JP2991549B2 - Video signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device such as a television receiver, and more particularly to a device for detecting the level of a luminance signal or a color difference signal and controlling the input / output characteristics of the luminance signal. It is.

[0002]

2. Description of the Related Art FIG. 10A shows a conventional luminance signal processing circuit. A luminance (Y) signal is separated from a composite video signal demodulated by a video detection circuit (not shown) and supplied to an input terminal 80. This Y signal is input to the clamp circuit 81 via the coupling capacitance C1 and is clamped. Clamp circuit 81
Brightness signals of the pedestal voltage is stabilized by is input to the black expanding circuit 82, the luminance signal close to black is extended so as not to underexposure. Next, it is input to the DC transmission amount correction circuit 83, and the APL (Average Picture)
Level (average luminance level) changes the direct current (DC) of the luminance signal during the screen display period. The next-stage contrast circuit 84 controls the gain for amplifying the luminance signal,
Increase or decrease the brightness amplitude. The next ACL (Automati
In c Contrast Limiter, the luminance signal is limited so that the white peak of the luminance signal does not exceed a certain value. The luminance signal subjected to the signal processing is clamped again by the bright circuit 86, the DC level is stabilized, and output to the output terminal 87.

In recent years, characteristic black extension and ACL will be described with reference to FIG. The black expansion circuit 82 amplifies a certain DC voltage or less of the input signal and adds it to the original signal.
As a result, the input / output characteristics are as shown by the dotted line in FIG. 3B, and the input signal in the vicinity of black is expanded. On the other hand, in the ACL 85, the level on the white peak side is nonlinearly compressed. When the luminance signal exceeds the white peak voltage, an attenuating circuit having a gamma characteristic is used for an input exceeding a certain value so that the white peak does not exceed the set voltage. The input / output characteristics in this case are as shown by the dotted line in FIG. With these image quality improvement circuits, good received images can be obtained.

By the way, as can be said for both the black extension circuit and the ACL, since the start / stop of the circuit operation is determined by an external time constant, a shift due to charging / discharging, that is, an operation offset occurs.

[0005] For example, in a black expansion circuit, the blackest level of an input signal is detected, and feedback is performed so that the level does not fall below the pedestal, and a feedback filter is externally provided. Figure 10 capacitor C2 (a), which corresponds to a filter of the resistor R3 pixels. When the blackest level of the input luminance signal has not reached the pedestal, the black extension circuit charges C2 and R3 and starts the black extension operation. When the blackest level of the input becomes equal to the pedestal, the charging current does not flow from the black stretching circuit, and the potential of the capacitor C2 is stabilized. However, even at this time, the electric charge is charged through the resistor R3, and accordingly, the black extension circuit needs to supply a charging current. Therefore , even though the black level has reached the pedestal, a further black extension operation is required.
A blackout phenomenon such as the following occurs. This is the same in the ACL.

In recent black expansion circuits and ACLs, the black signal and the start voltage of the ACL compression operation are changed according to the APL to adaptively expand and compress the signal. Is complicated, and there is a problem that this information alone cannot sufficiently process adaptively.

Further, when the dynamic range of the display is narrow, such as in a liquid crystal display, a signal of an average luminance level cannot be expanded by black expansion and ACL, and there is no judgment information for performing this.

Further, if the weak electric field noise is mixed in a weak electric field, the black extension and distinguish whether the luminance signals for one-noise of the ACL is Tsukazu, there is a problem that respond to noise.

[0009]

As described above, in the conventional system, since the start / stop of the circuit operation is determined by an external time constant in black extension or ACL, the shift due to charge / discharge, that is, the operation offset. Occurs.
Further, there is a problem that the information of the luminance signal waveform is complicated, and the black extension and white compression processing cannot be sufficiently adaptively performed only by the information based on the APL. Furthermore, countermeasures when the dynamic range of the display is narrow, such as a liquid crystal display, are insufficient. When weak electric field noise is mixed in a weak electric field, there is a problem in that it is difficult to distinguish between a luminance signal and a noise in the black extension and the ACL, and there is a problem that a response is made to the noise.

Therefore, an object of the present invention is to provide a color difference signal
Within multiple zones preset by phase and color saturation
Of which zone is detected, and the level for each zone
Detection, and based on this detection result, demodulation band and luminance signal
Control the operating point of the route and display differences
So that the optimal display can be obtained adaptively even when the electric field is strong or weak.
To provide a video signal processing device.

[0011]

SUMMARY OF THE INVENTION The present invention provides a chroma demodulation.
The color difference signal output from the circuit depends on the hue and color saturation.
To any of the preset zones
Detected for each signal component according to each signal component detected for each zone
Level distribution detecting means for generating a pulse output by
Based on the result of each detection output of the bell distribution detecting means, the chroma
In addition to controlling the demodulation band of the signal demodulation circuit,
At least one of linear and nonlinear processing
Control means for controlling an operating point of a luminance signal processing unit for performing the processing
Is provided.

[0012]

A color difference signal is monitored by the above means.
Adaptively adapts to display differences and electric field strength
You can get a good display.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a reference example on which the present invention is based .
The luminance signal Yin is input to the clamp circuit 1 via the input terminal 101 and the coupling capacitance C1. The luminance signal in which the pedestal voltage is stabilized is input to the black extension circuit 2. The output of the black expansion circuit 2 is input to the DC transmission amount correction circuit 3, and the corrected output is input to the contrast circuit 4 to increase or decrease the amplitude.
The output luminance signal of the contrast circuit 4 is input to an automatic contrast limiter (ACL) 5, which performs white expansion or compression to output. The output luminance signal is finally stabilized by the drive circuit 6 again at the DC level as the final output luminance signal, and is output to the output terminal 102.

The luminance signal clamped by the clamp circuit 1 is further input to a level discriminating circuit 14 constituting a level distribution detecting device, and it is determined at which level the signal is. Here, an example in which the luminance level is divided into three will be described. The level of the luminance signal is divided into zones z1 to z3.
The determination signal is output to 5 to 17. Outputs of the counters 15 to 17 are input to a control circuit (for example, CPU) 18.
From the black expansion circuit 2, the expanded luminance signal is supplied to the blackout detection circuit 7. The underexposure detection circuit 7 outputs a detection signal only when underexposure occurs. The latch circuit 12 latches this blackout detection signal and outputs
18. From the ACL, the expanded or compressed luminance signal is input to the overexposure detecting circuit 8. The underexposure detection circuit 8 detects whether the whitest peak of the luminance signal exceeds a set level. When an underexposure occurs, the detection signal is supplied to the counter 13.
The output of the counter 13 is supplied to the CPU 18.

The CPU 18 controls each of the zone counters 15 to 1
7. The information from the latch circuit 12 and the counter 13 is
The data is stored in the AM 19, and the optimum control state is calculated. Based on the calculation result, the black expansion circuit 2 and the DC transmission amount correction circuit 3
And DC control circuits 9-1 for controlling ACL5
1 to send data.

The black expansion circuit 2, the DC transmission amount correction circuit 3 and the ACL 5 in FIG. 1 only set the control state in accordance with the DC information, and the conventional black level detection function corresponds to a black-out detection circuit. Similarly, the conventional whiteout detection function corresponds to the whiteout detection circuit 8.

FIG. 2A shows the zone counter 15 of FIG.
FIG. 18 is a diagram for explaining operations of Nos. To 17; Now, it is assumed that a ramp waveform signal of 100% IRE is input to the input terminal 101. The level from the pedestal to the white peak is divided into three as described above, and zones z1 to
z3. A sampling clock is applied as shown in (c) of FIG. 2A, and a video signal is sampled at the rise of the clock. Then, for example, at the rise of B1, the video signal is at the level of zone 3. Since the horizontal retrace period naturally has a level equal to or lower than the pedestal level, the level discrimination operation is stopped by using a horizontal blanking pulse as shown in FIG. Therefore, the rising edges of the clocks A1 and A2 are ignored. Valid data is B1 to B6. In this example, the sampling clock has a frequency of 8 fH for convenience of explanation. The blanking pulse (b) in the horizontal retrace period is set longer than the actual retrace period so as not to sample even if the luminance level in the horizontal retrace period is wrong. B1
For each of the six sample points up to B6, the level discriminating circuit outputs which zone is in which zone. In the zone counters 15 to 17, one of the counters counts at each point. This count is performed over one field, and the CP value of each zone is calculated.
U18 detects. Based on the result, the CPU 18 calculates the optimal state setting of the image quality improving function, and the DC control circuit 9
Each corresponding circuit is controlled via .about.11.

FIG. 2B shows an example of the control characteristics. When the count results of the sampled fields are concentrated in the zones z1 and z2 and hardly in the zone z3, the black extension is operated. If the degree of concentration in the zones z1 and z2 is high, the black extension start voltage is set high as shown by the characteristic line 2a in FIG. Otherwise, the start voltage is set low as shown by the characteristic line 1a. As will be described later, the latch output from the blackout detection circuit may be used for this determination. In this distribution, the ACL 5 operates in the direction of compressing the input signal as indicated by the characteristic lines 1b, 2b, and 3b shown in FIG. The setting order of the characteristic lines 1b, 2b, 3b is the order in which the count value of the zone 1 is small, and when the count value is the smallest, the state 1b, which is the lightest compression, is taken. If it is slightly larger, the white peak is lowered without lowering the start voltage and changing the compression gain as shown in 2b. If it is larger, the compression characteristic is a two-point broken line as in the characteristic line 3b, and only the portion close to white is compressed without changing the start point. The compression method may be a polygonal line type or a compression method using a completely non-linear gamma curve. The compression method is characteristic line 2.
The settings of b and 3b may be performed simultaneously instead of separately. The method of compressing white with the characteristic of the characteristic line 3b can minimize the influence on the signal of the intermediate luminance. As will be described later, the count output from the overexposure detection circuit may be used in combination for this determination. At the same time the DC transmission rate correction shifts the DC input-output characteristic in accordance with dc reproduction rate set <br/>.

In the case of the present example, the APL is expected to be high because it is concentrated in zone 1 and zone 2. When the DC regeneration rate is set to less than 100%, the input / output characteristics are shifted in the direction of the characteristic line 2c shown in FIG. Conversely, if it exceeds 100%, the DC transmission amount correction direct circuit 3 is controlled so as to shift in the direction of the characteristic line 1c.

Next, a case where the count result is concentrated in zones 2 and 3 will be described below. In this case, since there are many levels near black, the black decompression circuit 2 is not operated and FIG.
( B ) As shown by the solid characteristic line in (a), or slightly black extension as shown in FIG. If the count value is highly concentrated in zone 3, the former may be used, and if not so, the latter may be used. ACL5 may be a characteristic that does not automatically limited as solid characteristic line in FIG. 2 (B) (b),
4B and 5B may be operated in the extending direction. The direction of operation of the DC transmission amount correction circuit 3 is also determined by the set DC regeneration rate at this time. The APL is expected to be low because it is concentrated in zones 2 and 3. Therefore, if the playback rate is set to less than 100%,
The DC level is shifted in the direction of the characteristic line 1c of (B) (c), and when the DC level exceeds 100%, the characteristic level of FIG.
DC is lowered as in step 2c. In the conventional case where only APL was monitored, it was difficult to determine whether or not to perform white expansion. However, if the signal level is known in this way, how many components near white exist? Since it can be detected, it is possible to determine white extension. Of course, as in the case described above, when controlling the operating points of these circuits, it is also possible to use the outputs of the underexposure detection circuit 8 and underexposure detection circuit 7 in combination.

Next, a method for detecting weak electric field noise will be described. This will be described with reference to the system diagram of FIG. 1 and FIG. In a weak electric field, a pulse noise called a weak electric field noise is uniformly applied to the luminance signal. At this time, the level determination circuit 14
Since the level of a signal containing noise is detected, if noise happens to be added to a sampled luminance signal, the level changes due to the noise. It is also possible to sample and detect the sample value of the horizontal retrace period, that is, the noise component from the pedestal not including the luminance signal at the positions A1 and A2 in FIG. The level of the sample points A1 and A2 fluctuates due to the leakage of the data, and it is difficult to extract only pure noise. Therefore, when the vicinity of the vertical synchronization period as shown in FIG. 3B is used, the detection can be easily performed only by processing the timing pulse. Figure 3 shows the vertical retrace period
As shown in (B), it is divided into an equalizing pulse and a period of only horizontal synchronization of a vertical synchronizing signal and no luminance signal. Each of the count circuits is operated in an appropriate period excluding the vertical synchronization period in the same manner as in the video display period. If there is no noise, only the samples in zone 3 will be counted during this period, and the level will not be higher than zone 2. However, the positive noise is added at the sample point as the noise is mixed.
Is counted, so that the CPU 18 can detect mixing of noise. Therefore, the CPU 18 sets the counter 16
Are counted once at a timing before the vertical synchronization period, and the results counted by each of the counters 15 to 17 after the vertical synchronization period and during the non-signal period until the video signal arrives are taken, the noise level, that is, The strength of the electric field can be detected. Incidentally, since the noise level and the mixing frequency increase as the electric field is weaker, it is understood that the larger the number counted by the counters 16 and 17 in the zone 2 and the zone 3 during the non-signal period, the weaker the electric field.

The embodiment described here is a case in which the system shown in FIG. 1 is diverted. As a modified example, an example in which a counter dedicated to weak electric field noise is provided will be described with reference to FIG. A level discrimination circuit 20 and a noise counter 21 are added to the system of FIG.
18. The level discrimination circuit 20 detects whether or not there is a luminance signal in the noise counter detection zone as shown in FIG. 2A during a non-signal period after the vertical synchronization signal. In this zone, a voltage higher than a voltage offset from the pedestal level by a certain voltage is detected. In this way, the counters in zones 1 to 3 are dedicated to the level detection of the video display signal, and can be separated from the noise detection. When the zone 3 is also used, since the noise detection level is one third of white, it cannot be detected when low level noise enters. However, in the case of FIG. Since it can be set low, there is an advantage that the low-level noise can be detected.

The CPU 18 detects the video signal level and
Referring to both the count values from the charting counter 21, it is possible to the optimum state by processing the control state of image quality settings. Nothing is inserted in the equalization pulse period after the vertical synchronization signal, but depending on the broadcasting station, a text multiplex broadcast signal or GCR (ghost cancel reference) may be used.
Since a signal such as a signal is often inserted, it is practical to detect the weak electric field noise only in the rear equalizing pulse period. Next, an example of the underexposure and overexposure detection circuits 7 and 8 shown in FIG. 1 will be described.

FIG. 4A shows a specific example of the underexposure detection circuit 7. If blackout occurs, there is a tendency to design to avoid this in any part of one field. Therefore, a circuit for detecting underexposure in one field will be described. Transistors Q1 to Q5
Is a level determination circuit. The input luminance signal Yin is supplied to the transistor Q1 via the input terminal 31.
Supplied to the base. The emitter of the transistor Q1 is commonly connected to the emitter of the transistor Q2, and the current source I
1 is connected to the power supply line Vcc. At the base of the transistor Q2, the voltage VBTH at which black
Is set. That is, when the base potential of the transistor Q1 becomes lower than VBTH, the transistor Q2 is turned off.
The emitters of the transistors Q1 and Q2
3, Q4 connected to the collectors of the transistors Q3, Q4
The emitter of No. 4 is connected to the ground line GND, and the base is connected in common and connected to the collector of the transistor Q3. When underexposure is detected, the transistor Q
2 is turned off, and its collector output is supplied to the base of the transistor Q5. Transistor Q5
Is connected to the ground line, and the collector is a resistor R
1, and to the set input terminal of the RS flip-flop circuit FF1.

Now, VBTH is used to detect underexposure.
It is assumed that the voltage is set . Since the setup level of the luminance signal differs depending on the broadcasting station, this voltage cannot be said uniformly, but is set to the pedestal level here. When the luminance signal causes a black loss, the voltage of Yin falls below VBTH. Then, no current flows to the base of the transistor Q5, and the transistor Q5 is cut off. At this time, the collector potential of the transistor Q5, that is, the signal P4 becomes Vcc. The set (S) signal is input to the next-stage flip-flop circuit FF1,
The Q output, that is, the signal BCP becomes high level (Hi). A reset input (R), which is the other input of the flip-flop circuit FF1, has a clock pulse BC of a field cycle whose state changes during a field blanking period.
K has been entered.

As shown in FIG. 4 (B), when the signal P4 is generated due to the occurrence of blackout in any part of the field, the signal BCK immediately becomes Hi and the next clock pulse BC
The result is held until the K pulse arrives. By doing so, the occurrence of blackout can be latched until the end of one field, and the CPU 18 can easily take in data. FIG. 5A shows one specific example of the whiteout detection circuit. Transistors Q6 to Q10
Is the analog whiteout detection circuit 8.

The input luminance signal Yin is supplied via the input terminal 41 to the base of the transistor Q6. The emitter of the transistor Q6 is commonly connected to the emitter of the transistor Q7, and is connected to the power supply line Vcc via the current source I2. A voltage VWTH at which blackout occurs is set at the base of the transistor Q6. That is, when the base potential of the transistor Q6 becomes lower than VWTH, the transistor Q6 is turned on and the transistor Q7 is turned off. The emitters of the transistors Q6 and Q7 are connected to the transistors Q8 and Q
9, the emitters of the transistors Q8 and Q9 are connected to the ground line GND, and the bases are commonly connected to the collector of the transistor Q9. When underexposure is detected, the transistor Q6 is turned on and its collector output is supplied to the base of the transistor Q10. The emitter of the transistor Q10 is connected to the ground line, and the collector is connected to the resistor R2.
Connected to the power line via the inverter G1
It is connected to the. The output of the inverter G1 is supplied to the data input terminal of the D-type flip-flop circuit FF2 via the inverter G2. The Q output of the flip-flop circuit FF2 is supplied to a data input terminal of the flip-flop circuit FF3. Further, each flip-flop circuit FF2,
The FF3 is configured to be reset by the output of the inverter G1, and a signal WCK described later is used as a clock input. Also, the final output signal WC
P is derived by performing a logical operation on the signal WCK, the output of the inverter G2, and the Q output of the flip-flop circuit FF3 in the AND circuit G3. Next, the operation will be described with reference to the waveform diagrams of the respective parts in FIG.

The above-mentioned VWTH is a reference voltage for detecting underexposure of a video signal, and is normally set to 100% white. When the voltage of the input luminance signal Yin exceeds this VWTH, the transistor Q10 is cut off because no base current flows. If the voltage of the luminance signal Yin is lower than VWTH, on the contrary, the base current flows into the transistor Q10 and the transistor Q10 is turned on. Unlike underexposure, underexposure is likely to not be avoided immediately even if overexposure occurs to some extent, so this circuit can detect how much underexposure has occurred. Now, the detected transistor Q10 collector signal P1 is inverted by inverters G1 and G2,
Two D-type flip-flop circuits FF2 and FF3 are supplied to a cascade-connected shift circuit. A signal WCK is input as a clock to the flip-flop circuits FF2 and FF3.

The signal WCK is a pulse as shown in FIG. Now, it is assumed that a detection signal P1 as shown in FIG. The flip-flop circuit FF2 is
When the signal P1 is at a high level, sampling is performed with the signal WCK. When the signal P1 is at a low level, a reset is applied, so that the waveform becomes like P2 in FIG. This P2
Is input to the flip-flop circuit FF3 again and processed in the same manner as the flip-flop circuit FF2. The output P3 of the flip-flop circuit FF3 is as shown in (d) of FIG. Here, the signals P3 and G2 output (that is, P
When 1) and the signal WCK are input to the AND circuit G3 to obtain a logical product, the output WCP is as shown in FIG.

When the pulse width is shorter than one clock of WCK, nothing is output to the output section of the AND circuit G3 as shown in the period A of (a) of FIG. If one has a time width of one clock or more, one pulse is generated. When the whiteout has occurred for a long time as in the period C, a continuous pulse is generated. In this manner, it is possible to detect how long and how long the whiteout has occurred continuously. For example, the signal WCP may be counted and detected by the count value of one field or one line. If a continuous WCP is detected, it is possible to know in which range whiteout has occurred in one line. Flip-flop circuit FF1 of underexposure detection circuit 7
The method described in the above may be used for the overexposure detection circuit 8, or the reverse may be performed. If the underexposure and overexposure are detected in this manner, the feedback can also be provided to the control method in the CPU 18. FIG. 6 shows C as described above.
The control characteristics from the PU 18 are shown together.

First, as a start case, zones 1 to 3
In the case where the count values are almost equally distributed in FIG.
A linear input / output characteristic as shown in FIG. CPU18
Operates the black extension circuit 2 while monitoring the output from the blackout detection circuit 7, and controls the maximum black extension gain as shown in FIG. 6B unless blackout occurs. If blackout occurs in the process of shifting to the maximum black expansion gain, the black expansion gain is controlled in a lowering direction and fixed to a gain that does not cause blackout. At the same time, the ACL 5 causes a limiting operation to be performed when whiteout occurs. However, as described above, unlike the blackout condition, there is a tendency in recent years to set the ACL 5 not to operate even if whiteout occurs to some extent. Therefore, the operation of the ACL5 is controlled by a function based on the whiteout detection result.

FIG. 6D shows an example. Signal WCP
When the count value exceeds a certain value, the attenuation of the white peak is started by the ACL5, so that the white is not completely compressed so as not to exceed the overexposure voltage, but the amount of attenuation is determined according to the count value. I do. In accordance with this function, the CPU 18 operates the ACL 5, for example, as shown in FIG.
The input / output characteristics are as shown in FIG. In the case where blackening has occurred even though black extension has not been performed, the characteristic shifts to the dotted line from (a) to (c) in FIG.
It is assumed that black extension and ACL are not dependent but are processed in parallel.

The control characteristic of the CPU 18 may have the above-mentioned white extension characteristic in addition to the above, and the manner of reflecting the zone count result may be as described above. However, each circuit is set and the CPU 1 checks the counting result of the next field.
It is better to change the setting state during the field blanking period. The speed of shifting to the changed setting state can be performed in units of microseconds (mS) to seconds (S) as conventionally set by an external time constant. When the weak electric field noise is detected, at least the white extension is stopped, and the operation in which the restriction by the ACL 5 is slightly performed is a direction in which the noise is less noticeable. In this case, the black extension is in the direction of stopping, but it can be easily stopped if necessary.

FIG. 7 shows a specific example of the level discriminating circuit of FIG. Amplifiers A1 to A4 for comparison are prepared,
The non-inverting input terminals of the comparison amplifiers A1 to A4 include:
An input luminance signal Yin is supplied from an input terminal 51. Separate voltages VTH1 and VTH are applied to each inverting input terminal.
Apply TH2, VTH3 and VTH4. Vcp is a clamp voltage, and it is assumed that the pedestal voltage of the Yin luminance signal is clamped to this voltage. Vcp to amplifier A3,
The potential obtained by adding VTH2 to Vcp is applied to the amplifier A2, and further to VTH.
The potential obtained by adding 1 is input to the amplifier A1.
The potential which has been increased only by the voltage is applied to the amplifier A4. In the amplifier A1, when the Yin voltage becomes higher than the voltage of VTH1 + VTH2 + Vcp, the output becomes high level (Hi). Here, zone 1 is detected.

The output of the amplifier A2 becomes high level (Hi) when Yin exceeds Vcp + VTH2. However, the output of the amplifier A2 and the output obtained by inverting the output of the amplifier A1 by the inverter G4 are input to the AND circuit G5. When the output is in the zone 1 of the amplifier A1, no detection output is output from the AND circuit G5. ing. Then, only when Yin is in the zone 2, a high level (Hi) is output to the AND circuit G5. The output of the AND circuit G5 is used as the detection output of zone 2.

Similarly, in the amplifier A3, the output of the inverter G6 (inverting the output of the amplifier A2) and the output of the amplifier A3 are input to the AND circuit G7, and the level of the zone 2 or higher is excluded. That is, the output of the AND circuit G7 outputs a high level (Hi) only when the Yin voltage is present in the zone 3. The output of the AND circuit G7 is used as the detection output of zone 3. The detection results of each zone, the clock signal CK, and the blanking pulse BLK1 are input to the AND circuits G8 to G10. Clock signal CK
Is equivalent to the signal of (c) in FIG. 2A, and BLK1 is
3B corresponds to a signal obtained by combining the horizontal blanking signal and, if necessary, the vertical blanking signal of FIG. 3B. The outputs of the AND circuits G8 to G10 are set as Z1P, Z2P, and Z3P signals, respectively, and input to each zone counter of FIG. The amplifier A4 corresponds to the level determination circuit 20 in FIG. When Yin exceeds the voltage of Vcp + VTH3, a high level appears at the output of the amplifier A4. This signal is a noise detection output, and the clock signal CK and the blanking signal B are output by the AND circuit G11.
By taking the logical product with LK2, a ZNP signal is obtained. The blanking signal BLK2 is a vertical blanking pulse as described above. Since BLK1 detects the level of the video signal, the timing is set so that a period wider than the vertical blanking period is blanked, and BLK2 malfunctions for various signals superimposed by the broadcasting station during the vertical blanking period. In order not to do so, the period is as short as the rear equalization pulse period. Other embodiments

Although the above description has been made on the case where control is performed only on the luminance signal, the present invention is also performed on the color signal.
Examples will be described below. In the case of a color signal, important factors are the hue and the color saturation. Here, the detection of the I axis, that is, the hue and the color saturation of the flesh color will be described first with reference to FIG.

FIG. 8 shows a vector of hue and color saturation, and the color saturation is constant on a unit circle. I axis is 12
3 degrees and the Q axis is 33 degrees. It is assumed that a circuit (not shown) for demodulating a chroma signal into a color difference signal is an I and Q axis demodulation circuit. The demodulated output of the I-axis demodulation circuit becomes maximum when the hue is on the I-axis if the color saturation is constant. Similarly, in the Q-axis demodulation circuit, it becomes maximum when the hue is on the Q-axis. Now, the I-axis demodulated output is divided into three, and divided into three zones shown in FIG.
The zone from the maximum level obtained by demodulating a color saturation signal having a burst chroma ratio of 1: 0.5 to the maximum level obtained by demodulating a signal having a color saturation of 1: 1 is defined as I zone 1. Similarly, I-zone 2 is from 1: 1 to 1: 1.5, and I-zone 3 is the maximum demodulation level of 1: 1.5 or more. The output of the Q-axis demodulation circuit is divided into six zones as shown in FIG. The outside thereof is Q zone 2 (consisting of two blocks), and the outside of Q zone 2 is Q zone 3. The positive / negative Q-axis maximum output obtained by demodulating the color saturation signal having a burst chroma ratio of 1: 0.75 is set as the maximum value of the Q zone 3,
The range obtained by dividing this range into six is allocated to each Q zone as described above.

This makes it possible to detect whether the hue of the demodulated chroma signal exists in a certain range near the I axis. When the output level of the I and Q demodulation circuits is I
If in zone 1 and Q zone 1, I zone 2
And in Q zones 1 and 2, and I zone 3
In addition, the number of occurrences in the field is counted by detecting the case in the Q zones 1 to 3. Detection of this combination can be easily realized by modifying the circuit of FIG. 7 for the I-axis and the Q-axis and combining them by an AND circuit. CP
By taking it into U18, it is possible to detect how many components near the I axis are present in the field and control various circuits.

Although there are various objects to be controlled, control of the chroma demodulation band and feedback to the luminance signal processing are raised. When there are many I-axis components, the I and Q-axis demodulation circuits may be controlled so as to widen the chroma demodulation band. Also,
In the case where the I-axis component is large, if the transmission DC level of the luminance signal is increased or the contrast is increased using the correction or the contrast or the ACL of the luminance signal, the problem of darkening of the skin color can be improved.

Also, good results can be obtained even when used for demodulation axis (skin color) correction such as a so-called fresh tone. In the conventional circuit, whether or not the signal is in the vicinity of the I axis is determined in binary, so that the hue correction range is shifted between a case where the color saturation is low and a case where the color saturation is high. However, the flesh color neighboring components detected by the combination as described above in FIG. 8 are shaded ranges in FIG. 8 and vary in accordance with the level, so that the hue range is constant at any color saturation.
In the example of FIG. 8, ± 27 degrees of the I axis is detected. Therefore, the effect of correction can be stabilized irrespective of the color saturation, and weighting can be intentionally added.

Even if the demodulation circuit does not use the I and Q axes,
As long as the axis is demodulated, the detection of the I axis can be performed by vector synthesis. Similarly, it is also possible to detect other hues and operate the luminance and color difference signals only for specific colors.

FIG. 9A and FIG.
This will be described with reference to FIG. In recent years, the image quality of liquid crystal TVs has also become higher, and some ICs have been developed exclusively for liquid crystals. The liquid crystal TV has a narrow display dynamic range of the liquid crystal panel, and does not have a blooming phenomenon which occurs in a Brownian (B) tube TV. Therefore, if the white or black gradation exceeds the dynamic range, the image is completely collapsed and no image is displayed. When displaying on such a display, the signal near the intermediate luminance cannot be fully utilized only by the function of the ACL. In such a case,
A circuit for expanding a signal near the intermediate luminance as shown in FIG. 9A is required. This circuit is an example of a circuit having an expansion characteristic. The amplifier including the transistors Q11 and Q12 and the resistor R6 is the main amplifier, and the transistor Q1
The amplifier composed of Q3, Q14 and resistor R7 is an amplifier of intermediate luminance.

The input luminance signal Yin is supplied to the input terminal 61. This luminance signal Yin is supplied to transistors Q11 and Q11.
13 bases. Transistors Q11, Q1
The two emitters are connected via a resistor R6 and to the ground line via current sources I3 and I4, respectively. The collector of the transistor Q11 is connected to a power supply line, and the emitter of the transistor Q12 is supplied with a bias voltage V1. The collector of the transistor Q12 is connected to the output terminal 62, and is connected to the power supply line via the resistor R8 together with the collector of the transistor Q14. Transistors Q13 and Q14
Is connected via a resistor R7, and the emitter of the transistor Q14 is further connected to a ground line via a current source I5. The collector of the transistor Q13 is connected to a power supply line, and the base of the transistor Q14 is supplied with a bias voltage V2.

When the input luminance signal Yin exceeds the bias voltage V1.
Rises, Yin is amplified by the main amplifier and appears at R8. Until Yin reaches V2, transistor Q13 is cut off and transistor Q14
, A constant current I5 flows. When Yin rises above V2, the transistor Q13 conducts, and the amplified signal from the main amplifier and the transistors Q13 and Q14 are connected to the resistor R8.
Output the sum signal of the amplified signals from the amplifiers. The input dynamic range of the intermediate luminance amplifier of the transistors Q13 and Q14 is determined by I5 × R7. When the input level exceeds this range, the transistor Q14 is cut off and only the signal from the main amplifier appears at R8. Therefore, the gain increases only during the period when the intermediate luminance amplifier is active, and the input / output characteristics are as shown by the broken line in FIG.

Since the intermediate luminance signal is an important factor for determining the quality of an image, care must be taken in control. Zone 1
This signal is preferably used only when there is not much signal and the signal is concentrated in the zone 2 or 3 and the white peak can be detected even if the intermediate luminance is extended by the white peak detecting means as shown in FIG.

[0048]

As described above, according to the present invention, the level of an input video signal is detected,
The central control circuit sets a high-quality circuit such as white extension in an optimal state, and can obtain a high-quality image in response to a difference between displays and the strength of an electric field.

[Brief description of the drawings]

FIG. 1 is a diagram showing a reference example on which the present invention is based .

FIG. 2 is a waveform diagram used to explain the operation of the discriminating circuit of FIG. 1 and a characteristic diagram used to describe the operation of the individual circuit of FIG.

FIG. 3 is a block diagram showing a modification of the determination circuit shown in FIG. 1 and waveform diagrams for explaining the operation thereof.

FIG. 4 is a circuit diagram showing a specific example of a blackout detection circuit and a waveform diagram for explaining the operation thereof.

FIG. 5 is a circuit diagram showing a specific example of a whiteout detection circuit and a waveform diagram for explaining the operation thereof.

FIG. 6 is a characteristic diagram used to explain an example of the operation of the CPU and the ACL control characteristics in FIGS. 1 and 3;

FIG. 7 is a circuit diagram showing a specific example of a level determination circuit.

FIG. 8 illustrates a level determination principle according to an embodiment of the present invention.
The hue characteristic diagram shown for clarity.

Figure 9 is a circuit diagram showing an example of a luminance decompression circuit according to the present invention
And its characteristic diagram .

FIG. 10 is a block diagram for explaining a conventional luminance signal processing circuit, and a correction characteristic diagram and a signal waveform diagram in the circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Clamp circuit, 2 ... Black expansion circuit, 3 ... DC transmission amount correction circuit, 4 ... Contrast circuit, 5 ... ALC, 6 ... Bright circuit, 7 ... Black loss detection circuit, 8 ... White loss detection circuit, 9, 10 , 11 DC control circuit, 12 latch circuit, 13 counter, 14 level discriminating circuit, 15-1
7 zone controller, 18 control circuit, 19 RAM.

Claims (2)

(57) [Claims] 1. A color difference signal output from a chroma demodulation circuit is detected as to which of a plurality of preset zones is based on hue and color saturation, and each signal detected for each zone is detected. A level distribution detecting means for generating a pulse output according to the component; controlling a demodulation band of the chroma signal demodulation circuit based on a result of each detection output of the level distribution detecting means; A video signal processing device comprising: a control unit that controls an operating point of a luminance signal processing unit that performs at least one of the processes. 2. The apparatus according to claim 1, wherein the level distribution detecting means includes means for detecting a component near the I-axis of the color difference signal, and a conversion circuit for converting an I-axis detection result into a pulse. 2. The video signal processing device according to claim 1, wherein an operation point of the luminance signal processing unit is controlled.