1. A data processing apparatus for detecting a probability of speech based on video data, the data processing apparatus comprising: at least one processor; a non-transitory computer-readable storage medium including instructions executable by the at least one processor, wherein execution of the instructions by the at least one processor causes the data processing apparatus to execute: a visual speech detector configured to receive a coordinate-based signal, the coordinate-based signal representing movement or lack of movement of at least one facial landmark of a person in a video signal; the visual speech detector configured to calculate a short-term value representing short-term characteristics of the coordinated-based signal and a long-term value representing long-term characteristics of the coordinate-based signal, the visual speech detector configured to compute a probability of speech of the person based on a comparison of the short-term value and the long-term value, wherein, when the short-term value is greater than the long-term value, the visual speech detector computes the probability of speech as a value indicating that speech as occurred.