[1, 'a']], 0)),[[1, 'a']])
check('fixture 3',solve(*([[1, 'a']], 2)),[])
check('fixture 4',solve(*([], 0)),[])
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 | [[12, 'c']] | [[10, 'b'], [12, 'c']] | Failed |
| fixture 2 | [[1, 'a']] | [[1, 'a']] | Passed |
| fixture 3 | [] | [] | Passed |
| fixture 4 | [] | [] | Passed |
SHA-256 / 446d5df28753aa44d150a9bfdf1e3b3acf787ec2f815e5b815421d26c9f18bbc
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(frames, target):
return [f for f in frames if f[0]>=target]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[8, 'a'], [10, 'b'], [12, 'c']], 10)),[[10, 'b'], [12, 'c']])
check('fixture 2',solve(*([[1, 'a']], 0)),[[1, 'a']])
check('fixture 3',solve(*([[1, 'a']], 2)),[])
check('fixture 4',solve(*([], 0)),[])
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 | [[10, 'b'], [12, 'c']] | [[10, 'b'], [12, 'c']] | Passed |
| fixture 2 | [[1, 'a']] | [[1, 'a']] | Passed |
| fixture 3 | [] | [] | Passed |
| fixture 4 | [] | [] | Passed |
SHA-256 / 70a939b1e6512df53885d816160ddb1a79143600bbfe354f667665746a1904b1
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 2026-09-29T14:38:46.021499+00:00.
Case digest / 833298f03d7b98d2326790a0369f2b5cc703927cf012cd8710b57d274f761499