MPEG4 Video Codec on a Wireless Handset Baseband System

In this paper we present a cache-performance analysis of an MPEG4 video codec running on a wireless handset Digital BaseBand (DBB) system. We outline the AD6532 DBB system architecture, and the software optimizations used to port an efficient version of an MPEG4 codec to the Blackfin core. Our primary focus is the impact of write-back (WB) versus writethrough (WT) data cache policy on the system performance of data-intensive workloads such as video codecs. We find that for these workloads, even though a WB cache policy generally tends to have shorter execution times than WT, it also tends to increase data bandwidth. In systems where data movement dominates overall execution time, WT tends to outperform WB. WT also has an advantage in terms of bandwidth determinism.