JPH0856294A - Dark part detector - Google Patents

Abstract

PURPOSE:To provide a dark part detector which detects a dark part without using a digital memory having a large capacity neither an expensive A/D converter. CONSTITUTION:The luminance signal of a processed input video signal from a DC reproducing circuit 2 is supplied to a comparator 3 as a voltage Vd to be compared. A microcomputer 6 controls a PWM signal generation circuit 6a to change the pulse width. This pulse signal is made into a DC reference voltage Vref by a low pass filter 7 and is supplied to the comparator 3, and the microcomputer 6 gradually increases the reference voltage Vref from 0 to detect the point of the reference voltage at which the comparison result shows that the voltage to be compared is lower once or more in one field. The comparison in the comparator 3 is performed again based on the detected reference voltage; and if it is detected that the voltage to be compared is lower in a horizontal scanning period and is higher in the other horizontal scanning periods, the microcomputer 6 discriminates the existence of a dark part in the preliminarily determined horizontal scanning period of the input video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dark area detecting device used in a television receiver or the like, and a dark area where a predetermined range of a video signal is uniformly dark without using an expensive A / D converter. The present invention relates to a dark area detection device capable of easily detecting whether or not

[0002]

2. Description of the Related Art Conventionally, as television receivers have been diversified, the display screen has been widened. For example, satellite broadcasting such as high-definition broadcasting or ordinary NTSC.
Wide aspect television receivers (hereinafter referred to as wide televisions) capable of mutually receiving broadcasts such as standard broadcasts have been put into practical use.

As is well known, this wide television is equipped with a display screen (CRT) having an aspect ratio of 16: 9 so that the viewer can effectively feel, feel and be impressed, and receives the current terrestrial waves. Not only the tuner is provided, but there are also those having a satellite broadcast receiving tuner, a teletext tuner, and the like.

In recent years, terrestrial broadcasting has been used to broadcast programs with the same aspect ratio of 16: 9 as in high-definition broadcasting.
On the receiving side, a second-generation EDTV capable of viewing the program on the current NTSC television receiver
(Extended Definition Tele
(abbreviation of "vision", hereinafter referred to as "EDTV2") has attracted attention, and EDT for decoding such an EDTV2 signal
There is also a wide-screen television equipped with a V2 decoder and the like.

By the way, in such a wide television and a television receiver having a normal display screen with an aspect ratio of 4: 3, various video sources in which the vertical and horizontal sizes of the projected image are different can be considered. . Among them, the movie aspect ratio is close to 16: 9, and a cinemascope-sized movie program or a Vista-sized movie program that is displayed in the same display state as in a theater, and further EDTV2
When a system broadcast program or the like is received and displayed, a video of the main image area is displayed in the center of the normal display screen, and a black belt as a non-image area is displayed in the upper and lower portions of the display screen. So, in recent wide-screen TVs,
In order to view the image more effectively, for example, a so-called enlargement function of performing digital signal processing on the image signal and enlarging and displaying the image of the main image portion on the full display screen with an aspect ratio of 16: 9, a so-called Some have a zoom mode. In addition, there are also various screen modes such as a wide mode for displaying an image as it is and a full mode.

From a number of screen modes,
In order to automatically select and execute a screen mode according to an input video signal, for example, in a signal processing process for displaying a video based on the input video signal on a display screen, a video image of any display form It is essential to determine whether or not a signal has been input. Further, in the case of letterbox display or the like displayed as a black band on the upper and lower portions of the display screen as described above, a detection device for detecting whether or not it is a uniformly dark portion from the video signal, so-called A dark area detection device is indispensable, and a television receiver provided with this dark area detection device has been conventionally used.

A dark area detecting device used in a television receiver generally has an A / D converter for converting an input video signal into a digital signal and a temporary storage of the digital signal from the A / D converter. Digital memory,
A microcomputer (hereinafter, referred to as a microcomputer) that receives a digital signal from a digital memory and performs arithmetic processing is provided.

The microcomputer performs arithmetic processing based on the digital signal fetched from the digital memory, and detects whether or not the predetermined range of the video signal is a uniformly dark portion. In this case, the microcomputer performs arithmetic processing to detect whether or not the value of the digital signal is uniformly smaller than a certain level within the above range.

Now, it is assumed that the dark area detection device is driven in order to determine the screen mode according to the input video signal. Then, the input video signal is converted into a digital signal by the A / D converter, and the digital signal is stored in the digital memory for each field. After that, the microcomputer fetches the digital signal from the digital memory,
The value of the captured digital signal is uniformly processed in the above range to determine whether or not it is smaller than a certain level, and the dark part is detected. In this way, the dark part of the image based on the input image signal is detected, and the microcomputer controls based on the detection result to automatically determine the screen mode according to the input image signal. The timing of the digital signal fetched from the digital memory is based on the horizontal and vertical sync signals.

However, in such a detection method,
The analog value of the video signal is usually 5-6 by the A / D converter.
Converted as digital value of bits. Therefore, a relatively large capacity digital memory is required to store this digital signal. That is, it becomes expensive. Further, since the A / D converter needs to operate at high speed, it has a complicated structure.
Since a microcomputer operating at high speed is required to correspond to the converter, there is a problem that the cost of constructing the dark part detection device becomes expensive after all.

[0011]

As described above, in the conventional dark area detection device, the dark area detection processing is performed by using the A / D converter for converting the video signal into a digital signal and the digital memory for storing the digital signal. However, in this case, the digital memory needs to have a relatively large capacity, and in order to operate the A / D converter at a high speed, the structure is complicated. From
A microcomputer that performs arithmetic processing must operate at a high speed, which inevitably increases the cost.

Therefore, the present invention has been made in view of the above problems, and it is possible to detect a dark portion without using a large-capacity digital memory and an expensive A / D converter, and with a simple structure. It is also an object of the present invention to provide a dark part detection device that can be configured at low cost.

[0013]

A dark area detecting apparatus according to the present invention comprises a video signal input terminal to which a video signal is supplied, and a horizontal and vertical sync signal input to which a horizontal and vertical sync signal separated from the video signal are supplied. A first DC reproducing means connected to the terminal and the video signal input terminal, performing a DC reproduction process on the supplied video signal, and outputting a luminance signal as a compared voltage; and a reference for the compared voltage. A reference voltage generating means for inputting a pulse signal for generating a reference voltage, converting the pulse signal into a direct current and outputting the reference voltage, a compared voltage from the first direct current regenerating means, and the reference voltage. Compare with the reference voltage from the generating means,
Comparing means for outputting a comparison result, and a circuit for generating a pulse signal for changing the reference voltage, means for controlling the circuit to adjust the pulse width of the pulse signal, the horizontal and Horizontal and vertical synchronization signals are input from the vertical synchronization signal input terminal, the comparison result from the comparison means is taken in at a timing according to these synchronization signals, and the pulse width of the pulse signal is determined based on the comparison result. Using the reference voltage corresponding to the determined pulse signal, the comparison result by the comparison means is detected in the predetermined horizontal scanning period of one field, and the determination means for determining the presence of the dark portion of the input video signal based on the comparison result. And are provided.

[0014]

In the present invention, the luminance signal of the input video signal is supplied to the comparing means as the compared voltage by using the first direct current reproducing means. The determining means controls the circuit to generate the pulse signal and change the pulse width of the pulse signal. This pulse signal is generated by the reference voltage generating means.
It is converted into a direct current, created as a reference voltage, and supplied to the comparison means. For example, the microcomputer as the determination means controls the PWM signal generation circuit to gradually increase the reference voltage from zero. At this time, the comparison result by the comparator as the comparison means detects the point of the reference voltage at which the compared voltage is determined to be lower even once during one field. After that, the microcomputer performs comparison by the comparator again in the horizontal scanning period of one field based on the detected reference voltage.
In this case, when it is detected that the compared voltage is lower in the predetermined horizontal scanning period and the compared voltage is higher in the other horizontal scanning periods, the microcomputer inputs the comparison result. It is determined that the dark portion is present during the predetermined horizontal scanning period of the video signal. Therefore, the dark portion can be easily detected without using the A / D converter and the digital memory at high cost, so that the device can be realized with a simple configuration and at low cost.

[0015]

EXAMPLES Examples will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a dark part detecting device according to the present invention.

In FIG. 1, a video signal which is an analog signal is input to the video signal input terminal 1. The input video signal is supplied to the DC reproducing circuit 2, and the DC reproducing circuit 2 performs DC reproduction processing on the input video signal and supplies the luminance signal as one of the compared voltages Vd to one input terminal of the comparator 3.

The horizontal sync signal input terminal 4 and the vertical sync signal input terminal 5 are supplied with the horizontal and vertical sync signals separated from the video signal by a sync separation circuit (not shown), respectively. ing. The input horizontal synchronizing signal and vertical synchronizing signal are respectively supplied to the microcomputer 6. Based on the supplied horizontal and vertical synchronizing signals, the microcomputer 6 performs P
PWM as a control signal using the WM signal generation circuit 6a
Signal (Pulse Width Modulation)
, Which is a pulse width modulation signal),
The WM signal is D / A converted and supplied to the low pass filter 7. The PWM signal generating circuit 6a is provided inside the microcomputer 6, and the microcomputer 6 can control the PWN signal generating circuit 6a so as to freely change and output the PWM signal.

The low-pass filter 7 receives the supplied PWM
The signal is converted into a direct current, that is, a direct current regeneration process (integration) is performed, and the direct current component of the PWM signal is set as a reference voltage Vref.
It is supplied to the other input terminal of the comparator 3.

The comparator 3 compares the compared voltage Vd from the DC regeneration circuit 2 with the reference voltage Vref from the low pass filter 7 and outputs the comparison result to the microcomputer 6.

For example, the comparator 3 has the compared voltage Vd.
Becomes a voltage value higher than the reference voltage Vref, a high level (hereinafter, H signal) signal is output, and conversely, when the compared voltage Vd becomes low, a low level (hereinafter, L signal).
The signal of is output. The microcomputer 6 controls the comparator 3 at a timing based on the supplied horizontal and vertical synchronization signals.
The comparison result supplied from is determined. The microcomputer 6 can temporarily store the pulse width when controlling the generation of the PWM signal by the PWM signal generation circuit 6a, and also temporarily store the reference voltage Vref corresponding to this PWM signal. There is.

Next, the control operation by the microcomputer of the dark part detecting device will be described in detail with reference to FIG.

FIG. 2 is a flow chart showing the control operation of the microcomputer shown in FIG.

Now, it is assumed that the power of the television receiver to which the dark area detecting device is attached is turned on. Then, the microcomputer 6 starts the detecting operation and shifts to the processing in step S1. In the process of step S1, the reference voltage Vref supplied to the comparator 3 is initialized, that is, the PWN signal generation circuit 6a is controlled so that the reference voltage Vref is zero, and the pulse width of the PWM signal is changed. At this time, since the pulse width of the generated PWM signal becomes extremely small, the reference voltage Vref supplied to the comparator 3 becomes zero by being converted into a direct current by the low-pass filter 7. Then, the process proceeds to step S2.

In the process of step S2, it is determined whether horizontal scanning based on the input video signal has started. If it is determined that this determination has not started,
The determination is performed again, and the operation continues until it is determined that the operation is started. Also, when it is determined that it has started,
The processing moves to step S3.

In the processing in step S3, the comparator 3 compares the compared voltage Vd from the DC regeneration circuit 2 with the reference voltage Vref and detects the comparison result. In this case, if it is determined that the reference voltage Vref is lower than the compared voltage Vd, the process proceeds to step S4, and if it is determined that it is higher, the microcomputer 6 ends the control operation. For example, the microcomputer 6 ends the control operation when the output from the comparator 3 is the L signal, and shifts the processing to step S4 when the output is the H signal.

Next, the microcomputer 6 determines whether or not the horizontal scanning in one field of the input video signal is completed by the processing in step S4. If it is determined that the horizontal scanning is completed, the processing in step S5 is executed. If not, the process returns to step S3.

In the process in step 5, the PW
The M signal generation circuit 6a is controlled to increase the pulse width of the PWM signal. That is, the reference voltage Vref supplied to the comparator 3 is gradually increased from zero. After that, the process is fed back to step S2, and the above step S2 is performed.
The process is continued until the determination of 3 becomes YES.

That is, the microcomputer 6 sequentially performs the processing from step S2 to step S4 in the horizontal scanning period of one field, and when it is determined in step S4 that one field is completed, the processing in step S5 causes the comparator 3 to operate. The reference voltage Vd to be supplied is increased. Therefore, the reference voltage Vref at the time of switching to the next field becomes higher than that at the time of the previous field. In this way, the reference voltage Vref is increased by the process of step S5 of the microcomputer 6, and then the routine of steps S2 to S5 is repeated, whereby the determination of step S3 is determined to be YES. At this time, the comparator 3 shown in FIG.
The signal is output.

Thus, the microcomputer 6 detects the point of the reference voltage Vref at which the output of the comparator 3 is determined to be lower than the compared voltage Vd even once during one field, and sets the reference voltage Vref. . The output of the comparator 3 is checked during the horizontal scanning period assumed from the vertical synchronizing signal and the horizontal synchronizing signal input to the microcomputer 6.

Then, the microcomputer 6 supplies the set reference voltage Vref to the comparator 3, and the comparator 3
Is compared with the compared voltage Vd of the input video signal by
That is, the comparison result in the horizontal scanning period of one field is detected.

FIG. 3 shows a state in which one field is horizontally scanned on the display screen of the television receiver.
The horizontal scan in the upper part of the display screen is shown as H scan A,
The horizontal scanning in the central portion of the display screen is shown as H scanning B.

The microcomputer 6 detects the comparison result with the compared voltage Vd in the horizontal scanning period of one field based on the reference voltage Vref set as described above. For example, as shown in FIG.
In the case of scan A, the compared voltage Vd becomes lower than the set reference voltage Vref. Reference voltage Vref at this time
4A is compared with the compared voltage Vd. As can be seen from FIG. 4A, the comparison voltage Vd of the video signal between the horizontal synchronizing signals becomes lower for the H scan A. ing. At this time, the microcomputer 6 can detect the L signal.

On the other hand, in the case of H scanning B in the central portion of the display screen 50 shown in FIG. 3, the compared voltage Vd becomes higher than the set reference voltage Vref. A comparison between the reference voltage Vref and the compared voltage Vd at this time is shown in FIG. 4B. As can be seen from this figure, regarding the H horizontal scanning B, the comparison of the video signal between the horizontal synchronizing signals is performed. The comparison voltage Vd is higher than the reference voltage Vref. At this time, the microcomputer 6
The signal can be detected.

Therefore, the microcomputer 6 uses the set reference voltage Vref to detect that the output of the comparator 3 is always lower than the compared voltage Vd during the horizontal scanning period of the upper and lower portions of the display screen, for example. It is possible to determine that the dark portion appears in the upper and lower areas of the display screen 50 by detecting whether the compared voltage Vd is higher even once in the other horizontal scanning periods. That is, the letterbox display can be determined. Therefore, in the dark part detection device of this embodiment, the A / D is expensive.
It is possible to favorably detect the dark part in the input video signal without using a converter. Furthermore, since the dark part detecting device can be configured with a simple structure without using a digital memory, it is not necessary to provide a microcomputer with a high-speed operation, and as a result, the cost can be reduced.

In the present embodiment, the horizontal scanning period for comparing the set reference voltage with the compared voltage of the input video signal is, for example, in the upper and lower portions of the display screen according to the television signal of the EDTV2 system. Horizontal scan destination 60
The comparison may be performed with respect to the range of the books, or may be configured in advance in the microcomputer so that the comparison is performed with respect to the range of 360 in the central portion.

[0036]

As described above, according to the present invention,
Even if an expensive A / D converter is not used, a predetermined range of the video signal is a uniformly dark part by using a microcomputer provided with a direct current reproducing circuit, a low pass filter, a comparator and a PWM signal generating circuit. It is possible to detect whether or not. Therefore, the dark part detection device can be realized at a low cost with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a dark part detection device according to the present invention.

2 is a flowchart showing a control operation of a microcomputer of the apparatus shown in FIG.

FIG. 3 is an explanatory diagram for explaining the operation of the apparatus of FIG.

FIG. 4 is an explanatory diagram for explaining the operation of the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Video signal input terminal 2 ... DC reproduction circuit 3 ... Comparator 4 ... Horizontal synchronization signal input terminal 5 ... Vertical synchronization signal input terminal 6 ... Microcomputer 6a ... PWM signal generation circuit 7 ... Low-pass filter Vd ... Compared voltage Vref ... Reference voltage

Claims (3)

[Claims] 1. A video signal input terminal to which a video signal is supplied, horizontal and vertical sync signal input terminals to which horizontal and vertical sync signals separated from the video signal are supplied, and connected to the video signal input terminal, First direct current reproducing means for subjecting the supplied video signal to direct current reproduction processing and outputting a luminance signal as a compared voltage, and inputting a pulse signal for producing a reference voltage as a reference for the compared voltage. Then, the reference voltage generating means for converting this pulse signal into a direct current and outputting it as the reference voltage, the compared voltage from the first direct current regenerating means, and the reference voltage from the reference voltage generating means are compared and compared. Comparing means for outputting a result and a circuit for generating a pulse signal for changing the reference voltage, and means for controlling the circuit so as to adjust the pulse width of the pulse signal. Then, the horizontal and vertical sync signals from the horizontal and vertical sync signal input terminals are input, the comparison result from the comparison means is fetched at the timing corresponding to these sync signals, and the pulse of the pulse signal is generated based on the comparison result. The width is determined, the comparison result by the comparison means is detected in a predetermined horizontal scanning period of one field by using the reference voltage according to the determined pulse signal, and the presence of the dark portion of the input video signal is based on the comparison result. A dark part detection circuit comprising: a determination unit for determining. 2. The determination means is composed of a microcomputer, and when the microcomputer determines the pulse width of the pulse signal based on the comparison result by the comparison means, the comparison result is obtained even once in one field. The dark area detection device according to claim 1, wherein the circuit is controlled so as to generate a reference voltage when it is determined that the compared voltage is lower. 3. The microcomputer detects the comparison result by performing comparison by the comparison means during a predetermined horizontal scanning period period of one field using a set reference voltage. When the comparison result is one in which the compared voltage is detected to be lower in the predetermined horizontal scanning period and the comparison voltage is detected to be higher in the other horizontal scanning periods, the predetermined result is set. The dark area detection device according to claim 2, wherein the presence of a dark area is determined within the range of the horizontal scanning period.