FourCC
A FourCC – also spelled FOURCC or fourcc – is a 4-byte identifier which specifies the format of a video stream.
Every codec has its own unique FourCC. Commonly, each byte corresponds to a printable character in the ASCII character set, making the sequence human-readable.
This is very useful for determining whether VLC media player can decode a video stream. For audio streams, a TwoCC is used.
Good lists of FourCC can be found here:
