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Overlay details: Motion vectors | Overlay details: Motion vectors: Arrows
In the colour wheel representation, hue represents direction and depth of colour represents size. This is carried out by setting the U and V picture components equal to the x and y motion vector components (with a scaling factor) respectively. An example of this is shown in Figure 2(b). The legend indicates in which direction colours are found with the origin of the motion vector at the centre of the cross, i.e. orange indicates a motion vector direction of straight down. The frame number and reference frame number are displayed in order for the information to be put into context. In Figure 2(b), the motion vectors are in the opposite direction to the actual displayed motion as the reference frame precedes the current frame in display order.
By default, full colour intensity represents motion vectors of 25 1/8th pixels or greater. This may be adjusted using the command option -clip n. No colour indicates no motion.
Figure 2. (a) 'BBC comp' sequence frame 26 (b) with colour wheel motion vector field overlay