JPH02285780A - Discrimination circuit - Google Patents

Abstract

PURPOSE:To discriminate whether a TV signal of the NTSC system or of the PAL system in a short time by measuring a period of a vertical synchronizing signal in a computer and discriminating whether a vertical synchronizing signal is based on the PAL or the NTSC system based on the measurement of the period and discriminating the system of the vertical synchronizing signal when the result of discrimination shows identical discrimination for a prescribed number of times or over. CONSTITUTION:An object 1 is picked up via a lens 2 by a camera 3, a pickup signal is processed by a picture processing circuit 3b in the camera 2 and a video signal 3a is outputted as an output signal and the picture of the TV signal of the NTSC or the PAL is displayed on a screen of a view finder 5 via an adder circuit 4. A camera operating signal or a signal such as synchronizing signal from a synchronizing signal generator 6 is inputted to the circuit 3a and a vertical synchronizing signal 11 is extracted from the signal from the signal generator 6 and inputted to a CPU 7. When the period of the synchronizing signal 11 is measured by the CPU 7 and the PAL or the NTSC system is discliminated from the signal 11 an when the discrimination is identical for a prescribed number of times or over, it is finally discriminated to be a TV signal of the NTSC or PAL system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discrimination circuit suitable for use in a video camera.

[Summary of the invention]

The present invention relates to a discrimination circuit suitable for use in a video camera,
A measurement means for measuring the period of the vertical synchronization signal, and whether the vertical synchronization signal is of the PAL system or not based on the output of the measurement means.
A first discriminating means for discriminating whether it is an SC system, and a vertical synchronizing signal system when the discriminating result of the first discriminating means becomes the same number of determinations for a predetermined number of times or more based on the output of the first discriminating means. By providing a second discriminating means that outputs a signal indicative of the above, the initial setup time of the camera is shortened.

[Conventional technology]

NTSC and PAL have traditionally been used as television systems.
A method has been proposed. As shown in Figure 4, the NTSC system has 525 scanning lines per frame, while the PAL system has 6 scanning lines/frame.
It is well known that 25 lines/frame are used.Also, as shown in Figure 3, the vertical blanking period between vertical synchronizing signals (11) is 16.66...11 in the NTSC system.
! In 9SPAL, it is 20n+s, so in general, to determine whether the system is NTSC or PAL, the time of this vertical retrace period can be measured using a microcomputer or the like.

In addition, in cameras, etc., a synchronization signal generator (hereinafter referred to as SG) is used to obtain the drive signal and synchronization signal necessary for camera scanning, and the frequency, pulse arrangement, and relative phase of various output waveforms are strictly controlled. is maintained. This SG has a synchronization coupling (genlock) function and is configured to obtain an output signal synchronized with an external video signal.

[Problem to be solved by the invention]

Conventionally, the method for determining whether a television signal is an NTSC or PAL television signal is to use a computer built into the camera to detect the vertical synchronization signal (11) from the SG at the start when the power is turned on. The period between
It was determined whether the signal was an NTSC or PAL television signal.

When the power is turned on with the SG genlocked in this way, even if the vertical synchronization signal (11) is output from the SG at a predetermined period as shown in Figure 3A,
A signal (13) that resets the vertical synchronizing signal (11) shown in FIG. 3C by the indefinite vertical synchronizing signal component of the external signal (12) as shown in FIG. 3B causes the microcomputer to output the vertical synchronizing signal The time t from the fall of the signal (11) to the fall of the reset signal (13) is measured. When such an error measurement is performed, for example, a camera or the like is used as a character generator as shown in FIG. Lower screen position (1
Even if you want to display characters (14) etc. on 0a), the NTS
In C and PAL systems, the number of scanning lines is 525/frame, 6
Since the number of lines is different from 25 lines/frame, there is a problem in that the character (14) is positioned too high on the screen (10b) or off the screen (10c). Therefore, by setting a certain delay time (usually about 1 second), the SG
Measurements were carried out after waiting until the genlock group of was stabilized. Because of this, it takes too much time to measure, and there was a problem in that the user had to wait about one second before turning the camera and starting drawing.

It is also possible to constantly measure the period between the vertical synchronization signals (11) during the main routine of the microcomputer, not when the power is turned on, but even in this case, if the SG is genlocked, the same problem as described above will occur. This has the disadvantage of causing

The present invention was made in view of the problem of ridges, and its purpose is to provide a discrimination circuit that can discriminate between NTSC and PAL television signals in an extremely short period of time. be.

[Means to solve the problem]

An example of the discrimination circuit of the present invention is shown in FIGS. 1 and 2, which includes a measuring means in a computer (7) that measures the period of a vertical synchronizing signal (11), and a measuring means of this measuring means. A computer (7) that determines whether the vertical synchronization signal (11) is a PAL system or an NTSC system based on the output.
and indicates the method of the vertical synchronization signal (11) when the discrimination result of the first discrimination means becomes the same number of discriminations for a predetermined number of times or more based on the output of the first discrimination means. The second determination means also within the computer (7) outputs a signal.

[Effect]

The discrimination circuit of the present invention measures the period of the vertical synchronizing signal (11) in the computer (7) (ST, )L, and then, based on this period measurement, determines whether the vertical synchronizing signal (11) is of the PAL system or the NTSC system. Based on the output of this determination, when the same determination is made more than a predetermined number of times, a determination (ST &) indicating the vertical synchronization signal format is performed, and the NTSC format or It is designed to determine whether the signal is a PAL television signal.

〔Example〕

Hereinafter, a case where the discrimination circuit of the present invention is applied to a camera device will be explained with reference to FIGS. 1 and 2.

Before explaining the flowchart of FIG. 1, the discrimination circuit of the camera device of the present invention will be explained with reference to FIG. In the figure, a subject (1) is imaged by a camera (3) through a lens (2).

The camera (3) includes an image processing circuit (3b), etc., a video signal (3a) is output as an output signal, and an addition circuit (4)
An image of a television signal such as NTSC or PAL is displayed on the screen of the viewfinder (5) through the screen.

A camera operation signal, a synchronization signal, etc. are sent to the image processing circuit (3b) in the camera (3) from a synchronization signal generator, that is, the 5G (6). This SC; (11) has a genlock terminal to which a video signal (3a) is supplied from the outside and is synchronized with a vertical synchronizing signal. The vertical synchronizing signal (11) is taken out from this S G (11) and sent to the microcomputer (
(hereinafter referred to as CPU) (7). CPU (7
) includes ordinary storage means such as ROM, RAM, and a timer (8), and has a timer function. CPU
In (7), pulse width measurement and the like are performed in which the period of the vertical synchronizing signal (11) is counted by a pulse train having a predetermined pulse interval.

The CPU (7) controls a character generator (hereinafter referred to as CG) (9) which outputs characters (14) etc. to be displayed on the viewfinder (5), and outputs a character video signal (9a). This character video signal (9a) is imaged by an adder circuit (4), and is, for example, an NTS
The periods of the video signal (3a) processed in the image processing circuit (3b) in C or PAL format and the vertical synchronization signal (11) are correctly synchronized, and the video signal (3a) and character video signal (9a) are added by an adding circuit (4), and characters (14) etc. are correctly superimposed on the screen of the viewfinder (5).

In the above-mentioned configuration, the determination operation for determining whether the system is an NTSC system or a PAL system in the CPU (7) will be explained with reference to the flowchart of FIG. In the first step ST+, the CPU (7) sets the count value to zero in order to measure the period between the vertical synchronizing signals (11) of the NTSC system, and in the second step STt, attempts to measure it. Set the count value n. If the number of measurements is actually performed five times, it is set to n:5.

In the third step STs, the CPU (7) uses the vertical synchronization signal (11) to measure the period of the vertical synchronization signal (11).
The time from the fall of signal 1) to the fall of the next vertical synchronization signal (11) is measured by a timer (8). At the time of measurement, 16.67m5 for NTSC method to 20m for PAL method
Select the middle time of m5 as the darkness value (SH), and set this SH>
If it is O, it is determined that the NTSC system is used, and if SH<O, it is determined that the PAL system is used. 4th step S
If it is determined that it is the vertical synchronizing signal period of the NTSC system at T, the NTSC system 〇 counter is incremented by +1 at the next fifth step STs. 4th step ST
, if it is determined that the PAL system is used, the process proceeds to the sixth step STb. In the sixth step STh, it is determined whether the NTSC count value is >.

That is, if the count value n=5 is set, when the count value reaches 3, it is determined that the NTSC system is used, and the process ends. That is, in this sixth step ST, measurements are performed at least three times.

At the 6th step ST, the NTSC count value is >
If not, proceed to the ninth step ST, and decrement the measurement count value by -1.

In the eighth step ST, if the measurement count value is n, the process returns to the third step ST and repeats the same measurement, but if not, it is determined that the PAL system is used and the process goes to the end. That is, according to the operation of the discriminating circuit of the present invention, the NTSC system or the PAL system is determined based on the majority decision of the results of each measurement.

According to the discrimination circuit of the present invention, the initial setup time in a camera device can be reduced to 1 second or less compared to the conventional one.

Note that the discrimination circuit of the present invention is not limited to the above-described embodiments, and can be used as a discrimination circuit for other video equipment that requires measuring the vertical synchronization signal period without departing from the gist of the present invention. Of course, various changes can be made to the range.

〔Effect of the invention〕

According to the discrimination circuit of the present invention, it is possible to obtain a PAL/NTSC system discrimination circuit which can shorten the initial setup time of the system, and has the effect of being able to measure the vertical synchronization signal period in a short time.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing one embodiment of the discrimination circuit of the present invention, FIG. 2 is a system diagram showing one embodiment of the discrimination circuit of the present invention, and FIG.
The figure is a waveform diagram illustrating a conventional vertical synchronizing signal, and FIG. 4 is a diagram illustrating a screen. (3) is a camera, (4) is an addition circuit, (5) is a viewfinder, (6) is an SG, (7) is a CPU, (8) is a timer, and is a CG. Agent Hidemori Matsukuma, fist, invention of a pig with a good-for-nothing mouth, fountain drawing, figure 2, burning east no *IL synonymous title, farm, figure 3, mountain drinking and drinking, figure 4

Claims (1)

[Scope of Claims] Measuring means for measuring the period of the vertical synchronizing signal; and first determining means for determining whether the vertical synchronizing signal is of the PAL system or the NTSC system based on the output of the measuring means. , a second discriminating means that outputs a signal indicating the type of the vertical synchronization signal when the discrimination result of the first discriminating means reaches a predetermined number or more of the same number of discriminations based on the output of the first discriminating means; A discrimination circuit characterized by comprising: