The RM file format is used by RealMedia. This is a multimedia player created by RealNetworks Inc. It is used by both RealVideo and RealAudo and is popular for streaming video and audio over the internet.
Mime type: application/vnd.rn-realmedia, audio/vnd.rn-realaudio, audio/x-pn-realaudio, audio/x-realaudio, audio/x-pm-realaudio-plugin