PipBlack

Reduce your light emission by watching videos in picture-in-picture mode with a pure black background. Your partner doesn't like to much light but you need your videos when trying to sleep?  This is the compromise you are looking for.

Note: This app does not provide any videos of its own. It is only intended to be used as background for Picture-in-Picture of other apps.

The app will show the current time and lets you set a sleep timer that stops any running media.