Stream will start playing automatically when it is live
Live Stream using OBS Studio
OBS Studio is the most popular streaming software in the world and is what most people use
to stream to Twitch or YouTube.
Download it from - https://obsproject.com/
and then before streaming, go to your stream settings, and provide server/key values below:
Live Stream local file with FFmpeg
Just replace "./video.mp4" with path to that video file.
ffmpeg -re -i "./video.mp4" -c:v libx264 -c:a aac -b:a 128k -ar 44100 -ac 2 -preset veryfast -f flv