JPS62168472A - Video signal deciding device - Google Patents

Abstract

PURPOSE:To improve the accuracy for deciding whether a video signal exists or not, by measuring a pulse width of a vertical or horizontal synchronizing pulse, and also, measuring a cycle of the measured synchronizing pulse, and deciding whether its pulse is continued in a prescribed range or not. CONSTITUTION:A composite synchronizing signal applied to a terminal 1 is measured by a pulse width measuring means A and a cycle measuring means B, respectively. The pulse width measuring means A measures a pulse width of a vertical or horizontal synchronizing pulse in the composite synchronizing signal, and the cycle measuring means B measures a cycle of a pulse measured by the pulse width measuring means A, in the vertical or horizontal synchronizing pulse. Each measured value of the pulse width measuring means A and the cycle measuring B is supplied to a deciding means C and a storing means D, and compared with a pulse width and a cycle which have been set in advance, in said means. When both of them are continued in a prescribed range, it is decided that a supply of a video signal exists, and when they are out of the prescribed range, it is decided that there is no supply, and a deciding signal is outputted from a terminal 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal determining device, and more particularly, to a video signal determining device that determines whether or not a video signal is supplied.

2. Description of the Related Art Conventionally, there have been video signal synthesis circuits for displaying superimposed images on television images.

This video signal synthesis circuit is supplied with, for example, a main video signal received from a television broadcast, and an additional video signal from a personal computer or the like that is synchronized with this video display signal. The main video signal is replaced with an additional video signal and 1q of composite video signals are output only during the period when one character, one figure, etc. is displayed.

When such a superimposed display is performed, the personal computer continues to output additional video signals at all times, but the television receiver that receives television broadcasts may, for example, switch channels that are not being broadcast when changing channels. (for example, 5 channels),
The main video signal cannot be obtained. Furthermore, when a video tape recorder is used instead of a television receiver, the main video signal cannot be obtained if the video tape recorder is placed in stop mode.

In the composite video signal, the period representing a character, figure, etc. is replaced by an additional video signal, so the composite synchronization signal of the composite video signal is obtained from the main video signal. Therefore, as mentioned above, since there is no composite synchronization signal in the composite video signal when the main video signal is not supplied, there is a problem that the display screen based on the composite video signal becomes abnormal.

Therefore, the present applicant previously disclosed in Japanese Patent Application No. 59-209317 (title of the invention "Video Signal Determination Circuit") that the number of pulses of the main video signal during the existence period of the vertical synchronization pulse of the additional video signal is We proposed a circuit that counts and determines whether or not the main video signal is supplied based on the counted value.

Problems to be Solved by the Invention However, since the above-mentioned conventional circuit only counts the number of notches in the vertical synchronizing pulse of the main video signal, the determination accuracy is not satisfactorily high; Accuracy deteriorates when the S/N ratio of the signal deteriorates. Also,
In order to recognize the duration of the vertical synchronization pulse of the main video signal, an additional video signal that is synchronized with the main video signal and always exists stably is required, and judgment hunting occurs near the judgment value. There was a problem.

Therefore, the present invention provides a video signal determining device that solves the above problems by using a pulse width measuring means, a period measuring means, and a determining means, or a pulse width measuring means, a period measuring means, a determining means, and a storage means. The purpose is to

Means for Solving the Problems FIG. 1 shows the overall structure of the present invention. In the figure, a composite synchronizing signal separated from the supplied video signal enters terminal 1, and is supplied to pulse width measuring means A and period measuring means B, respectively. The pulse width measuring means A measures the pulse width of the vertical or horizontal synchronizing pulse in the composite domei signal, and the period measuring means B
measures the period of the synchronization pulse measured by the pulse width measuring means A among the vertical or horizontal synchronization pulses. The measured values of the pulse width measuring means A and the period measuring means B are supplied to the determining means C and the storage means, where they are compared with predetermined ranges of the pulse width and period, respectively, and are determined to be within the predetermined ranges. It is determined that the continuous video signal is being supplied, and when it is outside a predetermined range, it is determined that heat is being supplied, and a determination signal based on the determination result is output from the terminal 4.

Effects In the present invention, the presence or absence of a video signal supply is determined based on whether the pulse width and period of the vertical or horizontal synchronizing pulses are continuous within a predetermined range, so that the determination accuracy is improved.

Embodiment FIG. 2 shows a block system diagram of an embodiment of the present invention. In the figure, a composite synchronization signal as shown in FIG. 3, which is synchronously separated from a video signal received by a television receiver or reproduced by a video tape recorder or a video disc player, is input to terminal 1. This composite synchronization signal is determined by the determination device 3.
is supplied to the measurement terminal 3a. Note that when no video signal is supplied, this composite synchronization signal remains at a constant H level. An instruction signal indicating the field frequency of the video signal is input to the terminal 2, and is supplied to the type terminal 3b of the determination device @3. This instruction signal is, for example, a signal that is at H level when the field frequency of the video signal is 60 Hz, and is at L level when the field frequency is 50 Hz. The determination device 3 is, for example, a 1-chip microcomputer, and determines the pulse width and period of the vertical synchronization pulse of the supplied composite synchronization signal to determine the presence or absence of a video signal.
If I or nothing, a determination signal of ``0'' is output from terminal 4.

Next, the operation of the determination device 3 will be explained with reference to FIGS. 4 and 5. The determination device 3 executes the process shown in FIG. 4 when the power is turned on and at predetermined time intervals thereafter. In FIG. 4, the determination signal portion 5 before performing steps 5 and 6.7, in which the value Z of the determination criterion performed in step 23 is set from the storage means that stores the previous determination result, is changed from 1'' to 0''. When starting for the first time, it is set to “0”.
”. This will be explained later.

Next, set the decimal value “0” to variable 1 (step 1
0). Thereafter, the pulse width of the vertical synchronization pulse is determined (step 11). The operation of this pulse width determination is as shown in FIG.

In FIG. 5, the determination device 3 detects the level of the composite synchronization signal (step 30). In this level detection, the composite quantity +IIJ signal is sampled twice at an interval of 1X1, which is longer than the horizontal synchronizing pulse (valf 1'''/1-level period), for example, 6μSeC.This detection level is determined whether both times are at H level or not. It is determined in step 31 that even once L
If the level is detected, the process moves to step 30, and if 1 level is detected both times, the detected level is determined to be the H level, and the process moves to step 32. This prevents horizontal synchronization pulses and noise from being mistaken for vertical synchronization pulses. In step 32, timers N and N are both reset to zero. Thereafter, time measurement by timer M is started (step 33). This timer M is counted up every 50 μsec, for example, and is not shown in FIG. The time T1 from tl to tl is measured.

After this, the determining device 3 detects the composite synchronizing signal level again (step 34). This level detection is also done in step 30.
Similarly, sampling is performed twice at an interval of, for example, 6 μsec, which is longer than the 1-level period of the horizontal synchronizing signal. It is determined whether this detection level is L level both times (
Step 35), if the level is H at least once, NO 6
Detected when both are at L level ・Determined to be at L level and step 37! −・・ Do. In step 36, the level of the instruction signal is determined, and when it is at the H level, it is determined whether the count value of timer M exceeds the period 16, 7n5eck, or a value corresponding to the field frequency 601-1z.Step 38 )
, when the timer M is at the L level, it is determined whether the measured value of the timer M exceeds a value corresponding to a period of 20 m5ec with a field frequency of 50 Hz (three steps). Step 38
Alternatively, if the counted value of timer M is determined to be small in step 39, the process moves to step 34, and if it is determined to be large, the process moves to step 40, where it is assumed that there is no vertical synchronizing pulse, and 11111 indicating an abnormality is set in the status flag. Then, the process shown in FIG. 5 is completed.

In step 37, timer N starts counting time.

This timer N is counted up every 10 μsec, for example, and the time T1 from time t1 to tl in FIG.
2. Measure the pulse width of the vertical synchronization pulse. Thereafter, in step 41, the level of the composite synchronization signal is detected. This level detection is also performed in the same way as in step 30, for example, 6μSQQ.
Sampling is performed twice at an interval of . It is determined whether this detection level is 1-level twice (step 42), and if it is L level even once, the process moves to step 41, and if both times are H level, the detection level is H level. It is determined that this is the case, and the process moves to step 43. Step 43
Then, the count value of timer N is the pulse width of the vertical synchronization pulse (=
3 horizontal scanning periods)? 50μsec to 20
It is determined whether the value corresponds to the range up to 0 m5ec. Here, if the condition of step 43 is not satisfied, the process moves to step 40, and if it is satisfied, the process moves to step 44, where "'○" indicating normality is entered in the status flag, and the process shown in the fifth figure ends. do.

Returning to FIG. 4, when the above pulse width determination (step 11) is executed, it is determined whether the value of the status flag is IIO11 (step 12).

Here, when the value of the status flag is O°, the process moves to step 13, where the period of the vertical synchronization pulse is measured, and II 1
When it is IT, move to step 14 and set the value P0° from the terminal.
' is output, and the process shown in FIG. 4 is completed. In step 13, timer M is reset to zero, and then timer M starts counting (step 15). Furthermore, composite synchronization signal level detection is performed (step 16). Similarly to step 30, this level detection is also sampled twice at intervals of, for example, 6 μSaC. This detection level is 2 [that is L
It is determined whether or not the level is 1 (step 17).
If the detection level is "i" level twice, the process moves to step 18, and when both times are at the L level, it is determined that the detected level is the L level, and the process moves to step 19. In step 18, the count value of timer M is sufficiently larger than the period (=20 msec) of the vertical synchronizing pulse with a field frequency of 50 Hz.
It is determined whether the count value exceeds a value corresponding to 3,5 m5ec, and if this count value is small, the process moves to step 16, and if it is large, it is determined that no vertical synchronizing pulse is detected, and the process moves to step 14.

In step 19, the level of the instruction signal is determined, and when it reaches level 14, the counted value of timer M includes an error in the period 16.7 m5ec of field frequency 60 Hz.
It is determined whether the value corresponds to the period from 15.5m5ec to 17.5m5ec (step 20).
). Here, if the conditions of step 20 are not satisfied, the process moves to step 14 and outputs a determination signal of value "O",
If satisfied, the process moves to step 22. Further, if the instruction signal is determined to be at L level in step 19, the timer M
The count value is around IFI 2 with a field frequency of 50 Hz.
Period including error in 0 m5ce 19 m5ce to 2
It is determined whether the value corresponds to the range up to 1 m5ac (step 21).

If the conditions of step 21 are not satisfied, the process proceeds to step 14 and a determination signal of value 110 II is output.
If satisfied, the process moves to step 22.

In step 22, the value of variable i is incremented by "1". Next, it is determined whether the value of variable 1 is greater than or equal to "Z" (step 23), and if not satisfied, the process moves to step 11 and steps 11 to 22 are repeated. As a result, if step 20 or step 21 is repeated seven times and is satisfied, the process moves from step 23 to step 24, where a determination signal of value It 1 II is output from terminal 4, and the process shown in the fourth diagram ends. do.

In this way, the number of loops to stabilize the judgment signal (variable 1 in step 22) is determined by the stability of the judgment signal output and the judgment response. Hunting occurs. For example, if a video signal obtained in a weak electric field where the video signal can barely be received is input to this determination device, it will be determined that there is a signal at one moment and no signal at another moment. Therefore, returning to the steps in FIG. 4, the value of the criterion Z used in step 23 is changed depending on the state of the storage means in which the previous determination result is stored. Specifically, if it is judged that there is a signal, the Iff of the judgment criterion Z is
Decrease f and set it to al, for example, set it to 4, and make a judgment of 11<
Rir. On the other hand, when determining the number of lines from a state with no signal to a state with a signal, the value of Z is increased to al, for example, 6 to make it more difficult. However, aQ, al is aQ>a
It is a natural number related to l. By doing this,
As long as the signal does not change significantly, the judgment result can be stably obtained under any signal condition, and a high-quality judgment result can be obtained. In this way, the pulse width of the vertical synchronizing pulse of the vertical synchronizing signal is determined in steps 32 to 44 in FIG.
In steps 13.15 to 23 shown in the figure, the period of the vertical synchronizing signal is determined, and based on the determination result of the pulse width and period 1111, it is determined whether or not the video IgA signal is supplied. Therefore, the determination accuracy is improved compared to the conventional method. Also step 1
Since the level is determined based on the level detected twice at a predetermined interval in 7.31.35.42, highly accurate determination can be made even when the SN ratio of the video signal is degraded. Further, this determination only requires a composite synchronization signal separated from the video signal, and does not require an additional video signal as in the conventional art.

In the above embodiment, the pulse width and period of the vertical synchronization bus in the composite signal are determined to determine whether or not a video signal is supplied. The determination may be made based on the following information. In this case, the interval between two level detections in steps 17, 31, 35, and 42 is equal to the pulse width of the horizontal synchronizing pulse (
- It is necessary to set the time to about 1 μsec, which is sufficiently smaller than 4μ5ec).

Note that in the above embodiment, timers M and N are used to measure time, but it is also possible to consider that the execution time of each instruction step on the program is approximately the same, and to measure the time by counting the number of executed instruction steps. It is not limited to the above embodiments.

In the above embodiment, the field frequency is 50Hz or 60Hz.
Although the explanation has been made assuming that a Hz video signal is input, if only one of the video signals is input, there is no need to supply the instruction signal from the terminal 2 to the determination device 3.

Effects of the Invention As described above, the video signal determining device according to the present invention determines whether or not a video signal is supplied based on how many consecutive times the pulse width and period of a vertical or horizontal synchronizing pulse are within a predetermined range. This improves the judgment accuracy of the video signal, eliminates the need for an additional video signal as in the past, and determines the detection level when the sampled signal levels match consecutively. High M degree can be determined even if the S/N ratio is degraded, and furthermore,
Since the state of the previous input signal is memorized and the judgment conditions are changed depending on the state, it has the advantage that a judgment result can be stably obtained regardless of the signal state.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of the present invention, FIG. 2 is a block system diagram of an embodiment of the apparatus of the present invention, and FIG. 3 is a diagram showing the overall configuration of the present invention. FIG. 6 is a waveform diagram of a composite synchronization signal, and FIGS. 4 and 5 are flowcharts for explaining the operation of the determination device shown in FIG. 2. 1.2.4...terminal, 3...judgment device, 5~7゜1
0 to 24.34 to 44...Step, A...Pulse width measuring means, B...Period measuring means, C...Judgment means, D...Storage means, M, N...Timer , Z...predetermined number of times. Figure 1 Δ Figure 2 Figure 3 Figure 6

Claims (2)

[Claims] (1) Pulse width measuring means for measuring the pulse width of a vertical or horizontal synchronizing pulse included in a video signal, a period measuring means for measuring the period of the vertical or horizontal synchronizing pulse, the pulse width measuring means and the period measuring means It is determined that the video signal is being supplied when the measured values are within the predetermined ranges of the predetermined pulse width and period and are obtained consecutively a predetermined number of times Z, and each of the measured values is within the predetermined range. 1. A video signal determining device comprising: determining means for determining that the video signal is not supplied when the video signal is outside the range. (2) A pulse width measuring means for measuring the pulse width of a vertical or horizontal synchronizing pulse included in a video signal, a period measuring means for measuring the period of the vertical or horizontal synchronizing pulse, the pulse width measuring means and the period measuring means It is determined that the video signal is supplied when the measured values are within a predetermined range of each predetermined pulse width and period and are obtained a predetermined number of times Z, and each of the measured values It is constituted by a determining means that determines that the video signal is not supplied when it is outside a predetermined range, and a storage means that stores the output of the determining means, and when the storage state of the storage means is that there is no video signal, Z The value of a_0,
When there is a video signal, the value of Z is a_1 (however, a_0, a
1. A video signal determining device characterized in that the determination criterion is varied depending on the storage state by changing the value of Z so that _1 is a natural number such that a_0>a_1.