Subtitles were appearing progressively out of sync (~1.0s early per AD)
because the VTT retimer calculated freeze durations theoretically
rather than using actual rendered segment durations.
Changes:
- video_renderer: Measure actual freeze segment duration after creation
- video_renderer: Return updated placements with actual_freeze_duration
- vtt_retimer: Prefer actual_freeze_duration over calculated values
- render_task: Pass actual durations to VTT retimer
This ensures subtitle timing matches the real video timeline regardless
of any FFmpeg encoding variations.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
The VTT retimer had two bugs causing subtitles to display during freeze
periods and become out of sync:
1. Same offset applied to both start and end times (should differ when
pause falls between them)
2. Cues spanning pause points weren't split (causing captions during freeze)
Changes:
- Add _offset_at() for timestamps AT or AFTER pause points
- Add _offset_before() for timestamps STRICTLY BEFORE pause points
- Add _retime_cue() to split cues at pause points into multiple segments
- Add _filter_short_segments() to remove <100ms segments after splitting
- Rewrite retime_for_pause_insert() to use new helper methods
Example fix for cue 8s-12s with pause at 10s (4s freeze):
- Before: 8s-12s (displayed during freeze!)
- After: 8s-10s + 14s-16s (gap during AD)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
