I started talking about codecs and then kind of wandered into bitrate territory before remembering the actual key point: temporal redundancy.
Start by explaining the fundamental difference in data redundancy: a still image is a single frame with limited spatial redundancy, while a video consists of many frames with high temporal redundancy. Then discuss how video codecs exploit both spatial and temporal redundancy, often achieving much higher compression ratios than image codecs. Finally, mention the trade-offs in complexity and quality.
Pro tip: Emphasize that video compression leverages inter-frame prediction (motion compensation) which is not available for still images, and that this is a key reason for the size difference. Also, note that the perceived quality can be maintained because human vision is less sensitive to certain temporal artifacts.
Explain that compression reduces file size by eliminating redundancy. Still images have only spatial redundancy, while videos have both spatial and temporal redundancy.
Describe how image compression (e.g., JPEG) exploits spatial redundancy within a single frame, but is limited by the need to preserve details in that one frame.
Explain that consecutive video frames are often very similar, so video codecs can encode only the differences between frames (inter-frame prediction), drastically reducing data.
Mention techniques like motion estimation/compensation, keyframes (I-frames), and predictive frames (P/B-frames) that allow video to achieve much higher compression ratios.
Note that video compression is more complex, computationally intensive, and may introduce artifacts, but the high temporal redundancy makes the size reduction worthwhile.
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