Another technique for extracting information is global feature calculation. This would cover features of a stream that are not localised. For example for continuous channels, the global maximum and minimum value that each channel takes; the average value of each channel and so on. They may be more complicated. For example, we could count the number of local maxima and minima, we could measure the total ``distance'' covered by each channel, or use some measure of energy. For discrete binary channels, it might be something like how many changes there are, the percentage of time for which the value is true and so on.
Note that global features may be associated with either a single channel or more than one channel. For example, in the Auslan domain, we could measure the distance using a Euclidean metric on the x, y and z motions, or on each channel separately. For simplicity below, we consider global feature calculation for a single channel.