JPH0218794B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a television for transmitting character information that transmits code data pulses representing alphanumeric information in line periods in which there is no image signal representing normal image information in a television signal. The present invention relates to a television receiver of a type hereinafter referred to as a specific type suitable for use in a transmission system.

(Prior Art) Regarding the above-mentioned television transmission system for transmitting character information, so-called full channel operation is also possible in which the entire line period of each field in the television signal is used for transmitting code data pulses.

However, in the current television transmission system for transmitting character information, only the line period of the vertical erasing period is used for transmitting code data pulses, so in reality, such character information transmission is not equivalent to normal image transmission. It is done multiple times. The alphanumeric information transmitted by such a transmission system can be displayed in selectable replacement with conventional image information through the use of a suitable television receiver capable of extracting encoded data pulses from the television signal. Note that this type of television transmission system for transmitting character information can use either a radio broadcasting system or a cable transmission system as its transmission medium.

This type of television transmission system for transmitting character information is
It is described in British Patent No. 1370535.
In addition, the Broadcast Teletext Broadcasting Specification, jointly published by the British Broadcasting Corporation, the Independent Broadcasting Corporation and the Radio Equipment Industry Association, is also available.
Specification), published in September 1976, contains detailed specifications for this type of character information transmission system.

According to the above-mentioned teletext broadcast specifications, the amount of information that should be displayed all at once on a television screen is called a page, so it will also be referred to as a page hereafter. Therefore, all information pages to be displayed and used are sequentially and repeatedly transmitted, regardless of whether or not the most recent information page is displayed. In a television receiver dedicated to such text information transmission, the viewer can specify any information page to be displayed, and the specified information page is extracted the next time it is repeatedly transmitted. It is stored in the display memory until it is replaced with the next extracted information page.

Such specific types of television receivers include:
A data selection and extraction means for selectively extracting coded data pulses from a received television signal, a memory for storing the extracted coded data pulses, and a video signal that can be used to display information represented by the stored coded data pulses. A decoding means is included for generating from the stored encoded data pulses.
Such a television receiver includes appropriate television display means and can also supply a video signal for displaying text information to other television receivers.

For this type of television receiver, code data pulses contained in the received television signal containing noise with a height exceeding a predetermined threshold are
It has been desired in the past to further include a signal quality evaluation device configured to operate to inhibit the extraction of code data pulses for storage. The purpose of such a signal quality evaluation device is to minimize the extraction for storage of so-called noise-contaminated code data pulses that tend to display difficult-to-understand information, and furthermore, it The purpose is to prevent the code data pulses representing the information contained therein from being adversely affected by such noise-contaminated code data pulses. This disadvantageous effect is caused by the fact that in this type of television receiving device, when a certain page is selected, code data pulses of that page are extracted and stored anew each time it is repeatedly transmitted, and the code data pulses of that page are extracted and stored anew each time it is transmitted. This can actually happen, since it operates to completely rewrite conceptually identical code data pulses that have been extracted and stored at times.

British Patent No. 1568184 discloses a conventional signal quality evaluation device for determining the signal quality of a received television signal. This conventional signal quality evaluation device combines the heights of a line periodic pulse generated within a receiving device and a corresponding line periodic pulse separated from a received television signal, and calculates the combined pulse height for a specific line periodic pulse. It performs its function by generating an output voltage by integrating it over a period, and when the output voltage reaches a threshold value, it generates an inhibit signal that prevents the extraction of code data pulses.

(Problems with the Prior Art) According to the conventional signal quality evaluation device described above, good performance can be obtained if the specified line period is constant for any arbitrary television transmission system. However, in designing a specific type of television receiver for selective use in a number of different television transmission systems, it is important to consider the pulse width of the line period pulses, which is adapted to a good quality television signal. It is known that the conventional signal quality evaluation apparatus described above becomes unusable depending on the range of the signal quality.

(Object of the Invention) An object of the present invention is to provide a signal quality evaluation device with another structure that is improved so as not to be subject to such usage restrictions.

(Structure of the Invention) According to the present invention, a signal quality evaluation device configured to operate so as to prohibit extraction of code data pulses included in a received television signal containing noise higher than a predetermined threshold for storage purposes. a separator for separating line period Hals, field synchronization pulses and equalization pulses from the received television signal; The type described above is provided with a counting circuit that counts the number of pulses, and a prohibition circuit that receives the pulse count value and generates a prohibition pulse that prohibits the extraction of code data pulses when the pulse count value exceeds a predetermined value. A television receiving device is provided.

The present invention is based on the recognition that when a noisy television signal is received, false signal pulses are introduced into the pulse signal waveform separated from the television signal. The number of such false signal pulses is related to the degree of noise contamination, and therefore means can be provided to reliably indicate whether the received television signal is suitable or not, depending on the number.

In carrying out the present invention described above, the predetermined period described above is made to correspond to a large number of line periods, and the number of pulses described above in each of those line periods is counted to calculate the predetermined number for each line period. means for determining that a received television signal with a corresponding line period is inappropriate because it contains pulses exceeding the number of line periods, and further means for counting the number of inappropriate line periods that occur among the large number of line periods mentioned above. may be provided, and the above-mentioned prohibition signal may be generated when the number of unsuitable line periods exceeds a predetermined value. Note that the above-mentioned predetermined period is preferably one field cycle.

The signal quality evaluation device according to the present invention further includes counting the number of line periods in which no pulse appears during the predetermined period mentioned above, and when the number of line periods exceeds a predetermined value, the above-mentioned prohibition signal is sent. can include means for generating. Note that, as will be described later, such a line period can also be considered to be included in the inappropriate line period.

Further, the signal quality evaluation device according to the present invention is provided with an integrating means, and the situation is evaluated until the received television signal of each line period in a sequential predetermined period is determined to be either suitable or unsuitable. It is also possible to leave it as is and prevent the above-mentioned prohibition signal from being generated or stopped.

The present invention also provides for selectively inhibiting the extraction of code data pulses included in a line period in which no image signal representing normal image information of a television signal exists in a television receiving device.
A pulse signal waveform containing only line period, field synchronization, and equalization pulses as present in the received television signal is formed from the received television signal, and a pulse that appears in the pulse signal waveform for each line period. determine when the number of pulses exceeds a predetermined number, and count the number of line periods containing pulses exceeding the predetermined number for each field period,
A selective inhibition method is also provided, which detects when the count value reaches a predetermined value, and further prohibits the extraction of code data pulses when the detection is performed for a predetermined number of consecutive field periods. This is what we provide.

(Example) The present invention will be described in detail below with reference to the drawings.

The illustrated television transmission system is a television image formed from image information represented by a normal radio broadcast or cable television video signal, or coded data pulses that are multiplexed and transmitted during the vertical or field erasing period of the video signal. The company has a composite television receiver that selectively displays teletext information such as alphanumeric information.

Note that it is also possible to display teletext information simultaneously with the television image, such as subtitles and headlines superimposed on the television image.
It is also possible to adapt so-called full-channel operation.

As schematically shown in Fig. 1, this transmission system includes a television transmitter TT and a television receiver suitable for receiving a television video signal VS via a normal radio broadcast or cable transmission link TL. We are prepared. The transmitter TT includes means for forming a television video signal in a well-known manner;
A means for forming teletext information such as alphanumeric information and a means for forming a television video signal VS containing an image signal representing image information and a coded data pulse representing teletext information using the normal synchronization necessary for the operation of the television receiving device. and means for generating with each pulse of equalization. on the other hand,
The television receiver TR includes conventional amplification, tuning, and intermediate frequency detection front-stage circuits, as well as video and data processing circuits, which will be described below with reference to FIG.

The composite television receiver shown in FIG. 2 has a front section FE connected to receive an input television video signal. To display a normal image in this television receiver, the demodulated video signal VS' is supplied to a color decoder CD which forms R, G, and B component signals for image display. The time axis scanning circuit for the display tube DT uses the demodulated video signal.
Each sync pulse is received from a sync separator circuit which extracts the normal line period and field sync pulses from VS'. Component CD represents a color decoder and other circuit elements provided for normal image display.

The demodulated video signal VS' is also supplied via the selection circuit SL to another circuit section in the television receiving device which processes the display of teletext information, such as alphanumeric information received in the form of digital codes. Ru. This circuit section is provided with a video processing circuit VP which mainly performs slicing at an appropriate threshold level of data pulses for shaping and extracting code data pulses D from the demodulated video signal VS'.
The code data pulse D, together with the clock pulse C, is supplied to a data extraction circuit DAC operable to supply a selected group of data pulses D/G from among the code data pulses to the memory MEM as address and display information. This memory MEM
has a capacity to store at least one page worth of character information. The logic processing circuit PRO may operate to control which data pulse group of the code data pulses is extracted by the data extraction circuit DAC in response to a selection signal S supplied by the remote control device RC. Meanwhile remote control device RC
has a receiving circuit part RR and a remote transmitting circuit part with a transmitter TX and a keypad KP. Furthermore, the logic processing circuit PRO reads display character information of the selected page from the memory MEM and supplies it to the character signal generator CG which stores R, G, and B component signals for display. Operate. The timing circuit TC includes each circuit element DAC,
Connection line t1 corresponding to MEM and CG respectively
It supplies a timing signal from t3 to t3. In addition, those circuit elements DAC, MEM, CG
and timing circuit TC are accessed by logic processing circuit PRO via interface circuit INT. In addition, the operation of the timing circuit TC is based on the demodulated video signal in the video processing circuit VP.
It is synchronized with the received video signal VS' by a composite pulse signal VCS including line synchronization, field synchronization, and equalization pulses separated from VS'.

In the television receiver shown in FIG. 2, only a single interconnection line between the various circuit elements is shown for simplicity. However, it will be apparent to those skilled in the art that in reality, many of these interconnections consist of a large number of connecting wires. For example, the code data pulse D separated and shaped from the demodulated video signal VS' is supplied to the data extraction circuit DAC in series via a single connection line, whereas in this data extraction circuit DAC, the code data pulse D is Since the conversion takes place,
Each group of code data pulses D/G is supplied in parallel to the memory MEM via a number of connecting lines. In addition, logic processing circuit PRO and interface circuit
The connection between the INT and the INT also includes multiple connection lines, e.g.
For example, it depends on the I ² C bus. The logic processing circuit PRO is a commercially available microcomputer, for example,
It can be a Philips MAB8400 type microcomputer. The composite television receiver is constructed as shown in FIG. 2, but the data extraction section provided with the front stage FE is a separate unit that can be combined with a television display monitor or a normal television receiver. It can also be provided as a teletext decoder.

The signal quality evaluation device shown in FIG.
It forms part of the timing circuit TC. This signal quality evaluation device includes an "edge" counter EC, an "inappropriate line period" counter BL, a "non-pulse line period" counter ZL, two decoding latch circuits DL1 and DL2,
OR gate OG, "field" counter FC, "signal quality" flag latch SQL, and line period and field period signal generator LSG and
Equipped with FSG. A composite pulse signal VCS is supplied to the clock input terminal CK of the edge counter EC, and an idealized signal waveform of this composite pulse signal VCS is shown in FIG. This signal waveform is the scanning line
It shows the generation status of each pulse LP, FP, and EP for line synchronization, field synchronization, and equalization in the 625-line standard television system.
Each repetition period of LP, FP and EP is also the line period.
It is shown in Figure 4 with a time of 64 microseconds.

The noisy demodulated video signal VS′ is processed by the video processing circuit.
Upon entering the input terminal of the VP, spurious signal pulses are introduced into the composite pulse signal VCS, the number of which is related to the degree of noise contamination. In the actual operation of the video processing circuit VP,
It is conventionally known that such false signal pulses appear relatively frequently in the field synchronization pulse and equalization pulse regions due to the automatic gain control function provided in the video processing circuit VP. The signal quality evaluation device operates to determine signal quality by counting the number of pulses that occur during a period of time. Note that the time length of the period is preferably made to correspond to the line period.

Considering the operation of this signal quality evaluation device, the edge counter EC counts the number of rising edges of each pulse appearing in the composite pulse signal VCS applied to the clock input terminal CK. This edge counter EC is reset every line period by a signal LSs supplied from the line period signal generator LSG to the reset input terminal RS. Furthermore, as can be seen from Figure 4, if noise is not mixed into the composite pulse signal VCS, only one rising edge will be counted for most line periods, and each pulse FP and EP for field synchronization and equalization will be counted. In the appearing line period, only two rising edges are counted. Therefore, when three or more rising edges are counted in one line period, the edge counter EC, which is preferably a 2-bit counter, is
By outputting an active logic level at the output of ``3'', the signal for that line period is declared invalid. The unsuitable line period counter BL is then enabled by its active logic level output until it is reset by the signal FSs applied from the signal generator FSG to the reset input terminal RS at the end of the field period. Count each unsuitable line period.

The count value created by this unsuitable line period counter BL is calculated by the two decoding latch circuits DL1 and DL.
2 and decoded. Only one of these decoding latch circuits DL1 and DL2 is always activated according to the determination of the supplied selection signal SEL. For example, when the selection signal SEL exhibits a high logic level, the decoding latch circuit DL2 is activated. is in the enabled state. The operating conditions are as follows:
Signal quality flag formed by latch SQL
SQF is also established when the received signal exhibits a high logic level meaning it is suitable. Further, when the selection signal SEL exhibits a low logic level, the decoding latch circuit DL1 is enabled via the inverter INV. This latter operating condition is met when the signal quality flag SQF mentioned above also exhibits a low logic level, meaning that the received signal is unsuitable. In addition, the data extraction circuit DAC shown in the second figure
is prohibited from extracting data when this signal quality flag SQF is at a low logic level, which means that the received signal is unsuitable.

On the other hand, the non-pulse line period counter ZC accidentally generates inappropriate data when the oscillator that extracts the synchronization pulse generated on the receiving side loses phase lock with the input video signal and free-runs in the video processing circuit VP. This is provided to protect the reception from being detected. Note that the synchronization pulses generated on the receiving side are used to display data that has already been received and stored by the television receiver. The above-mentioned free running state of the oscillator may occur because the external television signal is not being received, or because the external television signal being received is contaminated with noise and a prohibition signal that prohibits data reception has already been generated. It is something that arises because of the existence of In such a case, it is known that edges are not detected over a period of several line periods. A line period with no pulses indicates no input and therefore indicates inadequate signal quality, but if the local oscillator free-runs too fast, it will not be possible to feed the signal quality detector. Since the timing of the line period is shorter than 64 microseconds, a blank line period will obviously occur. In addition, until 31 such blank line periods occur per field period,
It is preferable not to declare the field period as inappropriate, which ensures that
A signal with suitable signal quality can be detected even if the oscillation frequency of the local oscillator is increased by 5%.
Additionally, in this case, the hysteresis created in the signal quality evaluation device controls the switching between the phase lock operation and the free running operation of the local oscillator, and the "jump" that would occur on the display screen in the absence of hysteresis is also controlled. ” and “jitter” are substantially reduced.

(Effects of the Invention) As is clear from the above description, according to the present invention, character information data pulses that are multiplexed and transmitted on television signals of various standard formats can be appropriately transmitted regardless of the standard format. A special effect can be obtained in which deterioration due to noise incorporation can be eliminated through evaluation, and only high-quality character information can be received, extracted, and displayed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a television transmission system for character information, FIG. 2 is a block diagram showing an example of the configuration of a television receiver in the above-mentioned type of transmission system, and FIG. FIG. 4 is a block diagram showing an example of the configuration of a signal quality evaluation device. FIG. 4 is a signal waveform diagram showing an example of an ideal pulse signal waveform. TT...television transmitter, TR...television receiver, TL...link, FE...previous section, SL...selection circuit, CD...color decoder, DT...
…display tube, VP…video processing circuit, CG…character generator, DAC…data extraction circuit, MEM…memory, TC…timing circuit, INT…interface circuit, PRO…logic processing circuit, RC...
Remote control device, RR...Reception tuning section, TX...Transmitter, KP...Keypad, EC...Edge counter, BL...Unsuitable line period counter, DL1, DL2
...Decoding latch circuit, LSG, FSG...Signal generator, ZL...Pulse line period counter, OG...OR gate, FC...Field counter, FSL...
...Signal quality flag latch, VS...Television video signal, VS'...Demodulated video signal, VCS...Decoded pulse signal, S, SEL...Selection signal, SQF...
...Signal quality flag, D...Code data pulse, C
...Clock pulse, D/G...Data pulse group, R, G, B...Color component signal, LSs, FSs...
Signal, EP...Equivalent pulse, FP...Field synchronization pulse, LP...Line synchronization pulse.

Claims (1)

[Scope of Claims] 1. Suitable for use in a television transmission system for character information that transmits code data pulses representing alphanumeric information in line periods in which there is no image signal representing normal image information in a television signal; ,
Data selection and extraction means for selectively extracting coded data pulses from a received television signal, a memory for storing the extracted coded data pulses, and storage of video signals that can be used to display information represented by the stored coded data pulses. and a signal quality evaluation device configured to operate so as to prohibit extraction for storage of code data pulses contained in a received television signal containing noise higher than a predetermined threshold. In the television signal receiving device, the signal quality evaluation device receives a line synchronization pulse from the received television signal,
a separator for separating the field synchronization pulse and equalization pulse; a counting circuit for accepting each of the separated pulses and counting the number of pulses appearing within a predetermined period; 1. A television receiver comprising an inhibiting circuit that generates an inhibiting pulse that inhibits extraction of code data pulses when a numerical value exceeds a predetermined value. 2. In the receiving device according to claim 1, the predetermined period corresponds to a large number of line periods, and the number of pulses in each of the line periods is counted to calculate the predetermined number for each line period. means for determining that a received television signal with a corresponding line period is inappropriate because it contains a number of pulses exceeding the number of line periods; 1. A television receiving apparatus, characterized in that the prohibition signal is generated when the number of unsuitable line periods exceeds a predetermined value. 3. The television receiving apparatus according to claim 2, wherein the predetermined period is one field period. 4. Claims: The receiving device according to any one of the above claims, which counts the number of line periods in which no pulse appears during the predetermined period, and
A television receiver comprising means for generating the inhibition signal when the number of line periods exceeds a predetermined value.