GB2343810A - Composite image processing device and method - Google Patents

Abstract

A signal processing means for generating a composite image wherein the signal from a tuner (14) may be switched between a display (20) and a mixer (40), thereby preventing the internal transfer of broadcast derived video signals within the receiver with direct tuner signals. Said mixer (40) receives the signal from the tuner and from a second means (44, 48), combines said signals and conveys them to a TV receiver video input (22) forming a composite image. The mixer may also alter the background image brightness, contrast and other parameters to permit easier viewing of images or messages. The second means may comprise a camera (CCTV), a baby monitor, a computer system, or a VCR.

Description

Title: Video signal processing device and method Field of invention This invention concerns video signal processing devices and methods which enable a second video signal to be mixed with a first signal for display in a television display, and to a method of mixing a first video signal with a second video signal for display on a television set.

Background to the invention Video signal mixing devices are known by which two video signals can be mixed and merged either by switching as between one and the other so that one signal occupies one part of a screen and the other signal another part of the screen, or by superimposition of one signal over the other so that one picture is superimposed in the display over what would have been displayed from the original signal.

A difficulty arises if the television set which is to be used to display the output signal is also to be used as the tuner for receiving and decoding incoming television signals and to provide a video signal as one of the inputs to the mixer. Most modern receivers include a Video-in socket to allow the output of a video recorder to be conveyed to the video circuits within the television set for the purpose of displaying the output of the video recorder on the television. When recording an incoming broadcast television signal, the television set may be set to display the same signal, or another signal, but it is not normal to supply the output from the video recorder to the television receiver in parallel with the incoming video signal which is being recorded.

Arrangements have been proposed in recent years for switching between an incoming broadcast derived signal and a closed circuit television camera (typically associated with a security system, or an entryphone system) to allow a signal from the camera to be displayed on the receiver screen n place of the e incoming broadcast signal. Typically this has been achieved using the normal handheld control linked to the television set.

But it is not appropriate or desirable to continually display the signal from the CCTV camera, which would obviously interfere with the normal viewing of broadcast television pictures. The ability to replace the broadcast signal with that from a CCTV camera is merely incidental to the main use of the television set, and will normally be under the control of the viewer, so that their enjoyment of the incoming broadcast is not interfered with, except when a sensor indicates an intruder may be in the field of view of the camera, or when a doorbell is rung.

It is an object of the present invention to provide a device which will enable a second video signal to be superimposed over a first video signal or be displayed in a discrete region of a screen in place of or substantially in place of the first video signal.

It is another object of the invention to provide a device as aforesaid which can be adapted to display in combination with a first video signal typically obtained from an incoming broadcast signal, characters forming words and/or devices and/or pictures for conveying a message to the viewer either by superimposition over, or substitution for part of, the incoming broadcast signal.

Summarv of the invention According to one aspect of the present invention there is provided first circuit means adapted to obtair. from a broadcast television receiver a video signal which would normally be supplied to a video recorder for recording purposes, second circuit means adapted to receive the first and second signals for mixing one with the other, third circuit means for determining the nature of the mixing to occur, fourth circuit means for conveying a combined signal produced by the mixing of the two signals to a video signal input of the broadcast television receiver for display thereon, and fifth circuit means adapted to prevent the internal transfer of broadcast derived video signal within the receiver for display thereon, except via the said first, second and fourth circuit means.

The invention is of particular application to a broadcast television receiver having a so-called SCART socket in which pin 19 comprises a video output terminal from the receiver, pin 20 a video input terminal for receiving a video signal for display by the receiver, and pin 8 constitutes a control pin to which a signal can be applied to switch the television display input from the tuner output to the video input terminal of the SCART socket, namely pin 20 thereof.

The mixing may be controlled in known manner so that one signal may be superimposed over the other in a subsequent display or the two signals may be arranged to be displayed simultaneously in different regions of a television display, or part of one signal may be blanked and the video signal from the second circuit means is synchronously incorporated into the blanked region of the display, As applied to a modern broadcast television receiver therefore, the fifth circuit means previously referred to comprises a circuit adapted to provide an appropriate control signal (typically +12 volts) to pin 8 of a SCART socket, whenever a device comprising the said first to fourth circuit means is connected to the SCART socket, so that signals from the tuner section of the broadcast receiver are routed to the input of the video signal amplifier circuits from pin 19 via the said first, second and fourth circuits, and pin 20 of the SCART socket.

The video signal obtained from the broadcast receiver may be derived from a live broadcast signal, or from a camera, a VCR, or any other video source adapted to provide a modulated VHF signal suitable for decoding by a receiver tuner.

The second video signal to be mixed with the broadcast derived signal may be a signal from a television camera, or from a video recorder or video player such as a disc player, or from a memory device in which signals have been stored for retrieval in a synchronous manner when required, which when retrieved generate a video signal representative of graphics or letters or numerals, which can be mixed with the said first signal in any of the ways previously described for display therewith.

In particular the memory device may contain signals which when read out, generate a video input corresponding to characters such as letters of the alphabet or numerals to allow a message to be displayed in combination with the original broadcast signal, on the receiver screen, either as a superimposition over the original video signal or a superimposition over apart of the original video signal or in an area of the screen in which the message signal is substituted for the broadcast signal.

According to a preferred feature of the invention, if the message signal is to be displayed superimposed over part or all of the display of the incoming broadcast signal, one of the circuit means is preferably adapted to reduce the brightness or contrast or chrominance or other parameters of the signal derived from the broadcast signal, so that the display of the broadcast signal appears less bright than normal, either over the whole of the display or over that part of the display in which the message is to be displayed, so as to allow the characters forming the message to be seen more clearly. To this end the signal generating the characters forming the message is preferably one which generates a generally black background on which the letters or numerals appear in a colour such as white or yellow.

It is to be understood that the above-mentioned technique of reducing a brightness parameter of the broadcast signal in which it becomes more of a background, so that the second signal can be more readily distinguished, may be applied to situations where the video signal in the second channel (to be mixed with the broadcast derived signal) is derived from any video signal source and not necessarily a message generating signal source. Thus the technique is not limited to static message display but may also be used when camera generated video or recorded video is supplied via the second circuit means for mixing with the broadcast derived signals.

The invention also provides a method of introducing a second video signal into a first video signal for display in synchronism with the first, either superimposed over or in substitution for part of the first signal, comprising the steps of inhibiting the internal transmission of video signal from a television tuner section of a broadcast television receiver to a video signal amplifying circuit which supplies signals to generate a picture on the display device of the receiver, conveying the video signal from the tuner section to a first input of a mixing device, conveying a second video signal to a second input of the mixing device, synchronously mixing the two signals therein and conveying the output signal from the mixer as an input signal to the video signal amplifying circuits of the receiver in place of signal derived from the tuner section of the receiver.

The above method differs from the manner in which a broadcast receiver is normally interfaced with a video recorder or other device via the SCART socket provided thereon, in that the video signal amplifying circuit of the receiver is either supplied with recorded video signals from a video recorder or signals derived from the tuner section of the receiver. There is no provision for mixing signals already recorded by the video recorder with the incoming video signal from the tuner section of the broadcast receiver, for display on the receiver. Once the signal path within the broadcast receiver has been interrupted or inhibited by the application of the appropriate control voltage on pin 8 of the SCART socket, any transfer of the video signal derived from the incoming broadcast signal, can only be supplied to the video amplifier by providing a signal path therefor through the video recorder in place of the inhibited path within the receiver. In that mode there is no provision for the video recorder to provide any video signal for mixing with the video signal derived from a broadcast signal by the tuner.

In a preferred method of the invention, the video signal which is to be mixed with the broadcast derived signal, may be derived from a memory device such as a digital memory, such as is associated with a microprocessor in a computer, and the memory is read at high speed in synchronism with the broadcast derived signal so as to generate a sequence of signals which when displayed will comprise a graphical display over or in place of the picture generated by the broadcast derived signal.

This is of particular value where the signal which is to be merged with the incoming broadcast signal is to form a message in the form of characters such as letters or numerals or both, and apparatus for performing this aspect of the method, comprises a processor, a keyboard, a power supply, and supporting electronic circuits such as are contained in a socalled mother board adapted to support the chosen processor and keyboard, a character generator driven by the microprocessor, and circuit means for relaying signals derived by the character generator as an output signal to one input of a mixer for combining with video signals derived from a broadcast signal.

The character generator typically comprises a digital memory in which sequences of digital signals are stored, each sequence being representative of a character.

An optional memory device may be provided in which character defining sequences can be entered using the keyboard, to enable a message to be built up and stored either permanently or semi-permanently.

Where the device is simply to provide a way of introducing a short term message which will not normally have to be replicated, at the same time as receiving an incoming broadcast signal, no long term memory is required and the message can simply be typed in on the keyboard and stored in RAM associated with the processor, and a command given as by one of the keyboard function keys, to cause the microprocessor to display the characters synchronised to the incoming broadcast signal as a repetitive video signal, for supply to the mixer. In this case the memory of the character generator need only comprise a buffer into which digital signals relating to the different characters can be entered and held for read out by the microprocessor and the memory normally provided in a microprocessor chip may itself be sufficient for this purpose.

Alternatively and more preferably, non-volatile memory may be provided into which messages can be stored after having been entered via the keyboard and each message may be given a code name or number or other unique identifier, and a list or index of such messages may be compiled and stored so a user can select one of the stored messages by entering an appropriate command either by the keyboard or via another control device associated with the processor, so that a message can be instantaneously conveyed to the screen of the television set without the need for typing in the message.

The method and apparatus of the invention is not limited to use with a single television set and two or more sets may be connected via appropriate buffering amplifiers, using the SCART socket pins, for operation in parallel.

A device incorporating the invention may be used in conjunction with other interface devices such as a so-called mouse or joystick, together with a more complex character generating device thereby enabling one or more representations to be displayed on a television screen superimposed over or in conjunction with the incoming video signal. In this way for example a game may be played on the screen by moving the displayed representation (s) relative to what is visible on the screen, by manipulating the interface device such as a mouse or joystick.

The broadcast signal need not be a live television broadcast signal, but can be one obtained from a video recording.

In another example the signal from the tuner may be such as to display a list of products available and circuit means is provided for generating an icon in the television display and a mouse or joystick is provided for moving the generated icon around the screen relative to the display in the same way as an icon can be moved around a computer screen using a mouse or the like. By positioning the icon so as to overlie or align with one of the listed objects in the display, a viewer can identify that particular object as being required, by simultaneously pressing a switch such as for example a push button operated switch in the case of a conventional computer mouse, so as to generate a signal indicating that that object has been selected by the viewer. Electronically the object can be tagged by comparing the video signal with the broadcast signal on a time axis during the television frame, with the point in time along the same axis corresponding to the generation of the icon signals. A unique signal can thus be generated indicating that the viewer has selected that object from the list and this information can be stored in a memory typically within the unit. Such information can be transmitted either simultaneously or at a later point in time via a suitable connection to a remote location to enable the viewer's requirements to be met.

Such a system could for example be used for ordering products or services, or could be used in a hospital or nursing home to enable a patient to alert nursing staff to a particular need, or to permit nursing staff to individually address each patient by causing an enquiry message to appear on a television screen viewed by the patient. Using a hand held device interacting with the mixer unit and message memory, or a keyboard, a patient could respond to the question indicating whether or not assistance was required.

In the case of a list of articles or services for sale, the information which can be derived from the memory associated with the unit, can be transmitted to a remote location to indicate that that particular product or service has been selected by the viewer at that unique address, and steps taken to provide the product or service against appropriate payment.

The invention is not limited to the switching of picture signals derived from a receiver tuner but can also be used to switch audio signals in a similar way to the video signals.

By providing an audio channel in a device embodying the invention and an audio channel back from it to the broadcast receiver audio signal amplifying circuits, signals from the tuner can be supplied as an input signal to the audio signal amplifying circuits in the receiver, and the method includes the step of mixing or substituting other audio signals for those derived from the tuner signal for supply to the receiver audio amplifying circuits.

Signals which can be mixed with the tuner derived audio signals may for example comprise an alarm or warning sound to attract attention or simply to indicate that a message is being displayed.

Alternatively a spoken commentary or a translation of a commentary may be provided for substitution for, or overlay over, background sounds such as music derived from the tuner signal so that a combination of sounds will be delivered by the receiver loudspeakers.

Devices are available by which video and audio signals can be encoded onto a carrier so that picture and sound signals from a video camera or from a video recorder in playback mode, can be presented to the aerial input circuit of a broadcast television receiver for decoding and reproduction by the receiver when combined with such a device. The invention thus for example allows a video recording of a broadcast television signal to be made and replayed through a broadcast television receiver using the aerial input socket, and for example a sequence of sub-titles to be synchronously displayed via a mixing unit embodying the invention.

In accordance with the method of the invention, if a mixing unit embodying the invention s connected to the SCART socket of a television receiver, whilst receiving at its aerial a carrier modulated recorded video signal, by suppressing the audio track of the originally recorded video signal, subtitles stored on a second video recording can be displayed, superimposed on or in a lower region of the screen of the television receiver, to allow a person who is hard of hearing to enjoy a television programme which did not include subtitles in the original broadcast.

Thus for example a video signal may be transmitted unimpeded via a mixing unit embodying the invention using the method of the invention, without any substitution or superimposition of video signal content, and a recorded audio track can be superimposed in place of the audio content of the video signal, so that a commentary in one language can be suppressed and that in another language supplanted.

In such an arrangement, any significant text in the original transmission which is in the original language can be replaced by text keyed in via the keyboard and stored for appropriate display with the played back video signal such as the credits at the beginning and ending of a film and/or any important text appearing in any of the sequences during the film.

The invention also lies in an arrangement wherein a remote transmitter/receiver includes a camera or other video signal source whereby data transmitted can be mixed with the signals from the tuner for display in conjunction with or in place of at least part of the signals from the tuner, on the television screen.

The remote transmitter may transmit audio information as well as picture information.

The remote transmitter may transmit a warning message for display in a discrete region of the screen in conjunction with the picture signal derived from the tuner signals, giving the viewer the choice of selecting either the whole or partial substitution of the displayed picture from the tuner, with information which may be graphical or pictorial with or without sound, derived from the remote transmitter.

Thus a baby monitoring camera and microphone with noise actuated lighting and message transmitting device may be linked to a unit embodying the invention to supply a warning signal for display along the bottom of the TV picture as a message to the viewer indicating that the baby has cried. The viewer can then select the picture content of the transmission to view the baby by the remote camera to determine if the child needs attention.

Alternatively a unit embodying the invention could form part of a surveillance system enabling a security guard to watch a television programme but be alerted with a warning message if a door or window is opened or a beam is broken or a sound is received by a remote microphone. As with the illustration of the baby monitoring system, a remote camera can also be actuated by the opening of the door or window etc and the security guard can select the output of the camera for display on the television screen either to partly or wholly obscure the television picture he is watching to enable the guard to monitor the region containing the door or window or the beam which has been broken or in which the sound has arisen.

-t is an advantage of the invention that the television receiver can be operated in a normal mode with the sound at normal volume since the viewer can relax in the full knowledge that any remote sound which would normally be drowned out by the sound from the television broadcast, will nevertheless be received by a remote microphone and will trigger a warning message on the screen to alert the viewer to the fact that a sound has occurred which otherwise he or she would not have heard.

It is not essential for the remote transmitter/receiver to be permanently connected to the device embodying the invention and the invention also lies in apparatus and methods as aforesaid in combination with a modem or radio telephone receiver/transmitter unit in combination with auto dialling apparatus, whereby a link can be established with a remote transmitter/receiver unit by using a standard telephone line or radio telephone link, for transfer of data between the remote location and the unit.

Where picture information is to be transmitted via a conventional telephone circuit, signa compression and decompression may be required at transmitter and receiving ends of the link.

It will therefore be seen that the invention enables an ordinary broadcast television receiver to be used for displaying a message such as a warning message to a viewer but also to enable the viewer to select for display on the screen either in place of part of or the whole of the television picture which is being watched, pictures derived from a camera or other video source or data which can be displayed in a visual format on a television screen such as for example temperatures and pressures or the like in a chemical or industrial process obtained from probes or measuring devices associated therewith, and furthermore in conjunction with a hand held device and synchronous addressing techniques, can form the basis of a system enabling a viewer to interact with the television display, call up a list of services or articles required and select from the list the article or service desired, and for this information to be relayed to a remote location, or to receive messages from a remote location, all without the need for the viewer to move from where they are watching the television. Whereas this may simply be a matter of convenience for an able bodied person, it may be a valuable channel of communication for a disabled person or someone ill or infirm or unable to leave a chair or bed for medical or other reasons.

Whilst the invention envisages the use of a separate unit for connection to an existing television receiver, the invention is not limited to this arrangement and according to a further aspect of the invention, a television receiver having a tuner adapted to receive signals via aerial or from cable or satellite transmission may be modified so as to incorporate therein circuit means as aforesaid to enable messages to be displayed on the screen and/or alternative pictorial or graphical images displayed on the screen in conjunction with or in place of the incoming television programme picture, in response to signals supplied to a second input to the receiver.

The invention also lies in the combination of a television receiver as described or a combination of conventional broadcast receiver and separate unit connected thereto via the SCART interface, in the manner as aforesaid, in conjunction with a hand held unit for controlling not only the television but also the operation of the said additional unit or the additional circuits contained within a modifie television set, to enable a viewer to interact with the television receiver and supplementary circuits as provided by the invention to enable the viewer to call up a list of services or products which may be required and to identify using the hand held device, which of the services or products is desired and to transmit that requirement to a remote location simply by operation of push buttons cr a keyboard.

The hand held device may be connected to the television receiver and/or other circuit means provided by the invention, whether remote or incorporated in the receiver, by a direct connection or by a radio or infra-red link such as for example is utilised in remote television controls for selecting programmes and remote controls for controlling the operation of video recorders and the like.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a block schematic diagram showing how a television receiver can be controlled from an external unit embodying the invention, for mixing message as by superimposition on or substitution for part of, with an incoming video signal; Figure 2 comprises a block schematic diagram of the mixer device shown in Figure 1 connected to the television receiver ; Figure 3 is a schematic diagram showing how a television receiver can be used for superimposing messages over off-air or distr-buted TV picture signals ; Figure 4 is another schematic diagram illustrating how television signals of one standard such as SVHS or Hi8 can be converted to VHS standard, for copying on a VHS recorder, using a mixer unit embodying the invention ; and Figure 5 shows how a +12V can be derived from the external unit for application to the SCART socket pin 8.

Detailed description of drawings In Figure 1 a standard television broadcast receiver is identified by numeral 10 having an aerial socket 12 to which the normal antennae lead is connected. The receiver essentially comprises a tuner unit 14 which decodes the incoming signals and produces therefrom a video signal and an audio signal (on another channel, not shown). The video signal is supplied along line 16 to video signal amplifying circuits contained within a section of the receiver marked 18, which additionally includes the power supply and line and frame scanning circuits associated with a cathode ray tube or other television display device 20, for displaying the signals supplied thereto.

The receiver includes a so-called SCART socket 22 of which pin 8 is a control pin. If +12 volts is applied to pin 8, a switch 24 within the receiver is operated so that the display section 18 now der-ves its input video signals from pin 20 of the SCART socket, rather than the output of the tuner unit via line 16.

Line 16 is connected to SCART pin 19 as well as switch contact 26 and SCART pin 20 is connected to the other contact 28 of switch 24.

In the position shown, the receiver-tuner derived video signal is supplied direct to the display 18. With the switch in the other position (not shown) the video signal appearing at pin 20 on the SCART socket is supplied to the display device 18.

During playback of a recorded tape (whether pre-recorded or recorded from a live television broadcast signal) +12 volts is applied to pin 8 so that the display only receives signals from the video recorder via pin 20 of the SCART socket. In this mode signals derived from any signal are prevented from reaching the input to the video signal amplifying circuits of section 18, since otherwise conflict would occur.

Some video recorders generate a voltage to inhibit the transfer of tuner derived video to the display, and video signal generating circuits within the video recorder (not shown) generate a blank screen, typically a blue screen, on which words and numbers appear, to assist the user in setting up the recorder or selecting the programme which is to be recorded etc. However no provision is made for displaying data such as this superimposed over the picture.

In accordance with the present invention, a device embodying the invention and denoted by reference numeral 30, has a video in terminal 32, a video out terminal 34 and a control terminal 36 which are connected to a SCART plug (not shown) so that terminal 32 is connected to pin 19, terminal 34 to pin 20 and terminal 36 to pin 8 of the SCART socket.

Within unit 30 is a control voltage source 38 for providing a positive voltage (typically +12 volts) to terminal 36, and a mixer 40 one input of which is connected to the video in term additional memory means may be provided on the mother-board associated therewith.

The character generator 44 is adapted to generate digital signals which if presented in synchronism in an appropriate sequence via the input terminal 42, will appear as video signal representative of letters or numerals or other graphical indications for supply via line 58 to the video in pin 2C of the SCART socket, and therefore in the presence of a +12 voltage on the control pin 8, via the switch 24 to the input of the video amplifying circuits of display device 18, for presentation on the television display device 20.

The mixing device 40 is indicated in simplifie format in Figure 1, and a more complex system would be provided in practice tc allow different signal combinations to be produced.

Although not shown, the SCART socket 22 includes additional pins for sound-in and sound-out, and unit 30 can include similar input and output terminals for sound, and a mixing unit (not shown) under control of signals generated by the microprocessor 54, or by another processor, for mixing the audio signals. The control signal on pin 8 can be adapted to switch audio signal amplifying circuits 60 in section 18, to receive audio from the sensor socket"audio-in"pin, instead of from the timer section of the receiver. In this way the sound signal derived from a broadcast television signal, can be prevented from reaching the sound amplifying circuits 60 and loudspeaker 62 in section 18 of the receiver, and the sound signals mixed with others or replace by others, from another audio source (not shown). (Although one audio channel and one loudspeaker is shown it is to be understood that multiple circuit channel audio, can be accommodated using a plurality of audio amplifying circuits and an appropriate number of loudspeakers).

Figure 2 shows in more detail the video circuits associated with unit 30 in Figure 1. Details of the audio channels are not shown.

In order to handle so-called S-video signals in which the Y and C components are separated, two mixers are provided namely 64 and 66. Two signal paths are therefore provided, one for the Y component and the other for the C component, identified by reference numerals 68 and 70 respectively. Buffer amplifiers 72 and 74 are supplied with Y and C signals either directly from a YC input socket 76 or from a YC separating circuit 78 supplied with a composite video signal from a composite video input terminal 80. Multiple switches forming an input selector 82, enable the Y and C inputs from 76 or outputs from the separator 78 to be connected to the Y and C buffer amplifiers as appropriate. A second similar pair of switches are ganged to provide synchronisation selection. These switches are identified by reference numeral 84. In one position the sync pulses are derived from the incoming video signals, using the sync separator 86. In the other position an internal timebase generator 88 controlled by a crystal 90 supplies sync pulses to the Y buffer amplifier 74.

The separated sync pulses are supplied from 86 to synchronise a graphics controller module 90, output of which controls a grey scale generator 92, which supplies the second input signal to the mixer 66.

The chrominance signal (C) is decoded to provide sync pulses in unit 94 and these controls a colour encoder module 96 supplied with output from the graphics controller 90 to provide a synchronised chrominance signal as a second input to mixer 64.

The outputs of the two mixers are buffered by amplifiers 98 and 100 and their outputs are supplied direct to the Y and C terminals of a YC output 102, and to the inputs of a YC mixer 104 which provides a composite video signal via a buffer amplifier 106 to a composite video signal output terminal 108.

The graphics controller 90 is controlled by a microprocessor 110 which in turn derives programme information from an EPROM 112. Data car. be added to the EPROM via the microprocessor 110 and a socket 114 is provided to which a standard Qwerty computer keyboard such as 52 (see Figure 1) can be connected.

Additionally an XCON socket is provided having input and output terminals by which a control voltage can be applied to pin 8 of the SCART socket of the television receiver as described in relation to Figure 1. The XCON socket is denoted by reference numeral 116. The transmit and receive paths from the socket connect the latter to the microprocessor 110.

A further multiple path socket 118 is provided by which a joystick or mouse can be connected to the microprocessor.

A second EPROM 120 serves to store signals from which character can be generated and these signals are made available for the graphics controller under the control of the microprocessor.

A random access memory 122 together with back-up battery 124 provides storage for complete pages of data compiled by entering the information via the keyboard and assembling words and devices and graphics as required.

The supplementary input to mixer 64 can be switched between colour encoder generator 96 and a buffer amplifier 126, and that to mixer 66 between the output of the grey scale generator 92 and the output of another buffer amplifier 128. The switches which are designated 130 and 132 respectively correspond to the input selector switch 82 in that in one position the signals to be mixed are the outputs of the graphics controller, and in the other case the outputs from the two buffer amplifiers 126,128. The purpose of these alternative inputs to the mixers 64 and 66 is to allow the Y and C components of a second live video signal to be supplied to the mixers 64,66 so that instead of mixing words or warnings with the original video signal from the tuner, video signals from another source such as a VCR or camera can be mixed with the broadcast derived video signal instead. As is well known, the second and first video signals must be synchronised to allow for such mixing to occur and this may be achieved by synchronising one source of signal to the other, or in any other conventional way. A further input selector is provided in the form of a ganged pair of switches 134 and 136 which switch between an S-video input 138 and the output of a YC separator stage 140 supplied with a composite video signal from a composite video input 142.

With the switches 130 and 132 in the positions shown, mixers 64 and 66 serve to mix character generating signals with the broadcast derived signals. In the other position, the broadcast derived signal is mixed with a video signal supplied to the YC input 138 or the composite input 142.

Although r. ot shown, signals supplied to the mixers 64 and 66 may be gated so as to cause one of the incoming signals to be displayed in one part of the television display and the other in the remainder of the display or in another discrete region thereof.

Alternatively one signal can be superimposed over the other with an appropriate darkening of the background signal to allow the superimposed signal to appear more prominently and be more easily visible in the display.

Figure 3 shows the connections which may be made to a device embodying the invention, designated by reference numeral 30 to allow a signal from a second source to be mixed with a broadcast signal for display on a television set. To this end the television monitor is denoted by reference numeral 144, the computer keyboard by reference numeral 146 and a power supply for the unit 30 by reference numeral 148. As shown the composite video input and output terminals are employed together with left and right stereo audio channels. Thus connections from the SCART socket are made via conductors 148 for the composite video signal and 150 and 152 for the left and right audio channels. The composite output terminal of the unit 30 is connected via conductor 154 to the composite video input of the TV monitor 144 and the left and right stereo audio channels are connected via conductors 156 and 158 to appropriate terminals of the SCART connector. The latter is denoted by reference numeral 160. The aerial to the broadcast receiver 144 is denoted by reference numeral 162.

The mixer unit 30 may be used in an alternative mode such as shown in Figure 4 in which the S-video video output of a video camera video source such as 164 is shown connected to the Svideo input terminal of the unit 30 via lead 166. The composite output terminal of the unit 30 is shown connected to the composite input of a video recorder 168 which is connected in a conventional manner with a TV monitor 170. Left and right audio channels are connected in a similar way between the camera 164 and the unit 30, and between the unit 30 and the video recorder 168.

In this mode the S-video output from the source 164 is combined into a composite video signal by the circuitry within unit 30 so that a composite signal corresponding to the S-video signal from the source, is generated, and this can then be recorded on a standard video recorder which otherwise would not be able to handle the S-video signal.

Timebase correction may be employed by switching the synchronisation control on the unit 30 to Internal Sync using switch 84 of Figure 2. Alternatively synchronisation using the video signal from the source 164 may be sufficient.

Although not shown in Figure 3, a communication is provided between the XCON socket of the unit 30 and the SCART socket 160 to provide for control of the internal switch within the television monitor, as described in relation to Figure 1.

The control voltage can alternatively be supplied by the video cable by adding a 12 volt DC component to the video signal and separating the DC component from the video signal at the SCART socket. The components needed to separate the DC component from the video signal may be housed within the SCART connector.

This is shown in Figure 5 which illustrates how +12V can be supplied to pin 8 of a SCART socket of a TV receiver. The presence of 12 volts on that pin controls the transfer of video signals from the tuner output to the input of the video signal amplifier stages of the receiver and the 12 volts can be supplied to the SCART plug from a unit such as 30 in Figure 1 without the need of a separate cable. This is of benefit in installations where for example the video signal is to be transmitted over some distances from a central location such as an office or reception area of a hotel, to each of the TV receivers in the various rooms in the hotel.

As shown, a +12V supply (the negative pole of which is grounded) is connectable via a switch 174 and HF choke 176 to the video signal line 178. A capacitor 180 isolates the video signal source (not shown) which supplies video signals to the terminal 182 from the 12 volt supply, and the choke 176 prevents video signals reaching the 12 volt source (and also prevents the latter from short circuiting the video signal to ground).

At the SCART socket end, the video signal is separated from the 12 volt DC component conveyed along the line 184, by a second capacitor 186, and the line 184 is connected to pin 8 in the SCART plug via a second HF choke 188. A large capacitor typically an electrolytic capacitor 190 is connected between the choke 188 and the ground and the 12 volts is developed across this capacitor. The junction 192 serves as the +12V DC output terminal to connecting to pin 8 of the SCART plug. As previously mentioned, the components 186,188 and 190 may be housed within the SCART plus housing.

Claims (28)

1. CLAIMS 1. Signal processing means by which a second video signal can be superimposed over or displaced in place of a first video signal comprising: (1) first circuit means adapted to obtain from a broadcast television receiver a video signal which would normally be supplied to a video recorder for recording purposes; (2) second circuit means adapted to receive the first and second signals for mixing one with the other; (3) third circuit means for determinina the nature of the mixing to occur; (4) fourth circuit means for conveying a combined signal produced by the mixing of the two signals to a video signal input of a broadcast television receiver for display thereon ; (5) fifth circuit means adapted to prevent the internal transfer of broadcast derived video signals within the receiver for display thereon except via the said first, second and fourth circuit means.
2. 2. Signal processing means as claimed in claim 1, wherein the mixing is controlled so that one signal is superimposed over the other in a subsequent display.
3. 3. Signal processing means as claimed in claim 1, wherein the mixing is controlled so that the one video signal is displayed in one region of a television display and the other signal is displayed simultaneously in a different region of the television display.
4. 4. Signal processing means as claimed in claim 1, wherein the mixing is controlled so that part of one signal is blanked and the video signal from the second circuit means is synchronously incorporated into the blanked region of the display of the first signal.
5. 5. Signal processing means as claimed in any of the preceding claims, wherein the said fifth circuit means comprises a circuit adapted to provide appropriate control signals to pin 8 of a SCART socket, whenever a device comprising the said first to fourth circuit means is connected thereto, so that signals from the tuner section of the broadcast receiver are routed to the input of the video signal amplifier circuits of the receiver, from the pin 19 of the SCART socket, via the said first, second and fourth circuits, and pin 20 of the SCART socket.
6. 6. Signal processing means as claimed in any of the preceding claims wherein the video signal obtained from the broadcast receiver is derived from a live broadcast signal or from a camera or a video recorder or any other video source adapted to provide a modulated UHF signal suitable for decoding by the receiver tuner.
7. 7. Signal processing means as claimed in any of the preceding claims wherein the second video signal to be mixed with the broadcast derived signal may be a signal from a television camera or from a video recorder or video player such as a disc player or from a memory device in which signals can be stored for retrieval in a synchronous manner when required, which when retrieved generate a video signal representative of graphics or letters or numerals which can be mixed with the said first signal in any of the ways previously claimed.
8. 8. Signal processing means as claimed in claim 7, wherein the memory device contains signals which when read out generate a video signal corresponding to characters such as letters of the alphabet or numerals to allow a message to be displayed in combination with an original broadcast signal, on the receiver screen, either as a superimposition over the original video signal or a superimposition over a part of the original video signal or in an area of the screen in which the message signal is substituted for the broadcast signal.
9. 9. Signal processing means as claimed in claim 8, wherein the message signal to be displayed is superimposed over part or all of the displayed incoming broadcast signal and one of the circuit means is adapted to produce the brightness or contrast or chrominance or other parameters of the signal derived from the broadcast signal, so that the display of the broadcast signal appears less bright than normal over either the whole of the display or over that part of the display in which the message is to be displayed, so as to allow the characters forming the message to be seen more clearly.
10. 10. A signal processing device as claimed in claim 9, in which the signal generating characters forming the message is one which generates a generally black background on which the letters or numerals appear in a colour such as white or yellow.
11. 11. A signal processing method comprising the steps of introducing a second video signal into a first video signal for display in synchronism with the first, either superimposed over or in substitution for part of the first signal, comprising the steps of: (1) inhibiting the internal transmission of video signals from a television tuner section of a broadcast television receiver to a video signal amplifying circuit therein which supplies signals to generate a picture on the display device of the receiver; (2) conveying the video signal from the tuner section to a first input of a mixing device; (3) conveying the second video signal to a second input of a mixing device; (4) synchronously mixing the two signals therein and conveying the output signal from the mixer as an input signal to the video signal amplifying circuits of the receiver in place of signal derived from the tube inner section of the receiver.
12. 12. A signal processing method as claimed in claim 11, in which the video signal which is to be mixed with the broadcast derived signal is derived from a memory device such as associated with a microprocessor in a computer, and the memory is read a high speed in synchronism with the broadcast derived signals so as to generate a sequence of signals which when displayed will comprise a graphical display over or in place of the picture generated by the broadcast derived signal.
13. 13. A signal processing method as claimed in claim 12, where the signal which is to be merged with the incoming broadcast signal is in the form of a message and the characters can comprise letters or numerals or both.
14. 14. Signal processing apparatus for performing the method as claimed in claim 13, comprising a processor, a keyboard, a power supply, supporting electronic circuits comprising a socalled mother board adapted to support the processor and keyboard, a character generator driven by the microprocessor, circuit means for relaying signals derived by the character generator as an output signal to one input of the mixer for combining with video signals derived from a broadcast signal.
15. 15. Apparatus as claimed in the preceding claim, wherein the character generator comprising a digital memory in which sequences of a digital signal are stored, each sequence being representative of a character.
16. 16. Apparatus as claimed in claim 15, in which an optional memory device is provided in which characters defining sequences can be entered using the keyboard, to enable a message to be built up and stored either permanently or semipermanently in the device.
17. 17. Apparatus as claimed in claim 16, wherein the optional memory device is non-volatile memory.
18. 18. Apparatus as claimed in any of the preceding claims, further comprising an audio signal channel with switch means for diverting audio signals in a similar way to the video signals from the television receiver into the apparatus and selectively routing the audio signals back to the broadcast receiver for reproduction by the sound producing apparatus therein, either unmodified, mixed with other signals, or in which the said other signals are supplied to the receiver in place of the signals derived from the receiver.
19. 19. Apparatus as claimed in claim 18, wherein the signals to be mixed with the sianals derived from the receiver tuner unit comprise an alarm or warning sound to attract attention or indicate that a message is being displayed.
20. 20. Apparatus as claimed in any of the preceding claims, further comprising circuit means for enccding onto a carrier picture and sound signals from the output of apparatus as aforesaid, for generating a broadcast type television signal for supply to the aerial socket of a standard television receiver whereby a combined picture signal and optionally combined sound signal can be displayed on the subsequent television receiver.
21. 21. A method as claimed in any of the preceding method claims, wherein apparatus as claimed in any of the preceding claims is connected to the SCART socket of a television receiver and a carrier modulated recorded video signal is supplied to the aerial socket of the receiver and the apparatus as aforesaid is adapted to suppress the audio track of the originally recorded video signal and subtitles stored on a second video recording are displayed superimposed on or in the lower region of the screen of the television receiver, whereby a viewed who is hard of hearing can enjoy a television which did not include subtitles in the original signal.
22. 22. A method as claimed in any of the preceding claims, in which apparatus as claimed herein is connected to the SCART socket of a television receiver and a carrier modulated recorded video signal is supplied to the aerial input of the receiver and the apparatus is adapted to suppress the audio track of the originally recorded video signal and to substitute a different audio signal in place of the original audio track, thereby enabling a translation of an original commentary or audio track to be substituted.
23. 23. Apparatus as claimed in any of the preceding claims, wherein a remote transmitter/receiver includes a camera or other video signal source whereby data transmitted can be mixed with the signals from the tuner for display in conjunction with or in place of at least part of the signals from the tuner, on the television screen.
24. 24. Apparatus as claimed in claim 23, wherein the remote transmitter transmits audio information as well as picture information.
25. 25. Apparatus as claimed in claim 24, wherein the remote transmitter transmits a warning message for display in a discrete region of the screen in conjunction with the picture signal derived from the tuner signals, giving the viewer the choice of selecting either the whole or partial substitution of the displayed picture from the tuner, with information which may be graphical or pictorial with or without sound, derived from the remote transmitter.
26. 26. Apparatus as claimed in claim 25, wherein the remote transmitter of the receiver comprises a camera and microphone to be placed in the bedroom of a child and the apparatus of the invention is adapted to transmit a warning message superimposition on the television screen in addition to or in place of part of an incoming broadcast signal in the event that sound signals are received on the microphone in the bedroom.
27. 27. Apparatus as claimed in claim 26, wherein the apparatus includes a remote control unit and infra-red transmission link and switching means whereby a viewer in charge of the control unit, can selectively display the video signal from the camera in the remote bedroom in place of the incoming broadcast signal, or in place of part of the incoming broadcast signal to enable the viewer to see what is occurring in the bedroom.
28. 28. Apparatus as claimed in a preceding claim (number to be checked) wherein the remote transmitter/receiver unit forms part of a surveillance system and includes a camera and microphone and the apparatus according tc the invention is triggered to generate a warning signal for display on a television screen in addition to or in place of the displayed signal in the event that a warning electrical signal is generated as by the opening of a door or a window or by the breaking or a beam, or if a sound is received by a remote microphone associated with the system.