KR100991421B1 - High-compression video encoding procedure, and signals processing equipment and method for DCC using the video encoding procedure - Google Patents

Abstract

It provides line-by-line high-speed image compression and dynamic capacitance compensation (DCC) control. A method of processing an image signal according to an embodiment of the present invention includes generating and storing encoded data by encoding an input image signal using lossy compression encoding, and reconstructing an image signal of a previous frame from the stored encoded data. Calculates a first pixel value difference for each pixel from the reconstructed previous video image signal and the current frame video signal, performs dynamic capacitance compensation on a pixel whose first pixel value difference is greater than or equal to a threshold, and And not performing the dynamic capacitance compensation for pixels whose pixel value difference is less than or equal to the threshold.

Description

High-compression video encoding procedure, and signals processing equipment and method for DCC using the video encoding procedure

The present invention relates to high compression video encoding and dynamic capacitance compensation (DCC) using the same, and more particularly, to a high compression video encoding process and a signal processing apparatus and method using the video encoding procedure for dynamic capacitance compensation. .

Recently, in accordance with the trend of large-sized televisions, flat panel display devices such as liquid crystal displays and plasma display panels (PDPs) instead of cathode ray tube displays (CRTs) have attracted attention. Among such flat panel display devices, weight reduction and thickness reduction are possible, and in recent years, liquid crystal display devices are particularly attracting attention as they become larger in size. In the liquid crystal display device, a liquid crystal material is injected between an upper substrate on which a color filter and the like are formed and a lower substrate on which a thin film transistor and the like are formed, and a predetermined potential is applied between the upper and lower substrates by applying different potentials to the upper and lower substrates. A display device expresses a desired image by changing an arrangement of molecules of a liquid crystal material by applying an electrical pressure (gradation voltage) and controlling an amount of light transmitted through the substrate. Liquid crystal displays operate at a low power source and consume less power, which is not only used as a display for a portable device, but also recently, a large-capacity panel can be manufactured.

One problem of the liquid crystal display is that the response speed of the liquid crystal does not match the frame rate. That is, since the liquid crystal has a slow response speed, blurring occurs due to the response of the previous image to the value of the current image or the response delay with respect to the applied gradation voltage. In order for a desired image to be represented in a liquid crystal display, a time delay is inevitable, and the image cannot be effectively displayed due to such time delay.

One method proposed to solve the problem of deterioration of image quality due to the delay of the response speed for the liquid crystal display is Dynamic Capacitance Compensation (DCC). Dynamic capacitance compensation is to minimize the problem caused by the response delay of the liquid crystal by applying a gray scale voltage greater than the original gray voltage to the pixel, the difference between the pixel value of the previous frame and the pixel value of the current frame for each pixel And a predetermined voltage proportional to the difference between the pixel values is applied to the current frame.

In order to perform such dynamic capacitance compensation, the pixel values of the previous frame must be stored in the memory. However, when the pixel values of the previous frame are stored in the memory without compression, a large memory is required, and thus a method of compressing image data may be considered to alleviate the burden on the large memory. According to this, since the pixel values of the previous frame are compressed using the encoder and the compressed bit string is stored in the memory, the burden on the large memory can be alleviated. However, no method has been proposed to compress image data with very high efficiency for dynamic capacitance compensation.

One problem to be solved by the present invention is to use this video encoding procedure together with a high compression video encoding procedure that can alleviate the burden of adding a large amount of memory by guaranteeing a compression rate of a certain level or more, and also provides a signal for dynamic capacitance compensation. It is to provide a processing apparatus and method.

Another challenge that the present invention seeks to solve is this improvement, along with an improved EG-MEG encoding procedure that shows a higher compression rate than the existing Exponential-Golomb (EG) encoding. It is to provide a signal processing apparatus and method for using the exponential-Golomb encoding procedure and also for dynamic capacitance compensation.

Another problem to be solved by the present invention is to solve the problem that the change of the previous frame is amplified by lossy compression of the previous frame even when the pixel value does not change or only a very small change occurs in the before and after frame. To provide an apparatus and method for processing an image signal for dynamic capacitance compensation that can control the application of the dynamic capacitance compensation so that.

According to an aspect of the present invention, there is provided a method of processing a video signal, the method comprising: generating and storing encoded data by encoding an input video signal using a lossy compression encoding method; Reconstructing a video signal of a previous frame from the stored encoded data; And calculating a first pixel value difference for each pixel from the reconstructed image signal of the previous frame and the image signal of the current frame, performing dynamic capacitance compensation on pixels whose difference is greater than or equal to a threshold. And not performing the dynamic capacitance compensation for pixels whose pixel value difference is less than or equal to the threshold.

According to an aspect of the embodiment, the threshold may be determined using the amount of error that may occur by the lossy compression encoding scheme. The lossy compression encoding scheme may include a quantization process, and the threshold may be a maximum error value that may occur during the quantization process.

According to another aspect of the embodiment, the lossy compression encoding method may include quantizing the input video signal by a first pixel unit having a predetermined size to generate a quantized pixel value for each pixel; Obtaining a second pixel value difference by difference between the quantized pixel value of the current pixel and the quantized pixel value of the left pixel of the current pixel; And calculating a frequency of the second pixel value differences in units of a second pixel having a predetermined size and adaptively assigning a code according to the frequency. In this case, the first pixel unit is a line unit, a group unit of dividing one line into a plurality of units, or a unit of a plurality of lines, and the second pixel unit is a group unit of a single line divided into a plurality of units. Can be. In the generating of the quantized pixel value, the quantization coefficient may be generated by adaptively applying the quantization step such that the compression ratio of the encoded data is equal to or greater than a predetermined level. In addition, in the code allocating step, an exponential-code having a short length is allocated to the plurality of frequently different second pixel value differences in inverse proportion to the magnitude of the frequency, and existing for the second pixel value difference of the remaining frequencies. Assign an exponential-Golomb code of.

According to another aspect of the embodiment, when the input video signal is RGB type, converting the input video signal to YUV type before the encoding step and RGB video signal of the previous frame reconstructed in the reconstruction step The method may further include converting to a type.

According to an aspect of the present invention, there is provided a method of encoding a video signal, the method comprising: obtaining a pixel value difference by dividing a pixel value of a current pixel from a pixel value of a left pixel of the current pixel in an input video signal; Calculating a frequency for the pixel value differences in units of pixels of a predetermined size; And assigning the exponential-Golomb code having a length inversely proportional to the frequency among the exponential-Golomb codes for each of the pixel value differences.

According to an aspect of the embodiment, in the allocating of the exponential-Golomb code, a short length code is assigned among the exponential-Golomb codes so as to be inversely proportional to the frequency with respect to the predetermined number of pixel values having a large frequency. The general exponential-Golomb code may be assigned to the pixel value difference of the frequency.

According to another aspect of the embodiment, further comprising the step of generating a quantized pixel value for each pixel by quantizing the input image signal by a pixel unit of a predetermined size before calculating the difference of the pixel value, The difference in pixel values can be obtained using the quantized pixel values. In this case, the pixel unit of the predetermined size may be a group unit in which one pixel line is divided by any one of 1 to 16 and grouped.

A signal processing method according to another embodiment of the present invention for solving the above problems is a signal processing method for a display device including a dynamic capacitance compensation device, the signal processing method of the pixel value of the current frame and the current frame By using the pixel value of the previous frame, the dynamic capacitance compensation device is adaptively turned on or off for each pixel of the current frame.

According to an aspect of the embodiment, the dynamic capacitance compensation device may be turned on only when the difference between the pixel value of the current frame and the pixel value of the previous frame is greater than or equal to a threshold. The pixel value of the previous frame is data reconstructed according to the lossy compression scheme, and the threshold may be the maximum error that may occur according to the lossy compression scheme. In this case, the lossy compression scheme may be a quantization process.

By using the video signal processing system according to the embodiment of the present invention, by replacing the DCC-related system of the existing liquid crystal display device (LCD television, LCD monitor, etc.), the burden on the memory capacity can be alleviated and the calculation amount is greatly increased. Can be reduced. Therefore, the signal processing apparatus or method according to the embodiment of the present invention is suitable when a large amount of data and a lot of memory are required, such as HDTV.

In addition, the DCC control scheme proposed in the embodiment of the present invention can be used in combination with all other image compression techniques in addition to MPEG-based compression to reduce the adverse effect of compression error on the final output image.

In addition, according to the embodiment of the present invention, since the dynamic capacitance compensation is applied only when the difference between the pixel value of the current frame and the previous frame is greater than or equal to the predetermined threshold value, the dynamic capacitance compensation is unnecessary in the pixel which is recognized as not changing the pixel value. Due to this application, it is possible to prevent the deterioration of the image quality due to the change in the pixel value.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Embodiments of the present invention described below may be applied to signal processing for a dynamic capacitance compensation device generally provided in a liquid crystal display device, but this is merely exemplary. For example, the modified Exponential-Golomb (MEG) encoder according to an embodiment of the present invention described below is an example of a high speed video encoding apparatus, and may be applied to other types of lossless video signal compression apparatuses.

In addition, the adaptive dynamic capacitance compensation (DCC) device according to an embodiment of the present invention described below includes a lossy compression storage process for data of a previous frame as well as a liquid crystal display, and an image having a capacitance compensation control device using the same. Any display device can be applied regardless of its type. For example, the adaptive DCC device or DCC control technique described below may be included and applied to any device if it is necessary to reduce the adverse effect of compression error on the final output image in combination with all other image compression techniques in addition to MPEG-based compression. Can be.

1 is a flowchart schematically illustrating an image signal processing procedure including a dynamic capacitance compensation (DCC) process according to an embodiment of the present invention.

Referring to FIG. 1, in an image signal processing procedure according to an embodiment of the present invention, first, an input image signal input in a predetermined unit is compressed by a modified Exponential Golomb (MEG) encoder to store compressed data (S11). . The input image signal may be input in line units of the image in the raster scan direction of the image, but is not limited thereto. For example, one line image may be divided into a plurality of pixel groups, or a plurality of lines may be input in a plurality of line units in which a plurality of lines are combined into one line group.

In operation S11, a high compression image encoding technique that guarantees a compression rate of a predetermined level or more may be used. As described above, in order to perform the DCC procedure without image compression, a high capacity memory capable of storing the entire pixel value of the previous frame is required. By using an image compression technique showing a high compression ratio as in the embodiment of the present invention, It can alleviate the burden of adding memory. However, high compression video encoding provides high compression efficiency, but inevitably results in data loss.

According to an embodiment of the present invention, a modified Exponential Golomb (MEG) encoding technique is used as a high compression image encoding technique. Since the general EG technique and the MEG technique applied to the embodiment of the present invention use the characteristic that the pixel values of the left and right pixels are similar due to the characteristics of the continuous images, the difference pixel value obtained by subtracting the value of the left pixel from the value of each pixel or There is a common point in that a pixel difference is obtained and encoded by a method of allocating a predetermined code to each pixel difference. However, the MEG technique differs from the general EG technique in terms of a specific method of allocating codes. The MEG technique is a code fixed to a value to be encoded (for example, a difference between a quantized pixel value of a previous frame and a current frame). It is possible to improve the compression efficiency more than the conventional EG in that the code is adaptively allocated based on the statistical result (for example, the frequency value of the pixel difference) on the value. More details on this will be described later.

In the image encoding technique according to the embodiment of the present invention, an adaptive quantization technique is used to ensure a constant compression ratio that is higher than or equal to a predetermined level. The adaptive quantization technique refers to adaptively determining the quantization step size to be used in the quantization step in consideration of the compression ratio. According to the embodiment of the present invention, since the compression ratio is limited due to the characteristics of the MEG technique which is lossless compression, the high compression ratio is ensured by introducing the adaptive quantization technique. Although applying a quantization technique in the encoding process inevitably causes data loss, in the embodiment of the present invention, the compression efficiency is improved while taking a certain amount of data loss to alleviate the burden on a high capacity memory. The adjustment of the quantization step may be performed on a line basis, but is not limited thereto, and may be performed on a sub-line basis divided into several lines.

2 is a block diagram illustrating an example of a configuration of an encoding apparatus 100 for performing a high compression video encoding technique that may be applied to step S11 according to an embodiment of the present invention. Referring to FIG. 2, the encoding apparatus 100 includes a quantizer 110, a differentiator 120, and a MEG encoder 130.

The quantizer 110 is a means for quantizing the input image signal of a predetermined unit. A quantization step (K) of predetermined magnitude is used for quantization, the value of which may be fixed or variable. According to the exemplary embodiment of the present invention, the quantizer 110 may adaptively control the size of the quantization step so as to guarantee a compression rate of a predetermined level or more. In FIG. 2, this process is indicated by the control of the quantization step K using the output of the MEG encoder, and the control of the quantization step can be, for example, in line units.

For example, in the quantizer 110, after encoding by using a small value quantization step, if the compression rate does not reach the expected value, the encoding process is performed again by increasing the size of the quantization step. To ensure a certain level of compression. 3 is a diagram illustrating an example of a compression rate control process through the control of the quantization step. Referring to FIG. 3, first, a predetermined size per pixel, for example, 9 bits is encoded, and when the compression rate is lower than the reference value, the LSB (Least Significant Bit) is removed and then compressed again to calculate the compression rate. . The removal of the LSB and the calculation of the compression rate are repeated until a predetermined reference compression rate is achieved.

Since the MEG compression method is a lossless compression method, the compression rate varies depending on the image. Accordingly, the quantizer 110 is a means for adjusting the compression ratio in the encoding apparatus 100 according to the embodiment of the present invention. In this case, the quantized value may use division as in the conventional method, but may use a bit shift operation to remove the LSB as shown in FIG. 3. In the latter case, the bit shift operation has an advantage that the division operation can be performed quickly, and for this purpose, the quantized value may be limited to an exponent of two.

The quantizer 110 compresses the quantized line with the MEG encoder 130 and then outputs and stores the result when the compression is achieved within the target compression ratio. On the other hand, if the compression rate is not achieved within the target, as described above, the same process is repeated until the target compression rate is achieved after increasing the quantization step (K). In this case, the quantization step K can be doubled, but the embodiment of the present invention is not limited thereto. When the target compression rate is achieved, the value of the corresponding quantization step is stored separately and used as a reference value for subsequent decoding procedures and DCC control.

As in the conventional EG encoding method, the encoding method used by the MEG encoder 130 described later has a higher compression ratio as the input value is distributed intensively near zero. In general, the pixel difference between left and right pixels is symmetrically distributed around 0. This characteristic is also used because the MEG encoding method is a variation of the EG encoding method. As the quantizer 110 increases, the pixel differences are more concentrated around zero, and the compression ratio increases.

Subsequently, referring to FIG. 2, the difference unit 120 calculates a difference between the quantization result of the current pixel and the quantization result of a pixel adjacent to the current frame to the left (hereinafter referred to as a 'left pixel'). Output the difference or difference. To this end, the difference unit 120 uses a predetermined delay means for inputting the value of the left pixel calculated before the current pixel, and a value of the current pixel input through the quantizer 110 and the delay means. It may include an adder (Adder, +) for subtracting the value of the input left pixel. However, the configuration of the difference unit 120 is an example, the difference unit 120 may be implemented in another configuration to perform the same function.

The MEG encoder 130 is a unit for allocating a predetermined code according to the difference between the current pixel and the left pixel obtained by the difference unit 120, similarly to the EG technique, which is a lossless compression method. However, in the conventional EG method, the shorter code is allocated as the difference approaches 0 in the entire range, whereas the MEG encoder 130 according to the embodiment of the present invention obtains a frequency distribution for the difference of pixel values. The most frequent constant range (e.g., 3 to 8) of the most frequent values in the frequency distribution is searched, and these modes are specifically assigned to the most compressed code in the existing EG code in consideration of the frequency. This will be described in more detail below.

In the general image, since the pixel values in the image have a high spatial correlation, the left and right pixel values adjacent to each other have the same or similar characteristics. One of the encoding methods using the characteristics of the image is the EG encoding method. In the EG encoding method, which is a lossless compression method, the pixel difference obtained by subtracting the left pixel value from each pixel value is obtained. Assign.

Referring to Table 1, it can be seen that the smaller the pixel difference between the left and right pixels, the shorter the allocated code length. This EG encoding method has a high compression ratio when encoding a video having high spatial correlation such as a natural video. Shows. In other words, when the spatial correlation of the image is high and the distribution of pixel difference values shows a generalized Gaussian (GG) distribution, the conventional EG encoding method using the code of Table 1 not only shows a high compression rate but also a high speed. Coding is possible.

However, the conventional EG encoding method for allocating codes as shown in Table 1 does not show a high compression ratio in the case of an image having low spatial correlation, for example, because a large amount of text is included in the image as shown in FIG. 4A. can not do it. This is because, in the case of the image of FIG. 4A, when the frequency distribution is obtained by determining the pixel difference between the left and right pixels, the distribution does not show the GG distribution.

FIG. 4B is a graph showing a frequency distribution of pixel differences for the image of FIG. 4A. Referring to FIG. 4B, unlike the GG distribution, it can be seen that a small peak occurs at a predetermined pixel difference (see a portion indicated by circles in FIG. 4B). When the conventional EG code shown in Table 1 is applied to such a distribution of pixel differences, the high peak compression is difficult due to low compression efficiency due to the small peak portion described above.

Therefore, the MEG encoding scheme according to the embodiment of the present invention, that is, the MEG encoder 130 first obtains a frequency distribution of pixel differences and finds a predetermined number of modes having a high frequency distribution. The most frequent code of the most frequently distributed EG code is allocated to the most frequent frequency distribution, and the other code is allocated in the same manner as the existing EG code.

This frequency distribution can be obtained in pixel units of a predetermined size. For example, the frequency distribution can be found in lines, but it is desirable to find them in smaller units if possible. This is because an image may have different frequency distributions, even if the same line is different depending on its type, depending on its position. For example, the frequency distribution may divide one line into a plurality of groups and obtain a frequency distribution in units of groups. The coding efficiency of dividing one line into several groups should be taken into consideration as a whole, and may be divided into any one of 1 to 16, for example, eight groups.

The number of modes having a high frequency distribution is not particularly limited, but can be adaptively determined in consideration of the improvement of the compression efficiency. For example, the number of modes adapts to any one of three to eight values, such as six fixed values, or to a value within a certain range (eg, 3-8) depending on the nature of the frequency distribution. It can also be a variable value that selects a value. For example, in the case of searching for six modes, a method of allocating the six modes with the shortest six codes having the highest compression ratio in the existing EG code may be used.

As described above, the reason why the MEG encoder 130 which finds high frequency pixels and adaptively assigns codes according to the frequency is used in the embodiment of the present invention. In this case, the image forms a predetermined pattern, so that pixels having a large left and right pixel difference often appear continuously, and in this case, the frequency of a specific pixel difference value tends to be high (Fig. 4A and Fig. 4A). Video with text).

However, according to an aspect of an embodiment of the present invention, all pixel differences are not aligned according to their frequency, but only for the mode of the pixel difference within a predetermined range. This is because the sorting of all pixel differences based on the frequency and the code allocation according to the frequency are too large for the real-time processing. Therefore, in the case of a device without burden of computation, a method of allocating a shorter length code according to the frequency order and sorting by frequency according to every pixel difference may be applied.

According to another aspect of the embodiment of the present invention, unlike the conventional EG code (see Table 1) which targets only integers greater than or equal to zero (see Table 1), the pixel difference is 0, 1, -1, 2, -2,. Likewise, the codes may be assigned in the order considering the negative numbers. This is because the left and right pixel difference of the image becomes a symmetrical form with the positive and negative values centered around zero.

5 is a block diagram showing the configuration of the MEG encoder 130 and the encoding process using the same according to an embodiment of the present invention. Referring to FIG. 5, the MEG encoder 130 includes a frequency histogram generator 131, a mode search unit Sorter 132, and a code assignment unit First Encoder and Second Encoder 133.

The frequency histogram creation unit 131 creates a frequency histogram from the pixel difference values (difference of the quantized pixel values) of the inputted left and right pixels. The frequency histogram may be created in units in which encoding is performed in the encoding apparatus 100, for example, in pixel lines, but embodiments of the present invention are not limited thereto. For example, the frequency histogram may be created in units of a plurality of pixel lines or in units of one whole frame. And the mode search unit 132 uses the created frequency histogram to show a pixel number that shows the mode value of a predetermined number, for example, one of three to eight (for example, six except when the pixel difference becomes zero). Find the values.

The code assignment unit 133 assigns a code in a manner different from that of the existing EG encoding scheme. That is, for the pixel differences showing the predetermined number of modes (6 except when the pixel difference becomes 0) found in the mode search unit 132, the first encoder 133a is different from the conventional EG code. Assign code For example, as shown in Table 2, the first encoder 133a allocates the shortest length EG code to the frequency difference having the mode value in inverse proportion to its frequency. On the other hand, for pixel differences showing other frequencies (i.e., less frequent), the second encoder 133b allocates the same code as the existing EG code, as shown in Table 3.

1, the image signal processing apparatus according to an embodiment of the present invention restores pixel values of a previous frame from stored MEG code data (S12). The reason for restoring the pixel value of the previous frame is to perform the DCC procedure. This is because, in the DCC procedure, a predetermined gray scale voltage is applied which is proportional to the difference between the pixel value of the current frame and the pixel value of the previous frame, so that the pixel value of the previous frame must be input to apply the DCC.

The method of restoring the pixel value of the previous frame from the stored MEG code data uses a process opposite to that of the MEG encoding method, that is, the MEG decoding method. 6 is a block diagram illustrating a configuration of a decoding apparatus 200 that may be used for a MEG decoding procedure according to an embodiment of the present invention. Referring to FIG. 6, the decoding apparatus 200 includes a MEG decoder 210, an accumulator 220, and an inverse-quantizer 230.

In the MEG decoder 210, the process proceeds in the opposite manner to the MEG encoder (reference numeral 110 of FIG. 2) by inputting a code value for a previous frame stored in the memory. The code values may be input in a predetermined size unit, for example, in a line unit. The MEG decoder 210 restores the pixel value difference between the left and right pixels from the MEG code for the previous frame. Therefore, in the MEG decoder 210, the same MEG code assignment table as used in the MEG encoder (see Tables 2 and 3) is used.

The accumulator 220 accumulates these pixel difference values output from the MEG decoder 210 and outputs quantization coefficients for each pixel of the previous frame. To this end, as shown in FIG. 6, the accumulator 220 adds an adder unit (Adder, +) for summing the output from the delay unit and the output from the MEG decoder 210 and the output from the delay unit. It can be configured to include. However, the configuration of the accumulator 220 is an example, and another configuration may be employed to perform the same function.

The inverse-quantizer 230 inversely quantizes the output value of the accumulator 220. In the inverse quantization process, since the quantization step having the same size as the quantization step used in the quantization process is used, the magnitude K of the quantization step generated in the encoding apparatus 100 is used in the decoding apparatus 200.

Subsequently, referring to FIG. 1, it is determined whether dynamic capacitance compensation (DCC) is to be applied using pixel values of the current frame and the previous frame (S13). The DCC is adaptively performed in subsequent steps S14 and S15 according to the determination result in the upper limit S13. As described above, the reason for adaptively performing DCC in the embodiment of the present invention is that since the pixel value of the previous frame is a value obtained from a lossy compressed image, a difference with the actual pixel value of the previous frame occurs. to be.

In the DCC procedure, a gray voltage higher than the gray voltage applied in the previous frame is applied to the current frame in proportion to the difference between pixel values of the current frame and the previous frame. That is, when the difference between the pixel values is large, the additionally applied gradation voltage is proportionally higher, but when the difference between the pixel values is small, the additionally applied gradation voltage is relatively small.

In the embodiment of the present invention, DCC is adaptively applied in consideration of the characteristics of such a DCC procedure and also an error due to lossy compression storage of data of a previous frame. For example, if the difference between the pixel value of the inputted current frame and the previous frame restored from the compressed data is large, even if some data loss occurs during the restoration after compression, the loss value occupies the pixel value difference. The ratio is not very high. That is, as the DCC is applied, the ratio of the magnitude of the applied gradation voltage generated by the compression error is not very high in the magnitude of the applied gradation voltage. Therefore, in this case, DCC is applied as in the prior art.

On the contrary, when the pixel value is small, a slight error due to compression may also have a large effect. That is, as the DCC is applied, the ratio of the magnitude of the applied gradation voltage generated by the compression error to the change in the magnitude of the applied gradation voltage originally generated is considerably high. Therefore, in this case, since there is a high possibility that an unexpected error occurs due to the application of the DCC, in this case, the DCC is not applied unlike the conventional case.

In the case of DCC with a compressed image, the DCC value is also slightly changed due to an error due to compression. In this case, when the difference between the pixel value of the previous frame and the current frame is large, since the change of the value due to the DCC is original, it is almost impossible to recognize even if a slight error occurs due to compression. However, if the value of the previous frame and the current frame is the same or the same, the difference is amplified due to the compression error, so that DCC is highly likely to be applied. In such a case, since the value of a pixel that is essentially almost unchanged or has to maintain a constant value may change relatively, such a change may be perceived and may cause deterioration of image quality.

Therefore, this problem can be solved by applying the DCC only when the difference between the pixel value of the previous frame and the current frame is greater than or equal to a predetermined threshold, and not applying the DCC when less than the threshold. The threshold may be determined in terms of the size of the quantization step that is experimentally determined or that causes lossy compression. For example, the threshold may be determined using the maximum error generated due to the compression in the quantization step. More specifically, DCC is not applied when the difference in pixel values between the frames is smaller than the maximum error that may occur due to compression. On the contrary, when the difference in pixel values is larger than the maximum error that may occur due to compression, DCC is not applied. Can be applied.

The small difference in pixel values between the current frame and the previous frame is pixels that have little effect of DCC. Therefore, as in the embodiment of the present invention, the DCC is applied only when the difference of pixel values is large, and the DCC is not applied when the pixel value is small.

7 is a block diagram showing the configuration of an adaptive DCC device 300 according to an embodiment of the present invention. The adaptive DCC device 300 of FIG. 7 may be a device that can be applied in steps S13 to S15 in the flowchart shown in FIG. 1, but is not limited thereto. That is, the adaptive DCC device 300 having the configuration as shown in FIG. 7 is a procedure in a device that performs DCC and also uses compressed and stored data for the DCC, regardless of the type of the device. It may be used to control the DCC performed in the.

Referring to FIG. 7, the adaptive DCC device 300 according to the embodiment of the present invention includes a DCC unit 310 and a DCC control unit 320 for controlling the operation of the DCC unit. The DCC unit 310 performs the same function as the existing DCC device, and a gray scale voltage proportional to the difference is added using the pixel value Xc of the current frame and the pixel value Xp of the previous frame. The pixel value after the generated DCC is outputted. However, according to the exemplary embodiment of the present invention, the DCC unit 310 is different from the existing DCC unit in that the operation thereof is controlled by the DCC control unit 320.

In addition, the DCC control unit 320 may or may not operate the DCC unit 310 in consideration of the difference between the pixel values using the pixel value Xc of the current frame and the pixel value Xp of the previous frame. It performs the function of controlling to prevent. For example, the DCC control unit 320 may perform a switching function for controlling the DCC unit 310 to operate or not to operate. Therefore, the configuration diagram shown in FIG. 7 is exemplary and may be configured in another manner to perform a function of switching using the pixel value Xc of the current frame and the pixel value Xp of the previous frame. For example, the DCC control unit 320 is arranged in the form of a switch that selects from the form that the input signal is input to the DCC unit 310 or bypasses it by placing an additional line bypassing it before the DCC unit 310. May be

As described above, according to the embodiment of the present invention, the compression rate is adaptively controlled compared to the conventional EG encoding method by adaptively controlling the size of the quantization step so as to guarantee a compression rate of a predetermined level or more, and applying the MEG encoding method. Further improve. Therefore, according to the embodiment of the present invention, even when DCC is applied when displaying an image, the pixel data of the previous frame is compressed and stored, thereby further alleviating the burden of adding a high memory capacity.

In addition, according to the embodiment of the present invention, since DCC is adaptively applied in consideration of the loss that may occur due to compression, it is possible to further enhance the effect of blurring due to DCC. In addition, DCC is applied only when the difference between the pixel of the previous frame and the current frame is the maximum error due to compression or more, so that a human will not visually change, such as a pixel having no change in pixel value or a pixel having a slight change in pixel. Since DCC is applied to the expected pixel, it is possible to prevent the image quality from being easily recognized. In addition, in the embodiment of the present invention, since the DCC is not applied only when the DCC does not significantly affect the image quality, the disadvantage of the non-application of DCC can be minimized.

Next, the overall configuration of the image signal processing apparatus according to the embodiment of the present invention including all the above-described processes will be described.

8 is a block diagram showing the overall configuration of a dynamic capacitance compensation signal processing apparatus using high compression video encoding according to an embodiment of the present invention. Referring to FIG. 8, the signal processing apparatus 400 includes an encoding apparatus 410, a memory 420, a decoding apparatus 430, and an adaptive DCC apparatus 440. Encoding device 410 including a quantizer (Q), a differential, a MEG encoder (MEG Encoder), a MEG decoder (MEG Decoder), an accumulator (Accumulator), and a dequantizer (Q-1) Since the configuration and operation of the decoding device 430 and the adaptive DCC device 440 including the DCC unit DCC and the DCC controller have been described in detail above, the description thereof will be omitted. .

In addition, the signal processing apparatus 400 according to an exemplary embodiment of the present invention may include a second video signal converter (A) at an input terminal of the encoding device (410) and / or an input terminal of the adaptive DCC device (440). 435 may be further included. In FIG. 7, a YUV converter 405 is shown as the first video signal converter 405, and an RGB converter 435 is shown as the second video signal converter 435. This embodiment is not limited only to this. That is, the first and second video signal converters 405 and 435 are devices for mutually converting YUV and RGB signals, and include an encoding device 410, a memory 420, a decoding device 430, and an adaptive DCC. A device for converting a video signal to be compatible with a format of a video signal used in the device 440.

Accordingly, in some embodiments, the first video signal converter 405 may be an RGB converter, and the second video signal converter 435 may be a YUV converter. In addition, the signal input to the first and second video signal converters 405 and 435 is an adaptive DCC in the case of the encoding device 410 or the RGB converter 435 in the case of a subsequent device such as the YUV converter 405. If the format of the video signal to be used in the device 440 is the same, at least one or both of the video signal converters 405 and 435 may be unnecessary.

In FIG. 8, when an input signal is an RGB type, the YUV converter converts an RGB signal into a YUV type. In general, since encoding efficiency of YUV type data is higher than encoding RGB type data, the YUV converter 405 contributes to the improvement of the compression efficiency. If the input signal is of the YUV type or is deemed unnecessary, the YUV converter 405 may not be present. The RGB converter 435 in FIG. 8 is also an optional component for the same reason.

The embodiments of the present invention described in detail above are merely illustrative of the technical idea of the present invention, and should not be construed as limiting the technical idea of the present invention by the embodiments. The protection scope of the present invention is specified by the claims of the present invention described later.

1 is a flowchart schematically illustrating an image signal processing procedure including a dynamic capacitance compensation (DCC) process according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a configuration of an encoding apparatus for performing a high compression video encoding technique that may be applied to step S11 of FIG. 1.

3 is a diagram for describing a compression rate control process through control of a quantization step.

4A illustrates an example of an image having low spatial correlation including text.

FIG. 4B is a graph showing the frequency characteristics of the image of FIG. 4A.

5 is a block diagram showing a configuration of an MEG encoder and an encoding process using the same according to an embodiment of the present invention.

6 is a block diagram illustrating a configuration of a decoding apparatus that may be used in a MEG decoding procedure according to an embodiment of the present invention.

7 is a block diagram showing the configuration of an adaptive DCC device according to an embodiment of the present invention.

8 is a block diagram showing the overall configuration of a dynamic capacitance compensation signal processing apparatus using high compression video encoding according to an embodiment of the present invention.

Claims (22)

Encoding the input video signal using a lossy compression encoding method to generate and store encoded data; Reconstructing a video signal of a previous frame from the stored encoded data; And The first pixel value difference is calculated for each pixel in the reconstructed previous image image signal and the current frame image signal, dynamic capacitance compensation is performed on a pixel having the first pixel value difference greater than or equal to a threshold value, and the first pixel. Not performing the dynamic capacitance compensation for pixels whose value difference is less than or equal to the threshold value; The threshold value is determined using the magnitude of the error that can occur by the lossy compression encoding method. delete The method of claim 1, wherein the lossy compression encoding scheme comprises a quantization process, And the threshold is a maximum error value that can occur during the quantization process. The method of claim 1, wherein the lossy compression encoding scheme is Generating a quantized pixel value for each pixel by quantizing the input image signal by a first pixel unit having a predetermined size; Obtaining a second pixel value difference by difference between the quantized pixel value of the current pixel and the quantized pixel value of the left pixel of the current pixel; And And calculating a frequency with respect to the second pixel value differences in units of a second pixel having a predetermined size, and adaptively assigning a code according to the frequency. The method of claim 4, wherein the first pixel unit is a line unit, a first group unit that divides one line into a plurality, or a plurality of line units, and the second pixel unit divides one line into one or a plurality. And a second group unit. The image signal processing of claim 4, wherein the generating of the quantized pixel value comprises generating a quantization coefficient by adaptively applying a quantization step such that a compression ratio of the encoded data is equal to or greater than a predetermined level. Way. 5. The method of claim 4, wherein in the code assigning step, an exponential-code having a short length is allocated to the second plurality of frequently different pixel values in inverse proportion to the magnitude of the frequency, and the second pixels having the remaining frequency are generated. A method of processing an image signal according to claim 1, wherein an existing Exponential-Golomb code is assigned to the difference in value. The method of claim 1, wherein when the input video signal is RGB type Converting the input video signal into a YUV type before the encoding step; And converting the video signal of the previous frame reconstructed in the reconstruction step into an RGB type. Obtaining a pixel value difference by dividing a pixel value of a current pixel from a pixel value of a left pixel of the current pixel in an input image signal; Calculating a frequency for the pixel value differences in units of pixels of a predetermined size; And And assigning the exponential-Golomb code having a length inversely proportional to the frequency among the exponential-Golomb codes for each of the pixel value differences. The method of claim 9, wherein the step of assigning the exponential-Golomb code For a predetermined number of pixel values with a large frequency difference, a shorter code is allocated among the Exponential-Golomb codes to be inversely proportional to the frequency, and a general Exponential-Golomb code is allocated for the remaining frequency pixel values. A video signal encoding method. 10. The method of claim 9, prior to calculating the difference of pixel values. Generating a quantized pixel value for each pixel by quantizing the input image signal by a pixel unit of a predetermined size; And the difference between the pixel values is obtained by using the quantized pixel values. The method of claim 11, wherein the pixel unit of the predetermined size is a group unit of dividing one pixel line into any one of 1 to 16 and grouping the pixel lines. In the signal processing method for a display device comprising a dynamic capacitance compensation device, Adaptively turning on or off the dynamic capacitance compensation device for each pixel of the current frame by using a pixel value of a current frame and a pixel value of a previous frame of the current frame, And turning on the dynamic capacitance compensation device only when the difference between the pixel value of the current frame and the pixel value of the previous frame is greater than or equal to a threshold. delete The method of claim 13, wherein the pixel value of the previous frame is data reconstructed data encoded according to a lossy compression scheme, The threshold value is a signal processing method, characterized in that the maximum error that can occur according to the lossy compression scheme. The method according to claim 15, wherein the lossy compression scheme is a quantization process. An encoding device for encoding the input video signal of the current frame by lossy compression encoding to generate encoded data, and storing the generated encoded data in a memory; A decoding device for reconstructing an image signal of a previous frame of the current frame from the encoded data stored in the memory; And Compute a first pixel value difference for each pixel from the video signal of the previous frame and the video signal of the current frame output from the decoding device, and compensate for dynamic capacitance based on whether the first pixel value difference is greater than or equal to a threshold. An adaptive dynamic capacitance compensation device for performing or not performing The threshold value is determined using the magnitude of the error that can occur by the lossy compression encoding scheme. 18. The apparatus of claim 17, wherein the adaptive dynamic capacitance compensation device performs the dynamic capacitance compensation for pixels whose difference in value between the first pixel value is greater than or equal to a maximum error that can be caused by the lossy compression encoding scheme in the encoding device. And the dynamic capacitance compensation is not performed on a pixel whose first pixel value difference is less than or equal to the maximum error. 18. The apparatus of claim 17, wherein the encoding device is Generating a quantized pixel value for each pixel by quantizing the input image signal by a first pixel unit having a predetermined size; Obtaining a second pixel value difference by difference between the quantized pixel value of the current pixel and the quantized pixel value of the left pixel of the current pixel; And Calculating a frequency for the second pixel value differences in units of a second pixel having a predetermined size and adaptively assigning a code according to the frequency. Processing unit. 18. The method of claim 17, wherein when the input video signal is RGB type A YUV converter for converting the input video signal input to the encoding apparatus into a YUV type; And And an RGB converter for converting an image signal of a reconstructed previous frame outputted from the decoding apparatus into an RGB type. A difference unit for obtaining a pixel value difference by differentiating a pixel value of a current pixel from a pixel value of a left pixel of the current pixel in an input image signal; A frequency histogram generating unit for calculating a frequency for the pixel value differences output from the difference unit in units of pixels of a predetermined size; And And a code assignment unit for allocating said exponential-Golomb code having a length inversely proportional to said frequency among said pixel value differences for each of said pixel value differences. In the signal processing device for a display device including a dynamic capacitance compensation device, The signal processing apparatus adaptively turns on or off the dynamic capacitance compensation device for each pixel of the current frame by using the pixel value of the current frame and the pixel value of the previous frame of the current frame. ), And the dynamic capacitance compensation device is turned on only when a difference between the pixel value of the current frame and the pixel value of the previous frame is equal to or greater than a threshold.

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