A circuit arrangement for controlling audio signal transmissions for a
communications system that includes a microphone and a video camera. The
arrangement comprises a video processor configured and arranged to
receive a video signal from the video camera, detect movement of an
object in the video signal, and provide a motion-indicating signal
indicating movement relative to the object. An audio processor is coupled
to the video processor and is configured and arranged to modify the audio
signal to be transmitted responsive to the motion-indicating signal. In
another embodiment, a video signal processor is configured and arranged
to receive a video signal from the video camera, detect mouth movement of
a person and provide a mouth-movement signal indicative of movement of
the person's mouth. An echo-cancellation circuit is coupled to the video
signal processor and configured and arranged to filter from an audio
signal provided by the microphone sound energy output by the speaker
responsive to the mouth-movement signal.