Abstract
Due to the needs of real-time, bandwidth intensive applications like videoconferencing, several resource reservation infrastructures like the Integrated Services Packet Network (ISPN) are currently being developed. These schemes provide applications with a way to reserve a fixed quantity of network resources for their exclusive use. Most video encoders, however, are variable rate. This research describes a mechanism by which variable bit-rate, real-time video streams can be sent over a fixed rate resource reservation with a high level of reservation utilization. A Predictive/Adaptive Rate Control (PARC) mechanism is developed which dynamically adjusts the quality of the video encoding using a prediction mechanism to obtain a nearly constant output rate. This rate can then make use of a high percentage of the reserved rate. The controlled coder output is buffered so that any errors in the predictive video quality adjustment can be smoothed. Network delay feedback is used to control the buffer delay so that none of the data packets exceed an allowable real-time delay maximum for useful video-conferencing. Finally, the reservation rate is adapted over time to match the needs of each particular video sequence. This research is implemented and tested using a multi-layered version of the popular CU-SeeMe video encoder built into a basic video-conferencing tool. While the resulting image quality remains high, increases in link utilization as high as 108.8% over current techniques used for sending variable bit-rate over resource reservations are shown.
Schroeder, Charles Grant (1996). Increased network efficiency for variable rate video streams in an Integrated Services Packet Network environment. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -S372.