Xv is the X Window System video extension.
The Xv extension provides support for video adaptors attached to an X display, an adaptor may be able to display video, capture video, or both. It translates between video encoding (NTSC, PAL, SECAM, etc...) and drawable format.
For more information see http://ftp.x.org/pub/X11R7.0/doc/html/Xv.3.html
If you need to disable xv, just set the NO_XV environment variable