Streaming Media in Variable Bit-Rate Environments

We consider streaming of video sequences over both, constant and variable bitrate (VBR) channels. Our goal is to enable decoding of each video unit before exceeding its displaying deadline and, hence, to guarantee successful sequence presentation even if the media rate does not match the channel rate. In this work, we will show that the separation between a delay jitter buffer and a decoder buffer is in general sub-optimal for VBR video transmitted over VBR channel. We will define the minimum initial delay and the minimum required buffer for a given video-stream and a deterministic VBR channel. In addition, we provide some probabilistic statements in the case that we have a random behaviour of the channel bit-rate. A specific example tailored to wireless video streaming is discussed in greater details and bounds are derived which allow to guarantee a certain quality-of-service even for random VBR channels in a wireless environment. Simulation results validate the findings. 1