Signage player output for a large LED billboard canvas

What plays the content on a big LED billboard?

A signage player feeds the billboard's LED controller over HDMI, and the controller, not the player, drives the LEDs: the player's HDMI port is an output. On a typical large board the controller's input mode is 1920 × 1080 at 30 Hz.

That chain has three links. The player makes the picture. The sending controller turns the HDMI frame into LED data. Receiver cards in the cabinets drive the modules themselves. You choose the player for its content features; the cabinet supplier chooses the controller to suit the modules.

The signal runs one way. The input port lives on the controller, and why an HDMI input on a signage player rarely works covers the reverse assumption, which is the usual mix-up. The same chain at indoor scale is described in driving an LED video wall from an Android signage player. The billboard version differs mainly in cable length and weather, which belong to the cabinet builder's scope.

Why must the player's output match the controller's input mode?

Because the controller treats the player as a monitor and maps whatever it receives onto the LED grid: a mode the controller does not list, or 1080p60 fed into a controller set for 1080p30, brings no picture or a squeezed one.

Over the HDMI handshake the controller announces the mode it wants to receive. A player set to follow that handshake lands on the right mode without being told. Both 1920 × 1080 at 30 Hz and 1920 × 1080 at 60 Hz belong to the standard HDMI timing set defined in CEA-861, so a player with a standard mode list normally carries them.

Billboards often run the 30 Hz variant. The content changes slowly, and the lower rate lowers the pixel clock, which is easier on a long cable run out to a pole or a roof.

Two clarifications keep the rest of the job sane. The 30 Hz is the pace frames arrive at the controller, not the pace your slides animate at, and planning signage animation frame rate covers that separate choice. Skipping the match produces exactly the failure you may have seen indoors, slides parked in one corner of the picture, which the fix for a signage screen size mismatch works through on a normal display.

How do you find the billboard's true canvas size in pixels?

Divide the face size by the pixel pitch: a 3.2 m by 3.2 m face at P10, meaning 10 mm between pixel centres, is 3200 ÷ 10 = 320 pixels across, so the design canvas is 320 × 320, about 102,400 pixels.

The pitch is on the cabinet datasheet, and the grid follows from the module layout. The usual P10 module measures 320 mm by 160 mm and carries 32 × 16 pixels. A face of 10 modules across and 20 modules down lands on exactly 320 × 320, the example used below.

Pitch is what moves the number. The same 3.2 m face at P16 gives 3200 ÷ 16 = 200 pixels across, and at P6 gives 533. Fewer pixels per metre means fewer pixels available for every letter, so the pitch decision and the content decision are the same decision.

Ask the supplier for the module count, not just the board size. Boards are built from whole modules, so a face described as about 3 m can come out at 288, 300 or 320 pixels depending on the layout, and the canvas must match the real grid.

Which output mode should you set on the player?

The exact mode listed in the controller's manual for its HDMI input, resolution and refresh together: 1920 × 1080 at 30 Hz is the common billboard setting, and 1920 × 1080 at 60 Hz is the other one you will meet.

If the controller lists a standard mode, any player whose specification includes that standard mode will do. If the controller accepts a custom mode equal to the canvas itself, for example 320 × 320, you need a player whose specification says custom output resolutions. That single line on the spec sheet is worth checking before anything else.

Hold the chain to one scaler. Either the player scales to a standard mode and the controller maps the frame, or the player outputs the canvas natively and nothing scales at all. Two scalers stacked in one chain are how you get soft edges and borders that sit where nobody drew them.

Can you walk through a 10 m² billboard example?

Take a 3.2 m by 3.2 m board, 10.24 m², built from P10 modules, so the canvas is 320 × 320 pixels; the controller reads 1920 × 1080 at 30 Hz, and a driver reading from 100 ft needs capitals of about 13 pixels.

Letter size comes first. The FHWA planning figure for signs is 30 ft of viewing distance per inch of capital letter height, and 20 ft per inch is the safer number for fast reading.

• Minimum capitals at 100 ft: 100 ÷ 30 = 3.33 in, and 3.33 in × 25.4 mm per in = 85 mm. At 10 mm pitch that is 85 ÷ 10 = 8.5, so 9 pixels.
• Comfortable capitals at 100 ft: 100 ÷ 20 = 5 in = 127 mm = 12.7 pixels, so draw 13.
• P10 puts 25.4 ÷ 10 = 2.54 pixels on every inch of face, so a 13 pixel capital stands about 5.1 in tall on the board.

Now feed the board one of two ways.

Full-frame scale. Design at 1920 × 1080 and let the controller scale 1080 lines down to 320, a factor of 1080 ÷ 320 = 3.375. To deliver 13 pixels to the board you draw 13 × 3.375 = 43.9, so capitals live at 44 px or more in the design; the 9 pixel minimum becomes 30 px. The board is square and the frame is 16:9, so hold content inside a centred 1080 × 1080 zone, which leaves 420 px of empty band per side, or shapes distort by the 1.78 ratio between the frame's width and height.

Pixel-to-pixel. The controller windows onto a 320 × 320 region of the input frame, or the player crops its output to that region, or the controller accepts a custom 320 × 320 mode. You draw at 320 × 320 and the 13 pixel capital is 13 pixels, with nothing resampled.

Both numbers move with distance and pitch. Each extra 30 ft of reading distance adds 1 in of capital height at the 30 ft per inch figure, which is 2.54 pixels on this board. A coarser pitch spends fewer pixels on the same letter: the 127 mm capital is 127 ÷ 16 = 8 pixels on P16 and 127 ÷ 6 = 21 pixels on P6.

The decision for this board: photographs and short words in big capitals survive the full-frame scale. Small text, logos and anything with fine detail want the pixel-to-pixel path.

Which content method fits your player and controller?

Three workable methods exist, ranked by how sharp the result is: pixel-to-pixel wins for text and detail, full-frame scaling is fine for photographs and big short words, and a converter box added mid-chain is the last resort.

Check the player specification for the crop or custom mode wording before you buy. A player that lists neither pushes you to the third row, and the third row has the letter-size penalty shown above.

When is a signage player the wrong tool for a billboard?

When the board shows nothing but a clock, a temperature or a queue number, the controller's own scheduling covers it with less to run. A player earns its place once you want designed slides, video and playlists you update yourself.

A player is worth adding once the board carries designed content that changes. Watch the arithmetic of outputs too: one player output carries one picture, so independent content on several boards means one player per board or a controller with extra inputs.

And the honest boundary for our side of the market: nothing in our display range is the screen in this job. An indoor LCD panel is the wrong display for a 10 m² board exposed to weather; the LED cabinets are the display, and the player is only the source. If the real job turns out to be a panel on an indoor wall, that is a viewing distance question, and the screen size and viewing distance guide answers it.

What should you ask for before you buy?

Three answers in writing settle the design before you order anything: the controller's supported input mode list, the board's true pixel grid with its module layout, and the player's output abilities.

From the controller maker:

• The input mode list for the HDMI input, resolution and refresh together, for example 1920 × 1080 at 30 Hz.
• Whether the controller accepts a custom input mode, and whether it can window onto part of the input frame.

From the cabinet supplier:

• Face size, pitch and the module layout, so you can compute the canvas as modules times pixels per module.

From the player maker:

• The standard output mode list, and whether custom output resolutions are supported.
• Whether the output can be cropped, sometimes called overscan, where the output frame is larger than the visible area so the edges are cut away and the chosen region fills the board.
• How updates reach the player, and the hours per day the supplier rates the unit for.

From whoever runs the cable:

• The HDMI run length. Most passive HDMI cables are dependable to about 5 m; past that, active or optical cable is the normal choice, and a controller room to pole run is usually well past it.

A 10 m² LED board is mains powered, built at height and often above a road, so the electrical, structural and installation work belongs to licensed contractors, and the content work on this page starts once that is signed off.

Recommendation: set the player's output to the controller's exact input mode and design every slide at the board's true pixel canvas. On the 320 × 320 board in the example that means a pixel-to-pixel window or a custom 320 × 320 mode, with capitals drawn 13 px tall for a 100 ft read. If the player offers neither output crop nor a custom mode, design full-frame at 1920 × 1080, hold the content inside a centred 1080 × 1080 zone, and keep capitals at 44 px or more so they survive the 3.375× downscale to 320 lines.

Questions