Editing Inter frame (section)

=== Enhanced Direct/Skip Macroblock ===
Skip and Direct Mode are very frequently used, especially with B-frames. They significantly reduce the number of bits to be coded. These modes are referred to when a block is coded without sending residual error or motion vectors. The encoder will only record that it is a Skip Macroblock. The decoder will deduce the motion vector of Direct/Skip Mode coded block from other blocks already decoded.

There are two ways to deduce the motion:
[[File:Direct skip.jpg]]
; Temporal: It uses the block motion vector from List 1 frame, located at the same position to deduce the motion vector. List 1 block uses a List 0 block as reference.
; Spatial: It predicts the movement from neighbour macroblocks in same frame. A possible criterion could be to copy the motion vector from a neighboring block. These modes are used in uniform zones of the picture where there is not much movement.

[[File:block partition.jpg]]

In the figure above, pink blocks are Direct/Skip Mode coded blocks. As we can see, they are used very frequently, mainly in B-frames.