This invention relates to video transmission systems, in particular to those used to transmit video content generated and displayed on a source device to a second remote display. We describe a method of transmitting a video stream over a data link is described. Video frames are captured at a capture frame rate. The captured frames are then processed to identify duplicated frames in consecutively captured frames. Duplicated frames, duplicated as a result of capture the same source frame twice, are deleted leaving a filtered set of video frames. The remaining frames are retimed to amend a presentation time and transmitted over a data link to a rendering device.