6. The method of claim 1 wherein: substantially all the segments have the same width; the set of features for the potential keyword includes a plurality of feature vectors, each feature vector corresponding to a respective one of the segments; and a given feature vector for a given segment represents pixel values of the given segment.
7. The method of claim 6 wherein a feature vector for a given segment of the potential keyword includes a representation of the topmost pixel in the given segment having a value above a threshold, a representation of the bottommost pixel in the given segment having a value above the threshold, and a set of autocorrelation values.