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  Codec Central: m4a, mp4, aac & Apple Lossless


Successor to mp3, m4a (and mp4) is a container that can store many sub-formats, of which the main would be Advanced Audio Compression (AAC). Also using the .m4a container is Apples Lossless format (ALAC), this format is like WinZip for audio and looses no audio quality to compression (unlike ALAC which is lossless, audio tracks purchased from Apples iMS store are lossy aac). There are also .m4b files, these are identical to .m4a except the iPod knows to use them as audio books and allow book marking.

Adding ID tags to mp4 has standardized on the Apple iTunes format. Files ending in .m4a are audio content only, .mp4 can contain both audio and video, .m4v are video files.

Within AAC are different encoding types, LC (low complexity), HE (high efficiency) to name a few. To encode your audio to be compatible with most audio players, use the LC compression type (used as default by this encoder). High Efficiency (HE AAC) uses SBR technology (not too different as mp3PRO) if the player knows about HE the extra frequency information can be decoded, otherwise half the audio quality will be missing on playback. A newer standard again for ultra low bitrates is AAC+ or AAC HEv2, this uses parametric stereo for even lower bitrates, dBpoweramp is able to decode every AAC type (excluding iTunes m4p protected). 

Apple supplies protected mp4 files in a .m4p format from its online audio store (whilst dBpoweramp cannot decode these see Forum for details on fair use). Files ending in .aac are raw audio files.

 m4a, mp4, (aac & Apple Lossless)  



Description Decodes all mp4, m4a and aac (containing AAC LC, HE-AAC, AAC HE v2, aac+ or Apple Lossless). Note protected m4p, or m4b cannot be decoded.
Download    m4a, mp4 Codec   688 KB Version     Release 4
Decodes       .m4a, .mp4, .m4b (not protected audio), .aac Encodes   .m4a (either Apple Lossless, or AAC using Nero Digital Audio)
Author          Illustrate Email       Email dBpoweramp

 AAC to mp4 & mp4 to AAC  



Description Moves aac audio files in or out of a .mp4 container, without loss to audio quality.
Download    AAC to mp4 & mp4 to AAC   347 KB Version     Release 1
Decodes       [none] Encodes   [none]
Author          Illustrate Email       Email dBpoweramp
Notes            Install m4a, mp4 Codec and AAC Codec to preserve ID tags.