How to add text over video when playing a video stream from local source?

Question

I want to develop an android app that can control custom(user) text added over a streaming video.

1. say when the user plays a 3 min video, suppose he pauses exactly at 1 min to add or include his text(subtitle or some info), then saves it.
2. Now the video should continue streaming (original video without the text added, from min 1 onwards) till the end of the video.
3. Then when the user replays the video it should incorporate the text added from min 1 onwards overwritting the original video.