I have a source video. In order to play it in all major browsers (IE7+, Chrome, Safari, Firefox), how many formats do I need to convert the video to? Will using a single .mp4 file be sufficient? What exactly is the webm format, and is it required that I additionally convert my video to this?
In addition, what are some open source video players that would be able to play this format(s) in all browsers?
flowplayer is the opensource player which is easy to integerate in your website. It can play formats like flv and mp4 in all browsers.
here is a link to it:
http://flowplayer.org/
Another opensource player is JW Player. you can find it here:
http://www.longtailvideo.com/players/
Hope this helps.