Position and time an image/video overlay over a background clip, optionally constrain it with a matte, then render a new video.
Where: Flowgen → Add → Video & Motion → AI Edit → Video Alpha Over.
Before you start
- Connect a background video and a top image/video layer.
- Connect a matte only when the composite needs a mask.
Key ideas
- Layer roles are explicit: video_in is the background, overlay_in is the top layer, and mask_in optionally supplies a matte. video_out emits the rendered composite.
- Placement and timing are separate: X/Y, scale, and rotation position the overlay; Overlay Start places it in time; Trim In/Out choose the overlay range.
- This is a render operation: The node renders a flattened video result. Use Video Editor/Video Composition instead when you need a fully editable multi-layer timeline afterward.
- Video Alpha Over card: VideoAlphaOverNode uses the authored shared-card path. Composite a connected video background with an image/video layer and optional matte, then render the result as a video.
- Properties sidebar: Common properties source controls
- Opened surfaces: Video preview/player
Steps
- Connect a background clip to Background and the foreground image or video layer to Overlay.
- Optionally connect a matte to Matte when only part of the overlay should contribute.
- Set X and Y position, scale, and rotation on the card. Use Reset to return those placement values to their defaults.
- Set Overlay Start and Trim In/Trim Out so the overlay appears for the intended interval. Leave Trim Out blank to keep the full available overlay range.
- Check the video preview and compare the overlay alignment at its start and end. The card’s fields control placement and timing; the common properties shell exposes source connections.
- Choose Render and wait for the video output. Connect video_out to another video operation or the final delivery stage.
Visible controls
- Background video, Top layer, and optional Matte sockets.
- X % and Y % position, Scale, Rotate, Start, Trim in, and Trim out fields.
- Reset restores X, Y, scale, and rotation; it does not replace or reconnect source media.
- The card previews the source/result and displays render errors. Render is unavailable until the required background and overlay sources are ready.
Matte and layer behavior
- A matte controls the overlay contribution; it is not a replacement background.
- An image overlay behaves as a still layer over the background duration; a video overlay also has its own start and trim range.
- Keep source clips upstream so the graph shows provenance and a later edit can swap the background, overlay, or matte independently.
Video Alpha Over controls and presets
- Add path: Flowgen → Add → Video & Motion → AI Edit → Video Alpha Over.
- Card: VideoAlphaOverNode.
- Properties: Common properties source controls.
- Controls: Background video; top image/video layer; optional matte; X/Y position; scale; rotation; overlay start; trim in/out; reset; render.
- Opened surfaces: Video preview/player.
Tips
- Use small placement changes and inspect the preview before rendering the full clip.
- If the overlay begins late, adjust Overlay Start; if its source content begins at the wrong moment, adjust Trim In.
Limitations and important notes
- The output is a rendered/flattened video, not an editable compositor project.
- A matte is optional and only affects the overlay layer.
- The node does not offer a dedicated editor window; work from the node card and shared source controls.
Troubleshooting
Render is disabled.
Connect both the background video and top layer, and wait for their media to load.
The overlay is visible at the wrong time.
Check Overlay Start separately from Trim In/Trim Out; they describe timeline placement and source range, respectively.
The overlay covers too much of the frame.
Adjust position/scale or connect a matte that defines the overlay area.