# How does a video wall show one picture across displays?

A video wall combines several displays into one shared surface: a shop-window band made of two displays, a wall made of four. How the picture is spread across it, and which three limits count before you build.

> **Type:** concept
> **For:** anyone who is planning a video wall or wants to understand why a display in it reacts differently than on its own
> **Prerequisite:** none
> **Where in the portal:** **Video walls**

## The calculation is reversed

Without a video wall, each display fits the scene into its own panel. Two displays with the same assignment therefore show the same picture twice. The displays of a video wall are called its members, and a different rule applies to them: The scene is fitted into the shared surface, and each display shows only its section of it. Four displays then show one picture, not the same picture four times.

The surface is built from an even grid of columns and rows. Each tile counts as 1920 × 1080 pixels, so 2 × 1 tiles make 3840 × 1080 pixels. You decide which display occupies which tile when you create the video wall. The members do not have to be attached to the same device — the surface is built in the portal, not at the cable.

![A scene is fitted into the shared surface of a video wall. The left display shows the left half, the right display the right half, and a display without a video wall shows the whole scene.](/docs/displays/bilder/ff8aa8dc-video-wall-crop.svg)

*On the video wall, each display shows its section of the shared scene. On its own, it shows the whole scene.*

Assignments go to the video wall, not to the individual display: A program, scene, playlist, or media item lands on all members in one go. On the member itself, the assignment is locked. There it says **Part of a video wall** with the name of the surface and the **Go to the video wall** link.

## Content for very wide surfaces

A scene for a 16:9 panel does not fit a surface of 4 × 1 tiles. The template gallery under **Scenes** therefore has a **Video wall** format for aspect ratios from about 21:9 up. Such templates do not appear under **Landscape**: Their layout makes no sense on an ordinary panel.

## Three limits you should know

**Synchronization is clock synchronization, not frame synchronization.** All members calculate the same timeline and switch the program entry at the same time. It is not guaranteed that two displays show a video frame-accurately next to each other. There is no synchronization across devices. For still images, scenes, and calm transitions, this is enough, but for video across the seam it is not.

**Video plays on video walls through the browser.** The accelerated video path does not know about the section and would show the whole picture on every member. The device therefore switches to playback in the browser. That costs performance: Very large videos on a 4 × 4 wall are not a good idea.

**The clocks must be right.** The devices get their time from the network. A wrong clock switches at a different moment than its neighbors. The portal reports this as **Clock out of sync**: “The device clock runs without synchronization. Schedules will switch at the wrong moment.”

## What follows

- Plan a video wall for scenes, still images, and calm transitions. A video across the seam will not be frame-accurate.
- Keep videos small on large grids: The more tiles, the more each device calculates in the browser.
- Design content in the **Video wall** format as soon as the surface is wider than about 21:9.
- Make sure every device gets its time from the network: **Clock out of sync** on one member affects the whole surface.
- A display belongs to at most one video wall. To use it differently, dissolve the wall or rebuild it.

## Related

- [Create a video wall, assign content, and dissolve it](/docs/displays/create-video-wall): grid, assignment, dissolving.
- [Which format does a scene need for which display?](/docs/content/about-scene-formats): the **Video wall** format.
- [Connect to the network: cable, Wi-Fi, company network, time](/docs/devices/connect-network): where a device gets the time.