1. A system, comprising: a processor; video feature extraction module configured by the processor to receive a video signal and to extract a two-dimensional feature from at least two video frames of the video signal; one-dimensional video feature computation module configured by the processor to derive a one-dimensional feature from the extracted two-dimensional feature; and visual rhythm detector module configured by the processor to detect visual beats and a visual tempo of the video signal from the one-dimensional feature, the visual rhythm detector module comprising: a pre-processing module configured by the processor to condition the one-dimensional feature to smooth fluctuations in the one-dimensional feature over a period of time; a different module configured by the processor to compute time derivatives of the conditioned one-dimensional feature at temporal positions within the time period; and a peak-picking module configured by the processor to: identify a plurality of local maxima in the computed derivatives, the local maxima representing corresponding ones of the visual beats and being associated with corresponding ones of the temporal positions; and determine a rate at which the local maxima occur within the time period, the rate representing the visual tempo.