# US 5,347,305 A · Video telephone system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,347,305 A - Document ID: US5347305A - Status: Granted - Kind: A - Application number: 07/628,607 - Filed: 1990-12-17 - Granted: 1994-09-13 - Earliest claimed: 1990-02-21 - Assignees: Alkanox Corporation - Inventors: Daniel R. Bush; Ashok Patel; Charlie W. Zetterower - Web page: https://patentgrep.com/patent/US5347305A ## CPC - H04N 21/2368: Multiplexing of audio and video streams - G10L 19/00: Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis (in musical instruments G10H) - H04N 7/148: {Interfacing a video terminal to a particular transmission medium, e.g. ISDN} - H04N 19/00: Methods or arrangements for coding, decoding, compressing or decompressing digital video signals - H04N 19/61: in combination with predictive coding - H04N 19/619: {the transform being operated outside the prediction loop} - 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)} - H04N 21/242: Synchronisation processes, e.g. processing of PCR [Programme Clock References] {(arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18)} - H04N 21/4302: {Content synchronisation processes, e.g. decoder synchronisation} - 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)} - H04N 21/4341: {Demultiplexing of audio and video streams} - H04N 21/6137: {involving transmission via a telephone network, e.g. POTS} - H04N 21/6187: {involving transmission via a telephone network, e.g. POTS} - G10L 19/04: using predictive techniques - H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract Apparatus and method are provided for the simultaneous transmission of video information and audio information in substantially real time over an ordinary voice grade telephone line having limited bandwidth in the range of about 300-3400 Hz. Because of the limited bandwidth of the ordinary telephone line, the video and audio information are compressed before transmission thereof. Each of the video information and audio information is separately compressed, mixed together and then further compressed. After the further compression, a composite signal, which includes the mixture of video and audio information, is asynchronously transmitted over the same bandwidth of the ordinary telephone line. Upon reception, the compressed information is expanded and separate video information and audio information are reproduced for viewing and hearing by the receiving party. To reduce the size of the apparatus, application specific integrated circuits (ASICs) are employed. A state machine controller apparatus is integrated with the ASIC technology to control the transfer and storing of video information and audio information and also to control the operation of the various compression and expansion stages associated with the transmitting and receiving channels. ## Claims ### Claim 1 A method for transmitting and receiving video and audio signals over an ordinary telephone line in substantially real time, comprising: generating at a transmitting station a video signal having video information, said generating step including providing first means having a number of pixels together comprising a frame and wherein said video signal is generated using a number of frames with an updating of frames being provided at a rate of about 7.5 frames per second; generating at said transmitting station an audio signal having audio information; producing a composite video/audio signal wherein said composite signal includes a mixture of compressed video information and compressed audio information, with said video and audio information being provided to form said composite signal in a manner that permits accurate restoration thereof at a receiver station and proper synchronization of said video information and said audio information, said step of producing including compressing said video information and separately compressing said audio information; modulating said composite signal; transmitting said modulating composite signal using an ordinary telephone line having a limited band width; receiving said modulated composite signal at a receiving station after having been sent over the ordinary telephone line; demodulating said modulated composite signal; and reproducing said video information and said audio information at the receiving station using said composite signal. ### Claim 2 (depends on 1) A method, as claimed in claim 1, wherein: said limited bandwidth of the ordinary telephone line is about 3100 Hz. ### Claim 3 (depends on 1) A method, as claimed in claim 1, wherein: said compressed video information and compressed audio information are provided using at least a first state machine means and ASIC means. ### Claim 4 (depends on 1) A method, as claimed in claim 1, wherein: said step of producing includes using a linear predictive coding apparatus to provide compressed audio information. ### Claim 5 (depends on 4) A method, as claimed in claim 4, wherein: said step of producing includes using correlation function generator means for determining at least one of: predictor coefficients, pitch period and gain associated with said audio information. ### Claim 6 (depends on 5) A method, as claimed in claim 5, wherein: said step of producing includes determining a pitch period associated with a predetermined number of samples of said audio information. ### Claim 7 (depends on 5) A method, as claimed in claim 5, wherein: said step of producing includes determining whether said audio information is voiced or unvoiced. ### Claim 8 (depends on 5) A method, as claimed in claim 5, wherein: said step of producing includes determining said gain factor using at least some of said audio information and said pitch period. ### Claim 9 (depends on 5) A method, as claimed in claim 5, wherein: said step of producing includes determining said predictor coefficients using recursively solved equations and correlation function generator means. ### Claim 10 (depends on 5) A method, as claimed in claim 5, wherein: said step of producing includes comparing sampled audio information with a threshold value to generate a sequence of values for use in determining said pitch period. ### Claim 11 (depends on 5) A method, as claimed in claim 5, wherein: said step of producing includes correlating samples of said audio information to provide an output used in determining whether said audio information is voiced or unvoiced. ### Claim 12 (depends on 1) A method, as claimed in claim 1, wherein: said step of producing includes controlling the sending of said compressed audio information and said compressed video information using state machine means. ### Claim 13 (depends on 1) A method, as claimed in claim 1, wherein: said step of transmitting includes using substantially the same bandwidth to send both said video information and said audio information. ### Claim 14 (depends on 1) A method, as claimed in claim 1, wherein: said step of transmitting includes asynchronously sending said modulated composite signal. ### Claim 15 (depends on 1) A method, as claimed in claim 1, wherein: said step of reproducing includes inputting at said receiver station at least one of the following: predictor coefficients, pitch period and gain factor. ### Claim 16 (depends on 15) A method, as claimed in claim 15, wherein: said step of reproducing includes controlling at least one of an impulse generator means and a random noise generator means, depending upon whether said audio information is voiced or unvoiced. ### Claim 17 (depends on 16) A method, as claimed in claim 16, wherein: said step of reproducing includes using at least one of the value of said pitch period and state machine means to control transmission from said impulse generator means and said random noise generator means. ### Claim 18 (depends on 16) A method, as claimed in claim 16, wherein: said step of reproducing includes outputting a train of impulses from said impulse generator means having a pitch period corresponding to said determined pitch period. ### Claim 19 (depends on 16) A method, as claimed in claim 16, wherein: said step or reproducing includes outputting an aperiodic signal from said random noise generator means when said audio information is unvoiced. ### Claim 20 (depends on 16) A method, as claimed in claim 16, wherein: said step of reproducing includes inputting an output from one of said impulse generator means and said random noise generator means to gain factor circuit means for controlling the gain associated with an inputted signal. ### Claim 21 (depends on 20) A method, as claimed in claim 20, wherein: said step of reproducing includes inputting said gain factor to said gain factor circuit means. ### Claim 22 (depends on 15) A method, as claimed in claim 15, wherein: said step of reproducing includes inputting said predictor coefficients to time-varying digital filter means and using said predictor coefficients to restore said compressed audio information. ### Claim 23 An apparatus for substantially simultaneously transmitting and receiving video and audio signals over an ordinary voice grade telephone line, comprising: first means for generating video information; second means for generating audio information; third means for producing compressed video information and compressed audio information for transmission, in substantially real time, over an ordinary voice grade telephone line having a limited bandwidth in the range of about 300-3400 Hz, said third means includes means for producing said compressed audio information separately from means for producing said compressed video information, wherein said step of producing includes compressing said video information by a factor of at least 57 times and compressing said audio information by a factor of at least 42 times; fourth means for reproducing video information and audio information from said compressed video information and said compressed audio information after transmission thereof; fifth means for displaying images using said video information; and sixth means for generating sounds using said audio information. ### Claim 24 (depends on 23) An apparatus, as claimed in claim 23, wherein: said third means includes means for providing a composite signal having said video information and said audio information mixed together in a manner that permits accurate restoration thereof and proper synchronization between said video information and said audio information at a receiving station. ### Claim 25 (depends on 24) An apparatus, as claimed in claim 24, wherein: said third means includes modulator means in which said composite signal is used to modulate a first carrier wave. ### Claim 26 (depends on 25) An apparatus, as claimed in claim 25, wherein: said modulated carrier wave is asynchronously transmitted over the ordinary voice grade telephone line. ### Claim 27 (depends on 23) An apparatus, as claimed in claim 23, wherein: said third means includes means for providing a single data stream of said compressed video information and said compressed audio information wherein both said compressed video information and said compressed audio information are adapted to be transmitted using the same bandwidth over the ordinary voice grade telephone line. ### Claim 28 (depends on 23) An apparatus, as claimed in claim 23, wherein: said third means includes means for correlating samples of said audio information. ### Claim 29 (depends on 28) An apparatus, as claimed in claim 28, wherein: said third means includes predictor coefficient calculator means for receiving outputs from said means for correlating and for determining predictor coefficients associated with said audio information using recursively solved equations. ### Claim 30 (depends on 23) An apparatus, as claimed in claim 23, wherein: said third means includes pitch period detecting means for determining a value of pitch period associated with a predetermined number of samples of said audio information. ### Claim 31 (depends on 30) An apparatus, as claimed in claim 30, wherein: said third means includes means for determining whether said audio information is voiced or unvoiced. ### Claim 32 (depends on 30) An apparatus, as claimed in claim 30, wherein: said third means includes gain factor determinator means for determining a gain factor associated with said audio information. ### Claim 33 (depends on 23) An apparatus, as claimed in claim 23, wherein: said third means includes a linear predictive coding apparatus that includes a linear predictive coding coder and a linear predictive coding decoder. ### Claim 34 (depends on 33) An apparatus, as claimed in claim 33, wherein: said linear predictive coding decoder includes impulse generator means for receiving a value of pitch period associated with audio information for outputting an impulse train having a pitch period corresponding to said pitch period value. ### Claim 35 (depends on 33) An apparatus, as claimed in claim 33, wherein: said linear predictive coding decoder includes random noise generator means for outputting a substantially aperiodic signal when unvoiced audio information is being receiving by said decoder. ### Claim 36 (depends on 33) An apparatus, as claimed in claim 33, wherein: said linear predictive coding decoder includes gain factor circuit means for receiving a magnitude of gain factor and outputting a digital signal having a waveform dependent upon whether audio information is voiced or unvoiced and an amplitude depending upon the magnitude of said gain factor. ### Claim 37 (depends on 33) An apparatus, as claimed in claim 33, wherein: said linear predictive coding decoder includes time-varying filter digital means for receiving predictor coefficients and for outputting synthesized audio information that substantially represents said audio information generated by said second means.