On the Estimation and Model Costs in

Various implementation of the context tree algorithm have demonstrated that thisapproach to data compression is very successful. Recently the algorithm was also appliedto the problem of lossless still image compression. Although the compression ratio resultsare promising and belong to the best achieved, one needs a better understanding of themechanisms that cause that compression ratio from not improving beyond a certain depthof the context tree. This paper addresses these mechanisms and ways to decrease theire ects.7