What Is Video?

Video is a technology for capturing, storing, transmitting, and displaying sequences of still images in rapid succession to create the perception of motion. Each image in a video sequence is called a frame, and the rate at which frames are displayed, measured in frames per second (fps), determines how smoothly motion is perceived. Standard broadcast television operates at 25 or 30 fps, while high-frame-rate systems used in cinema and gaming extend to 60 fps or beyond.

Video draws its roots from analog television, where an electromagnetic signal encodes a continuous stream of brightness and color information. The transition to digital video in the 1980s and 1990s transformed the field: frames became discrete grids of pixels, and values for luminance and chrominance could be processed, stored, and transmitted with the same mathematical tools applied to other digital signals. The IEEE Signal Processing Society identifies video as one of the primary domains where digital signal processing finds application, alongside audio and communications.

Capture and Sensing

The front end of any video system is an image sensor that converts incoming light into electrical signals. Two sensor families dominate: charge-coupled devices (CCDs) and complementary metal-oxide-semiconductor (CMOS) active pixel sensors. CMOS sensors, described in detail in foundational IEEE research on camera-on-a-chip technology, offer integration of on-chip circuitry, lower power consumption, and lower manufacturing cost than CCDs, which drove their adoption in smartphones, security cameras, and broadcast cameras. Lenses, color filter arrays, and analog-to-digital converters complete the capture chain, converting optical input into a stream of quantized pixel values.

Representation and Formats

Digital video is represented using color models, most commonly YCbCr, which separates luminance (Y) from two chrominance components. This separation allows the chrominance channels to be sampled at lower resolution, a technique called chroma subsampling (typically 4:2:0), which reduces data volume by roughly half without a perceptible drop in quality for most viewers. Resolution standards range from standard definition (480 lines) through high definition (720p and 1080i/p) to ultra-high definition (4K and 8K). Frame rates, bit depth, dynamic range (SDR versus HDR), and color gamut collectively define the quality envelope of a video stream, and the choice of parameters depends on the intended delivery medium, from broadcast television to streaming to cinema production.

Processing and Compression

Raw uncompressed video generates enormous data volumes: a single second of 4K video at 30 fps, 10-bit depth, and 4:2:2 chroma sampling requires roughly 3 gigabytes before compression. Practical storage and transmission rely on video compression, which removes spatial redundancy within a frame using transforms such as the discrete cosine transform (DCT), and temporal redundancy between frames using motion estimation and compensation. The MPEG and ITU-T standards bodies have produced the dominant compression families: MPEG-2 for broadcast, H.264/AVC for streaming and web delivery, H.265/HEVC for 4K content, and the royalty-free AV1 codec. A coding efficiency comparison of AV1, H.265, and H.264 encoders published in IEEE conference proceedings shows that AV1 achieves roughly 30 to 50 percent better compression than H.265 at equivalent perceptual quality. Encoding, transcoding between formats, and adaptive bitrate streaming for network-variable connections all fall under video processing.

Applications

Video has applications in a wide range of disciplines, including:

• Broadcast television and cable systems
• Video conferencing and remote collaboration
• Streaming media platforms and internet video
• Medical imaging, including endoscopy and surgical guidance
• Security and surveillance systems
• Autonomous vehicles and machine vision
• Scientific visualization and remote sensing