Macintosh Audio Compression/Expansion

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Macintosh Audio Compression/Expansion (MACE) is a lossy, proprietary compression scheme developed by Apple Computer for their Macintosh line of computers.

Technically, it's very similar to how ADPCM works.

It only works on 8bit streams. It offers two compression modes: 6:1 (1/6th of the original file size, 117 kbps) and 3:1 (1/3rd of the original file size, 235 kbps). Quality is relatively poor.

ffmpeg/libavcodec is able to decode MACE3 and MACE6 streams.

Users are encouraged not to use this codec, for several reasons:

There are better alternatives quality-wise (ADPCM, WavPack lossy, psychoacoustic codecs)
Proprietary codec - E.G, on Windows platform, it can only be encoded and played in QuickTime
Won't work on bit depths other than 8bit.

External Links

QuickTime plays and encodes MACE streams.
Reverse engineered MACE decoder sources by Laszlo Torok, part of ffmpeg.