Handheld , Mobile Video Conferencing

Recent improvements in the technology of handheld computers and mobile communications have made the task of exploring handheld mobile video conferencing feasible. Handheld mobile video conferencing introduces a number of constraints that affect the type of coders and protocols that are used. This research project has explored audio and video coders that are suitable for use in a handheld wireless environment. Six different video coders, both existing and new, were evaluated in the areas of computational complexity, stability of bit-rate and quality. Of these, two coding schemes that have not previously been applied to video coding were designed and evaluated. The first is based on the forest of Quadtrees coding technique which improves the stability of the bit-rate of the Quadtree coding technique. The forest of Quadtrees offers low computational complexity making it suitable for handheld computing. The second is a block-based conditional replenishment SPIHT coding scheme that uses the S+P wavelet transform. This scheme localises errors and artefacts that are produced by the S+P transform SPIHT video coder. This research shows that this block-based conditional replenishment technique both reduces coding times and improves quality over the standard S+P transform SPIHT coding technique. A robust protocol was developed that is designed for low bandwidth environments with low signal-to-noise ratios. The protocol contains minimal overhead and contains a number of features that allow it to recover from the errors that are produced by wireless networks. A video conferencing framework based on C++ was developed that can be implemented on the wide variety of handheld computing platforms currently available. This framework including the audio and video coders was implemented and tested on four platforms including Newton OS, Windows CE, Mac OS and Win32. This project demonstrates that video conferencing with handheld devices over wireless networks is possible and identifies areas for further research.