JPH0134512B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention is directed to a television receiver that receives composite video signals of different formats such as NTSC, PAL, or SECAM, or a video tape recorder (hereinafter referred to as VTR) that records and plays back composite video signals of different formats such as NTSC, PAL, or SECAM. ) or a video disc (hereinafter referred to as VD) as a playback device, relates to an automatic television broadcast system discrimination method for automatically determining whether the above-mentioned NTSC signal is being received or played back.

(b) Prior art In a conventional television receiver or VTR, etc., the composite video signal received or reproduced is, for example,
Depending on whether the system is NTSC or PAL, you can use a TV receiver or VTR designed for each broadcasting system, or equip one TV receiver or VTR with a circuit that can receive or play back both systems. This was extremely inconvenient, especially in areas where both types were used, as the switch had to be changed each time.

(c) Purpose of the Invention The present invention provides the above-mentioned method from a composite video signal when reproducing a signal received or recorded from a plurality of television broadcasting systems having different numbers of horizontal scanning lines or field frequencies, such as the NTSC system or the PAL system. An object of the present invention is to provide an automatic discrimination method for television broadcasting methods that can automatically determine which method is used among the TV broadcasting methods.

(d) Structure of the invention A signal having a horizontal synchronizing signal frequency or an integral multiple thereof is frequency-divided, and the first frequency-divided output signal is transmitted during a period in which the first vertical synchronizing signal of the first broadcasting system is expected to arrive. a counter that generates a second frequency-divided output signal during a period in which the second vertical synchronization signal of the second broadcasting system is expected to arrive; a vertical synchronization signal generation circuit that generates a vertical synchronization signal, a first AND gate that performs an AND of a first frequency-divided output signal of the counter, and a vertical synchronization signal from the vertical synchronization signal generation circuit; a second AND gate that performs an AND of the frequency-divided-by-2 output signal and the vertical synchronization signal from the vertical synchronization signal generation circuit;
and holding means for holding the values of the output signals of the first and second AND gates, and the television broadcast system is determined based on the output of the holding means.

(E) Embodiment FIG. 1 is a block diagram showing an automatic discrimination method for television broadcasting systems of the present invention, and FIG. 2 is a waveform diagram for explaining FIG. 1.

Next, the present invention will be explained according to the drawings. In FIG. 1, 1 is a clock signal generation circuit, 2 is a counter, 3 is a vertical synchronization signal generation circuit, 4 is a gate circuit having AND gates 5 and 6, and 7 is a flip-flop. (F/F), etc., 8 and 9 are discrimination output terminals, and 10 is an OR gate. In Figure 2, A is the output waveform of the clock signal generation circuit, B and D are the output waveforms of the vertical synchronization signal generation circuit derived from composite video signals of different systems, for example, NTSC and PAL systems, and C and H are the output waveforms of the vertical synchronization signal generation circuit. Output waveforms of the counters corresponding to B and D, F and G are output waveforms of the memory 7,
1 shows the input waveform of the OR gate 9 connected to the counter 2.

First of all, NTSC and PAL are examples of broadcasting systems.
To explain the system in detail, the output _VH of the clock signal generating circuit 1 shown in FIG. 1 appears as shown in FIG. 2A and is added to the counter 2.

At this time, if the vertical synchronization signal from the vertical synchronization signal generation circuit 3 is derived from an NTSC composite video signal, the period is 1/60 seconds and the counter 2
counts the pulses of the clock signal V _H by
Since the number of horizontal scanning lines is 525/2 per field, the output of counter 2 is, for example,
If it is set to occur between 256 and 272 (n ₁ = 256, _{2 2} = 272), the vertical synchronization signal V _V in the received signal or reproduced signal will exist during this period, and the result will be shown in Figure 2 C. The counter 2 is reset at the timing shown (n _0th line), and the output of the waveform shown by the solid line in FIG. 2C is obtained from the counter 2. Along with this, the output shown in FIG. appears.

On the other hand, if the vertical synchronization signal from the vertical synchronization signal generation circuit 3 is derived from a PAL system composite video signal, the period is 1/50 seconds and the pulses of the clock signal V _H are counted by the counter 2. Since the number of horizontal scanning lines is 625/2 per field, the output of the counter 2 is, for example, 300 to 325.
(n ₁ ′ = 300, n ₂ ′ = 325), the vertical synchronization signal V _V in the received signal or reproduced signal exists during this period, as shown in Figure 2 D. Reset counter 2 at the timing (n ₀ 'th),
Therefore, the waveform is shown by the solid line in FIG. 2E. Accordingly, the waveform shown in FIG. 2G is obtained as the output of the memory 7.

Note that if the vertical synchronization signal V _V does not arrive at the relevant timing of the NTSC system or PAL system (missing in either case), the output of counter 2 will be the second one.
In this case, the output V _A of counter ₂ (OR
A reset is applied via gate 10.

The voltage V _N (second
Figure F) appears as a control voltage for NTSC, and at this time terminal 9 remains at a low level, while voltage V _P appearing at terminal 9 (Figure 2 G) appears as a control voltage for PAL, and at this time terminal 9 remains at a low level. 9 is kept at a low level, and the control voltage V _N or
_VP automatically sets the NTSC or
You can switch to PAL format.

The above-mentioned clock signal generation circuit may be a dedicated circuit such as a VTR or video camera, which uses its own oscillation circuit instead of using television broadcast waves.
Like a television receiver, it may be equipped with a synchronization separation circuit and use its output.
I explained examples of NTSC and PAL systems, but
The same is true for discrimination with the SECAM method.

(F) Effects of the Invention According to the automatic television broadcast system discrimination system of the present invention, if the system of the received broadcast wave or composite video signal recorded on a magnetic tape etc. is, for example, NTSC system or
It is possible to detect the difference in the number of scanning lines of the PAL system, ie, 525 lines and 625 lines, and the difference in the vertical period, ie, 1/60 second and 1/50 second, and achieve the desired purpose with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an automatic discrimination system for a television broadcasting system according to the present invention, and FIG. 2 is a waveform diagram of each part in FIG. 1. Explanation of main drawing numbers, 1...Clock signal generation circuit,
2...Counter, 3...Vertical synchronization signal generation circuit, 4...
Gate circuit, 7...memory.

Claims (1)

[Claims] 1 Divide the frequency of the horizontal synchronization signal frequency or a signal with a frequency that is an integer multiple thereof, and generate the first frequency-divided output signal during the period in which the arrival of the first vertical synchronization signal of the first broadcasting system is expected; A counter that generates a second frequency-divided output signal during a period when the second vertical synchronization signal of the broadcasting system is expected to arrive, and a vertical synchronization signal that is used to reset the counter in correspondence with various broadcasting systems. a vertical synchronization signal generation circuit, a first AND gate that takes an AND of a first frequency-divided output signal of the counter and a vertical synchronization signal from the vertical synchronization signal generation circuit, and a second AND gate of the counter;
a second AND gate that performs a logical product of the frequency-divided output signal and the vertical synchronization signal from the vertical synchronization signal generation circuit; and a holding means for holding the values of the output signals of the first and second AND gates; An automatic determination method for a television broadcasting method, characterized in that the television broadcasting method is determined based on the output of the holding means.