JPH01268277A - Video signal processing device - Google Patents

Abstract

PURPOSE:To execute stable format discrimination by switching a level detecting period according to the result of frequency discrimination for a reproducing video signal. CONSTITUTION:When the output of a level detecting circuit 6 is L, the control terminals of signal switching circuits 12 and 14 are selected so that the output can pass through a gate circuit 11 and a hold circuit 13. Thus, it is determined by the output of the level detecting circuit 6 whether the frequency discrimination is executed only during a vertical retrace line period, out of the angle- modulated video signals, or the frequency discrimination is always executed. Thus, at a still time or at a fine slow time, etc., even when the envelope of the angle-modulated video signal falls down, the stable discriminating operation can be executed. Further, when the frequency discrimination is executed only during the vertical retrace line period, since the operation is regardless of the contents of the video signal and a side wave band is slightly enlarged, the exact discrimination can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in the playback system of a magnetic recording/playback device, etc., and is capable of automatically switching frequency characteristics, etc. according to the frequency band of an angle-modulated video signal. The present invention relates to a signal processing device.

2. Description of the Related Art Generally, in a high-band compatible VTR, it is necessary to record and reproduce video signals in a plurality of formats on the same magnetic tape. In this case, the user generally selects the format using a switch or the like during recording, and the VTR automatically determines and switches the format during playback, and the method of format discrimination during playback is important.

FIG. 3 is a block diagram showing an example of a conventional video signal processing device. In FIG. 3, a signal applied to an input terminal 1 is supplied to a first equalizer circuit 2, a second equalizer circuit 3, and a peaking circuit 4. The output of the first equalizer circuit 2 is supplied to one input terminal of the signal switching circuit 6, and the output of the second equalizer circuit 3 is supplied to the other input terminal. The output of the peaking circuit 4 is supplied to a level detection circuit 6, which outputs control signals 31 .
7 is supplied to the signal switching circuit 5, and a desired signal is selected and supplied to the output terminal 7.

As an example, consider a case where the video signal processing apparatus shown in FIG. 3 is used in the reproduction system of a VTR compatible with the VH3 system and the 5VH8 system. The signal applied to the input terminal 1 is an angle-modulated video signal having a frequency band as shown in FIGS. 4A and 4B.

That is, in the VH8 system, as shown in Figure 4A, 3.4
MHz to 4.4MHz luminance signal carrier and o, 63M
Sidebands are distributed around the Hz color signal carrier wave, and 5VH8
In this method, as shown in Figure 4B, the frequency range is from 5.4MHz to 7.0MHz.
Sidebands are distributed around the luminance signal carrier wave of MHz and the color signal carrier wave of 9 and 63 MHz. Therefore, the peaking circuit 4 is set to emphasize the level of either the frequency band from 3.4 MHz to 4.4 MHz or from 5.4 MHz to 7.0 MHz, and its output is used as a reference value by the level detection circuit e. By comparison, it was determined whether it was the VH3 method or the %5VH85VH8 method.

Problems to be Solved by the Invention However, as is clear from FIGS. 4A and 4B, the frequency bands of the VH8 and 5VH8 systems almost overlap when sidebands are included. Therefore, there is a problem in that a particular video signal is incorrectly determined.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an excellent video signal processing device that can prevent erroneous determination even for a specific video signal and can perform stable format determination.

Means for Solving the Problems In order to solve the above problems, the video signal processing device of the present invention uses a predetermined delay time and a predetermined time synchronized with a head switching signal for selecting one output from a plurality of video heads. means for generating a control signal having a width, means for emphasizing the level of a specific frequency band of the angle-modulated video signal, means for limiting the output period of the emphasizing means to the control signal period, and the emphasizing method. means for selecting the output of the means and the output of the limiting means; means for detecting the level of the output of the selecting means; and the angle-modulated video signal according to the output of the level detecting means 5A, ->. and means for switching the frequency characteristics of the signal, and is configured to switch the selection means in accordance with the output of the level detection means.

Effect of the Invention With the above-described configuration, the present invention has a system in which the output of the level detection circuit determines whether the frequency of the angle-modulated video signal is determined only during the vertical blanking period or whether the frequency is constantly determined. It is possible to perform stable discrimination operations even when the envelope of the angle-modulated video signal falls during stills, fine throws, etc. Moreover, when frequency discrimination is performed only during the vertical retrace period, accurate discrimination is possible because it is unrelated to the content of the video signal and the spread of sidebands is small.

Embodiment Hereinafter, an embodiment of a video signal processing apparatus according to the present invention will be described with reference to the drawings.

Figure 1 shows a block diagram of the same embodiment.
Parts that are the same as those in the figures are designated by the same reference numerals.

In FIG. 1, a signal applied to a first input terminal 1 is supplied to a first equalizer circuit 2, a second equalizer circuit 3, and a peaking circuit 4. First equalizer circuit 2
The output of is supplied to one input terminal of the signal switching circuit 5,
The output of the second equalizer circuit 3 is supplied to the other input terminal. The head switching signal applied to the second input terminal 8 is supplied to an integrator 9, transformed into a trapezoidal wave, and supplied to a pulse generator 10. The output of the pulse generator 1° is supplied to the control terminals of the gate circuit 11 and the hold circuit 13. The gate circuit 11 switches the output of the peaking circuit 4 according to the output of the pulse generator 1o to the signal switching circuit 12.
is supplied to one input terminal of the peaking circuit 4, and the output of the peaking circuit 4 is supplied as is to the other input terminal. The output of the signal switching circuit 12 is supplied to the level detection circuit 6, and the output of the level detection circuit e is supplied to the control terminal of the signal switching circuit 12, one input terminal of the signal switching circuit 14, and the other via the hold circuit 13. The signal 78-7 is supplied to the input terminal, and further supplied to the control terminal of the switching circuit 140. Signal switching circuit 1
The output of 4 is supplied to a control terminal of a signal switching circuit 6, and a desired signal is selected and output to an output terminal 7.

Here, VTR compatible with VH8 system and 5VHS system
The operation when the video signal processing apparatus shown in FIG. 1 is used in the reproduction system will be described in detail with reference to FIG. 2.

, FIG. 2a is a waveform diagram showing a vertical retrace period of a composite video signal before angle modulation. VH8 system and 5VH
In the No. 5 system, the timing of the head switching signal for both recording and reproduction is approximately e, 5H (1 Hi 1 horizontal period) before the vertical synchronizing pulse, as shown in FIG.

Next, the waveform head switching signal shown in Figure 2 is input to the integrator 9.
, the output waveform becomes a trapezoidal wave as shown in FIG. 2C. The pulse generator 10 has a threshold level of ■1.
(2) The head switching signal has a predetermined delay time and a predetermined time width from the output of the two comparators as shown in Fig. 2d, and the vertical synchronization pulse period and It is also possible to generate a wide range of control signals.

Also, ■1. If v2 is set to a potential that is almost symmetrical with respect to the intermediate value between the low level VL and high level vH of the head switching signal, a control signal almost similar to that shown in Fig. 2d is generated at the falling edge of the head switching signal. be able to.

Assume that the peaking circuit 4 is set to emphasize the level of a frequency band of 3 or 4 MHz, which is the synchronization signal carrier frequency of the VH8 system, and a reproduced video signal of the VH8 system is input to the first input terminal 1. Furthermore, when the output of the level detection circuit 6 is L, the signal switching circuit 12.degree. 140 control terminal is selected so that it passes through the gate circuit 11 and the hold circuit 13. At this time, 3.4MH! If the component exceeds the reference value of the level detection circuit 6 and becomes the output signal H, the frequency is constantly determined. next,
If a 5VH8 format reproduced video signal is input, the output signal of the level detection circuit 6 becomes L, and the gate circuit 11
■ Frequency discrimination is performed only during the blanking period.

Effects of the Invention 9 ・, -7' As is clear from the above explanation, the present invention provides an excellent method that allows highly stable formant discrimination by switching the level detection period based on the frequency discrimination result of the reproduced video signal. A video signal processing device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the video signal processing device according to the present invention, and FIG. 2 is an explanatory formula and S V4
FIG. 3 is a frequency allocation diagram of the HA method. 1.8...Input terminal, 2,3...Equalizer circuit, 4...Peaking circuit, 6,12
．． 14...Signal switching circuit, 6...Level detection circuit, 7...Output terminal, 9...
Integrator, 10...Pulse generator, 11...
...Gate circuit, 13...Hold circuit.

Claims (1)

[Claims] means for generating a control signal having a predetermined delay time and a predetermined time width synchronized with a head switching signal for selecting one output from a plurality of video heads; and a level of a specific frequency band of the angle-modulated video signal. means for emphasizing, means for limiting the output period of the emphasizing means to the control signal period, means for selecting the output of the emphasizing means and the output of the limiting means, and detecting the level of the output of the selecting means. and means for switching the frequency characteristics of the angle-modulated video signal according to the output of the level detection means, and configured to switch the selection means according to the output of the level detection means. A video signal processing device characterized by: