A software-based MPEG-4 video encoder using parallel processing

In this paper, we describe a software-based MPEG-4 video encoder which is i mplemented using parallel processing on a cluster of workstations collectiv ely working as a virtual machine. The contributions of our work are as foll ows. First, a hierarchical Petri-nets-based modeling methodology is propose d to capture the spatiotemporal relationships among multiple objects at dif ferent levels of an MPEG-4 video sequence, Second, a scheduling algorithm i s proposed to assign video objects to workstations for encoding in parallel , The algorithm determines the execution order of video objects, ensures th at the synchronization requirements among them are enforced and that presen tation deadlines are met, Third, a dynamic partitioning scheme is proposed which divides an object among multiple workstations to extract additional p arallelism, 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 dynam ic variations in the video object behavior. We have made various additional software optimizations to further speed up the computation. The performanc e of the encoder can scale according to the number of workstations used. Wi th 20 workstations, the encoder yields an encoding rate higher than real ti me, allowing the encoding of multiple sequences simultaneously.