The Advanced Authoring Format (AAF) is a professional file interchange format designed for the video post-production and authoring environment. It was created by the Advanced Media Workflow Association. The AMWA develops specifications and technologies to facilitate the deployment and operation of efficient media workflows, working closely with standards bodies like the SMPTE.
this is a lossless-format (and encoding algorithm) for Apple platforms. M4A is widely used in iPod players and as a component in QuickTime media-players. The m4a codecs decoder is found in open sources - this allows third party users to open files in that format.