JPS6130185A - Chost removing device for character broadcasting - Google Patents

Abstract

PURPOSE:To remove a ghost from character broadcasting data by comparing a received demodulating signal obtained from a memory part on the detection side with a reference signal obtained from a memory part on the reference side and controlling a filter on the basis of a discrimination signal which is a compared result to send a ghost compensating signal to a synthesizing part. CONSTITUTION:Since the transmission bit rate of character broadcasting data included in a character multiplex TV signl inputted from an input terminal 1 is 5.73MHz, an error data pattern due to a ghost delayed by 6 bits at maximum is written in a reference side memory part 7. Every holding of a received and demodulated clock line signal and a Fleming's code signal in a memory part 7, a comparing/discriminating part 8 compares the detected data pattern of a reference side memory part 6 with each data pattern of the memory part 7. When a compared result error discriminating signa is sent to a conrol part 9, the tap of the filter 3 is controlled by the control part 9 and a ghost compensation signal is outputted from the filter 3 to the synthesizing part to remove the ghost from the character broadcasting data in the synthesized character multiplex TV signal outputted from the synthesizing part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a teletext ghost removal device for removing ghosts of teletext data in a teletext multiplex television signal.

[Prior art]

Conventionally, when receiving television signals, ghosts occur due to interference between direct waves and reflected waves.

And how to remove ghosts from television signals!
Various methods have been proposed, such as a method using a transversal filter.

By the way, in the case of normal television broadcasting, if a ghost with a delay time of about 0.6 to 0.7 μm or more is superimposed on the television signal, the screen becomes extremely unsightly, but even if a ghost with a delay time of about 0.5 μm or less is superimposed, it will not be noticeable. It doesn't look unsightly.

Therefore, the conventional ghost removal device uses the above-mentioned approx.
In order to remove ghosts with a delay time of 7μ5 or more, for example, as disclosed in Japanese Patent No. 54-102824, ghosts are removed by referring to the leading edge of the vertical synchronization signal in the received television signal. The apparatus is configured to determine the presence or absence of a ghost, generate a ghost correction signal based on the determination, and combine the correction signal with the received television signal to remove the ghost.

On the other hand, in teletext broadcasting, two characters or figures are displayed on a predetermined horizontal scan of a television signal for normal television broadcasting.
Teletext data consisting of digitized code information or pattern information is superimposed to form a teletext multiplex television signal, and image information of the teletext is transmitted using the teletext data.

When receiving and demodulating teletext and displaying it, it is necessary to extract the teletext data from the received teletext multiplexed television signal, and to decode the extracted teletext data and convert it into a television signal.

By the way, in the case of teletext broadcasting, since the teletext data is so-called digital data, the aforementioned ghost having a short delay time of 0.5 microns or less has more influence on the screen.

It is difficult to detect and remove the ghost with a short delay time by detecting the presence or absence at the leading edge of the vertical synchronization signal as in the conventional ghost removal device, and removes the ghost of normal television broadcasting. Conventional ghost removal devices have the drawback of not being able to remove ghosts from teletext data.

[Purpose of the invention]

This invention was made with the above points in mind,
In particular, it is an object of the present invention to remove ghost components with a short delay time of 0.5μ or less, and to remove ghosts from teletext data.

[Structure of the invention]

The present invention provides a transversal filter that receives a teletext television signal multiplexed with teletext data and outputs a ghost correction signal of the teletext television signal based on tap control; a signal synthesis unit that combines the signal and the ghost correction signal and outputs a composite text multiplex television signal; a text broadcast data decoder that extracts the text broadcast data from the composite text multiplex television signal and decodes the data; A detection side memory section that rewrites and holds the clock run-in signal in the teletext data extracted by the decoding section and the Fleming code, and normal data formed by the clock run-in signal and Fleming code when not affected by coasting. pattern, the clock run-in signal when affected by a ghost, and the clock run-in signal of the reference side memory section in which a plurality of types of error data patterns formed by the Fleming code are written in advance, and the detection side memory section. , the detected data pattern formed by the Fleming code is compared with the normal data pattern and each of the error data patterns of the reference side memory section, and the detected data pattern is equal to either the normal data pattern or each of the error data patterns. a comparison/discrimination unit that outputs a discrimination signal based on the discrimination signal; The ghost removal device for teletext broadcasting is characterized by comprising: a control section that performs tap control for the transversal fill so that the detected data pattern matches the normal data pattern.

〔Effect of the invention〕

Therefore, according to the ghost removal device for teletext broadcasting of the present invention, the clock run-in signal is stored in the reference side memory section in advance.
Writes a normal data pattern without ghosts and multiple error data patterns with ghosts of the Fleming code, and determines which data pattern in the reference memory part the detected take pattern in the detection side memory part is equal to or close to. Since ghosts are removed using a simple configuration, it is possible to remove ghosts with a short delay time of 1 μm or less, which is a problem especially in teletext broadcasting.

〔Example〕

Next, this invention will be explained in detail with reference to the drawings showing the first embodiment thereof.

First, the superimposition position of teletext data will be explained.

As shown in Figure 1, teletext data consists of data packets (DP
). In the figure, (H) indicates one horizontal scanning period, (S) indicates a horizontal synchronizing signal, and (CV) indicates a color burst, respectively.

The data packet (Dr) has a transmission bit rate of 5.
As shown in Figure 2 at 78&, a clock run-in signal (OR) for clock recovery of data is written in the first two bytes, and a synchronization of packet j (DP) is written in the first byte following the signal (CR). Fleming code (FC
) is written, and at this time the clock run-in signal (OR
) always consists of a repeat of "Jll, uO+", and the Fleming code (FC) always consists of 'l'", ゛'1", I", 0" IIQII, l"l II
, IIQ"l, 1111".

Therefore, when teletext data without ghosts is received and decoded as shown in FIG. 3(a), the signal pattern obtained by the processing is as shown in FIG. 3(b). Byte transmission bit rate 5.78 & 2
Byte clock run-in signal (CR).

The next 1 byte becomes a normal data pattern with a fleming code (FC) of l/<ite at the same transmission bit rate.

However, in the ghost-free teletext data shown in Figure 4(a), there is a ghost component with a delay time of less than 0.5 μm, for example, as shown in Figure 4(b), a delay time of 1000% (in 175,73Mz). When the ghost of As shown, the clock run-in signal (CR) is all °''l II.

Fleming code (FC) is °l] +1, IT
I II, “I 11% +1111゜°゛0” +
1111, Ill” +1 Q 11, resulting in an error data pattern.

Furthermore, if a ghost with a delay time of 34 Qnsec is superimposed on the ghost-free teletext data in Figure 5(a), as shown in Figure 5(b), the received teletext data will be as shown in Figure 5(C). In this case, the signal 1) pattern obtained by decoding the teletext data received at this time is the clock run-in signal (O
R) is ll'11. “'0” is repeated, but the Fleming code (FC) is l”, °゛l” 11111
, 11111°Tl111 , 111+1 , IJI
I, II□II K-slip, error data pattern different from Fig. 4(d).

That is, the clock run-in signal (OR) that is transmitted.

Since the Fleming code (FC) is always the same, when there is no ghost, the signal pattern demodulated by the decoding process is always the normal data pattern shown in Figure 3(b), and when there is a ghost, the demodulated signal pattern is For example, the signal pattern shown in FIG. 4(d) and FIG.
The error data pattern shown in Figure (d) is 2.

Therefore, the clock run-in signal (OR) of the demodulated signal
By constantly monitoring the data pattern of the Fleming code (FC), it is possible to determine the presence or absence of ghosts of 0.5 μ% or less.

Furthermore, in advance, the clock run-in signal (OR), −y
By storing a normal data pattern and multiple types of error data patterns of Remink code (FC), demodulating it, and determining which of the stored data patterns the fc data pattern matches or is close to, the received teletext It is possible to determine the delay time of ghosts superimposed on data.

If the delay time of the ghost can be determined, the tap coefficient of the transversal filter can be controlled based on the determination, and the ghost can be removed from the received teletext data.

Based on the above principle, a teletext ghost removal device is constructed as shown in FIG.

In the figure, (1) is an input terminal into which a received teletext multiplex television signal is input, (2) is a teletext data section detection circuit connected to input terminal (1), ) is detected from the teletext television signal in which the teletext data is superimposed, that is, the data packet (Dr) in FIG. 1, and a section setting signal for extracting the section is output.

(3) is a transversal filter to which the character multiplex television signal from the input terminal (1) is input, and outputs a ghost correction signal based on tap control.

(4) is a signal synthesis section that adds and synthesizes the text multiplex television signal from the input terminal (1) and the ghost correction signal from the filter (3), and outputs a composite text multiplex television signal.

(5) is a teletext data coder to which the composite text multiplex television signal of the composite unit (4) is input; it extracts the text broadcast data from the composite text multiplex television signal and demodulates it, for example, as shown in FIG. b), Figure 4(d), Figure 5
Figure (d) Digital teletext broadcasting as shown in each ≠−
It is equipped with a comparator (5a) that outputs the evening signal and a processing circuit (5b) that processes the teletext data of the comparator (5a) and converts it into a television signal, It works based on.

(6) is a detection side memory section into which the teletext data output from the comparator (5a) and the interval setting signal of the detection circuit (2) are input, and is rewritten and held every time the received and demodulated character count data is input. do.

(7) is the reference side memory section consisting of ROM, etc.; the normal data pattern shown in FIG. 3(b) and the normal data pattern shown in FIG. d), a plurality of @ class error data patterns such as the error data pattern shown in FIG. 5(d) are written.

(8) Compare the detected data pattern of the clock run-in signal t (OR) and Fleming code (FC) held in the memory (6) with each data pattern in the memory section (7) f
Based on the comparison, it determines which data pattern in the memory unit (7) the detected data pattern is equal to or close to, and detects the delay of ghosts superimposed on the received and demodulated teletext data. In addition to identifying the time, a discrimination signal based on the discrimination described in a, for example, Fig. 8 (
4(d) and 5(d), respectively, are output.

(9) is a control unit to which the discrimination signal of the comparison and discrimination unit (8) is input, and based on the discrimination signal, it discriminates the appropriate amount of ghost correction for the teletext data in the text multiplex television signal of the input terminal (1). Based on this determination, tap control of the filter (3) is performed so that the detected data pattern matches the normal data pattern.

By the way, since the transmission bit rate of teletext data in the teletext television signal at input terminal (1) is 5.73, it is difficult to detect ghosts with short delay times of 1 μ% or less, which are a problem in teletext broadcasts. , +7 in I75.78Ih
Based on the formula 6 out of 4 nsec and 1000/+74, an error data pattern due to a ghost delayed by a maximum of 6 bits is written.

and a received and demodulated clock run-in signal (Ca).

Every time the Fleming code (FC) is stored in the memory section (6), the comparison/discrimination section (8) compares the detected data pattern of the memory section (6) with each data pattern of the memory section (7). At this time, if the detected data pattern is the error data pattern shown in FIG. 4(d) based on the ghost delayed by 174 nsec, that is, the ghost delayed by 1 bit, the controller (9) controls the filter (3) based on the discrimination signal. ) to increase or decrease the first tap of the filter (
3) to the synthesizing section (4) to output a ghost correction signal that cancels out the ghost shown in FIG. is removed to match the detected data pattern in the memory section (6) with the normal data pattern in the memory section (7).

Note that if the detected data pattern is the error data pattern shown in FIG. 5(d), the controller (9)
controls the increase/decrease of the second tap of filter (3) by
Match the detected data pattern to the normal data pattern.

Furthermore, even when the data patterns are other than the error data patterns shown in FIG. 4(d) and FIG. 5(d), the control unit (9) controls the appropriate taps of the filter (3) to match the detected data pattern. match the normal data pattern.

Therefore, even if a ghost with a short delay time of 1 μ% or less is superimposed on the composite teletext television signal, the tap of the filter (3) is controlled to cancel the superimposed ghost, and the composite teletext television signal is Data can be decoded.

As described above, according to the embodiment, it is possible to remove ghosts with a short delay time of 1μ5 or less, which is a problem especially in teletext broadcasting, with a very simple configuration, and it is possible to remove ghosts from teletext data. A very effective teletext ghost removal device can be provided.

[Brief explanation of the drawing]

The drawings show one embodiment of the ghost removal device for teletext broadcasting of the present invention, in which FIG. 1 is an explanatory diagram of the superimposition position of teletext data, and FIG. 2 is a clock run-in signal. Explanatory diagram of Fleming code, Figure 3 (a), (b)
are teletext data without ghosts, waveform diagrams of demodulated signals of the data, Fig. 4(a) to (d), Fig. 5(a)
-(d) are waveform diagrams of the teletext data when a ghost is superimposed on the teletext data, the ghost, the received teletext data, and the demodulated signal of the data, respectively, and FIG. 6 is a block diagram. (1)...Input terminal, (2)...Teletext data section detection circuit, (3)...1-Rance Versal Filter, (4)...Signal synthesis unit, (5) ... Teletext data decoding section, (6) ... Detection side memory section, (7)
... Reference side memory section, (8) ... Comparison discrimination section, (
9)...Control unit. Figure 2 Figure 3 Figure 4 1010101010 1 +10010 Figure 5 CRFC-

Claims (1)

[Claims] (1) A transversal filter that receives a teletext television signal multiplexed with teletext data and outputs a ghost correction signal of the teletext television signal based on tap control; a signal synthesis unit that synthesizes the composite text multiplex television signal with the correction signal and outputs a composite text multiplex television signal; a teletext data decoding unit that extracts the teletext data from the composite text multiplex television signal and decodes it; a detection side memory unit that rewrites and holds the clock run-in signal and Fleming code in the extracted teletext data; a normal data pattern formed by the clock run-in signal and the Fleming code when not affected by ghost; a reference side memory section in which a plurality of types of error data patterns formed by the clock run-in signal and the Fleming code when affected by a ghost are written in advance, and the clock run-in signal and the Fleming code in the detection side memory section. compares the detected data pattern formed by the normal data pattern and each error data pattern of the reference side memory section, and determines whether the detected data pattern is equal to or close to either the normal data pattern or each error data pattern. a comparison/discrimination unit that outputs a discrimination signal based on the discrimination signal, and determines an appropriate ghost correction amount for the teletext data in the teletext multiplex television signal based on the discrimination signal; a control section that performs tap control of the transversal filter so that the transversal filter matches the normal data pattern.