JPH02260787A - Chrominance signal system discriminator for magnetic reproducing device - Google Patents

Abstract

PURPOSE:To attain a stable color signal processing circuit without generating a discrimination error at special reproduction by providing a discrimination result holding circuit between a color system discrimination circuit and the output terminal of discrimination result and holding the result of discrimination of the color system discrimination circuit at the special reproduction. CONSTITUTION:A discrimination result holding circuit 24 is provided between a color system discrimination circuit 22 and a discrimination result output terminal 112 so as to hold the result of discrimination of the color system discrimination circuit 22 at the special reproduction. When the information representing the special reproduction is inputted from a special reproduction state control input terminal 13, the discrimination result holding circuit 24 holds just preceding discrimination result. Even when mis-discrimination result is outputted due to noise or the like generated at the reproduction of the output of the chrominance signal system discrimination circuit 22, the output of the chrominance signal system discrimination result output terminal 12 is unchanged. The holding operation is functioned till the special reproduction is finished. Thus, the chrominance signal processing circuit is stably operated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for determining the color signal method of an image signal, and particularly to a device for determining the color signal method of a reproduced signal of a magnetic reproduction device compatible with a plurality of color signal methods. It is related to.

(Prior Art) Currently, multiple television signal formats are used in each country around the world.Depending on the signal format, magnetic recording and playback devices also record in different formats. In devices that reproduce multiple formats, devices that automatically determine the format of the signal to be reproduced have been put into practical use.

FIG. 2 shows the configuration of an automatic discrimination device in this type of magnetic reproducing device. In the figure, 11 is a color signal input terminal;
2 is a burst sampling circuit, 22 is a color signal type discrimination circuit, 23 is a time constant circuit, and 12 is a color signal type discrimination result output terminal.

Next, the operation will be explained. A reproduced color signal is input to the color signal input terminal 11 from the output of the color signal processing circuit of the magnetic reproduction device. As for the reproduced color signal, only the burst signal is transmitted by the burst extraction circuit 21 to the color discrimination circuit 22. The color signal type discrimination circuit 22 detects the phase change between the burst signal and the subcarrier signal to discriminate the color signal type. In this case, the burst signal exists only intermittently, so
It is necessary to sample and hold the above-mentioned phase change etc. using the time constant circuit 23.

The color signal method discrimination result obtained in this manner is outputted to the color signal method discrimination result output terminal 12 as discrete voltage values or the like. This output controls the operation of the color signal processing circuit to obtain a normal color signal output.

[Problem to be solved by the invention]

Incidentally, a problem with the above-mentioned system is the stability of the discrimination operation during special playback, and a problem particularly occurs during fast forward/rewind playback called speed search. This is because during fast forward/rewind playback, the magnetic head diagonally traces the track where the signal is recorded, so the amplitude of the reproduced color signal is not stable, and the signal amplitude decreases or does not appear at all at the turn of the track. It's for a reason.

In the above-mentioned system, it becomes difficult to stably discriminate the color signal method when the amplitude of the reproduced color signal becomes small as described above. In order to obtain correct discrimination results even under such conditions, the time constant of the time constant circuit 23 is set to a large value so that the color discrimination circuit does not respond to changes in the color signal amplitude at the change of tracks. A method has been developed to do so.

However, in this method, since the time constant of the time constant circuit 23 becomes very large, the disadvantage is that the determination time during normal reproduction becomes long. For this reason, when starting playback or when there is an unrecorded portion during playback, it may take several seconds until the correct color is played back.

This invention was made in order to solve the above-mentioned problems of the conventional method, and it is a magnetic reproduction system that can distinguish color signal systems in a short time and stabilize the discrimination results during special reproduction. The purpose of this invention is to obtain a color signal system discrimination device for a device.

[Means to solve the problem]

A color signal method discriminating device for a magnetic reproducing device according to the present invention includes:
A discrimination result holding circuit is provided between the color type discrimination circuit and the discrimination result output terminal, and the discrimination result of the color direction two discrimination circuit is held during special playback.

[Effect]

By having the above-described configuration, the present invention can determine the color signal system in a short time, and can stabilize the determination result during special playback.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a color signal type discriminating device for a magnetic reproducing apparatus according to an embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 2 indicate the same parts. 24 is a discrimination result holding circuit composed of a D flip-flop or the like, and 13 is a special playback state control input terminal.

Next, the operation of the above embodiment will be explained.

Similar to the conventional circuit, a reproduced color signal is inputted to the color signal input terminal 11 from the output of the color signal processing circuit of the magnetic reproducing device, and only the burst signal is extracted by the burst extraction circuit 21. This burst sampling circuit uses a burst gate pulse signal created by a monostable oscillation circuit or the like from a synchronization signal separated from the reproduced signal, and outputs only the reproduced color signal during that pulse period, suppressing signals during other periods. It is supposed to be done.

The burst signal output from the burst sampling circuit is transmitted to the sex-man style discrimination circuit 22. This seductive male discrimination circuit 2
A circuit 2 detects the phase relationship between the input burst signal and the subcarrier signal created by the color signal processing circuit. For example, the burst signal of the NTSC system always has a constant phase, but the phase of the burst signal of the PAL system changes by 90 degrees every horizontal period. Therefore, considering the phase relationship between the constant phase subcarrier signal and the burst signal, the NTSC
In the PAL method, the phase difference is always constant, but in the PAL method, the phase difference changes every horizontal period. Since this phase change occurs only during the burst period, it is sampled and held by the time constant circuit 23.

In the above embodiment, a determination result holding circuit 24 is provided so that the determination result during special playback such as speed search is stable. When information indicating the special playback state is input from the special playback state control input terminal 13, the determination result holding circuit operates to hold the immediately previous determination result. Even if the output of the color signal method discrimination circuit 22 outputs an erroneous discrimination result due to noise generated during special reproduction, the output of the color signal method discrimination result output terminal 12 does not change. This holding operation functions until the special playback ends.

In this way, according to this embodiment, the color signal discrimination result immediately before starting special reproduction is held by the discrimination result holding circuit, so that the color signal processing circuit can operate stably.

Furthermore, since the discrimination operation during special playback is stable, the time constant of the sex-man type discrimination circuit can be set short, and the discrimination operation can be made faster.

In addition, in the above embodiment, only color discrimination of PAL and NTSC systems was explained, but PAL, NTSC, SECAM
3 methods of color discrimination, or SECAM and PAL,
Of course, the present invention can also be applied to the case of color discrimination between SECAM and NTSC, and the same effects as those of the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the color signal method discriminating device for a magnetic reproduction device according to the present invention, a discrimination result holding circuit is provided between the color male type discrimination circuit and the discrimination result output terminal, and color male type discrimination is performed during special reproduction. Since the circuit discrimination results are held, discrimination errors do not occur during special playback, and the color signal processing circuit can operate stably.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a color signal method discrimination device for a magnetic reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing conventional color signal method discrimination colors. In the figure, 11 is a color signal input terminal, 12 is a discrimination result output terminal, 13 is a special reproduction state control input terminal, 21 is a burst sampling circuit, 22 is a color man type discrimination circuit, 23 is a time constant circuit, and 24 is a discrimination result. This is a holding circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A device for reproducing a magnetically recorded video signal, which determines the color signal system of the reproduced video signal, comprising means for extracting a burst signal from the reproduced color signal, and the extracted burst signal. means for discriminating the color system from the phase change of the color signal; and during normal playback, the above discrimination result is directly output to the color signal mode discrimination result output terminal, and during special playback, the immediately preceding above discrimination result is held and the above color signal mode discrimination result is output. 1. A color signal method discriminating device for a magnetic reproducing device, comprising: holding means for outputting to a terminal.