Abstract
For coding of image sequences taken by an airborne IR sensor, an object-based coding method using MPEG-4 coding tools is investigated. In order to encode the landscape, current frame- based MPEG-4 coding is extended by global motion compensation, as proposed for MPEG-4 version 2, and by a sprite coding technique. This VOP0 encoder saves the bit-rate of the motion vectors due to global motion compensation and provides an additional bit-saving by not transmitting sprite prediction errors. Only extensions of the sprite are encoded. Object- based MPEG-4 coding by the VOP1 encoder is used for encoding moving objects, if the size of a moving object exceeds the size of a 16*16 pel macroblock. Thus, the data rate of the VOP0 and VOP1 coding depends on the size of the sprite extension area and the size of moving objects in the scene. Compared to frame-based MPEG-4 coding which reduces the bit rate by a factor of about 25 without visible distortions an additional compression factor of 2 can be achieved. To facilitate an implementation of the MPEG-4 coding tools a high computation power in combination with frequent access on varying positions of the entire image is required. Therefore, a flexible, parallel, high performance video signal processor architecture called PRISMA has been designed that employs a novel controlling scheme, called associative controlling.
