The display at the bottom left of the above image is what appears on the secondary display (it does not show up on the main app window - I've added this as an overlay to show the output you will see on a secondary screen). You can test this secondary display if you've enabled developer options on your device. Look under the developer options for 'simulate secondary display'.
The app looks for connected display devices via HDMI, Miracast or Chromecast (using cast screen). It also requires Android 4.2 or higher.
The purple buttons at the bottom middle allow you to select parts of your song. The app splits the songs into sections using OpenSong tags. Selecting a button preloads it to the text box at the top middle. Here you can temporarily edit anything before sending it to the projector screen using the 'Project' button. Useful if you spot a typo!
If you have loaded a set, the items will show as red buttons on the left. You can still navigate through the set using the arrow buttons at the top or using the pull out menu on the right. Songs can also be freely selected using the pull out song menu on the left.
Other buttons allow you to blank the screen, show a logo, change the presentation margins or change the backgrounds. The logo used is called ost_logo.png and is found in your OpenSong/Backgrounds folder. You can replace this with your own church logo if you want. These settings are available using the 'Connected display' action button once the display is connected.
Video backgrounds do work, but avoid them if you're presenting wirelessly using Miracast or Chromecast as they are a little slow. There is also a short delay between loops depending on your device's processor. The bundled ost_bg.png image is the preferred background (minimum graphic load and a dark background).
You can select any suitable picture or video as a background. The app looks for suitable files in your OpenSong/Backgrounds folder. If you can't choose a file you know is there, it is likely a non supported filetype. Images should be PNG, JPG or GIF. Videos should be MP4, MPG, MOV, AVI. The toggle buttons switch backgrounds on. If you change a background you need to press its toggle button again to use it.