Welcome to the proceedings of the 10th Pacific Rim Conference on Multimedia (PCM 2009) held in Bangkok, Thailand, December 15-18, 2009. Since its inception in 2000, PCM has rapidly grown into a major conference on multimedia in the Asia- Pacific Rim region and has built up its reputation around the world. Following the success of the preceding conferences, PCM 2008 in Taiwan, PCM 2007 in Hong Kong, PCM 2006 in China, PCM 2005 in Korea, PCM 2004 in Japan, PCM 2003 in Singapore, PCM 2002 in Taiwan, PCM 2001 in China, and PCM 2000 in Australia, the tenth PCM brought researchers, developers, practitioners, and educators together to disseminate their new discoveries in the field of multimedia. Theoretical bre- throughs and practical systems were presented at this conference, thanks to the s- port of Naresuan University, Mahanakorn University of Technology, and the IEEE Thailand Section. PCM 2009 featured a comprehensive program including keynote talks, regular - per presentations, posters, and special sessions. We received 171 papers from 16 countries including Australia, Sweden, German, Italy, Iran, France, Canada, China, Japan, Korea, Malaysia, Singapore, Taiwan, Hong Kong, the UK, and the USA. After a rigorous review process, we accepted only 67 oral presentations and 45 poster pr- entations. Four special sessions were also organized by world-leading researchers.