JPS62295582A - Video control signal reader - Google Patents

Abstract

PURPOSE:To eliminate the mis-discrimination of a video control signal by using a clamper to boost a pre-shoot signal component of a pedestal level or less up to a threshold level of a detector. CONSTITUTION:A signal demodulated into a video signal is amplified by an amplifier 9 and only a VPS signal part is extracted by a VPS extracting gate 10, the result is clamped by a clamper 11 and fed to a detector 5 through a buffer 12. Since the pre-shoot part is boosted to higher potential by the effect of the clamper 11, the level reaches the threshold level of the detector 5. Thus, the mis-discrimination of the VPS signal due to pre-shoot caused frequently at the start of the VPS signal is eliminated.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Application Field The present invention relates to a video control signal reading device that distinguishes and decodes video control signals contained in television broadcast waves. .

2. Description of the Related Art Conventionally, video, programs, and systems have been developed in which a video control signal is superimposed on the vertical blanking period of a video signal of a television broadcast wave, and this video control signal is reproduced on the receiving side to control equipment such as a VTR. (abbreviated as VPS) has been proposed. Note that the video control signal is referred to as a VPS signal.

FIG. 4 (-) is a waveform diagram showing a video signal including a VPS signal, and on the 16th line from the vertical synchronization signal,
The S signal is superimposed. FIG. 4(b) is an enlarged view of the waveform showing the vPS signal. The vPs signal is as shown in the figure.
The maximum frequency fo-2 is a pulse with a period of 5MH2, and the first 10μ81i1C is a reference pulse of vPs,
Next, 10 μsec includes a start signal and further a data signal.

Therefore, on the receiver side, distinguish between these pulses and
Deciphers the data and controls the equipment on the receiver side.

Figure 3 shows VPs detection 1 of a conventional device, such as a VTR.
FIG. 2 is a block diagram of the circuit in FIG.

The video signal including the PS signal shown in FIG. 4 is sent out as a broadcast wave from the broadcasting station 1, inputted to the antenna of the receiving device, selected by the tuner section 2, demodulated by the demosimulator section 3, and then I Vpp video signal 4 (including the VPS signal) is returned. This signal is
On the other hand, in the case of a VTR, etc., it is supplied to the recording circuit, but
The other side is supplied to the vPS detector 5, where only the line with the PS signal is extracted from the video signal.
It passes through a waveform shaping circuit 7 and becomes a control signal 8.

Problems to be Solved by the Invention However, in the above configuration, the propagation state of radio waves from the broadcasting station 1 to the receiver and the tuners 2 to . Due to circuit elements such as the demosimulator section 3, the waveform of the vPS signal at the output 6 of the detector 5 does not become an ideal waveform as shown in FIG. It is normal for the waveform to be distorted. In particular, when the tuner 2 is out of tune, the waveform often has a large preshoot component A.

Now, FIG. 6 shows a commonly used detection method.

FIG. 6(a) shows the beginning of a normal PS signal, with a pulse above the level corresponding to the pedestal portion of the video signal. Normally, harmonic components are removed in the transmission line, so the waveform is close to a sine wave. When detecting, the pedestal part is set as the level, and normal VPS is detected.
The pulse level is set to zero, and the threshold level is set to 100 points ahead. Therefore, the shaped output waveform after detection by the wave detector 5 is as shown in FIG. 6(b). Note that FIG. 6 shows the first part of the vPS signal, and this part consists of nine pulses used to determine the presence or absence of the PS signal.

By the way, if we consider the case where a signal with preshoot distortion as described above is input to a detector that operates in this way, the beginning of the waveform will be distorted by the preshoot component as shown in Figure 7(a). Because the pulses are lowered below the pedestal level, the original pulses do not reach the hold level of Threshold 5) and the output waveform is only the last few pulses of the nine normal pulses, as shown in Figure 7 (0)). The output is slow. Therefore, this output has the disadvantage that it cannot be distinguished from a vPS signal.

The present invention eliminates this problem and provides a video control signal reading device that faithfully reproduces a PS signal necessary for normal PS operation.

Means for Solving the Problems In order to solve the above problems, the video control signal reading device of the present invention includes reception selection means for receiving television broadcast waves containing video control signals and selecting frequencies as necessary; video signal demodulation means for demodulating the output of the reception selection means to produce a video signal; video control signal selection means for extracting a video control signal from the output signal from the video signal demodulation means;
The apparatus includes means for clamping the output signal of the video control signal selection means, and a detector having a threshold voltage 6 at a constant potential higher than a reference potential consisting of the pedestal portion of the video signal.

According to the above-described configuration, the present invention can raise the threshold level potential of the detector, which uses the pre-shoot signal component below the pedestal level as a clamper, and eliminates misjudgment of video control signals. It is possible.

Embodiment Hereinafter, a video control signal reading device according to an embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a video control signal reading device of the present invention.

The signal demodulated into a video signal is amplified by an amplifier 9, only the vPS signal part is extracted by a vPS extraction gate 1o, and then clamped by a clamper 11, and further supplied to a detector 5 through a buffer 12. . The input waveform 12a of the wave detector 5 at this time is shown in FIG. 2 (,). Due to the effect of the clamper 11, the pre-X shoot portion is raised to a higher potential, so that it reaches the threshold level of the detector 5, and the output control signal 13 has the waveform shown in FIG. 2 Φ). The waveform of this output control signal 13 is shown in FIG.
) is almost the same as the output when the signal is normal.

Note that the reference potential of the clamper 11 is defined as v1, where the potential of the shoot part is set to vl, the normal PS pulse level is set, and the threshold level is set to v1.
It is set to a value such that +ΔV>V□.

Effects of the Invention As described above, according to the present invention, it is possible to eliminate PS signal misjudgment due to pre-shoot, which often occurs at the beginning of a vPS signal, thereby realizing more stable video control operation. It is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the video control signal reading device of the present invention, FIGS. 2(a) and (b) are signal waveform diagrams in the same embodiment, and FIG. 3 is a conventional video control signal reading device. A block diagram showing the device; FIGS. 4(a) and 4(b) are signal waveform diagrams showing video signals including video control signals;
Figures 6(a) and 6(b) are signal waveform diagrams showing video control signals, and Figures 7(a) and 6(b) are signal waveform diagrams in a conventional video control signal reading device. 2...Tuner section, 3...Demosimulator section, 6...Detector, 7...Shaper, 10...vPS signal gate Part, 11...
... Clampa.

Claims (1)

[Claims] reception selection means for receiving television broadcast waves including video control signals and selecting a necessary frequency; video signal demodulation means for demodulating the output of the reception selection means to generate a video signal; and output from the video signal demodulation means. video control signal selection means for extracting a video control signal from the signal; clamping means for clamping the output signal of the video control signal selection means; 1. A video control signal reading device comprising: a wave detector having a wave detector, wherein the wave detector detects an output signal of the clamping means.