Introduced in 1998, the cook codec was the first audio codec developed by RealNetworks in-house, and was named after its author, Ken Cooke.
In 2003, RealNetworks introduced a surround sound version of cook, called RealAudio Multichannel.
This was initially designated by the four-character code 'whrl', but is now identified as 'cook', as mono/stereo files are.
Although RealNetworks never published a technical description of the cook codec, others have reverse engineered the format, and as of December 2005, FFmpeg libavcodec contains a decoder capable of playing cook-encoded files.
As of July 2009, Rockbox is capable of playing cook-encoded files as well.