Xv is "
The XFree86 X Video Extension (Xv) Device Dependent Layer", an extension to XFree86 to allow for hardware accelerated video playback.
It was introduced in XFree86 4. (See the Xv(3x) man page.)
To find out if you're using it, try xvinfo. xvattr is also useful to set parameters for it.
2 pages link to Xv:
