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copied!<p>If you know what you are looking for, correlate the input signal against a replica of what you expect. Basically, implement a matched filter. If you want to see when the input stream is -127, -63, 0, 63, 127, implement a direct form fir filter with these values as the coefficients. Then look for a maximum on the output. The maximum output of a filter with those coefficients occurs when the data in the filter is -127, -63, 0, 63, 127.</p> <p>Google "Matched Filter Detection" or or "detection theory" maybe even "Feature detection"</p> <p>If you don't know exactly what you are looking for, or what you are looking for is variable, it gets more complicated. You would then try to implement a filter that's output would give you information about what is going on. The example that I gave above would show the output spike up when that input sequence occurred. If you then saw that spike occurring with regular frequency, you would guess that the input event was occurring with regular frequency.</p> <p>if you made your filter 0, 63, 127 63 0, which correlates to turning the knob all the way up, and then back down again, and on your output saw the aforementioned spike occur, but having a lower maximum amplitude and wider time over which the correlation occurs, that might tell you that the know was turned all the way up and then back down, but either slower or faster than the speed for which the filter is design to get a maximum response.</p> <p>To combat this you might implement 3 of these filters in parallel, one designed for a slow knob turn, one for a medium speed knob turn, and one for a fast knob turn. Then looking at the 3 outputs you get 3 different correlations which better help you understand what is occurring</p>

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