RealPlayer

RealPlayer, by RealNetworks, is a cross-platform software product primarily used for the playing of recorded media. The media player is compatible with numerous formats within the multimedia realm, including MP3, MPEG-4, QuickTime, Windows Media, and multiple versions (proprietary) of RealAudio and RealVideo formats. RealPlayer is also available for other operating systems (OS) and Linux, Unix, Palm OS, Windows Mobile and Symbian versions have been released.

The software is powered by an underlying open source media engine called Helix.

Read more about RealPlayer:  History, Features, Controversies, Access Restrictions, Real Alternative