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>
Replace complex overlap/catch-up logic with simpler approach:
- Snap pause points to midpoint between sentences (not sentence boundaries)
- Add 500ms silence before AND after AD audio during freeze frame
- Resume playback from same midpoint (no overlap, no visual jump-back)
This eliminates audio/visual anomalies caused by the previous algorithm's
complexity around sentence boundary snapping and audio catch-up.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Changes pause point calculation to use the entire gap between sentences
as a buffer on BOTH sides of the audio description:
- pause_point: Just BEFORE next sentence starts (gap.end - 50ms)
- resume_from: Just AFTER previous sentence ends (gap.start + 50ms)
This means a small portion of video plays twice (the gap duration), but
creates a much more natural listening experience by maximizing the
breathing room around audio descriptions.
Changes:
- whisper_service.py: snap_pause_point() now returns (pause_point, resume_from)
- video_renderer.py: Uses resume_from for current_time after freeze segment
- vtt_retimer.py: Calculates effective_offset including overlap duration
- accessible_video.py: Added resume_from field to ADPlacementCue schema
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Add new deliverable type that renders video with audio descriptions embedded.
Supports two AI-determined methods:
- Direct Overlay: ducks original audio and overlays AD TTS (for minimal dialogue)
- Pause-Insert: freeze-frame video, insert AD, re-time subtitles (for significant dialogue)
Backend:
- Add Pydantic schemas for Gemini analysis response
- Add Gemini prompt and analyze_accessible_video_placement() method
- Add video_renderer.py service using FFmpeg for both rendering methods
- Add vtt_retimer.py service for pause-insert subtitle adjustment
- Add render_accessible_video.py Celery task
- Modify TTS service to return individual per-cue segments
- Update translate_and_synthesize.py to save segments and trigger rendering
- Update download endpoint to include accessible video outputs
Frontend:
- Add accessible_video_mp4 checkbox to NewJob form
- Update TypeScript types for new deliverable
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
