Prefilters, sampling, and transmission rates for intraframe codecs for picturephone® service

This study of prefilters and sampling rates analyzes the edge busyness phenomenon which is a very significant degradation introduced by intraframe video coders. For any given transmission rate, the prefilter and sampling rate can be varied to yield a tradeoff between the edge busyness and the rise time associated with a video transition. A narrower prefilter results in less edge busyness but slower rise times and vice versa. Similarly, varying the sampling rate implies an inverse variation in the number of bits per sample allowed in the quantizer, which leads to a tradeoff between aliasing and quantizing noise, both of which are components of the edge busyness phenomenon. This paper shows in detail how the prefilter, sampler, and quantizer affect both edge busyness and rise time, and optimizes the intraframe coder design as a function of transmission rate from an analysis of this two-factor tradeoff.