AVCHD (Advanced Video Coding High Definition) is a file-based format for the digital recording and playback of high-definition video. Developed jointly by Sony and Panasonic, the format was introduced in 2006 primarily for use in high definition consumer camcorders.
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.