ALE (Apple Lossless Encoder) is an lossless audio format from Apple, also known as ALAC, Apple Lossless Audio Codec, or simply Apple Lossless. It will typically have a .mp4a extension.

[edit] features

• Supports: 16 & 24 bit, multi channel (such as 5.1) & high frequency audio
• Has iPod and iTunes support but limited support outside the Apple tool set.
• Stored in MPEG 4 container but so is AAC making it difficult to tell which you have.
• standard encoding but fast decoding
• Apple Lossless can compress CD quality audio file to roughly half its original size.
• normally played by Quicktime.

Thought to be based loosely on FLAC (Free Lossless Audio Codec) however Apple has not released any details on the format.

[edit] metadata

It is 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. The maximum length of each tag value is 255 characters. Multiple artists, etc are supported as is embedded album art.