GB1604053A - Television systems - Google Patents

Television systems Download PDF

Info

Publication number
GB1604053A
GB1604053A GB5038177A GB5038177A GB1604053A GB 1604053 A GB1604053 A GB 1604053A GB 5038177 A GB5038177 A GB 5038177A GB 5038177 A GB5038177 A GB 5038177A GB 1604053 A GB1604053 A GB 1604053A
Authority
GB
United Kingdom
Prior art keywords
signal
frame
video
signals
counter
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.)
Expired
Application number
GB5038177A
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.)
REDIFFUSION HONGKONG Ltd
Original Assignee
REDIFFUSION HONGKONG Ltd
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 REDIFFUSION HONGKONG Ltd filed Critical REDIFFUSION HONGKONG Ltd
Priority to GB5038177A priority Critical patent/GB1604053A/en
Priority to DE19782851906 priority patent/DE2851906A1/en
Publication of GB1604053A publication Critical patent/GB1604053A/en
Priority to HK23582A priority patent/HK23582A/en
Priority to MY190/83A priority patent/MY8300190A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00Television systems
    • H04N7/08Systems 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
    • H04N7/0806Systems 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 the signals being two or more video signals

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Synchronizing For Television (AREA)
  • Television Systems (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO TELEVISION SYSTEMS (71) We, REDIFFUSION (HONG KONG) LIMITED, a Company incorporated under the Laws of Hong Kong, of Rediffusion House, 77-79 Gloucester Road, Hong Kong, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates generally to the field of television and is particularly concerned with the distribution of a number of video signals over a single transmission link, such as a coaxial cable.
In accordance with a first aspect of the present invention, there is provided a method for distributing the outputs of a plurality of video signal sources over a single transmission link, in which the plurality of video signal sources are synchronised with one another, the output signals of the video sources including synchronisation signals are sequentially sampled frame by frame in a cycle order to provide a combined output on a common output, a reference frame signal is applied to the common output between consecutive cycles, whereby a frame sampled from any one video source is transmitted in a respective predetermined position relative to the reference frame signal in the cycle, the synchronisation signals are removed from the video signals appearing at the common output and replaced by new synchronisation signals, the resultant signals are distributed over the transmission link to a receiver, the received synchronisation pulses are counted, the count being reset by the reference frame signal, and a desired frame is selected for display by sampling the received signal when the count of the synchronisation pulses corresponds to the position of the desired frame relative to the reference frame signal.
In accordance with a second aspect of the present invention, there is provided a television transmitting system comprising a plurality of synchronised video sources, means for generating a reference frame signal, a sampling circuit for sequentially sampling the outputs of the video sources and the output of the means for generating the reference frame signal in a cyclic order, whereby a combined output signal is generated which is applied to a common output and which comprises a plurality of cycles each consisting of a reference frame signal and one frame from each of the sources in a predetermined order, and a circuit connected to the common output for removing the synchronisation signals from the video signals appearing at the common output and for replacing the removed signals with new synchronisation signals.
Preferably, the reference frame signal includes for at least part of its duration a continuous wave component.
Conveniently, the sampling circuit comprises a counter and a plurality of electronic switches controlled by the counter, each electronic switch connecting the output of one of the video signal sources to a common output.
Preferably, the counter is connected to a reset circuit controlled by a circuit for detecting the presence of the reference frame signal on the common output, whereby the counter is reset by the reference frame signal to commence a new cycle of sampling.
A receiver may also be provided comprising a frame snatch system which includes means for detecting the reference frame signal in the incoming signal, a channel selector for selecting the number of a channel corresponding to one of the video signals which it is desired to display, a counter for counting frames following each reference frame, a storage circuit controlled by the said counter for storing the frame selected by the channel selector, and a video monitor for reproducing the stored frame. Particularly frames are identified as the Nth frame after the reference frame, N being any positive integral number.
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing which is a schematic block diagram of a television system in accordance with the invention.
To the left of a dotted line 10 in the drawing, there is shown a transmission system, a receiver being shown to the right of the line 10.
In the transmission system, there are provided 80 cameras designated CAM I to CAM 80 respectively. All the cameras are connected to a common sync generator 12 so that the vertical and horizontal scanning in all the cameras is synchronized. The sync generator 12 is also connected to a reference frame generator 14 which generates a 1 MHz continuous wave.
The sync generator 12 is further connected to a pulse counter 18 which counts sync pulses. The pulse counter may comprise a 50 Hz oscillator locked onto the sync generator signal and a binary coded decimal (BCD) counter connected to the oscillator. The counter counts frames one by one and cyclically applies a sampling signal onto one of 81 lines each controlling a respective one of 81 electronic switches designated CH. 0 to CH. 80. The 81st line is connected to the switch CH. 0. The electronic switch CH. 0 is connected to the reference frame generator 14 and each of the other is connected to a respective one of the cameras CAM 1 to CAM 80. The outputs of all the electronic switches are connected to a common video line 16 on which there appears a signal which comprises cycles each having 81 frames of which the last frame is a reference frame consisting exclusively of a 1 MHz wave riding on the syncs and the eighty preceding frames are the respective video output signals of the cameras.
When the pulse counter reaches the count "8", the reset frame signal from generator 14 is applied to line 16 and detected by a reset signal detector 20. This detector controls a clearing signal generator 22 to reset the counter 18 to"00".
A video processing amplifier 24 is provided which serves to remove the sync pulses obtained from the respective cameras and to replace these by clean sync signals derived directly from the sync generator 12. The provision of this circuit 24 ensures that in the event of failure of one of the cameras the counting sequence for the remaining cameras is not disrupted and only the frame of the failed camera is lost.
The output signal of the.synchronization signal regenerating circuit is applied to a carrier frequency modulator 26.
In the receiver, the video signal is applied to a signal frequency board 28 which derives the received carrier frequency signal and produces a video signal and a frame sync signal. The video signal is applied to a memory unit 30 and also to a detector 32 for detecting the 1 MHz reference frequency and the frame sync signal is applied directly to a frame pulse counter 34. The frame pulse counter 34 is reset by the signal from the detector 32 of the reference frequency and counts frame synchronization signals to allow a frame from a desired camera to be selected. The selection is effected by means of a channel selector 36 which is connected to a digital display 38 by means of which the number of a desired channel may be selected manually. The channel selector 36 includes a keyboard connected to a binary coded generator which in turn applies a signal to the frame pulse counter 34. When the frame in the field pulse counter corresponds to the desired frame as set on the manual keyboard, a record command signal is applied by the frame pulse counter to the memory unit which may, for example, consist of a magnetic disc. The memory unit then snatches the video frame, that is to say the one frame is recorded on the memory unit and is continuously played on a video monitor 40.
Whilst the described system enables a plurality of channels to be transmitted on a single transmission link it will be appreciated that the updating frequency of each channel is reduced in proportion to the number of channels combined on the same link. The system can, however, enable, for example, 500 channels or frames of information to be transmitted sequentially provided an updating delay of once in every 10.02 seconds is acceptable.
WHAT WE CLAIM IS: 1. A method for distributing the outputs of a plurality of video signal sources over a single transmission link, in which the plurality of video signal sources are synchronised with one another, the output signals of the video sources including synchronisation signals are sequentially sampled frame by frame in a cyclic order to provide a combined output on a common output, a reference frame signal is applied to the common output between consecutive cycles, whereby a frame sampled from any one video source is transmitted in a respective predetermined position relative to the reference frame signal in the cycle, the synchronisation signals are removed from the video signals appearing at the common output and replaced by new synchronisation signals, the resultant signals are distributed over the transmission link to a receiver, the received synchronisation pulses are counted, the count being reset by the reference frame signal, and a desired frame is selected for display by sampling the received
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. the reference frame, N being any positive integral number. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing which is a schematic block diagram of a television system in accordance with the invention. To the left of a dotted line 10 in the drawing, there is shown a transmission system, a receiver being shown to the right of the line 10. In the transmission system, there are provided 80 cameras designated CAM I to CAM 80 respectively. All the cameras are connected to a common sync generator 12 so that the vertical and horizontal scanning in all the cameras is synchronized. The sync generator 12 is also connected to a reference frame generator 14 which generates a 1 MHz continuous wave. The sync generator 12 is further connected to a pulse counter 18 which counts sync pulses. The pulse counter may comprise a 50 Hz oscillator locked onto the sync generator signal and a binary coded decimal (BCD) counter connected to the oscillator. The counter counts frames one by one and cyclically applies a sampling signal onto one of 81 lines each controlling a respective one of 81 electronic switches designated CH. 0 to CH. 80. The 81st line is connected to the switch CH. 0. The electronic switch CH. 0 is connected to the reference frame generator 14 and each of the other is connected to a respective one of the cameras CAM 1 to CAM 80. The outputs of all the electronic switches are connected to a common video line 16 on which there appears a signal which comprises cycles each having 81 frames of which the last frame is a reference frame consisting exclusively of a 1 MHz wave riding on the syncs and the eighty preceding frames are the respective video output signals of the cameras. When the pulse counter reaches the count "8", the reset frame signal from generator 14 is applied to line 16 and detected by a reset signal detector 20. This detector controls a clearing signal generator 22 to reset the counter 18 to"00". A video processing amplifier 24 is provided which serves to remove the sync pulses obtained from the respective cameras and to replace these by clean sync signals derived directly from the sync generator 12. The provision of this circuit 24 ensures that in the event of failure of one of the cameras the counting sequence for the remaining cameras is not disrupted and only the frame of the failed camera is lost. The output signal of the.synchronization signal regenerating circuit is applied to a carrier frequency modulator 26. In the receiver, the video signal is applied to a signal frequency board 28 which derives the received carrier frequency signal and produces a video signal and a frame sync signal. The video signal is applied to a memory unit 30 and also to a detector 32 for detecting the 1 MHz reference frequency and the frame sync signal is applied directly to a frame pulse counter 34. The frame pulse counter 34 is reset by the signal from the detector 32 of the reference frequency and counts frame synchronization signals to allow a frame from a desired camera to be selected. The selection is effected by means of a channel selector 36 which is connected to a digital display 38 by means of which the number of a desired channel may be selected manually. The channel selector 36 includes a keyboard connected to a binary coded generator which in turn applies a signal to the frame pulse counter 34. When the frame in the field pulse counter corresponds to the desired frame as set on the manual keyboard, a record command signal is applied by the frame pulse counter to the memory unit which may, for example, consist of a magnetic disc. The memory unit then snatches the video frame, that is to say the one frame is recorded on the memory unit and is continuously played on a video monitor 40. Whilst the described system enables a plurality of channels to be transmitted on a single transmission link it will be appreciated that the updating frequency of each channel is reduced in proportion to the number of channels combined on the same link. The system can, however, enable, for example, 500 channels or frames of information to be transmitted sequentially provided an updating delay of once in every 10.02 seconds is acceptable. WHAT WE CLAIM IS:
1. A method for distributing the outputs of a plurality of video signal sources over a single transmission link, in which the plurality of video signal sources are synchronised with one another, the output signals of the video sources including synchronisation signals are sequentially sampled frame by frame in a cyclic order to provide a combined output on a common output, a reference frame signal is applied to the common output between consecutive cycles, whereby a frame sampled from any one video source is transmitted in a respective predetermined position relative to the reference frame signal in the cycle, the synchronisation signals are removed from the video signals appearing at the common output and replaced by new synchronisation signals, the resultant signals are distributed over the transmission link to a receiver, the received synchronisation pulses are counted, the count being reset by the reference frame signal, and a desired frame is selected for display by sampling the received
signal when the count of the synchronisation pulses corresponds to the position of the desired frame relative to the reference frame signal.
2. A television transmitting system comprising a plurality of synchronised video sources, means for generating a reference frame signal, a sampling circuit for sequentially sampling the outputs of the video sources and the output of the means for generating the reference frame signal in a cyclic order, whereby a combined output signal is generated which is applied to a common output and which comprises a plurality of cycles each consisting of a reference frame signal and one frame from each of the sources in a predetermined order, and a circuit connected to the common output for removing the synchronisation signals from the video signals appearing at the common output and for replacing the removed signals with new synchronisation signals.
3. A television transmitting system according to claim 2, wherein the means for generating a reference frame signal provides an output which includes for at least part of its duration a continuous wave component.
4. A television transmitting system according to claim 2 or 3, wherein the sampling circuit comprises a counter and a plurality of electronic switches controlled by the counter, each electronic switch connecting the outut of one of the video signal sources to the common output.
5. A television transmitting system according to claim 4, wherein the counter is connected to a reset circuit controlled by a circuit for detecting the presence of the reference frame signal on the common output, whereby the counter is reset by the reference frame signal to commence a new cycle of sampling.
6. A television transmitting system according to any one of claims 2 to 5, wherein the new synchronisation signals are derived directly from a synchronisation pulse generator the output of which synchronises the outputs of the video signal sources.
7. A television transmitting system according to any one of claims 2 to 6, comprising a receiver having a frame snatch system which includes means for detecting the reference frame signal in the incoming signal, a channel selector for selecting the number of a channel corresponding to one of the video signals which it is desired to display, a counter for counting frames following each reference frame, a storage circuit controlled by the said counter for storing the frame selected by the channel selector, and a video monitor for reproducing the stored frame.
8. A method for distributing the outputs of a plurality of video signal sources over a single transmission link substantially as hereinbefore described with reference to the accompanying drawing.
9. A television transmitting system substantially as hereinbefore described with reference to the accompanying drawing.
GB5038177A 1977-12-02 1977-12-02 Television systems Expired GB1604053A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB5038177A GB1604053A (en) 1977-12-02 1977-12-02 Television systems
DE19782851906 DE2851906A1 (en) 1977-12-02 1978-11-30 METHOD OF TRANSMISSION OF MULTIPLE TELEVISION SIGNALS, TELEVISION TRANSMISSION SYSTEM AND TELEVISION RECEIVER
HK23582A HK23582A (en) 1977-12-02 1982-06-03 Improvements in or relating to television systems
MY190/83A MY8300190A (en) 1977-12-02 1983-12-30 Improvements in or relating to television systems

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB5038177A GB1604053A (en) 1977-12-02 1977-12-02 Television systems

Publications (1)

Publication Number Publication Date
GB1604053A true GB1604053A (en) 1981-12-02

Family

ID=10455707

Family Applications (1)

Application Number Title Priority Date Filing Date
GB5038177A Expired GB1604053A (en) 1977-12-02 1977-12-02 Television systems

Country Status (4)

Country Link
DE (1) DE2851906A1 (en)
GB (1) GB1604053A (en)
HK (1) HK23582A (en)
MY (1) MY8300190A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2148069A (en) * 1983-10-14 1985-05-22 Marconi Avionics Video processing circuit
GB2238926A (en) * 1989-12-07 1991-06-12 Secretary Of The State For Def Video multiplexer for surveillance installation

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE16548T1 (en) * 1982-04-29 1985-11-15 Deltavisie Bv SYSTEM FOR TRANSMISSION OF PROGRAM OR DATA SIGNALS.
DE3736374A1 (en) * 1987-10-27 1990-05-10 Peter Pannier Method for transmitting and receiving multiple image signals at a sequential field rate

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2148069A (en) * 1983-10-14 1985-05-22 Marconi Avionics Video processing circuit
GB2238926A (en) * 1989-12-07 1991-06-12 Secretary Of The State For Def Video multiplexer for surveillance installation

Also Published As

Publication number Publication date
DE2851906A1 (en) 1979-06-13
MY8300190A (en) 1983-12-31
HK23582A (en) 1982-06-11

Similar Documents

Publication Publication Date Title
EP0127383B1 (en) Video signal scrambling and descrambling systems
EP0386928B1 (en) Timing audio and visual signals with coincidental markers
US4527195A (en) Apparatus for encoding and decoding information
US4319273A (en) Television signal with encoded synchronizing signals
KR940017735A (en) Ghost Canceling Reference Signal Acquisition Circuit Used in TV Receivers or Video Recorders
GB1147603A (en) Improvements in or relating to television transmission systems
US4245246A (en) Pay TV system
CA1150818A (en) Subscription television coding system
GB1147604A (en) Improvements in or relating to television transmission systems
ATE112917T1 (en) TELEVISION SIGNAL MONITOR.
US4232339A (en) Television signal horizontal interval timing reconstruction system
GB1604053A (en) Television systems
US3067280A (en) Secret signaling
US6947069B1 (en) Method and apparatus for connecting fiber optic lines to an information transmission line carrying two way signals
US5530756A (en) Television scrambling and descrambling method, and transmitter and receiver using said method
GB1163016A (en) Improvements in and relating to Television Systems
US3001011A (en) Subscription television system
US2563448A (en) Subscription type signaling system
US3420951A (en) Television transmission delay compensation apparatus
ATE57289T1 (en) SYNCHRONIZATION SIGNAL REMOVAL DEVICE FOR COMPONENT TELEVISION VIDEO SIGNAL RECEPTION.
US2929865A (en) Secrecy communication system
GB2200011A (en) Television sync extraction circuit
US2656405A (en) Air key subscriber television system
RU2046546C1 (en) Method for scrambling of tv-signal and device for implementation of said method
US2809231A (en) Subscriber television system

Legal Events

Date Code Title Description
PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee