DIGITAL TELEVISION TRANSMISSION SYSTEM

• US 3,795,763 A
• Filed: 04/18/1972
• Issued: 03/05/1974
• Est. Priority Date: 04/18/1972
• Status: Expired due to Term

• Current Assignee: Bruce J. Merrihew, Henry F. Mueller, Leonard S. Golding, Marvin D. Ginsberg, Melville L. Heiges Jr, Pradman P. Kaul, Ronald K. Garlow, Wilfred G. Maillet
• Original Assignee: Bruce J. Merrihew, Henry F. Mueller, Leonard S. Golding, Marvin D. Ginsberg, Melville L. Heiges Jr, Pradman P. Kaul, Ronald K. Garlow, Wilfred G. Maillet
• Inventors: Golding, Leonard S., Garlow, Ronald K., Ginsberg, Marvin D., Maillet, Wilfred G., Kaul, Pradman P., Heiges, Melville L. Jr., Merrihew, Bruce J., Mueller, Henry F.
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US05/245,129
• Time in Patent Office: 686 Days
• Field of Search: 178/5.2R,6.8,DIG.3,DIG.22,DIG.23,7.1,7.2,5.4R 179/15BW,155ST,2TV 325/38B
• US Class Current: 375/240.01
• CPC Class Codes: H04N 11/046 DPCM
• CPC Class Codes: H04N 21/236 Assembling of a multiplex stream, e.g. transport stream, by combining a video stream with other content or additional data, e.g. inserting a URL [Uniform Resource Locator] into a video stream, multiplexing software data into a video stream; Remultiplexing of multiplex streams; Insertion of stuffing bits into the multiplex stream, e.g. to obtain a constant bit-rate; Assembling of a packetised elementary stream multiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 21/434 Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream demultiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00

Abstract

A digital television transmission system for transmitting television signals at substantially reduced bit rate and bandwidth. Frequency interleaving techniques reduce the sampling rate,and digital differential PCM with edge recoding techniques reduce the number of bits per sample. Further, reduction in bit rate is accomplished by eliminating approximately half the chrominance data and all the sync pulses from the transmitted signal. Periodic sync words are transmitted to allow reconstruction of the sync pulse format at the receiver. All transmitted bits are multiplexed in accordance with a particular format which provides proper alignment of the luminance and chrominance lines at the receiver.

Claims

1. A digital transmission system for television signals comprising, a. means responsive to a composite video signal for separating said signal into its luminance component, first and second chrominance components, and its vertical and horizontal sync pulses, b. luminance channel processing means responsive to said luminance component for converting every line of said luminance component into digital representations thereof and storing said digital luminance lines, c. first chrominance channel processing means responsive to said first chrominance component for converting the lines of said first chrominance component into digital representations thereof and storing those said digital representations representing every other pair of successive lines of said first chrominance component, d. second chrominance channel processing means responsive to said second chrominance component for converting the lines of said second chrominance component into digital representations thereof and storing those said digital representations representing every other pair of successive lines of said second chrominance component, e. audio channel processing means responsive to an audio signal associated with said composite video signal for digitally converting said audio signal and for storing said digital audio signal, f. a sync word generator means, and g. means responsive to every Nth horizontal sync pulse for actuating said sync word generator and reading out data from said luminance, chrominance and audio channels in a preestablished sequence to provide a multiplexed serial bit stream comprising in a repetitive format of at least one sync word, N digital luminance lines, N/2 digital chrominance lines, and digital audio representing analog audio over an N line duration.

2. A digital transmission system as claimed in claim 1 wherein said luminance channel processing means comprises, a. luminance signal sampling means for pulse amplitude sampling said luminance componate at a sample rate less than the Nyquist rate for said luminance components and equal to an odd multiple of half the horizontal line frequency, b. luminance quantizing means for quantizing said luminance samples into digiTal luminance samples, c. luminance digital differential PCM means with edge recoding responsive to said digital luminance samples for generating digital respresentations of the difference between successive samples, said digital representations having fewer bits than said digital samples, d. luminance buffer storage means for storing the luminance date outputs from said luminance digital differential PCM means, and e. luminance write control means for writing the output data from said luminance digital differential PCM means into said luminance buffer.

3. A digital transmission system as claimed in claim 2 wherein each of said first and second chrominance channel processing means comprises, a. chrominance signal sampling means for pulse amplitude sampling said chrominance component at sample rates less than the Nyquist rate for said chrominance component and equal to an odd multiplex of half the horizontal line frequency, b. chrominance quantizing means for quantizing said chrominance samples into digital chrominance samples, c. chrominance digital differential PCM means with edge recoding responsive to said digital chrominance samples for generating digital representations of the difference between successive samples, said digital representations having fewer bits than said digital samples, d. chrominance buffer storage means for storing the chrominance data written therein, and e. chrominance write control means for writing every other pair of chrominance output data from said chrominance digital differential PCM into said chrominance buffer storage.

4. A digital transmission system as claimed in claim 3 wherein said means responsive to every Nth horizontal sync pulse comprises, a. transmitter frame counter means adapted to count locally generated output bit rate clock pulses and to be reset by every Nth horizontal sync pulse, b. means responsive to said transmit frame counter for reading out, in nonoverlapping sequence during each cycle of said frame counter, N lines of luminance data from said luminance buffer storage means, N/2 lines of data from the chrominance buffer storage means of said first chrominance channel processing means, N/2 lines of data from the chrominance buffer storage means of said second chrominance channel processing means, and N groups of bits from said audio channel storing means, c. means responsive to a predetermined count in said transmitter frame counter for actuating said sync word generator to generate a group of bits representing a sync word, and d. means for serially combining said sync word, said N groups of audio bits, said N lines of luminance and said N/2 lines of both chrominance components.

5. A digital transmission system as claimed in claim 4 further comprising receiver means adapted to receive data in the same format as appears at the output of said serial combining means for converting said data into composite video and related audio analog signals.

6. A digital transmission system as claimed in claim 5 wherein said receiver means comprises, a. means for detecting said sync words in a received data format and generating sync detect pulses in response thereto, b. receiver frame counter means adapted to count clock pulses at the bit rate of said received data formate and to be reset by said sync detect pulses, c. demultiplexing means responsive to said receiver frame counter for separating the audio, luminance, first chrominance, and second chrominance bits appearing in said received data format from each other, d. receiver luminance channel processing means responsive to said separated out luminance bits for reconverting said luminance bits into an analog luminance component, e. first receiver chrominance channel processing means responsive to said separated out first chrominance bits for reconstructing the missing lines of said first chrominance component and reconverting said chrominanCe bits and said reconstructed lines into a first analog chrominance component, f. second receiver chrominance channel processing means responsive to said separated out second chrominance bits for reconstructing the missing lines of said second chrominance component and reconverting said chrominance bits and said reconstructed lines into a second analog chrominance component, g. means responsive to said sync detect pulses and said frame counter for reconstructing the horizontal and vertical sync pulses and a chrominance subcarrier frequency for a composite video signal, h. composite color television encoder means responsive to said reconstructed analog luminance and chrominance signals, said vertical and horizontal sync pulses, and said color subcarrier frequency, for forming a composite video signal, and i. receiver audio channel processing means responsive to said separated out audio bits for reconverting said audio bits into an analog audio signal.