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Miguel Ángel
3a72aa528d
## Summary Fixes #1317 — systematic duplicate+skip video frames when clip `data-start` is aligned to the output frame grid. ### Root cause `Math.floor(localTime * fps)` in `getFrameAtTime` produces off-by-one errors when the product lands exactly on an integer boundary due to IEEE 754 float noise. For example, `0.28 * 25 === 6.999999999999999` instead of `7`, causing `Math.floor` to return 6 (duplicate of previous frame) instead of 7. ### Fix 1. Add `1e-9` epsilon before flooring: `Math.floor(localTime * fps + 1e-9)` — nudges boundary values like `6.999999` to `7.000000` without affecting mid-frame values. 2. Include `mediaStart` in the frame index computation so trimmed clips (`data-media-start`) map to the correct extracted frames. Both call sites fixed: `getFrameAtTime()` (public API) and the `FrameLookupTable.getFramesAtTime()` bulk lookup. ### Reporter's measurements (before fix) | Case | Duplicates (of 351 frames) | |---|---| | Source file | 1 | | data-start="0" | 14 | | data-start="230.44" (production) | 127 | | data-start="0.02" (half-frame offset workaround) | 1 | ## Test plan - [x] 4 new regression tests for IEEE 754 boundary precision - [x] No duplicate frames when data-start is grid-aligned (25fps) - [x] Monotonically increasing frame indices across 100 frames - [x] Correct frame at the `0.28 * 25` boundary (frame 7, not 6) - [x] `mediaStart` correctly offsets frame index - [x] Typecheck clean