X-Video Motion Compensation is an extension of the X video extension (Xv) for the X Window System. The XvMC API allows video programs to offload portions of the video decoding process to the GPU video-hardware. In theory, this process should also reduce bus bandwidth requirements. Currently, the supported portions to be offloaded by XvMC onto the GPU are motion compensation (mo comp) and inverse discrete cosine transform (iDCT) for MPEG-2 video. XvMC also supports offloading decoding of mo comp, iDCT, and VLD ("Variable-Length Decoding", more commonly known as "slice level acceleration") for not only MPEG-2 but also MPEG-4 ASP video on VIA Unichrome (S3 Graphics Chrome Series) hardware.
XvMC was the first UNIX equivalent of the microsoft Windows DirectX Video Acceleration (DxVA) API. Popular software applications known to take advantage of XvMC include MPlayer, MythTV, and xine.