JPH1146311A - Automatic gain adjustment circuit and monitor for game machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically adjust the level of a video signal received from a signal source to a correction level, even if the signal source generating the video signal of the JAMMA standards is changed. SOLUTION: A data latch circuit 4 latches digital data which are maximum values among video signals 100 held by a peak level hold circuit 2. A comparator 5 compares the maximum value of the video signals 100, latched at this time with a maximum value of the preceding video signals 100 having been latched by a MAX latch circuit 6. When the maximum value this time is larger than the preceding maximum value, the maximum value this time is latched by the MAX latch circuit 6. The maximum value of the video signal 100 latched by the MAX latch circuit 6 is converted into an analog signal by a D/A converter circuit 10, and the level is shifted by a level shift circuit 11 and the result is given to an attenuator 12. The attenuator 12 attenuates the level of the video signal 100 at an attenuation rate, in response to the maximum value of the video signal 100 to set the level to be a correct level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic gain adjustment circuit for automatically adjusting the level of a video signal of the JAMMA standard to an appropriate level and inputting it to a video processing circuit, and for a game machine equipped with this automatic gain adjustment circuit. About the monitor.

[0002]

2. Description of the Related Art The JAMMA standard applied to amusement equipment used in the amusement industry has no standard regarding the level of a video signal, and the signal level of each company varies. Therefore, the level of the video signal is also 0.7
５5v (pp), which varies from company to company. Therefore, J
Plays back AMMA standard video signals and displays them on the screen. For example, in the case of a game machine monitor, each time the signal source changes, the input level is adjusted to an appropriate level according to the level of the video signal, and then the video processing of the monitor is performed. Supply to the circuit.

FIG. 3 is a block diagram showing a configuration example of a conventional gain adjustment circuit for adjusting the input level of the above-mentioned JAMMA standard video signal to an appropriate level. The video signal is input to the attenuator 31. The adjuster operates the variable resistor (VR) 33 while monitoring the oscilloscope 32 connected to the output side of the attenuator 31. When the variable resistor (VR) 33 is operated, the divided voltage of the + B voltage changes, and this divided voltage is supplied to the attenuator 31. The attenuator 31 attenuates the level of the input video signal 100 at an attenuation rate corresponding to the divided voltage and outputs the resulting signal. Manually adjust the variable resistor (VR) 33 and set the attenuator 3
The oscilloscope 32 confirms that the video signal adjusted to an appropriate level from 1 has been output, and ends the adjustment.

FIG. 4 is a block diagram showing another example of the configuration of a conventional gain adjustment circuit for adjusting the input level of the above-mentioned JAMMA standard video signal to an appropriate level. In this example,
The attenuator 31 is connected to a plurality of fixed resistors R1 to Rn, switches S1 to Sn for connecting one end of each of the fixed resistors R1 to Rn to a + B voltage line, and a resistor R0. The coordinator turns on any of the switches S1 to Sn. For example, when the switch S1 is turned on, the + B voltage is divided by the resistors R1 and R0, and the divided voltage is input to the attenuator 31. The attenuator 31 attenuates and outputs the level of the input video signal 100 at an attenuation rate corresponding to the divided voltage. In this case, the switches S1 to S
Since the attenuation factor of the attenuator 31 is set in advance for n, a video signal adjusted to an appropriate level can be obtained without an oscilloscope.

[0005]

As described above, the JAM
In the MA standard, each time the signal source for supplying the video signal changes, the adjuster manually switches the attenuator 31 with the switches S1 to S1.
After adjusting the video signal to an appropriate level by selecting Sn or operating the variable resistor 3, it is necessary to input the video signal to, for example, a monitor for a game machine, and the adjustment requires technical skill. However, not everyone can do it, and there is a problem that labor and labor costs are required.

Accordingly, the present invention has been made to solve the above problems, and even if the signal source of the JAMMA standard is changed, the level of the video signal input from the signal source is automatically adjusted to an appropriate level. It is an object of the present invention to provide an automatic gain adjustment circuit capable of quickly and accurately adjusting the input to a video device and a monitor for a game device equipped with the automatic gain adjustment circuit and having improved operability.

[0007]

According to a first aspect of the present invention, there is provided a level detecting means for detecting and holding a maximum level of an input video signal, and corresponding to the maximum level of the video signal detected by the level detecting means. Control signal generating means for generating a control signal of a predetermined level, and an attenuation rate corresponding to the level of the control signal generated by the control signal generating means, and the input video signal is attenuated at this attenuation rate. And a level attenuating means for outputting the output.

With such a configuration, even if the level of the input video signal changes, the maximum level of the video signal is detected and held by the level detecting means. The control signal generating means generates a control signal having a level corresponding to the detected maximum level of the video signal, and the control signal sets the attenuation rate of the level attenuating means in accordance with the maximum level of the video signal. Therefore, the level attenuating means attenuates the level of the input video signal at the set attenuation rate, adjusts the level to an appropriate level, and outputs the adjusted level to the video equipment.

According to a second aspect of the present invention, the control signal generating means has a configuration for generating the control signal after a lapse of a predetermined time from the input of the video signal.

With this configuration, the maximum level of the input video signal is detected and held by the level detection means during the predetermined time, so that the level attenuating means can detect the maximum level of the input video signal in accordance with the maximum level of the input video signal. Is set at 1 degree.

According to a third aspect of the present invention, the level detecting means has a configuration which is reset when the power is turned on.

According to a fourth aspect of the present invention, the video signal is a JAMM
It has a configuration that is a signal of the A standard.

According to a fifth aspect of the present invention, the level attenuating means includes an attenuator.

According to a sixth aspect of the present invention, there is provided an automatic gain adjustment circuit according to any one of the first to fifth aspects, and a video signal to which a video signal whose level has been adjusted by the automatic gain adjustment circuit is input and subjected to various processes. There is provided a configuration including a processing circuit and display means for displaying a video signal processed by the video signal processing circuit.

With this configuration, the video signal adjusted to an appropriate level by the automatic gain adjustment circuit is input to the video signal processing circuit regardless of the type of signal source.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the automatic gain adjustment circuit of the present invention. Reference numeral 1 denotes a pedestal clamp unit for DC-reproducing the video signal 100. Reference numeral 2 denotes a peak value hold circuit that holds the maximum value of the video signal input during one vertical synchronization period. Reference numeral 3 denotes a digital value of the peak value held by the peak value hold circuit 2. A / to convert to signal
A D conversion circuit 4, a data latch circuit (memory) for latching a digital signal output from the A / D conversion circuit 3;
Is the data latched by the data latch circuit 4 and MA
A comparator for comparing the data latched by the X latch circuit 6; a MAX latch circuit 6 for latching the maximum value of the data latched by the data latch circuit 4; AND circuit for calculating the logical product of the AND operation, 8 a counter for counting the vertical synchronization signal, 9 an inverter for inverting the output of the counter 8, 1
0 is a D / A conversion circuit that converts the data held in the MAX latch circuit 6 into an analog value, 11 is a level shift circuit that converts the level of the analog value output from the D / A conversion circuit 10, and 12 is a video signal 100 The attenuator 13 attenuates the level and outputs a signal.
Reset circuit.

Next, the operation of this embodiment will be described. When a signal source (not shown) is connected and the power is turned on,
The reset circuit 13 detects the rise of the power supply voltage (detects the power-on of the circuit), and thereby sets the reset signal to MAX.
The data is output to the latch circuit 6 and the counter 8 to reset these circuits. Video signal 100 output from the signal source
Is input to the pedestal clamp circuit 1 and the attenuator 12. The pedestal clamp circuit 1 operates in response to a horizontal synchronization signal, performs DC reproduction of an input video signal, and outputs the DC-reproduced video signal to a peak value hold circuit 2.

The peak value hold circuit 2 holds the maximum value of the video signal input from the pedestal clamp circuit 1 every one vertical synchronization period. This peak value hold circuit 2 is 1
Reset every vertical synchronization period. The A / D conversion circuit 3 converts the maximum value of the video signal held by the peak value hold circuit 2 into a digital signal at the rise of the vertical synchronization signal,
This is output to the data latch circuit 4. That is, the maximum input level (analog signal) of the video signal for each vertical synchronization period
Is converted into a digital signal, and this maximum level is held by the data latch circuit 4 at the rise of the vertical synchronizing signal.

The comparator 5 compares the current data (C) latched by the data latch circuit 4 with the maximum value (P) input up to the previous time and held by the MAX latch circuit 6. As a result, if the current data (C) is larger than the previous maximum data (P), the comparator 5
0 is output to the MAX latch circuit 6. When the latch signal 200 is input, the MAX latch circuit 6 holds the current data (C) instead of the previous maximum data (P). That is, the current data (C) is determined to be the largest of the data input so far, and the current data (C) is held in the MAX latch circuit 6.

The D / A conversion circuit 10 includes a MAX latch circuit 6
Is converted into an analog signal and output to the level shift circuit 11. However, the D / A conversion circuit 10 converts the data into an analog signal under the following conditions. That is, a vertical synchronization signal is input to one terminal of the AND circuit 7. The counter 8 outputs a low-level signal while the counter 8 does not count up to the set value, and outputs a high-level signal when the counter 8 reaches the set value. Therefore, while the count value of the counter 8 does not reach the set value, the inverter 9 is connected to the other terminal of the AND circuit 7.
To input a high-level signal. Therefore, during this time, the AND circuit 7 is open, and the vertical synchronization signal is input to the counter 8 through the AND circuit 7.

When the counter 8 counts the vertical synchronizing signal and reaches a set value, its output becomes high level, and the gate of the AND circuit 7 is closed through the inverter 9. At the same time, the conversion operation of the D / A conversion circuit 10 starts at the rising edge when the output of the counter 8 becomes high level,
The data (maximum value of the video signal) held in the MAX latch circuit 6 is converted into an analog signal and output to the level shift circuit 11. This means that the D / A conversion circuit 10 does not operate until the counter 8 counts up,
During this time, it is necessary to wait until the maximum value of the video signal is held in the MAX latch circuit 6.

Usually, since the video signal 100 starts with a demonstration signal of the JAMMA standard, the maximum value of the demonstration signal is MAX before the counter 8 counts up.
The data is held in the latch circuit 6.

The level shift circuit 11 converts the level of the maximum value (analog signal) of the input video signal into a control signal, and outputs the control signal to the attenuator 12.
The attenuator 12 has an attenuation rate corresponding to the signal input from the level shift circuit 11, and the input video signal 10
0 is attenuated at the attenuation rate and output. Here, the attenuation rate of the attenuator 12 is set in advance so as to change according to the level of the control signal input from the level shift circuit 11 so that the maximum value of the video signal 100 becomes an appropriate level. Therefore, the attenuator 12 converts the video signal 100 into a video signal of an appropriate level, and outputs the video signal to an amusement device such as a game device monitor (not shown). It should be noted that usually, the video signal 10
Since the maximum value of 0 is included, the attenuation rate of the attenuator 12 is adjusted to an appropriate value at the beginning of the input of the video signal.

According to the present embodiment, the maximum value of the input video signal 100 is always held by the MAX latch circuit 6,
By outputting a control signal corresponding to the held maximum value of the video signal 100 from the level shift circuit 11 to the attenuator 12, the attenuation rate of the attenuator 12 can be quickly and accurately adjusted to a value corresponding to the maximum value of the video signal 100. Can be set automatically. This eliminates the need for the adjuster to manually adjust the level of the input video signal 100 to an appropriate level so as to match the input level of the amusement device each time the signal source that generates the video signal 100 of the JAMMA standard is replaced, thereby saving labor. In addition to this, the video signal of an appropriate level can be always input to the amusement device regardless of the skill level of the adjuster, and the amusement device can be operated stably.

FIG. 2 is a block diagram showing an embodiment of a monitor for a game machine conforming to the JAMMA standard. Reference numeral 50 denotes an automatic gain adjustment circuit shown in FIG. 1, reference numeral 60 denotes a video signal processing circuit for performing various processes on an input video signal, and reference numeral 70 denotes a CRT for displaying an image corresponding to the input video signal.

Next, the operation of this embodiment will be described. A JAMMA standard video signal 100 is input to an automatic gain adjustment circuit 50 from a signal source (not shown). The automatic gain adjustment circuit 50 detects the maximum level of the video signal 100, and adjusts the video signal 10 so that the level of the video signal 100 matches the input level of the video signal processing circuit 60 at the next stage.
The level of 0 is adjusted and output to the video signal processing circuit 60. The video signal processing circuit 60 performs various processes on the input video signal to generate a signal that can be displayed on the CRT 70, and then outputs the signal to the CRT 70. The CRT 70 displays an image corresponding to the video signal on its screen.

According to the present embodiment, even if the level of the input video signal 100 changes by changing the signal source (not shown), the video signal 100
Automatically adjusts the level of the video signal 100 to the input level of the video signal processing circuit 60, so that it is not necessary to manually adjust the level of the video signal 100 every time the signal source changes as in the related art. Properties can be significantly improved.

[0028]

As described above, according to the automatic gain adjustment circuit of the present invention, even if the signal source for generating the JAMMA standard video signal is changed, the level of the video signal input from the signal source is automatically adjusted. It can be quickly and accurately adjusted to an appropriate level and input to an amusement device. Further, according to the game device monitor of the present invention, it is not necessary to manually adjust the level of the input video signal every time the signal source changes, and the operability can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic gain adjustment circuit according to the present invention.

FIG. 2 is a block diagram showing an embodiment of the game device monitor of the present invention.

FIG. 3 is a block diagram showing a configuration example of a conventional gain adjustment circuit that adjusts an input level of a video signal of JAMMA standard to an appropriate level.

FIG. 4 is a block diagram showing another configuration example of a conventional gain adjustment circuit for adjusting an input level of a video signal of JAMMA standard to an appropriate level.

[Explanation of symbols]

 Reference Signs List 1 pedestal clamp unit 2 peak value hold circuit 3 A / D conversion circuit 4 data latch circuit 5 comparator 6 MAX latch circuit 7 AND circuit 8 counter 9 inverter 10 D / A conversion circuit 11 level shift circuit 12 attenuator 13 reset circuit

Claims (6)

[Claims] 1. A level detector for detecting and holding a maximum level of an input video signal, and a control signal generator for generating a control signal having a level corresponding to the maximum level of the video signal detected by the level detector. Means for setting an attenuation rate corresponding to the level of the control signal generated by the control signal generation means, and attenuating the input video signal at this attenuation rate and outputting the same. An automatic gain adjustment circuit characterized by the following. 2. The automatic gain adjustment circuit according to claim 1, wherein said control signal generation means generates said control signal after a lapse of a predetermined time from said input of said video signal. 3. The automatic gain adjustment circuit according to claim 1, wherein said level detection means is reset when power is turned on. 4. The automatic gain adjustment circuit according to claim 1, wherein said video signal is a signal of JAMMA standard. 5. The automatic gain adjustment circuit according to claim 1, wherein said level attenuation means is an attenuator. 6. An automatic gain adjustment circuit according to claim 1, further comprising: a video signal processing circuit for inputting a video signal whose level has been adjusted by said automatic gain adjustment circuit and performing various processes. A monitor for displaying a video signal processed by the video signal processing circuit.