FA-11256 / Media timeline seeking / Open access
Media trim rebases timestamps · case 01
Trimmed media retains source timestamps instead of beginning at the trim-relative timeline.
ROOT CAUSE
Trimmed media retains source timestamps instead of beginning at the trim-relative timeline.
VERIFIED REPAIR
Preserve the media contract: Select frames whose presentation starts lie in half-open trim interval and rebase their timestamps by subtracting trim start.
Unsuccessful approach: Inclusive ending timestamps retain the first frame belonging to the next clip.
Case contract
Select frames whose presentation starts lie in half-open trim interval and rebase their timestamps by subtracting trim start.
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, start, end):
return [[t,payload] for t,payload in frames if start<=t<end]
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'], [14, 'd']], 10, 14)),[[0, 'b'], [2, 'c']])
check('fixture 2',solve(*([[5, 'a']], 5, 6)),[[0, 'a']])
check('fixture 3',solve(*([], 0, 1)),[])
check('fixture 4',solve(*([[1, 'a']], 1, 1)),[])
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']] | [[0, 'b'], [2, 'c']] | Failed |
| fixture 2 | [[5, 'a']] | [[0, 'a']] | Failed |
| fixture 3 | [] | [] | Passed |
| fixture 4 | [] | [] | Passed |
SHA-256 / 7ff5de57997c331be915324fed6953477b31783510d7993d2bfa0f4b54d19c57
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(frames, start, end):
return [[t-start,payload] for t,payload in frames if start<=t<=end]
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'], [14, 'd']], 10, 14)),[[0, 'b'], [2, 'c']])
check('fixture 2',solve(*([[5, 'a']], 5, 6)),[[0, 'a']])
check('fixture 3',solve(*([], 0, 1)),[])
check('fixture 4',solve(*([[1, 'a']], 1, 1)),[])
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, 'b'], [2, 'c'], [4, 'd']] | [[0, 'b'], [2, 'c']] | Failed |
| fixture 2 | [[0, 'a']] | [[0, 'a']] | Passed |
| fixture 3 | [] | [] | Passed |
| fixture 4 | [[0, 'a']] | [] | Failed |
SHA-256 / 73b04697f7c5b98700f509b5514de6d8b87771ebcce19c5327ee282e1fde5809
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(frames, start, end):
return [[t-start,payload] for t,payload in frames if start<=t<end]
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'], [14, 'd']], 10, 14)),[[0, 'b'], [2, 'c']])
check('fixture 2',solve(*([[5, 'a']], 5, 6)),[[0, 'a']])
check('fixture 3',solve(*([], 0, 1)),[])
check('fixture 4',solve(*([[1, 'a']], 1, 1)),[])
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, 'b'], [2, 'c']] | [[0, 'b'], [2, 'c']] | Passed |
| fixture 2 | [[0, 'a']] | [[0, 'a']] | Passed |
| fixture 3 | [] | [] | Passed |
| fixture 4 | [] | [] | Passed |
SHA-256 / 2a7a680279b166cb77e869c2715dceb9264f364103c478f34850225eac7e2a58
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 2026-09-29T14:38:46.260954+00:00.
Case digest / c86d674225eb7bc7798759f1dcec7c057cfa4a5c91f86d497b931cd2cbe419a1