you might have noticed our equalizer tool, and been confused by it and the many controls. that’s probably partly because you didn’t see a similar thing before, we had to develop it first.
very short history behind the ui is a powerful frequency domain processing technique, based on wavelets. the most commonly used wavelets are based on the lifting scheme [swe97], work in a data-independent way, and are decimated (i.e. the coarse coefficients are much more sparse than the fine ones).
This is a companion discussion topic for the original entry at https://www.darktable.org/2011/11/darktable-and-research/