M4A (MPEG-4 Audio Layer)
The M4A Audio file format
M4A is short for MPEG-4 Part 14 and the file type was created by Apple in 2004 using the QuickTime File Format. The iTunes store runs on M4A file downloads (15 billion files worldwide). It is a digital multimedia container format used to store audio components, but can store other data (e.g. images) as well. MPEG-4 Part 14 files can be saved under the extension M4A and MP4 (the difference being MP4 is capable of storing video). Like most audio file types, there is a lossy compression option and it is accomplished using AAC encoding. Unlike other audio files there is a lossless compression available, which is possible due to the Apple Lossless format.
Technical details of M4A files
M4A files are an improvement on MP3 files primarily due to the fact they are capable of being lossless, as opposed to the lossy competition. This means the files can be converted back and forth from the original audio file and file size. MP4 copying is restricted using the DRM technology but the M4A file type is easier to distribute and copy. This explains why the Apple store uses M4A files, to allow users to purchase audio and transfer the content to CD’s or mobile music players. Strictly an Apple product, it can be difficult to utilize the files in Windows. However, iTunes for Windows makes it possible, as well as converting the files to a Windows compatible audio file (which will cause lossy compression).