JPS6133424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for representing alphanumeric text or other set information in a video signal in at least one television scan line during a vertical blanking interval in which no normal image information is present. A television reception device suitable for use in a character television transmission system that transmits encoded data pulses,
a data selection and acquisition device for selectively extracting encoded data pulses from a received video signal; a data storage device for storing the extracted encoded data pulses; and a data storage device for storing the extracted encoded data pulses; a decoding device for producing a video signal usable for display on a television screen from said stored encoded data pulses, and a decoding device for producing a video signal which can be used for display on a television screen and locally generated within the television receiver itself and used for display on a television screen; The present invention relates to an apparatus for television reception, comprising an oscillator for generating a synchronization signal which can be used.

The television receiver may be provided with a suitable television display, or the television receiver may be adapted to supply a video signal to a separate television receiver.

Further, the television transmission system of the above-mentioned character is described in British Patent No. 1370535.

Television reception equipment of the type mentioned above was introduced in 1976.
“Mullard Technical” published in September.
Information Article 34” and is known.

It is known from DE 26 51 635 to generate a locally generated synchronization signal using an oscillator device provided in a television reception device of the above-mentioned type, in which case the normally received television In the absence of a synchronization signal, for example, in the absence of a broadcast video signal containing a separable synchronization signal, a locally generated synchronization signal is generated to provide a television display of the stored data. Stored data for display can be received from television video signals or from conventional telephone transmission lines. The apparatus for television reception described in the above-mentioned German patent application prevents the operation of the television synchronization separation stage when the received television signal falls below a predetermined limit level, and instead It is also configured to generate a locally generated synchronization signal.

The present invention provides a television receiver of the type described above which is capable of obtaining both a separated synchronizing signal and a locally generated synchronizing signal, in which the separated synchronizing signal is not obtained because the received television signal is absent or inadequate. television reception by being able to selectively use one or the other of these two forms of synchronization for different display conditions, compared to the simple example of using a locally generated synchronization signal only when the This is based on the recognition that it is possible to bring about significant advantages in the operation of the device.

The present invention transmits encoded data pulses representing alphanumeric text or other message information in a video signal in at least one television scan line during a vertical blanking interval in which no normal picture information is present. A television image receiving device suitable for use in Character's television transmission system,
a data selection and acquisition device for selectively extracting encoded data pulses from a received video signal; a data storage device for storing the extracted encoded data pulses; and a data storage device for storing the extracted encoded data pulses; a decoding device for producing a video signal usable for display on a television screen from said stored encoded data pulses, and a decoding device for producing a video signal which can be used for display on a television screen and locally generated within the television receiver itself and used for display on a television screen; an oscillator for generating a synchronizing signal that can be used for a television receiver; A switching circuit is provided for coupling to the video signal output terminal of the front stage of the image receiving device or to the output terminal of the oscillation device, and the oscillation device is connected to a phase lock loop by the output of another synchronizing signal separation circuit. The input terminal of another synchronization signal separation circuit is coupled to the video signal output terminal of the preceding stage, and the phase lock loop is configured to synchronize if the signal quality of the video signal is unacceptable. Alternatively, it is characterized in that it is made inactive by a signal quality detection circuit that detects the absence of a video signal. Here, "the oscillation device can be synchronized via a phase-locked loop (by the output of another synchronization signal separation circuit)" means that the oscillator constituting the oscillation device can be, for example, a phase-locked oscillator.

The television receiving apparatus according to the present invention has the advantage that by using a locally generated synchronization signal to display message information on television, the display can be performed with less jitter than when using a separate synchronization signal. I made sure that I could get it. Another advantage is that by phase-locking the locally generated synchronization signal to the separated synchronization signal whenever possible, the locally generated synchronization signal can also be used for synchronization purposes when acquiring encoded data pulses from the incoming video signal. It will be done.

As a variation of the invention, separate synchronization pulses may be used for television display when the received video signal is unacceptably noisy and unsuitable even when normal image display is selected. Provision may be made to prohibit the use of synchronization signals and to use locally generated synchronization signals instead. In this case, any pre-stored data, such as channel information, such as that generated by the television remote control, can be clearly superimposed on the displayed image without further deterioration of the television image display. This is an advantage.

The present invention can also be applied to the above-mentioned type of television reception apparatus used in the character television transmission system. Additionally, the above-described television receiving apparatus which selectively uses either a separate synchronization signal or a locally generated synchronization signal as described above may display alphanumeric text or other message information simultaneously with normal image information; These can be configured to be displayed selectively.

The invention will be explained with reference to the drawings.

The drawings illustrate television images resulting from the image information in a conventional over-the-air or cable television video signal, and alphanumeric text resulting from encoded data pulses transmitted during the vertical or field blanking period of the video signal. 2 shows a character television transmission device having a television receiver for selectively displaying other message information. Furthermore, message information such as that described above can be displayed simultaneously with the television image; for example, message information such as subtitles and subtitles can be superimposed on the television image. The television receiver also receives message information sent from other sources, such as experimental news, post office, etc.
View Data System (British Post Office
It is also possible to receive and display view data (see "Wireless World", February to May 1977 issue), such as that transmitted by a telephone line of the View Data System.

The incoming television video signal VS appears at the input line 1 of the television receiver via an input circuit 2 comprising conventional amplification, synchronization, intermediate frequency and detection circuits. It is assumed that the input circuit 2 is coupled to a television transmitter 3 via an ordinary wireless or cable transmission line 4. The transmitter 3 comprises, in a known manner, a device for producing television picture information, a device for producing alphanumeric text or other message information, and a television receiver for transmitting a picture signal representing the picture information and coded data pulses representing the message information. and an apparatus for generating a suitable composite television video signal including synchronization, equalization and blanking signals necessary for operation of the apparatus.

In the case of normal image display in a television receiver, the received video signal VS is supplied to a selection circuit 5 having a selection switch 6. When the switch 6 is closed, the video signal VS is supplied to the color decoder 7, which generates RG and B color component signals for image display, and these color component signals are sent to the video interface. It is supplied via a circuit 8 to the red, green and blue electron guns of a color television picture tube 9. Picture tube 9
A normal horizontal synchronization pulse LS and a vertical (field) synchronization pulse FS are supplied from a synchronization separation circuit 11 to the time axis circuit 10 for the time axis. The synchronization separation circuit 11 extracts the synchronization pulses LS and FS from the incoming video signal VS or from a locally generated synchronization signal as will be described later.

The encoded data pulses representing message information in the video signal VS do not affect the display of the image. The reason is that these encoded data pulses are
This is because it occurs during the above scanning lines. Most of the scan lines occurring during the vertical blanking interval can be used to send encoded data pulses representing message information. However, in the experimental BBC/IBA teletext system on which this invention is based, the scan lines carrying the encoded data pulses were compared to the even numbers in the 625 scan line broadcast television system used in the United Kingdom. It is currently proposed to be limited to the 17th and 18th scanlines of fields and the 330th and 331st scanlines of odd fields.
(British Broadcasting Corporation,
Independent Broadcasting Authority and
British Radio Equipment
“Broadcast Teletext” co-published by the Manufacturers’ Association in September 1976.
(See "Specification") The video signal appearing on input lead 1 is processed by a data extraction circuit 12, a data clock pulse generator 13,
Data reception gate 14 and data acquisition circuit 15
It is also supplied to a data selection and acquisition device having a
The message information represented by the coded data pulses contained in the video signal VS is divided into various pages of information, each page being divided into pages in which the coded data pulses representing each page are accompanied by updates of the information or It is assumed that the image is displayed as a whole on the screen of the picture tube 9 so as to be repeated periodically without any interruption. It is also assumed that each page of message information is identified by a page address code included in the encoded data pulse and determining the page number. The particular coded data pulse acquired by data acquisition circuit 15 at any instant is controlled by code selection circuit 16. (This control is shown by wide arrows representing the presence of n parallel channels forming an n-bit channel link for transmitting the n-bit information necessary for data selection, forming a multi-bit channel link in a television receiver. (The other groups of parallel channels are similarly shown as channels and numbers of information bits m, p, q, r and s.) The acquired coded data pulses originate in the data acquisition circuit 15 from the clock pulse generator 13. The signals are sequentially synchronized and taken out by clock pulses. The acquired encoded data pulses originating from the data acquisition circuit 15 are supplied to a data storage device 17 via an m-bit channel link. For each character (or other item of information) contained in the message information, a byte of m bits is required, for example m=7.

Data storage 17 can store an entire page of message information. In a typical teletext transmission, each page of message information contains up to 24 lines of characters, and each line contains up to 40 characters. Therefore, in order to identify different characters for one page, the coded data pulse also contains an address code for each character, this address code having r bits, which is transmitted from the data acquisition circuit 15. Data storage device 1 via r bit channel link
7.

Because of the limited transmission time available for transmitting coded data pulses representing message information, for example, coded data pulses for only one row of characters can be used during one television scan line during vertical blanking. Since there is only so much time available for transmission, it is necessary to store character data for one page of message information in sequential rows in data storage 17 over a relatively large number of television field periods. The storage of character data row by row in the data storage device 17 is carried out under the control of address codes supplied from the data acquisition circuit 15 via the r-bit channel link. Also, the encoded data pulse is the view data.
A storage device 17 can also be supplied from the input circuit 18 via an s-bit channel link, and these encoded data pulses are supplied via a telephone line 19 from a telephone (not shown). Other sources of message information generating encoded data pulses that can be received by data storage device 17 can be, for example, a video cassette player.

The television receiver is further provided with a decoding device comprising a character generator 20 and a parallel-to-serial converter 21. Character generator 20 generates character generator data in response to character data stored in data storage device 17, and uses the character generator data to generate the character represented by the stored character data. Generates a new image signal to display. As mentioned above, the various characters can be represented by separate m-bit bytes. The bits of each byte are provided in parallel from data storage 17 to character generator 20 as p-bit bytes. The character format for the characters to be displayed can be a rectangular matrix with separate elements arranged in rows and columns, which format acts as a character generator 20 and divides the bits of character generated data into rows and columns. Moreover, it is retrieved from fixed memory, which occurs one line at a time. Character generation data is required when displaying characters by selectively brightening the screen of the picture tube 9 by modulating the video signal, so each row of bits (for example, q Character generation data (as 1's and 0's) are produced serially by using a parallel-to-serial converter 21 which converts the data (=5) into serial form.

In order to display characters on the screen of the picture tube 9 using standard scanning lines and frame scanning, the logic circuitry of the television receiver is appropriately organized, and for each row of characters to be displayed,
All characters in this row are constructed as a whole in sequential television scan lines, and all rows of characters are constructed as such in sequential order. Therefore, a large number of television scan lines are required to construct one row of characters. In the first television scan line, character data supplied from the data storage device 17 to the character generator 20 causes the character generator 20 to
generate character occurrence data for the first row of each separate element for the character;
Character generation data for the first row of each separate element is generated for the second character of the row, and so on for successive characters in the first row. In the second television scan line, character generation data for the second row of each separate element is generated sequentially for each character in the first row, and character generation data for the other television scan lines is generated in the same manner. bring about.

The output of the parallel-to-serial converter 21 is fed to a color coder 22 which produces R', G' and B' color component signals for the character display, these color component signals being fed to the video interface circuit 8.
The color coder 22 can be controlled by selection items of character data in the data storage device 17 (this control method is not shown), and can display controlled colors. Of course, a monochrome image can also be displayed with monochrome characters, and in this case, the color decoder 7 and color coder 22 are omitted.

The television receiver has a data receiving gate 14 as part of the data selection and acquisition device, as described above. The encoded data pulses extracted from the incoming video signal VS by the data extraction circuit 12 pass through this data receiving gate 14 controlled by the signal quality circuit 23 to the data acquisition circuit 1.
5. This signal quality circuit 23 (a concrete example of which is described in British Patent No. 37533/77) is configured to generate encoded data pulses when the signal-to-noise ratio in the incoming video signal VS falls below a predetermined value. An inhibit signal IS is supplied to the data receiving gate 14 in order to inhibit the data receiving gate 14 from receiving the memory. As described in the above-mentioned UK Patent Application No. 37533/77, this signal quality circuit 23 performs a An acceptable signal-to-noise ratio can be determined.

In order to be able to selectively use the separated synchronization signal and the locally generated synchronization signal, the incoming video signal VS is separated by a synchronization pulse separator 24 and an electronic switch 25 (for simplicity of the drawing). The electronic switch is shown as a mechanical changeover switch having fixed terminals 26 and 27 and a changeover contact 28). The separated horizontal synchronization pulses originating from the synchronization pulse separator 24 are provided to a phase lock oscillator 29 which drives a timing circuit 30 and also to a first input terminal of a signal quality circuit 23. The timing circuit 30 includes the data acquisition circuit 15, the code selection circuit 16, and the data storage device 1.
7. Supply appropriate clock pulses (timing pulses) to the view data input circuit 18 and character generator 20; In addition, the timing circuit 30
drives the synchronization pulse generator 31 such that the synchronization pulse generator 31 produces a locally generated synchronization signal in response to the output from the timing circuit 30. The locally generated horizontal synchronization pulses from the synchronization pulse generator 31 are supplied via conductor 32 to a second input terminal of the signal quality circuit 23. These locally generated horizontal synchronization pulses are also combined with vertical (field) synchronization pulses at gate 33. These vertical sync pulses originate from a sync pulse generator 31 via conductor 34 and are synchronized with the incoming vertical sync pulses. gate 33
The output of is supplied to switch 25. A phase lock oscillator 29, a timing circuit 30 and a synchronous pulse generator 31 constitute an oscillation device.

A user control 35, which may be any suitable known form of hand-held remote control, controls channel selection and adjustment, etc. in the input circuit 2, as well as the code selection circuit 16 and the view data input circuit 18. to select one of the formats of message information. When a normal picture channel is selected and its associated broadcast video signal is received, a "picture on" signal PO originating from user control 35 places switch 25 in the state shown in the drawings in which contact 28 engages terminal 26. ,
The incoming video signal VS is supplied to the synchronization separation circuit 11. Therefore, the separated synchronization signal is sent to the time base circuit 1.
Used to control 0.

When teletext or view data message information is selected, signal PO ends and switch 2
5 is in a state where the contact 28 is engaged with the terminal 27, and the locally generated synchronization signal from the pulse generator 31 is supplied to the synchronization separation circuit 11. Therefore, a locally generated synchronization signal is used to control the time base circuit 10. These two
In each of the two cases, the operation of the time base circuit 10 is synchronized with the incoming video signal, this synchronization being done directly in the first case and using the oscillator 29 in the second case.
This is done because the signal is phase-locked to the incoming video signal VS.

If the signal quality becomes unacceptable or there is no incoming video signal, the signal quality circuit 23
The phase lock of the oscillator 29 is released by the inhibition signal IS from the oscillator 29, causing the oscillator to run freely, and also prohibiting the vertical synchronization pulse from being supplied to the synchronization pulse generator 31. Therefore, although the locally generated synchronization signal is still occurring, it is not synchronized with any incoming video signal. Of course, in the presence of a video signal, the inhibit signal IS inhibits the operation of the data receiving gate 14 and prevents the reception and storage of encoded data pulses with unacceptable noise.

A variant is to use a locally generated synchronization signal instead of selecting a separate synchronization signal when the "image on" signal is present and the signal quality becomes sufficiently poor to cause an inhibit signal IS. It is also possible to control the switch 25 by the inhibition signal IS so as to select . By doing so, pre-stored data such as channel information that can be generated by the control device 35 can be clearly superimposed and displayed on the display image.

[Brief explanation of the drawing]

The drawing is a block diagram showing an example of a character television transmission apparatus having a television reception apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1... Input conductor, 2... Input circuit, 3... Television transmitter, 4... Transmission line, 5... Selection circuit, 6... Selection switch, 7... Color decoder, 8... Video interface circuit, 9... Picture tube, 10 ...Time axis circuit, 11...Synchronization separation circuit, 12...Data extraction circuit, 13...Data clock pulse generator, 14...
Data reception gate, 15...Data acquisition circuit, 16
...Sign selection circuit, 17...Data storage device, 18...
View data input circuit, 19...Telephone line, 20...Character generator, 21...Parallel-serial converter, 22
...Color coder, 23...Signal quality circuit, 24...Synchronization pulse separator, 25...Electronic switch, 29...Phase lock oscillator, 30...Timing circuit, 31...
Synchronous pulse generator, 33...gate, 35...user control device.

Claims (1)

Claims: 1. Encoded data pulses representing alphanumeric text or other message information in a video signal in at least one television scan line during a vertical blanking interval in which no normal image information is present. This is a television reception device suitable for use in a character television transmission system that transmits a video signal, and includes a data selection and acquisition device that selectively extracts encoded data pulses from a received video signal, and a data selection and acquisition device that selectively extracts encoded data pulses from a received video signal. a data storage device for storing pulses and generating from said stored encoded data pulses a video signal that can be used to display on a television screen the particular message information represented by said stored encoded data pulses; In a television reception apparatus comprising a decoding device for determining the time axis of the display device and an oscillation device for generating a synchronization signal which is generated locally within the television reception device itself and which can be used for the television display. a switching circuit for coupling the input terminal of the synchronizing signal separation circuit of the circuit to the video signal output terminal of the front stage of the television receiver or to the output terminal of the oscillation device; can be synchronized by the output of another sync signal separation circuit via a phase lock loop, and the input terminal of this other sync signal separation circuit is coupled to the video signal output terminal of the preceding stage, and the 1. A television receiver characterized in that the phase lock loop is disabled by a signal quality detection circuit that detects that the signal quality of the video signal is unacceptable or that the video signal is not present. 2. In the television receiver apparatus according to claim 1, the switching signal input terminal of the switching circuit is coupled to the output terminal of the signal quality detection circuit, and the signal quality of the video signal is unacceptable. 1. A television reception apparatus, characterized in that it uses a locally generated synchronization signal in the absence of a video signal. 3. A television image receiving apparatus according to claim 1 or 2, characterized in that it is provided with a television display device.