Joint source/channel coding of statistically multiplexed real-time services on packet networks

We investigate the interactionof congestion control with the partitioning of source information into components of varying importance for variable bit-rate packet voice and packet video. High-priority transport for the more important signal components results in substantially increased objective service quality. Using a Markov chain voice source model with simple PCM speech encoding and a priority queue, simulation results show a signal-to=noise ratio improvement of 45 dB with two priorities over unprioritized system. Perfomance is sensitive to the fraction of traffic placed in each priority, and the optimal partition depends on networks loss condition. When this partition is optimized dynamically, quality degrades gracefully over a wide range of load values. Results with DTC encoded speech and video samples show similar behavior. Variations are investigated such as further partition of low-priority information into multiple priorities. A simulatione with delay added to represent other network nodes shows general insensivity to delay of network feedback information. A comparaison is made between dropping packets on buffer overflow and timeout based on service requirements

Exploring Discrete Cosine Transform for Multi-resolution Analysis

Multi-resolution analysis has been a very popular technique in the recent years. Wavelets have been used extensively to perform multi resolution image expansion and analysis. DCT, however, has been used to compress image but not for multi resolution image analysis. This thesis is an attempt to explore the possibilities of using DCT for multi-resolution image analysis. Naive implementation of block DCT for multi-resolution expansion has many difficulties that lead to signal distortion. One of the main causes of distortion is the blocking artifacts that appear when reconstructing images transformed by DCT. The new algorithm is based on line DCT which eliminates the need for block processing. The line DCT is one dimensional array based on cascading the image rows and columns in one transform operation. Several images have been used to test the algorithm at various resolution levels. The reconstruction mean square error rate is used as an indication to the success of the method. The proposed algorithm has also been tested against the traditional block DCT