MP3 versus M4A versus WAV versus AAC format

Motivation for M4A Format - What is Wrong with MP3?

Mpeg 3 audio (better known as MP3) is a lossy audio compression format, succeeded by M4A (higher quality with lower bit rates and file size).  The bit rate is the number of bits conveyed per unit time, and is (generally) measured in bits per second (generally higher bit rates allow for higher quality).

If WAV has higher quality, why not use it?

WAV files (pronouned WAVE) have high quality but no compression, so this format is not widely used for music collections. It was developed by Microsoft and IBM in 1991.

Alternative File Extensions for M4A

.MP4 is sometimes used as an alternative file extension to .M4A.

Advanced Audio Coding (AAC)

Audio standard for lossy digital audio compression.

Ogg Vorbis Sound Files

What are Ogg Vorbis sounds files a.k.a. .ogg files? Ogg Vorbis is an audio compression format comparable to MP3. Ogg is a container format for audio, video and metadata maintained by xiph.org. Vorbis is the specific audio compression scheme used.

According to the Vorbis technical specification, the codec is based on the Modified Discrete Cosine Transform (MDCT) which is also used in the MP3 format. Vorbis is, however, computationally simpler than MP3 but requires more working memory.

The Business of Overdrive: DRM Entrepreneurs

Overdrive: the Rights Management entrepreneurs, provide software to process digitally protected audio-books but also provide a distribution service, where titles are warehoused on behalf of publishers. It's run by founder Steve Potash.