.U File Extension

Contains settings used by Unreal Tournament; stored within the Unreal System directory, i.e. "\Unreal\System\Engine.u;" may be replaced with custom class packages

Audio container format typically used to store ?-law encoded audio data; introduced by Sun Microsystems and also used by MusicKit for the NeXT operating system; contains a header that includes six 32-bit words, an optional information section, then the audio data.

AU files typically use the .AU extension.

Subsampled "U" image created by ppmtoyuvsplit, a Unix-based command-line utility that splits .PPM files into .Y, U, and .V files; contains the "U" chrominance, or color, component for the image; used for storing image data in a format required by the Stanford MPEG codec.

Y, U, and V files can be built back into their original PPM file using the yuvsplittoppm utility.

NOTE: The ppmtoyuvsplit and yuvsplittoppm programs are part of netpbm, a Unix-based graphics package.