KR20180086093A - Method and apparatus for encoding or decoding video signal - Google Patents

Abstract

The present invention provides a method for generating a reference sample for intra prediction for encoding and decoding a high resolution image close to an original image, and a video signal encoding and decoding device performing the same. According to an embodiment of the present invention, the decoding method comprises the following steps: obtaining at least one of a maximum sample value and a minimum sample value from a bit stream; determining whether the reference sample included in a reference sample region located around a current block is usable; and generating the reference sample by using at least one of the maximum sample value and the minimum sample value, when the reference sample is unusable.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for encoding or decoding a video signal,

The present invention relates to a method and apparatus for encoding or decoding a video signal, and more particularly, to a method and apparatus for generating a reference sample of a reference sample region that is not available among peripheral reference samples of a current block.

Recently, the demand for high resolution and high quality images such as high definition (HD) image and ultra high definition (UHD) image is increasing in various applications. Since the amount of data increases relative to the conventional image data as the image data becomes high resolution and high quality, when the image data is transmitted using a medium such as a wired / wireless broadband line or stored using an existing storage medium, The cost and the storage cost increase. High-efficiency image compression techniques can be utilized to solve such problems as image data is high-resolution and high-quality.

It is possible to use a method of predicting information of neighboring blocks of the current block without transferring the information of the current block as it is with an image compression technique. An intra prediction technique for predicting a value of a current picture, and an intra prediction technique for predicting a sample value included in a current picture using pixel information in a current picture. There are various techniques such as an entropy encoding technique for assigning a short code to a value having a high appearance frequency and a long code to a value having a low appearance frequency. The image data is effectively compressed and transmitted or stored .

In the inter prediction method, a sample value of a current picture is predicted by referring to information of another picture. In intra prediction, intra-pixel correlation is used in the same picture Estimate the sample value. That is, in the case of performing intra prediction, the reference picture is not referenced in order to encode the current block, but the sample value of the reference samples located spatially adjacent to the current block to be encoded Intra prediction can be performed by determining the intra prediction mode.

Samples located in the reference sample region include both available samples and unavailable samples for intra prediction. If the reference sample is not available, it is used for intra-picture prediction after copying and using a sample value of surrounding available samples or assigning a predetermined sample value. However, these methods cause a problem of degrading intra prediction encoding efficiency.

SUMMARY OF THE INVENTION The present invention provides a method of generating a reference sample for intra-frame prediction for encoding and decoding a high-resolution image close to an original image, and an apparatus for encoding and decoding a video signal to perform the same.

Another object of the present invention is to provide a method and apparatus for encoding and decoding a video signal for increasing the encoding and decoding efficiency of an image.

According to an aspect of the present invention, there is provided a method of decoding a video signal, the method comprising: obtaining at least one of a maximum and a minimum sample value from a bitstream; Determining whether a reference sample located around the current block is available; And generating the reference sample using one or more of the maximum and minimum sample values if the reference sample is not available.

The maximum and minimum sample values may be maximum and minimum sample values in a picture or slice including the current block, and the reference sample area may include upper blocks, corner blocks, and left blocks of the current block.

In one embodiment, generating the reference sample may utilize an intermediate value or an average value of the maximum and minimum sample values.

According to another aspect of the present invention, there is provided a method of decoding a video signal, the method comprising: determining whether a reference sample included in a reference sample region located around a current block is available; And generating the unusable reference sample using reference samples available for at least two of the reference sample regions if the reference sample is not available.

In one embodiment, generating the reference sample comprises: obtaining at least one of an offset value, a slope value, a difference value, and a filter coefficient from the available reference samples; And generating the unusable reference sample using at least one of the offset value, the slope value, the difference value, and the filter coefficient.

The available reference samples may be reference samples that are adjacent to each other, and the available reference samples may be reference samples that are not adjacent to each other.

In addition, the step of generating the unavailable reference samples may be generated using at least one of a distance between the available reference samples and a distance of the available reference sample and the unavailable reference sample. have.

According to another aspect of the present invention, there is provided an apparatus for decoding a video signal, the apparatus comprising: a reference sample determining unit configured to determine whether a reference sample included in a reference sample region located in the vicinity of a current block is available; A determination unit; And a reference sample generator for generating the unusable reference samples using the reference samples available for at least two of the reference sample regions if the reference sample is not available.

In one embodiment, the reference sample generator obtains at least one of an offset value, a slope value, a difference value, and a filter coefficient from the available reference samples, and calculates the offset value, the slope value, And the coefficient may be used to generate the unavailable reference sample.

The available reference samples may be reference samples that are adjacent to each other, or one or more reference samples that are not adjacent to each other.

According to the embodiment of the present invention, when the reference sample of the current block is not available, the reference sample is generated using at least one of the maximum and minimum sample values obtained from the bit stream, thereby improving the coding and decoding efficiency of the image And to provide a method and apparatus for decoding a video signal.

Further, according to another embodiment of the present invention, by using two or more available reference samples of the reference sample region located around the current block to generate the unavailable reference samples of the reference sample region, And a method and an apparatus for decoding a video signal capable of encoding and decoding a high-resolution image closer to the original image.

1 is a block diagram schematically illustrating a video encoding apparatus according to an embodiment of the present invention.
2 is a block diagram schematically showing a video decoding apparatus according to an embodiment of the present invention.
3 is a schematic diagram for explaining a reference sample region of a current block according to an embodiment of the present invention.
Figures 4A-6A illustrate methods for generating reference samples for regions of the conventional reference sample regions that are not available.
6B and 7 are schematic diagrams illustrating a method of generating a reference sample for an unavailable region of a reference sample region of a current block according to an embodiment of the present invention.
FIG. 8 is a syntax diagram illustrating a method for generating a reference sample of an unavailable region according to an embodiment of the present invention, with reference to FIG. 6B.
Figures 9-12 are schematic diagrams illustrating methods for generating reference samples for unavailable regions of a reference sample region of a current block in accordance with various embodiments of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In the drawings, the thickness and the size of each unit are exaggerated for convenience and clarity of description, and the same reference numerals denote the same elements in the drawings. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Although the terms first, second, etc. are used herein to describe various elements, members, parts, regions, and / or sections, these elements, members, parts, It should be understood that the present invention should not be construed as being limited thereto. These terms are only used to distinguish one element, element, component, region, or portion from another region or portion. Thus, a first component, element, component, region, or section described below may refer to a second component, element, component, region, or portion without departing from the teachings of the present invention. Furthermore, and / or terms include any combination of the plurality of related described items or any of the plurality of related items described.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it is understood that the element is not directly connected or connected to the other element, And < / RTI > the case where other components are present. However, when an element is referred to as being "directly connected" or "directly connected" to another element, there is no other element in between and the element and the other element are directly connected or connected It should be understood that

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the drawings, for example, the size and shape of the members may be exaggerated for convenience and clarity of explanation, and in actual implementation, variations of the illustrated shape may be expected. Accordingly, embodiments of the present invention should not be construed as limited to any particular shape of the regions shown herein.

1 is a block diagram schematically showing an image encoding apparatus according to an embodiment of the present invention.

1, the image encoding apparatus 100 includes a picture dividing unit 105, an inter-picture predicting unit 110, an intra-picture predicting unit 115, a transform unit 120, a quantization unit 125, An entropy encoding unit 135, an inverse quantization unit 140, an inverse transformation unit 145, a filter unit 150, and a memory 155.

Each component shown in FIG. 1 is shown independently to represent different characteristic functions in the image encoding apparatus, and does not mean that each component is composed of separate hardware or one software constituent unit. That is, each component is listed as a separate component for convenience of explanation. At least two components of each component are combined to form one component, or one component is divided into a plurality of components, Can be performed. It is to be understood that the embodiments in which each of these components is integrated or the separate embodiments can be included in the scope of the present invention without departing from the essential aspect of the present invention.

The picture dividing unit 105 can divide the inputted picture into at least one processing unit. The processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU). ). However, for the sake of convenience of explanation, the prediction unit may be expressed as a prediction block, the conversion unit may be referred to as a conversion block, and the encoding or decoding unit may be expressed as a coding block or a decoding block.

In one embodiment, the picture dividing unit 105 divides a picture into a plurality of coding units, a prediction unit, and a conversion unit, and generates one (e.g., A picture can be encoded by selecting a combination of an encoding unit, a prediction unit, and a conversion unit.

For example, one picture may be divided into a plurality of coding units. In one embodiment, a picture may be divided into a plurality of units using a recursive tree structure such as a quad tree structure or a binary tree structure, and one picture or a maximum coding unit unit) as the root and the other encoding unit is divided into the number of child nodes corresponding to the number of the divided encoding units. Through this process, the encoding unit which is not further divided can be a leaf node. For example, in a case where it is assumed that only one square division is possible for one coding unit, one coding unit can be divided into a maximum of four coding units. However, in the present invention, the coding unit, the prediction unit, and / or the conversion unit are not limited to the symmetric division at the time of division. Asymmetric division is also possible, and not only four division but also two division are possible. The present invention is not limited thereto.

The prediction unit may be one which has been divided into at least one square or rectangular shape of the same size in one coding unit, and one of the prediction units in the one coding unit may be divided into another prediction And may have a shape and size different from the unit.

The predicting unit may include an inter-picture predicting unit 110 for performing inter-prediction and an intra-picture predicting unit 115 for performing intra-prediction. In order to improve the coding efficiency, instead of encoding the video signal as it is, the video is predicted using a specific area in the already coded and decoded picture, and the residual value between the original video and the predicted video is encoded. In addition, the prediction mode information and the motion vector information used for the prediction may be encoded by the entropy encoding unit 135 together with the residual value, and then transmitted to the decoding unit. When a particular encoding mode is used, it is also possible that the original block is encoded as it is without generating a prediction block through the predicting units 110 and 115, and is transmitted to the decoding unit.

In one embodiment, the predicting units 110 and 115 determine whether to perform intra-picture prediction or intra-picture prediction with respect to a prediction unit, and determine whether to perform intra-picture prediction using the inter-picture prediction mode, the motion vector, Specific information according to each method can be determined. In this case, the processing unit in which the prediction is performed, the prediction method, and the detail processing unit may be different from each other. For example, even if the prediction mode and the prediction method are determined according to the prediction unit, the prediction can be performed according to the conversion unit.

The predicting units 110 and 115 can predict a processing unit of a divided picture in the picture dividing unit 105 to generate a prediction block composed of predicted samples. The picture processing unit in the predicting units 110 and 115 may be a coding unit, a conversion unit, or a prediction unit.

The inter-picture predicting unit 110 can predict a prediction unit based on information of at least one of a previous picture or a following picture of the current picture, and predicts a prediction unit based on information of a partial area of the current picture, Unit can be predicted. The inter-picture predicting unit 110 may include a reference picture interpolating unit, a motion predicting unit, and a motion compensating unit.

In one embodiment, the information of the at least one picture used for prediction in the inter picture prediction unit 110 may be information of already coded and decoded pictures, have. For example, the picture modified and stored by any of the above methods may be a picture enlarged or reduced in a picture in which encoding and decoding has been performed, or may be a picture in which the brightness of all pixel values in a picture is changed, It is possible.

The reference picture interpolator can generate the pixel information of integer pixels or less from the reference picture by receiving the reference picture information from the memory 155. [ In the case of luminance pixels, it is possible to generate pixel information of less than or equal to a whole number in units of a quarter pixel by using a DCT-based 8-tap interpolation filter having different coefficients of the filter. In the case of a color difference signal, pixel information less than or equal to a certain integer can be generated in units of 1/8 pixel by using a DCT-based 4-tap interpolation filter having different coefficients of a filter. However, the unit for generating the pixel information of the type and the integer of the filter is not limited to this, and a unit for generating pixel information below the integer using various interpolation filters may be determined.

The motion prediction unit may perform motion prediction based on the reference pictures interpolated by the reference picture interpolation unit. Various methods can be used to calculate the motion vector. The motion vector may have an integer pixel unit or a motion vector value of 1/4 or 1/8 pixel unit based on the interpolated pixel. In one embodiment, a prediction unit of the current block can be predicted by differentiating the motion prediction method in the motion prediction unit. The motion prediction method may include a merge method, an AMVP (Advanced Motion Vector Prediction) method, and a skip method. In this way, the information including the index of the reference picture selected in the inter-picture prediction unit 110, the motion vector predictor (MVP), and the residual signal can be entropy-coded and transmitted to the decoder.

Unlike the inter-picture prediction, the intra-frame prediction unit 115 can generate a prediction unit based on reference pixel information around the current block, which is pixel information in the current picture. In the case where the neighboring blocks of the predictive unit are the blocks on which the inter-view prediction is performed, that is, the reference pixels are the pixels performing the inter-view prediction, the reference pixels included in the block in which the inter- May be replaced with the reference pixel information of the block.

If the reference pixel is unavailable, it must be set up to be available. Generally, in such a case, the non-available reference pixel has been used by replacing at least one reference pixel among available peripheral pixels or assigning a predetermined sample value.

However, a method of copying and using reference pixels available for such unavailable reference pixels may cause a problem of degrading the intra-picture prediction coding efficiency in decoding the current image. According to various embodiments of the present invention, in order to solve this problem, reference pixels that are not available by using at least two or more reference pixels available in the reference sample area, Method. A detailed description thereof will be described later. In addition, the intra prediction unit 115 may use the most probable intra prediction mode (MPM) obtained from the neighboring blocks to encode the intra prediction mode.

Even when the intra-frame prediction unit 115 performs intra-frame prediction, the processing unit in which the prediction is performed, the prediction method, and the processing unit in which the concrete contents are determined may be different from each other. For example, the prediction mode may be defined as a prediction unit (PU), the prediction may be performed in the prediction unit, the prediction mode may be defined as a prediction unit, and the prediction may be performed in a conversion unit (TU).

The prediction mode of the intra prediction can include 65 directional prediction modes and at least two non-directional modes. The non-directional mode may include a DC prediction mode and a planar mode. The number of the 67 inter picture prediction modes is only an example, and the present invention is not limited thereto, and intra prediction can be performed in more directional or non-directional modes to predict in various ways.

In one embodiment, intra prediction may generate a prediction block after applying a filter to a reference pixel. In this case, whether to apply the filter to the reference pixel can be determined according to the intra-picture prediction mode and / or size of the current block.

The prediction unit (PU) can be determined in various sizes and forms from a coding unit (CU) which is no longer divided. For example, in case of inter-picture prediction, the prediction unit may have the same size as 2N x 2N, 2N x N, N x 2N or N x N. In case of the intra prediction, the prediction unit may have the same size as 2N x 2N or N x N (N is an integer), but the intra prediction can be performed not only in the forward direction but also in the non-directional size. In this case, the N x N size prediction unit may be set to be applied only in a specific case. An intra prediction unit having the same size as N x mN, mN x N, 2N x mN or mN x 2N (m is a fraction or an integer) may be further defined and used in addition to the prediction unit of the above-described size.

A residual value (a residual block or a residual signal) between the prediction block and the original block generated by the intra prediction unit 115 may be input to the transform unit 120. [ In addition, the prediction mode information, the interpolation filter information, and the like used for prediction can be encoded by the entropy encoding unit 135 together with the residual value and transmitted to the decoder.

The transforming unit 120 transforms the residual block including the residual value information of the prediction unit generated through the original block and the prediction units 110 and 115 into a DCT (Discrete Cosine Transform), a DST (Discrete Sine Transform) , And KLT (Karhunen Loeve Transform). Whether the DCT, DST, or KLT is applied to transform the residual block can be determined based on the intra prediction mode information of the prediction unit used to generate the residual block.

The conversion unit in the conversion unit 120 may be a TU and may have a quad tree structure. In one embodiment, the size of the conversion unit may be determined within a range of predetermined maximum and minimum sizes.

The quantization unit 125 may quantize the residual values transformed by the transform unit 120 to generate a quantization coefficient. In one embodiment, the transformed residual values may be a frequency domain transformed value. The quantization coefficient may be changed according to the conversion unit or the importance of the image and the value calculated by the quantization unit 125 may be provided to the dequantization unit 140 and the rearrangement unit 130.

The reordering unit 130 may rearrange the quantization coefficients provided from the quantization unit 125. [ The reordering unit 130 can improve the coding efficiency in the entropy encoding unit 135 by rearranging the quantization coefficients. The reordering unit 130 may rearrange the quantization coefficients of the two-dimensional block form into a one-dimensional vector form through a coefficient scanning method. In the coefficient scanning method, it may be determined which scanning method is used according to the size of the conversion unit and the intra prediction mode. The coefficient scanning method may include a jig-jag scan, a vertical scan that scans a coefficient of a two-dimensional block form in a column direction, and a horizontal scan that scans a block form coefficient of a two-dimensional row in a row direction. In one embodiment, the reordering unit 130 may increase the entropy encoding efficiency in the entropy encoding unit 135 by changing the order of the coefficient scanning based on the probabilistic statistics of the coefficients transmitted from the quantization unit.

The entropy encoding unit 135 may perform entropy encoding on the rearranged quantization coefficients by the rearrangement unit 130. For entropy encoding, various encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Content-Adaptive Binary Arithmetic Coding (CABAC) may be used.

The entropy encoding unit 135 quantizes the quantization coefficient information, block type information, prediction mode information, division unit information, prediction unit information, and transmission unit information of the coding unit received from the reordering unit 130 and the prediction units 110 and 115, Various information such as motion vector information, reference picture information, interpolation information of a block, and filtering information can be encoded. Further, in one embodiment, the entropy encoding unit 135 may apply a certain change to the parameter set or syntax to be transmitted, if necessary.

The inverse quantization unit 140 dequantizes the quantized values in the quantization unit 125 and the inverse transformation unit 145 inversely changes the dequantized values in the inverse quantization unit 140. [ The residual values generated by the inverse quantization unit 140 and the inverse transform unit 145 may be combined with prediction blocks predicted by the prediction units 110 and 115 to generate a reconstructed block. The reconstructed block may be a motion compensated image or an MC image (Motion Compensated Picture).

The motion compensation image may be input to the filter unit 150. The filter unit 150 may include a deblocking filter unit, a sample adaptive offset (SAO), and an adaptive loop filter (ALF). In summary, A deblocking filter is applied in the filter section to reduce or eliminate blocking artifacts, and then input to the offset correction section to correct the offset. The picture output from the offset correcting unit is input to the adaptive loop filter unit, passes through an ALF (Adaptive Loop Filter) filter, and the picture passed through the filter can be transmitted to the memory 155.

To describe the filter unit 150 in detail, the deblocking filter unit can remove distortion in a block generated at a boundary between blocks in a reconstructed picture. In order to determine whether deblocking is to be performed, it may be determined whether to apply a deblocking filter to a current block based on pixels included in a few columns or rows included in the block. When a deblocking filter is applied to a block, a strong filter or a weak filter may be applied according to the required deblocking filtering strength. In applying the deblocking filter, horizontal filtering and vertical filtering may be performed concurrently in performing vertical filtering and horizontal filtering.

The offset correcting unit may correct the offset from the original image in units of pixels for the residual block to which the deblocking filter is applied. In order to correct an offset for a specific picture, a method of dividing a pixel included in an image into a predetermined number of regions, determining an area to be subjected to the offset, and applying an offset to the area (Band Offset) (Edge Offset) in which information is taken into consideration. However, in one embodiment, the filtering unit 150 may not apply the filtering to the reconstruction block used in inter-view prediction.

The adaptive loop filter (ALF) can be performed only when high efficiency is applied based on a value obtained by comparing the filtered reconstructed image with the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the group may be determined and different filtering may be performed for each group. Information related to whether or not to apply the ALF may be transmitted for each coding unit (CU), and the shape and filter coefficient of an ALF filter to be applied may be different according to each block. In addition, an ALF filter of the same type (fixed form) may be applied regardless of the characteristics of the application target block.

The memory 155 may store restored blocks or pictures calculated through the filter unit 150. [ The restored block or the picture stored in the memory 155 may be provided to the inter-picture predicting unit 110 or the intra-picture predicting unit 115 for performing inter-picture prediction. The pixel values of the reconstruction blocks used in the intra prediction unit 115 may be data to which the deblocking filter unit, the offset correction unit, and the adaptive loop filter unit are not applied.

2 is a block diagram schematically showing an image decoding apparatus according to an embodiment of the present invention. 2, the image decoding apparatus 200 includes an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, an inter-picture prediction unit 230, A filter unit 240, and a memory 245. The memory unit 245 includes a memory unit 235, a filter unit 240,

When an image bitstream is input from the image encoding apparatus, the input bitstream can be decoded in an inverse process of a process in which image information is processed in the encoding apparatus. For example, when variable length coding (VLC), such as CAVLC, is used to perform entropy coding in an image coding apparatus, the entropy decoding unit 210 is also used in an encoding apparatus It is possible to implement entropy decoding by implementing the same VLC table as the used VLC table. When CABAC is used to perform entropy encoding in the encoding apparatus, the entropy decoding unit 210 can perform entropy decoding using CABAC in correspondence thereto.

The entropy decoding unit 210 provides the information for generating a prediction block among the decoded information to the inter-picture predicting unit 230 and the intra-picture predicting unit 235. The entropy decoding unit 210 calculates residual values of entropy- May be input to the reordering unit 215. [

The reordering unit 215 may rearrange the entropy-decoded bitstream in the entropy decoding unit 210 based on a method of rearranging the entropy-decoded bitstream in the image encoder. The reordering unit 215 can perform reordering by providing information related to the coefficient scanning performed by the encoder and performing a reverse scanning based on the scanning order performed by the encoder.

The inverse quantization unit 220 may perform inverse quantization based on the quantization parameters provided by the encoding apparatus and the coefficient values of the re-arranged blocks. The inverse transform unit 225 may perform inverse DCT, inverse DST, or inverse KLT on the DCT, DST, or KLT performed by the transform unit of the encoding apparatus, on the quantization result performed by the image encoding apparatus. The inverse transform can be performed based on the transmission unit determined by the encoding apparatus or the division unit of the image. The transforming unit of the encoding apparatus can selectively perform DCT, DST, or KLT according to the prediction method, information such as the size and prediction direction of the current block, and the inverse transform unit 225 of the decoding apparatus transforms The inverse transform method is determined based on the transformed information to perform inverse transform.

The prediction units 230 and 235 may generate a prediction block based on the information related to the prediction block generation provided by the entropy decoding unit 210 and the previously decoded block and / or picture information provided in the memory 245. The reconstruction block may be generated using the prediction block generated by the prediction units 230 and 235 and the residual block provided by the inverse transform unit 225. [ The concrete prediction method performed by the prediction units 230 and 235 may be the same as the prediction method performed by the prediction units 110 and 115 of the encoding apparatus.

The prediction units 230 and 235 may include a prediction unit determination unit (not shown), an inter picture prediction unit 230, and an intra prediction unit 235. The prediction unit determination unit receives various information such as prediction unit information input from the entropy decoding unit 210, prediction mode information of the intra prediction method, motion prediction related information of the inter picture prediction method, And it is possible to discriminate whether the prediction unit performs inter-picture prediction or intra-picture prediction.

The inter-picture predicting unit 230 predicts information included in at least one of a previous picture or a following picture of a current picture including a current prediction unit by using information necessary for inter-picture prediction of a current prediction unit provided by an image encoder The inter prediction may be performed on the current prediction unit.

Specifically, in the inter-picture prediction, a reference block having the same size as the current block is selected for a current block, and a prediction block for the current block can be generated. At this time, information of neighboring blocks of the current picture can be used to use the information of the reference picture. For example, a prediction block for a current block can be generated based on information of a neighboring block using a skip mode, a merge mode, and an AMVP (Advanced Motion Vector Prediction) method.

The prediction block can be generated in units of samples below integer, such as a half pixel sample unit and a quarter pixel sample unit. In this case, the motion vector may also be expressed in units of integer pixels or less. For example, it can be expressed in units of 1/4 pixel for luminance pixels and 1/8 pixels for chrominance pixels.

The motion information including the motion vector and the reference picture index necessary for inter-picture prediction of the current block can be derived corresponding to the skip flag and the merge flag received from the encoding device.

The intra prediction unit 235 can generate a prediction block based on the pixel information in the current picture. If the prediction unit is a prediction unit that performs intra prediction, the intra prediction can be performed based on the intra prediction mode information of the prediction unit provided by the image encoder. In the case where the neighboring blocks of the predictive unit are the blocks on which the inter-view prediction is performed, that is, the reference pixels are the pixels performing the inter-view prediction, the reference pixels included in the block in which the inter- May be replaced with the reference pixel information of the block.

If the reference pixel is unavailable, it must be set up to be available. In general, in such a case, the unavailable reference pixel has been used by replacing at least one reference pixel among available neighbor pixel values, or by assigning a predetermined sample value, 3 to 4C.

However, a method of copying and using reference pixels available for such unavailable reference pixels may cause a problem of degrading the intra-picture prediction coding efficiency in decoding the current image. According to various embodiments of the present invention, in order to solve this problem, reference pixels that are not available by using at least two or more reference pixels available in the reference sample area, Method. A detailed description thereof will be given later with reference to Figs. 5 to 12.

In addition, the intra prediction unit 235 may use the most probable intra prediction mode (MPM) obtained from the neighboring blocks to encode the intra prediction mode. In one embodiment, the most probable intra-picture prediction mode may use an intra-picture prediction mode of a spatial neighbor block of the current block.

In one embodiment, the processing unit in which the prediction is performed in the intra prediction unit 235, the prediction method, and the processing unit in which the concrete contents are determined may be different from each other. For example, the prediction mode may be determined as a prediction unit, the prediction may be performed in the prediction unit, the prediction mode may be determined in the prediction unit, and the intra prediction may be performed in the conversion unit.

The intra picture prediction unit 235 may include an AIS (Adaptive Intra Smoothing) filter unit, a reference pixel interpolation unit, and a DC filter unit. The AIS filter unit performs filtering on the reference pixels of the current block, and may determine whether to apply the filter according to the prediction mode of the current prediction unit. The AIS filtering can be performed on the reference pixels of the current block using the prediction mode of the prediction unit provided in the image encoder and the AIS filter information. If the prediction mode of the current block is a mode in which AIS filtering is not performed, the AIS filter unit may not be applied to the current block.

The reference pixel interpolator can interpolate a reference pixel to generate a reference pixel in a pixel unit less than an integer value when the prediction mode of the prediction unit is a prediction unit that performs intra-frame prediction based on a sample value obtained by interpolating a reference pixel have. If the prediction mode of the current prediction unit does not interpolate the reference pixel and generates a prediction block, the reference pixel may not be interpolated. The DC filter unit may generate a prediction block through filtering when the prediction mode of the current block is the DC mode.

The restored blocks and / or pictures may be provided to the filter unit 240. The filter unit 240 may include a deblocking filter unit, a sample adaptive offset, and / or an adaptive loop filter unit on the restored block and / or the picture. The deblocking filter unit may receive information indicating whether a deblocking filter is applied to a corresponding block or a picture from the image encoder and information indicating whether a strong or weak filter is applied when a deblocking filter is applied. The deblocking filter unit may receive the deblocking filter related information provided by the image encoder and may perform deblocking filtering on the corresponding block in the image decoder.

The offset correcting unit may perform offset correction on the reconstructed image based on the type and offset value information of the offset correction applied to the image at the time of encoding. The adaptive loop filter unit may be applied as a coding unit based on information such as information on whether the adaptive loop filter provided from the encoder is applied or coefficient information of the adaptive loop filter. The information associated with the adaptive loop filter may be provided in a specific parameter set.

The memory 245 stores the reconstructed picture or block, and can later use the reconstructed picture or reference block as a reference picture or reference block, and can provide the reconstructed picture to the output unit.

Although omitted herein for the sake of convenience, the bit stream input to the decoding apparatus may be input to the entropy decoding unit through a parsing step. In addition, the entropy decoding unit may perform the parsing process.

In this specification, coding may be interpreted as encoding or decoding in some cases, and information includes both values, parameters, coefficients, elements, flags, and the like. . ≪ / RTI > A 'slice', a 'frame', or the like refers to a unit of a picture in a specific time zone, and a 'picture' Is a unit constituting a part, and can be used in combination with a picture as needed.

'Pixel', 'pixel' or 'pel' represents the smallest unit of a single image. Also, as a term indicating the value of a specific pixel, 'sample' can be used. The sample may be divided into luminance (Luma) and chroma (chroma) components, but generally it can be used as a term including both of them. The chrominance component represents a difference between predetermined colors, and is generally composed of Cb and Cr.

A 'unit' refers to a specific unit of an image processing unit or an image, such as the encoding unit, the prediction unit, and the conversion unit described above. In some cases, terms such as 'block' or 'area' Can be used in combination with each other. The block may also be used as a term indicating a set of samples or transform coefficients consisting of M columns and N rows.

3 is a schematic diagram for explaining a reference sample region of a current block according to an embodiment of the present invention.

Referring to FIG. 3, the current block 10 may be a block of various shapes, such as a square or a non-square shape. This current block 10 may be in the form of a rectangle having a transverse length (A) X longitudinal length (B). When the size of the current block 10 is A X B, a reference sample region 20, 30, or 40 in which reference samples used for intra-prediction can be located around the current block 10 may be located.

The reference sample region may include an upper reference sample region 20, a corner reference sample region 30, and a left reference sample region 40 located on the upper side of the current block 10. In one embodiment, the lengths of the upper reference sample region 20 and the left reference sample region 40 may be equal to the sum of the horizontal length A and the vertical length B of the current block 10. Further, the upper reference sample region 20, the corner reference sample region 30, and the left reference sample region 40 include at least one or more pixels, and the pixels include not only available reference pixels, And may include unavailable pixels for prediction.

The reference sample region located in the vicinity of the current block 10 includes an available reference sample region (1) including available reference pixels (1) and an unavailable reference sample region (2) including unavailable regions can do. If a reference sample region that is not available in the reference sample region is included, reference samples in the available reference sample region should be generated using reference samples in the available reference sample region.

Figures 4A-6A are schematic diagrams illustrating a method of generating reference samples of reference sample regions that are not available. Referring to FIG. 4A, a reference sample region that is not available may be located to the right of the current block 10 among the upper reference sample regions. In this case, reference samples at the R position among the available reference sample areas can be copied to the right direction, which is a reference sample area that is not available, to generate reference samples. Referring to FIG. 4B, there may be a reference sample region that is not available on the lower side of the current block 10 among the left reference sample regions. In this case, a pixel located closest to the reference sample region, The reference sample at the R position, which is not available, may be copied to the unavailable reference sample area to generate reference samples.

Also, referring to FIG. 4C, a reference sample region that is not available may be formed between the available reference sample regions. In this case, the reference sample at the R position, which is one of the pixels closest to the reference sample region that is not available among the available reference sample regions, may be copied and used to the unusable reference sample region.

In this way, when a reference sample area which is not available among the reference sample areas of the current block 10 coexist with an available reference sample area, conventionally, one reference sample value of the available reference sample areas is copied and used A sample value of the reference sample region that is not possible was generated. However, since all the pixel values of the unavailable reference sample region are generated by copying from the specific reference sample of the available reference sample region, they all have the same sample value. Therefore, such a padding method can lower the coding efficiency of the intra prediction.

5, if the current block 20 is tangent to the boundary of a picture, slice or segment, there may not be any available reference sample in the reference sample area 35. [ That is, there is only a reference sample area that is not available in the reference sample area, and there are no available reference samples to generate reference samples in the unavailable reference sample area. In this case, the reference sample for intra-frame prediction can use the intermediate value according to the bit depth representing the sample value as a DC value as shown in Equation 1 below.

According to Equation (1), for example, when 8 bits are used to represent a sample value, the sample value of the reference samples that are not available in the reference sample region 35 of the current block 20 is a middle value 128, it is possible to generate reference samples for intra prediction. A conceptual diagram related to Equation (1) is shown in Fig. 6A. Since the reference sample generation method also sets the sample value of the reference sample for the intra-picture prediction of the current block 20 using the predetermined number of bits without considering the information related to the actual sample value of the current block 20, The coding efficiency of the prediction is deteriorated.

To address these problems, a description is given of a reference sample generation method that improves coding efficiency when there is no reference sample region available in the reference sample region of the current block and when the available reference sample region is at least partially present. do.

6B to 7 are schematic diagrams illustrating a method of generating a reference sample for an unavailable region of a reference sample region of a current block according to an embodiment of the present invention.

For example, if the current block is a picture, slice, or segment boundary block, there are no reference samples available in the reference sample area for intra prediction in the current block. In this case, as shown in Equations 1 and 6A, the number of bits allocated for sample value representation is generally used as a reference sample value of the upper side, the upper corner, and the left reference sample region of the current block, The value was used as the sample value of the reference sample.

However, in the present invention, when there is no reference sample available in the reference sample region of the current block, reference samples can be generated using the maximum and minimum pixel values associated with the current block. In one embodiment, if there is no reference sample available in the reference sample region, then not only is there no such reference available, but more than the number of available reference samples in the reference sample region Include the case where the number of non-reference samples is greater. For example, this may be the case where the current block is a block located at the boundary of a picture, slice, or segment. If there is no reference sample available in the reference sample area, there may be no decoded pixel around the current block.

As shown in FIG. 6B, if there is no reference sample available in the reference sample area, a maximum sample value and a minimum sample value of the picture or slice including the current block from the bitstream may be obtained. The maximum sample value and the minimum sample value may be values within the maximum and minimum value ranges that can be expressed by the number of bits allocated to represent the sample value of the current block shown in FIG. 6A. An intermediate value of the obtained maximum sample value and minimum sample value may be allocated to a reference sample region that is not available in the reference sample region to generate reference samples of the current block.

Therefore, the method of generating a reference sample according to an embodiment of the present invention is similar to the method of generating a reference sample using the number of bits for representing a conventional sample value, by using information having high relevance to the sample value of the current block So that a video close to the original video can be encoded. In one embodiment, the maximum and minimum sample values may be included in the bitstream in units of pictures or slices in which the current block is included, but the present invention is not limited to this, and the maximum and minimum samples Value or a block unit. In addition, the method of obtaining the maximum and minimum sample values is not limited to the present invention.

For example, referring to FIG. 7, a current block is a block located at the boundary of a picture, 230 can be obtained as a maximum sample value transmitted on a picture-by-picture basis, and 50 as a minimum sample value can be obtained. At this time, the reference sample value of the current block can be calculated and calculated as shown in Equation (2).

The intermediate value 140 calculated by Equation (2) can be set as the reference sample value of the reference sample area, and the reference samples can be used for in-picture prediction of the current block. This method of generating a reference sample can set a reference value that is relatively unrelated to a current block to a reference sample that is not available, and thus can improve the coding efficiency.

8 is a syntax showing a method of generating a reference sample using maximum and minimum sample values, i.e., pixel values, obtained from an upper parameter of a bitstream according to an embodiment of the present invention.

8, when the explicit_min_max_value_flag of the Sequence Parameter Set (SPS) is '1', the encoder signals the maximum sample value and the minimum sample value to the upper parameter and transmits it to the decoder. When the explicit_min_max_value_flag is '0' The maximum sample value and the minimum sample value are not transmitted to the decoder. In the decoder, if the explicit_min_max_value_flag is '1', the explicit_min_max_slice_flag is decoded in the slide header. When the value of the decoded explicit_min_max_slice_flag is '1', it decodes explicit_min_value [0] indicating the minimum sample value for the luminance signal and explicit_max_value [0] indicating the maximum pixel value. Also, explicit_min_max_slice_chroma_flag is decoded to determine whether to transmit the maximum and minimum sample values for the color difference signal. Here, when the value of the explicit_min_max_slice_chroma_flag is '1', the explicit_min_value [cIdx] and the explicit_max_value [cIdx] indicating the maximum and minimum pixel values of the color difference signal are decoded for each color difference signal. Conversely, when the value of the explicit_min_max_slice_chroma_flag is '0', the maximum and minimum sample values for the color difference signal are not decoded.

Figures 9-12 are schematic diagrams illustrating methods for generating reference samples for unavailable regions of a reference sample region of a current block in accordance with various embodiments of the present invention. In one embodiment, the reference sample region may comprise at least one or more non-available reference sample regions.

Referring to FIG. 9, a reference sample region used for intra-frame prediction of the current block 10 may be located adjacent to the upper side and the left side of the current block 10. The reference sample region includes an available reference sample region 50 where available reference samples are located and a reference sample region 55 where pixels are not available.

In one embodiment, for pixels located in the unusable reference sample region 55, padding is performed on a reference sample region that is not available using at least one reference sample of available reference sample regions can do. For example, an offset value, a filter coefficient, a slope value, or a pixel difference value is calculated from sample values of two or more reference samples adjacent to a reference sample area that is not available among the available reference sample areas, and padding is performed .

The number of available reference samples used to calculate the offset value, the filter coefficient, the slope value, or the pixel difference value is not limited. Also, the method of calculating the offset value, the filter coefficient, the slope value, or the pixel difference value is not limited to the present invention. In one embodiment, the number of available reference samples used to generate the reference samples of the reference sample region that are not available and their location are not limited to the present invention, and may include at least one available reference sample Can be used.

To generate a reference sample that is not available in the present invention, first determine whether each of the pixels of the reference sample region 50, 55 is available for intra-picture prediction. Thereafter, if some reference pixels are not available, at least one or more pixels of the available reference sample area may be used to generate a reference sample value that is not available. The various methods of generating the reference samples may vary depending on the position and the number of reference sample regions that are not available among the reference sample regions, and a detailed method will be described with reference to FIGS.

Referring to FIG. 10, at least two or more of the available reference samples A and B (71, 72) of the reference sample regions 70 available to generate the unavailable reference samples may be used. The available reference samples A and B (71, 72) may be reference samples that are adjacent to each other. For example, the available reference samples can be used to obtain the offset value [beta], and the offset value is used to generate reference samples 72, 73, ..., 7N of reference sample regions that are not available . The sample value of the reference samples of the unavailable reference sample area generated in this way can be calculated by the following equation (3).

The available reference samples may be three or more, and the offset values obtained therefrom may be the median or average value of three or more reference samples as well as the formula of equation (3). In addition, the available reference samples may be at least a pair of adjacent pixels, and may include at least three adjacent pixels. In one embodiment, the available reference samples may be pixels at a location closest to the reference sample region that is not available, but the location of the available reference samples is not limited.

In addition, the available reference samples used to generate the reference samples in the reference sample region that are not available may not be contiguous, as shown in FIGS. 11 and 12. Referring to FIG. 11, the reference sample region of the current block may include at least two or more available reference samples A and B (81, 82), wherein the reference samples A and B are spaced apart from each other Lt; / RTI >

The method of generating a reference sample according to an embodiment of the present invention may use the available reference samples A and B (81, 82) to generate reference samples of unavailable regions. For example, as shown in Equation (4) below, the available reference samples A and B and the distance of the reference samples can be used to calculate the offset value beta. The offset values calculated in this way are used to generate reference samples (83, 84, ..., 8N) of the unusable region in addition to the available reference sample value (B) can do.

S is the distance between the reference samples A and B, Ro is the sample value of the least available reference sample that is closest to the available reference samples, and Rk is the reference sample of the unavailable reference sample area .

In one embodiment, the unavailable reference samples may be more than three and the offset values obtained therefrom may be the intermediate value or average value of three or more reference samples as well as the formula of equation (4). In addition, the available reference samples may be pixels that are not adjacent to each other, and their positions are not limited to the embodiments of the present invention.

Referring to FIG. 12, a method of generating a reference sample according to another embodiment of the present invention may use a weight obtained from two or more available reference samples that are not adjacent to each other.

The method of generating a reference sample according to an embodiment of the present invention may use the available reference samples A and B (91, 92) to generate reference samples of unavailable regions. First, using the sample values of the available reference samples A and B (91, 92) as shown in Equation (5), the weight values? ₁ and? ₂ Can be calculated first. The weight values? ₁ and? ₂ May be set differently for each unavailable reference sample Rk location between available reference samples. For example, assuming that the distance between the available reference samples A and B (91, 92) used for reference sample generation is D, the first weight? ₁ is denominator and D + 1 is the denominator It is possible to set a value obtained by subtracting the distance between the reference sample A and the reference sample Rk to be generated with a numerator. The second weight w ₂ can be set to a value having a numerator as the distance between the reference sample A and the reference sample R _k to be generated, with D + 1 as a denominator. It is possible to generate reference samples 93, 94, ..., 9N of the unavailable region using Equation (5) using the first weight and the second weight.

In one embodiment, the non-available reference samples may be more than three and the weight values obtained therefrom may be a value calculated from two reference samples out of three or more reference samples, . In addition, the available reference samples may be pixels that are not adjacent to each other, and their positions are not limited to the embodiments of the present invention.

As described above, the reference sample generation method according to an exemplary embodiment of the present invention uses at least two available reference samples of the reference sample region located in the periphery of the current block, A method and an apparatus for decoding a video signal capable of encoding and decoding a high-resolution image closer to an original image than an existing method.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be clear to those who have knowledge.

Claims (16)

Obtaining at least one of a maximum and a minimum sample value from the bitstream;
Determining whether a reference sample included in a reference sample region located around the current block is available; And
And generating the reference sample using at least one of the maximum and minimum sample values if the reference sample is not available. The method according to claim 1,
Wherein the maximum and minimum sample values are maximum and minimum sample values of a picture or slice including the current block. The method according to claim 1,
Wherein the reference sample region includes upper blocks, corner blocks, and left blocks of the current block. The method according to claim 1,
Wherein generating the reference sample comprises using an intermediate or mean value of the maximum and minimum sample values. Determining whether a reference sample included in a reference sample region located around the current block is available; And
Generating the unusable reference sample using reference samples available for at least two of the reference sample regions if the reference sample is not available. 6. The method of claim 5,
Wherein the step of generating the reference sample comprises:
Obtaining at least one of an offset value, a slope value, a difference value, and a filter coefficient from the available reference samples; And
And generating the unavailable reference sample using at least one of the offset value, the slope value, the difference value, and the filter coefficient. 6. The method of claim 5,
Wherein the available reference samples are reference samples that are adjacent to each other. 6. The method of claim 5,
Wherein the available reference samples are reference samples in which one or more are not adjacent to each other. 9. The method of claim 8,
Wherein generating the unavailable reference sample comprises:
Using the distance between the available reference samples and the distance of the available reference sample and the distance of the unavailable reference sample. An information obtaining unit obtaining at least one of maximum and minimum sample values from the bitstream;
Determining whether or not a reference sample included in a reference sample region located in the vicinity of the current block is available; And
And a reference sample generator for generating the reference sample using at least one of the maximum and minimum sample values if the reference sample is not available. 11. The method of claim 10,
Wherein the maximum and minimum sample values are maximum and minimum sample values of a picture or slice including the current block. 11. The method of claim 10,
Wherein the reference sample generator generates a reference sample using an intermediate value or an average value of the maximum and minimum sample values. A reference sample availability determining unit that determines whether or not a reference sample included in a reference sample area located in the vicinity of a current block is available; And
And a reference sample generator for generating the unavailable reference samples using the reference samples available for at least two of the reference sample regions if the reference sample is not available, . 14. The method of claim 13,
Wherein the reference sample generator comprises:
Obtaining at least one of an offset value, a slope value, a difference value, and a filter coefficient from the available reference samples and using the at least one of the offset value, the slope value, the difference value, And generates a reference sample that is not used. 14. The method of claim 13,
Wherein the available reference samples are reference samples that are adjacent to each other. 14. The method of claim 13,
Wherein the available reference samples are reference samples that are not adjacent to one another.

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