Videophone for simultaneous audio and video communication via a standard telephone line

• US 5,541,640 A
• Filed: 04/19/1995
• Issued: 07/30/1996
• Est. Priority Date: 06/23/1992
• Status: Expired due to Term

• Current Assignee: Videophone Technologies, LLC
• Original Assignee: Craig R. Larson
• Inventors: Larson, Craig R.
• Primary Examiner(s): Chan, Wing F.
• Application Number:
  US08/424,729
• Time in Patent Office: 468 Days
• Field of Search: 379/96-99, 379/93, 348/14, 348/16-19, 348/22, 348/384
• US Class Current: 348/14.15
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 7/142 Constructional details of the terminal equipment, e.g. arrangements of the camera and the display
• CPC Class Codes: H04N 7/148 Interfacing a video terminal to a particular transmission medium, e.g. ISDN

Abstract

A videophone includes a video camera for transducing and digitizing images at a station and connected to a video processor for compressing and encoding the digitized images into video data and an audio transducer and digitizer connected to an audio processor synchronized with the video processor for compressing and encoding digitized sound. The video and audio processors are connected to a communication controller for formatting and transmitting the video data bundled with the audio data via a standard bidirectional (full duplex) telephone line in the form of a twisted pair. The communication controller can also receive and then unformat and unbundle audio and video data, and the video processor and audio processor can decode and decompress the received video and audio data, and the station further includes a display connected to the video processor for reproducing images and an electroacoustic transducer connected to the audio processor for reproducing sounds transmitted by another station. Rather than format and transmit only delayed or partial changed video data when the image changes significantly, the large amount of changed video data being stored is overwritten when the amount reaches a predetermined level, and new video data corresponding to the present appearance of the image is compressed, encoded, bundled with associated audio data, formatted, and transmitted. The image reproduced at the receiving station therefore jumps ahead to an updated image without intervening blurred images.

Claims

1. A method for communicating audio and motion video simultaneously via a standard bidirectional (full duplex) telephone line in the form of a twisted pair in which video data is transmitted to produce a displayed moving image which is not blurred, comprising the steps of:

transducing and digitizing images;

compressing and encoding the digitized images into video data;

storing the video data until the video data is formatted and transmitted;

detecting when the capability to transmit all of the stored video data to reproduce a current image exceeds the time period allotted for transmission via the standard telephone line;

replacing the stored video data with new video data corresponding to the present appearance of the image when the amount of stored video data reaches a predetermined level;

formatting and transmitting the new video data via the standard telephone line;

receiving the new video data via the standard telephone line;

unformatting and unbundling the received new video data;

decoding and decompressing the received new video data; and

reproducing images based on the decoded and decompressed new video data so that the reproduced image jumps ahead to an updated image without intervening blurred images;

thereby enabling clear motion images to be reproduced.

2. The method of claim 1 wherein the step of replacing the stored video data comprises overwriting the stored video data with the new video data corresponding to the present appearance of the image.

3. The method of claim 2 wherein the step of overwriting the stored video data comprises overwriting the stored video data with I-frame video data corresponding to the present appearance of the image.

4. Apparatus for communicating audio and video simultaneously via a standard bidirectional (full duplex) telephone line in the form of a twisted pair, comprising:

video camera means for transducing and digitizing images;

video processing means connected to the video camera means for compressing and encoding an initial digitized image to produce video data and storing the video data, the video processing means for detecting a change in a subsequent digitized image with respect to the initial digitized image and for compressing and encoding the change in the digitized image to produce changed video data and storing the changed video data;

means for transducing and digitizing sound that is present when the images are being transduced and digitized;

audio processing means connected to the means for transducing and digitizing sound for compressing and encoding digitized sound into audio data and storing the audio data, operation of the audio processing means being synchronized with operation of the video processing means; and

a communication controller connected to the video processing means and the audio processing means for formatting and transmitting the stored audio data bundled with the stored video data via the standard telephone line at a synchronous data transmission rate less than 56 kilobits per second;

the video processing means for detecting when the amount of video data that is stored reaches a predetermined level such that the amount of changed video data exceeds the capability to transmit the changed video data within a time period allotted for transmission via the standard telephone line to produce a current image;

the video processing means for discontinuing the storage of changed video data when the predetermined level is reached and producing video data for a subsequent current image and storing the subsequent current video data so that the amount of video data that is stored does not reach the predetermined level.

5. The apparatus of claim 4 wherein the video processing means dumps the changed video data for the current image and overwrites stored video data with I-frame video data for the subsequent current image when the predetermined level is reached.

6. The apparatus of claim 4 wherein the communication controller receives audio and video data via the standard telephone line and then unformats and unbundles the audio and video data and wherein the audio processing means and the video processing means decode and decompress the audio and video data, respectively, and further comprising:

means connected to the video processing means for reproducing images based on the decoded and decompressed video data; and

electroacoustic transducer means connected to the audio processing means for reproducing sound based on the decoded and decompressed audio data.

7. The apparatus of claim 6 wherein the means for reproducing images comprises a color liquid crystal display (LCD).

8. The apparatus of claim 7 wherein the color liquid crystal display (LCD) is a 128×

112 pixel display.

9. The apparatus of claim 6 wherein the video camera means and the means for reproducing images are mounted in a tiltable swivel housing.

10. The apparatus of claim 4 wherein the video camera means is a color charge coupled device (CCD) camera.

11. The apparatus of claim 4, further comprising a mechanical shutter adjacent to the video camera means and selectively actuable by a person to obstruct the video camera means to enable the person to have privacy when privacy is desired.

12. The apparatus of claim 4 wherein the video processing means comprises:

an input pixel buffer having an input pixel bus connected to the video camera means and an output;

a vision controller having an input interfaced to the output of the input pixel buffer and first, second, and third bidirectional busses;

a vision processor connected to the first bidirectional bus of the vision controller;

a memory buffer having an input interfaced to the second bidirectional bus of the vision controller and also having a memory interface; and

a memory connected to the memory interface of the memory buffer;

the communication controller being interfaced to the third bidirectional bus of the vision controller.

13. The apparatus of claim 12 wherein the audio processing means comprises:

a microphone having an output;

an analog-to-digital converter having an input connected to the output of the microphone and an output; and

a digital audio signal processor having an input interfaced to the output of the analog-to-digital converter and also having a bidirectional bus;

the communication controller being interfaced to the bidirectional bus of the digital audio signal processor.

14. The apparatus of claim 4 wherein the audio processing means comprises:

a microphone having an output;

an analog-to-digital converter having an input connected to the output of the microphone and an output; and

a digital audio signal processor having an input interfaced to the output of the analog-to-digital converter and also having a bidirectional bus;

the communication controller being interfaced to the bidirectional bus of the digital audio signal processor.

15. The apparatus of claim 4 wherein the communication controller comprises:

a system sequencer having a bidirectional bus interfaced to the video processing means and to the audio processing means and also having a first serial bus;

a modem circuit interfaced to the first serial bus and having a second serial bus; and

a line interface connected to the second serial bus and having a serial interconnection to the standard telephone line.

16. The apparatus of claim 15 wherein the modem circuit is one of a 19.2 kilobits per second and a 24 kilobits per second modem circuit.

17. A method for communicating audio and video simultaneously via a standard bidirectional (full duplex) telephone line in the form of a twisted pair, comprising the steps of:

transducing and digitizing images;

compressing and encoding an initial digitized image to produce video data and storing the video data;

detecting a change in a subsequent digitized image with respect to the initial digitized image;

compressing and encoding the change in the digitized image to produce changed video data and storing the changed video data;

synchronously transducing and digitizing sound present when the images are being transduced and digitized;

compressing and encoding the digitized sound into audio data and storing the audio data;

formatting and transmitting the stored audio data bundled with the stored video data via the standard telephone line at a synchronous data transmission rate less than 56 kilobits per second;

detecting when the amount of video data that is stored reaches a predetermined level such that the amount of changed video data exceeds the capability to transmit the changed video data within a time period allotted for transmission via the standard telephone line to produce a current image;

discontinuing the storage of changed video data when the predetermined level is reached; and

producing video data for a subsequent current image and storing the subsequent current video data so that the amount of video data that is stored does not reach the predetermined level.

18. The method of claim 17 wherein the step of discontinuing the storage of changed video data comprises dumping the changed video data for the current image and the step of producing video data for the subsequent current image comprises overwriting stored video data with I-frame video data for the subsequent current image when the predetermined level is reached.

19. The method of claim 17, further comprising the steps of:

receiving audio and video data via the standard telephone line;

unformatting and unbundling the received audio and video data;

decoding and decompressing the received audio and video data;

reproducing images based on the decoded and decompressed video data; and

reproducing sound based on the decoded and decompressed audio data.

20. The method of claim 17 wherein the steps of transducing and digitizing images, compressing and encoding the digitized images into video data, synchronously transducing and digitizing sound present when the images are being transduced and digitized, and compressing and encoding digitized sound into audio data are performed when a first button is pressed;

further comprising the steps of;

storing the video and audio data; and

playing back the images and any associated sound by decoding, decompressing, and reproducing the stored video and any associated audio data when a second button is pressed; and

wherein the step of formatting and transmitting the audio data bundled with the video data via the standard telephone line at a synchronous data transmission rate less than 56 kilobits per second is performed when the second and a third button are pressed.