flv.js | HTML5 FLV Player - flv | Video Utils library

You can add text to a video in a number of ways - most common are probably:

• Add a text track to the video container, i.e. the MP4 file. This is usually done server side and the client then uses this info to display it client side. You can see more info here and an example with a commonly used tool: https://www.bento4.com/developers/dash/subtitles/

• Embed the text in the frames themselves - this requires more processing and also adds the text to the video frames themselves, so you can't turn text on and off at the client easily. If you do want to do this then FFMPEG is probably a good place to start.

• Add a text overlay on the client itself - e.g. a text 'div' or element on a browser App, or a TextView on Android etc. You mention that synchronisation may be a problem, but you could take timing events from the video to trigger changing the text. This avoids you having to do any extra processing on the video or video container.

A simple example of using timing to trigger text is below - you would likely want to update it to avoid checking everything on each 'onTimeUpdate' event, and maybe to put the text over the video itself, but this give an example how the basic mechanism works: