Recently there has been an increasing demand for video communication using very low bit rate channels that were initially designed to transmit speech or text. Such low bit rate channels include radio channels, Public Switched Telephone Networks (PSTN), and computer networks for transmitting electronic mail, which have channel capacities of less than 64kbit/s. Considering the present accessibility of these channels, the realization of video communica.tion at such bit rates may bring forth the future popularization of visual telephony....[ Read more ]

Recently there has been an increasing demand for video communication using very low bit rate channels that were initially designed to transmit speech or text. Such low bit rate channels include radio channels, Public Switched Telephone Networks (PSTN), and computer networks for transmitting electronic mail, which have channel capacities of less than 64kbit/s. Considering the present accessibility of these channels, the realization of video communica.tion at such bit rates may bring forth the future popularization of visual telephony.

In order to realize these low bandwidth video transmission services, some new innovations in coding schemes need to be developed. In this thesis, Region Based Coding (RBC) schemes are investigated as a possible solution. Comparing RBC to conventional coding schemes, such as Block Based Coding (BBC), RBC has been shown to have good potential for obtaining high image quality as well as compression ratio.

In the course of the investigation, many problems in region based techniques are solved, such as segmentation, contour extraction, motion compensation and frame reconstruction. Consequently, three complete schemes are proposed. Two are based on Contour Motion Compensated Coding (ChlCC) which are shown to be able to provide very good quality and a competitive bandwidth reduction. The third one is the Segmented Motion Transform (SMT) coding which provides excellent visual quality and extremely high compression ratio. Furthermore, SMT coding does not suffer from high computation cost. This shows it is feasible in the real world and potentially able to realize visual telephony using very low bit rate channels.