Editing Inter frame (section)

=== Resolution of up to ¼ pixel motion compensation ===
Pixels at half-pixel position are obtained by applying a filter of length 6.

 H=[1 -5 20 20 -5 1], i.e.
 half-pixel "b"=A - 5B + 20C + 20D - 5E + F

Pixels at quarter-pixel position are obtained by [[bilinear interpolation]].

While [[MPEG-2]] allowed a ½ pixel resolution, Inter frame allows up to ¼ pixel resolution. That means that it is possible to search a block in the frame to be coded in other reference frames, or we can interpolate nonexistent pixels to find blocks that are even better suited to the current block. If motion vector is an integer number of units of samples, that means it is possible to find in reference pictures the compensated block in motion. If motion vector is not an integer, the prediction will be obtained from interpolated pixels by an interpolator filter to horizontal and vertical directions.

[[File:Subpel interpolation.jpg]]