system
Given the following post, respond as if you're commenting on Reddit:
human
Are film clips still "moving pictures" when recorded and stored digitally, or does the recording of a digital video work differently from analogue recording?

I put computing as flair, but I'm honestly not sure in which category this belongs. Feel free to mark it with more appropriate flair, admins.
gpt
The basis of digital video formats is still a sequence of still images, just like analogue film.

However, for efficiency purposes, various optimizations are made, because storing a full resolution still image for every single frame would require a large amount of storage space (and a large amount of bandwidth to transfer).

The main way that digital video optimizes storage requirements is by not storing each frame as a full still image. Instead, a frame will only contain the differences between that frame and the previous. For most video clips large parts of the scene remain unchanged between two consecutive frames, which allows the next frame to be constructed using a relatively small amount of data.

In order to facilitate actions like forwarding and rewinding through a video, a "key frame" is inserted at regular intervals. Key frames contain the full image rather than only the differences between two frames. That way it's possible to start playback at a different point than the start of the video without having to first reconstruct the entire set of frames leading up to the selected starting point.

There are various techniques that further optimize the tradeoff between storage, quality and processing power needed, but the basic idea remains the same: Just like with analogue video, digital video still consists of individual frames that are recorded, stored and played sequentially.