GB2162714A - Interface unit for interactive video system - Google Patents

Abstract

An interface unit for an interactive video system is disclosed which can be connected between one or more command units and one or more video sources to enable the command unit or units to communicate with one or more of the video sources and identify and retrieve data stored in such sources. The interface unit includes means 18, 20, 23 for generating an internal video signal and an audio signal and has means 21 for selecting one or more frames or lengths of video tape from one or more external sources. It incorporates means 26 for converting the format of the external recording to the format of the internally generated video signal and means 26 for selecting one or both of the internally generated and externally derived video signals. Synchronising means is provided to synchronise the internally generated and externally derived video signals and switch means 34 is operable for selectively switching between or mixing the internally generated and externally derived audio signals. <IMAGE>

Description

SPECIFICATION Interface unit for interactive video system This invention relates to an interface unit for providing an interface between a command unit and a memory bank or data storage system whereby stored data may be identified and retrieved on command.

The invention is of particular, but not exclusive, application to interactive video systems in which one or more picture frames may be identified and retrieved from a video source, e.g., tape or disc, and displayed on command. In such systems, the response of the viewer or operator to one or more displayed picture frames may in fact initiate the next command and determine which part of the stored data is next to be retrieved and displayed.

Generally, such video systems are specific or dedicated in the sense that the command unit will only retrieve and identify data from a specific video format, e.g., V.H.S., umatic or video disc. In some cases, the command unit in the form of a micro computer, interface unit and video source are constructed as a unit or package but it will be appreciated that this is relatively expensive. It will also be appreciated that many potential users of interactive video systems already possess one or more video sources and one or more micro computers and that will enable the command unit or micro computer to communicate with one or more video sources and identify and retrieve the data stored.

It is an object of the present invention to provide such an interface unit.

The interface unit of the present invention enables a micro computer or a series of micro computers, possibly of different specifications, to be interfaced with one or more video sources such as tape and disc systems to control random access to the stored information in the video sources thus providing means for presenting an interactive combination of video images and computer generated text and graphics.

Data is generated by the selected micro computer and transmitted under RS232 interface protocol to the interface unit. The latter has a computer program resident in one or more "Read Only" memory storage areas which enables the data to be converted into signals for the remote manipulation of the selected video device enabling the display of transmitted images and/or the display of computer generated text and graphics information.

One embodiment of the invention will now be described by way of example, reference being made to the accompanying block diagram illustrating an interface unit according to the invention.

For convenience of description, the interface unit illustrated is divided into ten parts or boxes shown in dotted lines and identified by the reference numerals 1 to 10.

The unit has an internal bus 11 along which data is transmitted in the form of bytes, each byte comprising eight bits. Parallel protocol is employed.

The box 1 represents the core logic area of the unit and comprises a Z80A CPU identified by the reference 12, at least one EPROM (two are shown and identified by the references 13a and 13b), a RAM identified by the reference 14, a system clock 15 and an expansion port 16. All except the clock 15 are connected to the bus 11. Also included is a Z80A CTC processor identified by the reference 12a which is connected to the bus 11 and which is used to control the generation of internal audio signals.

The CPU 12 is the central processor unit, the EPROMS 13a and 13b store the driver firmware for the unit and the RAM 14 is a temporary data storage area. The clock 15 generates timing signals for the CPU 12 and the expansion port 16 provides an addition facility if required. For example one or more additional video players could be connected through such an expansion port.

The box 2 contains the means for generating RGB (red, green, blue) video signals and comprises a CPU 17 connected to the bus 11 and giving access to logic signals, a graphics RAM 18 connected to the CPU 17 and providing a screen memory temporary data storage area, a video controller 19 which incorporates timing circuitry and is connected to the graphics RAM 18 and an RGB video signal generator 20 connected to the output of the graphics RAM 18 the output of which modifies the output of signal generator 20 according to required data structure.

As will appear hereafter, the units represented in the box 2 are an important part of the interface unit as they provide for the generation of a video signal which is separate from an externally derived video signal and can be mixed or overlaid therewith or selected as an alternative. The graphics RAM shown as storing 64K of bytes is expandable and, in effect, stores an image in accordance with command data stored in RAM 14 and converted into image data by the CPU 17 upon instructions received along bus 11. The video controller 19 reads the stored image into the RGB video signal generator 20.

The box 3 contains the VCR controller circuitry for communication with an external video tape player and includes a driver unit 21 connected to the bus 11 to transmit to the video tape player data representing the desired position or frame of the video tape and a receiver unit 22 which is also connected to the bus 11 and which receives from the video tape player data representing the actual position or frame of the video tape.

Box 4 comprises a sound generator 23 which is a common sound generation processor compatible with Z80 micro computers and capable of generating audio signals at a standard (unamplified) level.

A total of three frequencies of signal can be generated at any one time and these can be manipulated in pitch, tone and volume. The sound generator 23 is connected to the bus 11 and is associated with the Z80A CTC processor 12a which in fact forms part of the CPU unit 12. The processor 12a is connected to the bus 11 and, when instructed, interprets the data stored in RAM 14 and identifies the internally generated sound required and then, through bus 11, causes the sound generator 23 to generate the required audio signal.

Box 5 comprises logic circuitry 24 for communication with a configured device 25 (modified centronics parallel protocol).

Box 6 comprises a conversion and switching device 26 which is connected to the output of the RGB video signal generator 20, to the bus 11 and to the output lines RGB. It operates to convert an externally derived PAL video signal to an RGB video signal and to switch between externally derived video signals which are supplied along line 27 and the internally generated RGB video signals derived from the signal generator 20.

Box 7 incorporates serial communication ports 28 and 29 which are RD 232 ports and a Z80A Dart processor 30 which is connected between the bus 11 and the ports 28 and 29 and which serves to convert the serial input to the ports 28 and 29 to parallel protocol for the bus 11 and the parallel protocol of bus 11 to serial form as output to the ports. The port 28 is for communication to an external micro computer and the port 29 may be similarly used or may be connected to an externally configured device such as a Phillips Lazer-Optic videodisc player. Communication of instructions is according to the player manufacturer's specification (comparable to JVC VHD).

Box 8 comprises a synchronising unit 31 which is connected between the video controller 19 and the conversion and switching device 26. It operates to lock the internally generated sync signal to the externally derived sync signal derived from the video tape. This locking of the two signals is achieved by speeding up or slowing down the internally generated sync signal in an attempt to identify the external sync pulse. Once the external sync pulse is identified, synchronisation is repeated for each sync pulse to allow for variations in the stability of the external signal. Extreme variations is the stability of the external signal will result in loss of synchronisation and loss of the ability to display simultaneously on a screen both internally generated and externally derived video signals.It will be appreciated that the "still frame" facility of an external video source may not always generate acceptable signals for the purpose of synchronisation. Where no external sync pulse is present, the video controller 19 is allowed to free run to enable video signals to be generated internally without the requirement of an external sync source.

Box 9 is concerned with selecting the audio signal to be transmitted to the user along lines 32 and/or 33 from the range of available sources. A switching unit 34 is supplied with internally generated sound from the sound generator 23 along line 35 and from the external video source along line 36. Additional or alternative audio sources may be used. Audio channels may be selected individually or jointly (mixed), this being achieved according to the bit setting of the byte of data transmitted to the audio switching circuitry, which serves to open or close logic gates, the signals allowed to pass through converging into line 32 and/or 33 for external transmission.

Box 10 comprises an amplifier 37 connected to line 33 and providing an output along line 38 for earphones and an output along line 39 for a loudspeaker.

In the operation of the interface unit described, instructions from an external micro computer are received at the port 28 in serial form, converted into parallel protocol by the Z80A DART processor 30 and placed in the RAM 14 upon command from the CPU 12.

The instructional data, once it has been loaded in the RAM 14 is checked for syntactic errors and data validity, i.e., correct spelling of the command work and that the related parameter data is within the defined and acceptable ranges. A message of acknowledgement is then returned to the micro computer to inform of the correctness or invalidity of the instruction. The instruction is then disseminated and actioned according to the command and the parameters.

The RAM 14 also identifies the relative priorities of the commands received.

The CPU 12 is composed of an accumulator within which data is manipulated according to instructions derived from the EPROMS 13a and 13b, X and Y Registers which are manipulatable hold areas for relational data manipulation within the accumulator, and status registers which contain status information of data held within the accumulator.

The CPU 12 is activated by timing signals from the clock 15 at 4 MHz, each signal activates the CPU 12 which reacts according to its contents which are obtained from the programs in EPROMS 13a and 13b. This activity takes the form of movement and manipulation of data to and from the RAM 14 and other areas of the interface unit (notably for transmission to other devices) and within the accumulator of the CPU 12.

The CPU extracts the stored information from the RAM 14 and compares and commands with those held in the programs in the EPROMS 13a and 13b On successfully making a match various functions are activated, e.g., video source control, text generation, graphics generation, computer sound generation.

Where an internally generated video signal is required, the CPU will extract the data from the relevant part of the RAM 14 and transmit this data in an appropriate form to appropriate addresses in the graphics RAM 18. The timing circuitry of the video controller 19 will read this data into the generator 20 where the data is converted to RGB video signals by the generator 20. This timing circuitry is linked with the synchronising unit 31 for the purpose of synchronising the internally generated and externally derived video signals as previously explained.

Where the input requires a video signal from an external source, the data is transmitted to an external video player in the same format generated by the manufacturer's remote handset or Edit controller. This data is transmitted to the external video player by the driver unit 21 and the receiver unit 22 receives and returns data representing the status and/or mode of operation of the player.

The Conversion and Switching device 26 automatically decodes PAL signals received from the external video source along line 27 to an RGB video signal.

Composite video is a single signal containing the three colour components red, green and blue plus the sync signal to which the others are encoded.

Conversion is achieved by separating these four components into separate signals. The three colour components contain the appropriate level of luminence and intensity of that colour.

The switching section of the device 26 receives instructions from the CPU 12 for selecting the appropriate video source. This selection is totally between the two sets of signals, i.e., externally derived and internally generated. The device 26 can also be set to combine the two sets of signals resulting in both sets of screen information being on display at the same time. This is effectively combining the two sets of signals to form one. Display of the two sets of signals as separate signal sets at the same time is achieved by switching at high speed during the period of a single line scan of the visual display unit. Switching speeds of up to 20 MHz allow for 1024 switches to be made within the duration of a single line scan. For this to be possible, the two signal sets must be synchronised and this is achieved by the synchronising unit 31.

Instructional data to the interface unit is generated in a predetermined format and consists of two parts; the command itself, followed by related parameter data.

For example, the instruction "VID,Q3,CONT,23564" contains the command identifier VID which indicates that this instruction is to be directed to an external video device. "Q3" indicates that it is to be placed in a specific position within a queue of commands such that it will be actioned in advance of other instructions of a higher queue index. "CONT" is the actual command itself, being the instruction to continue playing until the following parameter value 23564 is reached.

It will be appreciated that although the accompanying drawing only shows one box 3 and one box 9 and one box 10 associated with an external video player, the bus 11 may be expanded through the expansion port to accommodate additional video players, be they tape or disc or even additional micro computers, suitable driver and receiver units and switching units being associated with such additional players or computers.

The interface unit of the present invention not only provides an interface between micro processors or other command generating units and video tape or disc layers to enable an interactive video system to be assembled from units which may already be in-house or readily available, but it also generates its own audio and video signals and enables either one or both of the generated video signals and externally derived video signals to be displayed, the necessary synchronising means being incorporated for simultaneous display and also enables either one of the generated audio signals and the externally derived audio signals to be selected or both signals to be mixed.

It will be appreciated that the interface unit of the present invention enables interactive video systems to be assembled using existing micro processors and video players. The unit incorporates means for generating video signals and audio signals, means for selecting one or more frames or lengths of video tape from one or more external players, means for converting the format, e.g., PAL, of the external recording to the format of the internally generated video signal, means for selecting one or both of the internally generated and externally derived video signals, means for synchronising the internally generated and externally derived video signals and means for selectively switching between or mixing the internally generated and externally derived audio signals.

Claims (15)

1. An interface unit for connection between an external command unit and an external video source to provide an interactive video system, the interface unit comprising means responsive to input command signals generated by the external command unit to identify the frame or frames or length of video tape required and retrieve video signals representing such frame or frames or length of video from the external source and means for converting such video signals to a predetermined format.

2. An interface unit according to claim 1 having input means for connection to one or more external command units, input/output means for connection to a plurality of external video sources and wherein the input command signal responsive means is operable to identify the video source holding said frame or frames or length of video tape.

3. An interface unit according to claim 1 or 2 including means for internally generating a video signal and means for selecting one or both the internally generated video signal and the retrieved video signals.

4. An interface unit according to claim 3 including means responsive to the selection of both the internally generated video signal and the retrieved video signals to synchronise both signals.

5. An interface unit according to any one of the preceding claims incorporating means for internally generating an audio signal.

6. An interface unit according to claim 5 including means for identifying an audio signal associated with the retrieved video signals and means for selectively switching between or mixing the internally generated audio signal and such associated audio signal.

7. An interface unit for an interactive video system comprising means for generating a video signal and an audio signal, means for selecting one or more frames or lengths of video tape from one or more external players, means for converting the format of the external recording to the format of the internally generated video signal, means for selecting one or both of the internally generated and externally derived video signals, means for synchronising the internally generated and externally derived video signals and means for selectively switching between or mixing the internally generated and externally derived audio signals.

8. An interface unit for connection between one or more external command units and one or more external video sources to provide an interactive video system, the interface unit comprising one or more input channels for connection to such external command units whereby input command data can be supplied to a bus, such input data representing one or more demand functions, one or more input'output channels for connection to such external video sources, a memory unit connected to the bus to receive and store the command data, and a central processor unit connected to the bus and operable to identify the demand functions in the stored command data and through the bus address, the or each function unit corresponding to the desired function, such function units comprising:: a) means for internally generating a video signal; b) means for internally generating an audio signal; c) means for driving one of the video sources to retrieve one or more frames or length of tape as video signals; d) means for converting such retrieved video signals to the format of the internally generated video signal; and e) means for selecting one or both of the internally generated video signal and the retrieved video signals.

9. An interface unit according to claim 8 in which the or each input channel for connection to a command unit is connected to the bus through means operable to convert the input command data to the protocol of the bus.

10. An interface unit according to claim 8 or 9 including a read only memory device holding a computer program and connected to the bus to control the manipulation of the stored data by the central processor unit in accordance with such computer program.

11. An interface unit according to claim 10 in which the central processor unit is operable to compare the stored command data with the computer program to identify an acceptable demand function.

12. An interface unit according to any one of claims 8 to 11 in which the means for internally generating an internal video signal comprises an image processor connected to the bus and responsive to a corresponding demand function to convert stored data to corresponding image data, a graphics RAM for storing such image data, and a video controller incorporating timing circuitry for releasing the image data to a video signal generator.

13. An interface unit according to claim 12 including synchronising means connected between the video controller and the video signal generator.

14. An interface unit according to any one of claims 8 to 13 including means responsive to any external audio signal associated with the retrieved video signals and means for selectively switching between or mixing the internally generated and external audio signals.

15. An interface unit for an interactive video system constructed, arranged and adapted to operate substantially as herein described with reference to the accompanying drawing.