US 5,175,617 AGranted

Telephone line picture transmission

AssigneeVision Applications, Inc.

InventorsRichard S. Wallace, Benjamin B. Bederson, Eric L. Schwartz

Life of this patent

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Abstract

A system and method is provided to transmit logmap video images through telephone line band-limited analog channels. The pixel organization in the logmap image is designed to match the sensor geometry of the human eye with a greater concentration of pixels at the center. The transmitter divides the frequency band into channels, and assigns one or two pixels to each channel, for example a 3KHz voice quality telephone line is divided into 768 channels spaced about 3.9Hz apart. Each channel consists of two carrier waves in quadrature, so each channel can carry two pixels. Some channels are reserved for special calibration signals enabling the receiver to detect both the phase and magnitude of the received signal. If the sensor and pixels are connected directly to a bank of oscillators and the receiver can continuously receive each channel, then the receiver need not be synchronized with the transmitter. An FFT algorithm implements a fast discrete approximation to the continuous case in which the receiver synchronizes to the first frame and then acquires subsequent frames every frame period. The frame period is relatively low compared with the sampling period so the receiver is unlikely to lose frame synchrony once the first frame is detected. An experimental video telephone transmitted 4 frames per second, applied quadrature coding to 1440 pixel logmap images and obtained an effective data transfer rate in excess of 40,000 bits per second.

Claims34

Dependent claims

A method for transmitting on communication channels an original logmap video image stored in the memory of a transmitting unit, and then reproducing a reproduced logmap video image from the memory of the receiving unit;

the method including the steps of:
a) reducing a normal TV image composed of pixels to a logmap video image composed of fewer pixels by mapping selected groups of TV image pixels to a corresponding single logmap video pixel;
b) storing the luminance intensities of the logmap video pixels in digital computer memory of a transmitter wherein each said computer memory location is associated with the location of a particular logmap video pixel;
c) mapping the pixel intensities of the logmap video image stored in the memory of the transmitter to a series of at least 100 carrier waves of different frequencies within the bandwidth of the said communication channel, said mapping being performed in computer memory where the pixel intensity modulates the amplitude of a carrier wave at a given frequency;
d) summing together the individual waves, and calculating a time varying analog signal, s(t), which is the sum of said waves, said signal s(t) being stored as digital values in computer memory of the transmitter;
e) converting digital signal values of s(t) to analog signal values and outputting them to said communication channel;
f) sampling the analog signal on the communication channel at the receiving unit and storing the sampled values in computer memory of receiver as digital values;
g) deriving from the sampled values of s(t) stored in receiver memory, a spectrum of waves, where the amplitudes and frequencies of the derived waves correspond to the original waves summed by the transmitter;
h) recreating the logmap video image in computer memory of the receiver where the frequency of the waveform determines the location of each pixel and the amplitude of the waveform determines pixel intensity, and
i) displaying the logmap video image stored in receiver memory on a TV screen.

7 more elements

A system for transmitting on communication channels an original logmap video image stored in the memory of a transmitting unit, and then reproducing a reproduced logmap video image from the memory of the receiving unit;

the system comprising:
a) means for reducing a normal TV image composed to a logmap video image composed of fewer pixels by mapping selected groups of TV image pixels to a corresponding single logmap video pixel;
b) means for storing the luminance intensities of the logmap video pixels in digital computer memory of a transmitter wherein each said computer memory location is associated with the location of a particular logmap video pixel;
c) means for mapping the pixel intensities of the logmap video image stored in the memory of the transmitter to a series of at least 100 carrier waves of different frequencies within the bandwidth of the said communication channel, said mapping being performed in computer memory where the pixel intensity modulates the amplitude of a carrier wave at a given frequency;
d) means for summing together the individual waves, and calculating a time varying analog signal, s(t), which is the sum of said waves, said signal s(t) being stored as digital values in computer memory of the transmitter;
e) means for summing digital signal values of s(t) to analog signal values and outputting them to said communication channel;
f) means for sampling the analog signal on the communication channel at the receiving unit and storing the sampled values in computer memory of receiver as digital values;
g) means for deriving from the sampled values of s(t) stored in receiver memory, a spectrum of waves, where the amplitudes and frequencies of the derived waves correspond to the original waves summed by the transmitter;
h) means for recreating the logmap video image in computer memory of the receiver where the frequency of the waveform determines the location of each pixel and the amplitude of the waveform determines pixel intensity, and
i) means for displaying the logmap video image stored in receiver memory on a TV screen.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/802,328Filed 4 Dec 1991
Granted: 29 Dec 1992
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H04N 21/2383
Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth;…: channel…
H04N 7/12
Television systems: systems in which the television signal is transmitted via one channel or a plurality of parallel channels, the bandwidth of…
H04N 7/127
Systems in which the television signal is transmitted via one channel or a plurality of parallel channels, the bandwidth of each channel being…:…
H04N 19/00
Methods or arrangements for coding, decoding, compressing or decompressing digital video signals