1. A method for classifying a video, comprising the steps of: defining a set of classes for classifying an audio signal of a video; combining selected classes of the set as a subset of important classes, the subset of important classes being important for a specific highlighting task; combining the remaining classes of the set as a subset of other classes; training jointly the subset of important classes and the subset of other classes with training audio data to form a task specific classifier; and classifying the audio signal using the task specific classifier as either important or other to identify highlights in the video corresponding to the specific highlighting task.