Now, if you have a computer to the city word hear MP4, is able to play the video format of the concept of multi-media player, and not be able to play the MP4 AAC audio player. This is not a strange phenomenon is no reason for the above mentioned AAC copyright protection, which is many record company to support AAC reasons, to make their players to support AAC, support the need to pay royalties for certain patents or Fee, and, AAC is also a source of the problem, wholesale mp4 is not so open, very few sources of on-line, so the current MP4 audio player development is not yet mature, in view of the status quo, many businesses simply "another body", equivalent MP4 to MPEG-4 Abbreviations such, this also happens to be the MP4 is the next generation of MP3 this law, in addition to having the support of the MP3 music player functions, but also have a powerful MPEG-4 video playback capability.