Apple Lossless

Extension: .m4a
Codec Type: Lossless
Developer: Apple Inc.
Supports: 16 & 24 bit, multi channel & high frequency audio
Extra Details: Stored in MPEG 4 container
Strengths: iPod support, fast decoding, versatile ID Tagging
Weaknesses: Limited support outside of iPod / iTunes
ID Tagging: Quicktime / iTunes

Apple Lossless (also known as Apple Lossless Audio Codec, ALAC, or Apple Lossless Encoder, ALE) a type of audio compression created by Apple Inc.

Having Lossless in the name, obviously means Apple Lossless is a Lossless codec, unlike a lossy codec (such as mp3) where audio quality is lost forever in the name of smaller files, lossless stores the original CD track without loss, like zip for audio. Apple Lossless can compress CD quality audio file to roughly half its original size.

Apple Lossless files are stored in the MPEG 4 container and have a .m4a extension. The MPEG 4 container is also used for Advanced Audio Compression (AAC), a lossy compression (currently all tracks purchased from iTunes Music Store (iTMS) are AAC).

Have a .m4a file but do not know if it contains Apple Lossless or AAC? dBpoweramp Music Converter is able to show the contents (Apple Lossless or AAC) of an m4a file, by simply holding the mouse over.

Performance

Compression wise, ALAC is quite average amongst other Lossless codecs, whilst decoding speed is one of its strongest assets. ALAC files are not hindered by tagging limitations.

ID Tagging

Being stored in a m4a file, Apple Lossless files are tagged using the Quicktime / Apple iTunes tagging format, a relatively simple tagging format, supports Unicode characters (UTF-8). Any ID tag name can be added, yet the maximum length of each tag value is 255 characters. Multiple artists, etc are supported as is embedded album art.

Technical Details

Thought to be based loosely on FLAC (Free Lossless Audio Codec), both use Linear Prediction, Apple have not released any technical documents on Apple lossless, 3rd-party manipulation of Apple Lossless files are solely to the reverse engineering work of David Hammerton [craz.net]. Apple Lossless files can be decoded at relatively high speed, in comparison to other lossless codec.

Apple lossless supports 16 bit and 24 bit audio, as well as multi channel audio, such as 5.1

First appearance: April 2004 with iTunes 4.5.

Technical Lossless Codec Comparison [wiki.hydrogenaudio.org]

Creating, Converting & Ripping to

dBpoweramp Music Converter supports ripping to and conversion from Apple Lossless, 24 bit 192KHz is also supported.

Being lossless, Apple lossless can be converted to any other lossless format without quality loss, or to a smaller lossy file for use on a portable, such as iPod.

Compatibility

Hardware: Later model Apple iPods, Sonos, Apple AirPort Express. Apple Shuffles due to limited memory are not compatible with ALAC.

Other Mainstream Lossless Codecs

The True Audio (TTA) | Wavpack | Windows Media Audio Lossless (WMA)

Spoons Audio Guide