EP0558704A1 - Decoding of composite television signals - Google Patents

Decoding of composite television signals

Info

Publication number
EP0558704A1
EP0558704A1 EP92917600A EP92917600A EP0558704A1 EP 0558704 A1 EP0558704 A1 EP 0558704A1 EP 92917600 A EP92917600 A EP 92917600A EP 92917600 A EP92917600 A EP 92917600A EP 0558704 A1 EP0558704 A1 EP 0558704A1
Authority
EP
European Patent Office
Prior art keywords
signal
test signal
correction
derived
level
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP92917600A
Other languages
German (de)
French (fr)
Inventor
Michael George 10 Athelstan Way Croll
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Broadcasting Corp
Original Assignee
British Broadcasting Corp
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 British Broadcasting Corp filed Critical British Broadcasting Corp
Publication of EP0558704A1 publication Critical patent/EP0558704A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/64—Circuits for processing colour signals
    • H04N9/646—Circuits for processing colour signals for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00—Diagnosis, testing or measuring for television systems or their details
    • H04N17/02—Diagnosis, testing or measuring for television systems or their details for colour television signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/20—Circuitry for controlling amplitude response
    • H04N5/205—Circuitry for controlling amplitude response for correcting amplitude versus frequency characteristic
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/21—Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
    • H04N5/211—Ghost signal cancellation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/64—Circuits for processing colour signals

Definitions

  • the present invention relates to the field of composite television broadcasting systems and in particular to a method and apparatus for reducing the effect of differential distortions on demodulated broadcast video signals.
  • a method for reducing the effect of differential distortion on demodulated composite television signals comprising the steps of: broadcasting a test signal at predetermined intervals, the test signal including a component at at least one average video signal level; receiving the test signal at a receiver, the receiver being adapted to carry out the steps of: measuring the distortion of the video signal at the said at least one average video signal level; deriving the required correction at that signal level; and applying the said derived required correction to subsequently received broadcast video signals at that signal level.
  • the present invention also provides a test signal for use in the above method, comprising one line of a composite television signal having an identifying portion to identify it as a test signal and having high frequency components at at least three average video signal levels.
  • the test signal may be transmitted once per frame or over a longer period with successive test signals being spaced by several seconds.
  • the method of the present invention may include the step of measuring the amplitude and phase distortion for a range of average video signal levels of the test signal and deriving a correction to be applied to subsequently received broadcast signals for each such distortion at each of the measured average video signal levels.
  • a correction to be applied to subsequently received broadcast signals for each such distortion at each of the measured average video signal levels.
  • the derived corrections may be interpolated or extrapolated to derive the correction to be applied at average video signal levels other than the signal levels of the test signal components.
  • the corrections are applied to subsequently received broadcast signals at closely spaces signal levels to give a smoothly varying correction which adds no visible distortions to the broadcast signal.
  • a receiver adapted to receive and demodulate a composite television signal, including: a test signal detector operable to detect a test signal broadcast at predetermined intervals; measurement apparatus adapted to determine the level of differential amplitude and/or phase distortion of the received test signal at at least one average video signal level and to derive the correction required to reduce the distortion at that signal level or levels; storage means connected to receive the derived required correction or corrections; and signal processing apparatus adapted to apply the required correction or corrections to subsequently received television signals at the average video signal level or levels for which the correction or corrections was derived.
  • the receiver operates to derive and apply corrections in the way described above.
  • the apparatus may be implemented in analogue or digital circuitry or, where the receiver includes a high speed computer, certain of the apparatus operations may be implemented in software.
  • the present invention provides a broadcast system, including a transmitter configured to modulate and transmit a composite television signal including the test signal, and at least one receiver of the type described above.
  • a broadcast system including a transmitter configured to modulate and transmit a composite television signal including the test signal, and at least one receiver of the type described above.
  • differential distortion of the broadcast signals may be corrected more accurately than by the average correction methods currently known and used.
  • Figure 1 is a general schematic diagram of the correction derivation and application stages of the receiver of the present invention
  • Figure 2 shows two suitable forms of the test signal of the present invention.
  • Figure 3 is a schematic diagram showing the receiver stages of Figure 1 implemented in digital circuitry.
  • test signals are in the form of a broadcast line signal including high frequency components which may be measured at at least three different average video signal levels.
  • the first signal 10A shown in Figure 2A is in the form of a television line ramp and the second 10B, in Figure 2B, is in the form of a television line staircase. Both signals shown are augmented by a subcarrier.
  • Signals of this type are easy to detect, being identified by a preceding chrominance burst 12 of at least 20 microseconds duration.
  • the circuitry measuring the test signal distortion and deriving the corrections required to minimise its effect includes storage for the corrections to allow them to be applied to successive received television broadcast signals. It is therefore the case that the test signal, which sets up the stored corrections, need be transmitted only sufficiently often to ensure that there is no appreciable delay in obtaining a good picture after the viewer has changed channel or after a change in received signal quality as a result of changes to the signal path for distribution, transmission or reception. Accordingly, whilst the test signal may be transmitted once per frame, lower repetition frequencies such as once per second or once per ten seconds may be used.
  • the receiver circuitry which derives and applies the required correction of amplitude and phase distortion affecting one signal frequency (colour subcarrier) at different average video signal levels is shown in Figure 1.
  • the television broadcast signal including at periodic intervals the test signal, is received and demodulated by the receivers vision demodulator 20.
  • the demodulated signal 22 is applied to measurement apparatus 24 which measures the difference between the chrominance level of the received (distorted) signal and an expected chrominance level for the transmitted test signal and derives a correction which will minimise the effect of the distortion.
  • the derived corrections 26 are then stored in a memory 28 at address locations 30 determined by the average luminance level of the demodulated signal 22.
  • the average luminance level, and hence the memory address locations 30, are derived by passing the demodulated signal 22 through a suitable low-pass filter arrangement 32.
  • a test signal detector 34 is provided. When a test signal is received, identified as such by the preceding 20 us chrominance burst 12 ( Figure 2), the detector 34 generates a write-enable signal 36 which allows derived corrections to be written into the memory 28 for the duration of the test signal.
  • control of the equaliser 38 may be achieved by a number of established methods.
  • the stored corrections are passed through an interpolator 40 prior to application by the equaliser 38.
  • the interpolator 40 derives further required corrections to be applied at average video signal levels other than those for which the measurement apparatus 24 measured the distortion of the test signal.
  • Use of the interpolator 40 allows the corrections to be applied at closely spaced average video signal levels to provide a smoothly varying correction which adds no visible additional distortions to the video signal.
  • FIG. 3 A more detailed implementation of the receiver circuitry is shown in Figure 3.
  • the distortion is measured and the corrections derived from the test signal of Figure 2A (the television line ramp).
  • the output from the receivers vision demodulator 20 is digitised by an analogue to digital converter 42: this allows the subsequent measurement and correction stages to be defined in terms of known digital operations although it will be appreciated that some of these stages could be implemented in analogue circuitry.
  • the digitised output from the analogue to digital converter 42 is applied to a chrominance demodulator 44.
  • the chrominance demodulator 44 which could be the normal receiver demodulator, is shown in Figure 3 as a separate demodulator for the sake of clarity.
  • the demodulated chrominance components U,V are applied to the measurement apparatus 24.
  • the amplitude of the demodulated signal is calculated, in a PROM (programmable read-only memory) 24A, as the root of the sura of the squares of the two demodulated colour components U,V.
  • the phase of the demodulated signal is also calculated in a PROM 24P as the inverse tan ratio of the two demodulated colour components U,V.
  • the corrections are stored at memory address locations 30 derived from the average luminance level of the demodulated signal by a low pass filter 32. As also described, these corrections may only be stored when a write-enable signal 36 from a test signal detector 34 indicates the presence of a test signal.
  • the equaliser 38 is an adjustable transversal equaliser having a signal input 50 for the demodulated broadcast video signal and separate symmetric 52 and anti-symmetric 54 control inputs.
  • the amplitude correction signal is applied to the symmetric control input 52: amplitude correction is achieved by varying the size of the signal coefficients symmetrically about the centre of the filter.
  • the phase correction signal is applied to the anti-symmetric control input 54: phase correction is achieved by varying the size of the signal coefficients anti-symmetrically about the centre of the filter.
  • averaging circuits may be provided around the correction memories 28A, 28P. Such averaging circuits may average successive test signals prior to measurement of distortion or may average successively derived corrections for a given average video signal level.
  • the method of the present invention may be implemented in software.
  • the schematic diagrams of figures 1 and 3 may be regarded as flow charts representing the steps of a software decoding and correction process.
  • the decoding and correction circuitry of the present invention may also include means for correcting static losses within the receiver to compensate for multipath effects, receiver and/or transmitter responses and the low frequency effects of mistuning.

Abstract

On décrit un système de transmission, dans lequel les effets des distorsions différentielles sur les signaux de télévision composites sont réduits. Selon des intervalles prédéterminés, le signal transmis comporte un signal d'essai possédant des composantes hautes fréquence à au moins trois niveaux de signaux vidéo moyens. Dans un récepteur équipé de manière appropriée, suite à la démodulation effectuée par le démodulateur de vision du récepteur (20), un signal d'essai est identifié par un détecteur de signaux d'essai (34). Un appareil de mesure (24) permet alors de mesurer la distorsion du signal d'essai à un certain nombre de niveaux de signaux vidéo moyens; de calculer la correction nécessaire pour minimiser l'effet de distorsion pour chaque niveau de signaux mesuré et de stocker les corrections dans une mémoire (28) à des emplacements adressés dérivés du signal démodulé par un circuit de filtrage. Les corrections stockées sont appliquées à un interpolateur (40) qui dérive des corrections supplémentaires pour d'autres niveaux de signaux vidéo moyens, les corrections dérivées étant appliquées à des signaux de télévision reçus par un égaliseur (38) à commande.A transmission system is described in which the effects of differential distortions on composite television signals are reduced. At predetermined intervals, the transmitted signal includes a test signal having high frequency components at at least three average video signal levels. In a suitably equipped receiver, following demodulation by the receiver's vision demodulator (20), a test signal is identified by a test signal detector (34). A meter (24) then measures the distortion of the test signal at a number of average video signal levels; calculating the correction necessary to minimize the effect of distortion for each signal level measured and storing the corrections in a memory (28) at addressed locations derived from the signal demodulated by a filter circuit. The stored corrections are applied to an interpolator (40) which derives additional corrections for other average video signal levels, the derived corrections being applied to received television signals by a controlled equalizer (38).

Description

DECODING OF COMPOSITE TELEVISION SIGNALS
Technical Field:
The present invention relates to the field of composite television broadcasting systems and in particular to a method and apparatus for reducing the effect of differential distortions on demodulated broadcast video signals.
Background Art:
It is a known problem of PAL, NTSC and other similar composite television broadcasting systems that the broadcast signal is often subject to amplitude and phase distortions. These distortions are usually introduced to the signal as a result of modulation of the signal onto a high frequency carrier signal prior to transmission and demodulation of the transmitted signal at the receiver. Several factors contributing to the distortion of the video signal are influenced by the mean level of the modulated signal carrier with the result that, when the video signal is demodulated, the distortions become differential distortions which vary with the mean level of the signal.
While these distortions are allowed for in the design of known composite television signal receivers, by the use of delay-line decoders and a saturation control in PAL system receivers and by the use of hue and saturation controls in NTSC receivers, these measures allow only an average correction to be applied. In order to improve the quality of signal that can be delivered by existing terrestrial television systems and by new television systems which use the established composite coded signal methods, improved receivers employing more accurate distortion correction methods are required.
Disclosure of Invention:
In accordance with the present invention, there is provided a method for reducing the effect of differential distortion on demodulated composite television signals, comprising the steps of: broadcasting a test signal at predetermined intervals, the test signal including a component at at least one average video signal level; receiving the test signal at a receiver, the receiver being adapted to carry out the steps of: measuring the distortion of the video signal at the said at least one average video signal level; deriving the required correction at that signal level; and applying the said derived required correction to subsequently received broadcast video signals at that signal level.
The present invention also provides a test signal for use in the above method, comprising one line of a composite television signal having an identifying portion to identify it as a test signal and having high frequency components at at least three average video signal levels.
The test signal may be transmitted once per frame or over a longer period with successive test signals being spaced by several seconds.
The method of the present invention may include the step of measuring the amplitude and phase distortion for a range of average video signal levels of the test signal and deriving a correction to be applied to subsequently received broadcast signals for each such distortion at each of the measured average video signal levels. Thus, if the levels of demodulated chrominance are significantly reduced at high average signal levels (i.e. close to peak white) by distortion of the signal during modulation, transmission and demodulation, the effect of these distortions may be corrected by increasing the chrominance gain when the signal level is high. These corrections are preferably applied to the signal in its composite form to allow the level of high frequency luminance (picture detail) to be corrected also. The correction may be derived and applied at a number of different frequencies to improve the accuracy of the luminance correction.
The derived corrections may be interpolated or extrapolated to derive the correction to be applied at average video signal levels other than the signal levels of the test signal components. Preferably, the corrections are applied to subsequently received broadcast signals at closely spaces signal levels to give a smoothly varying correction which adds no visible distortions to the broadcast signal.
Also in accordance with the present invention there is provided a receiver adapted to receive and demodulate a composite television signal, including: a test signal detector operable to detect a test signal broadcast at predetermined intervals; measurement apparatus adapted to determine the level of differential amplitude and/or phase distortion of the received test signal at at least one average video signal level and to derive the correction required to reduce the distortion at that signal level or levels; storage means connected to receive the derived required correction or corrections; and signal processing apparatus adapted to apply the required correction or corrections to subsequently received television signals at the average video signal level or levels for which the correction or corrections was derived.
The receiver operates to derive and apply corrections in the way described above. The apparatus may be implemented in analogue or digital circuitry or, where the receiver includes a high speed computer, certain of the apparatus operations may be implemented in software.
The present invention provides a broadcast system, including a transmitter configured to modulate and transmit a composite television signal including the test signal, and at least one receiver of the type described above. In such a broadcast system differential distortion of the broadcast signals may be corrected more accurately than by the average correction methods currently known and used.
Brief Description of Drawings:
One particular preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a general schematic diagram of the correction derivation and application stages of the receiver of the present invention;
Figure 2 shows two suitable forms of the test signal of the present invention; and
Figure 3 is a schematic diagram showing the receiver stages of Figure 1 implemented in digital circuitry.
Modes for Carrying Out the Invention:
Referring initially to Figure 2, two suitable forms of test signals according to the present invention are shown. Both signals, employed to correct chrominance errors, are in the form of a broadcast line signal including high frequency components which may be measured at at least three different average video signal levels. The first signal 10A shown in Figure 2A, is in the form of a television line ramp and the second 10B, in Figure 2B, is in the form of a television line staircase. Both signals shown are augmented by a subcarrier.
Signals of this type are easy to detect, being identified by a preceding chrominance burst 12 of at least 20 microseconds duration.
The circuitry measuring the test signal distortion and deriving the corrections required to minimise its effect includes storage for the corrections to allow them to be applied to successive received television broadcast signals. It is therefore the case that the test signal, which sets up the stored corrections, need be transmitted only sufficiently often to ensure that there is no appreciable delay in obtaining a good picture after the viewer has changed channel or after a change in received signal quality as a result of changes to the signal path for distribution, transmission or reception. Accordingly, whilst the test signal may be transmitted once per frame, lower repetition frequencies such as once per second or once per ten seconds may be used.
The receiver circuitry which derives and applies the required correction of amplitude and phase distortion affecting one signal frequency (colour subcarrier) at different average video signal levels is shown in Figure 1.
The television broadcast signal, including at periodic intervals the test signal, is received and demodulated by the receivers vision demodulator 20. The demodulated signal 22 is applied to measurement apparatus 24 which measures the difference between the chrominance level of the received (distorted) signal and an expected chrominance level for the transmitted test signal and derives a correction which will minimise the effect of the distortion. The derived corrections 26 are then stored in a memory 28 at address locations 30 determined by the average luminance level of the demodulated signal 22. The average luminance level, and hence the memory address locations 30, are derived by passing the demodulated signal 22 through a suitable low-pass filter arrangement 32.
To ensure that only corrections derived from a received test signal are stored in the memory 28, a test signal detector 34 is provided. When a test signal is received, identified as such by the preceding 20 us chrominance burst 12 (Figure 2), the detector 34 generates a write-enable signal 36 which allows derived corrections to be written into the memory 28 for the duration of the test signal.
The stored corrections are applied to subsequently received television broadcast signals by a controllable equaliser 38. Control of the equaliser 38 may be achieved by a number of established methods.
The stored corrections are passed through an interpolator 40 prior to application by the equaliser 38. The interpolator 40 derives further required corrections to be applied at average video signal levels other than those for which the measurement apparatus 24 measured the distortion of the test signal. Use of the interpolator 40 allows the corrections to be applied at closely spaced average video signal levels to provide a smoothly varying correction which adds no visible additional distortions to the video signal.
A more detailed implementation of the receiver circuitry is shown in Figure 3. In the circuitry shown, the distortion is measured and the corrections derived from the test signal of Figure 2A (the television line ramp). The output from the receivers vision demodulator 20 is digitised by an analogue to digital converter 42: this allows the subsequent measurement and correction stages to be defined in terms of known digital operations although it will be appreciated that some of these stages could be implemented in analogue circuitry.
The digitised output from the analogue to digital converter 42 is applied to a chrominance demodulator 44. The chrominance demodulator 44, which could be the normal receiver demodulator, is shown in Figure 3 as a separate demodulator for the sake of clarity.
The demodulated chrominance components U,V are applied to the measurement apparatus 24. The amplitude of the demodulated signal is calculated, in a PROM (programmable read-only memory) 24A, as the root of the sura of the squares of the two demodulated colour components U,V. The phase of the demodulated signal is also calculated in a PROM 24P as the inverse tan ratio of the two demodulated colour components U,V. These two measurements 26A, 26P which define the corrections to be applied to a subsequently received broadcast signal are then stored in amplitude and phase correction memories 28A, 28P respectively.
As described previously, the corrections are stored at memory address locations 30 derived from the average luminance level of the demodulated signal by a low pass filter 32. As also described, these corrections may only be stored when a write-enable signal 36 from a test signal detector 34 indicates the presence of a test signal.
Following interpolation by respective amplitude and phase interpolators 40A, 40P the corrections are applied to a controllable equaliser 38. The equaliser 38 is an adjustable transversal equaliser having a signal input 50 for the demodulated broadcast video signal and separate symmetric 52 and anti-symmetric 54 control inputs. The amplitude correction signal is applied to the symmetric control input 52: amplitude correction is achieved by varying the size of the signal coefficients symmetrically about the centre of the filter. The phase correction signal is applied to the anti-symmetric control input 54: phase correction is achieved by varying the size of the signal coefficients anti-symmetrically about the centre of the filter.
In order to reduce the sensitivity of the circuitry to disturbances which may affect the received test signal, averaging circuits (not shown) may be provided around the correction memories 28A, 28P. Such averaging circuits may average successive test signals prior to measurement of distortion or may average successively derived corrections for a given average video signal level.
It is envisaged that new designs of broadcast receiver, which include means for improving the quality of the received television signal, will include a wide range of sophisticated circuits. The present invention provides such means for improving the quality without requiring a significant increase in receiver circuitry.
It will be appreciated that, where the receiver apparatus includes high-speed computing capability, the method of the present invention may be implemented in software. In such a case, the schematic diagrams of figures 1 and 3 may be regarded as flow charts representing the steps of a software decoding and correction process.
The decoding and correction circuitry of the present invention may also include means for correcting static losses within the receiver to compensate for multipath effects, receiver and/or transmitter responses and the low frequency effects of mistuning.

Claims

1. A method for reducing the effect of differential distortion on demodulated composite television signals, comprising the steps of: broadcasting a test signal at predetermined intervals, the test signal including a component at at least one average video signal level; receiving the test signal at a receiver, the receiver being adapted to carry out the steps of: measuring the distortion of the video signal at the said at least one average video signal level; deriving the required correction at that signal level; and applying the said derived required correction to subsequently received broadcast video signals at that signal level.
2. A method according to claim 1, in which the test signal includes components at at least three average video signal levels and in which a required correction is derived for each such level.
3. A method according to claim 2, in which measured values for distortion of the test signal are interpolated or extrapolated to derive the required correction at signal levels other than the average video signal levels of the measured test signal components.
4. A method according to claim 1, in which the required correction derived and applied includes correction of phase and amplitude distortions present in the demodulated television signal.
5. A method according to claim 1, in which the required correction is derived and applied at a number of different frequencies.
6. A method according to claim 1, in which successive test signals are stored and averaged with the preceding test signal and the required correction is derived from the measured distortion of the averaged test signal.
7. A method according to claim 1, in which successive derived corrections for a given average video signal level are averaged and the correction subsequently applied to broadcast video signals is the averaged correction for that average video signal level.
8. A method according to claim 1, in which the or each required correction is applied to the video signal in its composite form.
9. A method according to claim 2, in which the average video signal levels at which required corrections are applied are closely spaced such that no visible additional distortions are added to the signal.
10. A test signal for use in a method according to claim 1, comprising one line of a composite television signal having an identifying portion to identify it as a test signal and having high frequency components at at least three average video signal levels.
11. A test signal according to claim 10, including a chrominance burst preceding the said high frequency components thereof.
12. A test signal according to claim 11, in which the chrominance burst has a duration of at least 20 microseconds.
13. A composite television signal including, at predetermined intervals, a test signal according to claim 10.
14. A receiver adapted to receive and demodulate a composite television signal, including: a test signal detector operable to detect a test signal broadcast at predetermined intervals; measurement apparatus adapted to determine the level of differential amplitude and/or phase distortion of the received test signal at at least one average video signal level and to derive the correction required to reduce the distortion at that signal level or levels; storage means connected to receive the derived required correction or corrections; and signal processing apparatus adapted to apply the required correction or corrections to subsequently received television signals at the average video signal level or levels for which the correction or corrections was derived.
15. Apparatus according to claim 14, in which the signal processing apparatus includes an interpolator configured to derive the required correction for average video signal levels other than the at least one average video signal level at which the distortion is determined by the measurement apparatus, the derived required corrections being applied to subsequently received television signals by the signal processing apparatus.
16. Apparatus according to claim 14, in which the measurement apparatus is adapted to determine the level of distortion of the received test signal at at least three average video signal levels and to determine a required correction for each such signal level.
17. Apparatus according to claim 14, including an analogue to digital converter through which the received test signal is passed, in which the measurement apparatus and storage means are implemented in digital circuitry.
18. Apparatus according to claim 17, in which the measurement apparatus comprises a programmable read-only memory device.
19. Apparatus according to claim 17, in which the storage means comprises a memory device in which the derived required correction or corrections are stored at address locations determined by the average luminance level of the received test signal .
20. Apparatus according to claim 19, including at least one filter through which the analogue test signal is passed to derive the luminance level thereof.
21. Apparatus according to claim 14, including further storage means adapted to store a received test signal, to compare a subsequently received test signal with the stored test signal and to derive an average test signal therefrom, the measurement apparatus being adapted to determine the level of distortion of the average test signal.
22. Apparatus according to claim 14, including additional storage means adapted to compare a subsequently derived correction for a given average video signal level with a stored derived correction for that average video signal level, the signal processing apparatus being adapted to apply the averaged derived correction to subsequently received television signals.
23. A receiver adapted to receive and demodulate a composite television signal, including high speed computer circuitry programmed to effect correction of the effects of differential distortion on a demodulated composite television signal in accordance with the method of claim 1.
24. A composite television broadcast transmitter including means for modulating and transmitting a composite television signal according to claim 13.
25. A composite television broadcasting system comprising a transmitter according to claim 24 and at least one receiver according to claim 14.
EP92917600A 1991-08-21 1992-08-20 Decoding of composite television signals Withdrawn EP0558704A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9118057 1991-08-21
GB9118057A GB2258969A (en) 1991-08-21 1991-08-21 Decoding of composite television signals

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CN (1) CN1074073A (en)
AU (1) AU2440292A (en)
BG (1) BG97648A (en)
BR (1) BR9205328A (en)
CA (1) CA2094381A1 (en)
CZ (1) CZ61693A3 (en)
FI (1) FI931798A0 (en)
GB (1) GB2258969A (en)
HU (1) HUT64668A (en)
NO (1) NO931440D0 (en)
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Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2429868B (en) * 2005-09-03 2010-11-10 Amulet Electronics Ltd Video display system
JP4968146B2 (en) * 2008-03-31 2012-07-04 ソニー株式会社 Broadcast signal receiver, reception control method thereof, and IC

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1050574B (en) * 1975-07-01 1981-03-20 Indesit IMPROVEMENTS OF COLOR TELEVISION SYSTEMS
US4237486A (en) * 1978-11-09 1980-12-02 Comsonics, Inc. Compatible transmission of an encoded signal with a television
SU1184108A1 (en) * 1981-11-11 1985-10-07 Nikolaj M Eremin Meter of parameters of television signal
GB2176669A (en) * 1985-06-05 1986-12-31 Philips Electronic Associated Digitising television signals
US4825379A (en) * 1986-08-29 1989-04-25 Tektronix, Inc. Method and apparatus for processing waveform records for jitter elimination prior to averaging in determining signal to noise ratio
DE3883673T2 (en) * 1987-09-25 1994-03-03 Japan Broadcasting Corp Decoding equalizer.
US5136368A (en) * 1991-01-24 1992-08-04 The Grass Valley Group, Inc. Television signal decoder with improved architecture

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9304563A1 *

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JPH06501832A (en) 1994-02-24
FI931798A (en) 1993-04-21
BG97648A (en) 1994-03-31
GB9118057D0 (en) 1991-10-09
BR9205328A (en) 1994-06-21
FI931798A0 (en) 1993-04-21
NO931440L (en) 1993-04-20
HU9300945D0 (en) 1993-06-28
CA2094381A1 (en) 1993-02-22
NO931440D0 (en) 1993-04-20
WO1993004563A1 (en) 1993-03-04
CZ61693A3 (en) 1993-11-17
SK34293A3 (en) 1993-07-07
HUT64668A (en) 1994-01-28
AU2440292A (en) 1993-03-16
GB2258969A (en) 1993-02-24
CN1074073A (en) 1993-07-07

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