Transmission of variable bit-rate MPEG-2 video streams over ATM: applications, challenges, and techniques

Compressed digital video is inherently variable rate since its complexity and motion content directly affect the encoding rate. This paper addresses the issues in encoding variable rate MPEG video for transmission applications to realize bandwidth savings while maintaining quality. The applications and benefits of variable rate encoding are compared with constant rate encoding. Variable rate encoding is commonly used in storage applications such as digital versatile discs (DVDs). In these applications the bit utilization is optimized over the entire encoding session to produce a desired peak and average rate for the stream. This rate control approach may not be ideal for transmission applications since it does not bound the burstiness of the stream. Experimental results are presented to demonstrate the feasibility of transmitting variable rate MPEG streams over an ATM network. The traffic parameters for these streams are analyzed for several encoding options. The bandwidth saving is quantified by estimating the effective bandwidth of variable rate streams and comparing it with the bandwidth of constant rate streams of similar quality.