A circuit is used to process video signal from a video sensor. The video signal includes video content signal and synchronization signals. The circuit includes a status register, a data register, and a processor. The status register provides a sampling clock signal to the data register and the video sensor. The sampling clock signal is synchronized with the synchronization signals to sample the video signal. The status register stores the synchronization signals. The data register storing the video content signal. The processor is coupled to the status register and the data register. The processor reads the video content signal from the data register according to the synchronization signals in the status register.