US 5,347,305 A · Video telephone system

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.

Claims37

Dependent claims

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.

6 more elements

Dependencies are inferred from the claim text.

Video telephone system

Life of this patent

Video telephone system

Life of this patent

Abstract

Claims37