hi kajol:-
In video compression, motion compensation is a technique for describing a picture in terms of the transformation of a reference picture to the current picture. The reference picture may be previous in time or even from the future. When images can be accurately synthesised from previously transmitted/stored images then the compression efficiency can be improved.
In global motion compensation, the motion model basically reflects camera motions such as dolly (forward, backwards), track (left, right), boom (up, down), pan (left, right), tilt (up, down) and roll (along the view axis). It works best for still scenes without moving objects. There are several advantages of global motion compensation:
1. It models the dominant motion usually found in video sequences with just a few parameters. The share in bit-rate of these parameters is negligible.
2. It does not partition the frames. This avoids artifacts at partition borders.
3. A straight line (in the time direction) of pixels with equal spatial positions in the frame corresponds to a continuously moving point in the real scene. Other MC schemes introduce discontinuities in the time direction.
Answered by
shepherd
, an ibibo Master,
at
5:18 PM on April 30, 2008