1. A computer-implemented method for detecting presence of a hand gesture in video frames, the method comprising: receiving video frames having an original resolution; downscaling the received video frames into video frames having a lower resolution; detecting a motion corresponding to the predefined hand gesture in the downscaled video frames based on temporal motion information in the downscaled video frames; detecting a hand shape corresponding to the predefined hand gesture in a candidate search window within one of the downscaled video frames using a binary classifier, wherein the candidate search window corresponds to a motion region containing the detected motion; and determining whether the received video frames contain the predefined hand gesture based on the hand shape detection.