NDI video output (Pro)

NDI® video output sends the song's video over the network to an LED processor or media server. You cut the video into slices, place and rotate them on an output canvas — the layout the receiver expects — and LTCast sends the result as an NDI source, in step with the timecode. It has been tested with Depence R4 as the receiver. NDI is a network video standard from Vizrt NDI AB (ndi.video). For a step-by-step version with pictures, see Send the show video to an LED wall over NDI.

What it needs

• A Pro licence or an active trial — starting NDI video output needs Pro.
• Nothing to install: LTCast includes the NDI® library (ndi.video) on both Windows and Mac.
• The receiver on the same network. On a Mac, the first time you start sending, macOS asks whether LTCast may use the local network — click Allow, or no other computer can receive it. System Settings lists it as LTCast Helper.
• A video on the song (File → Import Video). A song without video sends black.

Opening the editor

Choose View → NDI output, or click the pencil on the NDI pill in the status bar. The editor is its own window, so it can sit on a second screen next to the receiver's picture. Closing it does not stop sending.

Outputs

The top row of the editor is the output. Add output creates one; its name is the NDI source name, which receivers list as COMPUTER (name). Start output and Stop output switch it on and off, and the status next to them says what is really happening — Sending with the number of receivers connected, or an error in red (hover it for the reason).

The second row is the picture. Canvas sets the output size and frame rate; match them to what the receiver expects. Applying a new size restarts the NDI source, which receivers handle better than a silent resize.

Slices

A slice takes a rectangle of the video and puts it somewhere on the canvas. Add slice, then:

• In INPUT, drag the slice over the part of the video it should take.
• In OUTPUT, drag it to where it lands. Corner and edge points resize it; the round grip rotates it to any angle.
• Select several the way Resolume Arena's Advanced Output does: drag across empty space to select every slice the box touches, Shift+click to add or remove one, Ctrl+A for all and Esc to clear. Dragging one of them moves them all, and the handles of the box around them resize them all.
• With slices selected: Rotation takes an exact angle, Flip horizontal and Flip vertical mirror them, Fill output stretches them over the whole canvas, and Duplicate (Ctrl+D) copies them. The arrow keys nudge them by one pixel, ten with Shift; Delete removes them.
• Right-click a slice for Arena's commands: Match Input / Output Shape, Swap Input / Output Shape, Center, Mirror, Fill (the whole area or a half), flips and rotation, Bring Forward / Send Backward, Duplicate, Copy / Paste (between outputs too), Hide and Delete. Select slice underneath reaches a slice that another one covers.
• Pan with the middle mouse button, or hold Space and drag — over a slice too; it never moves one. The wheel zooms at the pointer. On a Mac, two fingers on the trackpad pan and a pinch or ⌘ + scroll zooms, and the shortcuts use ⌘ where this page says Ctrl.
• Every change can be undone: Undo and Redo sit at the end of the second toolbar row (Ctrl+Z / Ctrl+Y). Starting or stopping the output is left out, so an undo never takes a live output down.
• The slice list below shows every slice's input and output rectangle as numbers you can type. The eye switches a slice off without deleting it; the bin deletes it.
• Snap pulls edges to the canvas, its centre and other slices while you drag.
• Reference lays a picture — typically the LED pixel map — under the output preview to line slices up against. It stays in the editor and is never sent.

Slices are drawn in list order, so a later slice covers an earlier one where they overlap. What the output preview shows is, pixel for pixel, what the receiver gets. The layout is saved in the show file.

Test pattern

Test pattern sends a calibration picture instead of the show: every slice outlined, numbered and named, a moving line, the timecode, and a square that flashes white on every whole second of timecode. The editor preview has the same square, flashing on the same seconds without any network in between — so with the receiver's picture beside the editor, you can see at once whether the two agree. The NDI pill in the status bar turns into a loud test pattern warning while it is on, so it cannot be left running into a show by accident.

Send early

Every receiver needs a moment to decode and show a frame. LTCast already allows for its own processing; Send early (in milliseconds) covers the receiver's part. Turn on the test pattern and raise it until the receiver's square flashes together with the editor's. It applies at once and can be changed during the show.

During the show

• Slices can be adjusted while the show plays or chases, against the picture as it runs. Send early can be changed too.
• Changing songs does not drop the NDI source — the receiver keeps the same source for the whole show.
• Past the end of a song's video, the last frame is held.