Videotelephone apparatus for transmitting high and low resolution video signals over telephone exchange lines

• US 4,888,795 A
• Filed: 06/28/1988
• Issued: 12/19/1989
• Est. Priority Date: 06/30/1987
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yokoyama, Takayuki, Ando, Fumio, Ichinokawa, Kazuo
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Lewis, Bonita
• Application Number:
  US07/212,498
• Time in Patent Office: 539 Days
• Field of Search: 379/53, 379/54, 379/96, 379/110, 358/85
• US Class Current: 348/14.14
• CPC Class Codes: H04N 1/33307 prior to start of transmission, input or output of the picture signal only
• CPC Class Codes: H04N 19/00 Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 7/122 involving expansion and subsequent compression of a signal segment, e.g. a frame, a line
• CPC Class Codes: H04N 7/142 Constructional details of the terminal equipment, e.g. arrangements of the camera and the display
• CPC Class Codes: Y10S 379/916 Touch screen associated with telephone set

Abstract

In an audiovisual communication, a first high fram rate video signal is derived from a motion image and converted to a low fram rate low resolution multiframe signal. A second high frame rate video signal is derived from an still image and converted to a single frame high resolution signal. Because of the low frame rates, the frequencies of the low and high resolution signals are within the range of frequencies of a telephone exchange line. A switching matrix is provided to sequentially couple both the low and high resolution signals to a transmission line in response to a mode select signal. The single frame high resolution signal is stored into a memory at the receiving end and repeatedly retrieved out of the memory into a display through the switching matrix.

Claims

1. A videotelephone apparatus comprising:

image pickup means for generating first and second high frame rate video signals representative of moving objects and objects which are standing still, respectively;

conversion means for converting said first high frame rate video signal to a low frame rate low resolution signal and converting the second high frame rate video signal to a single frame high resolution signal, each frame of said low frame rate low resolution signal having n×

m pixels and the frame of said high resolution signal having N×

M pixels, where N and M are respectively greater than n and m;

transmit means for transmitting said low frame rate low resolution signal and said single frame high resolution signal via a transmission medium to a destination apparatus;

receive means including a memory for receiving a low frame rate low resolution signal and a single frame high resolution signal from said destination apparatus and for storing said single frame high resolution signal into said memory and repeatedly retrieving it from the memory;

display means;

manually operated command entry means for generating a plurality of mode select signals in response to manual command inputs; and

switching means responsive to said mode select signals for selectively coupling said low rate low resolution multiframe signal and said single frame high resolution signal to said transmit means and coupling signals from said receive means to said display means.

2. A videotelephone apparatus as claimed in claim 1, wherein said conversion means comprises means for converting said second high frame rate video signal to a multiframe high resolution signal and converting same to said single frame high resolution signal, and wherein said manually operated command entry means generates a framing command signal and transmit command signal, wherein said switching means is responsive to said framing command signal for coupling said multiframe high resolution to said display means and responsive to said transmit command signal for decoupling said multiframe high resolution signal from said display means and coupling said single frame high resolution signal to said display means.

3. A videotelephone apparatus as claimed in claim 2, wherein said switching means decouples said low rate low resolution multiframe signal from said transmit means in response to said transmit command signal and recouples said low rate low resolution multiframe signal to said transmit means at the end of transmission of said single frame high resolution signal.

4. A videotelephone apparatus as claimed in claim 3, wherein said display means include a memory for storing a frame of said low frame rate low resolution multiframe signal and continuously displaying the stored frame during the transmission of said single frame high resolution signal.

5. A videotelephone apparatus as claimed in claim 1, wherein said conversion means comprises means for converting said second high frame rate video signal to a multiframe high resolution signal and converting same to said single frame high resolution signal, and wherein said manually operated command entry means generates a framing command signal, further comprising still picture detecting means responsive to said framing command signal for detecting a still picture in said multiframe high resolution signal, wherein said switching means is responsive to said framing command signal for coupling said multiframe high resolution signal to said display means and responsive to the detection of said still picture by said still picture detecting means for decoupling said multiframe high resolution signal from said display means and coupling said single high resolution signal to said display means.

6. A videotelephone apparatus as claimed in claim 5, wherein said still picture detecting means comprises:

frame delay means for introducing a delay of a frame interval to said multiframe high resolution signal;

means for detecting a difference between an output signal from said frame delay means and said multiframe high resolution signal on a per pixel basis;

means for integrating a plurality of said differences generated in each frame interval to produce a sum;

means for comparing said sum with a predetermined value to produce a logic output at one of two discrete values depending on the relative value of said sum to said predetermined value;

means for storing the logic outputs generated in each frame interval into a series of cells to produce a frame-by-frame bit patterns; and

means responsive to said framing command signal for detecting a match between said frame-by-frame bit pattern and a prescribed bit pattern and supplying a signal to said switching means as an indication that a freeze frame is detected.

7. A videotelephone apparatus as claimed in claim 6, further comprising an arm hinged at one end thereof and movable between a rest position and an upright position, wherein said image pickup means is mounted at the other end of said arm to generate said first high frame rate video signal when said arm is in said rest position and generate said second high frame rate video signal when said arm is in said upright position, and a switch means located adjacent a pivot point of said arm to generate said framing command signal when said arm is brought to said upright position.

8. A videotelephone apparatus as claimed in claim 5, further comprising an arm hinged at one end thereof and movable between a rest position and an upright position, wherein said image pickup means is mounted at the other end of said arm to generate said first high frame rate video signal when said arm is in said rest position and generate said second high frame rate video signal when said arm is in said upright position, and a switch means located adjacent a pivot point of said arm to generate said framing command signal when said arm is brought to said upright position.

9. A videotelephone apparatus as claimed in claim 1, further comprising image enlarging means for multiplying each pixel of the low frame rate low resolution signal received by said receive means by a factor N×

M/n×

m to enlarge the (n×

m) pixel plane of said received signal to an (N×

M) pixel plane, wherein said display means provides a display of the enlarged low resolution signal on an (N×

M) pixel plane.

10. A videotelephone apparatus as claimed in claim 9, wherein said display means comprises a fist display having an (n×

m)-pixel plane and a second display having an (N×

M)-pixel plane, and wherein said image enlarging means is connected to said second display and said switching means includes means for coupling the low resolution signal received by said receive means to said image enlarging means.

11. A videotelephone apparatus as claimed in claim 10, wherein said first and second displays are vertically spaced from each other, and wherein said image pickup means comprises a first video camera for generating said first video output signal and a second video cameras for generating said second video output signal, said first video cameras being located between said first and second displays, said second camera being mounted on a support movable with respect to said object which is standing still.

12. A videotelephone apparatus as claimed in claim 1, further comprising:

a screen touch sensor for generating a coordinate signal indicating a point specified on said display means in a coordinate system; and

marker generating means for generating a marker code in response to said coordinate signal and applying the marker code to said transmit means and to said display means.

13. A videotelephone apparatus as claimed in claim 12, wherein each of the frames of said low frame rate low resolution signal is preceded by a header containing a first identifier and said single frame high resolution signal comprises a plurality of successive subframes each being preceded by a header containing a second identifier and said marker code.

14. A videotelephone apparatus as claimed in claim 13, wherein said image pickup means includes means for generating a sync timing signal and supplying the sync timing signal to said conversation means to permit a generation of said low frame rate low resolution signal and said single frame high resolution signal, and wherein said switching means comprises means for coupling said sync timing signal to said display means and said transmit means and coupling a sync timing signal received by said receive means to said display means.

15. A videotelephone apparatus as claimed in claim 1, wherein said display means comprises a first display having an (n×

m)-pixel plane and a second display pixel plane, said first display is located in a position higher than said second display.

16. A videotelephone apparatus as claimed in claim 1, further comprising an arm hinged at one end thereof and movable between a rest position and an upright position, wherein said image pickup means is mounted at the other end of said arm to generate said first video output signal when said arm is in said rest position and generate said second video signal when said arm is in said upright position.

17. A videotelephone apparatus as claimed in claim 16, wherein said apparatus is housed in a housing comprising a front portion having a low profile for mounting a numeric key pad and a rear portion having a higher profile, said display means being located in said rear portion.

18. A videotelephone apparatus comprising:

image pickup means for generating first and second high frame rate video signals representative of moving objects and objects which are standing still, respectively;

first conversion means for converting said first high frame rate video signal to a multiframe low resolution display signal and converting the second high frame rate video signal to a multiframe high resolution display signal, each frame of said low resolution display signal having n×

m pixels and each frame of said high resolution display signal having N×

M pixels, where N and M are respectively greater than n and m;

second conversion means for converting said low resolution display signal to a low frame rate low resolution signal having a lower frame rate than the frame rate of said first video signal and converting said high resolution display signal to a single frame high resolution signal;

transmit means for transmitting said low frame rate low resolution signal and said single frame high resolution signal via a transmission medium to a destination apparatus;

receive means including a memory for receiving low frame rate low resolution signal and a single frame high resolution signal from said destination apparatus and for storing the received high resolution signal into said memory and repeatedly retrieving it from said memory;

display means;

manually operated command entry means for generating a plurality of mode select signals in response to manual command inputs; and

switching means responsive to said mode select signals for selectively coupling said low and high resolution display signals from said first conversion means to said display means and to said second conversion means and coupling output signals of said receive means to said display means.

19. A videotelephone apparatus as claimed in claim 18, wherein said manually operated command entry means generates a framing command signal and a transmit command signal, wherein said switching means is responsive to said framing command signal for coupling said high resolution display signal to said display means and responsive to said transmit command signal for decoupling said high resolution display signal from said display means and coupling said single frame high resolution signal to said display means instead of said high resolution display signal.

20. A videotelephone apparatus as claimed in claim 18, wherein said manually operated command entry means generates a framing command signal, further comprising still picture detecting means responsive to said framing command signal for detecting a still picture in said high resolution display signal, wherein said switching means is responsive to said framing command signal for coupling said high resolution display signal to said display means and responsive to the detection of said still picture by said still picture detecting means for decoupling said high resolution display signal from said display means and coupling said single frame high resolution signal to said display means instead of said high resolution display signal.

21. A videotelephone apparatus as claimed in claim 20, wherein said still picture detecting means comprises:

frame delay means for introducing a delay of a frame interval to said high resolution display signal;

means for detecting a difference between an output signal from said frame delay means and said high resolution display signal on a per pixel basis;

means for integrating a plurality of said differences generated within a frame interval to produce a sum;

means for comparing said sum with a predetermined value to produce one of two logical values depending on the relative value of said sum to said predetermined value;

means for storing the logical values over a frame interval to produce a frame-by-frame bit pattern; and

means responsive to said framing command signal for detecting a match between said frame-by-frame bit pattern with a prescribed bit pattern and supplying a signal to said switching means as an indication that a still picture is detected.

22. A videotelephone apparatus as claimed in claim 20, further comprising an arm hinged at one end thereof and movable between a rest position and an upright position, wherein said image pickup means is mounted at the other end of said arm to generate said first high frame rate video signal when said arm is in said rest position and generate said second high frame rate video signal when said arm is in said upright position, and a switch means located adjacent a pivot point of said arm to generate said framing command signal when said arm is brought to said upright position.

23. A videotelephone apparatus as claimed in claim 20, further comprising an arm hinged at one end thereof and movable between a rest position and an upright position, wherein said image pickup means is mounted at the other end of said arm to generate said first high frame rate video signal when said arm is in said rest position and generate said second high frame rate video signal when said arm is in said upright position, and a switch means located adjacent a pivot point of said arm to generate said framing command signal when said arm is brought to said upright position.

24. A videotelephone apparatus as claimed in claim 18, further comprising means for multiplying each pixel of a low frame rate low resolution signal received by said receive means by a factor N×

M/n×

m to enlarge the (n×

m) pixel plane of said received signal to an (N×

M) pixel plane, wherein said display means provides a display of the enlarged low signal on an (N×

M) pixel plane.

25. A videotelephone apparatus as claimed in claim 24, wherein said display means comprises a first display having an (n×

m)-pixel plane and a second display having an (N×

M)-pixel plane, and wherein said image enlarging means is connected to said second display and said switching means includes means for coupling the low frame rate low resolution signal received by said receive means to said image enlarging means.

26. A videotelephone apparatus as claimed in claim 25, wherein said first and second displays are vertically spaced from each other, and wherein said image pickup means comprises a first video camera for generating said first video output signal and a second video camera for generating said second video output signal, said first video camera being located between first and second displays, said second camera being mounted on a support movable with respect to said object which is standing still.

27. A videotelephone apparatus as claimed in claim 18, further comprising:

a screen touch sensor for generating a coordinate signal indicating a point specified on said display means in a coordinate system; and

market generating means for generating a marker code in response to said coordinate signal and applying the marker code to said transmit means and to said display means.

28. A videotelephone apparatus as claimed in claim 27, wherein each of the frames of said low frame rate low resolution signal is preceded by a header containing a first identifier and said single frame high resolution signal comprises a plurality of successive subframes each being preceded by a header containing a second identifier and said marker code.

29. A videotelephone apparatus as claimed in claim 18, wherein said second conversion means comprises:

a frame memory having an (N×

M)-pixel plane;

write address generator means for generating first and second write address codes for writing one of a plurality of successive frames of said low resolution display signal into an (n×

m)-pixel plane portion of said frame memory and writing a single frame of said high resolution display signal into the full (N×

M)-pixel plane of said memory; and

read address generator means for generating read address codes for reading the stored frame from said (n×

m)-pixel portion of said memory at a rate lower than a rate at which stored frame is written into said memory to produce said low frame rate low resolution signal, and reading said single frame of said second display signal from said memory at a rate lower than a rate at which the stored single frame is written into said memory to produce said single frame high resolution signal.

30. A videotelephone apparatus as claimed in claim 18, further comprising an arm hinged at one end thereof and movable between a rest position and an upright position, wherein said image pickup means is mounted at the other end of said arm to generate said first high frame rate video signal when said arm is in said rest position and generate said second high frame rate video signal when said arm is in said upright position.

31. A videotelephone apparatus as claimed n claim 30, wherein said apparatus is housed in a housing comprising a front portion having a low profile for mounting a numeric key pad and a rear portion having a higher profile, said display means being located in said rear portion.

32. A videotelephone apparatus as claimed in claim 18, wherein said image pickup means includes means for generating a sync timing signal and supplying the sync timing signal to said first conversion means to permit generation of said multiframe low and high resolution signals, and wherein said switching means comprises means for coupling said sync timing signal to said display means, said second conversion means and said transmit means and for coupling a sync timing signal received by said receive means to said display means.

33. A videotelephone apparatus comprising:

image pickup means for generating first and second video output signals representative of moving objects and objects which are standing still, respectively;

data compression means for converting said first video output signal of said image pickup means to a low resolution multiframe signal according to a data compression algorithm and converting the second video output signal of said image pickup means to a high resolution single frame signal according to said data compression algorithm;

transmit means for transmitting said low resolution multiframe signal and said high resolution single frame signal via a transmission medium to a destination apparatus;

receive means including a memory for receiving a low resolution multiframe signal and a single frame high resolution signal from said destination apparatus, and for storing said single frame high resolution signal into said memory and repeatedly retrieving it from the memory;

data decompression means for respectively converting the received low resolution multiframe signal and the received high resolution single frame signal to signals identical in format to said first and second video output signals generated by said image pickup means according to a data expansion algorithm inverse to said data compression algorithm;

display means;

manually operated command entry means for generating a plurality of mode select signals in response to manual command inputs; and

switching means responsive to said mode select signals for selectively coupling said first and second video output signals from said image pickup means, coupling said low and high resolution multiframe signals from said data compression means to said display means and said transmit means, and coupling said signals converted by said data expansion means to said display means.

34. A videotelephone apparatus as claimed in claim 33, wherein said data compression means comprises first and second coding circuits having a hierarchical coding algorithm for respectively converting said first and second video output signals to said low resolution multiframe signal and said high resolution single frame signal.

35. A videotelephone apparatus as claimed in claim 33, where said data compression means includes:

a plurality of spatial frequency filters of different resolutions and passing said first and second video output signals of said image pickup means through said spatial frequency filters to develop differential video signals of different levels of resolution; and

means for successively supplying said differential video signals to said transmit means with the lowest level of resolution first and an intermediate level of resolution last for generating said low resolution multiframe signal and successively supplying said differential video signals with the lowest level of resolution first and the highest level of resolution last for generating said high resolution single frame signal.

36. A videotelephone apparatus as claimed in claim 33, wherein said data compression means comprises:

a frame memory comprising a plurality of blocks;

a write address generator for writing said first and second video output signals into said frame memory at a frame rate lower than the frame rate of said video output signals; and

a microprocessor connected to the output of said frame memory, said microprocessor being programmed to perform the steps of;

(a) performing discrete cosine transform on data stored in said frame memory on a block by block basis;

(b) performing scaler quantization on the data of step (a);

(c) performing modified Huffman coding on the data of step (b) stored in a smaller portion of each of said blocks in response to a first control signal from said switching means and repeating the steps (a) to (c) to generate said low frame rate low resolution signal; and

(d) performing said modified Huffman coding on the data of step (b) stored in a greater portion of each of said blocks in response to a second control signal from said switching means to product said single frame high resolution signal.

37. A videotelephone apparatus as claimed in claim 33, wherein each of said first and second video output signals is a triplet of primary color signals, and wherein said data compression means comprises:

first, second and third frame memories each comprising a plurality of blocks;

a write address generator for writing the primary color components of either of said first and second video output signals into said first, second and third frame memories respectively, at a frame rate lower than the frame rate of said video output signals; and

a microprocessor connected to the output of said frame memory, said microprocessor being programmed to perform the steps of;

(a) converting said primary color components stored in said frame memories into a luminance and color difference components;

(b) subsampling said color difference components;

(c) performing a discrete cosine transform on data of steps (a) and (b) on a block by block basis;

(d) performing scaler quantization on the data of step (c);

(e) performing modified Huffman coding on the data of step (d) stored in a smaller portion of each of said blocks in response to a first control signal from said switching means (703) and repeating the steps (c) to (e) to generate said low frame rate low resolution signal; and

(f) performing said modified Huffman coding on the data of step (d) stored in a greater portion of each of said blocks in response to a second control signal from said switching means to produce said single frame high resolution signal.

38. A videotelephone apparatus as claimed in claim 33, further comprising:

a screen touch sensor for generating a coordinate signal indicating a point specified on said display means in a coordinate system; and

market generating means for generating a marker code in response to said coordinate signal and applying the marker code to said transmit means and to said display means.

39. A videotelephone apparatus as claimed in claim 38, wherein each of the frame of said low frame rate low resolution signal is preceded by a header containing a first identifier and said single frame high resolution signal comprises a plurality of successive subframes each being preceded by a header containing a second identifier and said marker code.

40. A videotelephone apparatus as claimed in claim 33, further comprising an arm hinged at one end thereof and movable between a rest position and an upright position, wherein said image pickup means is mounted at the other end of said arm to generate said first video output signal when said arm is in said rest position and generate said second video signal when said arm is in said upright position.

41. A videotelephone apparatus as claimed in claim 40, wherein said apparatus is housed in a housing comprising a front portion having a low profile for mounting a numeric key pad and a rear portion having a higher profile, said display means being located in said rear portion.