The light around the projection screen is Ambilight
Trapezoid Player is a free video player for Windows and Android. You mark the four corners of the screen cloth. The video plays inside that trapezoid. Light that misses the cloth becomes Ambilight on the wall, in the colors of the same frame, with no black rim where the cloth meets the wall.
- Price
- Free
- Systems
- Windows and Android, including Android TV boxes
- Input
- A video file you choose when the film starts
- Picture
- Perspective-mapped onto the four corners of the cloth
- Wall
- Ambilight sampled from that same frame
- Contact
- chiryasov@outlook.com
Download for WindowsDownload for Android
What Ambilight is
Ambilight is light around the screen that follows the picture. A projector already throws that light onto the wall past the cloth. Trapezoid Player turns it into Ambilight from the film you are watching, instead of a hard edge or a black margin.
A projector always throws a rectangle
The screen cloth is smaller than that rectangle. If the projector is even slightly off axis, the cloth is a trapezoid inside the throw. The bands of light that miss the cloth hit the wall and stay there for the whole film. Keystone correction in the projector menu squeezes the picture until it fits and throws the rest away. Trapezoid Player keeps that spill and makes it Ambilight in the color of the film.
Four corners, then playback
Mark the cloth in this order: top left, top right, bottom right, bottom left. A homography maps the video rectangle onto those four points. Play, pause, and the seek bar sit inside the same shape, so the controls land on the cloth and the Ambilight on the wall stays clear. The seam is the same color on both sides: Ambilight is built from real edge pixels of the current frame, not from a black margin blurred into the picture.
The Windows build and the Android build do the same job from the seat in front of the screen. The engines differ. Read how the mapping and the glow are built, then the steps for Windows or Android and a TV remote.
Ambilight in Trapezoid Player
These pictures show Trapezoid Player: the video on the cloth, the four corners, Ambilight on the wall, and the controls that stay on the screen.
Download
Trapezoid Player is free for Windows and for Android. The Windows file is a zip. The Android file is an APK. Questions are on the FAQ. You can also write to chiryasov@outlook.com.