What is Digital Video?

Digital Video: Simple Definition

Digital video is a sequence of photographs (frames) displayed in rapid succession to create the illusion of movement. Just like a flipbook, when individual still images are shown fast enough, the human eye perceives smooth motion.

Standard video plays 24, 30, or 60 frames per second (fps). At 30fps, a 1-minute video contains 1,800 individual image frames. Without compression, this would be enormous - that's why video codecs like H.264 and H.265 are essential.

Why Video Compresses So Well

Successive frames usually differ only slightly, so video codecs encode most frames as changes from neighboring ones rather than as full pictures.^[3] Self-contained keyframes are interspersed with predicted frames that store only motion and differences, which is how an hour of footage shrinks to a fraction of its raw size.^[3] This temporal compression is why a mostly static shot compresses far smaller than fast action with constant scene changes: the more each frame resembles the last, the less the codec has to store.

Frame Rate and Scanning

Beyond resolution, video is defined by its frame rate and whether it is progressive (each frame drawn whole) or interlaced (alternating half-frames of odd and even lines), a legacy of broadcast television.^[3] Higher frame rates smooth fast motion but multiply the data the codec must handle.^[3] Common rates are 24 fps for a cinematic look, 30 fps for general video, and 60 fps for smooth motion in gaming and sports footage.

What Decides a Video's Size

Four factors together set a video file's size and quality: resolution (how many pixels per frame), frame rate (how many frames per second), bitrate (how many bits per second of data), and the codec (how efficiently those bits are used). Raising resolution or frame rate increases the data the codec must compress; raising bitrate preserves more detail but grows the file; a more efficient codec gets the same quality from fewer bits. Understanding these four explains why one 1080p video is tiny and another is huge.

Streams Inside a Container

A finished video file is rarely a single thing: a container interleaves the compressed video with one or more audio tracks, subtitles and metadata, keeping them in sync during playback.^[1] Utilities like FFmpeg can extract, transcode or repackage these individual streams.^[2]

How Digital Video Works

Modern video codecs do not store every frame as a complete image. They store a full frame (keyframe) and then only the differences between that frame and subsequent frames. A static background only needs to be stored once, not in every frame.

This temporal compression is why a 10-minute video in H.264 might only be 500MB when the raw uncompressed frames would be 100GB+. The codec's efficiency directly determines the trade-off between file size and quality.

Examples of Digital Video

Frequently Asked Questions