Editing video on a timeline
Computer ScienceDigital ApplicationsAges 14–15
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Digital Applications
A video-editing timeline with several scenes: students click to select a scene, drag its right edge to trim it, split it in two, delete it, reorder it, and insert transition effects, then press Play to watch the playhead move through the scenes. Total duration, file size, and render time are all recomputed with the formula size = bitrate × duration ÷ 8, using the bitrate for the actual resolution of H.264 video.
Lesson: Photo and video editing software: trimming, splicing, transitions and exporting files
What it shows
Video editing software arranges clips, or scenes, on a timeline, and the finished film is exported by encoding every second of footage at a chosen bitrate. This simulation models that workflow: scenes can be trimmed, split, deleted, reordered and joined with transitions, and the total running time includes each transition. File size follows size (MB) = bitrate (Mbps) × duration (s) ÷ 8, with the video and background-audio bitrates added together, so a higher resolution raises both file size and render time. Students see the trade-off between image quality, storage and export time.
How to use
Select a scene on the timeline and drag its right edge to trim it, then use Split scene, Delete scene and the Move buttons to rebuild the story. Change the Transition effect and note how the total duration changes. Press Play to preview the edit. Finally, switch the Resolution from 480p to 4K without changing the edit, and compare the file size and render time.
Parameters you can change
- Initial number of scenes 3–8 scenes
- Resolution 480p – 2.5 Mbps, 720p HD – 5 Mbps, 1080p Full HD – 8 Mbps, 2160p 4K – 40 Mbps
- Transition effect Hard cut (0 s), Fade (1 s), Slide (0.5 s)
- Background music volume 0–100 %
- Show file size and render time
Questions to explore
- About how many megabytes does a 60-second 1080p video need, including the background audio?
- How does changing every transition from Hard cut to Fade affect the total duration of the film?
- When would exporting at 720p be a better choice than 4K?
