On Design-Time Performance Predictions of Object-Based MPEG-4 Video Applications

Development costs and time-to-market of software-intensive media processing systems can be reduced when correct decisions are made at an early design phase. However, the real-time requirements imposed on these systems, such as frame skipping and latency limitations, can only be validated after system implementation, e.g. at the test phase. To avoid system redesign for ensuring real-time performance, a system performance analysis should be done as soon as possible. This paper addresses a scenario simulation approach for performance predictions already at the design phase. This approach is presented through a real case study, for which we developed an advanced MPEG-4 coding application. The benefits of the approach are threefold: a) high accuracy of the predicted performance data; b) an efficient real-time software-hardware implementation of a system, because the generic computational costs become known in advance, and c) improved ease of use because of a high abstraction level of modelling. Experiments showed that the prediction accuracy of the system performance is within 10%, while the prediction accuracy of the time-detailed processor usage (performance) does not exceed 30%. However, the real-time performance requirements are sometimes not met, e.g. when other applications require intensive memory usage, thereby imposing delays on the decoding data retrieval from memory.