AAC format is generally a music file, which can be opened by listening to individual mobile phones on a PC. It also supports music in this format, such as Sony Ericsson W series.
Audio MP4 format: AAC
MP4 is an audio format, which has nothing to do with MPEG-4, just as MP3 has nothing to do with MPEG-3. MP3 is the abbreviation of MPEG- 1 Audio Layer 3; MP4 is MPEG-2 AAC, which is a complete audio compression format, adding new functions such as perfect stereo reproduction, multimedia control and noise reduction. Most importantly, MP4 realizes digital copyright protection through special technology, which is incomparable to MP3.
Video MP4 format: MPEG-4
At present, most MP4s on the market prefer multimedia players, but few can play AAC. Some media even described MP4 as the abbreviation of MPEG4-4, which was a fallacy in the past, but this fallacy has become a truth after the constant hype of merchants. Now, if you go to the computer city and hear the word MP4, it is definitely the concept of a multimedia player that can play video format, not a walkman that can play audio MP4 AAC. This strange phenomenon is not without reason. As mentioned above, AAC has copyright protection function, which is why many record companies support AAC. In order to make their players support AAC, they have to support the payment of certain copyright fees or patent fees. In addition, the source of AAC is also a problem, which is not as public as MP3, and there are few online sources. Therefore, the development of audio MP4 player is not mature at present. In view of the above situation, many businesses simply "come back to life". Equating MP4 with the abbreviation of MPEG-4 just corresponds to the law that MP4 is the next generation MP3, which not only supports the music playing function of MP3, but also has powerful MPEG-4 video playing ability. In addition, it makes sense to equate MP4 with MPEG-4 just after "3".
3gp is a mobile phone movie format, which can be played by ordinary mobile phones.