JPH02202284A - Signal processor - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the waveform of a teletext signal which is caused by a dubbing operation by slicing the teletext signal superposed on an input TV signal at a prescribed level to shape the waveform of the signal and inserting the character multiplex signal undergone the waveform shaping into a prescribed part of an output TV signal. CONSTITUTION:A slice level setting circuit 10 detects the average levels of a clock run-in CR and a framing code FC contained in a character multiplex signal, for example, and sets automatically and variably the slice level in accordance with the detected average level. In other words, the output of a 1st mono- multi 101 functions to perform the switching control of a 1st switching circuit 103 and at the same time triggers a 2nd mono-multi 102. Thus the slice level is variably set in response to the average level of the synchronizing part of the teletext signal. Then it is possible to perform an optimum slicing operation in accordance with the degree of deterioration of the waveform of an input TV signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a signal processing device that can prevent waveform deterioration of a text multiplex signal superimposed on a television signal.

(Prior art) In recent years, character multiplex signals, which are digitized character (still image) information such as news, weather forecasts, or additional information of regular broadcast programs, have been broadcast by superimposing them on the vertical retrace period of television signals. Teletext broadcasting is being carried out.

This character multiplex signal is, for example, vertical 204 Xlm2411
One still screen is displayed with approximately 50,000 pixels, and the pattern data and character code data that make up this still screen are vertically returned for each predetermined unit (packet) as shown in Figure 6. On a predetermined horizontal scanning line of the line period (for example, the 14th to 16th and 21st horizontal scanning lines in the case of an odd field, and the 277th to 279th and 284th horizontal scanning lines in the case of an even field) is superimposed with a color burst.

Also, each data packet consists of 3 bytes (2 bytes) as shown in the figure.
It consists of a synchronization part (4 bits) and a data part of 34 bytes (272 bits), and the synchronization part consists of a clock run-in (CR) used for bit-by-bit synchronization on the receiving side, The data section is composed of pattern data, character code data, and error correction codes (for example, Hamming codes).

Furthermore, the signal level of data "1" in the character multiplex signal is approximately 70% of the white level of the video signal in the television signal, and the signal level of data "0"(0') is approximately equal to the pedestal level of the video signal. It is set.

On the other hand, on the receiving side of such a character multiplex signal, the pattern data of the program specified by the keyboard etc. is decoded, character code data is converted into pattern data by a character generator etc., and the decoded data is once decoded. After being written into the display memory, it is displayed on the receiver tube as a teletext screen or mixed with a regular television screen.

(Problem to be Solved by the Invention) By the way, recent VTRs (video tape recorders) have become significantly wider in line with their higher picture quality. For example, high-quality VTRs with a horizontal resolution of 400 TV lines or more have Character multiplex signals can be recorded and reproduced as they are.

However, using such a high-definition VTR, a television signal on which a text multiplex signal is superimposed can be played back to other VTs.
If dubbing is performed to record also in R, the waveform of the character multiplex signal will be degraded due to this dubbing.

Here, the waveform (particularly the peak value) of the character multiplex signal as described above is set to a predetermined signal level as described above.

Therefore, there is a problem in that errors occur when reproducing and decoding a teletext signal whose waveform has been degraded due to dubbing as described above, making it impossible to correctly reproduce teletext.

Further, sharpness correction and color correction may be applied to television signals recorded by the above-mentioned high-quality VTR using an editing machine such as a video processor.

Here, the sharpness correction and color correction are intended to enhance the outline of an image, improve the contrast, and vary the color tone of the image by varying the signal level of the television signal.

For this reason, if sharpness correction or the like is applied to a television signal on which a text multiplex signal as described above is superimposed, not only the signal level of the video signal but also the text multiplex signal will change. There is a problem in that the number of errors increases significantly when decoding is performed.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a signal processing device that can prevent deterioration of a character multiplex signal.

In order to achieve this object, the present invention provides an input terminal to which a television signal with a character multiplex signal superimposed on a predetermined portion is supplied, and one signal line connecting the input terminal and the output terminal, respectively. the other signal line, a waveform shaping circuit that is provided on the other signal line and performs waveform shaping by slicing the signal level of the supplied television signal; and the one signal line and the other signal line. a switch circuit that selectively connects the output terminal to the output terminal; and a switch circuit that switches the switch circuit at a predetermined timing to connect the character multiplexed portion of the television signal supplied via the one signal line to the other signal. The present invention provides a signal processing device characterized by comprising a switch control circuit for interpolating a waveform-shaped character multiplex signal supplied via a line.

(Embodiment) Hereinafter, a preferred embodiment of the signal processing device according to the present invention will be described in detail using FIGS. 1 to 5.

In this embodiment, the present invention is applied to a video processor, and the input terminal 1 of this video processor has an NTS
In addition to being based on the C format, as explained earlier, the television signal (
composite television signal).

The supplied television signal is passed through an automatic gain control circuit (A
After the gain is controlled by GC) 2, it is supplied to a clamp circuit 3 where it is pedestally clamped, and one signal line f1
1 and the other signal line g2.

A video signal processing circuit 4 and a delay line 5 are provided on one of the signal lines g1, and the video signal processing circuit 4
extracts a luminance signal and a color signal from the supplied television signal, and performs sharpness correction on the luminance signal and color correction on the color signal in accordance with the operation of an operation section (volume) not shown. The video signal processing circuit 4 then synthesizes the luminance signal, color signal, synchronization signal, and color burst again and outputs the composite television signal to the delay line 5.

The delay line 5 is used to time-align the signal processing speed on the other signal line g2 and the signal processing speed on one signal line f11, which will be described later.
The television signal output from the switch circuit 6 is sent to the output terminal 7 via one input terminal 6a and the movable terminal 6b.
will be sent to.

Further, the other signal line g2 is provided with a data slice circuit 8 and a filter circuit 9, and the slice level in the data slice circuit 8 is set by a slice level setting circuit 10.

Here, this slice level setting circuit 10 detects, for example, the average level of a clock run-in (CR) or a framing code (FC) in a character multiplex signal, and automatically sets the slice level according to the detected average level. This is a variable setting.

That is, this slice level setting circuit 10 includes first and second monomultis 101, 102 and first to third switch circuits 103, 104, 105, as shown in FIG.
, an integrating circuit 106 and a capacitor 107 for slice level hold, and the output of the first monomulti 101 is connected to the first switch circuit 103.
At the same time, the second monomulti 102 is triggered, and the output of the second monomulti 02 controls the switching of the second and third switch circuits 104 and 105.

Further, the first monomulti 101 generates a horizontal retrace pulse as shown in FIG. 3(B) extracted by the synchronization separation circuit 11 to which the television signal shown in FIG. 3(A) is supplied. is triggered and outputs the output shown in FIG.

The output of this first monomulti 101 is supplied to the first switch circuit 103, and this first switch circuit 10
3 is opened during the high level period of the output of the first monomulti 101.

As a result, the DC power supply 108 of a predetermined level connected to the first switch circuit 103 is connected to the integration circuit 106, and the integration circuit 108 is connected to the integration circuit 106 as shown in FIG.
6 preset levels are set.

On the other hand, the output of the second monomulti 102 triggered by the fall of the output of the first monomulti 101 is as shown in FIG.
As shown in D), the level is high during the period corresponding to the synchronization part of the character multiplex signal, and during the period when the output of the second monomulti 102 is at the high level, the second and third switch circuits 104 and 105 are It will be developed.

Here, the second switch circuit 104 is supplied with the television signal output from the clamp circuit 3, and the synchronization part of the character multiplex signal multiplexed with this television signal is supplied to the second switch circuit 104. The signal is supplied to the integrating circuit 106 via the above.

This integrating circuit 106 is connected to the synchronization section of the character multiplex signal, that is, the clock run-in (CR) and the framing code (
FC), and the integrated output (average value) as shown in FIG. 3(E) is supplied to the capacitor 107 via the buffer amplifier 109 and the third switch circuit 105.

Then, at the same time as the synchronization part of the character multiplex signal ends, the output of the second monomulti 102 also falls, and the second
And the third switch circuits 104 and 105 are closed.

Therefore, the integrated output at the end of the synchronization section is held in the capacitor 107, and this hold level is supplied as a slice level to the data slice circuit 8 via the buffer amplifier 110.

In this way, in this embodiment, by variably setting the slice level according to the average level of the synchronization part in the text multiplex signal, it is possible to perform optimal slicing according to the degree of waveform deterioration of the input television signal. Can be done.

The slice level setting circuit 10 may, for example, once decode a character multiplex signal to detect an error, and then set the slice level so that this error rate is minimized, or adjust the slice level by manual volume control. You may also set it.

The filter circuit 9 also shapes the waveform of the character multiplexed signal sliced as shown in FIG. 4(A) so that it has a predetermined frequency spectrum as shown in FIG. 4(B). The television signal output from the filter circuit 9 is sent to the other input terminal 6c of the switch circuit 6 with a time delay.

On the other hand, the television signal output from the clamp circuit 3 is supplied to the synchronization separation circuit 11, and this synchronization separation circuit 11 extracts the horizontal synchronization signal (H-sync) and vertical synchronization signal (Vsync) from the supplied television signal. -5 sync
) are extracted and output.

Each extracted synchronization signal is supplied to the switch control circuit 12, and this switch control circuit 12 generates a switching signal for switching the switch circuit 6 based on each supplied synchronization signal and supplies it to the switch circuit 6. do.

The switching timing of the switch circuit 6 by this switching signal is the character multiplexed portion in the television signal, that is, in this embodiment, the 14th to
16 and 21 horizontal scanning period, and 277th to 2nd
It is connected to the horizontal scanning period terminal 6C of the 79th and 284th main ports, so that the television signal sent out through the one signal line is sent out through the other signal line during the vertical retrace period. The waveform-shaped character multiplexed signal is time-division multiplexed.

According to the video processor configured as described above, by slicing and waveform shaping only the character multiplex signal, the output terminal is The waveform of the character multiplex signal superimposed on the television signal output from 7 can always be kept constant.

Therefore, the occurrence of errors during decoding due to waveform deterioration of the character multiplexed signal can be significantly reduced.

Further, by connecting a reproduction side VTR to the input terminal 1 and connecting a recording side VTR to the output terminal 7 for dubbing, it is possible to prevent waveform deterioration of the text multiplex signal during dubbing. Note that when performing such dubbing, the video signal processing circuit 4 is not required.

Furthermore, in this embodiment, by providing the automatic gain control circuit 2 at the input stage, even if the signal level of the input television signal deviates from a predetermined level, it is automatically adjusted to a predetermined range. Furthermore, optimal slicing of the character multiplexed signal can be performed.

By the way, in the above embodiment, the video signal processing circuit 4
However, as shown in FIG.
) may be combined in the adder 13 with the television signal output from the switch circuit 6.

Thereby, it is possible to prevent not only the character multiplex signal but also the waveform deterioration of each synchronization signal.

Note that, in this case, the configuration is such that the synchronization signal is not synthesized in the video signal processing circuit 4.

(Effects of the Invention) As is clear from the above description, according to the present invention, a character multiplex signal superimposed on an input television signal is sliced at a predetermined level and waveform-shaped, and the waveform-shaped character multiplex signal is By interpolating this into a predetermined portion of the output television signal, it is possible to prevent the waveform deterioration of the text multiplex signal due to dubbing, and also to prevent the waveform deterioration of the text multiplex signal when signal processing is applied to the television signal. can do.

Therefore, the occurrence of errors when decoding this character multiplex signal can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a signal processing device according to the present invention, FIG. 2 is a circuit diagram also showing a slice level setting circuit, and FIGS. 3(A) to (E) are shown in FIG. A time chart showing the operating state of the slice level setting circuit (8) (B), a time chart showing the operating state of the fourth [9Li filter circuit], and FIG. 5 show another embodiment of the signal processing device according to the present invention. The block diagram and FIG. 6 are waveform diagrams showing a general television signal on which a character multiplex signal is superimposed. DESCRIPTION OF SYMBOLS 1... Input terminal, 6... Switch circuit, 7... Output terminal, 8... Data slice circuit (waveform shaping circuit), 10...
...Slice level setting circuit, 12...Switch control circuit, gl...One signal line, g2...The other signal line.

Claims (1)

[Scope of Claims] An input terminal to which a television signal with a character multiplex signal superimposed on a predetermined portion is supplied; one signal line and the other signal line connecting the input terminal and the output terminal, respectively; a waveform shaping circuit that is provided on the other signal line and performs waveform shaping by slicing the signal level of the supplied television signal; a switch circuit connected to the output terminal; and a switch circuit that is switched at a predetermined timing so that the character multiplexed portion of the television signal supplied via the one signal line is supplied via the other signal line. A signal processing device comprising a switch control circuit for interpolating waveform-shaped character multiplex signals.