| With the rapid convergence in telecommunications, computer, and TV/film industries, rigorous efforts are in progress for designing the emerging multimedia standard known as MPEG-4. The main features of MPEG-4 are its content-based interactivity, efficient coding, and universal access. Due to its content-based representation nature and flexible configuration structure, not only does an implementation of MPEG-4 have to support a large number of algorithms; it also needs to support flexibility to allow different usage of these algorithms as well as user interactions. Hardware-based approach seems to be very much application specific, and software-based implementation is a natural and viable option.; In this thesis, we proposed a software-based MPEG-4 video encoder which is implemented using an efficient parallel processing scheme on a cluster of workstations collectively working as a virtual machine. First, a hierarchical Petri nets based modeling methodology is proposed to capture the spatio-temporal relationships among multiple objects at different levels of an MPEG-4 video sequence as well as the user interactions. Second, we proposed a number of scheduling algorithms that allocate MPEG-4 objects to multiple workstations ensuring that the synchronization requirements among them are enforced, and presentation deadlines are met. Third, a dynamic partitioning scheme is proposed which divides an object among multiple workstations to extract additional parallelism. The scheme achieves load balancing among the workstations with a low overhead. The striking feature of our encoder is that it adjusts the allocation and partitioning of objects automatically according to the dynamic variations in the video object behavior. Various additional software optimization have been made to further speed up the computation.; The performance of the encoder can scale according to the number of workstations used. With 20 workstations, the encoder yields an real-time encoding rate on QCIF format video objects which demonstrates its potential to be used in a real system. |
