As a single chip can integrate more transistors than before, it can become a high-performing and inexpensive system for various important multimedia applications in our daily lives. In this work, we summarize a number of trends in multimedia system-on-chip (SoC) technologies. Because the new characteristics will drive the demand of new design methodology, we then summarize challenges and opportunities in multimedia SoC designs. We believe that in order to gain competitiveness, SoC design companies must improve efforts in the complete solution. This requires investigation into multi-disciplinary research topics.