Given two inputs
da[t] = abs(a[t] - a[t - 1]) and
db[t] = abs(b[t] - b[t - 1]). Output
da[t] is smaller, and output
db[t] is smaller. If
da[t] == db[t], use whichever input was used last (assume
a for the first sample of output).
Input signal A.
Input signal B.
the control that changed least is used as output: