System for combining and encoding first plurality of video signals to produce second plurality of signals and transmitting the signals via unshielded telephone cable to remote workstation

• US 5,479,617 A
• Filed: 06/05/1992
• Issued: 12/26/1995
• Est. Priority Date: 06/05/1992
• Status: Expired due to Term

• Current Assignee: Maxpeed Corporation
• Original Assignee: Maxpeed Corporation
• Inventors: Nei, Chu
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): Krick, Rehana
• Application Number:
  US07/894,418
• Time in Patent Office: 1,299 Days
• Field of Search: 395/200, 395/275, 395/100, 395/114, 395/162, 395/163, 395/500, 345/22, 379/100, 379/93, 348/17, 348/6, 382/56
• US Class Current: 710/73
• CPC Class Codes: H04N 21/2365 Multiplexing of several video streams
• CPC Class Codes: H04N 21/2381 Adapting the multiplex stream to a specific network, e.g. an Internet Protocol [IP] network transmission of MPEG streams over ATM H04L12/5601
• CPC Class Codes: H04N 21/4347 Demultiplexing of several video streams
• CPC Class Codes: H04N 21/6137 involving transmission via a telephone network, e.g. POTS
• CPC Class Codes: H04N 7/108 the cable being constituted by a pair of wires

Abstract

A type 286, 386, or 486 Personal Computer having a host controller comprising a standard VGA controller, a microprocessor, a receive and transmit unit, and an encoder is coupled via a ten line telephone cable to a remote VGA color display workstation having a base unit comprising a decoder, a RAMDAC, and microprocessor, and a receive and transmit unit. The encoder intelligently combines ten video signals (a pixel clock, six pixel signals, a video blanking interval (VBI) signal, and vertical and horizontal sync signals) and an I/O data transmit signal into four signals which are transmitted in a balanced fashion (requiring eight lines) to minimize signal noise so that shielding is unnecessary. An additional line is used to provide a ground reference to the remote workstation, and another line is used to provide an I/O data receive signal to the host controller microprocessor. The base unit decoder decodes the balanced signals to provide the I/O transmit signal to the base unit microprocessor, the vertical and horizontal sync signals to the remote workstation VGA monitor, and the VBI and pixel signals to the base unit RAMDAC. Remaining signals required by the base unit RAMDAC are provided by the base unit microprocessor.

Claims

1. Multi-user I/O apparatus for coupling a host personal computer to a plurality of remote workstations having VGA color monitors, said multi-user I/O apparatus comprising:

a host computer controller having, for each of said plurality of remote workstations,

a) a VGA controller producing a first plurality of video signals and a control signal;

b) a data transmit signal generator, comprising a microprocessor and an asynchronous serial communications circuit, receiving a second plurality of video signals and producing a data transmit signal; and

c) an encoder, coupled to said VGA controller and to said data transmit signal generator, for receiving as input said first plurality of video signals and said data transmit signal, said encoder combining and encoding said first plurality of video signals and said data transmit signal to produce a second plurality of digital, balanced pair encoded output signals, said first plurality greater than said second plurality, said encoder alternately representing said first plurality of video signals and said data transmit signal among said balanced pair encoded output signals in response to said control signal; and

a base unit for each of said remote workstations, said base unit including

a) a decoder, coupled to said encoder, for receiving as input and decoding said digital, balanced pair encoded output signals, for reproducing said first plurality of video signals and said data transmit signal;

b) a RAMDAC, coupled to said decoder and to said VGA monitor of said each of said plurality of remote workstations, for receiving as input said reproduced first plurality of video signals and providing analog RGB signals as input to said VGA monitor; and

c) a data receive signal generator, coupled to said host controller;

said base unit processing said data transmit signal, wherein said second plurality of digital, balanced pair encoded output signals and said data receive signal are transmitted digitally via unshielded telephone cable.

2. Multi-user I/O apparatus for coupling a host personal computer to a plurality of remote workstations having VGA color monitors, said multi-user I/O apparatus comprising:

a host computer controller having, for each of said plurality of remote workstations,

a) a VGA controller producing first plurality of video signals;

b) a data transmit signal generator; and

c) an encoder, coupled to said VGA controller and to said data transmit signal generator, for receiving as input said first plurality of video signals and said, data transmit signal, said encoder combining and encoding said first plurality of video signals and said data transmit signal to produce a second plurality of digital, balanced pair encoded output signals, said first plurality greater than said second plurality; and

a base unit for each of said remote workstations, said base unit including

a) a decoder, coupled to said encoders, for receiving as input and decoding said digital, balanced pair encoded output signals, for reproducing said first plurality of video signals and said data transmit signal;

b) a RAMDAC, coupled to said decoder and to said VGA monitor of said each of said plurality of remote workstations, for receiving as input said reproduced first plurality of video signals and providing analog RGB signals as, input to said VGA monitor; and

c) a data receive signal generator, coupled to said host controller;

said base unit processing said data transmit signal, wherein

said second plurality of digital, balanced pair encoded output signals and said data receive signal are transmitted digitally via unshielded telephone cable;

said plurality of video signals comprises a pixel clock signal, six pixel data signals, a video blanking interval signal, a vertical sync signal, and a horizontal sync signal;

said encoder combines said plurality of video signals and said data transmit signal into four balanced pair signals;

said decoder is coupled to said VGA monitor of said each of said plurality of remote workstations, reproduces said pixel clock signal, said six pixel data signals and said video blanking interval signal as input to said RAMDAC, and reproduces said vertical sync signal and said horizontal sync signal as input to said VGA monitor; and

said unshielded telephone cable is ten-line unshielded telephone cable.

3. The multi-user I/O apparatus of claim 2, wherein said base unit microprocessor is coupled to said RAMDAC for writing RGB values to RAMDAC addresses, said RGB values and RAMDAC addresses being received by said base unit microprocessor through said data transmit signal.

4. A method of controlling a workstation including a VGA monitor and a RAMDAC at a location remote from a host computer location, said method comprising the steps of:

a) combining and encoding at said host computer location first and second pluralities of signals required by said remote workstation RAMDAC, producing a set of digital, encoded outputs which alternately represent said first and second pluralities of signals in response to a control signal;

b) digitally transmitting said set of digital, encoded outputs from said host computer location to said remote workstation location in balanced pair, digital format via unshielded ribbon-type cable;

c) decoding said set of digital, encoded outputs at said remote workstation location to re-create said plurality of signals; and

d) providing at least a portion of said re-created signals to said remote workstation RAMDAC, whereby said remote workstation RAMDAC drives said VGA monitor.

5. A method of controlling a workstation including a VGA monitor and a RAMDAC at a location remote from a host computer location, said method comprising the steps of:

a) combining and encoding at said host computer location a plurality of signals required by said remote workstation RAMDAC, producing a set of digital, encoded outputs;

b) digitally transmitting said set of digital, encoded outputs from said host computer location to said remote workstation location in balanced pair, digital format via unshielded ribbon-type cable;

c) decoding said set of digital, encoded outputs at said remote workstation location to re-create said plurality of signals; and

d) providing at least a portion of said re-created signals to said remote workstation RAMDAC, whereby said remote workstation RAMDAC drives said VGA monitor, wherein

the combining and encoding step comprises combining and encoding a pixel clock signal, six pixel data signals, a horizontal sync signal, a vertical sync signal, a video blanking interval signal, and a data transmit signal, and said set of digital, encoded output comprises four encoded outputs;

the transmitting step comprises transmitting via ten-line telephone cable; and

the decoding step comprises decoding said encoded outputs at said remote workstation location to re-create said clock signal, said six decoded pixel data signals, said horizontal sync signal, said vertical sync signal, said video blanking interval signal, and said transmit data signal; and

the providing step comprises providing said re-created clock signal, said re-created six pixel data signals, and said re-created video blanking interval signal to said remote workstation RAMDAC, and providing said re-created horizontal sync signal and said re-created vertical sync signal to said VGA monitor.

6. The method of claim 5 wherein before said step of combining and encoding is performed, the following step is performed:

converting RAMDAC addresses and RGB values into a bitstream signal as said data transmit signal, and said decoding step further comprises

re-creating said RAMDAC addresses and said RGB values from said data transmit stream, and providing said re-created RAMDAC addresses and RGB values to said RAMDAC.

7. An I/O apparatus for coupling a host personal computer to a remote workstation having a VGA color monitor, said I/O apparatus comprising:

a host computer controller having

a) a VGA controller producing a first plurality of video signals and a control signal;

b) a data transmit signal generator, comprising a microprocessor and an asynchronous communications circuit, receiving a second plurality of video signals and producing a data transmit signal; and

c) an encoder, coupled to said VGA controller and to said data transmit signal generator, for receiving as input said first plurality of video signals and said data transmit signal, said encoder combining and encoding said first plurality of video signals and said data transmit signal to produce a second plurality of digital, balanced pair encoded output signals, said first plurality greater than said second plurality, said encoder alternately representing said first plurality of video signals and said data transmit signal among said balanced pair encoded output signals in response to said control signal; and

a base unit including

a) a decoder, coupled to said encoder, for receiving as input and decoding said digital, balanced pair encoded output signals, for reproducing said first plurality of video signals and said data transmit signal;

b) a RAMDAC, coupled to said decoder and to said VGA monitor, for receiving as input said reproduced first plurality of video signals and providing analog RGB signals as input to said VGA monitor; and

c) a data receive signal generator, coupled to said host controller, for producing a data receive signal as input to said host controller;

said base unit processing said data transmit signal, wherein said second plurality of balanced pair encoded output signals and said data receive signal are transmitted digitally via unshielded telephone cable.