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overlay-lyrics

Single-page HTML app which uses the OpenLP API to continuously display song lyrics. We use this app within OBS Studio to overlay song lyrics onto our church livestream.

demo2.mp4

This app displays the lyrics on a webpage with a plain background, which OBS automatically makes transparent. Any backgrounds configured within OpenLP for the house display are ignored.

Setup

  1. Download the app and save it onto the machine running OBS
  2. Edit the app code to point to your OpenLP server (edit the openLPHost constant on line 87)
  3. In your OBS scene, add a Browser source, selecting the Local File option
  4. Start OpenLP and display some song lyrics
  5. The song lyrics will be visible in the OBS scene

Display Logic

The app contains some smarts to help figure out the best font size to use when displaying each song. The default font size is 4vw, but if, at that size, any line of the song is wider than the screen, the font size of the entire song is reduced in 0.1vw steps until all lines of the song fit the screen.

Many songs in our database include meta information about the song on slides tagged with a verse type of Intro or Other. Slides containing meta information are rendered in a smaller font size (1.2vw) and are excluded when performing the width calculation described in the previous paragraph. The app identifies meta slides as those:

  • with a verse type of Intro or Other, and
  • which contain any of the following strings:
    • ©
    • ccli
    • lyrics
    • music
    • publish

Connectivity Logic

OpenLP provides real-time status updates via a WebSocket connection. Every operation within OpenLP triggers a message over this connection; although each message contains very limited information. However, receipt of these messages is a useful trigger to request more detailed information from OpenLP.

Whenever the app receives a message via the WebSocket, it calls the /controller/live-items endpoint of the OpenLP API. This endpoint responds with detailed information on the currently-displayed item.

If the WebSocket connection cannot be established, a small orange dot appears in the lower right corner to alert the operator that there is no connection to OpenLP. The operator can click this orange dot to see error details. This orange dot will also appear if the connection is terminated, or if a fetch request generates an error or times out.

Following a connection failure or fetch error, the app will automatically continue attempting to connect, reconnect or refetch at a rate of once every 5 seconds. As soon as connectivity is established, re-established or the fetch succeeds, the orange dot disappears.