JP2004120113A - Video processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video processing apparatus capable of displaying an excellent video without deterioration in the gradation of a dark part even on a linear display apparatus. <P>SOLUTION: The video processing apparatus is provided with: a zone discrimination section that discriminates whether or not to any one zone among zones with a plurality of quantization sized widths prepared in advance a quantized size of an input video signal quantized in L (L is an integer of 1 or over) bits is applicable; a bit revision section that quantizes the input video signal of each zone divided by the zone discrimination section in M (M is an integer and M>L) bits so that the amplitude per bit is smaller than the amplitude quantized in the L bits; a magnification conversion section that weights the input video signal of each zone quantized in the M bits according to the amplitude of the input video signal of each zone to add a weight to the input video signal; and an interface section that uses the input video signal to which the magnification conversion section adds the weight to produce a video display signal displayed on a display apparatus. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is suitable for a linear display device such as a PDP (Plasma Display Panel), a FED (Field Emission Display; Field Emission Display), and a DMD (Digital Micro-mirror Device; Digital Micromirror Device). The present invention relates to a video processing device that realizes video display.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, image signals such as television signals have been subjected to non-linear processing called gamma correction in advance in consideration of display characteristics of a cathode ray tube (CRT) in consideration of display characteristics of the cathode ray tube (CRT) on the premise of display on a cathode ray tube (CRT). Therefore, when the display device is a CRT, a correct (linear) luminance gradation can be obtained without correction. However, in the case of a display device other than a CRT such as PDP, FED, DMD, etc., a linear luminance gradation is obtained. It is necessary to perform optimal gamma correction for each display device in order to obtain gradation. For example, in the case of a PDP, it is necessary to provide a gamma correction circuit to perform inverse gamma correction because it has a light emission characteristic that is approximately proportional to an input signal, and the same applies to FEDs and DMDs.
[0003]
Here, a flow of processing when displaying an image on the PDP 55 will be described with reference to FIG. First, the analog / digital (A / D) converter 52 converts an analog video signal input from the input terminal 51 into a digital signal. Further, when the input video signal is interlaced, the pixel conversion unit 53 converts the input video signal into a progressive one and converts the number of pixels in the horizontal and vertical directions into the number of display pixels of the PDP 55. Then, when the conversion process by the pixel conversion unit 53 is completed, the inverse gamma correction unit 54 performs inverse gamma correction for displaying the input video signal on the PDP 55, performs predetermined signal processing in the signal processing unit 56, A subfield conversion unit 57 divides the input video signal into a plurality of subfield configurations. Thereafter, the drive unit 58 generates a signal for driving the PDP 55 based on the video signal, and the video is displayed on the PDP 55.
[0004]
The inverse gamma correction section 54 is different from the standard gamma correction characteristic (for example, gamma value: 1 / 2.2) of the CRT shown in FIG. , Gamma value: 2.2), an image is displayed on the PDP 55 with a linear luminance gradation as shown in FIG.
[0005]
[Patent Document 1]
JP-A-6-311394
[Patent Document 2]
Japanese Patent Application Laid-Open No. H10-113848
[Patent Document 3]
JP 10-013849 A
[Patent Document 4]
JP 10-153983 A
[Problems to be solved by the invention]
Normally, in image display using a CRT, the number of gradations of an image signal input to the CRT is 8-bit, 256 gradations is practically sufficient. However, for the purpose of CRT reverse gamma correction, 256 gradations are required. Even so, the ratio between the minimum value and the maximum value of the actual light emission luminance is larger than 1: 256.
[0010]
On the other hand, in the image display using the PDP, the gradation is controlled by the number of times of light emission in the subfield, and the light emission luminance is substantially proportional to the number of times of light emission. The ratio of the minimum value to the maximum value is 1: 256. For this reason, in the image display using the PDP, the contrast is insufficient compared with the case where the CRT is used, and particularly, the gradation is insufficient in a dark part (low luminance area) of the image.
[0011]
To solve such a problem, the bit width of the input video signal is increased, for example, from 8 bits to 9 bits or 10 bits, and the quantization error (indicating one step gradation or resolution) is ２ ，, 1 A method of increasing both the contrast and the number of gradations by improving the accuracy to / 4 is conceivable, but the circuit scale increases accordingly.
[0012]
In subfield driving used in PDPs and the like, an increase in the number of bits leads to an increase in the number of subfields, but an increase in the number of subfields per one field (16.7 ms) time is limited. Problems such as lowering occur.
[0013]
As described above, in a linear display device such as a PDP, FED, or DMD, when the same signal processing is performed over the entire video signal area (white to black) and the same quantization error occurs, the contrast is insufficient. Then, the gradation of the dark part (black side) is deteriorated.
[0014]
The present invention has been made in view of the circumstances described above, and has a low dynamic range and a low contrast ratio even in a linear display device such as PDP, FED, DMD, etc., as compared with a CRT. It is an object of the present invention to provide a video processing device capable of displaying a good video without deterioration of gradation.
[0015]
[Means for Solving the Problems]
The video processing device according to the present invention applies the quantization size of the input video signal quantized with L bits (L is an integer of 1 or more) to a zone having a plurality of quantization size widths prepared in advance. And an M-bit (M is an integer) such that the input video signal of each zone divided by the zone discrimination unit is smaller in amplitude value per bit than the amplitude value quantized by L bits. And M> L), and weighting the input video signal of each zone quantized by M bits by the bit changing unit according to the amplitude value of the input video signal of each zone, A magnification conversion unit that adds the weight, and an interface unit that generates a video display signal to be displayed on a display device using the input video signal weighted by the magnification conversion unit. And butterflies.
[0016]
According to such a configuration, the zone determination unit determines which of the zones having a plurality of quantization size widths the quantization size of the input video signal quantized by L bits applies to, and performs magnification conversion. The unit assigns weights to the input video signal of each zone quantized by M bits by the bit changing unit for each zone according to the amplitude value, so that the quantization error can be arbitrarily changed for each zone. Therefore, for example, without increasing the bit width of the input video signal, it is possible to improve the accuracy of a quantization error in a dark portion of an image, and to realize a favorable video display without deterioration in gradation. .
[0017]
Note that the video processing device may include an inverse gamma correction unit that performs inverse gamma correction on the input video signal quantized with L bits and outputs the result to the zone determination unit. Further, instead of the inverse gamma correction unit, an input / output characteristic correction unit that performs a correction process on an input video signal according to the input / output characteristics of the display device may be provided.
[0018]
In the video processing apparatus, the zone determination unit may convert the quantization size of the input video signal quantized by L bits into a plurality of zones equally divided into a plurality of quantization size widths, or a plurality of quantization sizes. It is determined whether any one of a plurality of zones divided in geometric series into widths is applicable. When the number of equal divisions is N (N> 0), the quantization error can be made up to 1 / N times, and the geometric series 1 / N ⁰ , 1 / N ¹ , 1 / N ² ,. 1 / in ^{n n (n} + 1) when dividing the number of zones can be maximized 1 / ^{n n} times the quantization error.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. It should be noted that the same or equivalent parts and components are denoted by the same or equivalent reference symbols throughout the drawings, and the description thereof will be omitted or simplified.
[0020]
[First Embodiment]
[Configuration of video processing device]
As illustrated in FIG. 1, the video processing device includes an analog / digital (A / D) conversion unit 2, an inverse gamma correction unit 3, a bit change unit 4, a zone determination unit 5, a signal processing unit 6, and a magnification conversion unit 7. , An interface unit 8, a display unit 9, and the like.
[0021]
The A / D converter 2 converts the input video signal input from the input terminal 1 into a digital signal, and the inverse gamma corrector 3 converts the digital signal into a digital signal and quantizes it with L bits in an L-bit width (L is 1 or more). Inverse gamma correction is performed on the input video signal of The zone discriminating unit 5 determines the quantization size of the input video signal, which has been subjected to the inverse gamma correction by the inverse gamma correction unit 3 and quantized by L bits, to a zone having a plurality of quantization size widths prepared in advance. It is determined whether any one of the zones is applicable. The bit changing unit 4 converts the input video signal of each zone divided by the zone determining unit 5 into M bits (M is an integer) such that the amplitude value per bit is smaller than the amplitude value quantized by L bits. Yes, M> L). The signal processing unit 6 performs predetermined signal processing on the input video signal of each zone quantized by M bits. The magnification converter 7 weights the input video signal of each zone quantized by M bits according to the amplitude value of the input video signal of each zone, and adds a weight. The interface unit 8 generates a video display signal to be displayed on the display unit 9 using the input video signal weighted by the magnification conversion unit 7. The display unit 9 is, for example, a linear display such as a PDP, FED, and DMD.
[0022]
[Operation of video processing device]
Next, the processing operation of the video processing device will be described with reference to the flowchart shown in FIG.
[0023]
The process illustrated in the flowchart of FIG. 2 is started when a video signal is input to the input terminal 1.
[0024]
In the process of step S1, the A / D converter 2 converts an input video signal input from the input terminal 1 into a digital signal, and outputs the digitally converted input video signal to the inverse gamma correction unit 2. Here, a description will be given assuming that the bit width L of the input video signal converted into a digital signal is 12 bits.
[0025]
In the process of step S2, the inverse gamma correction unit 3 performs inverse gamma correction for displaying the input video signal on the display unit 9 according to the 12-bit inverse gamma correction characteristic illustrated in FIG. The subsequent input video signal is output to the zone determination section 5.
[0026]
In the process of step S3, the zone discriminating unit 5 divides the quantized size of the input video signal quantized by 12 bits input from the inverse gamma correction unit 2 into three equal parts as illustrated in FIG. Of each of the zones, A zone (low-brightness area), B zone (middle-brightness area), and C zone (high-brightness area). The input video signals La, Lb, Lc are output to the bit changing section 4.
[0027]
(1) Zone A: La (level 0 to level 4091)
(2) B zone: Lb (level 0 to level 2727)
(3) C zone: Lc (level 0 to level 1364)
When zone determination is performed according to the amplitude level of the input video signal, the zone determination unit 5 determines each zone of the input video signal based on pixels, lines, and fields. Specifically, when determining for each line or field, the zone determination unit 5 performs zone determination in the order of A zone, B zone, and C zone, and sets the input video signal of A zone in the target line or field. Is present, the input video signal of zone A and zone A is not present, and the input video signal of zone B is present. If the input video signals of zone B, zone A and zone B are not present, zone C is present. Determine.
[0028]
In the process of step S4, the bit changing unit 4 converts the input video signals La, Lb, Lc of each of the zones A, B, C divided by the zone discriminating unit 5 into amplitudes quantized by L bits (12 bits). It quantizes with M bits (8 bits) so that the amplitude value per bit becomes smaller than the value, and outputs the input video signals Ma, Mb, Mc quantized with 8 bits to the signal processing unit 6.
[0029]
(1) Zone A: La (level 0 to 4091) → Ma (level 0 to 256)
(2) Zone B: La (level 0 to 2727) → Mb (level 0 to 256)
(3) C zone: La (level 0 to 1364) → Mc (level 0 to 256)
In the process of step S5, the signal processing unit 6 uses the same signal processing circuit between the input video signals of each zone to convert the input video signals Ma, Mb, Mc of each zone input from the bit changing unit 4 into the same. Signal processing is performed by bit processing (M-bit processing), and the input video signals Ma, Mb, Mc of each zone subjected to the signal processing are output to the magnification conversion unit 7.
[0030]
In the process of step S6, the magnification converter 7 converts the input video signal Ma of the A zone, the input video signal Mb of the B zone, and the input video signal Mc of the C zone input from the signal processor 6 as shown in FIG. , A weighting coefficient is added according to the amplitude level. Specifically, as shown below, the magnification conversion unit 7 triples the input video signal Ma in the A zone, doubles the input video signal Mb in the B zone, and increases the input video signal Mc in the C zone by one time. Then, the input video signals Ma, Mb, and Mc of the respective zones subjected to the magnification conversion are output to the interface unit 8.
[0031]
(1) A zone: Ma (level 0 to 256) × 3
(2) B zone: Mb (level 0 to 256) × 2
(3) C zone: Mc (level 0 to 256) × 1
Here, the quantization error of the input video signal having an amplitude level belonging to the C zone in the low luminance area is 1/3 times as compared with a case where the entire amplitude is quantized by 8 bits (256 levels). Therefore, the resolution of the dark part (black side) is improved by a factor of three, and both the gradation and the contrast can be improved by a factor of three.
[0032]
In the process of step S7, the interface unit 8 responds to the characteristics of the display unit 9 by, for example, time-sharing the input video signal input from the magnification conversion unit 7 into eight subfields if the display unit 9 is a PDP. The conversion process is performed, and the result is displayed on the display unit 9.
[0033]
In the present embodiment, the zone determination unit 5 equally divides the input video signal into three zones, that is, the A zone, the B zone, and the C zone, but the zone division method is generalized as follows. It is possible. For example, as shown in FIG. 6, the input video signal is divided into zones A, B, C,..., Z, the amplitude ratio of the minimum zone Z is set to 1, and each of the zones A, B, C,. The zones are divided by setting the amplitude ratio to a, b, c,..., 1. Then, the magnification converter 7 may set the weighting coefficients for the zones A, B, C,..., Z as a, b, c,.
[0034]
[Second embodiment]
In the first embodiment, an example has been described in which the zone determination unit 5 determines an input video signal having an L bit width and divides the input video signal into a plurality of zones according to the amplitude level. In the second embodiment, an example in which geometric series are divided into a plurality of zones according to the amplitude level will be described.
[0035]
As illustrated in FIG. 7, the zone determination unit 5 divides the quantization size of the input video signal quantized by L bits input from the inverse gamma correction unit 2 into a plurality of quantization size widths in a geometric series. It is determined whether each of the selected zones, the A zone, the B zone, the C zone, the D zone, and the E zone is applicable, and the input video signals La, Lb, and Lc of each zone are changed by the bit changing unit 4. Output to Specifically, it is divided into (n + 1) zones by the geometric series 1 / N ⁰ , 1 / N ¹ , 1 / N ² ,..., 1 / N ⁿ (where N <0). As described above, when performing zone division with the equal division number N (N> 0) according to the amplitude level, the quantization error can be made up to 1 / N times at the maximum, and the amplitude value can be reduced to the geometric series 1 / N ⁰ , 1 /. When dividing into (n + 1) zones by N ¹ , 1 / N ² ,..., 1 / N ⁿ , the quantization error can be made up to 1 / N ⁿ times at the maximum.
[0036]
Specifically, as shown in FIG. 7, the zone determination unit 5, a N = 1/2, geometric series ^{1/2 0, 1/2 1,} 1/2 2, ^1/2 3, 1 / 2 ⁴ (4 + 1) number of zones a, divides B, C, D, and E. Then, the magnification converter 7 sets the weighting coefficients for the zones A, B, C, D, and E to 1, 1/2, 1/4, 1/8, and 1/16. By performing zone division in this manner, for example, the quantization error of an input video signal having an amplitude level belonging to the E zone is 1 / N ⁴ compared to a case where the entire amplitude is quantized by 8 bits (256 levels). Double. Therefore, the resolution of the dark part (black side) can be improved accuracy N ⁴ times, to improve both the tone and contrast N ⁴ times.
[0037]
Incidentally, as illustrated in FIG. 7, as N = 1/2, geometric series ^{1/2 0, 1/2} 1, 1/2 ^{2, 1/2} 3, ^{1/2 4} to five zones A , B, C, D, and E, assuming that the input video signal output from the inverse gamma correction unit 3 has a 12-bit width, as shown in FIG. 8, the MSB (Most Significant Bit; The eight bits selected while shifting one bit at a time in order from the upper bit) correspond to the zones A, B, C, D, and E, respectively. The bit changing unit 4 can quantize the input video signal of each of the zones A, B, C, D, and E quantized by 12 bits by 8 bits by such a simple bit operation.
[0038]
As is clear from the above description, the zone discriminating unit 5 discriminates the input video signal, divides the zone according to the amplitude value, and the magnification conversion unit 7 adds a weighting coefficient according to the amplitude value for each zone, thereby obtaining It is possible to arbitrarily change the quantization error. Therefore, for example, without increasing the bit width of the input video signal, it is possible to improve the accuracy of a quantization error in a dark portion of an image, and to realize a favorable video display without deterioration in gradation. .
[0039]
Although the embodiments of the present invention have been described in detail, the present invention can be embodied in various other forms without departing from the spirit or main features thereof.
[0040]
For example, as shown in FIG. 10, the inverse gamma correction unit 3 can be replaced with an input / output characteristic correction unit 13. The input / output characteristic correction unit 13 performs correction according to input / output characteristics specific to each display as illustrated in FIG. According to such a configuration, the present invention can be applied not only to a display device such as a PDP but also to other types of display devices.
[0041]
In the above-described embodiment, an example in which an input video signal quantized by 12 bits is quantized by 8 bits has been described. However, an input video signal quantized by 14 bits is quantized by 10 bits. Can be changed as appropriate.
[0042]
As described above, the above-described embodiment is merely an example in every aspect, and should not be construed as limiting. The scope of the present invention is defined by the appended claims, and is not limited by the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.
[0043]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the favorable image display which does not have deterioration of the gradation of a dark part can be implement | achieved, without increasing the circuit scale of a digital signal processing circuit.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of a video processing device according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a processing operation of the video processing device shown in FIG. 1;
FIG. 3 is a diagram showing an example of an inverse gamma correction characteristic of an inverse gamma correction unit in the video processing device shown in FIG.
FIG. 4 is a diagram for explaining an example of zone division according to the first embodiment.
FIG. 5 is a diagram illustrating an example of a magnification conversion process performed by a magnification conversion unit in the video processing device illustrated in FIG. 1;
FIG. 6 is a diagram for explaining another example of zone division and an example of magnification conversion processing according to the first embodiment.
FIG. 7 is a diagram illustrating an example of zone division and an example of a magnification conversion process according to the second embodiment.
FIG. 8 is a diagram for explaining an example of a magnification conversion process for the example of zone division shown in FIG. 7;
FIG. 9 is a diagram illustrating an example of input / output characteristics of a display.
FIG. 10 is a block diagram illustrating a schematic configuration of a video processing device according to another embodiment.
FIG. 11 is a block diagram illustrating a schematic configuration of a typical video processing device.
FIG. 12 is a diagram illustrating an example of a gamma correction output characteristic, an inverse gamma correction output characteristic, and a video signal output after inverse gamma correction.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Input terminal 2 ... A / D conversion part 3 ... Inverse gamma correction part 4 ... Bit change part 5 ... Zone discrimination part 6 ... Signal processing part 7 ... Magnification conversion part 8 ... Interface part 9 ... Display part 13 ... Input / output characteristics Correction unit 51 input terminal 52 conversion unit 53 pixel conversion unit 54 inverse gamma correction unit 55 PDP
56 ... signal processing unit 57 ... subfield conversion unit 58 ... drive unit

Claims (2)

A zone determination unit that determines whether the quantization size of the input video signal quantized by L bits applies to any one of the zones having a plurality of quantization size widths prepared in advance,
A bit changing unit that quantizes an input video signal of each zone divided by the zone discrimination unit with M bits so that an amplitude value per bit is smaller than an amplitude value quantized with L bits;
The input video signal of each zone quantized by the M bits by the bit changing unit, weighted according to the amplitude value of the input video signal of each zone, a magnification conversion unit to add the weight,
An image processing apparatus comprising: an interface unit that generates an image display signal to be displayed on a display device using the input image signal to which the weight is added by the magnification conversion unit. 2. The video processing device according to claim 1, further comprising an inverse gamma correction unit that performs inverse gamma correction on the input video signal quantized with the L bits and outputs the result to the zone determination unit.

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