All-in-one application from Apple with free AAC/MP4 encoder and decoder from QuickTime, rips CDs, organizes music files and connects to its Music Store.
Since version 6 this Apple multimedia software decodes MP4 files. The basic player is free, the commercial Pro version also encodes MPEG-4 video and AAC as well as 3GP content.
Multimedia player of the VideoLAN project for several platforms, streams live MPEG-4 content via RTP and aacPlus via Shoutcast, transcodes to AAC with FAAC.
Tools to record, convert, stream and play multimedia content including libavcodec and libavformat, two libraries used by many other open source projects.
Integrated music management application inspired by Apple's iTunes and based on the GStreamer and/or the Xine framework, plays AAC/MP4 through gst-plugin for FAAD2.
This multimedia DirectShow player looks like the old Windows Media Player 6.4, but has a lot more features like switching audio streams in an MP4 file.