MPEG-4 Main Profile decoder partitioning with respect to bit stream processing

The MPEG-4 object based profiles pose highly varying computational demands. To enable real-time and power efficient decoding of these profiles, parallelization of the algorithm is a necessity. At this, sensible system partitioning is of paramount concern in order to keep communication and synchronization overhead low. It is shown that especially the bit stream level decoding is considerably more complex than in earlier, frame based video coding standards. Therefore, it is best executed on a dedicated unit. Based on the data dependencies between individual decoding operations, an interface between bit stream level and higher level decoding is derived which causes minimal synchronization overhead. An optimized software implementation of Main Profile bit stream level decoding shows that its computational demands for arbitrarily shaped Video Objects are 3.8-4.2 times as high as for frame based video. Under worst-case conditions 547.5MIPS are required for a Main@L2 decoder on a 32-bit MIPS RISC processor