Due to the tree structure of the filter bank, pre-echo problems are made worse, as the combined impulse response of the two filter banks does not, and cannot, provide an optimum solution in time/frequency resolution. Additionally, the combining of the two filter banks' outputs creates aliasing problems that must be handled partially by the "aliasing compensation" stage; however, that creates excess energy to be coded in the frequency domain, thereby decreasing coding efficiency.[citation needed]
What kind of structure does a filter bank have? Due to a specific kind of structure, what kind of problems are made worse? What kind of resolution are the filter banks unable to provide an optimal solution for? Combining two filter banks' outputs creates what kind of problem? The need to code excess energy in the frequency domain decreases what kind of efficiency?