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

Abstract

In this paper, we describe a software-based MPEG-4 video encoder which is implemented using parallel processing on a cluster of workstations collectively working as a virtual machine. The contributions of our work are as follows. First, a hierarchical Petri-nets-based modeling methodology is proposed to capture the spatiotemporal relationships among multiple objects at different levels of an MPEG-4 video sequence. Second, a scheduling algorithm is proposed to assign video objects to workstations for encoding in parallel. The algorithm determines the execution order of video objects, ensures that the synchronization requirements among them are enforced and that 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. We have made various additional software optimizations 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 encoding rate higher than real time, allowing the encoding of multiple sequences simultaneously. Index Terms-Data partitioning, dynamic scheduling, load balancing, MPEG-4, parallel and distributed processing, Petri nets, video encoder. I. INTRODUCTION T HE current and emerging multimedia services demand many more functionalities than those offered by the traditional standards. For example, mobile communication requires very low bit-rate video coding and error resilience across various networks, virtual reality and animation require integration of natural and synthetic hybrid object coding, and interactive digital video requires a high degree of object based interactivity. Instead of traditional frame-based interaction such as fast forward, fast backward, etc., new ways of interactivity are needed to efficiently realize such applications. The new standard, MPEG-4, which is currently being developed by MPEG, will enable the integration of the production, distribution, and content access paradigms in a multimedia Manuscript