In video conferencing and videotelephony applications, the bit rate of sending video sequences must be kept low due to the limited channel bandwidth....[ Read more ]

In video conferencing and videotelephony applications, the bit rate of sending video sequences must be kept low due to the limited channel bandwidth.

In this thesis, we propose and study some postprocessing techniques for VLBR system. To satisfy the very-low-bit-rate (VLBR) requirement of the Public Switch Telephone Network (PSTN), temporal subsampling is a simple technique which may be combined with other compression schemes to achieve very large compression ratio.

Previously proposed motion compensated temporal interpolation (MCTI) can interpolate frames with reasonably good visual quality at the price of high computational requirement and some blocky artifacts. In this thesis, we propose a temporal interpolation using optic flow (TIOF) to solve the problem of blocky artifacts. Another post-processing technique called unidirectional motion compensated temporal interpolation (UMCTI) is proposed to reduce the computation requirement while keeping the visual quality unchanged or even higher.

Moreover, fast algorithms and visual quality improvement algorithms for UMCTI are proposed for improvement of UMCTI.

Finally, we implement the UMCTI into the H.263 codec to increase the frame rate of the output. Modification are added to UMCTI to improve visual quality.