This screencast shows how video or audio can be added in MediaCore.
MediaCore supports a wide range of formats including (but not limited to): YouTube, Vimeo, Amazon S3, Bits on the Run, BrightCove, Kaltura, and either your own server or someone else's.
Videos can be uploaded in any format, but can only be published in web-ready formats such as FLV, MP3, M4V, MP4 etc.