Chapter 4 · Watch, then practise
Video and Animation
Relate frame rate and frame representation to video volume. Then use keyframes and interpolation to describe motion independently of how the final frames are encoded.
3 questions · 3 with related videos. Matches are based on playlist titles; broader background matches are labeled.
What to study
- Frame rate and storage
- Keyframes and interpolation
- Temporal compression
Chapter playlists
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Notes
Calculating File Size: Video
Eddie Woo · 4:22
Supplementary video-file-size lesson supports calculating frame storage and raw data rate.
1. Raw video calculation
Calculate the raw data rate for 640 × 480 video at 30 frames/s with 24-bit RGB, excluding audio and overhead.
Rate = 640 × 480 × 30 × 24 = 221,184,000 bit/s, or 221.184 Mb/s. Dividing by eight gives 27.648 MB/s. This explains why storage and delivery commonly use compression; it is not the bitrate of an encoded video file.
Multimedia Technology & Design: Unit 7.2 Computer-based animation
UNIMAS MOOC · 5:02 · Background lecture
Supplementary computer-animation background; the linear interpolation arithmetic is worked in the answer.
2. Linear keyframe example
An object moves from x = 20 at time 0 to x = 100 at time 2 seconds with linear interpolation. Where is it after 0.5 seconds?
Progress is 0.5 / 2 = 0.25. Therefore x = 20 + 0.25 × (100 − 20) = 40. A different easing function changes intermediate positions while preserving the defined endpoints.
Video Compression as Fast As Possible
Techquickie · 6:10
Video-compression explanation from the existing images-and-graphics playlist.
3. Why compare frames?
Why can encoding changes between frames reduce video size?
Nearby frames often share much of their visual content. A codec can encode predicted content and differences instead of storing each complete frame independently. This creates dependencies that affect seeking and recovery after data loss; independent frames provide useful restart points.