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WO1991010328A1 - Systemes de visiophones - Google Patents

Systemes de visiophones Download PDF

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Publication number
WO1991010328A1
WO1991010328A1 PCT/US1990/007649 US9007649W WO9110328A1 WO 1991010328 A1 WO1991010328 A1 WO 1991010328A1 US 9007649 W US9007649 W US 9007649W WO 9110328 A1 WO9110328 A1 WO 9110328A1
Authority
WO
WIPO (PCT)
Prior art keywords
image
grey
pixel
scale
difference signal
Prior art date
Application number
PCT/US1990/007649
Other languages
English (en)
Inventor
Robert L. Harvey
Patrick R. Hirschler-Marchand
David J. Cipolle
Kipton C. Kumler
Original Assignee
Massachusetts Institute Of Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Massachusetts Institute Of Technology filed Critical Massachusetts Institute Of Technology
Priority to KR1019910700999A priority Critical patent/KR920702157A/ko
Publication of WO1991010328A1 publication Critical patent/WO1991010328A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/14—Systems for two-way working
    • H04N7/141—Systems for two-way working between two video terminals, e.g. videophone
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T3/00—Geometric image transformations in the plane of the image
    • G06T3/40—Scaling of whole images or parts thereof, e.g. expanding or contracting
    • G06T3/4007—Scaling of whole images or parts thereof, e.g. expanding or contracting based on interpolation, e.g. bilinear interpolation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/136—Incoming video signal characteristics or properties
    • H04N19/137—Motion inside a coding unit, e.g. average field, frame or block difference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • H04N19/93—Run-length coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/25—Management operations performed by the server for facilitating the content distribution or administrating data related to end-users or client devices, e.g. end-user or client device authentication, learning user preferences for recommending movies
    • H04N21/266—Channel or content management, e.g. generation and management of keys and entitlement messages in a conditional access system, merging a VOD unicast channel into a multicast channel
    • H04N21/2662—Controlling the complexity of the video stream, e.g. by scaling the resolution or bitrate of the video stream based on the client capabilities
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
    • H04N21/61—Network physical structure; Signal processing
    • H04N21/6106—Network physical structure; Signal processing specially adapted to the downstream path of the transmission network
    • H04N21/6137—Network physical structure; Signal processing specially adapted to the downstream path of the transmission network involving transmission via a telephone network, e.g. POTS
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
    • H04N21/61—Network physical structure; Signal processing
    • H04N21/6156—Network physical structure; Signal processing specially adapted to the upstream path of the transmission network
    • H04N21/6187—Network physical structure; Signal processing specially adapted to the upstream path of the transmission network involving transmission via a telephone network, e.g. POTS
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/04—Systems for the transmission of one television signal, i.e. both picture and sound, by a single carrier
    • H04N7/045—Systems for the transmission of one television signal, i.e. both picture and sound, by a single carrier the carrier being frequency modulated
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/12—Systems in which the television signal is transmitted via one channel or a plurality of parallel channels, the bandwidth of each channel being less than the bandwidth of the television signal

Definitions

  • the technical field of this invention is image processing and, more specifically, differential motion detection processes and devices.
  • the invention relates to video telephones for transmitting both sound and images in real time over standard residential telephone lines.
  • ISDN Integrated Switched Digital Network
  • An object of this invention is to provide an image data compression process to enable video telephones to be used over the present, copper-based, residential telephone network, as well as other low bandwidth transmission media.
  • Another object of this invention is to provide an inexpensive video telephone that may be used with standard video cameras and video display screens or personal computers to provide videoconferencing capabilities between users connected to the standard residential telephone network.
  • Differential motion detection data compression systems and techniques are disclosed for use in low-cost, video telephone systems for full duplex, real time transmission of audio and video images over nominal 3 kHz residential telephone lines and other low bandwidth channels.
  • Each video telephone device consists of a transmitting portion and a receiving portion.
  • the transmitting section transforms an image (e.g., either from a standard video camera or an alternative imaging device such as a charge coupled device or CCD) into a reduced grey-scale image preferably consisting of only black-and-white pixels. This image is then compared with a similarly reduced image derived from previous image data to determine pixel positions that have changed. Information representative of the changes between image frames is then encoded to further compress the data and then modulated and multiplexed with the audio signal for transmission over a standard 3 kHz telephone line.
  • color images can be transmitted by decomposing the color video signal into its luminance and chrominance components and then processing the luminance values in accordance with this invention.
  • grey-scale image is intended to encompass both simple "black-and-white” images and the luminance component of color images.
  • Techniques for encoding and transmitting the chrominance values of color images, as well as reconstruction of a color image from the luminance and chrominance information, will be described below.
  • Coherent modulation/demodulation can be used to enable transmission and reception of the video and audio signals over a standard residential telephone line. Coherent modulation produces frequency transformations of the signals to position the signal bandwidth in the telephone line channel, nominally, 0 to 3 kHz.
  • the coherent modulation also is used to enable multiplexing two analog signals simultaneously onto the telephone line bandwidth, as described in more detail below.
  • Techniques for reducing crosstalk between the transmitted audio and video signals, as well as alternative frequency division multiplexing techniques for transmittal of the audio and video signals, are also disclosed below.
  • adaptive resolution apparatus and methods are disclosed in which different data compression techniques are used, depending on the degree of motion in the image over time.
  • three states fast motion, intermediate motion and slow motion
  • different data processing steps practiced in the transmitter based on the state determination.
  • the receiving section reverses the data compression process of the transmitting section.
  • the incoming signal is demodulated and demultiplexed to separate the audio and video portions, the image portion is decoded, and the reduced grey-scale image of the previous frame is updated accordingly.
  • the image Prior to the display of the updated image, the image can be transformed from a reduced grey-scale state into a fuller grey-scale image or a reconstructed luminance signal by overlapping and averaging blocks of pixel values.
  • various transmission schemes can be employed.
  • luminance and audio information can be coherently modulated, as in the black-and-white case, but over a slightly narrowed bandwidth (e.g., over a 0 - 2500 Hz band with a first carrier frequency, f 1 , and the I & Q color components can be coherently modulated in a second band (e.g., over 2500 - 3000 Hz band with a second carrier frequency, f 2 ).
  • a luminance signal L and chrominance signals e.g., X red and X blue color signals, can be multiplexed over time.
  • the color signals can be sampled over time and then time domain multiplexed over the audio channel.
  • the image data compression techniques of the present invention can be applied not only to video telephones and video conferencing systems but to graphic image storage devices, high definition television (HDTV), cable television, facsimile machines and computerized document storage on magnetic or optical disks.
  • the images that can be processed vary from still, black-and-white characters to fast-moving, high-resolution color images of intricate objects.
  • the invention can also be adapted for image transmission over other narrow band media, such as radio transmissions, through the air.
  • the invention can be adapted to transmit graphic images of text generated by a computer instead of a video camera.
  • the video telephones of the present invention also are compatible with conventional telephones and can receive and/or transmit audio signals, alone, whenever communication with a regular telephone or other audio transceiver is desired.
  • the systems of the present invention can be used not only with analog signals produced by conventional TV cameras but also with the signals produced by imaging devices such as CCDs and the like.
  • FIG. 1 is a schematic block diagram of a black-and-white video telephone system in accordance with the present invention
  • FIG. 2 is a schematic block diagram of a color video telephone system in accordance with the present invention.
  • FIG. 3 is a more detailed schematic diagram of an image processing module for use in the transmitter of FIG. 1;
  • FIG. 4 is an illustrative matrix of dithered threshold values for a 4 x 4 block of pixels useful in a grey-scale reduction unit according to the invention
  • FIG. 5A illustrates a hysteresis process for adjusting the dithered threshold values in a grey-scale reduction unit to decrease toggling and image flickering for a white pixel value in a previous frame;
  • FIG. 5B illustrates a similar hysteresis adjustment for a black pixel value in a previous frame
  • FIG. 6 is a more detailed schematic diagram of the modulation and multiplexing elements of the transmitter and the demodulation and demultiplexing elements of the receiver of the system of FIG. 1.
  • FIG. 7 is a schematic illustration of a system for suppressing cross-talk between the video and audio signals in a system, such as shown in FIG. 6.
  • FIG. 8 is a schematic illustration of an alternative modulation and demodulation approach for use in the present invention.
  • FIGS. 9A-9D illustrate an averaging process useful in the image averaging unit of the receiver of FIG. 1.
  • FIG. 10 is a schematic block diagram of a video telephone system employing an adaptive resolution module
  • FIG. 11A is an illustration of a matrix of dithered threshold values for coarse resolution in the adaptive system of FIG. 10.
  • FIG. 11B is an illustration of a matrix of dithered threshold values for intermediate resolution in the adaptive system of FIG. 10.
  • FIG. 11C is an illustration of a matrix of dithered threshold values for fine resolution in the adaptive system of FIG. 10. Detailed Description
  • a video telephone system 10 in accordance with the present invention is shown, including a transmitter section 12, having a sampling unit 14, an image processing module 20 (including a grey-scale reduction unit 16, a frame memory 15 and a motion detection unit 18), a differential image encoding unit 22, an optional error correction unit 24, an image modulator 26, an optional audio modulator 28 and a multiplexing mixer 30.
  • System 10 further includes a receiver section 38 having a demultiplexing and demodulating unit 42, an optional speaker 44 for audio output, an optional error detector 46, an image decoder 48, an image updating unit 50 (including image memory 52 and comparator 54), a pixel averaging unit 56, and a display or monitor driver 58 for video output.
  • Image data is first compressed by the sampling and grey-scale reduction units 14 and 16, then compared with a previously reduced grey-scale image in the motion detection unit 18 to produce image data representative of the changes from the previous image frame.
  • the differential image data is further compressed by the encoding unit 22, such that the image data may be modulated and transmitted over a 3 kHz or other narrow bandwidth channel.
  • the transmitted image data is received by the receiving section 38, as shown in FIG. 1, which reconstructs the new image.
  • the receiving section 38 also has three levels of data decompression.
  • the encoded image data is decoded by decoding unit 48 to provide the differential image, which is then used in the image updating unit 50 to make the designated changes to the previous image frame.
  • the image is averaged in averaging unit 56 to yield a greater range of shades of grey which can then be displayed on monitor 58.
  • System 10A includes filter 11 which decomposes a color (e.g., NTSC) video signal into its luminance component L and two chrominance components I and Q.
  • the luminance component L can be processed by module 20, encoder 24 and modulator 26 in a manner substantially identical to the processing of a black-and-white image, as shown in FIG. 1.
  • the luminance data can then be multiplexed with audio data via mixer 30 and transmitted over a portion of the bandwidth (e.g., a nominal frequency band ranging from about 0 to about 2500 Hz) while a second portion of the bandwidth (e.g., a nominal frequency bandwidth (e.g. a nominal frequency bandwidth from about 2500 to about 3000
  • the I and Q chrominance values can be modulated by modulator 13 and mixed together in mixer 17.
  • the luminance/audio and chrominance data can then be multiplexed together via mixer 19 for transmission.
  • the luminance and chrominance values (as well as audio signals, if any) are demultiplexed and demodulated by unit 42, and the luminance data is decoded by decoding unit 48 to provide the differential image, which is then used in the updating unit 50 to update the image.
  • the luminance values can be averaged to yield a greater range of grey values, which are then inputed into display driver 58, together with the chrominance values to provide a color video output.
  • the grey-scale reducing unit 16 transforms the image by reducing the number of grey levels for each pixel.
  • the resultant image when viewed by the human eye from a distance, has an appearance which is strikingly similar to the original image; however, it requires fewer bits of information.
  • the transformation entails reducing an image having 256 shades of grey into two shades, white and black. This results in an 8-fold reduction in the data required to represent the image, as each pixel is converted from having an 8-bit grey-scale representation to a 1-bit representation.
  • the grey value of each pixel is compared to a threshold value which varies with its pixel position. For grey values greater than the threshold, i.e., lighter in shade, the pixel value becomes 1, representative of pure white. For grey values less than the threshold, the transformed pixel value becomes 0, or pure black.
  • Different pixel positions have different threshold values which are selected to provide a proportional combination of black-and-white pixels such that when an area or block of pixels are viewed from a distance, the image appears the desired shade of grey.
  • the selected threshold values produce a primarily white pixels for light shades of grey, and increasingly more black pixels per unit area for darker shades of grey.
  • Various dithering methods known in the art can be employed in the present convention. See, for example, Ochi et al., "A New Halftone Reproduction and Transmission Method Using Standard Black & White Facsimile Code," Vol. COM-35, IEEE Transactions on Communications, pp. 466-470
  • the compressed or dithered image is then compared in a motion detection unit 18 to the compressed image from the previous image frame, as stored in an image memory unit.
  • the motion detection unit 18 detects which pixels have been changed between the two image frames and records the pixel locations. In one illustrated embodiment, pixel positions with no change have a value of 0, and those that have changed, either from white to black or black to white, have a value of 1.
  • the new compressed image is then stored in the image memory unit for comparison with the next image frame.
  • a differential image is next encoded in the differential image encoding unit 22 to further compress the data prior to transmission.
  • run-length encoding is used, many versions of which are known in the art. In normal operation, the image will not change too much from frame to frame, leaving long series of 0 bits in the differential image.
  • Run-length encoding represents various lengths (or runs) of consecutive 0's or 1's as code words. For example, in one embodiment, the shortest code words can be assigned to the most likely runs, effectively compressing the number of bits required to represent the data where there are long series of consecutive 0's or 1's.
  • the encoded differential image data is then ready for transmission over a narrow bandwidth channel, particularly a 3 kHz telephone line.
  • additional optional coding techniques such as toward error correction, may be conducted prior to transmission which will be described below.
  • the receiving section 38 shown in FIG. 1, (or the similar receiver 38A shown in FIG 2), generally reverses and decodes the three levels of data compression as described in the transmitter but in the opposite order.
  • the encoded differential image data is decoded in decoding unit 48 using the reverse process as used in the differential image encoding unit 22. In the preferred embodiment, this decoding process would reverse the selected run-length coding scheme.
  • the previous image frame as stored in the image 52 memory unit is updated by the differential image data in the image updating unit.
  • the pixel value of the corresponding pixel position is changed. This would switch a black pixel to white and vice versa.
  • the pixel value of the corresponding pixel position remains unchanged.
  • the updated compressed or dithered image is partially restored to its original image with multiple grey-scales in the image averaging unit. The value of each pixel position is calculated by averaging the pixel values of all positions within a prescribed region.
  • the invention may include an error code generator 24 and error detector 46, as shown in dotted lines in FIG. 1.
  • This adaptation may be desirable for use over noisy transmission lines.
  • One commonly-used error correction technique is forward error correction (FEC), in which redundant bits of data are added to the data stream in a specified manner, such that the FEC decoder on the receiving section can check for errors due to noise.
  • FEC forward error correction
  • S. Lin and D. Costello Error Control Coding: Fundamentals and Applications (Prentice-Hall, Englewood Cliffs, NJ 1983) for a further description of FEC systems, incorporated herein by reference.
  • FEC FEC
  • a joint modulation-coding scheme may be used to combine 24 and 26 into a single unit.
  • a corresponding demodulation-decoding unit combining 42 and 46 would be used.
  • Possible choices for this technique are tamed frequency modulation, continuous phase modulation, and trellis-code modulation. Other choices are obvious to those familiar with the art. These techniques provide noise reduction without increasing the signal bandwidth, but require more complexity.
  • FIGS. 1 and 2 Another optional element of the invention as shown in FIGS. 1 and 2 is the audio modulator 28 and mixer 30 for multiplexing an audio signal with the modulated image signal for simultaneous audio and video transmission.
  • the receiving section 38 then separates the audio and video portions of the signal by an analogous demodulation and demultiplexing unit 42. While this combination is envisioned to be a highly desirable feature, particularly for video conferencing; it is not an essential element. For some applications, an audio portion may be superfluous or undesired.
  • FIG. 3 shows the image processing module 20 of FIGS. 1 and 2 (the grey-scale reducing unit 16, the frame memory unit 15 and the motion detection unit 18) in greater detail.
  • FIG. 3 illustrates an embodiment which includes an hysteresis-dithered, thresholding process for converting a multiple grey-scale image into a halftone image consisting of black-and-white pixels. The halftone image in turn is compared to that from the previous image frame to provide a differential image, which is further processed by the image encoding unit in the third compression stage.
  • the image processing module 20 includes an analog comparator 80, an ordered dither threshold table 82, a frame memory 15, inverter 84, summer 86, summer 88, digital-to-analog converter 90 and an exclusive OR gate 92.
  • Inputs to the image processing module 20 of FIG. 3 are luminance values which can be derived from any standard video camera that converts an image into an NTSC or similar format (such as PAL or SECAM).
  • the analog signal representative of the image from the camera is then passed through a clamp and sample circuit which provides the reduced analog image, which is an analog signal representative of an image screen of 128 x 128 pixels at a rate of 10 frames per second. This can be accomplished by sampling the NTSC signal 128 times per line and one time out of every four lines.
  • the sampled pixel values from the analog signal are real numbers representative of an 8-bit grey-scale consisting of 256 shades of grey from pure black (0) to pure white (255).
  • the image size can be any N x K matrix of pixels
  • the frame rate may be varied, and any number of grey levels may be used.
  • the resolution is increased, the frame rate will generally have to be decreased to permit the image data to compress sufficiently to permit effective transmission of the real time image over a 3 kHz telephone line.
  • the frame rate is increased, the image resolution will have to be decreased accordingly.
  • the camera, clamp and sample circuit may be replaced by a digital or analog storage device or other means for generating a digital or analog signal representative of an image.
  • the next stage of the process entails converting the sampled analog pixel values into 1-bit binary values representative of black or white. This is accomplished in comparator 80 by comparing the real value of each pixel with a threshold value, as stored in the ordered dither threshold table 82, as shown in FIG. 3.
  • the table is a digital memory device representative of a shade of grey for each of the 128 x 128 pixel positions. Different pixel positions have different threshold levels to permit a grey area spanning a given group of neighboring pixel positions to be represented by combinations of black-and-white pixels to give the perception of the particular shade of grey when viewed from a distance. For example, for an 8-bit grey-scale spanning from pure black (0) to pure white (255), a medium dark grey of shade level 63 over a block of pixels would be converted into black-and-white pixels with about three times as many black pixels as white.
  • the output of the analog comparator 82 is stored in frame memory 15 and also used to "dither" the threshold values used to process the next frame.
  • a hysteresis-ordered, dither threshold is implemented by inverter 84 and summers 86 and 88 which operate to define a hysteresis band around each threshold value, T Xy ⁇ ⁇ , which serves to reduce flicker in the analog comparator 80.
  • a set of illustrative threshold values for the ordered dither threshold table are shown in FIG. 4.
  • the 128 x 128 pixel image is broken down into 4 x 4 pixel blocks. There are 32 x 32 superblocks of these 4 x 4 blocks.
  • the threshold values are selected to create a line-type dither pattern, which facilitates greater data compression in the preferred embodiment of the differential image encoding stage.
  • a 1-dimensional, Modified Huffman run-length encoding scheme compresses data effectively where there is a long series of the same value.
  • grey-scale 63 would result in alternating black-and-white pixels on the first row, all black pixels on the second row, alternative black-and-white pixels on the third row, and all black pixels on the fourth row. For a given 4 x 4 block, this results in 12 black pixels and four white pixels -- exactly the desired 3-to-1 ratio. In addition, the efficiency of the run-length encoding will be maximized by this dithered pattern as every other row consists of continuous black pixels.
  • the preferred embodiment includes a hysteresis adjustment of the dithered threshold values.
  • the hysteresis adjustment increases the threshold value for a given pixel position if the corresponding pixel position in the previous image frame is black, and decreases the threshold value if the corresponding pixel position in the previous frame is white.
  • the second position in the second row of the matrix has a threshold value of 64, which is very close to level 63.
  • each dither threshold is adjusted by a predetermined amount to ensure any change in shade is sufficient to warrant toggling of the pixel value.
  • the new image is compared to the threshold values to transform the multiple grey-scale image into a halftone image.
  • the adjusted dithered threshold value is converted from digital to analog in a D-to-A converter 90 and sent along with the reduced analog image to the analog comparator 80.
  • Each reduced analog pixel value that is greater than the adjusted analog threshold value becomes a digital output of 1 or white; each reduced analog pixel value that is less than the adjusted analog threshold value becomes a digital output of 0 or black.
  • the analog comparator 80 also converts the compared results into digital values for each pixel.
  • the digital output from the analog comparator 80 i.e., the first level compressed image
  • the output of the XOR gate is 0.
  • the output of the XOR gate is 1.
  • this data is also sent to the frame memory 15 to replace the currently-stored pixel values.
  • the new digital values representative of the halftone image replaces the old values in the frame memory 15 representative of the previous halftone image frame. This updates the frame memory 15 for processing of the next frame in time.
  • the final data compression stage is the differential image encoding scheme, as shown in FIG. 1.
  • the preferred embodiment is a 1-dimensional Modified Huffman run-length code. This encoding scheme transforms long series of 0 or 1 bits into shorter codes. Integrated circuits for implementation of such encoding techniques are commercially available, e.g., the AM7971 compression-expansion processor chip (Advanced Micro Devices, Inc., Sunnyvale, California). Alternative embodiments may be substituted for the 1-dimensional Modified Huffman code, such as the 2-dimensional Modified Huffman code, and other variations.
  • the encoded differential image values may either be directly sent over a transmission line or multiplexed and modulated with audio portion for simultaneous transmission over the same bandwidth.
  • FIG. 6 illustrates this process.
  • the video signal from the encoder is processed by image modulating module 26 comprising a delay modulator 76 and mixer 78.
  • the incoming video signal essentially a binary bit stream, is converted into a rectangular waveform of two levels according to the following rules: a transition from one level to the other level is placed at the midpoint of the bit cell when the binary data contains a one. No transition is used for a zero unless it is followed by another zero, in which case the transition is placed at the end of the bit cell for the first zero.
  • the resulting waveform is then low pass filtered to remove higher harmonics and yields an analog signal which lies within the 0 - 3 kHz range.
  • delay modulation see, Hecht et al., "Delay modulation", Vol. 57, Proc. IEEE
  • the processed video portion is then modulated by a cosine function to permit coherent (in-phase and quadrature) modulation and added to the audio portion, which is similarly modulated with a sine function.
  • a frequency and phase recovery unit 40 detects and tracks the phase at which the signal arrives; and demodulators 43, 45 separate the sine and cosine components of the signal, providing an audio and a video signal.
  • the video signal is then further processed by a delay demodulation 79 to recover the original binary bit stream.
  • demultiplexing and demodulation unit 42 can also include filter elements 83 and 85 and a video/audio recovery module 87 (shown in dotted lines in FIG. 6) to suppress cross talk.
  • the output of low pass filter 85 is an audio signal r 1 and the output of high pass filter 83 is a video signal r 2 .
  • the signals r 1 and r 2 contain the transmitted audio and video signals plus additional cross-talk terms. They have the form
  • T 1 [s video ] and T 2 [s video ] are the cross-talk terms. If they were absent, r 1 would be the audio signal and r 2 would be the video signal.
  • T 1 [] and T 2 [] are tranformations defined by the processing steps carried out between the transmitter and the receiver.
  • the transform functions encompass the filtering as well as the multiplication operations (e.g., multiplication by the carrier and its quadrature) that occur during modulation and multiplexing.
  • a udio r 1 - T 1 [ video ]
  • v ideo r 2 - T 2 [ audio ]
  • a three-step recursive process can be used to recovering the audio and video signals, as shown in FIG. 7.
  • an initial estimate of s aud io (t) is produced by applying the transform function T 1 to an initialization value of s video (t) in element 93.
  • This initial value s° can be obtained from a previous image frame (with an appropriate delay) or, during start-up, from an initialization signal.
  • the transform T 1 [s video (t)] is then subtracted from r 1 in summer 94 to obtain the initial estimate of s audio (t).
  • an estimate of s video (t+ ⁇ ) is produced, by applying the transform function T 2 to the estimate of s audio (t) (obtained in step one) in element 93 and then subtracting this transformed signal from r 2 (t+ ⁇ ) in summer 96.
  • the delayed signal, r 2 (t+ ⁇ ) is obtained by passing the received video signal r 2 through delay element 97.
  • the factor ⁇ compensates for time delays inherent in the transformations T 1 and T2. (Although these delays may be different, for purposes of illustration they are assumed to be the same.)
  • the output of summer 96 is an estimate of video signal, s video (t+ ⁇ ).
  • s audio (t+2 ⁇ ) is produced by applying a delayed transform of T 1 to the estimate of s v (t+ ⁇ ) in element 98 and then subtracting this tranformed signal from 1(t+2 ⁇ ) in summer 99 to yield a refined audio estimate s audio (t+2 ⁇ ).
  • the results of step two and three are the outputs of the recovery system.
  • the time delay, ⁇ , associated with T1 and T2 is less than one millisecond, a delay which is normally imperceptible to the users.
  • an alternative modulation apparatus including data encoder 22, error corrector encoder 24, delay modulation 31, audio high pass filter 31, and mixer 35, in the transmitter section and filter elements 36, 37 and delay demodulator 39, in the receiver section.
  • This amplified system is based on the observation that the necessary video data rate for normal use of a video telephone (e.g., without handwaving or gross head movements) is about 2,400 bits per second (b/s).
  • the delay modulator for a 2,400 b/s input stream can produce an analog signal in a band ranging from 0 to about 1100 Hz.
  • the audio and video signals can be frequency division multiplexed (FDM). That is, the video signal lies in the 0 to 1100 band.
  • the audio signal lies in the 1100 to 3000 (or higher) band.
  • the loss in audio signal-to-noise would be about 25 percent on dB, which is tolerable over most telephone channels.
  • the video signal in the 0 to 1100 band can also be moved to another part of the band by modulation. Such a relocation of the video signal may be desirable to reduce its effect on the voice quality (insofar as much of the energy in normal voice signals lies below 2000 Hz.) For example, by modulating with a 1000 Hz carrier, the video can be moved to the 1300 to 2100 band.
  • a carrier recovery system similar to that discussed previously, can then be used to synchronize the transmitter and receiver for demodulation.
  • the frequency bandwidth can be further divided to provide a first band for chrominance information, a second band for luminance information and a third band for audio information.
  • color information can be transmitted over a narrow band of nominal frequency from 0 to 500 Hz. The selection of particular frequency ranges for such bands is within the ordinary abilities of those skilled in the art.
  • all of the signals can be multiplexed over time, rather than frequency.
  • FIG. 4 shows a block diagram.
  • the disadvantage is its loss of audio signal-to-noise ratio and its limitation in tracking motion in the video image. There may be applications where these disadvantages are unimportant.
  • FIGS. 9A-9D illustrate an image averaging process useful in the image averaging unit 56 of receiver 38 shown in FIG. 1.
  • 5 x 6 blocks of pixel values are averaged with the averaged value being applied to the pixel situated in the upper left hand corner of the block. This provides 30 shades of grey.
  • FIG. 9A an initial pixel value is averaged; in FIG. 9B, the pixel in the next column is averaged using a 5 x 6 matrix of pixel values, which is displaced one column to the right.
  • FIG. 9C a pixel in the next row relative to the pixel illustrated in FIG. 9A is shown. This pixel is averaged using a 5 x 6 matrix of pixel values which is displaced one row downward relative to the matrix of FIG. 9A.
  • FIG. 9D the averaging process is illustrated for a pixel one row below and one column to the right of the original pixel shown in FIG. 9A.
  • image averaging unit 56 can also be employed in the image averaging unit 56 to reduce the "blockiness" of the picture.
  • spatial filtering techniques can be used to average pixel values across a line or from one line to the next.
  • interpolation techniques can be used to "fill-in" additional data values (e.g., intermediate values between pixels or between lines).
  • the pixel averaging unit 56 in transmitter 38 can further include means for interpolating pixel values to improve the resolution of the reconstructed image. The effect of such interpolation is to smooth out the discontinuities in the reconstructed image, provide a subjectively more pleasing image and allow the use of a larger display at the receiving end. These interpolation functions can take place entirely at the receiving end. No modification is required at the transmitter.
  • the original scene is described by N samples per line and M lines per frame, corresponding the MxN picture elements or pixels per frame.
  • the receiver calculates the luminance levels at each of the MxN pixels.
  • the pixel averaging unit 56 can further include a resolution multiplier which introduces additional interpolation points or pixels in the reconstructed signal, specifically, between any two consecutive pixels in a same row or in a same column. When one interpolation point is added between any two original pixels, the total number of pixels per frame is multiplied by 4.
  • the resolution multiplier can proceed as follows:
  • step one interpolated columns are generated.
  • a new pixel, P i,j+1/2 is added halfway between pixels P ij and P i,j+1 .
  • Its luminance, b i , j +1/2 is equal to:
  • b ij + (1-a) b i,j+1 , if b i,j+2 > 2 b i,j+1 - b ij 1/2 b ij + 1/2 b i,j+1 , if b i,j+2 2 b i,j+1 - b ij (1-a) b ij + a b i,j+1, if b i,j+2 ⁇ 2 b i,j+1 - b ij
  • a is a selectable parameter which can range typically from 0 to about 1/2.
  • One suitable value of a is 1/4.
  • step two a similar process can be employed to interpolate rows.
  • P i+1/2,j is added half way between pixels P ij and P i+i,j .
  • Its luminance, b i+1/2,j is equal to:
  • the number of pixel values per frame is 4MN consisting of MN original pixel values, and new 3MN interpolated pixel values.
  • This enhancement process can be repeated any number of times. It will result each time in a quadrupling of the number of pixels values within each frame.
  • a system 100 is shown that provides for adaptive resolution in image processing. Adaptive resolution provides a means to enhance the resolution of the received picture depending upon the degree of motion existing in the original scene. For example, when there is animated motion in the scene (e.g., rapid head movement during a videophone conversation), the basic resolution techniques described above can be applied. However, when there is slow motion in the original scene
  • system 100 includes a transmitter section 112 having a grey-scale reduction unit 102, a multi-frame buffer 104, a motion estimation unit 106, a threshold look-up table 108, differential image buffer 114, reference frame buffer 116, image date encoders (e.g. run length and Huffman coding elements) 118, and channel buffer 120, as well as control circuit 110.
  • the receiver 138 includes image data decoders 140, differential buffer 142, reference frame buffer 144, a multi-frame buffer 146, and a grey-scale computer 150.
  • the image data is compressed by the grey scale reduction unit 102 to yield binary luminance values.
  • Unit 102 applies threshold matrices to the incoming data (using the look-up tables stored in element 108) in a manner analogous to that described above in FIGS. 1-5.
  • a multiframe buffer 104 is used to store a series of binary frame values. These values are then compared by motion estimator 106 to determine the motion state (e.g., fast, intermediate or slow). Depending on the motion state, different threshold values are selected from element 108.
  • Differential buffer 114 contains the changes between the last received frame in buffer 104 and the reference frame from buffer 116.
  • the contents of the reference frame buffer 116 are updated at different times depending on the motion state, as described in more detail below.
  • the contents of the reference buffer will be the last f rame when fast motion is occurring , or wi ll be an average of the four most recent frames for intermediate motion, or will be an average of sixteen frames during the slow motion operating mode.
  • the motion estimator 106 estimates the average amount of motion existing in the original scene between two instants in time. Motion estimation is an ongoing process at the transmitter, and every frame, a new motion estimate is generated. This estimate is used to either keep the resolution level unchanged or switch to a different resolution level. For example, if L is a number representing the maximum level of motion allowed on the transmission channel, then a fast motion state can be defined as existing when the motion estimate is between the maximum motion level L and L/4. An intermediate motion state can be defined to exist when the motion estimate is between L/4 and L/16. A third state --slow motion-- can be defined to exist when the motion estimate is less than L/16.
  • a change in. the motion level in the scene can be signalled by the transmitter 112 to the receiver 138 by imbedding into the transmitted video bit stream a "resolution sync word" consisting of two additional bits of information per frame.
  • a "resolution sync word” consisting of two additional bits of information per frame.
  • motion estimation is based on the differential information, D(n), D(n-1), D(n-2), D(n-3) which represent the changes which have occurred over the four most recent frames.
  • the differential information at frame F(n) is equal to the difference between binary (i.e. black-and-white) frame F(n) and the previous binary frame F(n-1):
  • F(n) is a binary matrix of 0's and 1's. Let sum [M] be the sum of all the elements of the matrix M. Then, the motion estimate at the time n, ME(n), can be defined as:
  • the motion estimate represents the total number of bit changes that have occurred over the past four frames. This provides a reading of the motion level at the end of each frame.
  • the four-frame averaging process and the readout of the motion estimate are synchronized to the frame sync.
  • a coarse resolution level is used (e.g., same as described above in connection with FIGS. 3 and 4).
  • G i,j (n) F i+k,j+1 (n)
  • the grey level can be calculated as:
  • the notation (pxp,q) is used to represent this class of grey level estimates.
  • the notation underlines the fact that the spatial sum of the binary values over a block of size pxp and the time sum over q frames. With this notation, a three grey level estimation scheme is illustrated in FIGS. 11A, 11B and 11C.
  • FIG. 11A illustrates the course resolution level in which spatial averaging over a 4x4 pixel block from a single frame is used to derive a binary value in the grey-scale reduction unit.
  • FIG. 11B illustrates the intermediate resolution level, where the grey level of a pixel is derived from both spatial averaging over a 2x2 block and time averaging over 4 successive frames.
  • FIG. 11C illustrates the fine resolution level, where the averaging is over a 1x1 block, or 1 pixel, and over 16 successive frames. There is no spatial averaging, but only time averaging.
  • the grey level resolution (e.g. thresholds) can be left unchanged at 16 levels or 4 bits of grey.
  • n different threshold matrices are used.
  • the procedure uses one 4x4 threshold matrix, M, at the coarse resolution level, four 2x2 threshold matrices. M1 to M4, at the intermediate resolution, and 16 threshold levels at the fine resolution.
  • the threshold matrices M, M1, M2, M3, M4 are given in FIGS 11A and 11B.
  • the 16 sealer thresholds are the values 16, 32, 48, ... up to 256, i.e., values multiple of 16, as illustrated schematically in FIG 11C. These matrices are for illustration purposes and other matrices can perform equally well.
  • a multi-frame buffer 104 is used in the transmitter 112 to calculate the motion level in the scene.
  • a four-frame buffer is sufficient to calculate the estimate, once every frame.
  • Reference buffer 116 is used to calculate the motion estimate and generate the differential information. While in the coarse resolution mode or when switching to the coarse resolution mode, the previously-received frame can be used as the reference frame for calculating the differential information. The same convention is used at the receiver. The decision to switch to a different resolution level (such as intermediate or fine) can occur at the end of any frame.
  • the transmitter does not switch to another resolution (coarse or fine) until all four differential frames have been transmitted. At that point, whether a resolution switch occurs or not, the last transmitted frame becomes the new reference frame. If one assumes instead that a decision to switch to fine resolution occurred at the end of frame F(n), then this frame is used as the reference for the next 16 frames:
  • controller 110 can be used to desensitize the updating mechanism of the differential buffer 114 based upon conditions in the channel buffer 120.
  • controller 110 can increase hysteresis by incrementing the dither parameter ⁇ , thereby making it more difficult to toggle a particular pixel and, hence, reducing the number of pixel changes recorded in the differential buffer 114. This same mechanism also provided flicker control.
  • a multi-frame buffer 146 can be used to store data values over a series of frames so that the grey-level computer 150 can calculate the grey levels, e.g., by spatial averaging in the fast motion mode, by space and time averaging over four frames in the intermediate motion mode, or by time averaging over 16 frames in the slow motion mode.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Databases & Information Systems (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)
  • Compression Of Band Width Or Redundancy In Fax (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Telephone Function (AREA)
  • Telephone Set Structure (AREA)

Abstract

Systèmes et techniques de compression de données d'images différentielles, utilisés dans des systèmes de visiophones permettant la transmission en duplex intégral, en temps réel, d'images audio et vidéo par des lignes téléphoniques privées nominales de trois kHz ainsi que d'autres canaux de largeurs de bande étroites. Chaque dispositif de vidéophone comprend une partie de transmission (12) et une partie de réception (38). Dans la section de transmission (12) une image d'échelle de gris (luminance) réduite, composée de préférence uniquement de pixels noirs et blancs, est comparée dans un module de traitement d'image (20) ayant une image réduite de manière analogue dérivée de valeurs préalables afin de déterminer les positions des pixels ayant changé. Ensuite, les informations représentant les changements sont codées et modulées, puis elles sont multiplexées (temps ou fréquence) à l'aide des signaux audio et/ou de chrominance afin d'être transmises. Au niveau du récepteur (38), le signal entrant est démodulé et démultiplexé afin de séparer les parties audio et vidéo, la partie image est décodée et la valeur de luminance est mise à jour à l'aide d'une unité de mise à jour d'image (50). L'invention concerne également des techniques d'obtention de moyenne et d'interpolation de pixels à résolution adaptative, permettant d'améliorer les images.
PCT/US1990/007649 1989-12-28 1990-12-26 Systemes de visiophones WO1991010328A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6603515B2 (en) 1997-09-02 2003-08-05 Nokia Mobile Phones Ltd. Video data transmission
CN101917622A (zh) * 2010-08-24 2010-12-15 中国科学院光电技术研究所 14bit位宽图像压缩硬件编码器
RU2633179C1 (ru) * 2011-12-13 2017-10-11 ДжейВиСи КЕНВУД КОРПОРЕЙШН Устройство, способ и программа кодирования движущихся изображений, и устройство, способ и программа декодирования движущихся изображений

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6124882A (en) * 1992-02-19 2000-09-26 8×8, Inc. Videocommunicating apparatus and method therefor
US6121998A (en) * 1992-02-19 2000-09-19 8×8, Inc. Apparatus and method for videocommunicating having programmable architecture permitting data revisions
JP2001028763A (ja) * 1999-04-29 2001-01-30 Mitsubishi Electric Inf Technol Center America Inc コントローラからビデオ表示ユニットに画像データを転送する方法、ビデオ表示ユニットアダプタ、ビデオ表示システム、並びにテレビ表示画面上への提示のために画像データをダブルバッファリングする方法
EP1387340A1 (fr) 2002-07-30 2004-02-04 Deutsche Thomson-Brandt Gmbh Procédé et dispositif pour le traitement des données d'image vidéo pour un dispositif d'affichage
EP1387343B1 (fr) * 2002-07-30 2009-03-25 Thomson Licensing Méthode et dispositif de traitement de données video pour affichage sur un dispositif d'affichage
US8914734B2 (en) 2009-12-23 2014-12-16 8X8, Inc. Web-enabled conferencing and meeting implementations with a subscription-based model
US20110149811A1 (en) 2009-12-23 2011-06-23 Ramprakash Narayanaswamy Web-Enabled Conferencing and Meeting Implementations with Flexible User Calling Features
US20110149809A1 (en) 2009-12-23 2011-06-23 Ramprakash Narayanaswamy Web-Enabled Conferencing and Meeting Implementations with Flexible User Calling and Content Sharing Features
US20110150194A1 (en) 2009-12-23 2011-06-23 Ramprakash Narayanaswamy Web-Enabled Conferencing and Meeting Implementations with Flexible User Calling Features
JP2013005204A (ja) * 2011-06-16 2013-01-07 Sony Corp ビデオ送信装置、ビデオ受信装置、およびビデオ送信方法
US8817801B1 (en) 2011-07-08 2014-08-26 8X8, Inc. Conferencing and meeting implementations with advanced features

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0098763A1 (fr) * 1982-06-18 1984-01-18 Inria Institut National De Recherche En Informatique Et En Automatique Procédés et dispositifs de télécommunications visuelles, notamment à l'usage des sourds
US4591907A (en) * 1983-07-13 1986-05-27 Thomson-Csf Method and device for detection of moving points in a television image for digital television systems providing conditional-replenishment bit-rate compression
US4717957A (en) * 1984-12-14 1988-01-05 Valtion Teknillinen Tutkimuskeskus Video compression method

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3937878A (en) * 1975-01-21 1976-02-10 Bell Telephone Laboratories, Incorporated Animated dithered display systems
JP2794281B2 (ja) * 1986-07-10 1998-09-03 株式会社日立製作所 デイザ信号の符号復号処理装置
US4967272A (en) * 1988-01-27 1990-10-30 Communications Satellite Corporation Bandwidth reduction and multiplexing of multiple component TV signals
FR2629595B1 (fr) * 1988-03-31 1991-06-21 Oreal Procede et dispositif pour mesurer l'elasticite d'une couche superficielle, en particulier de la peau

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0098763A1 (fr) * 1982-06-18 1984-01-18 Inria Institut National De Recherche En Informatique Et En Automatique Procédés et dispositifs de télécommunications visuelles, notamment à l'usage des sourds
US4591907A (en) * 1983-07-13 1986-05-27 Thomson-Csf Method and device for detection of moving points in a television image for digital television systems providing conditional-replenishment bit-rate compression
US4717957A (en) * 1984-12-14 1988-01-05 Valtion Teknillinen Tutkimuskeskus Video compression method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IEEE Transactions on Commu- nications, vol. COM-35, no. 6, June 1987, New York HAMID GHARAVI "Conditional Run-Length and Variable- -Length Coding of Digital Pictures" pages 671-677. *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6603515B2 (en) 1997-09-02 2003-08-05 Nokia Mobile Phones Ltd. Video data transmission
CN101917622A (zh) * 2010-08-24 2010-12-15 中国科学院光电技术研究所 14bit位宽图像压缩硬件编码器
CN101917622B (zh) * 2010-08-24 2012-09-05 中国科学院光电技术研究所 14bit位宽图像压缩硬件编码器
RU2633179C1 (ru) * 2011-12-13 2017-10-11 ДжейВиСи КЕНВУД КОРПОРЕЙШН Устройство, способ и программа кодирования движущихся изображений, и устройство, способ и программа декодирования движущихся изображений

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EP0462261A1 (fr) 1991-12-27
JPH04505537A (ja) 1992-09-24
AU7166491A (en) 1991-07-24
CA2048623A1 (fr) 1991-06-29

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