JPS61101184A - Television receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 all-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 of this type, 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 is
Through the use of suitable television receiving equipment capable of extracting encoded data pulses from the television signal, they can be displayed in selectable replacement with normal image information.

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.

A television transmission system of this type for transmitting text information is described in British Patent No. 1.370.535. In addition, the ``Broadcast Teletext 5pec Specification'', which is jointly published by the British Broadcasting Corporation, the Independent Broadcasting Corporation, and the Radio Equipment Industry Association, is also available.
ification) J Published in September 1976,
Details of the specifications of this type of character information transmission system are described.

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 hereafter as a page. 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 receiving device dedicated to the transmission of text information, the viewer can specify any information page to be displayed, and the specified information page will be extracted the next time it is repeatedly transmitted. The information page is then stored in the display memory until it is replaced with the next extracted information page.

Such a specific type of television receiving device includes data selection and extraction means for selectively extracting coded data pulses from the received television signal, a memory for storing the extracted coded data pulses, and information representing the stored coded data pulses. Decoding means are included for forming a video signal from the layered encoded data pulses that can be used for display.

Such a television receiver includes an appropriate television display means, and can also supply a video signal for displaying text information to another television receiver.

For this type of television receiving device (Y), code data pulses contained in a received television signal containing noise with a height exceeding a predetermined threshold are prohibited from being extracted in order to store the code data pulses. It has long been desired to further include a signal quality evaluation device configured to operate to The purpose is to minimize the extraction of information for the purpose of the present invention, and furthermore to prevent already accumulated code data pulses representing information suitable for intelligible display from being adversely affected by such noise-contaminated code data pulses. This disadvantageous effect is due to the fact that television receivers of this type typically, once a page is selected, extract the coded data pulses of that page each time it is transmitted, and generate a new one. accumulated,
This can actually happen because the operation is such that the conceptually identical code data pulses that were extracted and stored during the previous transmission are completely rewritten.

British Patent No. 1,568,184 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 sync pulse generated within the receiver and a corresponding line sync pulse separated from the received television signal, and calculates the combined pulse height for a specific line. Its function is to generate an output voltage by integrating it over a period, and when the output voltage reaches a threshold, it generates an inhibit signal that prevents the extraction of code data pulses.

(Problems with 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, the pulse width of the line sync pulse must be adjusted to match the quality of the 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, the signal quality evaluation is configured to operate such that code data pulses included in a received television signal containing noise higher than a predetermined threshold are prohibited from being extracted for storage. In response to a received television signal, the signal quality evaluation device determines a pulse signal waveform containing only line synchronization, field synchronization, and equalization pulses as present in the received television signal. separation means for forming a code data pulse; means for counting the number of pulses appearing in the pulse signal waveform in a predetermined period; and means for generating a prohibition signal for prohibiting the extraction of code data pulses when the number of pulses exceeds a predetermined value. A particular type of television receiving device is provided which is provided with means.

The invention was 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 side signal pulses is related to the degree of noise contamination, and therefore, depending on the number, means can be provided to reliably indicate whether the received television signal is appropriate or inappropriate.

In carrying out the 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 ensure that the number of pulses in each line period exceeds the predetermined number. means for determining that a received television signal of a corresponding line period is unreachable based on the number of pulses contained in the line period; The above-mentioned prohibition signal can be generated when the number of unsuitable line periods exceeds a predetermined value. NaJ'3
It is preferable that the above-mentioned predetermined period is one field period.

When the above-mentioned prohibition signal is already generated, the number of unsuitable line periods is allowed to reach a certain value, and when the above-mentioned prohibition signal is not generated, the number of unsuitable line periods is prevented from reaching a large value. By doing so,
Hysteresis can be implemented in the signal quality evaluation device described above.

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 a method 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. Form a pulse signal waveform containing only line synchronization, field synchronization, and equalization pulses as present in the received television signal from the signal, and calculate the number of pulses appearing in the pulse signal waveform for each line period. Determine whether the predetermined number has been exceeded, count the number of line periods that include pulses exceeding the predetermined number for each field period, detect when the counted value has reached the predetermined value, and A selective inhibition method is also provided in which extraction of code data pulses is inhibited when detection has occurred for a predetermined number of consecutive field periods.

(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. It has a composite television receiver that selectively displays teletext information such as alphanumeric information.

Furthermore, it is also possible to display teletext information at the same time as the television image, such as subtitles and headlines added to the television image. It can also be adapted to channel operation.

As schematically shown in FIG. 1, this transmission system includes a television transmitter tiTT and a television receiver suitable for receiving a television video signal vS via a normal radio broadcast or cable transmission link TL. There is C. The transmitter TT is equipped, in a known manner, with means for forming television video signals, means J5 for forming teletext information such as alphanumeric information, and for displaying image signals representing image information and teletext information. The television video signal ■S containing the WAZ code data pulse is sent to #I of the television receiving device.
It includes means for generating along with the normal synchronization and equalization pulses required by the IPF. On the other hand, the television receiver TR uses normal amplification and tuning.

Each pre-stage circuit for intermediate frequency detection is illustrated in conjunction with the video and data processing circuits described below with reference to FIG.

The composite television receiver shown in FIG. 2 has a face section FE connected to receive an input television video signal. In order to display a normal image in this television receiver, a color decoder C converts the decoded video signal vS- into R, G, and 8 component signals for image display.
Supply to D.

The time axis scanning circuit for the display tube DT receives the demodulated video signal vS-
Each synchronization pulse is received from a synchronization separator circuit which extracts the normal line interval and field synchronization pulses from the synchronization circuit. Component CD represents a color decoder and other circuit elements provided for normal image display.

The demodulated video signal VS- also passes through the selection circuit SL,
In the television receiver, it is supplied to further circuitry for processing the display of teletext information, such as alphanumeric information, received in the form of digital codes. This circuit section is provided with a video processing circuit VP which mainly performs data pulse shearing for shaping and extracting code data pulses D from the demodulated video signal vS-. The code data pulse D is supplied together with a clock pulse C 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 ME
M has each machine capable of storing at least one page's worth of character information.

The logic processing circuit PRO can operate to control which data pulse group among 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 RC7Jl. On the other hand, remote control 13I
The device RC has a receiving circuit part RR and a remote transmitting circuit part with a transmitter 11TX and a keypad KP. The logic processing circuit PRQ roughly displays R, G,
In order to supply the B component signal to the character generator CG, the display character information of the selected page is stored in the memory M.
It can operate without reading from E'Vl. The timing circuit TC supplies timing signals to connection lines tl to t3 corresponding to the respective circuit elements DAC, MEM, and CG. In addition, those circuit parts; +: D A
C, ~IFM, CG and timing circuit TO are interface circuit (through NT, logic '2!1]
l! Accessed by one circuit PRO. Further, the operation of the timing circuit TC is based on the line interval 1 separated from the demodulated video 1g signal VS- in the video processing circuit VP.

A composite pulse signal including field synchronization and equalization pulses is synchronized to the received video signal vS' by VCS.

In the television receiver shown in FIG. 2, only a single connection line is shown for interconnection between various circuit elements for simplicity; however, in reality, these It will be apparent to those skilled in the art that many of the interconnects in the circuit consist of multiple connecting wires. For example, the code data pulse D separated and shaped from the demodulated video signal VS- is serially connected to the data extraction circuit DAC via a single connection line.
1,: For the supplied data extraction circuit DAC
Since serial-to-parallel conversion is performed within C, each group of code data pulses D, /G is supplied to the memory MEM in parallel via a large number of connecting lines. Further, the connection between the logic processing circuit PRO and the interface circuit rNT is also made by a large number of connection lines, for example, a 2C bus. The logic processing circuit PRO is a commercially available microcomputer, for example, Philips' AMA
38400 type microcomputer. The composite television receiving apparatus is constructed as shown in FIG. 2, and the data extracting section provided together with the front stage FE is combined with a television display monitor or a normal television receiver. The C72 can also be provided as a separate teletext decoder.

The signal quality evaluation device shown in FIG. 3 conveniently forms part of the timing circuit TC. This signal quality evaluation 1-track device includes an "edge" counter EC1, an "inappropriate line period" counter BL, a "non-pulse line period" counter ZL, and 21f! il
decoding latch circuits DL1 and DL2, an OR gate OG, a "field" counter FC1, a "signal quality" flag latch SQL, and signal generators SG and FSG for the line layer till J5 and the field period. A composite pulse signal VC8 is supplied to the clock input terminal CK of the edge counter EC, and an idealized signal waveform of this composite pulse signal VC8 is shown in FIG. This signal waveform corresponds to the line interval, field synchronization, and equalization pulses LP in the standard television system (@625$).
, FP, and B show the generation states of σEP, and the repetition period of each of these pulses LP, FP, and EP is also shown in FIG. 4 with the linear period set to 64 microseconds.

When the noisy demodulated video signal vS- enters the input terminal of the video processing circuit vP, false signal pulses are introduced into the composite pulse signal vC8, but the number of false one-word pulses depends on the degree of noise contamination. related to. In the actual operation of the video processing circuit VP, such signal pulses appear relatively frequently in the region of field synchronization pulses and equalization pulses due to the automatic gain control T1m function provided in the video processing circuit VI''. is conventionally known. This signal quality evaluation device operates to determine the signal quality by counting the number of pulses generated during a certain time period.The time length of the period is It is preferable to correspond to the linear phase.

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 VC8 supplied to the clock input terminal CK. This edge counter EC is reset for each line period by a signal LSs supplied from the line period signal generator 'aLSG to the reset input terminal R8. Moreover, as can be seen from FIG. 4, if noise is not mixed in the composite pulse signal vC8, only one rising edge is counted for every line period, and each pulse FP and pulse for field synchronization and equalization are counted. In the linear phase when EP appears, only two rises and two rises are counted. Therefore, when three or more rising edges are counted in one line period, the edge counter EC, preferably a 2-bit counter, outputs an active logic level at its output for r>3J. Declare signals in the stratum phase to be unsuitable. The unsuitable line period counter BL is then enabled by its active logic level output, so that the unqualified line period counter BL remains in the unsuitable line period until reset by the signal FSs supplied from the signal generator FSG to the reset input terminal R8 at the end of the field period. Count each layer of light.

The count value created by this unsuitable line period counter BL is supplied to two decoding latch circuits DL1 and DL2 and decoded. These decoding launch circuits DLi, DL
According to the determination of the supplied selection signal SEL, only one of the decoding latch circuits DL2 is always activated. For example, when the selection signal SEL has a high logic level, the decoding latch circuit DL2 is enabled. Note that this operating condition is satisfied when the signal quality flag SQF formed by the latch SQL also exhibits a high logic level, meaning that the received signal is suitable. In addition, the selection signal SE
When L exhibits a low logic level, inverter INV
The decoding latch circuit DL1 is enabled via the decoding latch circuit DL1. This latter operating condition is met when the aforementioned signal quality flag SQF also exhibits a low logic level, meaning that the received signal is unsuitable. This signal quality flag S
It is assumed that QF acts as a J-type selection signal SEL in J3 in the simplified functional configuration example of FIG. Further, the data extraction circuit DAC shown in FIG. 2 is prohibited from extracting data when the signal quality flag SQF is at a low logic level indicating that the received signal is unsuitable.

Next, when N or more unsuitable line periods occur in one field period, that field period is declared to be unsuitable. Note that the yield period (targeted for evaluation) is determined by the effect that each pulse of field synchronization and equalization has on the automatic IH control function in the image processing circuit VP, and the area of those pulses. What is the tendency for false signal pulses to occur? 4 Select L, L<. Further, in detecting signal quality, hysteresis is introduced by using various different values for the above-mentioned N.

In the illustrated embodiment, when the signal quality flag SQF is currently set to indicate unsuitable, the latch DL+ is enabled with \=3; When set to represent \-15, latch D
The L2 is enabled.

If the signal quality flag SQF is set to indicate OK at the beginning of the operation overrun, then the latch DL2 is enabled. Furthermore, if the data reception is actually valid, the edge counter EC does not enable the unsuitable line period counter BL, so the unsuitable line period counter BL does not count at that time.

Therefore, latch DL2 in the enabled state, as well as latch DL1, is connected to the clock gate OR.
Field counter FC up/down/
A low logic level will be input to the enable input terminal, so that the field counter FC will count up by 1 for each field when the signal FSs is applied to the clock input terminal CK at the end of each field period. . By the way, the field counter FC consists of a 2-bit counter. Therefore, after counting up to three unsuitable fields and making the signal quality suitable, the high logic level appearing at the output terminal TCU is transferred to the signal quality flag latch SQL. C sets the recent signal quality flag SQF appropriately by supplying it to the set input terminal S of C. Furthermore, when data reception becomes inappropriate, the edge counter EC enables the unsuitable line period counter BL for the corresponding line period. Count each time. Further, when the count value of the unsuitable line period counter BL reaches 15 in one field period, the latch circuit DL2 is latched and inputs a high logic level to the field counter FC. F
'C resets the signal quality flag latch SQI by generating a high logic level on its output terminal TCD and applying the high logic level to its reset input terminal R;
Therefore, the active level of the signal quality flag SQF is changed to mean that data reception is inappropriate.

At that time, the latch DL1 is in the enabled state, so that the signal quality flag SQF remains in a state meaning that data reception is unsuitable due to this active logic level, and for at least three This results in an unsuitable line period of . In addition, due to the hysteresis effect of the two latches DL1t and DL2,
The field counter FC performs Arab output counting of the data signals of three successive fields that are obtained with only three or less unsuitable line periods for each field, and sets the signal quality flag latch SQL.

The signal quality flag SQF is changed from a low logic level to a high logic level, and data reception is received by the time a signal that data reception becomes suitable again is sent out.

On the other hand, the non-pulse line period counter ZC is connected to the video processing circuit V.
In P, the oscillator that extracts the synchronization pulse generated on the receiving side loses its phase lock with the input video signal and is installed to prevent incorrect data reception from being mistakenly detected when free running occurs. be. 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. However, the free running state of the oscillator described above may be due to the fact that the external television signal is not being received, or the external television signal being received is contaminated with noise and the prohibition signal for prohibiting data reception 5 is already present. This occurs because it is occurring. In such a case, it is known that edges are not detected over the period of number line brightness. A line phase in which there are no pulses at all indicates no input and therefore indicates inadequate signal quality, but if the local oscillator free-runs too fast, the line feeding the signal quality detector Since the timing of the layer phase opens by M from 64 microseconds, an obviously blank line layer phase will occur.

Note that the antenna frequency is 3 per field period.
It is preferable not to declare a field period as bad until one occurs, which ensures that a signal of good signal quality will have a local oscillator oscillation frequency that is only 5% higher. It will also be detected.

Additionally, in this case, the hysteresis generated in the signal quality evaluation device restricts the local oscillator's switching between phase-locked operation and free-running operation, and the " Jump” and “
"Jitter" is substantially reduced.

(Effects of the Invention) As is clear from the above description, according to the present invention, text information data pulses that are multiplexed and transmitted on various previous sub-I format television signals can be transmitted efficiently (regardless of the V format). properly evaluate and eliminate deterioration due to noise contamination.
A special effect can be obtained in that only high-quality text 1 hour 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 text 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 signal waveform diagram showing an example of an ideal pulse signal waveform. TT...Television transmission separate TR...Television receiving device TL...Link FE...Front stage SL...
Selection circuit CD...Color decoder DT...Display tube
VP...Video @ Jinri circuit CG...Character generator
DAC...Data extraction circuit MEM...Memory
TC...Timing circuit INT...Interface circuit P RO...Logic processing circuit RC...Remote control device RR...Reception tuning unit TX.
・・Transmission K'P・Keypad EC・・
Edge counter BL...Unsuitable line period counter DLI, DL2...Decoding latch circuit LSG, FSG...Signal generator 71...No pulse line period counter OG...OR gate FC...Field counter FSL・... Signal quality flag latch vS ... Television video signal VS - ... Demodulated video signal VO8 ... 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... Interline Pulse Patent Applicant: N.B.Philips Fluiranpenfabriken

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. a data selection and extraction means for selectively extracting code data pulses from the received television signal; a memory for storing the extracted code data pulses;
decoding means for creating a video signal from the stored coded data pulses that can be used to display information represented by the stored coded data pulses; and coded data pulses contained in the received television signal containing noise above a predetermined threshold. is a television signal receiving device equipped with a signal quality evaluation device configured to operate so as to prohibit extraction for storage, the signal quality evaluation device is configured to determine whether the received television signal separation means for forming a pulse signal waveform containing only line synchronization, field synchronization and equalization pulses as present in the signal;
The present invention is characterized by comprising means for counting the number of pulses appearing in the pulse signal waveform during a predetermined period, and means for generating a prohibition signal for prohibiting the extraction of code data pulses when the number of pulses exceeds a predetermined value. television receiving device. 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 assign a predetermined number to 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, and further comprising means for counting the number of inappropriate line periods that occur among the large 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 cycle. 4. In the receiving device according to claim 2, by including a hysteresis means in the signal quality evaluation device, the number of unsuitable line periods reaches a certain value when the prohibition signal is already generated. 2. A television receiving apparatus according to claim 1, wherein the number of unsuitable line periods is allowed to reach a large value when the prohibition signal is not generated. 5. Scope of Claims In the image receiving device according to any of the above items, the number of line periods in which no pulse appears at all during the predetermined period is counted, and when the number of line periods exceeds a predetermined value, A television receiving device comprising means for generating the inhibition signal. 6. In the receiving device according to any one of claims 2 to 5, the reception television signal of each line period in the predetermined period is determined to be appropriate or inappropriate, respectively. 1. A television receiving device comprising integrating means for preventing the generation or stop of the prohibition signal by leaving the situation as it is until the inhibition signal is reached. 7. When selectively inhibiting the extraction of code data pulses included in line periods in which there is no image signal representing normal image information of the television signal in the television receiving device, the reception of the code data pulse from the received television signal is Form a pulse signal waveform that includes only line synchronization, field synchronization, and equalization pulses as present in the television signal, and determine when the number of pulses appearing in the pulse signal waveform exceeds a predetermined number for each line period. The number of line periods including pulses exceeding the predetermined number is counted for each field period, and the count value reaches a predetermined value. 1. A selective inhibition method in a television receiver, characterized in that extraction of code data pulses is inhibited when the extraction is performed in a number of field periods.