A control signal is provided to a video data acquisition system that generates video data. In response to receiving the control signal, the video data acquisition system modifies at least a portion of the video data to produce an output signal. Authenticity of the output signal from the video data acquisition system is verified by checking that the video data includes modifications according to the control signal. If the video data does not include such modifications, it is known that the video data acquisition system needs to be checked for tampering or system failures.