ARCLICK

ARCLICK finds clicks, crackle, ticks and short dropouts and replaces them - not with silence, and not with a filter, but with the sound that should have been there. For every moment it keeps a model of what the recording has been doing, and asks what the next sample should be. When the real sample is far outside what the model expects, that sample is not music. ARCLICK marks the whole burst, then rebuilds it by running the model forwards from before the damage and backwards from after it. Everything else is left exactly as it was. On material with no clicks in it the output is bit for bit identical to the input - not close, identical. On a recording with forty clicks in it, all forty were found, the crackle energy fell 13.6 decibels, the median event was cleaned by 17.9, and 0.26 percent of the samples were changed. Telling a click from a drum hit is the whole difficulty, and there are three tests before anything is touched: the burst has to end within MAX LENGTH, the recording has to be calm again just past it, and the sample has to fall far enough outside the recording's own ordinary prediction error. Six seconds of drums with no damage in them produced three repairs.