JPH02195788A - Nonstandard signal discrimination circuit - Google Patents

Abstract

PURPOSE:To surely perform the discrimination of a nonstandard signal by detecting phase relation between a horizontal synchronizing signal and a chrominance subcarrier. CONSTITUTION:A monostable multivibrator 19 at a preceding stage to which a signal of four fields synchronized with the horizontal synchronizing signal is inputted decides the phase detecting positions of the chrominance subcarrier at phase detection circuits 11, 12 and 15, 16. The output Q of the monostable multivibrator is supplied to the clocks of FFs 11 and 12, and the output Q to that of FFs 15 and 16. Therefore, the phase detecting positions of the chrominance subcarriers at the FFs 11 and 12 are deviated from that of the FFs 15 and 16. The input and output of the FF 12 are sent to a monostable multivibrator 14 via an EXOR gate 13, and that of the FF 16 to a monostable multivibrator 18 via an EXOR 17, respectively, and by sending the output of each monostable multivibrator to an AND gate 20, the nonstandard signal can be discriminated from a standard signal corresponding to respective output.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a non-standard signal discrimination method for detecting whether the phase relationship of color subcarriers in each predetermined field of an arbitrarily given PAL color video signal is asynchronous or not. It is related to circuits.

BACKGROUND OF THE INVENTION PAL color video signals, which are generally called PAL color video signals, are roughly divided into two types: standard signals and non-standard signals.

In the former case, the standard signal is one in which the horizontal synchronization signal, vertical synchronization signal, and color subcarrier have no temporal jitter and are expressed by equation (1), (
2) Refers to a signal that satisfies the relationship of formula.

625 X f H = 2 X f v
-(2) fsc: Frequency of color subcarrier fH: Frequency of horizontal synchronizing signal fv: Frequency of vertical synchronizing signal For example, camera output, output of T2O to eliminate time axis fluctuation of VTR, output of composite motion signal generator etc. are the standard signals mentioned above.

Next, the latter non-standard signal refers to a signal in which the horizontal synchronization signal, vertical synchronization signal, and color WJJ carrier wave have time axis fluctuations and do not satisfy the relationship of equation (1).

For example, the playback output of a VH8 system or β system VTR,
The playback output of a 374-inch VTR corresponds to the aforementioned non-standard signal.

Therefore, VTRs, video switchers, etc. that handle video signals have no choice but to accept the same level of input as standard signals and non-standard signals as described above coexist.

Therefore, equipment that handles video signals is equipped with an input switch that manually selects whether the input signal is a standard signal or a non-standard signal, but the market demand is that an automatic discrimination device for determining whether the video signal is a non-standard signal is required. It is desired that the system be installed in equipment that handles.

Against this background, a circuit as shown in the block diagram of FIG. 5 is known as a circuit for discriminating non-standard signals. In FIG. 5, the synchronization separation circuit 1 has an input video signal a
Separate the horizontal synchronization signal from the horizontal synchronization signal. The loop including the phase comparator 2, amplifier 3, voltage controlled oscillator 4, and frequency divider 5 is synchronized with the horizontal synchronization signal of the input video signal a by n times (n
This is a PL loop for generating a signal C with a frequency n fH (integer), and is a block often installed in VTRs. Using this PLL loop, the movement of the voltage d that controls the voltage controlled oscillator 4 is controlled by the two voltage comparators 6 and 7.
I am trying to determine whether the signal is a non-standard signal by using These two voltage comparators 6.7 each have an upper limit value and a lower limit value for the voltage, and when either threshold value is exceeded, the signal is determined to be a non-standard signal via the OR circuit N8. There is. That is, when the input video signal @a is a standard signal, the horizontal synchronization signal has no time axis fluctuation, so the voltage d that controls the voltage controlled oscillator 4 in the PLL loop is stable, so the two voltage comparators 6 , 7 will not be exceeded. On the other hand, when the input video signal a is a non-standard signal, the horizontal synchronization signal also has time axis fluctuations, so the input voltage d of the voltage comparator 6.7 fluctuates due to the phase fluctuation of the horizontal synchronization signal. , the threshold value of either of these two voltage comparators 6.7 is exceeded, and it can be determined from the output of the OR circuit 8 that it is a non-standard @ number. For VTR playback signals, turn off the head! ! Sometimes a large skew occurs, and this phase error must be detected.

Problems to be Solved by the Invention In the above-mentioned conventional non-standard signal discrimination circuit, the horizontal synchronization signal @
eJ-axis fluctuations are converted into voltage and whether or not the signal is a non-standard signal is detected from the voltage fluctuations, so the setting of thresholds in voltage comparators etc. becomes delicate. Moreover, the time axis fluctuation of the VTR's self-recording and playback signal may be extremely small.
This has the problem that non-standard signals may be misidentified.

The present invention solves such conventional problems and provides a non-standard signal discriminating circuit that enables reliable discrimination of non-standard signals by detecting the phase relationship between the horizontal synchronization signal and the color IaWI transmission wave. The purpose is to

Means for Solving the Problems In order to solve the above 1IW1, the non-standard signal discrimination circuit of the present invention includes a first phase detection circuit that detects the phase of a color subcarrier for each predetermined field of a PAL color video signal; a first means having a circuit for detecting whether the phase relationship of the color subcarriers detected by the first phase detection circuit is constant; color 1
iiiJIIi A second phase detection circuit that detects the transmission phase at a position shifted from the transmission phase detection position, and a circuit that detects whether the phase relationship of the color subcarrier detected by the second phase detection circuit is constant. The apparatus includes a second means, and a means for determining a non-standard signal when both the first means and the second means detect that the phase relationship of the color printing carrier wave is shifted.

Operation With the above configuration, the first means detects that the phase relationship of the color subcarriers is not constant and changes for each predetermined field of the PAL color video signal, and the second means detects that the phase relationship of the color subcarriers of the first means is changed. It is detected that the phase relationship of the color subcarrier detected shifted from the phase detection position is not constant and has changed, and in this way both the first and second means detect that the phase relationship of the color subcarrier is constant. When a deviation is detected, the signal is determined to be a non-standard signal. In this case, the color 1itJI for each predetermined field, for example every 4 fields, etc.
To determine whether the phase relationship of the transmitted waves is out of alignment, it is sufficient to use only the first means, but when the phase detection of the color subcarrier is configured with a digital circuit, the horizontal synchronization signal and the color subcarrier Since there is a risk of erroneous detection in a standard signal whose phase is shifted, a second means is provided to prevent erroneous detection.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a non-standard signal discrimination circuit showing one embodiment of the present invention. As shown in FIG. 1, there are cascade-connected D flip-flops 11.12 that detect the phase of the color subcarrier signal A every four fields, and the phase relationship between the color IJII transmission from the outputs of these D flip-flops 11.12. an EXCLUSIVE-OR gate 13 for detecting fluctuations in
(7) EXCLUSIVE-OR'7''-G13 output is input to ridrigger mono multi 14 with a long time constant.
and other cascade-connected D flip-flops 15 and 16 for detecting the phase of the color subcarrier at a position shifted from the color subcarrier phase detection position of the first means, and these D flip-flops. 15. EX that detects fluctuations in the phase relationship of color subcarriers whose positions are shifted from the output of 16.
The CIIISJVE-OR gate 17 and the ridrigger monomulti 18 constitute a second means.

The monomulti 19 at the front stage to which the 4-field signal synchronized with the horizontal synchronization signal is input is connected to the first phase detection circuit 11.1.
2 and the phase detection position of the color subcarrier in the second phase detection circuit 15 and 16, and the monomulti 19
The Q output of the D flip-flop 11 and 12 is connected to the a link input terminal, and the Q output is connected to the D flip-flop 15 and 16.
By supplying the signal to the clock input terminal of , the all-color transmission phase detection positions of the D flip-flop 11.12 and the D flip 70 knob 15.16 are shifted. Further, in order to prevent false detection when inputting a standard signal, the time constant of the monomulti 19 must meet the following conditions.

However, n is an integer satisfying n≧O.

Further, an AND circuit 20 is provided to which the outputs of the monomulti 14 of the first means and the monomulti 18 of the second means are input, and the output of the AND circuit 20 discriminates between a standard signal and a non-standard signal. .

Next, various input conditions will be assumed and explained with reference to the timing diagrams of FIGS. 2, 3, and 4.

FIG. 2 shows an example when a standard signal is input. Second
In the figure, the phases of the color subcarrier signals A and B of the (n-4) field and the n field are changed to the rising edge C1 and the falling edge C of the sample pulse C output from the monomulti 19.
Detect with 2. In the example shown in Fig. 2, the phases of the color subcarrier signals @A and B for every 4 fields are inverted with respect to each other when detected at the rising edge C1 and when detected at the falling edge C2. and EXCLU of the second means
SIVE-OR gate 13.17 (7) Maintain the output level. Therefore, Ridriger Mono Multi 14.
Since both signals 18 and 18 are not triggered, the output of the AND circuit 20 is at a high level and outputs an output that is determined to be a standard signal.

FIG. 3 shows another example when a standard signal is input.

In FIG. 3, the rising edge C of sample pulse C'
1' coincides with the rising edge Eh' of the n-field color subcarrier signal B' and the falling edge A2' of the (n-4) field color subcarrier signal A'. At this time, the set-up time (
If the position does not satisfy the data retention time (data retention time), even if the phase relationship between sample pulse C' and color subcarrier signals A' and 8' is constant, EXC
The output of the LUSIVE-OR gate 13 indicates a high level or a low level. Therefore, EX
CLUSIVE-OR/7”-to13 output fluctuates,
As a result, a trigger is given to the ridrigger monomulti 14, and the signal is determined to be a non-standard signal. However, in the phase detection of the second means, since the condition of equation (3) described above is satisfied, the color subcarrier signals A' and B' are '
- The output of the gate 17 (7) does not change, and the redrigger monomulti 18 is not triggered. Therefore, the output of the AND circuit 20 is determined to be a standard signal. Therefore, by providing the second means, no matter where the phase relationship between the sample pulse C' and the color subcarrier signals A' and 8' is, they can be stably distinguished from the standard signal, and erroneous detection can be prevented. .

Next, FIG. 4 shows an example when a non-standard signal is input. At this time, the correlation between the horizontal synchronization signal and the color subcarrier disappears, and the fact that the phase relationship cannot be maintained is detected at both the rising edge C1" and the falling edge C2" of the sample pulse C#, and the Ridrigger monomulti 14.18 Both of them operate, and the AND circuit 20 outputs a low level signal, which is determined to be a non-standard signal.

At this time, if the frequency of the horizontal synchronization signal and the color subcarrier are only slightly different, phase shift detection will rarely be possible, so the time constant of the Ridrigger Mono Multi 14.18 must be set sufficiently long. be.

Note that in this embodiment, the phase of the color subcarrier is detected every 4 fields to discriminate non-standard signals, but it is also possible to detect the phase of the color subcarrier every 8 fields to discriminate non-standard signals. You can also do it.

Effects of the Invention As described above, according to the non-standard signal discriminating circuit of the present invention, regardless of the time axis fluctuation of the horizontal synchronization signal, non-standard signals can be discriminated extremely stably only by detecting the phase of the color subcarrier. This method is extremely advantageous in practical terms because wJU is not required. In addition, digital tC
It is also possible to configure it more easily.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a non-standard signal discriminating circuit showing an embodiment of the present invention, FIGS. 2 and 3 are timing waveform diagrams when a standard signal is input to the non-standard signal discriminating circuit, and FIG. FIG. 4 is a timing waveform diagram when a non-standard signal is input to the non-standard signal discriminating circuit, and FIG. 5 is a block diagram of a conventional non-standard signal discriminating circuit. 11.12, 15.16...D flip 70 knobs, 1
3.17...EXCLIISIVE-OR/7" -
To, 14.18.19-+ /? At'l-12
0...AND circuit. Agent Yoshihiro MorimotoFigure 2Figure 3'F'1 Male exit η 4 Figure 4

Claims (1)

[Claims] 1. a first phase detection circuit that detects the phase of a color subcarrier for each predetermined field of a PAL color video signal;
a circuit for detecting whether the phase relationship of the color subcarriers detected by the phase detection circuit of the first means is constant; A second phase detection circuit that detects a phase shifted from a phase detection position and a circuit that detects whether a phase relationship between color subcarriers detected by the second phase detection circuit is constant. means, and when both the first means and the second means detect that the phase relationship of the color subcarriers is shifted,
A non-standard signal discrimination circuit equipped with a means for discriminating a non-standard signal.