KR101557374B1 - Intra Prediction Method and Apparatus and Image Encoding/Decoding Method and Apparatus Using Same - Google Patents

Abstract

The present invention relates to an intra prediction method and apparatus, and a method and apparatus for image coding / decoding using the same.
The present invention relates to an intra prediction apparatus for predicting a pixel value of each pixel of a current block by weighting a pixel value of one or more adjacent pixels included in a neighboring block in accordance with a distance between each pixel of the current block and one or more adjacent pixels, And an intraprediction unit.
According to the present invention, the current block to be encoded can be more accurately predicted, thereby reducing the difference between the actual block and the predicted block, thereby improving the coding efficiency and improving the compression efficiency.

Description

[0001] The present invention relates to an intra prediction method and apparatus, and an image encoding / decoding method and apparatus using the intra prediction method and apparatus.

The present invention relates to an intra prediction method and apparatus, and a method and apparatus for image coding / decoding using the same. More particularly, the present invention relates to an intra prediction method and apparatus for predicting, coding, and decoding a current block of an image from neighboring blocks, which minimizes a difference between an actual current block and a predicted current block, and an image encoding / And apparatus.

Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) have developed superior video compression techniques superior to the existing MPEG-4 Part 2 and H.263 standards. This new standard is called H.264 / AVC (Advanced Video Coding) and is jointly announced as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264. In this H.264 / AVC (abbreviated as 'H.264'), a spatial prediction coding method which is different from the international standard related to the conventional video coding such as MPEG-1, MPEG-2 and MPEG- Predictive Coding) method.

In the conventional moving image encoding method, "intra prediction" is used for the coefficient value transformed in the discrete cosine transform domain (DCT domain), thereby seeking to increase the coding efficiency. As a result, Resulting in deterioration in the subjective image quality of the transmission bit rate band. However, H.264 adopts a coding method based on Spatial Intra Prediction in a Spatial Domain instead of a Transform Domain.

An encoder using a coding method based on the existing spatial intraprediction predicts block information to be currently encoded from the information of a previous block that has been already encoded and reproduced and calculates a difference ) Information and transmits it to a decoder. At this time, parameters necessary for predicting the block information may be transmitted to the decoder, or the encoder and the decoder may be synchronized to share parameters required for prediction, so that the decoder may predict the block information. The decoder predicts the information of the neighboring block that has already been decoded and reproduced, obtains the sum of the error information transmitted from the encoder and the information of the predicted neighboring block, and generates and reproduces information of a desired current block to be decoded. In this case, if parameters necessary for prediction are also transmitted from the encoder, the decoder uses the parameter to predict information of neighboring blocks.

Intra prediction includes intra 4x4 prediction, intra 16x16 prediction, and intra 8x8 prediction, and each intra prediction includes a plurality of prediction modes.

1 is an exemplary diagram showing nine conventional 4x4 intra prediction modes.

1, intra 4x4 prediction includes a vertical mode, a horizontal mode, a DC (direct current) mode, a diagonal down-left mode, a diagonal down-right mode, There are nine prediction modes including a vertical-right mode, a horizontal-down mode, a vertical-left and a horizontal-up mode.

FIG. 2 is an exemplary diagram showing a conventional four 16 × 16 intra prediction modes.

Referring to FIG. 2, intra-16 × 16 prediction has four prediction modes including a vertical mode, a horizontal mode, a DC mode, and a plane mode. Intra 8x8 prediction There are four prediction modes similar to intra 16x16 prediction.

In the intra prediction using the DC mode as the prediction mode (hereinafter referred to as " DC mode prediction "), prediction is made with an average value in block units. Here, the average value is the average value of four pixels (intra 4x4 prediction) or 16 pixels (intra 16x16 prediction) and four pixels (intra 4x4 prediction) of the left block of the current block to be coded Refers to an average value of a total of 8 pixels (for intra 4x4 prediction) or 32 pixels (for intra 16x16 prediction) for 16 pixels (for intra 16x16 prediction). Therefore, when intraprediction is performed using the DC mode as a prediction mode, an average value of neighboring blocks of the current block is sought to predict both 4x4 pixels or 16x16 pixels of the current block to be coded.

Therefore, regardless of the types of intra 4x4 prediction and intra 16x16 prediction, a predictive value (Prediction Value or Predictor) for DC mode prediction is 16 pixels (in case of intra 4x4 prediction) or 256 pixels (In case of intra 16x16 prediction). This lowers the accuracy of the prediction of the current block, thereby causing a problem of lowering the coding efficiency or the compression efficiency.

Also, if the accuracy of the prediction deteriorates, the difference value between the actual block and the predicted block becomes large. However, the DC mode prediction as described above has a problem of increasing the error information and decreasing the coding efficiency.

In order to solve the above-described problems, the present invention has a main purpose of improving the compression efficiency of an image by reducing the difference between an actual block and a predicted block in performing intra prediction for predicting a current block of an image .

According to an aspect of the present invention, there is provided an intraprediction apparatus comprising: a weighted pixel value calculation unit for calculating a weighted pixel value by adding a weight to pixel values of one or more adjacent pixels included in a neighboring block; And a predictive pixel value calculation unit for calculating a predictive pixel value of each pixel of the current block using the weighted pixel values of one or more adjacent pixels.

According to another aspect of the present invention, there is provided an intraprediction method comprising the steps of: (a) calculating a weighted pixel value by adding a weight to pixel values of one or more adjacent pixels included in a neighboring block; And (b) calculating a predicted pixel value of each pixel of the current block using the weighted pixel values of one or more adjacent pixels.

According to still another aspect of the present invention, there is provided an apparatus for encoding an image, the apparatus comprising: prediction means for calculating a predicted pixel value of each pixel of a current block by adding a weight to pixel values of one or more adjacent pixels of a neighboring block, An intra predictor; A subtractor for generating a residual signal by calculating a difference value between an original pixel value of each pixel of the current block and a predicted pixel value of each pixel of the current block; A converter for converting the residual signal into a frequency domain; A quantization unit for quantizing the transformed residual signal; And a coding unit for coding the quantized residual signal into a bitstream.

According to still another aspect of the present invention, there is provided a method of encoding an image, comprising: (a) adding a weight to a pixel value of one or more adjacent pixels of a neighboring block to calculate a predicted pixel value of each pixel of the current block, Predicting a block; (b) generating a residual signal by calculating a difference value between an original pixel value of each pixel of the current block and a predicted pixel value of each pixel of the current block; (c) converting the residual signal into a frequency domain; (d) quantizing the transformed residual signal; And (e) encoding the quantized residual signal into a bitstream.

According to another aspect of the present invention, there is provided an apparatus for decoding an image, comprising: a decoding unit decoding a bitstream to extract a residual signal; A dequantizer for dequantizing the extracted residual signal; An inverse transform unit for inversely transforming the inversely quantized residual signal into a time domain; An intra predictor for predicting a current block by adding weight values to pixel values of one or more adjacent pixels of a neighboring block to calculate a predicted pixel value of each pixel of the current block; And an adder for calculating a sum of the inverse transformed residual signal and the predicted pixel value of each pixel of the current block and restoring the original pixel value of the current block.

According to another aspect of the present invention, there is provided a method of decoding an image, the method comprising: (a) decoding a bitstream to extract a residual signal; (b) dequantizing the extracted residual signal; (c) inversely transforming the dequantized residual signal into a time domain; (d) predicting a current block by adding a weight to pixel values of one or more adjacent pixels of a neighboring block to calculate a predicted pixel value of each pixel of the current block; And (e) reconstructing the original pixel value of the current block by calculating a value obtained by adding the inverse transformed residual signal to the predicted pixel value of each pixel of the current block.

According to still another aspect of the present invention, in an intraprediction apparatus, a pixel value of one or more adjacent pixels included in a neighboring block is weighted averaged according to a distance between each pixel of the current block and one or more adjacent pixels, And the pixel value of each pixel of the intra prediction unit is predicted.

As described above, according to the present invention, the current block to be encoded can be more accurately predicted, thereby reducing the difference between the actual block and the predicted block, thereby improving the coding efficiency and improving the compression efficiency.

1 is an exemplary diagram showing nine conventional 4x4 intra prediction modes,
2 is an exemplary diagram showing a conventional four 16 × 16 intra prediction modes,
3 is a block diagram schematically illustrating an electronic configuration of an image encoding apparatus according to an embodiment of the present invention.
4 is a block diagram schematically illustrating an electronic configuration of an intra prediction apparatus according to an embodiment of the present invention;
5 is a flowchart illustrating an intra prediction method according to an embodiment of the present invention.
6 is a flowchart illustrating a process of calculating a weighted pixel value of an adjacent pixel for each pixel of a current block according to an embodiment of the present invention.
FIG. 7 is a flowchart illustrating a method of encoding an image according to an embodiment of the present invention. FIG.
8 is a block diagram schematically illustrating an electronic configuration of an image decoding apparatus according to an embodiment of the present invention.
FIG. 9 is a flowchart illustrating a video decoding method according to an embodiment of the present invention. FIG.
10 is an exemplary diagram for explaining a process of predicting a current block using a weight according to distance according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

3 is a block diagram schematically illustrating an electronic configuration of an image encoding apparatus according to an embodiment of the present invention.

The image encoding apparatus 300 according to an exemplary embodiment of the present invention predicts a current block of an image using one or more neighboring blocks around the current block and encodes the image, A quantization unit 310, a subtraction unit 320, a transform unit 330, a quantization unit 340, and an encoding unit 350.

The image encoding apparatus 300 may be a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a portable multimedia player (PMP), a PlayStation Portable ), A mobile communication terminal, and the like, and may be a communication device such as a communication modem for performing communication with various devices or wired / wireless communication networks, a memory for storing various programs for encoding an image and data, a program And a microprocessor for calculating and controlling the microprocessor.

The intra predictor 310 predicts a current block in an image using a neighboring block of the current block, adds a weight value to one or more pixel values of one or more neighboring blocks, The current block is predicted by calculating a predicted pixel value of the pixel. Here, the neighboring block may be one or more neighboring blocks that are compressed before the current block and located in the periphery of the current block, as described above, and may be at least one of the left block of the current block and the upper block of the current block.

In addition, the intra prediction unit 310 may include a direct current (DC) mode, which is an intra prediction mode for predicting an average value of pixel values of one or more neighboring pixels of one or more neighboring blocks neighboring the current block to be encoded, Mode, it is possible to predict a current block only by performing weighting as described above when intra prediction is performed. In addition, the weight may be added differently depending on the distance between the position of each pixel of the current block and the position of each of one or more adjacent pixels of one or more neighboring blocks.

 That is, the intra predictor 310 averages the pixel values of the pixels adjacent to the current block among the pixels included in the neighboring blocks of the current block, and uses the DC mode, which is an intra prediction mode in which each pixel of the current block is predicted, The pixel value of the adjacent pixels is simply averaged and the average value thereof is not predicted as the pixel value of all the pixels of the current block but the weights are set differently according to the distance between each pixel of the current block and the adjacent pixels, The weighted pixel values of adjacent pixels are calculated and the weighted pixel values are averaged to predict the pixel values of all the pixels of the current block. Here, the "adjacent pixel" may be a pixel included in the neighboring block but adjacent to the current block, but may be a pixel included in the neighboring block but not adjacent to the current block. The intra prediction unit 310 will be described in detail with reference to FIG. 4 in the following description.

The subtraction unit 320 generates a residual signal by calculating the difference between the original pixel value of each pixel of the current block and the predicted pixel value of each pixel of the current block .

The transforming unit 330 transforms the residual signal generated by the subtracting unit 320 into a frequency domain. Here, the transforming unit 330 may use various transformation techniques for transforming image signals on a time axis, such as a discrete cosine transform (DCT) or a wavelet transform, to a frequency axis So that the residual signal can be converted into the frequency domain.

The quantization unit 340 quantizes the residual signal transformed into the frequency domain by the transform unit. The encoding unit 350 encodes the residual signal quantized by the quantization unit 340 into a bitstream. As such an encoding technique, entropy encoding technology may be used, but various other encoding techniques may be used without being limited thereto.

4 is a block diagram schematically showing an electronic configuration of an intra prediction apparatus according to an embodiment of the present invention.

The intraprediction apparatus 400 according to an embodiment of the present invention may be implemented as an intra predictor 310 in the image encoding apparatus described above with reference to FIG. Hereinafter, for the convenience of explanation, the intra prediction apparatus according to an embodiment of the present invention is abbreviated as an 'intra prediction unit 310'.

The intra prediction unit 310 according to an embodiment of the present invention predicts a current block of an image using one or more neighboring blocks around the current block, The pixel value of each pixel of the current block is predicted by weighted averaging the pixel value of the pixel according to the distance between each pixel of the current block and one or more adjacent pixels.

The intraprediction unit 310 may include a weighted pixel value calculation unit 410 and a predicted pixel value calculation unit 420. The intraprediction unit 310 may include weighted values of one or more pixel values of one or more neighboring blocks Weight value) to predict the current block by calculating the predicted pixel value of each pixel of the current block.

The weighted pixel value calculation unit 410 adds weight values to pixel values of one or more neighboring pixels included in one or more neighboring blocks adjacent to the current block to be encoded (in particular, adjacent to the current block) And calculates the weighted pixel value of the pixel.

Here, the weighted pixel value calculation unit 410 can calculate the distance between the position of each pixel of the current block and the position of each of the one or more adjacent pixels, and add the weight according to the distance. Thus, The weighted pixel value of the adjacent pixel can be calculated according to the weighted value. In addition, the weighted pixel value calculation unit 410 may add the weighted value to the pixel value of the adjacent pixel so as to be in inverse proportion to the calculated distance.

That is, if the current pixel of the current block is close to the adjacent pixel of the neighboring block, the weighted pixel value calculation unit 410 may add a large weight to the pixel value of the adjacent pixel , If the distance between the current pixel of the current block and the adjacent pixel of the neighboring block is large, the similarity between the current pixel and the neighboring pixel may be low, so that a small weight can be added to the pixel value of the adjacent pixel. In this manner, similarity between pixels in intra prediction (hereinafter referred to as " DC mode prediction ") utilizing a DC mode as a prediction mode by adding a weight in inverse proportion to the distance between the current pixel and the adjacent pixel to the pixel value of the adjacent pixel The difference between the current block and the prediction block can be further reduced.

The predictive pixel value calculation unit 420 calculates a predictive pixel value of each pixel of the current block using the weighted pixel values of one or more adjacent pixels calculated by the weighted pixel value calculation unit 410. [ Here, the predictive pixel value calculation unit 420 may calculate the predictive pixel value of each pixel of the current block by averaging the weighted pixel values of one or more adjacent pixels with respect to each pixel of the current block.

5 is a flowchart illustrating an intra prediction method according to an embodiment of the present invention.

When coding an image, the image coding apparatus 300 reduces the amount of coded data to increase the coding efficiency. The image coding apparatus 300 calculates a difference between an original pixel value of a current block to be coded and a prediction pixel of a current block predicted by a previously- (I.e., a residual signal).

For this purpose, as described above, the intra predictor 310 predicts the current block of the image using one or more neighboring blocks around the current block. For each pixel of the current block to be encoded, The pixel value is calculated (S510). That is, the intra predictor 310 calculates a weighted pixel value of one or more adjacent pixels by adding a weight to pixel values of one or more adjacent pixels included in one or more neighboring blocks (particularly, adjacent to the current block).

When the weighted pixel value of the adjacent pixel is calculated, the intra predictor 310 calculates the predicted pixel value of each pixel of the current block using the weighted pixel value of the adjacent pixel (S520). Here, the intra predictor 310 may calculate the predicted pixel value of each pixel of the current block by averaging the weighted pixel values of one or more adjacent pixels with respect to each pixel of the current block.

Meanwhile, when calculating the weighted pixel values of the adjacent pixels for each pixel of the current block in step S510, the intraprediction unit 310 may add weights according to distances between the positions of the pixels and the positions of the adjacent pixels have.

6 is a flowchart illustrating a process of calculating a weighted pixel value of an adjacent pixel for each pixel of a current block according to an exemplary embodiment of the present invention.

The intra predictor 310 selects one or more adjacent pixels adjacent to the current block among the pixels included in the neighboring block in the image if the current block is determined to be coded in the image (S610). Here, the selected neighboring pixel may be one or more of all the neighboring pixels of the left block of the current block, or one or more of all the neighboring pixels of the upper block of the current block, and all of the left block and the upper block But may be all pixels in a neighboring block (which may include a right block and a lower block) of the current block without being necessarily limited thereto.

In step S620, the intra predictor 310 selects one or more neighboring pixels and calculates a distance between each pixel of the current block and a corresponding one of the adjacent pixels. When the distance between each pixel of the current block and each of the one or more adjacent pixels is calculated as described above, the intra predictor 310 sets the weight according to the distance calculated in step S620, And calculates weighted pixel values of one or more adjacent pixels (S630).

That is, as in step S610, when the adjacent pixels of the neighboring block are selected, the intra-prediction unit 310 calculates a distance to each of the selected one or more adjacent pixels by selecting a specific pixel among all the pixels of the current block. The intraprediction unit 310 sets different weights according to the distances to the adjacent pixels for the specific pixels calculated as described above, and adds them to the pixel values of the adjacent pixels. When the distance is long, a small weight is added, A similarity between a specific pixel and an adjacent pixel is considered by adding a large weight. Thus, the weighted pixel value of the adjacent pixel is calculated by reflecting the weight value added differently depending on the distance. The intra predictor 310 performs an operation for calculating a weighted pixel value of an adjacent pixel with respect to a specific pixel of the current block as described above for all the pixels.

The intra predictor 310 calculates a weighted pixel value by adding different weights to the pixel values of the adjacent pixels according to the distance between the position of each pixel and the position of the adjacent pixel with respect to all the pixels of the current block, A predicted pixel value for a specific pixel is calculated by averaging the weighted pixel values of the adjacent pixels with respect to a specific pixel, and the process is performed on all pixels of the current block to calculate a predicted pixel value for all pixels of the current block .

7 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.

Referring to FIG. 3, the image encoding apparatus 300 according to an embodiment of the present invention may include an intra prediction unit 310, which is described above with reference to FIGS. 4 through 6, and an intra prediction unit 310, The current block is predicted using one or more neighboring blocks around the current block and the image is encoded.

That is, the image encoding apparatus 300 predicts a current block by adding a weight to one or more pixel values of adjacent pixels of one or more neighboring blocks to calculate a predicted pixel value of each pixel of the current block (S710) A residual signal is generated by calculating a difference value between the original pixel value of each pixel and the predicted pixel value of each pixel of the current block (S720), and the generated residual signal is converted into a frequency domain using DCT or wavelet transform (S730), quantizes the residual signal transformed into the frequency domain (S740), and encodes the quantized residual signal into a bitstream (S740).

As described above, the image encoded with the bit stream by the image encoding apparatus 300 can be transmitted in real time or in non-real time through a wired / wireless communication network such as the Internet, a local area wireless communication network, a wireless LAN network, a WiBro network, And transmitted to a video decoding device through a communication interface such as a serial bus (USB: Universal Serial Bus), decoded by the video decoding device, and restored and reproduced as an image.

FIG. 8 is a block diagram schematically illustrating an electronic configuration of an image decoding apparatus according to an embodiment of the present invention. Referring to FIG.

The image decoding apparatus 800 according to an embodiment of the present invention predicts a current block of an image using one or more neighboring blocks around the current block and decodes the image, An inverse quantization unit 820, an inverse transform unit 830, an adder 840, and an intra prediction unit 850.

The image decoding apparatus 800 may be implemented by a computer such as a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a portable multimedia player A portable communication terminal, a PMP (Portable Multimedia Player), a PlayStation Portable (PSP), a mobile communication terminal, and the like. The communication device such as a communication modem for performing communication with various devices or wired / wireless communication networks, A memory for storing various programs and data for performing the functions, a microprocessor for executing and controlling the programs, and the like.

The decoding unit 810 decodes the bit stream to extract a residual signal. That is, the decoding unit 810 decodes a bitstream, which is an image encoded by the image encoding apparatus 300, and extracts a residual signal including pixel information of a current block of the image.

The inverse quantization unit 820 dequantizes the residual signal extracted from the bit stream by the decoding unit 810. The inverse transform unit 830 inverse transforms the residual signal inversely quantized by the inverse quantization unit 820 into a time domain.

The adder 830 restores the original pixel value of the current block by adding the residual signal inversely transformed by the inverse transform unit 820 and the predicted pixel value of each pixel of the current block predicted by the intra predictor 850 .

The intraprediction unit 850 adds a weight to pixel values of one or more neighboring pixels of one or more neighboring blocks neighboring the current block among a plurality of blocks of the previously decoded and reconstructed image, To predict the current block.

Here, the weight may be added differently depending on the distance between the position of each pixel of the current block and the position of each of one or more adjacent pixels of one or more neighboring blocks. In addition, the intra-prediction unit 850 can calculate a predicted pixel value of each pixel of the current block by assigning weights only when DC mode prediction is performed, as described above.

In addition, the intraprediction unit 800 of the video decoding apparatus 800 according to an embodiment of the present invention may have the same or similar function as the intraprediction unit 310 of the video encoding apparatus 300 described above with reference to FIG. 3 The current block can be predicted using neighboring blocks. Therefore, a detailed description thereof will be omitted in order to avoid redundant description.

9 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

The video decoding apparatus 800 receives and stores a bitstream for an image through a wired / wireless communication network or a cable. The video decoding apparatus 800 decodes the current block of the current block to reproduce the video according to an algorithm of another program, Prediction is performed using one or more surrounding blocks in the vicinity, and the image is decoded and restored.

To this end, the image decoding apparatus 800 decodes the bit stream and extracts a residual signal indicating information on a pixel value of a current block of the image (S910). When the residual signal is extracted, the image decoding apparatus 800 dequantizes the extracted residual signal (S920), inversely transforms the inversely quantized residual signal into a time domain (S930), and outputs the inverse transformed residual signal to the time domain The current block is predicted by calculating a predictive pixel value of each pixel of the current block by adding a weight to one or more pixel values of one or more neighboring blocks around the current block (S940), and the residual of the current block inversely transformed in step S930 And the predicted pixel value of each pixel of the current block predicted in step S940 is added to restore the original pixel value of the current block (S950).

10 is an exemplary diagram for explaining a process of predicting a current block using a weight according to distance according to an embodiment of the present invention.

In intra-prediction, intra-prediction is performed using a plurality of intra-prediction modes. In the DC mode among the plurality of intra-prediction modes, pixels of neighboring blocks already coded (Which may be the pixels of the upper block), and predicts the current block through the prediction of the pixel values of all the pixels of the current block.

FIG. 10 shows pixels used in the intra 4x4 mode prediction of H.264, which is one of standards of video compression techniques. The sixteen pixels from the lower case letters a to p are the pixels of the current block to be encoded and the 13 pixels from the uppercase letters A to M are pixels of the previously compressed neighboring block (i.e., adjacent pixels).

10, intraprediction of the current block shown in FIG. 10 is performed using nine intra prediction modes for intra 4x4 mode prediction described above with reference to FIG. 1, and neighboring pixels A through M Prediction mode is determined from 9 intra-prediction modes using Rate-Distortion Optimization (RDO).

When predicting the pixel values of the pixels of the current block shown in FIG. 10 using the DC mode, which is the intra-prediction mode of 2 times shown in FIG. 1, in the case of the conventional prediction method, all 16 pixels ranging from a to p are the same Lt; / RTI > For example, the predicted pixel value of a pixel which is the pixel of the first column in the first row is calculated as shown in Equation (1), and not only the a pixel but also the remaining b pixel to p pixel are calculated as a pixel. That is, the pixels in the current block are predicted to have the same pixel values regardless of the positions of the pixels.

As described above, in the method of predicting the pixel value of the current block using the normal DC mode, since the positions of the pixels in the current block are predicted to be the same pixel values regardless of the positions of the adjacent pixels (A to L) It is impossible to predict an accurate pixel value according to the position of the pixel.

That is, although the actual pixels of the current block to be encoded may all have the same pixel value, they may have different pixel values depending on the positions of the pixels. As the positions of the pixels of the current block are closer to the adjacent pixels, And the position of the pixel of the current block is far from the adjacent pixel, the likelihood of being similar to the pixel value of the adjacent pixel is small. That is, the pixel value of the current block pixel is likely to be similar to the pixel value of the adjacent pixel as the position of the pixel is closer to the position of the adjacent pixel. However, in the method of predicting the pixel value of the current block using the conventional DC mode as described above, the relation between the position of the pixel of the current block and the position of the adjacent pixel is ignored, do.

However, according to the embodiment of the present invention, the pixel value of the current block pixel can be predicted by reflecting the relationship between the pixel position of the current block and the neighboring pixel position.

For example, if the pixel values of the pixels used in intra 4x4 mode prediction as shown in FIG. 10 are predicted according to an embodiment of the present invention, A pixel value is calculated by adding weights to the pixels I, J, K, and L and the adjacent pixels A, B, C, and D of the upper block.

Here, the weight may be added in inverse proportion to the distance calculated by calculating the distance between the position of the pixel of the current block to be predicted and the position of the adjacent pixel of the neighboring block. That is, the pixel value of each pixel of the current block is predicted using the pixel value of the adjacent pixel of the neighboring block (in particular, the pixel value of the adjacent pixel of the left block and the pixel value of the adjacent pixel of the upper block) If the distance between the position of the current block and the position of the adjacent pixel of the adjacent block is short, it is determined that the similarity between the current pixel and the adjacent pixel is great, and the weight is added to the pixel value of the adjacent pixel of the neighboring block, If the distance between adjacent pixels of the adjacent block is long, it is determined that the similarity between the current pixel and the adjacent pixel is small, and the weight is added to the pixel value of the adjacent pixel of the adjacent block.

In one embodiment of the present invention, as described above, the pixel values of one or more neighboring pixels included in one or more neighboring blocks are weighted and averaged according to the distance between each pixel of the current block and one or more neighboring pixels, Of the pixel value. Equation (2) expresses a formula for predicting the pixel value using the weighted average according to the distance.

Here, x is each pixel of the current block (a to p pixels in FIG. 10), P1 to Pn are adjacent pixels of the neighboring block (A to L pixels in FIG. 10), f1, f2, ... fn-1 and fn are weights according to the distances between the respective pixels x of the current block and the adjacent pixels P1 to Pn of the neighboring blocks. Further, N = f1 + f2 + + fn-1 + fn.

Using Equation (2), each pixel a to p of the current block shown in FIG. 10 can be predicted as shown in Equation (3). However, for the sake of convenience of explanation, in predicting the pixel value of each pixel, the neighboring block is limited to the left block of the current block and the upper block of the current block, and the neighboring pixels in the neighboring block also belong to the row and column It is limited to predicting each pixel of the current block using only adjacent pixels. However, the present invention is not limited to such a limitation, and a current pixel may be predicted using a part or all of adjacent pixels included in a neighboring block of the current block.

Here, the pixel value of the a pixel can be determined by the adjacent pixel A of the upper block and the adjacent pixel I of the left block. Are all the same and are separated by a distance (basic distance) of one pixel. Therefore, a pixel is calculated by adding a basic weighting value '1' to A pixels and I pixels, because a pixel is spaced by a basic distance from A pixels and I pixels. Assuming that a distance between all the pixels is '1', a = (1 x A + 1 x I) / (1 + 1) = (A + I) / 2.

The pixel value of the g pixel can be determined by the adjacent pixel C of the upper block and the adjacent pixel J of the left block. The position of the g pixel is determined by the position of the C pixel, (Base distance X 2) and the position of the J pixel is separated by the distance (base distance X 3) of the three pixels. Therefore, the weight for calculating the pixel value of the g pixel is given as '2' for the C pixel and '3' for the J pixel, and assuming that the distance between all the pixel positions is '1' g = (3xC + 2xJ) / (3 + 2) = (3C + 2J) / 5.

In the case of performing the DC mode prediction using the pixel values of the adjacent pixels of the adjacent block in which the weight is weighted according to the distance between the pixel of the current block and the adjacent pixel of the neighboring block, The predicted pixel values of the current block may be predicted to be different predicted pixel values according to each pixel position of the current block, unlike the case where the predicted pixel values of the current block have the same pixel values.

10, each of the left block and the upper block of the current block is used to calculate the predicted pixel value of the current block. However, the present invention is not limited to this example, and a predicted value of one pixel included in the current block may be obtained using all or a part of 16 pixel values from a to p of the left block and the upper block of the current block , It is possible to obtain a predicted value of one pixel included in the current block by using all or a part of one or more pixel values included in all the surrounding blocks or some blocks as well as the left and top blocks of the current block.

Prediction of the pixel value of the current block using the pixel value of the adjacent pixel reflecting the weight added according to the distance between the pixel position of the current block and the neighboring pixel position of the neighboring block is not limited to the image encoding apparatus 300 The same is performed by the intra prediction units 310 and 850 in the image decoding apparatus 800 as well.

In this manner, when the image encoding apparatus 300 and the image decoding apparatus 800 perform DC mode prediction, when it is determined that the current block is intra-predicted in the DC mode, intra-4x4 mode prediction or intra 16x The predicted current block is made more similar to the original current block by predicting the pixel value of the current block in consideration of the 16 mode prediction or the weight according to the distance to obtain the optimum predicted pixel value, The difference value between the block and the predicted current block can be reduced, so that the compression efficiency can be improved without reducing the performance of the intra prediction, and the amount of data to be transmitted can be reduced.

Although the image encoding apparatus 300 and the image decoding apparatus 800 are described as being implemented as independent apparatuses in the above description, the image encoding apparatus 300 and the image decoding apparatus 800 may be implemented in one apparatus . The encoding unit 350 and the decoding unit 810, the quantization unit 340 and the inverse quantization unit 820, the conversion unit 330, and the image encoding unit 300, The inverse transform unit 830, the subtractor 320 and the adder 840 and the intraprediction units 310 and 850 include a memory for storing the program and a microprocessor for executing each function by executing the program However, it may be implemented as a program module that performs each function in hardware such as the image encoding apparatus 300 and the image decoding apparatus 800. [

When the image encoding apparatus 300 and the image decoding apparatus 800 are implemented in a single apparatus, the respective components performing functions corresponding to each other, that is, the encoding unit 350 and the decoding unit 810, The quantization unit 340 and the inverse quantization unit 820, the transform unit 330 and the inverse transform unit 830, the subtraction unit 320 and the adder 840, and the intra prediction units 310 and 850, May be implemented as a module.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

As described above, the present invention provides an intra prediction method and apparatus for predicting, encoding, and decoding a current block of an image from neighboring blocks, which minimizes a difference between an actual current block and a predicted current block, / Decoding method and apparatus, it is possible to improve the efficiency of coding by reducing the difference between the actual block and the predicted block by predicting the current block to be encoded more accurately, thereby improving the compression efficiency Is a very useful invention.

Description of the Related Art
300: Image encoding apparatus 310, 850: Intra prediction unit
320: subtracter 330:
340: quantization unit 350: encoding unit
410: weighted pixel value calculation unit 420: predicted pixel value calculation unit
810: Decoding unit 820: Inverse quantization unit
830: Inverse transform unit 840:
850: Intra prediction unit

Claims (15)

delete An intra prediction apparatus for predicting a current pixel in a current block from a plurality of neighboring blocks existing in a same picture as a current block,
A weighted pixel value calculation unit for calculating a plurality of weighted pixel values by applying weights variably determined based on the positions of the current pixels in the current block to a plurality of neighboring pixels selected from the plurality of neighboring blocks; And
And a predictive pixel value calculation unit for determining a predictive pixel value for the current pixel using the plurality of weighted pixel values,
Wherein the plurality of peripheral pixels comprise:
A first pixel located at a position vertically adjacent to the current pixel as a pixel adjacent to an upper end of the current block,
A second pixel located at a position horizontally the same as the current pixel as a pixel adjacent to the left side of the current block,
A third pixel located at the top of the current block, and
And a fourth pixel located to the left of the current block,
The plurality of weighted pixel values may include:
A first weighted pixel value calculated by applying a first weight to the first pixel,
A second weighted pixel value calculated by applying a second weight to the second pixel,
A third weighted pixel value calculated by applying a third weight to the third pixel, and
And a fourth weighted pixel value calculated by applying a fourth weight to the fourth pixel. 3. The method of claim 2,
Wherein the weighted pixel value calculation unit determines the first weight value, the second weight value, the third weight value and the fourth weight value based on the position of the current pixel in the current block,
The predictive pixel value calculation unit may calculate the sum of the first weighted pixel value, the second weighted pixel value, the third weighted pixel value, and the fourth weighted pixel value as the first weighted value, the second weighted weight, And a sum of the first and second weights, and a sum of the fourth weights, as a predicted pixel value for the current pixel. 3. The method of claim 2,
Wherein the first weight is determined by a distance between the current pixel and the first pixel,
Wherein the second weight is determined by a distance between the current pixel and the second pixel. 3. The method of claim 2,
Wherein each of the weights is determined by a distance between the current pixel and each neighboring pixel in the plurality of neighboring blocks, and is determined to be a larger value as the distance is shorter. An intra prediction apparatus for predicting a current pixel in a current block from a plurality of neighboring blocks existing in a same picture as a current block,
A weighted pixel value calculation unit for calculating a plurality of weighted pixel values by applying weights variably determined based on the positions of the current pixels in the current block to a plurality of neighboring pixels selected from the plurality of neighboring blocks; And
And a predictive pixel value calculation unit for determining a predictive pixel value for the current pixel using the plurality of weighted pixel values,
Wherein the plurality of peripheral pixels comprise:
A first pixel located at a position vertically adjacent to the current pixel as a pixel adjacent to an upper end of the current block,
A second pixel located at the same horizontal position as the current pixel as a pixel adjacent to the left side of the current block, and
And at least one third pixel selected from the plurality of neighboring blocks,
The plurality of weighted pixel values may include:
A first weighted pixel value calculated by applying a first weight to the first pixel,
A second weighted pixel value calculated by applying a second weight to the second pixel, and
One or more third weighted pixel values calculated by applying a third weight corresponding to each of the one or more third pixels to the one or more third pixels,
Wherein the predictive pixel value calculation unit divides the sum of the weighted pixel values calculated from the first through third pixels by the weighted pixel value calculation unit by the sum of weights corresponding to the first through third pixels, And determines a prediction pixel value for the block.
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