Depth value for positioning a caption in 3D video

A method of generating a recommended depth value for use in displaying a graphics item over a three dimensional video is described. The method include: receiving, at a headend, a three dimensional video including a sequence of video frames; analyzing each frame of the three dimensional video in turn to produce a sequence of depth maps, each map corresponding to a video frame in the sequence of video frames, each depth map comprising a depth value for every pixel location of its corresponding frame, each depth map being associated with timing data relating that depth map to its corresponding video frame; selecting a sub-sequence of the sequence of depth maps; analyzing the sub-sequence to identify a furthest forward depth value occurring in the sub-sequence of depth maps; and transmitting the furthest forward depth value as the recommended depth value to a display device. One or more sub-regions of the depth maps may be analyzed instead of the whole map. A method of displaying OSD messages is also included.