KR20140057514A - Prediction block generating apparatus - Google Patents

Abstract

A prediction block generating apparatus according to the present invention utilizes auxiliary information for generating a prediction block included in a received information container, and effective intra-prediction candidate information of a current prediction unit to determine an intra-prediction mode of a current prediction unit. Then, the apparatus generates reference pixels in locations which are not available in generating an intra-prediction block, by using available reference pixels. Next, the apparatus adaptively filters reference pixels close to the current prediction unit based on the intra-prediction mode of the determined intra-prediction unit and size information of the current prediction unit. Finally, the apparatus utilizes the reference pixels corresponding to the intra-prediction mode of the determined current prediction unit to generate a prediction block of the current prediction unit. Therefore, a prediction block, which is close to an original image, is generated, and an image compression ratio is raised.

Description

[0001] Prediction block generating apparatus [0002]

The present invention relates to an apparatus for generating a moving picture prediction block, and more particularly, to an apparatus for generating a prediction block capable of reducing an amount of coding of a residual block.

In an image compression method such as MPEG-1, MPEG-2, MPEG-4 H.264 / MPEG-4 and AVC (Advanced Video coding), one picture is divided into macroblocks for coding an image. Then, each macroblock is encoded using inter prediction or intra prediction.

Among these, intra prediction does not refer to a reference picture to encode a block of a current picture but performs encoding using pixel values spatially adjacent to the current block to be encoded. First, an intra prediction mode having a small distortion is selected by comparing the original macroblock with an adjacent pixel value. Next, prediction values for the current block to be encoded are calculated using the selected intra-prediction mode and adjacent pixel values, and a difference between the predicted value and the pixel value of the original current block is obtained, and then the resultant is encoded through transcoding, quantization, and entropy encoding . The prediction mode is also coded.

Here, the intra-prediction modes are roughly divided into a 4x4 intra-prediction mode, an 8x8 intra-prediction mode, a 16x16 intra-prediction mode, and a chrominance intra-prediction mode.

In the 16x16 intra prediction mode according to the prior art, there are four modes of a vertical mode, a horizontal mode, a direct current (DC) mode, and a plane mode.

The conventional 4x4 intra prediction modes include a vertical mode, a horizontal mode, a DC (direct current) mode, a diagonal down-left mode, a diagonal down-right mode, There are a total of nine modes: vertical right mode, vertical left mode, horizontal-up mode, and horizontal-down mode.

Prediction mode numbers indexed in each mode are numbers determined according to the frequency with which each mode is used. Vertical mode, which is a probability 0 mode, is the most commonly used mode when intra prediction is performed on a target block. Horizontal (up-8) mode is the least used mode.

According to the H.264 standard, in coding an image, a current block is coded in 13 modes of the 4 × 4 intra prediction mode and the 16 × 16 intra prediction mode, and a bitstream .

However, when some or all of the pixel values adjacent to the pixels included in the current block do not exist or are not coded, some or all of the intra prediction modes can not be applied. If intra prediction is performed by selecting one of the applicable intra modes, the residual signal between the current block and the prediction block becomes large, thus reducing the efficiency of image compression.

An object of the present invention is to provide a prediction block generating apparatus for generating a prediction block similar to an original image.

The apparatus for generating a prediction block according to the present invention includes a prediction mode determining unit for determining an intra prediction mode of a current prediction unit by using additional information for generating a prediction block included in a received additional information container and effective intra prediction mode candidate information of a current prediction unit, A reference pixel generating unit for generating reference pixels at positions that are not available for generating the intra prediction block and the intra prediction block using available reference pixels, And a prediction block generation unit for generating a prediction block of a current prediction unit using reference pixels corresponding to the determined intra prediction mode of the current prediction unit do.

A method and an apparatus for intraprediction encoding and decoding according to the present invention generate a reference pixel to generate a prediction block close to an original image and adaptively filter the reference pixel to generate a prediction block close to the original image. Further, by adaptively filtering the prediction block according to the intra prediction mode, the residual signal can be further reduced, and the image compression ratio can be increased.

1 is a block diagram illustrating a moving picture encoding apparatus according to the present invention.
2 is a flowchart illustrating an operation process of the scanning unit according to the present invention.
3 is a block diagram illustrating a video decoding apparatus according to an embodiment of the present invention.
4 is a block diagram illustrating an intra predictor according to the present invention.
5 is a diagram illustrating positions of reference pixels used in intra prediction according to the present invention.
6 is a diagram illustrating a method of generating a reference pixel according to the present invention.
7 is a block diagram illustrating an intra predictor of the decoding apparatus according to the present invention.

Hereinafter, various embodiments of the present invention will be described in detail with reference to exemplary drawings. It is to be understood that the invention is not to be limited to the specific embodiments thereof except as defined in the appended claims and all changes, Should be understood to include. Like reference numerals are used for like elements in describing each drawing.

For image coding, each picture is composed of a plurality of slices, and each slice is made up of a plurality of coding units. In the HD-level or higher-level video, there are many regions where the image is relatively flat. Therefore, it is possible to increase the image compression rate by encoding in units of units larger than the 16x16 MB.

The encoding unit according to the present invention may be a 32x32 block, a 64x64 block, as well as a 16x16 MB. A block of 8x8 size or smaller can also be an encoding unit. For convenience, the largest encoding unit is referred to as a super macro block (SMB). The size of the super macro block can be determined as information indicating the size of the smallest encoding unit and depth information. The depth information indicates a size difference value between the super macroblock and the smallest encoding unit.

Therefore, the coding units to be used for coding all the pictures of the video sequence may be SMBs and their subblocks. The encoding unit to be used for the video sequence can be specified as the default or specified in the sequence header.

The SMB (i.e., the maximum encoding unit) is composed of one or more encoding units. Therefore, the SMB has a recursive coding tree form to include a division structure and an encoding unit of an encoding unit. Therefore, the description based on the SMB is as follows. If the SMB is not divided into four sub-coding units, the coding tree may be composed of information indicating that the SMB is not divided and one coding unit. However, if the SMB is divided into four sub-coding units, the coding tree may be composed of information indicating that the SMB is divided and four sub-coding trees. Similarly, each sub-encoding tree has the same structure as an encoding tree of SMB units. However, it is not divided below the minimum encoding unit.

On the other hand, Intra Pediction or Inter Prediction is performed for each coding unit in the coding tree per coding unit itself or sub-block unit. The unit for performing the intra prediction or the inter prediction is referred to as a prediction unit. The prediction unit for intra prediction may be 2Nx2N or NxN. Prediction units for inter prediction may be 2Nx2N, 2NxN, Nx2N, NxN. Where 2N denotes the length and breadth of the coding unit .

The encoding unit should include the prediction mode of the prediction unit in the encoding unit and the size information of the prediction unit (partmode). In order to increase the coding efficiency, the prediction mode information and the size information of the prediction unit may be combined and jointly coded. In this case, a prediction type (pred_type) jointly coded is included for each coding unit.

The encoding unit includes an additional information container for each prediction unit. The additional information container includes additional information necessary for generating a prediction block of the prediction unit. In case of intra prediction, the side information includes encoded intra prediction information. In the case of inter prediction, the additional information includes coded motion information. The motion information includes a motion vector and a reference picture index.

The encoding unit includes the residual signaling container of the encoding unit. The residual signal container includes one conversion tree, one luminance residual signal container, and two color difference residual signal containers. The conversion tree indicates the presence or absence of residual signals in the conversion blocks in the residual signal container made of a tree structure. The residual signal container consists of a recursive tree structure. That is, the residual signal container of the coding unit will be described with reference to the following. First, if the residual signal container of the encoding unit is not divided into four lower residual signal containers, the residual signal container includes quantization information (residual quantization parameter) and encoded residual signal. If the residual signal container is divided into four lower residual signal containers, the residual signal container of the encoding unit includes quantization information and four lower residual signal containers. The lower residual signal container has the same structure as the encoding unit residual signal container except that it does not include quantization information.

On the other hand, only the prediction unit in which the coding units are equally divided has been described. However, when the image has a boundary in a specific direction or a specific position due to the characteristic of the image, when using the above-described uniform division, different prediction units are used for similar data in the boundary portion, so that the residual signal can not be effectively reduced.

Therefore, in such a case, it is more effective to perform intra or inter prediction by dividing the SMB or MB in a specific direction according to the shape of the boundary portion of the image.

The simplest adaptive mode is to segment the coding units into two blocks using a straight line to extract the statistical dependence of the local topography of the prediction region. That is, the boundary portion of the image is matched with a straight line and divided. In this case, it is preferable to limit the dividable directions to a predetermined number. For example, the method of dividing a block can be limited to four directions: horizontal, vertical, upward diagonal, and downward diagonal. Also, it may be limited to horizontal and vertical. The divisible number is 3, 5, 7, and so on. The number of divisible numbers can be different from the size of the block. For example, it is possible to increase the number of divisions relative to a large-size encoding unit.

In the case of inter prediction, when one encoding unit is divided into two prediction blocks in order to more adaptively predict, it is necessary to perform motion prediction and motion compensation on each of the prediction blocks. Therefore, the motion information is obtained for each divided area, and the residual signal with the prediction block obtained based on the motion information is encoded.

 A residual signal for each of the two prediction blocks divided for one coding unit is obtained, and two residual signals are added to form one coding unit residual signal, and the resultant signal is transcoded. In this case, since the probability that the distribution of the residual signals of the respective divided regions is different from each other is large, the residual signal for one coding unit can be generated by multiplying the value of one region by a constant value have. In addition, one residual signal can be generated by smoothing the boundary portion by overlapping the boundary portions of the two residual signals.

Alternatively, a block can be generated and padded by padding for each divided area of the block. That is, when coding the current divided region among the two divided regions, the other divided regions constituting the block may be padded with the values of the current divided region into one block, and then two-dimensional transformed coding may be performed.

1 is a block diagram illustrating a moving picture encoding apparatus according to the present invention.

1, a moving picture encoding apparatus 100 according to the present invention includes a picture dividing unit 110, a transform unit 120, a quantization unit 130, a scanning unit 131, an entropy coding unit 140, An inter prediction unit 160, an inverse quantization unit 135, an inverse transformation unit 125, a post-processing unit 170, a picture storage unit 180, a subtraction unit 190, and an addition unit 195, .

The picture division unit 110 analyzes the input video signal, divides the picture into the coding units of a predetermined size for each largest coding unit, determines a prediction mode, and determines the size of the prediction unit for each coding unit. The picture division unit 110 sends the prediction unit to be encoded to the intra prediction unit 150 or the inter prediction unit 160 according to the prediction mode. Further, the picture division unit 110 sends the prediction unit to be encoded to the subtraction unit 190.

The transform unit 120 transforms the residual block, which is a residual signal of the prediction block generated by the intra prediction unit 150 or the inter prediction unit 160, with the original block of the inputted prediction unit. The residual block is configured as a coding unit. The residual block composed of coding units is divided into optimal conversion units and converted. Different transformation matrices may be determined depending on the prediction mode (intra or inter). Also, since the residual signal of the intra prediction has directionality according to the intra prediction mode, the transformation matrix can be adaptively determined according to the intra prediction mode. The transformation unit can be transformed by two (horizontal, vertical) one-dimensional transformation matrices. For example, in the case of inter prediction, a predetermined conversion matrix is determined. On the other hand, in case of the intra prediction, when the intra prediction mode is horizontal, the probability that the residual block has the direction in the vertical direction becomes high. Therefore, the DCT-based integer matrix is applied in the vertical direction, Or a KLT-based integer matrix. When the intra prediction mode is vertical, a DST-based or KLT-based integer matrix is applied in the vertical direction and a DCT-based integer matrix is applied in the horizontal direction. In case of DC mode, DCT-based integer matrix is applied in both directions. Further, in the case of intra prediction, the transformation matrix may be adaptively determined depending on the size of the conversion unit.

The quantization unit 130 determines a quantization step size for each encoding unit for quantizing the coefficients of the residual block transformed by the transform matrix. And quantizes the coefficients of the transform block using a quantization matrix determined according to the determined quantization step size and the prediction mode. The quantization unit 130 uses the quantization step size of the encoding unit adjacent to the current encoding unit as the quantization step size predictor of the current encoding unit. The quantization unit 130 searches for the quantization step size of the effective encoding unit as the quantization step size predictor of the current encoding unit by searching in the order of the left encoding unit, the upper encoding unit, and the upper left encoding unit of the current encoding unit, To the encoding unit (140).

On the other hand, when the slice is divided into coding units, there is a possibility that the left coding unit, the upper coding unit, and the upper left coding unit of the current coding unit are not present. On the other hand, there may be a coding unit that exists before in the coding order in the maximum coding unit. Therefore, the coding units adjacent to the current coding unit and the coding unit immediately before the coding order in the maximum coding unit can be candidates. In this case, 1) the left encoding unit of the current encoding unit, 2) the upper encoding unit of the current encoding unit, 3) the upper left encoding unit of the current encoding unit, and 4) . The order may be changed, and the upper left side encoding unit may be omitted.

The quantized transform block is provided to the inverse quantization unit 135 and the scanning unit 131.

The scanning unit 131 scans the coefficients of the quantized transform block and converts them into one-dimensional quantization coefficients. Since the coefficient distribution of the transform block after quantization may be dependent on the intra prediction mode, the scanning scheme is determined according to the intra prediction mode. The coefficient scanning method may be determined depending on the size of the conversion unit.

The inverse quantization unit 135 dequantizes the quantized quantized coefficients. The inverse transform unit 125 restores the inversely quantized transform coefficients into residual blocks in the spatial domain. The adder combines the residual block reconstructed by the inverse transforming unit and the prediction block from the intra prediction unit 150 or the inter prediction unit 160 to generate a reconstruction block.

The post-processing unit 160 performs a deblocking filtering process for eliminating the blocking effect generated in the reconstructed picture, an adaptive offset application process for compensating the difference value with respect to the original image on a pixel-by-pixel basis, And performs an adaptive loop filter process to compensate the value.

The deblocking filtering process is preferably applied to a boundary of a prediction unit and a conversion unit having a size larger than a predetermined size. The size may be 8x8. The deblocking filtering process may include determining a boundary to be filtered, determining a bounary filtering strength to be applied to the boundary, determining whether to apply a deblocking filter, And selecting a filter to be applied to the boundary if it is determined to apply the boundary.

Whether or not the deblocking filter is applied is determined based on i) whether the boundary filtering strength is greater than 0 and ii) whether a pixel value at a boundary between two blocks adjacent to the boundary to be filtered (P block, Q block) Is smaller than a first reference value determined by the quantization parameter.

The filter is preferably at least two or more. If the absolute value of the difference between two pixels located at the block boundary is greater than or equal to the second reference value, a filter that performs relatively weak filtering is selected. And the second reference value is determined by the quantization parameter and the boundary filtering strength.

The adaptive loop filter process can perform filtering based on a value obtained by comparing a reconstructed image and an original image through a deblocking filtering process or an adaptive offset applying process. The adaptive loop filter is detected through a single Laplacian Activity value based on a 4x4 block. The determined ALF may be applied to all the pixels included in the 4x4 block or the 8x8 block. Whether or not the adaptive loop filter is applied can be determined for each encoding unit. The size and the coefficient of the loop filter to be applied according to each coding unit may be changed. Information indicating whether or not the adaptive loop filter is applied, filter coefficient information, filter type information, and the like can be included in each slice header and transmitted to the decoder in units of coding units. In the case of the color difference signal, it is possible to determine whether or not the adaptive loop filter is applied in units of pictures. The shape of the loop filter may have a rectangular shape unlike the luminance.

The picture storage unit 180 receives the post-processed image data from the post-processing unit 160, and restores and restores the pictures on a picture-by-picture basis. The picture may be a frame-based image or a field-based image. The picture storage unit 180 has a buffer (not shown) capable of storing a plurality of pictures.

The inter-prediction unit 150 performs motion estimation using at least one reference picture stored in the picture storage unit 180, and determines a reference picture index and a motion vector indicating a reference picture. Then, based on the determined reference picture index and motion vector, a prediction block corresponding to a prediction unit to be coded is extracted from a plurality of reference pictures stored in the picture storage unit 150 and used for motion estimation .

The intraprediction unit 140 performs intraprediction encoding using the reconstructed pixel values in the picture including the current prediction unit. The intra prediction unit 140 receives the current prediction unit to be predictively encoded and selects one of a predetermined number of intra prediction modes according to the size of the current block to perform intra prediction. The intra prediction unit adaptively filters the reference pixels to generate an intra prediction block. If reference pixels are not available, reference pixels may be generated using available reference pixels.

The entropy encoding unit 130 entropy-codes quantization coefficients quantized by the quantization unit 130, intra prediction information received from the intra prediction unit 140, motion information received from the inter prediction unit 150, and the like.

Fig. 2 is a flowchart showing a scanning operation process of the scanning unit 131 of Fig.

First, it is determined whether to divide the quantized coefficient blocks into a plurality of subsets (S110). The determination of whether or not to divide is dependent on the size of the current conversion unit. That is, when the size of the conversion unit is larger than the first reference size, the encoded quantized coefficients are divided into a plurality of subsets. The first reference size is preferably 4x4 or 8x8. The predetermined size information may be transmitted to a decoder through a picture header or a slice header.

If it is determined that the quantized coefficient blocks are not divided into a plurality of subsets, a scan pattern to be applied to the quantized coefficient block is determined (S120). Then, the coefficients of the quantized coefficient block are scanned according to the determined scan pattern (S130). The scan pattern may be adaptively determined according to a prediction mode and an intra prediction mode.

In the case of the inter prediction mode, only a predetermined scan pattern (for example, a zigzag scan) can be applied. Also, one of a plurality of predetermined scan patterns may be selected and scanned, and the scan pattern information may be transmitted to the decoder.

In case of intra prediction, a predetermined scan pattern can be applied according to the intra prediction mode. For example, a horizontal priority scan is applied to a predetermined number of intra prediction modes in the vertical intra prediction mode and adjacent prediction directions. A vertical scan is applied to a predetermined number of intra prediction modes having a horizontal intra prediction mode and an adjacent prediction direction. The predetermined number varies depending on the number of intra prediction modes (or the number of directional intra prediction modes) allowed per prediction unit or the size of the prediction unit. For example, when the number of directional intra-prediction modes allowed for the current prediction unit is 16, it is preferable that the number of directional intra-prediction modes is two for both of the horizontal and vertical intra-prediction modes. When the number of directional intra-prediction modes allowed for the current prediction unit is 33, it is preferable that the number of directional intra-prediction modes is 4 for both of the horizontal and vertical intra-prediction modes.

On the other hand, zigzag scan is applied to the non-directional modes. The non-directional mode may be a DC mode or a planar mode.

If it is determined that the quantized coefficient blocks are divided into a plurality of subsets, the transform quantized coefficient blocks are divided into a plurality of subsets (S140). The plurality of subsets comprises one main subset and at least one or more remaining subsets. The main subset is located on the upper left side including the DC coefficient, and the remaining subset covers an area other than the main subset.

Next, a scan pattern to be applied to the subset is determined (S150). The scan pattern is applied to all subsets. The scan pattern may be adaptively determined according to a prediction mode and an intra prediction mode. In the case where the size of the current transform quantized coefficient block (the size of the transform block) is larger than the second reference size (for example, 8x8), only the zigzag scan can be applied. Therefore, the above step is performed only when the first reference size is smaller than the second reference size.

In the inter prediction mode, the scan pattern in the subset may be a predetermined scan pattern (e.g., a zigzag scan). In the case of intra prediction, it is the same as in S120.

The scan order of the quantization coefficients in the subset scans in the reverse direction. That is, quantization coefficients that are not 0 in the backward direction from the last non-zero quantization coefficient in the subset can be scanned and entropy-encoded according to the scan pattern.

Next, the quantization coefficients are scanned according to the scan pattern for each subset (S160). The scan order of the quantization coefficients in the subset scans in the reverse direction. That is, quantization coefficients that are not 0 in the backward direction from the last non-zero quantization coefficient in the subset can be scanned and entropy-encoded according to the scan pattern.

In addition, a scan pattern between subsets applies a zigzag scan. The scan pattern is preferably scanned to the remaining subsets in the forward direction from the main subset, but vice versa. In addition, a scan pattern between subsets may be applied in the same manner as a scan pattern applied in a subset.

On the other hand, the encoder transmits to the decoder information indicating the position of the last non-zero quantization coefficient in the conversion unit. Information indicating the position of the last non-zero quantization coefficient in each subset is also transmitted to the decoder. The information may be information indicating the position of the last non-zero quantization coefficient in each subset.

3 is a block diagram illustrating a moving picture decoding apparatus according to an embodiment of the present invention.

3, the moving picture decoding apparatus according to the present invention includes an entropy decoding unit 210, an inverse scanning unit 220, an inverse quantization unit 230, an inverse transform unit 240, an intra prediction unit 250, A post-processing unit 270, a picture storage unit 280, an adding unit 290, and an intra / inter changeover switch 295, as shown in FIG.

The entropy decoding unit 210 decodes the received encoded bit stream into intraprediction information, inter prediction information, quantization coefficient information, and the like. The entropy decoding unit 210 supplies the decoded inter prediction information to the inter prediction unit 260. [ The entropy decoding unit 210 supplies the intra prediction information to the intra prediction unit 250 and the inverse transformation unit 240. In addition, the entropy decoding unit 210 supplies the inverse quantization coefficient information to the inverse scanning unit 220.

The inverse scanning unit 220 converts the quantized coefficient information into a two-dimensional inverse quantized block. One of a plurality of reverse scanning patterns is selected for the conversion. The coefficient inverse scanning pattern is determined based on at least one of a prediction mode and an intra prediction mode. The operation of the inverse scanning unit 220 is the same as the inverse process of the operation of the scanning unit 131 described above.

The inverse quantization unit 230 determines the quantization step size predictor of the current encoding unit. The predictor decision process is the same as the predictor decision process of the quantization unit 130 of FIG. The inverse quantization unit 230 adds the determined quantization step size predictor and the received residual quantization step size to obtain the quantization step size applied to the current inverse quantization block. The inverse quantization unit 230 restores the inverse quantization coefficient using the quantization matrix to which the quantization step size is applied. Different quantization matrices are applied according to the size of the current block to be restored and a quantization matrix is selected based on at least one of a prediction mode and an intra prediction mode of the current block with respect to blocks of the same size.

The inverse transform unit 240 inversely transforms the inverse quantized block to reconstruct the residual block. Then, the reconstructed quantized coefficient is inversely transformed to reconstruct the residual block. The inverse transform matrix to be applied to the inverse quantization block may be adaptively determined according to a prediction mode (intra or inter) and an intra prediction mode. Since the inverse transformation matrix of the transformation matrix applied to the transformation unit 120 of FIG. 1 is determined, detailed description is omitted.

 The addition unit 290 reconstructs the image block by adding the residual block reconstructed by the inverse transform unit 240 to the intra prediction unit 250 or the prediction block generated by the inter prediction unit 260. [

The intraprediction unit 250 restores the intra prediction mode of the current block based on the intra prediction information received from the entropy decoding unit 210. A prediction block is generated according to the restored intra prediction mode.

The inter-prediction unit 260 reconstructs the reference picture index and the motion vector based on the inter-prediction information received from the entropy decoding unit 210. A prediction block for the current block is generated using the reference picture index and the motion vector. When motion compensation with a decimal precision is applied, a prediction block is generated by applying a selected interpolation filter.

The operation of the post-processing unit 270 is the same as that of the post-processing unit 160 of FIG.

The picture storage unit 280 stores the decoded picture, which is post-processed by the post-processing unit 270, on a picture-by-picture basis.

4 is a block diagram showing an intra predictor 150 of the encoding apparatus 100 according to the present invention.

4, the intraprediction unit 150 includes a reference pixel generation unit 151, a reference pixel filtering unit 152, a prediction mode determination unit 153, a prediction block generation unit 154, a prediction block filtering unit 155, and a prediction mode encoding unit 156.

The reference pixel generation unit 151 determines whether to generate reference pixels for intraprediction, and generates reference pixels when it is necessary to generate them.

5 is a diagram showing the positions of reference pixels used in intra prediction of a current prediction unit. As shown in FIG. 5, the upper reference pixel of the current prediction unit is pixels (regions C and D) existing twice the width of the current prediction unit, and the left reference pixels are the (Regions A and B) that exist twice as much as the other pixels.

The reference pixel generation unit 151 determines whether reference pixels at all the positions are available. When a part of the reference pixels is not available, reference pixels of unusable positions are generated using available reference pixels.

First, a description will be given of a case where reference pixels in any one of the upper and left regions of the current prediction unit to be encoded are not available.

For example, when the current prediction unit is located at the upper boundary of the picture or slice, the upper reference pixels (regions C and D) of the current prediction unit do not exist. Similarly, when the current prediction unit is located at the left boundary of the picture or slice, the left reference pixels (areas A and B) do not exist. When one of the reference pixels is not available, the reference pixel can be generated by copying the nearest available reference pixel. In the former case, the closest usable reference pixel is the uppermost left reference pixel (i.e., the uppermost reference pixel in the area A). In the latter case, the closest usable reference pixel is the upper leftmost reference pixel (i.e., the leftmost reference pixel in the area C). The application of the above method may be default, but may be adaptively applied to the sequence unit, the picture unit, or the slice unit, if necessary.

Next, a case where a part of the upper or left reference pixels of the current prediction unit to be encoded is not available will be described. There are two cases: 1) there are reference pixels usable only in one direction, and 2) there are reference pixels available to both.

1) will be described.

For example, if the current prediction unit is located at the right boundary of the picture or slice, or at the right boundary of the maximum coding unit, the reference pixels of the region D are not available. Similarly, if the current prediction unit is located at the lower boundary of the picture or slice or the lower boundary of the largest coding unit, the reference pixels of the region B are not available.

In this case, it is possible to generate reference pixels by copying available reference pixels existing at the closest position. Alternatively, a plurality of available reference pixels existing at the closest position may be used to generate reference pixels.

 2) will be described.

For example, if the current prediction unit is located at the upper boundary of the slice and the upper right prediction unit of the current prediction unit is available, the reference pixels corresponding to the region C of the current prediction unit are not available, Reference pixels located at D are available. In this way, when both available reference pixels are available, one usable reference pixel that is closest to each direction is selected, and these (that is, the uppermost reference pixel of the region A and the leftmost Reference pixels) are used to generate reference pixels at positions that are not available.

A rounded average value of the two reference pixels (pixels located closest to each direction) may be generated as a reference pixel value. However, when the usable reference pixel region is large, it is more likely to generate the reference pixel by using the linear interpolation method because there is a high possibility that a step between the available pixel and the generated pixel occurs. A reference pixel which is not available at the current position can be generated in consideration of the position with respect to the two available reference pixels.

Next, a case in which both the upper and left reference pixels of the current prediction unit to be encoded are not available will be described. For example, if the current prediction unit is adjacent to the picture or slice upper left boundary, there are no reference pixels available.

In this case, some or all reference pixels may be generated using two or more pixels existing within the current prediction unit. The number of pixels present in the current prediction unit used to generate the reference pixel may be 2 or 3.

6 is a diagram illustrating a method of generating reference pixels according to the present invention.

Referring to Fig. 6, the case of using two pixels will be described first. And a pixel different from the upper left pixel (O) of the current prediction unit is used. The other pixel may be an upper right pixel (?), A lower left pixel (?), And a lower right pixel (?). When the upper left pixel () and the upper right pixel () are used, the upper left pixel and the upper right pixel are copied to the corresponding upper positions, and the copied upper left pixel and upper right pixel To generate reference pixels in the area (area C) therebetween. The generated reference pixels may be a rounded mean value of the two reference pixels (copied upper left pixel and upper right pixel) or a value generated in the linear interpolation method. The upper right pixel (□) is copied or reference pixels of the area D are generated by using a plurality of upper generation reference pixels. The same method as above is also applied when the left upper pixel (O) and the lower left pixel (?) Of the current prediction unit are used. When the upper left side pixel (O) and the lower right side pixel (V) of the current prediction unit are used, the lower right side pixel pixel (V) is copied to the reference pixel position at the same position in the horizontal direction and the vertical direction. The reference pixel generation method thereafter applies the same method as above.

The case of using three pixels will be described first. The left upper pixel (O), the upper right pixel (), and the lower left pixel (DELTA) of the current prediction unit can be used. In this case, after each pixel is copied to the corresponding reference pixel position, the remaining reference pixels are generated using the pixels. The method of generating the remaining reference pixels is the same as the case of using the above two pixels.

On the other hand, when the above method is used, the pixels inside the current prediction unit used for generating the reference pixels must be transmitted to the decoder. In this case, in order to reduce the information transfer amount, values other than the upper left pixel (O) are transmitted with the difference value from the upper left pixel (O). Also, the upper left pixel value used for generating the reference pixel may be a quantized value, and may be entropy encoded and transmitted.

The method of generating reference pixels using two or more pixels existing within the current prediction unit is effective when the slice type is intra (I).

Another method of generating a reference pixel when both the upper and left reference pixels of the current prediction unit to be encoded are not available will be described. This scheme is effective when the slice type is not intra (I).

First, it is determined whether or not pixels exist in the same position as the reference pixels of the current prediction unit in the previously coded reference picture of the current block. If so, the reference pixels of the current prediction unit are generated by copying the pixels in the reference picture.

If it is not present, it is determined whether or not pixels are present in the previously coded reference picture at a position closest to the position of the reference pixels of the current prediction unit (one pixel apart). If they are present, And is used as a reference pixel.

 The reference pixel filtering unit 152 adaptively filters the reference pixels of the current prediction unit. This is for smoothing the amount of change in pixel values between reference pixels, and applies a low-pass filter. The low-pass filter can be a [1, 2, 1] or a 5-tap filter [1, 2, 4, 2, 1] which is a 3-tap filter.

In addition, it is possible to apply the filter adaptively according to the size of the current prediction unit. For example, if the current prediction unit is larger than a predetermined size, the filter may not be applied. Specifically, when the size of the current prediction unit is 64x64, the filter is not applied.

Also, the low-pass filter may be adaptively applied according to a current prediction unit size and an intra prediction mode.

When the intra prediction mode is horizontal or vertical, one reference pixel is used to generate the pixels of the prediction block. Therefore, in this case, the filter is not applied. When the intraprediction mode is DC, since the average value of the reference pixels is used, it is not affected by the step difference between the reference pixels. Therefore, the filter is not applied even in the DC mode.

On the other hand, for modes in which the intra-prediction direction is inclined by 45 占 with respect to the horizontal or vertical direction, the filter is applied irrespective of the size of the current prediction unit. In this case, a first filter may be used for a prediction unit smaller than a predetermined size, and a second filter whose smoothing effect is larger for a prediction unit of a predetermined size or larger may be used. The predetermined size may be 16x16.

On the other hand, in a mode other than the above-mentioned mode (6 kinds) in which at least two reference pixels are used to generate the pixels of the prediction block, it can be adaptively applied according to the current prediction unit size and the intra prediction mode. In the planar mode, however, no filtering is performed on the reference pixels.

In addition, a filter may not be applied to the reference pixels generated by the linear combination.

The prediction block generation unit 153 generates a prediction block corresponding to the intra prediction mode. The prediction block is generated using a linear combination of reference pixels or reference pixels based on an intra prediction mode. The reference pixels used for generating the prediction block may be reference pixels filtered by the reference pixel filtering unit 152. [

The prediction block filtering unit 154 adaptively filters the prediction block generated by the prediction block generating unit 153 according to the used intra prediction mode. The operation is to minimize the residual signal of the generated prediction block and the current prediction unit to be encoded. That is, the difference value between the reference pixels and the pixels in the adjacent prediction block may vary according to the intra prediction mode. Therefore, by filtering the pixels in the prediction block generated by the intra prediction mode generating a large number of steps, the residual can be reduced.

In the DC mode, since a prediction block is made of the average value of the reference pixels, a step may occur between the reference pixels and the pixels in the adjacent prediction block. Therefore, the pixels of the upper line and the pixels of the left line in the prediction block adjacent to the reference pixels are filtered using the reference pixels. Specifically, since the adjacent reference pixels are two (the upper reference pixel and the left reference pixel) in the upper left corner in the prediction block, the pixels in the upper left corner are filtered (or smoothed) using the 3-tap filter, )do. The other pixels (i.e., the pixels on the upper line in the prediction block and the pixels on the left line) are filtered using a 2-tap filter because there are one adjacent reference pixel.

The reference blocks generated by the mode numbers 0 and 6 and the intra prediction modes (mode numbers 22, 12, 23, 5, 24, 13, and 25) having the direction between the modes are referred to as upper reference A prediction block is generated using only pixels. Therefore, the pixels of the left line of the generated prediction block adjacent to the reference pixel may become larger in the downward direction.

In addition, the reference blocks generated by the mode numbers 1, 9 and the intra prediction modes (mode numbers 30, 16, 31, 8, 32, 17, 33) having the directivity between the above- A prediction block is generated using only pixels. Therefore, the pixels on the upper line of the generated prediction block adjacent to the reference pixel may have a larger step as they go to the right.

Therefore, in order to compensate the step difference, some pixels of the prediction block are adaptively filtered also in the directional mode other than DC.

When the mode number is 6, all or some pixels of the left line in the generated prediction block adjacent to the left reference pixel are filtered. Some pixels of the left line may be a part of the lower side of the left line, for example, N / 2 pixels. Where N is the height of the current prediction unit.

Similarly, when the mode number is 9, all or some pixels of the upper line in the adjacent generated prediction block are filtered. Some pixels of the upper line may be a part of the right side of the upper line, for example, M / 2 pixels. Where M represents the width of the current prediction unit.

Also, among the modes having the directionality between the mode numbers 0 and 6, the filtering can be performed in the same manner as the mode number 6 for a predetermined number of modes having a direction close to the mode number 6. In this case, the farther from the mode number 6 the farther the mode is, the more or less the number of pixels to be filtered can be.

The same method can also be applied to modes having directionality between the mode numbers 1 and 9.

On the other hand, it can be applied adaptively according to the size of the current prediction unit. For example, a filter may not be applied to a prediction unit of a predetermined size or smaller in each intra prediction mode.

The prediction mode determining unit 153 determines the intra prediction mode of the current prediction unit using the reference pixels. The prediction mode determining unit 153 can determine the mode in which the coding amount of the residual block for each intra prediction mode is the minimum to be the intra prediction mode of the current prediction unit. A prediction block is generated according to each intra prediction mode in order to obtain a residual block. The prediction block may be a prediction block using pixels filtered by the reference pixel filtering unit according to each intra prediction mode or a prediction block filtered by the prediction block filtering unit 155 according to a predetermined condition .

The prediction block transmission unit 157 transmits the prediction block generated corresponding to the intra prediction mode determined by the prediction mode determination unit 155 to the subtraction unit 190.

The prediction mode encoding unit 156 encodes the intra prediction mode of the current prediction unit determined by the prediction mode determination unit 155. [ The prediction mode encoding unit 156 may be included in the intraprediction unit 150 or may be performed in the entropy encoding unit 140.

The prediction mode encoding unit 156 encodes the intra prediction mode of the current prediction unit using the upper intra prediction mode of the current prediction unit and the left intra prediction mode of the current prediction unit.

First, the upper and left intra prediction modes of the current prediction unit are derived. When there are a plurality of upper prediction units of the current prediction unit, the intra prediction mode of the first effective prediction unit is set to the upper intra prediction mode while scanning in a predetermined direction (for example, right to left). Even when a plurality of left prediction units exist in the current prediction unit, the intra prediction mode of the effective first prediction unit can be set to the left intra prediction mode while scanning in a predetermined direction (e.g., lower phase). Or may set the smallest mode number among the mode numbers of the plurality of valid prediction units to the upper intra prediction mode.

If the upper intra prediction mode or the left intra prediction mode is not valid, the DC mode (mode number 2) may be set to the upper or left intra prediction mode. When the upper or left intra prediction mode is not valid, there is no corresponding intra prediction unit.

If the upper or left intra prediction mode is equal to or greater than the number of intra prediction modes allowed in the current prediction unit, the upper or left intra prediction mode is converted into one of a predetermined number of intra prediction modes. The predetermined number varies with the size of the current prediction unit. For example, if the size of the current prediction unit is 4x4, it is mapped to one of nine modes (modes 0 to 8). If the size of the current prediction unit is 64x64, mapping is performed to one of three modes do. Also, it may be converted into one of the intra prediction modes allowed in the current prediction unit.

Next, if the intra prediction mode number of the current prediction unit is the same as one of the left and upper intra prediction mode numbers, a flag indicating the same and a flag indicating one of the upper and left intra prediction modes are transmitted . In this case, if the left and upper intra prediction modes are the same, only a flag indicating the same can be transmitted. If only one of the upper and left intraprediction modes is valid and is identical to the intra prediction mode of the current block, only a flag indicating that the mode is the same as the mode of the adjacent block can be transmitted.

However, when the intra prediction mode of the current prediction unit is different from the left and upper intra prediction modes, the intra prediction mode number of the current prediction unit and the left and upper intra prediction mode numbers are compared. Prediction mode number of the current prediction unit out of the left and upper intra prediction mode numbers is calculated and a value obtained by decrementing the intra prediction mode number of the current prediction unit by the number of the above case is used to determine the final The intra prediction mode is determined. Here, when the left and upper intra prediction mode numbers are the same, they are treated as one.

A table for entropy encoding the determined final intra prediction mode is determined according to whether the upper and left intra prediction modes are the same.

7 is a block diagram showing an intra predictor 250 of the decoding apparatus 200 according to the present invention.

The intraprediction unit 250 according to the present invention includes a prediction mode decoding unit 251, a reference pixel generation unit 252, a reference pixel filtering unit 253, a prediction block generation unit 254, a prediction block filtering unit 255, And a prediction block transmitter 256. [

The prediction mode decoding unit 251 restores the intra prediction mode of the current prediction unit through the following process.

And additional information for generating a prediction block included in the additional information container in the received encoding unit. The additional information includes a predictable flag and residual prediction mode information. The predictable flag indicates whether or not it is the same as any one of the intra prediction modes of the adjacent prediction units of the current prediction unit. The remaining prediction mode information includes other information according to the predictable flag. If the predictable flag value is 1, the residual prediction mode information may include the prediction mode candidate index. The prediction mode candidate index is information for designating an intra prediction mode candidate. If the predictable flag value is 0, the residual prediction mode information includes the residual intra prediction mode number.

And derives the intra prediction mode candidate of the current prediction unit. The intra prediction mode candidate derives an intra prediction mode of an adjacent prediction unit. For convenience, the intra prediction mode candidate of the current prediction unit is limited to the upper and left intra prediction modes. When there are a plurality of upper or left prediction units of the current prediction unit, the upper and left intra prediction modes of the current prediction unit are derived in the same manner as the prediction mode coding unit 156 of the coding apparatus 100 described above. If the upper or left intra prediction mode is equal to or greater than the number of intra prediction modes allowed in the current prediction unit, the prediction mode encoding unit 156 performs the same conversion.

Next, if it is determined that the received predictive flag is the same as the intra prediction mode of the adjacent prediction unit, if the prediction mode candidate index exists, the prediction mode indicated by the prediction mode candidate index is determined as the intra prediction mode of the current prediction unit do.

If the prediction mode candidate index does not exist and the effective intra prediction mode of the adjacent prediction unit is 1, it indicates that the intra prediction mode of the current prediction unit is the same as the intra prediction mode of the current prediction unit, Mode.

Prediction mode of the current prediction unit by comparing the received residual intra-prediction mode value with the intra prediction mode number of the valid intra prediction mode candidates, if the received predictive flag indicates that the intra prediction mode is not the same as the intra prediction mode of the adjacent prediction unit Restore.

The reference pixel generating unit 252 generates reference pixels in the same manner as the reference pixel generating unit 151 of the encoding apparatus 100. The reference pixel generating unit 252 generates a reference pixel adaptively according to the intra prediction mode reconstructed by the prediction mode decoding unit 251, different. That is, the reference pixel generation unit 252 generates a reference pixel only when reference pixels to be used for generating a prediction block using the restored intra prediction mode are not valid.

The reference pixel filtering unit 253 adaptively filters the reference pixels based on the intra prediction mode reconstructed by the prediction mode decoding unit 251 and the size information of the current prediction unit. The filtering conditions and the filter are the same as the filtering condition and filter of the reference pixel filtering unit 152 of the encoding apparatus 100.

The prediction block generation unit 254 A prediction block is generated using the reference pixels according to the intra prediction mode restored by the prediction mode decoding unit 251. [ ,

The prediction block filtering unit 255 adaptively filters according to the intra prediction mode restored by the prediction mode decoding unit 251. The operation is the same as that of the prediction block filtering unit 154 of the encoding apparatus 100.

The prediction block transmission unit 256 transmits the prediction block received from the prediction mode generation unit 254 or the prediction block filtering unit 255 to the adder 290.

510:
520: prediction performing unit

Claims (10)

An apparatus for generating a prediction block of a moving picture decoding apparatus,
A prediction mode decoding unit for determining an intra prediction mode of a current prediction unit by using additional information for generating a prediction block included in the received additional information container and effective intra prediction mode candidate information of the current prediction unit;
A reference pixel generator for generating reference pixels of a position not available for generating an intra prediction block using available reference pixels;
A reference pixel filtering unit adaptively filtering a reference pixel adjacent to a current prediction unit based on the determined intra prediction mode of the current prediction unit or size information of the current prediction unit;
And a prediction block generator for generating a prediction block of a current prediction unit using reference pixels corresponding to the determined intra prediction mode of the current prediction unit. The apparatus of claim 1, further comprising a prediction block filtering unit for filtering a part of pixels in a prediction block generated by the prediction block generation unit based on the determined intra prediction mode of the current prediction unit,
Wherein a position of some pixels in the prediction block is determined by the intra prediction mode. 2. The apparatus of claim 1, wherein the reference pixel generation unit generates a reference pixel that is not usable by using the nearest usable pixel when there are available pixels in only one direction. The apparatus of claim 1, wherein the reference pixel filtering unit performs adaptive filtering according to a size of a current prediction unit. 2. The apparatus of claim 1, wherein the reference pixel filtering unit filters the reference pixels using a [1, 2, 1] filter. 2. The apparatus of claim 1, wherein the reference pixel filtering unit does not perform filtering on prediction units of a predetermined size or larger. 2. The apparatus of claim 1, wherein the reference pixel filtering unit does not filter the reference pixels in intra-prediction mode applying a single reference pixel used for generating each pixel in the prediction block. The apparatus of claim 1, wherein the reference pixel filtering unit does not filter the reference pixels in the planar mode. 3. The apparatus of claim 2, wherein the prediction block filtering unit generates the prediction block using only one of the reference pixels on either the left side or the upper side, generates the prediction block having the direction that is inclined by 45 degrees with respect to the horizontal or vertical direction, And for filtering some pixels in the prediction block. 2. The apparatus of claim 1, wherein the prediction block filtering unit filters the reference pixels in an intra prediction mode having a mode inclined by 45 占 with respect to the horizontal or vertical direction.

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