FOURCC

FOURCC, literally four character code is used to specify the encoding under which video and audio data streams may be presented. All multimedia streams carry an DWORD flag as an identifier for compression or encoding used for the respective stream. In this way, at the Presentation Layer depicted abstractly in the OSI Reference Model, one can apply a specific decoder algorithm in order to extract the information in the desired and presentable format.

You may find useful information on the pages linked below:


 * FOURCC wikipedia article
 * The FOURCC.org website, a public codec and encoding definitions.
 * OSI Reference Model