A device or software that combines many video sources into a single composite output for monitoring on one screen — historically a broadcast tool, now common in NOCs and AV.
What it is
A multiviewer takes multiple incoming video streams and renders them as a tiled composite on a single display output. Tile layout is configurable; tally borders, audio meters, source labels, and timecode are usually overlaid per tile.
How it differs from a video wall
A multiviewer outputs one physical screen with multiple source windows on it. A video wall spans many physical screens treated as one canvas. They overlap conceptually: modern software video-wall platforms are multiviewers that happen to drive an array of displays instead of a single one.
Why it matters
Multiviewers compress operator attention. Watching one labelled, audio-metered tile of 16 cameras is far more efficient than cycling through 16 separate windows. Combined with NDI input, the sources can come from anywhere on the network — no SDI cabling required.