AAC is a file format for storing music or other sounds. It stands for Advanced Audio Coding or Advanced Audio Codec. It is used by Apple Inc. in the iPod and iTunes. AAC is one of the standard formats that comes from the MPEG organization, the same people who invented MP3.
There are several flavors of AAC. These are the most popular:
- AAC LC–the format used by Apple software; it takes up more space and is used for music stored on an iPod, CD-ROM, or disk drive.
- HE-AAC v1–a more efficient format; it saves space for music sent over a network, like over the Internet or to a cell phone. Brand names for this format include aacPlus™, Nero Digital™, and AAC+.
- HE-AAC v2–an even more efficient format for music sent over a network. Brand names for this format include aacPlus™ v2, eAAC+™, and AAC+ Enhanced™.
File names [change]
Here are some common AAC file name endings:
- .aac–music only
- .m4a–music and information
- .m4p–music and information, with DRM
- .m4b-speech and information, "Audiobook" recognized by Apple that keeps the listener's position
- .m4r-music and information used by Apple as a ringtone
- .mp4–music, video, or both, plus information.
An AAC file that has only music and information could have a name that ends with either .m4a or .mp4.
A KDE/Qt application for Linux/Unix called easytag will edit metadata about AAC-encoded files as long as they end with the .m4a extension. Typically, renaming files to .m4a and back to the original extension after editing is sufficient. This method can be used to configure typical ID3v2 metadata including cover art. This cover art is used by Apple's iTunes and their media players. Note that easytag does not have the ability to add chapter points into Audiobooks (.m4b).