[CentOS] recommended methods/software for videocasting

An acquaintance is considering videocasting speakers at a conference and using a Twitter product called Periscope. I'd like to recommend an open source solution. While I've never offered videos over the web, I have made audios available, and all it entailed was placing the file on the website and putting its url on a visible webpage. I wouldn't think any more than that is required for video. True?

"Live" videocasting is likely a different animal. How is this accomplished?

Also, which video formats are recommended-- FOSS of course preferred, but a FOSS format for which there are readily available client apps on the major platforms (MS, Android, OSX, Linux).

Thanks for your expertise.