Channel segment function: repeats the animation between frames f1 and f2, accumulating the value.
Each repeated portion will have its first value set to the last value of the previous cycle. The rest of the values are set such that their relative increments with respect to the first value match the relative increments in the channel interval between f1 and f2. If you wish to repeat motion exactly, use the cycle function instead.
If f1 is less than f2, then it will cycle forwards from f1 to f2. If f2 is less than f1, then it will cycle backwards from f2 to f1.