Perceptual Coding - Interactions Between Models and Coders
Thursday, February 1, 2001 - 11:00am - 12:00pm
Jim Johnston (AT&T Laboratories - Research)
This talk will provide a tutorial on perceptual audio coders, as well as introduce the basics of some perceptual image coders. In the course of explaining the basics behind the perceptual coder a number of problems arise in fitting together the lossy, non-linear perceptual process with the generally linear, LMS coding process, with its attached information-theoretic and computer-science like entropy coding and solution methods. A number of these interactions will be pointed out, from filterbank fitting vs. perceptual models, to quantization strategy vs. error loudness. Some ad-hoc solutions will be shown, and some open questions will be mentioned. To date, there has been very little work in actually determining an 'optimum' to such problems, rather work on finding something that works, that can approximate the optimum, rather than finding an optimum. Perhaps this work will be mature when, given a perceptual model and a (set of) filterbanks, quantizers, etc, one can produce evidence of a true optimum.