Joint control of MPEG VBR video over ATM networks

In video applications, digital encoding techniques are frequently associated to the use of compression algorithms. Compression algorithms such as the MPEG 2 standard allow economies in transmission bandwidth, while providing a service with a quality similar or better to the current analogue systems. The reduction in the number of bits necessary to represent a given sequence is achieved by exploiting spatial and temporal redundancy in the original video sequences. The number of bits necessary to achieve a given picture quality level will be variable because the redundancy in the original sequence is also variable. This means that compression algorithms such as the MPEG 2 standard will generate variable bit rate (VBR) encoded bit streams if a constant quality is to be obtained. The goal of the work described in this paper is to develop dynamic multiplexing algorithms to be implemented at the user terminal equipment and to study the potential benefits of jointly controlling the bit rate of several encoders and the channel bit rate. The bit rate of the VBR transmission channel is constrained by leaky bucket policing functions. The source bit rate is determined and controlled on a picture basis by the proposed dynamic bandwidth allocation algorithm with the objective of maintaining a minimum level of quality among all video sources using always the least possible bandwidth and without violating the traffic contract