WHAT IS M4A?
MPEG-4 Audio Layer
The International Organization for Standardization
M4A is described in the MPEG-4 Part 14 standard created by the International Organization for Standardization. While MP4 files can contain audio and video, M4A is designed for audio only. This file type can be used to store music, podcasts, or audiobooks. Apple devices and programs support M4A natively, and it is the most common format in iTunes. On Windows, you might need to install an additional codec pack to open and play an M4A file.
In the M4A format specification, you might see one of two codecs: AAC or ALAC. ALAC provides lossless compression, so these files might be relatively large compared to those compressed with AAC, which offers lossy compression. If you’re wondering how to choose between these codecs when converting files to M4A, think about the audio playback. Lossless compression means better quality.
Windows Media Player 12 (older versions will require additional codecs), iTunes, QuickTime, and VLC