JP4004232B2 - Video signal processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a video signal processing apparatus capable of correcting a level of a luminance signal included in a digitized video signal and displaying a clear image in a television receiver or the like.
[0002]
[Prior art]
In an television receiver, in an image with few black portions, the black portion in the screen is lifted from the surrounding portion, and the image has no sharpness. In order to prevent this, black level correction is performed. Black level correction is correction that extends in the black direction so that the blackest part of the input luminance signal approaches the reference level, and its input / output characteristics are as shown in FIG. Conventionally, black level correction has been performed by an analog circuit including a transistor, a resistor, and the like.
[0003]
[Problems to be solved by the invention]
In recent years, in order to increase the integration of television signal processing circuits, it has been required to digitize and digitally process video signals. Therefore, it is necessary to perform the above black level correction not by an analog circuit but by a digital circuit having a memory such as a ROM for storing digital data representing input / output characteristics.
[0004]
However, in order to realize the non-linear input / output characteristics as shown in FIG. 4 with a digital circuit, a large-capacity memory is required, and there is a problem that the manufacturing cost increases. An object of the present invention is to reduce the capacity of a memory necessary for a digital circuit that performs black level correction of a digital luminance signal.
[0005]
[Means for Solving the Problems]
According to one aspect of the present invention, a video signal processing apparatus for correcting the black level of the digital luminance signal included in the digital video signal, storing the output characteristic data for nonlinear converting the digital luminance signal input A memory means, a comparing means for comparing the value of the input digital luminance signal with a first fixed value, a non-linearly transformed digital luminance signal value and a second fixed value output from the memory means. Switching means for selecting and outputting one of them according to the comparison result of the comparison means, and multiplying means for multiplying the output of the switching means and the inputted digital luminance signal , the memory means comprising a plurality of Different input / output characteristic data are stored, and the input / output characteristics corresponding to the value of the first control signal supplied from the outside among the plurality of different input / output characteristic data Data is supplied to the switching means as the non-linearly converted digital luminance signal, and the plurality of different input / output characteristic data are values of the non-linearly converted digital luminance signal output from the memory means by the switching means. Data for changing a black level correction start point that is a boundary point between the black level correction range to be selected and output and the black level fixed range to be output by the switching means selecting and outputting the second fixed value. Features.
[0006]
The invention according to claim 2 further comprises gate means for outputting a logical sum of the output of the comparison means and a second control signal supplied from the outside, and the switching means is a value of the output of the gate means. According to the above, one of the non-linearly converted digital luminance signal output from the memory means and the second fixed value is selected and output.
[0007]
According to a third aspect of the present invention, there is provided a video signal processing apparatus for correcting a black level of a digital luminance signal included in a digital video signal, and storing input / output characteristic data for nonlinearly converting the inputted digital luminance signal. A memory means, a comparing means for comparing the value of the input digital luminance signal with a first fixed value, a non-linearly transformed digital luminance signal value and a second fixed value output from the memory means. Switching means for selecting and outputting one of them according to the comparison result of the comparison means, multiplication means for multiplying the output of the switching means and the input digital luminance signal, and the output of the comparison means from the outside and a gate means for outputting the logical sum of the second control signal supplied, the switching means, said memory means in accordance with the value of the output of said gate means Characterized by one selected and the output of the nonlinear converted digital luminance signal and the second fixed value is et output.
According to a fourth aspect of the present invention, the memory means stores a plurality of different input / output characteristic data, and the first control signal supplied from outside of the plurality of different input / output characteristic data. Input / output characteristic data corresponding to a value is supplied to the switching means as the non-linearly converted digital luminance signal.
[0008]
The invention according to claim 5 is characterized in that the second control signal and the output of the comparison means are each a 1-bit signal.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
Embodiment 1 FIG.
FIG. 1 is a schematic block diagram showing the configuration of a video signal processing apparatus according to Embodiment 1 of the present invention. In the figure, 1 is a ROM, 2 is a comparator, 3 is a switching means, and 4 is a multiplier.
[0010]
In FIG. 1, the ROM 1 includes a total of 2 bits including the lower 7 bits of the 8-bit input digital luminance signal Y-IN and a 2-bit control signal BLK-S-Point for setting a black level correction start point described later. A 9-bit signal is input. The ROM 1 outputs an 8-bit signal having a value corresponding to the value of the 9-bit signal.
[0011]
The 8-bit digital luminance signal Y-IN is also input to the comparator 2, and the comparator 2 compares the value of the digital luminance signal with a fixed value such as “7FH”. The comparator 2 outputs a signal “1” when the value of the digital luminance signal is larger than “7FH”, and sends a signal “0” to the switching means 3 as a switching signal in other cases.
[0012]
In the switching means 3, the 8-bit signal output from the ROM 1 is input to one input terminal, and a fixed value, for example, “FFH” that is the maximum value of the 8-bit signal is input to the other input terminal. . The switching means 3 selects the output signal of the ROM 1 when the switching signal from the comparator 2 is “0”, and selects the fixed value “FFH” when the switching signal from the comparator 2 is “1”. .
[0013]
The multiplier 4 multiplies all 8 bits of the input digital luminance signal Y-IN by 8 bits output from the switching means 3, and outputs a 16-bit signal as a multiplication result. Of the 16-bit output of the multiplier 4, the upper 8 bits are output to the outside as the luminance signal Y-OUT with the black level corrected.
[0014]
FIG. 3 shows input / output characteristics of the ROM 1. As shown in FIG. 3, when the 9-bit input signal input to the ROM 1 is between “00H” and “7FH”, the value of the 8-bit output signal is increased by the value of the input signal. Accordingly, it starts from “FFH” and once decreases to “00H”, then returns to “FFH” again. Even when the 9-bit input signal is between “80H” and “FFH”, between “100H” and “17FH”, or between “180H” and “1FFH”, the value of the 8-bit output signal is the same. Although it changes, the point to return to 'FFH' is different. Each of the points (a), (b), (c), and (d) returning to “FFH” of these four types of input / output characteristics is a point at which black level correction is started.
[0015]
Which of the above four input / output characteristics divided by the broken line in FIG. 3 is used is determined by a 2-bit control signal BLK-S-Point. For example, when this signal is “00”, the input / output characteristics in the range of “00H” to “7FH” are used. In this case, the point (a) is “7FH”, and the black level correction start point is The input luminance level is 50 IRE. Further, when the points (b), (c), and (d) are “E6H”, “14DH”, and “1B4H”, respectively, the control signal BLK-S-Point is set to “01”, “10”, or “11”. If ', then the black level correction start point can be set to 40 IRE, 30 IRE, or 20 IRE.
[0016]
FIG. 4 shows the input / output characteristics of the luminance signal of the apparatus of the first embodiment when the control signal BLK-S-Point is “00”. As described above, the output luminance signal (the upper 8 bits of the 16-bit signal obtained by multiplying the 8-bit output of the switching means 3 and the 8-bit of the input digital luminance signal) is 50IRE as shown in FIG. At the following input levels, it is expanded in the black direction.
[0017]
In the first embodiment, in the linear part of the input / output characteristic that does not require level correction (for example, the part exceeding 50 IRE), the switching means 3 selects a fixed value instead of the output of the ROM 1, so that this is stored in the ROM 1. It is not necessary to store data corresponding to the linear portion, and accordingly, the capacity can be reduced accordingly.
[0018]
Embodiment 2. FIG.
FIG. 2 is a schematic block diagram showing the configuration of the video processing apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or equivalent parts as those in the first embodiment. The second embodiment is different from the first embodiment in that an OR gate 5 is provided.
[0019]
The operations of the ROM 1, the comparator 2, the switching unit 3, and the multiplier 4 shown in FIG. 2 are the same as those in the first embodiment. That is, the switching means 3 is configured such that the 8-bit output of the ROM 1 is input to one input terminal, a fixed value ('FFH') is input to the other input terminal, and the output of the OR gate 5 is '0'. The output signal of the ROM 1 is selected, and when the output of the OR gate 5 is “1”, the fixed value is selected. The multiplier 4 multiplies all 8 bits of the digital luminance signal Y-IN and 8 bits output from the switching means 3 and outputs a 16-bit signal. Of the 16-bit output of the multiplier 4, the upper 8 bits are output to the outside as the luminance signal Y-OUT with the black level corrected.
[0020]
On the other hand, the OR gate 5 has one input terminal to which the output of the comparator 2 is input, and the other input terminal to the 1-bit control signal BLK-S-on / indicating whether or not to perform black level correction. off is supplied. As a result, when the control signal is “1”, the switching signal supplied from the OR gate 5 to the switching means 3 is always “1” regardless of the output of the comparator 2, and the switching means 3 has the fixed value. Select ('FFH'). Therefore, in this case, since the input luminance signal is multiplied by this fixed value, the input / output characteristics show linearity even in the low luminance portion as shown by the broken line in FIG.
[0021]
In the second embodiment, a circuit for switching and outputting an 8-bit input luminance signal with black level correction and an 8-bit luminance signal without black level correction is unnecessary, and the control signal BLK-S- Since it can be configured by only a gate that outputs an OR of one bit of on / off and one bit of the comparator output, the circuit configuration is simplified.
[0022]
In the first and second embodiments described above, the input / output digital luminance signal is 8 bits, the input to the ROM 1 is 9 bits, and the output from the ROM 1 is 8 bits. However, the number of bits is limited to these. For example, both the input and output digital luminance signals can be 10 bits, the input to the ROM can be 11 bits, and the output from the ROM can be 10 bits.
[0023]
In the first and second embodiments, the gradation number of input / output in the ROM 1 is made equal. For example, the output from the ROM 1 is set to 7 bits, and the gradation of the gradation at the time of black level correction is made rough so that the capacity of the ROM 1 is increased. Can be further reduced.
[0024]
【The invention's effect】
According to the first and third aspects of the present invention, in the linear part of the input / output characteristic that does not require level correction, a fixed value is selected instead of the output of the memory means by the switching means. There is no need to store corresponding data, and accordingly the capacity of the memory means can be reduced accordingly.
[0025]
According to the first and fourth aspects of the invention, it is possible to adjust the start point of black level correction.
[0026]
According to the second and third aspects of the present invention, it is possible to switch and output a luminance signal without black level correction and a luminance signal with black level correction by a simple circuit.
[0027]
According to the fifth aspect of the present invention, the circuit for switching between the luminance signal for which the black level is not corrected and the luminance signal for which the black level is corrected is configured by an OR gate that outputs a logical sum of two 1-bit signals. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a configuration of a first embodiment of a video signal processing apparatus of the present invention.
FIG. 2 is a schematic block diagram showing a configuration of a second embodiment of a video signal processing apparatus of the present invention.
FIG. 3 is an explanatory diagram of input / output characteristic data stored in a ROM of the devices according to the first and second embodiments.
FIG. 4 is a diagram showing input / output characteristics of luminance signals of the devices of the first and second embodiments.
[Explanation of symbols]
1 ROM, 2 comparator, 3 switching means, 4 multiplier, 5 OR gate.

Claims (5)

In a video signal processing apparatus for correcting a black level of a digital luminance signal included in a digital video signal,
Memory means for storing input / output characteristic data for nonlinear conversion of the input digital luminance signal;
Comparing means for comparing the value of the input digital luminance signal with a first fixed value;
Switching means for selecting and outputting one of the value of the non-linearly converted digital luminance signal output from the memory means and the second fixed value according to the comparison result of the comparing means;
Multiplying means for multiplying the output of the switching means and the input digital luminance signal ,
The memory means stores a plurality of different input / output characteristic data, and the input / output characteristic data corresponding to the value of the first control signal supplied from the outside among the plurality of different input / output characteristic data is Supplied to the switching means as a non-linearly converted digital luminance signal;
The plurality of different input / output characteristic data includes a black level correction range in which the switching means selects and outputs a value of a non-linearly converted digital luminance signal output from the memory means, and the switching means outputs the second level data. A video signal processing apparatus, characterized in that it is data for changing a black level correction start point, which is a boundary point with a black level fixed range to be selected and output . Gate means for outputting a logical sum of the output of the comparison means and a second control signal supplied from the outside is further provided, and the switching means is output from the memory means in accordance with an output value of the gate means. 2. The video signal processing apparatus according to claim 1, wherein one of the non-linearly converted digital luminance signal and the second fixed value is selected and output. In a video signal processing apparatus for correcting a black level of a digital luminance signal included in a digital video signal,
Memory means for storing input / output characteristic data for nonlinear conversion of the input digital luminance signal;
Comparing means for comparing the value of the input digital luminance signal with a first fixed value;
Switching means for selecting and outputting one of the value of the non-linearly converted digital luminance signal output from the memory means and the second fixed value according to the comparison result of the comparing means;
Multiplying means for multiplying the output of the switching means and the input digital luminance signal;
Gate means for outputting a logical sum of the output of the comparison means and a second control signal supplied from the outside ,
Said switching means, you characterized in that selects and outputs one of the non-linear transformed digital luminance signal and the second fixed value is outputted from the memory means in accordance with the value of the output of said gate means Film image signal processing apparatus. The memory means stores a plurality of different input / output characteristic data, and the input / output characteristic data corresponding to the value of the first control signal supplied from the outside among the plurality of different input / output characteristic data is 4. The video signal processing apparatus according to claim 3, wherein the switching unit is supplied as a non-linearly converted digital luminance signal. Video signal processing apparatus according to any one of claims 1 to 3, characterized in that the output of the second control signal and the comparison means are each 1-bit signal.

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