If the MPEG you loaded has video, the "has_video" member of the SMPEG_Info structure will be set.

The video stream of an MPEG is displayed by telling the SMPEG library onto what surface it should copy the video. In most cases, this will simply be your window.

if (info.has_video)
  SMPEG_setdisplay(mpeg, screen,
                   NULL, callback);