graph TD A[Thumbnail Extraction Subagent] --> B{Input MP4 URL and JSON file with section breakdowns and timestamps} B --> C[Extract Thumbnail Image at Timestamp 1] B --> D[Extract Thumbnail Image at Timestamp 2] B --> E[Extract Thumbnail Image at Timestamp 3] B --> F[Extract Thumbnail Image at Timestamp 4] B --> G[Extract Thumbnail Image at Timestamp 5] B --> H[Extract Thumbnail Image at Timestamp 6] C --> I[Save Thumbnail Image 1 on server] D --> J[Save Thumbnail Image 2 on server] E --> K[Save Thumbnail Image 3 on server] F --> L[Save Thumbnail Image 4 on server] G --> M[Save Thumbnail Image 5 on server] H --> N[Save Thumbnail Image 6 on server] I --> O[Output list of thumbnail images with internal and external URLs] J --> O K --> O L --> O M --> O N --> O