Compose the wall's video at the wall's real canvas, gaps included: 10,554 × 3840 in the worked example. Export one file at that size if the player accepts the canvas; otherwise cut the same master into one 2160 × 3840 file per panel. A single scaled 4K file stretches 1.55:1, drifts a full gap off the glass from panel 2 onward, and softens every text edge.
A video wall should be fed at its true pixel size: every panel's pixels plus every gap between them, counted in the panel's own pixel unit. For the four-panel wall used as this page's example, that canvas is 10,554 × 3840. Export one file at that size if the player's spec lists the full canvas. If it caps the canvas at one screen's format, cut the same master into one file per panel, each at the panel's native 2160 × 3840. The third path, a single 3840 × 2160 file that the processor scales up, is the one to refuse: the picture sits one full gap off the glass from the second panel onward, and text edges smear across 2 to 3 panel pixels.
Every number behind those claims is worked out below. If you are planning the wall itself first, the digital menu board guide covers sizing and layout from the viewing distance up.
What the wall's canvas really is
A wall's canvas is not the total of its screen resolutions. It is the total of the screens plus every gap, measured in the same pixels. Four portrait 4K panels contribute 4 × 2160 = 8640 pixels of width. Gaps of 638 pixels add 3 × 638 = 1914 more, so the canvas is 8640 + 1914 = 10,554 pixels wide and 3840 tall. Canvas columns 2160 to 2797, 4958 to 5595 and 7756 to 8393 fall on the mullions; nothing placed there is ever shown. Everything else has to land on glass, one source pixel per panel pixel, for type to stay sharp and for anything drawn against a panel edge to stay on that edge.
The panel's pixel pitch turns the gap into hardware. A 50-inch 16:9 4K panel spreads 3840 pixels across 43.6 inches of glass, 0.29 mm per pixel, so a 638-pixel gap is about 184 mm of mullion.
The three ways to feed a wall
| One file at wall size | One file per screen | One 4K file, scaled | |
|---|---|---|---|
| What the player gets | One file at 10,554 × 3840, black in the gap columns | Four files, each 2160 × 3840 | One file at 3840 × 2160 |
| File-to-glass scale | 1:1 | 1:1 | 1.78× to match height, then 1.55× more to fill width |
| Gap alignment | Exact, gaps drawn into the master | Exact, each crop starts at its own panel | One full gap off: 638 px on panel 2, 1276 on panel 3, 1914 on panel 4 |
| Text and lines | Rendered once at final size | Rendered once at final size | Edges spread over 2 to 3 panel pixels |
| H.264 budget at 30 fps | 4,752,000 macroblocks/s, 2.3× over Level 5.2 | 972,000 macroblocks/s per file, inside Level 5.1 | 972,000 macroblocks/s, inside budget |
| Needs from the hardware | A spec that lists the whole canvas | One addressable file per output | Nothing special, which is why it gets tried |
Example: canvas size and per-screen crops
The wall: four 50-inch 4K panels, portrait, one row, 184 mm mullions between them, which is 638 pixels at the panel's 0.29 mm pitch. Work in pixels from the start.
- Canvas width: 4 × 2160 + 3 × 638 = 8640 + 1914 = 10,554. Height 3840. Canvas: 10,554 × 3840.
- Cross-check with the three-panel layout: 3 × 2160 + 2 × 638 = 6480 + 1276 = 7756. One gap value, two canvases, both out of the same drawing. If your two numbers disagree, a measurement or the pitch is wrong.
- Build the master at 10,554 × 3840, with black rectangles 638 pixels wide starting at columns 2160, 4958 and 7756.
- Crop one file per panel:
| Panel | Canvas columns | File size |
|---|---|---|
| 1 | 0 to 2159 | 2160 × 3840 |
| 2 | 2798 to 4957 | 2160 × 3840 |
| 3 | 5596 to 7755 | 2160 × 3840 |
| 4 | 8394 to 10,553 | 2160 × 3840 |
Each crop is the panel's native pixel count, so no scaler sits between file and glass anywhere in the chain.
- One file for the whole wall runs into the codec first. H.264 spends its budget in macroblocks, blocks of 16 × 16 pixels. The 10,554-wide frame pads to 10,560, giving 660 × 240 = 158,400 macroblocks per frame; at 30 frames a second that is 4,752,000 macroblocks per second. The highest level H.264 defines, Level 5.2, allows 2,073,600, so the file sits 2.3 times over the ceiling, and still 1.8 times over at 24 frames (158,400 × 24 = 3,801,600). No H.264 level covers it, so a compliant decoder is never required to play it. Each per-panel crop is a different story: 2160 × 3840 is 32,400 macroblocks per frame, exactly a 4K frame's budget, and 30 frames a second runs at 972,000, inside Level 5.1's 983,040.
What the scaled file does to the picture
Start from a finished 3840 × 2160 file. Matching the wall's height takes 3840 / 2160 = 1.78×, which lands the file at 6827 pixels wide; the canvas is 10,554, so filling the width needs another 10,554 / 6827 = 1.55× horizontally. Everything on screen ends up 55 percent wider than it was shot.
Alignment breaks at the gaps. If the wall software keeps its natural gapless canvas of 8640 × 3840 and maps it 1:1 from panel 1, content drawn for panel 2 sits at column 2160 while panel 2's glass starts at column 2798: 638 pixels of drift, one full gap. It grows to 1276 pixels on panel 3 and 1914 on panel 4, so separator lines and per-panel framing miss the glass. A scale-to-fit that stretches the gapless canvas over all 10,554 columns, factor 10,554 / 8640 = 1.22, misses panel 2's edge by about 160 pixels and panel 4's by about 479.
Sharpness goes the same way. Interpolation spreads a 1-pixel edge over 1.78 pixels, so every hard edge covers 2 panel pixels vertically and up to 3 horizontally: a 0.3 mm edge becomes a 0.6 to 0.9 mm soft band. The eye resolves about 1 arcminute, the usual figure for normal vision, and 0.87 mm of blur reaches that limit at 3 m. Footage watched from 3 m or farther hides the scaling; type read from closer shows it on every letter.
Where each export wins
One file at wall size when motion runs unbroken across the gaps, the master is one composition, and the player's spec lists the whole canvas plus a format that can carry it. One file, one timeline, gaps exactly where the mullions stand.
One file per screen when the wall software caps its zone at one output's format, which is the common case; the video wall resolution limit and the 4K canvas fix covers that cap and the canvas arithmetic around it. It is also the answer whenever the screens may later show different content, because each output keeps its own file, and it is the only answer for menu boards, where every line of type must sit on the pixel grid. The per-output pixel budget behind this is the same one that makes six screens on one player drop to HD each, worked through in why a six-screen video wall drops to HD per screen.
One 4K file, scaled only for camera footage: no text, no logos, nothing geometric tied to panel edges, and viewers 3 m or farther away. It is the fallback for footage-only walls and the wrong tool anywhere type appears.
Menu boards and smaller walls
A one-row wall is the standard big menu board layout, and menu boards make the choice simple: type has to land on the pixel grid, so the scaled file is out, and the whole-canvas file or the per-screen crops win. The layout side, dividing one canvas across four screens with the gaps in mind, is covered in laying out one menu board canvas across four screens.
The same export rule scales down. Our menu-board displays mount portrait or landscape and play offline from a card with no software subscription, one file per screen, so each card carries its own file at that screen's native size. To turn slide content into those files, exporting slides to video for an offline signage player walks through the conversion.
How to check a player before you build the master
- Largest canvas. The wall software's spec or zone editor states the biggest single composition it builds. If it lists your full canvas including gap columns, the single file is possible. If it only builds panel-native multiples such as 8640 × 3840 for four portrait 4K panels, there is no bezel compensation: crop per screen.
- Decoder list. A player limited to standard H.264 cannot carry a moving file at this wall's canvas, by the example's budget math, so its single-file path means the still formats the spec lists, or per-screen crops.
- Per-output files. If each output can be pointed at its own file, per-screen crops work regardless of the canvas cap.
- Gap arithmetic. Recompute every canvas from one measured gap value, as the example does with 638 pixels across the three- and four-panel layouts. Numbers that disagree point at a wrong measurement or the wrong pitch.
Pick the tool last: any compositor that sets a custom canvas size and crops exports to order produces both the master and the per-panel files.
The decision
Recommendation: Compose one master at the wall's true canvas, 10,554 × 3840 in the example, black exactly where the gaps fall. If the player's spec lists that canvas and a format that carries it, export the master whole and hand it over. If the zone editor caps the canvas at one output's format, crop the same master into four portrait files of 2160 × 3840 using the column table, one file per output, all cut from one timeline so the frames stay in step. Refuse the scaled single file for anything with text or panel-aligned geometry; allow it only for camera footage watched from 3 m or farther.
Questions
Does the same method apply to a 2x2 wall?
Yes, one axis at a time. Four landscape 4K panels in a 2x2 with a 100-pixel gap give 2 × 3840 + 100 = 7780 pixels wide and 2 × 2160 + 100 = 4420 pixels tall. Draw black where the vertical and horizontal gaps fall, or crop each panel its own 3840 × 2160 file. Only the arithmetic changes; the decision stays the same.
How do the four per-screen files stay in step?
Crop all of them from one master timeline at the same frame rate and length, so frame 100 of each file is the same moment, and start them from one group command. A screen that starts 100 ms late at 30 frames a second sits 3 frames behind, and the mismatch shows as a tear on anything crossing the gap.
What resolution should the camera footage be?
No camera records 10,554 pixels wide, so footage gets scaled at least once no matter what; 4K is a sensible master for it. Text, logos and flat graphics are different: draw them as vectors at the wall canvas so they render once at final size and never pass through a scaler.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.