Bell Telephone Laboratories

At&t Bell Laboratories

Bell Communications Research, Inc.

Earl F Brown

John Ormond Limb

Arun N Netravali

Alan M Gordon

Arthur B Larsen

Birendra Prasada

Robert Lewis Eilenberger

Robert V Kline

John Francis Moran

Pat Le Gordon

A telecommunications interface is disclosed. The inventive telecommunications interface is capable of collecting multiple asynchronous video, audio, graphic and data signals from a variety of different kinds of sources and retransmitting such signals in a suitable form for display or detection with one or more types of receiver equipment at one or more locations. The interface operates at rates ranging from several hundred bits per second to several gigabits per second. The telecommunications interface includes a dual port RAM whose input and output operate asynchronously. Signals from the user sources are stripped of timing and source identification information and are written into the dual port RAM, while output processors read previously stored user signals out from the dual port RAM. The output processor appropriately format the retrieved signals, which are then transmitted to the receiver equipment.

Telecommunications interface

A video display touch detection digitizer for generating the coordinate position when the video display is touched. The light signals for the X and Y coordinate array are generated from the raster scan signals of the video display during selected periods of the vertical and horizontal blanking intervals. Vertical and horizontal mirrors reflect, respectively, the resulting row and columns of light signals across the screen of the video display where other mirrors reflect the signals to, respectively, row and column signal detectors. Control circuitry detects the resulting interruption in the rows and columns of light signals when the screen of the video display is touched and generates signals representing the touch coordinates.

Video display touch detection digitizer

A bandwidth reduced teleconferencing system achieving good video presence. The bandwidth reduction is accomplished by dividing the video picture of the camera into segments, by determining the activity level within each segment and by transmitting the signal of each segment with a resolution level which is related to the activity level within the segment. The most active segment is transmitted at highest resolution while other segments are transmitted at lower resolutions.

Reduced bandwidth video transmission

An interactive graphics transmission system for use, illustratively, in video teleconferencing is described which advantageously reduces the amount of transmission bandwidth and user effort required to transmit changing graphical information. This is accomplished by first transmitting a full image of the graphic followed only by the changes which a conferee makes to that graphic. Those changes are determined by sensing the tilt of a light pen and the location of its tip, which is closest to the graphic, as a conferee manipulates the pen to change the graphic. The tilt of the pen primarily determines the mode in which the light pen is used. The mode information, in conjunction with the location of the pen's tip, is used to generate an instruction which specifies the way in which the graphic is to be changed, e.g., whether information is to be added to, deleted from or emphasized in a graphic. In addition, the location of the pen's tip specifies the address of that portion of the graphic that is to be changed. By transmitting just the instruction and address information while the user simultaneously manipulates the light pen to change a graphic, transmission bandwidth and user effort are both advantageously minimized.

Interactive graphics transmission system employing an adaptive stylus

Supplementary digital data is encoded together with a video signal by predicting the intensity values of a first set of video samples, compressing the range of the prediction errors and superimposing a value indicative of the supplementary data on the compressed value. The samples in the first set may be selected in a regular sequence or asynchronously in accordance with a function of the video signal such as the slope in the area of the picture being processed; the composite values are time multiplexed with the remaining intensity values.

Technique for transmitting digital data together with a video signal

Video conferencing, wherein the outputs of a plurality of television cameras at one location are transmitted to a second location so that parties at the first location are perceived as present by parties at the second location, has received some attention directed toward bandwidth reduction. The subject invention relates to an improved video conferencing system for reducing bandwidth by advantageously applying temporal resolution and spatial reduction to a video picture provided by each camera. The temporal resolution of a picture from one or more of the cameras can be automatically adapted to a control signal, for example, to a speech level control signal so as to advantageously interleave and to give priority to a picture from one camera over a picture from other television cameras. The spatial reduction of each picture obtains by transmitting and displaying less than the total picture, illustratively the middle two-thirds of the picture from each camera.

Video conferencing system using spatial reduction and temporal resolution

A pulse code modulator utilizes a predetermined bit, which is the least significant bit in each code group, to indicate the polarity of the signal amplitude sample whose magnitude is represented by the immediately succeeding code group. Since variations in magnitude change the value of the predetermined bit in a more or less random fashion and the same is true of the polarity of the samples to be encoded, in the course of the encoding process there is a relatively high probability of occasions when the magnitude and polarity will call for the same value of bit. When there is a disagreement in bit value for the magnitude and polarity, the predetermined bit in each code group is forced to indicate the correct polarity. Additional bits in each of these code groups may also be changed to provide the most accurate magnitude information with the corrected polarity information.

Digital coding without additional bits to provide sign information

Alternate lines of a 526 line video signal are time-stretched and transmitted over a transmission channel of limited bandwidth. At the receiver, the lines are compressed back to their original duration and displayed in an interlaced manner on a conventional receiver by blanking alternate lines in each field. In another embodiment of the invention, adjacent transmitted lines of the video signal are averaged at the receiver and the resultant signals are substituted for the non-transmitted lines of the video signal.

Growing community of inventors

Piscataway, NJ, United States of America

Earl F Brown