Video

Video is an electronic medium that captures, stores, plays back, transmits, and displays moving images, either with or without sound. It began as a live-only technology, later expanding to include recording and storage using analog methods like magnetic tape. By the late 1900s, digital video had become the standard, allowing for efficient compression, storage, editing, and distribution through broadcast television, physical media, and online platforms.

The term *video* comes from the Latin word for "I see," derived from *videre*, meaning "to see."

Video evolved from mid-19th-century facsimile systems. Mechanical scanners, such as the Nipkow disk, were patented as early as 1884, but practical systems took decades to develop. Unlike film, which uses visible photographic images, video encodes images electronically into analog or digital signals. Early video was exclusively live, first used in mechanical television, which was quickly replaced by cathode-ray tube (CRT) systems. Live cameras used an electron beam to scan a photoconductive plate, producing a voltage signal proportional to image brightness. This signal was sent to televisions, where another beam displayed the image. Charles Ginsburg led an Ampex team to create one of the first practical video tape recorders (VTRs). In 1951, the first VTR captured live images by writing the camera's electrical signal onto magnetic tape. VTRs cost around $50,000 in 1956, with tape reels at $300 each, but prices dropped over time. In 1971, Sony introduced consumer videocassette recorders (VCRs) and tapes.

Digital video offers higher quality and eventually lower cost than analog. After the DVD launched in 1997 and Blu-ray in 2006, videotape sales declined. Advances in computing allow inexpensive personal computers and smartphones to capture, store, edit, and transmit digital video, reducing production costs and enabling tapeless workflows. Digital broadcasting and the transition to digital television have made analog video a legacy technology in most regions. High-resolution cameras with improved dynamic range and color gamuts, along with high-dynamic-range digital intermediate formats, have brought digital video closer to film. Since 2013, digital cameras have surpassed film cameras in Hollywood.

Video systems vary in display resolution, aspect ratio, refresh rate, color reproduction, and other qualities. Both analog and digital video can be carried on media such as radio, magnetic tape, optical discs, computer files, and network streaming.

Frame rate—the number of still images per second—ranges from 6 or 8 fps in older mechanical cameras to 120 fps or more in professional models. PAL and SECAM use 25 fps, while NTSC uses 29.97 fps. Film is shot at 24 fps, complicating transfers to video. The minimum frame rate for persistence of vision (the illusion of motion) is about 16 fps.

Video can be interlaced or progressive. Progressive scan updates all scan lines in sequence each refresh period, providing optimal spatial resolution for both stationary and moving parts. Interlacing was invented to reduce flicker in early displays without increasing full frames per second, retaining detail with lower bandwidth. In interlaced video, each frame's horizontal scan lines are split into two fields: an odd field (odd-numbered lines) and an even field (even-numbered lines). Analog displays reproduce each field, effectively doubling the perceived frame rate and reducing flicker. When fields are captured sequentially rather than from a full frame, motion appears smoother on interlaced CRT displays. NTSC, PAL, and SECAM are interlaced formats; in resolution notation, 'i' indicates interlacing (e.g., 576i50 means 576 scan lines, interlaced, 50 fields per second). Displaying an interlaced signal on a progressive device reduces overall spatial resolution.