In an approach for visual liveness detection, a video-audio signal related to a speaker speaking a text is obtained. The video-audio signal is split into a video signal which records images of the speaker and an audio signal which records a speech spoken by the speaker. Then a first sequence indicating visual mouth openness is obtained from the video signal, and a second sequence indicating acoustic mouth openness is obtained based on the text and the audio signal. Synchrony between the first and second sequences is measured, and the liveness of the speaker is determined based on the synchrony.