Abstract: An audio processing system for use in teleconferencing systems having high and low transmission delays. The audio processing system utilizes complementary comb filters in combination with auxiliary echo suppressors, a frequency scaler, expander/gates and automatic level controlling devices to substantially improve acoustic stability margin and reduce far-end talker echo.

Abstract: A teleconferencing system 100 is disclosed having a video camera for generating a video signal representative of a video image of a first station B. A microphone array 150, 160 is also provided in the first station for receiving a sound from one or more fixed non-overlapping volume zones 151, 152, 153, 154, 155, 156, 157, 158, 159, into which the first station is divided. The microphone array is also provided for generating a monochannel audio signal 170 representative of the received sound and a direction signal indicating, based on the sound received from each zone, from which of the volume zones the sound originated. The teleconferencing system also includes a display device 120A at a second station A for displaying a video image of the first station.

Abstract: A teleconferencing system (100, 100') provides a wide aspect ratio view at each site utilizing a single NTSC camera (250, 350) and projector (260,360). At the transmitting end of a teleconference, a transformation element (280, 380, 510, 610) maps a wide aspect ratio field of view into the field of view of an NTSC camera. The transformation is reversed at the receiving end of the teleconferencing system.

Abstract: An audio processing system (100) for use in a teleconferencing system (10) utilizes complementary comb filters (42, 52, 220, 320) in combination with an echo suppressor (210, 310) and/or a frequency scaler (60, 120) to substantially improve acoustic stability margin and reduce far-end talker echo.

Abstract: A method and apparatus for reducing the bit error probability of data transmitted over a Rayleigh fading channel are disclosed.A relatively high bit rate serial stream of data is divided into N parallel relatively low bit rate streams of data. A controlled amount of intersymbol interference is introduced in the parallel streams. The N parallel streams are then transmitted simultaneously over the Rayleigh fading channel. Each bit in the N parallel stream of data has a duration longer than the duration of the typical Rayleigh fade. Thus there is a reduced probability that a Rayleigh fade will cause a bit error.