1. A method of signal processing, said method comprising: performing a coding operation on a portion in time of a digitized audio signal, wherein said coding operation includes an ordered plurality of iterations; for each of the ordered plurality of iterations, calculating a corresponding value of a gain measure for the coding operation, wherein the value is based on a calculated energy of a residue of the iteration of the coding operation; for each of a plurality of first threshold values, determining the first iteration, among the ordered plurality, at which a specified relation between the corresponding calculated gain measure value and the threshold value has a particular state, and storing an indication of the position of the iteration within the ordered plurality; and comparing at least one of the stored order indications to at least one corresponding second threshold value, wherein said gain measure for the coding operation is a monotone function with respect to the position of the iteration within the ordered plurality.