WO1992017032A1 - Systeme d'emission de signal de television avec deux jeux de symboles de canaux - Google Patents

Systeme d'emission de signal de television avec deux jeux de symboles de canaux Download PDF

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Publication number
WO1992017032A1
WO1992017032A1 PCT/US1992/001396 US9201396W WO9217032A1 WO 1992017032 A1 WO1992017032 A1 WO 1992017032A1 US 9201396 W US9201396 W US 9201396W WO 9217032 A1 WO9217032 A1 WO 9217032A1
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WO
WIPO (PCT)
Prior art keywords
signal
symbols
level
level symbols
levels
Prior art date
Application number
PCT/US1992/001396
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English (en)
Inventor
Richard W. Citta
Original Assignee
Zenith Electronics Corporation
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 Zenith Electronics Corporation filed Critical Zenith Electronics Corporation
Publication of WO1992017032A1 publication Critical patent/WO1992017032A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
    • 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
    • H04N19/146—Data rate or code amount at the encoder output
    • H04N19/152—Data rate or code amount at the encoder output by measuring the fullness of the transmission buffer
    • 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
    • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
    • H04N19/37—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability with arrangements for assigning different transmission priorities to video input data or to video coded data
    • 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
    • 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]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/41—Structure of client; Structure of client peripherals
    • H04N21/426—Internal components of the client ; Characteristics thereof

Definitions

  • the present invention generally relates to a system for digitally transmitting a video signal and particularly concerns a system for adaptively improving the signal to noise performance of a digitally transmitted video signal.
  • the compressed video information may be transmitted in the form of motion vectors and difference signals, each motion vector identifying a previous portion of the video signal closely matching the current portion and the difference signal representing the difference between the two portions. Transmission of the motion vector and difference signals may be effected, for example, by encoding the binary data representing the two signals as a series of N-level symbols, each symbol thereby representing N/2 bits of binary data.
  • Each symbol in a 4-level transmission system would therefore represent two bits of binary data.
  • Digital video transmission systems of the foregoing type provide for extremely accurate reproduction of the transmitted image under ideal conditions and can even tolerate a certain degree of interference without appreciable performance degradation. However, if the level of interference encountered exceeds a threshold representing the signal-to-noise performance of the system, the ability to reproduce the televised image may be entirely lost. This is in contrast to an analog transmission system in which performance is gradually degraded as a function of interference. In the HDTV digital transmission environment, one source of such interference is expected to be NTSC co-channel signals from nearby television service areas.
  • Figure 1 is a block diagram of a video signal encoder and transmitter constructed in accordance with the invention
  • Figures 2A and 2B are respective graphs useful in explaining the operation of the encoder of Figure 1;
  • Figure 3A illustrates a technique for formatting video data according to a preferred embodiment of the invention
  • Figures 3B and 3C illustrate the manner in which different segments of the video data of Figure 3A are encoded for transmission at different levels of signal-to-noise performance according to a preferred embodiment of the invention.
  • FIG. 4 is a block diagram of a video signal receiver constructed in accordance with the invention.
  • Figure 1 illustrates a video signal transmitter constructed in accordance with the invention.
  • the transmitter incorporates a temporally based video compression system and utilizes a suppressed carrier, vestigial sideband form of transmission.
  • the invention may be used with other types of video compression and transmission systems so that the details thereof should not be viewed as to impose any unnecessary limitations on the invention.
  • a video source 10 provides a wideband digital video signal which may have a bandwidth of up to about 37 MHz.
  • source 10 may provide, for example, a progressively scanned video signal in the form of successive frames of binary video data having a vertical periodicity equal to the NTSC standard (i.e. about 59.4 Hz) and a horizontal periodicity equal to three times the NTSC standard (i.e. about 47.25 KHz).
  • the video data is applied in the form of a stream of binary pixel values from video source 10 to a transform coder 12 which may, for example, implement a discrete cosine transform.
  • transform coder 12 processes the binary pixel values for providing a series of blocks of spectral transform coefficients for each frame of the video source signal, each block of coefficients corresponding to a respective spatial region of the video image.
  • each block comprises an (8 X 8) array of coefficients, with 14,400 blocks representing an entire video frame.
  • the coefficient blocks developed by transform coder 12 are applied one at a time to a perceptual modeling system 14 which develops an output reflecting the perceptual nature of the corresponding portion of the video image.
  • Perceptual modeling system 14 a preferred embodiment of which is more fully described in copending U.S. application Serial No.
  • a video compression system 16 is responsive to the output of perceptual model 14 for compressing the video signal developed at the output of source 10 in accordance with a selected compression algorithm.
  • video compression is affected in the temporal domain wherein, for example, successive portions of the video image are analyzed to derive a respective motion vector and difference signal.
  • the motion vector identifies a closely matching group of video pixels from the previous frame and the difference signal represents the difference therebetween.
  • the difference signal is preferably variably quantized in response to the output of perceptual model 14 in the form of, for example, either a 0, 3, 5 or 7 average bit-length code and multiplexed with the motion vector to provide an output compressed binary video data signal.
  • the compressed signal developed at the output of compressor 16 is applied to the input of a variable rate buffer 18.
  • Buffer 18 controls the flow of video data in the transmitter by providing a feedback signal to perceptual model 14 which reflects the fullness of the buffer.
  • perceptual model 14 is responsive to the feedback signal for controlling compressor 16 in a manner so as to vary the degree of compression effected thereby as a function of the fullness of the buffer.
  • the extent of compression may likewise be increased and as fullness decreases the extent of compression may also be decreased to provide a relatively continuous flow of video data through the transmitter.
  • Figure 2A which plots the degree of error introduced by compressor 16 as a function of buffer fullness.
  • the error level likewise varies directly with buffer fullness. That is, increased compression provides an increased error level and decreased compression provides a decreased error level.
  • the compressed video data is coupled by buffer 18 to data sorter and formatter unit 20.
  • the video data may comprise a combination of both motion vectors and variably quantized difference signals, although other classes of data may also be provided.
  • Unit 20 sorts the various classes of data (e.g. motion vectors and difference signals) according to their relative importance and likewise ranks the data within each respective class.
  • the data applied to or developed in unit 20 may include various global control data necessary for proper operation of the receivers in the system. This class of data is therefore assigned the highest level of importance.
  • the motion vectors which are considered more important than the difference signals to the accurate reproduction of the televised image, are assigned the next highest level of importance and the difference signals the lowest relative level of importance.
  • Unit 20 next formats the data into a transmission frame, an exemplary embodiment of which is illustrated in Figure 3A, according to the foregoing classification as well as the inter-classification ranking of the data.
  • the exemplary transmission frame shown in Figure 3A is substantially coextensive with an NTSC field v and comprises a plurality of data segments 22 each corresponding to an NTSC horizontal line.
  • the most important class of data i.e. the control data in the foregoing example
  • the next most important class i.e. the motion vectors
  • the difference signals in a final group 28 of data segments 22.
  • the data within each group 24, 26, 28 of data segments 22 is likewise ranked according to its relative importance.
  • the more important motion vectors and difference signals are provided in the initial data segments of their respective groups, while the motion vectors and difference signals of lesser importance are provided in the lower data segments of the groups.
  • the formatted data frames developed by unit 20 are supplied to a level encoder 30 which is operated in response to an encoder 32.
  • Encoder control 32 is in turn responsive to the buffer fullness signal developed by buffer 18.
  • Level encoder 30 is operable for encoding each segment 22 of the transmission frame in the form of about 684 four or two level symbols, each four-level symbol representing two binary data bits and each two-level symbol representing one binary data bit.
  • the output of level encoder 30 thus comprises a successive series of data segments 22 each characterized by a fixed symbol rate of approximately 10.5 megasymbols per second and a data rate of either 21 megabits per second (for four-level symbols) or 10.5 megabits per second (for two-level symbols) .
  • a fixed symbol rate of approximately 10.5 megasymbols per second
  • a data rate of either 21 megabits per second (for four-level symbols) or 10.5 megabits per second (for two-level symbols) .
  • Figures 3B and 3C which respectively represent a four-level data segment 22 and a two-level data segment 22. Referring to Figure 3B, it will be seen that the data segment comprises 684 four-level symbols representing 171 bytes of data.
  • Each 6f the data symbols which are equally spaced by about 92 nanoseconds, assume one of the four exemplary levels 0, 1, 2 or 3 for providing a fixed symbol rate of about 10.5 megasymbols per second and a corresponding data rate of about 21 megabits per second.
  • the data segment of Figure 3C also comprises 684 symbols but only represents about 85 bytes of data corresponding to a data rate of about 10.5 megabits per second.
  • the levels characterizing the symbols of the data segment of Figure 3C are selected from among the levels used to encode the symbols of the data segment of Figure 3B.
  • the symbols of the data segment of Figure 3C are encoded using the levels 0 and 2 of Figure 3B. These levels were selected as representing the best compromise between maintaining a reasonably large difference between the levels while, at the same time, minimizing interference of the transmitted signal into a nearby co-channel.
  • the two-level symbols of the data segment of Figure 3C while providing half the data rate of the data segment of Figure 3B, provide a noise improvement in relation thereto of about 9.5 db.
  • this improvement in noise performance is advantageously utilized by encoding certain of the data comprising segments 22 as two-level symbols in accordance with Figure 3C and other of the data as four-level symbols in accordance with Figure 3B.
  • the division of encoding levels may be set on a fixed basis, may be derived on an adaptively varying basis, or may comprise a combination of both techniques.
  • level encoder 30 is controlled by encoder control 32 to always encode certain data segments 22 of each transmission frame as two-level symbols, other segments 22 as two-level symbols on an adaptively varying basis and the remaining segments 22 as four-level symbols.
  • a pair of partitions 34 and 36 are established for defining the symbol levels to be used for encoding the various data segments.
  • Partition 34 is a fixed partition, while partition 36 is variable between fixed partition 34 and the end of the frame.
  • Data segments above fixed partition 34 are always encoded as two-level symbols, data segments between fixed partition 34 and variable partition 36 as two-level symbols and data segments below variable partition 36 as four-level symbols.
  • fixed partition 34 is selected to define the global control data of data segment group 24 such that this class of data is always transmitted as robust two-level symbols.
  • Variable partition 36 is controlled as a function of the fullness of buffer 18 as illustrated by the nominal curve 40 of Figure 2B. That is, at levels of buffer fullness below fullness threshold T2 variable partition 36 is adjusted downwards to the bottom of the frame and at levels of buffer fullness above fullness threshold Tl variable partition 36 is adjusted upwards to fixed partition 34. For levels of buffer fullness between thresholds Tl and T2, the variable partition is established by encoder control 32 between these two extremes such that the transmission frames are encoded at an average data rate reflected by the portion of curve 40 between thresholds Tl and T2.
  • encoder control 32 inserts a count in the first segment of each transmission frame identifying the number of segments in each frame comprising two-level symbols. Since the count is above fixed partition 34 it will always be encoded as two-level symbols. This count, together with the remaining encoded symbols are coupled to a transmitter 42 for transmission over a 6 MHz television channel.
  • transmitter 30 preferably comprises the vestigial sideband, suppressed carrier transmitter described in copending application Serial No. 611,236, filed November 9, 1990.
  • Nominal curve 40 of Figure 2B may be adjusted by the broadcaster in a tradeoff between the quality of the broadcast and the extent of geographical coverage provided thereby.
  • curve 40 ' of Figure 2B may be employed to control level encoder 30 instead of curve 40.
  • Curve 40' results in a tendency to raise variable partition 36 whereby an increased number of data segments are encoded as four-level symbols to increase the average transmitted data rate. While this improves the quality of the broadcast image, the extent of geographical coverage is reduced as a consequence of the reduction in the average signal-to-noise ratio of the transmitted signal.
  • curve 40" of Figure 2B may be employed to control level encoder 30. Curve 40" results in a tendency to lower variable partition 36 whereby an increased number of data segments are encoded as two-level symbols resulting in a decreased average transmitted data rate. This provides a more robust signal having increased geographical coverage but at a reduced quality level.
  • the transmitted signal is received by a receiver including a tuner 50.
  • Tuner 50 converts the received signal to an intermediate frequency (IF) signal which is applied to a synchronous detector 52 and to a frequency and phase lock loop (FPLL) 54.
  • FPLL 54 locks to the applied IF signal and generates a continuous wave output for application to synchronous detector 52.
  • FPLL 54 may also may also generate an automatic frequency control voltage for controlling the operation of tuner 50.
  • Synchronous detector 52 in response to the output of FPLL 54, demodulates the received signal and applies the demodulated signal to the inputs of a data decoder 56 and a clock and sync recovery circuit 58.
  • the demodulated count signal identifying the number of segments of each received frame encoded as two-level symbols is coupled to a second input of data decoder 56.
  • Circuit 58 applies a clock signal to a third input of data decoder 56 and appropriate sync signals for controlling a display 60.
  • Data decoder 56 is responsive to the count and clock signals for decoding the demodulated segments of two and four-level symbols coupled thereto.
  • the decoded signal is applied through a buffer 62 as a fixed rate binary signal to a video processor 64 which decompresses the received signal to provide a wideband video output signal. It will be understood that since at least the most important portions of the received video signal were transmitted and received as relatively noise-immune, two-level symbols, highly accurate reproduction of corresponding portions of the image is achieved. Depending on the level of noise encountered during transmission, the remaining four-level symbols may be reproduced with the same or less accuracy. Finally, the decoded video data developed by processor 64 is applied through a D/A converter 66 to display 60 for reproducing the televised image.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

Un bloc de données vidéo comprimé est structuré, pour l'émission en une pluralité de segments de données, dont un premier groupe est codé sous la forme d'une pluralité de symboles à quatre niveaux et un second groupe est codé sous la forme d'une pluralité de symboles à deux niveaux pour obtenir des performances améliorées en ce qui concerne le bruit. La séparation entre le premier et le second groupe de segments de données peut être établie sur une base fixe, une base variable dépendant du niveau effectif de compression, ou à partir d'une combinaison des deux. De préférence, les deux niveaux du second groupe comprennent un sous-ensemble des quatre niveaux du premier groupe.
PCT/US1992/001396 1991-03-12 1992-02-21 Systeme d'emission de signal de television avec deux jeux de symboles de canaux WO1992017032A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US66783691A 1991-03-12 1991-03-12
US667,836 1991-03-12

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WO1992017032A1 true WO1992017032A1 (fr) 1992-10-01

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PCT/US1992/001396 WO1992017032A1 (fr) 1991-03-12 1992-02-21 Systeme d'emission de signal de television avec deux jeux de symboles de canaux
PCT/US1992/001560 WO1992017030A1 (fr) 1991-03-12 1992-02-26 Systeme de transmission de signaux de television, presentant deux niveaux de codage des symboles

Family Applications After (1)

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PCT/US1992/001560 WO1992017030A1 (fr) 1991-03-12 1992-02-26 Systeme de transmission de signaux de television, presentant deux niveaux de codage des symboles

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EP (1) EP0575530A1 (fr)
JP (1) JPH06506331A (fr)
CA (1) CA2106002A1 (fr)
WO (2) WO1992017032A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0609017A2 (fr) * 1993-01-29 1994-08-03 AT&T Corp. Schéma de transmission à divers debits de canal pour blocs codés de signal vidéo
EP0775422A1 (fr) * 1994-06-15 1997-05-28 RCA Thomson Licensing Corporation Appareil pour mettre au format un flux de donnees numeriques mises en paquets convenant au transport d'informations de television
US5831690A (en) * 1996-12-06 1998-11-03 Rca Thomson Licensing Corporation Apparatus for formatting a packetized digital datastream suitable for conveying television information

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Publication number Priority date Publication date Assignee Title
US5461619A (en) * 1993-07-06 1995-10-24 Zenith Electronics Corp. System for multiplexed transmission of compressed video and auxiliary data

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IEE Proceedings Section, vol. 133, no. 4, part F, July 1984, (Stevenage, Herts, GB), M. TOMLINSON et al.: "Digital pseudo-analogue satellite TV transmission system", pages 384-398, see abstract; page 386, left-hand column, lines 7-11; page 390, section 4.2: "Transmission format"; figures 11,14 *
IEEE Transactions on Communications, vol. COM-31, no. 3, March 1983, (New York, US), D.G.DAUT et al.: "Two-dimensional DPCM image transmission over fading channels", pages 315-328, see abstract; page 317, left-hand column, line 28 - right-hand column, line 19; figure 2 *
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0609017A2 (fr) * 1993-01-29 1994-08-03 AT&T Corp. Schéma de transmission à divers debits de canal pour blocs codés de signal vidéo
EP0609017A3 (fr) * 1993-01-29 1994-12-14 At & T Corp Schéma de transmission à divers debits de canal pour blocs codés de signal vidéo.
EP0775422A1 (fr) * 1994-06-15 1997-05-28 RCA Thomson Licensing Corporation Appareil pour mettre au format un flux de donnees numeriques mises en paquets convenant au transport d'informations de television
EP0775422A4 (fr) * 1994-06-15 1997-07-30 Rca Thomson Licensing Corp Appareil pour mettre au format un flux de donnees numeriques mises en paquets convenant au transport d'informations de television
US5831690A (en) * 1996-12-06 1998-11-03 Rca Thomson Licensing Corporation Apparatus for formatting a packetized digital datastream suitable for conveying television information

Also Published As

Publication number Publication date
EP0575530A4 (fr) 1994-02-23
WO1992017030A1 (fr) 1992-10-01
EP0575530A1 (fr) 1993-12-29
CA2106002A1 (fr) 1992-09-13
JPH06506331A (ja) 1994-07-14

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