JPH07245746A - Identification control signal system and demodulation system for identification control signal - Google Patents

Abstract

PURPOSE:To deliver correctly an identification command or control information and to demodulate it by using a horizontal synchronizing signal as a standard only and using timing information included in an identification control signal itself as a strict reference for the demodulation of an identification signal. CONSTITUTION:A trailing part of a horizontal synchronizing signal 2 is detected and checked by using a waveform 6, and a timing counter 1 is incremented when the trailing part is generated slower than a center of the waveform 6 by a prescribed time, and the timing counter 1 is decremented when the trailing part is generated faster than the center of the waveform 6 by a prescribed time, and rising/trailing of NRZ parts B1-B4 of an identification command is detected similarly. Furthermore, a signal for a period when the chrominance subcarrier is modulated is subject to synchronization detection by the chrominance subcarrier to detect rising 7 trailing of a 0/1 signal, a timing of a change point is checked by using a waveform 7 and the similar operation is implemented to that of horizontal synchronization depending on fast/slow timing. On the other hand, confirmation signals B25-B27 are subject to synchronization detection by a sine wave formed by the timing counter 1 and the phase or the timing count 1 is similarly corrected so that the phase is coincident.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an identification control signal in a television signal such as a so-called EDTV-II and its demodulation system.

[0002]

2. Description of the Related Art Conventionally, an identification control signal is arranged on a specific scanning line, and the phase of various reinforcing signals and the waveform of the identification control signal are determined with reference to the horizontal synchronizing signal (for example,
Japanese Patent Application No. 5-246588, transmission system of control signal in television signal). However, in an actual broadcasting system, the video signal may be shifted relative to the horizontal synchronizing signal for the purpose of reversing the polarity of the color signal, and in the actual system, this phase management itself is necessary. It may be incomplete.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a system in which the conditions of the phase relationship of the waveforms are relaxed and which corresponds in reality, and a demodulation system in that case. That is, when the condition of the phase relationship between the horizontal synchronization signal and the broad sense video signal (the broad sense video signal including the identification control signal and the non-image portion reinforcement signal) is loosened, (1) the identification command and control information are correctly transmitted. And (2) to provide a method of correctly demodulating these.

[0004]

In the present invention, (1) For correct transmission, a video signal in a broad sense is considered as a time reference, and a horizontal synchronizing signal is considered as a secondary floating. In addition, as a result (2), in order to correctly demodulate the video signal and the identification control signal, the horizontal synchronization signal should be kept as a rough guideline in the identification signal demodulation, and the timing information included in the identification control signal (including the color burst) itself. Is used as a strict standard.

[0005]

In the past, the reference of horizontal timing information was the horizontal synchronizing signal, but the present invention is only used as a rough timing reference. Instead, the timing information in the identification control signal itself indicated by this becomes important. However, for existing receivers, there is no difference that the horizontal sync signal is important reference timing information.

[0006]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 is a conceptual diagram in the embodiment. Hereinafter, consider the case where digital signal processing is performed in demodulation.

A first object of the present invention is to extract horizontal timing. For this reason, for example, as is often done in modern television systems,
In a system having a clock frequency of xfsc, it is necessary to correctly pull in the timing counter 1 that counts one horizontal cycle by 4xfsc. Here, fsc is the color subcarrier frequency (≈3.58 MHz).

In the identification control signal waveform shown in the upper part of FIG. 1, a horizontal synchronizing signal 2, a color burst period 3, and 27 bits as an identification command, that is, B1, B2, B3, ... B27 are arranged. Among them, the phase in the horizontal synchronization 2 period is fluid as described above.

In this embodiment, first, the color subcarrier reproducing circuit 4 is operated by the color burst signal. this is,
It is already used in current television receivers, and its operation is well known. Further, this is multiplied by 4 by the clock generation circuit 5, and the timing counter 1 is operated by using this as a clock pulse. This operation is also well known though there are various modifications.

In order to adjust the phase of this counter (the timing at which the count reaches 0, etc.), in the present invention, the count value of the timing counter 1 is increased or decreased (stepped or retarded) by the following method.

First, the falling portion of the horizontal synchronizing signal 2 is detected, and the waveform 6 as shown is applied and examined. This waveform 6 is synthesized by the count value of the timing counter 1.

Here, if the trailing edge occurs later than the center of the waveform 6 by a certain time or more, the timing counter 1
Add (advance the hands of the clock). Similarly, if it occurs earlier, subtract (delay) it. If it is near the correct position, it is not added or subtracted as is apparent from the figure.

Similarly, the NRZ part (B
1, B2, B3, B4) rising / falling is detected.
Further, the signal in the period of B6, B7, ... B23 in which the color sub-carrier is modulated is synchronously detected by the color sub-carrier to extract the 0/1 signal, and the rising / falling thereof is detected. (0
Since it is modulated in the phase and π phase, the demodulated signal is apparently +1, -1).

The rising / falling edge of this, that is, the timing of the change point is examined with the waveform 7. This waveform 7 is also formed by the timing counter 1. The timing is too late,
An operation similar to horizontal synchronization is performed.

On the other hand, confirmation signals B25, B26, B27
, A 2.04 MHz sine wave is transmitted. Therefore, this is synchronously detected with a sine wave formed from the timing counter 1, and the phase of the timing counter 1 is similarly corrected so that the phases match.

If they match, the output of the confirmation signal detection circuit 8 becomes maximum as shown in the figure. On the other hand, if the phase is reversed, it will be the maximum negative value. The output will be 0 if it is slightly shifted by π / 2. Therefore, the confirmation signal detection circuit 9 synchronously detects the sine wave deviated by π / 2, and the phase of the timing counter 1 is corrected so that it is always zero.

In the waveforms 6, 7, and 10 in the figure, the dead zone near 0 is to avoid the influence of some noise. In particular, in the case of the waveform 6, since the horizontal synchronization position is considered in a floating manner, the dead zone is wide (for example, ± 10 pixel intervals in an extreme case. Here, one pixel interval is 1/14.
3 MHz).

Others are narrower than this, for example, ± 2 pixel interval. For synchronous detection output, it may be better to have a one-pixel interval or so.

The following modifications may be made in the actual circuit configuration.

(1) Since the clock is generated by multiplying the color subcarrier frequency fsc by 4 here, the phase before the multiplication by 4 can be used as the phase information of the timing counter 1.
These are already widely used in digital video technology.

(2) As a circuit for detecting the change point of the identification command from the NRZ waveform or the demodulated waveform,
A general method is to use a so-called differentiating circuit and further determine the absolute value of the positive or negative component in order to extract it. However, this is susceptible to noise. In order to avoid this, it is desirable to extract a change point where a certain threshold value or more is passed a plurality of times, and then another threshold value is passed a plurality of times (or a change point of positive / negative reversals).

(3) When the S / N state is particularly poor, the stepping or retarding operation of the timing counter 1 is not performed by one detection at once, but integrated by a plurality of times.
(That is, if it is detected multiple times, it is detected).

(4) Confirmation function parts B25, B26, B27
When the phases are matched in (1), in addition to analog synchronous detection as described above, detection using a binarized signal is also possible.

(5) The change point detection and the waveforms 6 and 7 have been described as signals for the step-up and the step-down of the timing counter 1. However, specifically, the purpose is to slow down if it is detected before the central dead zone, and to step up if it is detected later. It can be designed easily.

(6) Here, the case of subtraction and addition one by one is shown, but a more complicated combination (application of analog processing of adding and subtracting a large number according to the magnitude of deviation) is also possible. Let's do it. In addition, a method of adding a large number or stopping other additions / subtractions is also possible when seeking coincidence with the horizontal synchronizing signal.

[0026]

According to the present invention, the discrimination control signal in which the horizontal synchronizing signal is in a floating position with respect to the color burst signal phase and the discrimination command signal phase is realized. Also, multiplexing of various reinforcement signals based on this has become possible. Then, specifically, it becomes possible to demodulate this by the method described in the embodiment.

That is, in the horizontal synchronizing signal, it is only necessary to know the general timing relationship as a whole, and strictly speaking, it is possible to determine by the color burst phase and the identification command (including the confirmation signal), and it becomes possible to demodulate the reinforcement signal. .

[Brief description of drawings]

FIG. 1 is a waveform diagram and a configuration diagram according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Timing counter, 2, 3 ... Waveform, 4 ... Color subcarrier reproduction circuit, 8, 9 ... Confirmation signal detection circuit.

Claims (2)

[Claims] 1. A color burst phase having a defined phase relationship, an identification command, a subcarrier modulated by the identification command, a confirmation signal not present in the video signal, and a horizontal position placed in a floating position with respect to these. A television signal identification control signal system characterized by comprising a synchronizing signal and being arranged on a specific scanning line. 2. A color burst phase having a defined phase relationship, an identification command, a subcarrier modulated by the identification command, a confirmation signal not present in the video signal, and a horizontal position arranged in a floating position with respect to these. Receives a television signal including an identification control signal composed of a synchronization signal,
An identification control signal characterized in that the horizontal synchronization signal in a floating position is used as a rough guide to determine the phase, and the horizontal timing is defined by the color burst phase, identification command, subcarrier modulated by the identification command, confirmation signal, etc. Demodulation method.