KR20140145560A - A method and an apparatus for encoding/decoding a scalable video signal - Google Patents

Abstract

A method for decoding a scalable video signal of the present invention includes the steps of: acquiring a filter coefficient of an up-sampling filter applied to a reference picture of a reference layer; creating an inter-layer reference picture by applying the acquired filter coefficient to the reference picture; and performing inter prediction with respect to a present block of a present layer based on the created inter-layer reference picture.

Description

[0001] METHOD AND APPARATUS FOR ENCODING / DECODING A SCALABLE VIDEO SIGNAL [0002]

The present invention relates to a scalable video signal encoding / decoding method and apparatus.

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. As the image data has high resolution and high quality, the amount of data increases relative to the existing image data. Therefore, when the image data is transmitted using a medium such as a wired / wireless broadband line or stored using an existing storage medium, The storage cost is increased. High-efficiency image compression techniques can be utilized to solve such problems as image data becomes high-resolution and high-quality.

An inter picture prediction technique for predicting a pixel value included in a current picture from a previous or a subsequent picture of a current picture by an image compression technique, an intra picture prediction technique for predicting a pixel value included in a current picture using pixel information in the current picture, There are various techniques such as an entropy encoding technique in which a short code is assigned to a value having a high appearance frequency and a long code is assigned to a value having a low appearance frequency. Image data can be effectively compressed and transmitted or stored using such an image compression technique.

On the other hand, demand for high-resolution images is increasing, and demand for stereoscopic image content as a new image service is also increasing. Video compression techniques are being discussed to effectively provide high resolution and ultra-high resolution stereoscopic content.

It is an object of the present invention to provide a method and apparatus for up-sampling a reference picture of a reference layer in encoding / decoding a scalable video signal.

An object of the present invention is to provide a method and apparatus for constructing a reference picture list using an interlayer reference picture in encoding / decoding a scalable video signal.

An object of the present invention is to provide a method and apparatus for effectively deriving texture information of a current layer through inter-layer prediction in encoding / decoding a scalable video signal.

A scalable video signal decoding method and apparatus according to the present invention is characterized by upsampling a reference picture of a reference layer by selectively using a fixed up-sampling filter and an adaptive up-sampling filter.

The scalable video signal decoding method and apparatus according to the present invention are characterized in that a fixed up-sampling filter and an adaptive up-sampling filter are selectively used for each of a luminance component and a chrominance component.

The method and apparatus for scalable video signal decoding according to the present invention are characterized in that a fixed up-sampling filter and an adaptive up-sampling filter are selectively used for each of a luminance component and chrominance components Cb and Cr.

The scalable video signal decoding method and apparatus according to the present invention are characterized in that a filter coefficient of an adaptive up-sampling filter is adaptively obtained for each phase of a reference sample.

A scalable video signal encoding method and apparatus according to the present invention is characterized by upsampling a reference picture of a reference layer by selectively using a fixed up-sampling filter and an adaptive up-sampling filter.

A scalable video signal encoding method and apparatus according to the present invention is characterized in that a fixed up-sampling filter and an adaptive up-sampling filter are selectively used for each of a luminance component and a chrominance component.

The scalable video signal encoding method and apparatus according to the present invention are characterized in that a fixed up-sampling filter and an adaptive up-sampling filter are selectively used for each of the luminance component and chrominance components Cb and Cr.

A scalable video signal encoding method and apparatus according to the present invention is characterized in that a filter coefficient of an adaptive up-sampling filter is adaptively obtained for each phase of a reference sample.

According to the present invention, by selectively using an adaptive up-sampling filter that reflects characteristics of an image, the reference picture of the reference layer can be effectively upsampled.

Further, according to the present invention, it is possible to effectively construct a reference picture list using an interlayer reference picture.

In addition, according to the present invention, texture information of a current layer can be effectively guided through inter-layer prediction.

1 is a block diagram schematically illustrating an encoding apparatus according to an embodiment of the present invention.
2 is a block diagram schematically illustrating a decoding apparatus according to an embodiment of the present invention.
3 is a flowchart illustrating a process of performing inter-layer prediction of a current layer using a reference picture of a reference layer according to an embodiment of the present invention.
FIG. 4 illustrates a method of selectively using an adaptive up-sampling filter for a reference picture according to an embodiment to which the present invention is applied.
FIG. 5 illustrates a method of selectively using an adaptive up-sampling filter for each of a luminance component and a chrominance component to which the present invention is applied.
FIG. 6 illustrates a method of selectively using an adaptive up-sampling filter for each of a luminance component and two chrominance components (Cb and Cr) to which the present invention is applied.
FIG. 7 illustrates a method of obtaining filter coefficients of an adaptive up-sampling filter based on a first adaptive component flag, according to an embodiment to which the present invention is applied.
Figure 8 illustrates a method of obtaining the filter coefficients of an adaptive up-sampling filter based on a second adaptive component flag, as an example of an application to which the present invention is applied.
FIG. 9 illustrates a method of adaptively acquiring filter coefficients for each phase of a reference sample according to an embodiment of the present invention. Referring to FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

When an element is referred to herein as being "connected" or "connected" to another element, it may mean directly connected or connected to the other element, Element may be present. In addition, the content of " including " a specific configuration in this specification does not exclude a configuration other than the configuration, and means that additional configurations can be included in the scope of the present invention or the scope of the present invention.

The terms first, second, etc. may be used to describe various configurations, but the configurations are not limited by the term. The terms are used for the purpose of distinguishing one configuration from another. For example, without departing from the scope of the present invention, the first configuration may be referred to as the second configuration, and similarly, the second configuration may be named as the first configuration.

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that the components are composed of separate hardware or software constituent units. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of each constituent unit may form one constituent unit or one constituent unit may be divided into a plurality of constituent units to perform a function. The integrated embodiments and the separate embodiments of each component are also included in the scope of the present invention unless they depart from the essence of the present invention.

In addition, some of the components are not essential components to perform essential functions in the present invention, but may be optional components only to improve performance. The present invention can be implemented only with components essential for realizing the essence of the present invention, except for the components used for the performance improvement, and can be implemented by only including the essential components except the optional components used for performance improvement Are also included in the scope of the present invention.

The coding and decoding of video supporting a plurality of layers (multi-layers) in a bitstream is referred to as scalable video coding. Since there is a strong correlation between a plurality of layers, it is possible to remove redundant elements of data and improve the coding performance of an image by performing prediction using such a relation. Hereinafter, prediction of the current layer using information of another layer is referred to as inter-layer prediction or inter-layer prediction.

The plurality of layers may have different resolutions, where the resolution may refer to at least one of spatial resolution, temporal resolution, and image quality. Resampling such as up-sampling or down-sampling of a layer may be performed to adjust the resolution in the inter-layer prediction.

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

The encoding apparatus 100 according to the present invention includes an encoding unit 100a for an upper layer and an encoding unit 100b for a lower layer.

The upper layer may be represented by a current layer or an enhancement layer and the lower layer may be represented by an enhancement layer, a base layer, or a reference layer having a resolution lower than that of the upper layer . The upper layer and the lower layer may have different spatial resolution, temporal resolution according to the frame rate, and image quality depending on the color format or the quantization size. Upsampling or downsampling of a layer may be performed when a resolution change is required to perform inter-layer prediction.

The encoding unit 100a of the upper layer includes a decomposing unit 110, a predicting unit 120, a transforming unit 130, a quantizing unit 140, a rearranging unit 150, an entropy encoding unit 160, 170, an inverse transform unit 180, a filter unit 190, and a memory 195.

The lower layer encoding unit 100b includes a partitioning unit 111, a predicting unit 125, a transforming unit 131, a quantizing unit 141, a reordering unit 151, an entropy coding unit 161, an inverse quantization unit 171, an inverse transform unit 181, a filter unit 191, and a memory 196.

The encoding unit may be implemented by the image encoding method described in the embodiments of the present invention, but operations in some components may not be performed for lowering the complexity of the encoding apparatus or for fast real-time encoding. For example, in performing intra-picture prediction in the prediction unit, it is not necessary to use a method of selecting an optimal intra-picture coding method using all the intra-picture prediction mode methods in order to perform coding in real time, The intra-picture prediction mode may be used as the final intra-picture prediction mode. As another example, it is also possible to restrictively use the type of the prediction block used in intra-picture prediction or inter-picture prediction.

The unit of the block processed by the encoding apparatus may be a coding unit for performing encoding, a prediction unit for performing prediction, and a conversion unit for performing conversion. The coding unit can be expressed by CU (Coding Unit), the prediction unit by PU (Prediction Unit), and the conversion unit by TU (Transform Unit).

In the division units 110 and 111, the layer image is divided into a plurality of encoding blocks, a prediction block, and a conversion block, and is divided into a coding block, a prediction block, Can be selected to divide the layer. For example, a recursive tree structure such as a quad tree structure can be used to divide an encoding unit in a layer image. Hereinafter, in the embodiment of the present invention, the meaning of a coding block may be used not only for a coding block but also for a block to perform decoding.

The prediction block may be a unit for performing prediction such as intra-picture prediction or inter-picture prediction. The block for intra prediction may be a square block such as 2Nx2N, NxN. As a block for performing inter picture prediction, there is a prediction block dividing method using AMP (Asymmetric Motion Partitioning), which is a square shape such as 2Nx2N or NxN or a rectangular shape or an asymmetric shape such as 2NxN and Nx2N. The method of performing the transform in the transform unit 115 may vary depending on the type of the prediction block.

The prediction units 120 and 125 of the encoding units 100a and 100b include intra prediction units 121 and 126 for performing intra prediction and inter prediction units for performing inter prediction, (122, 127). The predicting unit 120 of the upper layer encoding unit 100a may further include an inter-layer predicting unit 123 that performs prediction on an upper layer using information of a lower layer.

The prediction units 120 and 125 can determine whether to use inter-picture prediction or intra-picture prediction for the prediction block. The process of determining an intra prediction mode in units of prediction blocks in performing intra prediction and performing intra prediction on the basis of the determined intra prediction mode may be performed on a conversion block basis. The residual value (residual block) between the generated prediction block and the original block can be input to the conversion units 130 and 131. In addition, the prediction mode information, motion information, and the like used for prediction can be encoded by the entropy encoding unit 130 and transmitted to the decoding apparatus together with the residual value.

When the PCM (Pulse Coded Modulation) coding mode is used, it is also possible to directly encode the original block and transmit it to the decoding unit without performing the prediction through the prediction units 120 and 125.

Intra prediction units 121 and 126 can generate a predicted block on the basis of reference pixels existing in the vicinity of the current block (block to be predicted). In the intra prediction method, the intra prediction mode may have a directional prediction mode using the reference pixel according to the prediction direction and a non-directional mode not considering the prediction direction. The mode for predicting luma information and the mode for predicting chrominance information may be different types. In order to predict the color difference information, an intra prediction mode in which luma information is predicted or predicted luma information can be utilized. If the reference pixel is not available, replace the unavailable reference pixel with another pixel and use it to create a prediction block.

The prediction block may include a plurality of transform blocks. When intra prediction is performed, if the size of the prediction block and the size of the transform block are the same, a pixel existing on the left side of the prediction block, In-picture prediction for the prediction block based on the pixels existing in the prediction block. However, when intra prediction is performed, when the size of the prediction block is different from the size of the transform block, when a plurality of transform blocks are included in the prediction block, the intra-picture prediction is performed using the neighboring pixels adjacent to the transform block as reference pixels. Can be performed. Here, the neighboring pixels adjacent to the transform block may include at least one of neighboring pixels adjacent to the prediction block and pixels already decoded in the prediction block.

The intra-picture prediction method can generate a prediction block after applying a mode dependent intra-smoothing (MDIS) filter to the reference picture according to the intra-picture prediction mode. The type of MDIS filter applied to the reference pixel may be different. The MDIS filter can be used to reduce residuals in intra-frame predicted blocks generated after performing intra-prediction and applied to reference pixels and prediction as additional filters applied to intra-frame predicted blocks. In performing MDIS filtering, the filtering of the reference pixel and some columns included in the intra prediction block can perform filtering according to the direction of the intra prediction mode.

The inter-picture prediction units 122 and 127 can perform prediction by referring to information of a block included in at least one of a previous picture of a current picture or a following picture. The inter-picture prediction units 122 and 127 may include a reference picture interpolating unit, a motion predicting unit, and a motion compensating unit.

In the reference picture interpolating unit, the reference picture information is supplied from the memories 195 and 196, and pixel information of an integer pixel or less can be generated in the reference picture. In the case of luma pixels, a DCT-based interpolation filter (DCT) based on a different filter coefficient may be used to generate pixel information of an integer number of pixels or less in units of quarter pixels. In the case of a color difference signal, a DCT-based 4-tap interpolation filter having a different filter coefficient may be used to generate pixel information of an integer number of pixels or less in units of 1/8 pixel.

The inter-picture prediction units 122 and 127 can perform motion prediction based on the reference pictures interpolated by the reference picture interpolating unit. Various methods such as Full Search-based Block Matching Algorithm (FBMA), Three Step Search (TSS), and New Three-Step Search Algorithm (NTS) can be used to calculate motion vectors. The motion vector may have a motion vector value of 1/2 or 1/4 pixel unit based on the interpolated pixel. The inter-picture prediction units 122 and 127 can perform prediction on the current block by applying one inter-picture prediction method among various inter-picture prediction methods.

As the inter-picture prediction method, various methods such as a skip method, a merge method, and a method using a motion vector predictor (MVP) can be used.

In the inter-picture prediction, information such as motion information, such as reference indices, motion vectors, and residual signals, is entropy-encoded and transmitted to the decoding unit. When the skip mode is applied, a residual signal is not generated, so that the conversion and quantization process for the residual signal may be omitted.

The inter-layer predicting unit 123 performs inter-layer prediction for predicting an upper layer using information of the lower layer. The inter-layer predicting unit 123 may perform inter-layer prediction using texture information and motion information of a lower layer.

Inter-layer prediction can predict a current block of an upper layer using motion information on a picture of a lower layer (reference layer) using a picture of a lower layer as a reference picture. A picture of a reference layer used as a reference picture in inter-layer prediction may be a picture sampled according to the resolution of the current layer. In addition, the motion information may include a motion vector and a reference index. At this time, the value of the motion vector for the picture of the reference layer can be set to (0, 0).

As an example of inter-layer prediction, a prediction method of using a picture of a lower layer as a reference picture has been described, but the present invention is not limited to this. The inter-layer predicting unit 123 may perform inter-layer texture prediction, inter-layer motion prediction, inter-layer syntax prediction, inter-layer difference prediction, and the like.

Inter-layer texture prediction can derive the texture of the current layer based on the texture of the reference layer. The texture of the reference layer can be sampled according to the resolution of the current layer, and the inter-layer predicting unit 123 can predict the texture of the current layer based on the texture of the sampled reference layer.

The inter-layer motion prediction can derive the motion vector of the current layer based on the motion vector of the reference layer. At this time, the motion vector of the reference layer can be scaled according to the resolution of the current layer. In the inter-layer syntax prediction, the syntax of the current layer can be predicted based on the syntax of the reference layer. For example, the inter-layer predicting unit 123 may use the syntax of the reference layer as the syntax of the current layer. In the inter-layer difference prediction, the picture of the current layer can be restored by using the difference between the restored image of the reference layer and the restored image of the current layer.

A residual block including residue information which is a difference value between the prediction blocks generated by the prediction units 120 and 125 and the reconstruction blocks of the prediction blocks is generated and the residual blocks are input to the transform units 130 and 131. [

The transforming units 130 and 131 can transform the residual block using a transform method such as DCT (Discrete Cosine Transform) or DST (Discrete Sine Transform). Whether to apply the DCT or the DST to transform the residual block can be determined based on the intra prediction mode information and the prediction block size information of the prediction block used to generate the residual block. That is, the transforming units 130 and 131 can apply the transforming method differently according to the size of the prediction block and the prediction method.

The quantization units 140 and 141 may quantize the values converted into the frequency domain by the transform units 130 and 131. [ The quantization factor may vary depending on the block or the importance of the image. The values calculated by the quantization units 140 and 141 may be provided to the dequantization units 170 and 17 and the reordering units 150 and 151, respectively.

The reordering units 150 and 151 can reorder the coefficient values with respect to the quantized residual values. The reordering units 150 and 151 may change the two-dimensional block type coefficient to a one-dimensional vector form through a coefficient scanning method. For example, the rearrangement units 150 and 151 may scan a DC coefficient to a coefficient of a high frequency region using a Zig-Zag scan method, and change the DC coefficient to a one-dimensional vector form. A vertical scanning method of scanning a two-dimensional block type coefficient in a column direction instead of a jig-jag scanning method according to a size of a conversion block and an intra-picture prediction mode, and a horizontal scanning method of scanning a two- Can be used. That is, it is possible to determine whether any scan method among the jig-jag scan, the vertical scan and the horizontal scan is used according to the size of the conversion block and the intra prediction mode.

The entropy encoding units 160 and 161 can perform entropy encoding based on the values calculated by the reordering units 150 and 151. [ For entropy encoding, various encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be used.

The entropy encoding units 160 and 161 receive the residual value coefficient information, the block type information, the prediction mode information, the division unit information, the prediction block information, and the transmission information of the encoding block from the reordering units 150 and 151 and the prediction units 120 and 125, And various information such as unit information, motion information, reference frame information, block interpolation information, filtering information, and the like, and performs entropy encoding based on a predetermined encoding method. In addition, the entropy encoding units 160 and 161 can entropy-encode the coefficient values of the encoding units input from the reordering units 150 and 151.

The entropy encoding units 160 and 161 may encode the intra-picture prediction mode information of the current block by performing binarization on the intra-picture prediction mode information. The entropy encoding units 160 and 161 may include a codeword mapping unit for performing such a binarization operation, and binarization may be performed differently depending on the size of a prediction block for performing intra prediction. In the codeword mapping unit, a codeword mapping table may be adaptively generated or stored in advance through a binarization operation. In another embodiment, the entropy encoding units 160 and 161 may represent the current intra prediction mode information using a codeword mapping unit that performs codeword mapping and a codeword mapping unit that performs codeword mapping. In the codeword mapping unit and the codeword mapping unit, a codeword mapping table and a codeword mapping table may be generated or stored.

The inverse quantization units 170 and 171 and the inverse transform units 180 and 181 dequantize the quantized values in the quantization units 140 and 141 and invert the converted values in the transform units 130 and 131. The residual values generated by the inverse quantization units 170 and 171 and the inverse transform units 180 and 181 are estimated through a motion estimation unit, a motion compensation unit, and an intra prediction unit included in the prediction units 120 and 125, It can be combined with the prediction block to generate a reconstructed block.

The filter units 190 and 191 may include at least one of a deblocking filter and an offset correcting unit.

The deblocking filter can remove block distortion caused by the boundary between the blocks in the reconstructed picture. It may be determined whether to apply a deblocking filter to the current block based on pixels included in a few columns or rows included in the block to determine whether to perform deblocking. When a deblocking filter is applied to a block, a strong filter or a weak filter may be applied according to the deblocking filtering strength required. In applying the deblocking filter, horizontal filtering and vertical filtering may be performed concurrently when vertical filtering and horizontal filtering are performed.

The offset correction unit may correct the offset of the deblocked image with respect to the original image in units of pixels. In order to perform offset correction for a specific picture, pixels included in an image are divided into a predetermined area, and then an area to be offset is determined, and an offset is applied to the area, or an offset is applied considering edge information of each pixel Can be used.

The filter units 190 and 191 may apply only the deblocking filter without applying both the deblocking filter and the offset correction, or both the deblocking filter and the offset correction.

The memories 195 and 196 may store restored blocks or pictures calculated through the filter units 190 and 191 and the stored restored blocks or pictures may be provided to the predicting units 120 and 125 have.

The information output from the entropy encoding unit 100b of the lower layer and the information output from the entropy encoding unit 100a of the upper layer can be multiplexed by the MUX 197 and output as a bitstream.

The MUX 197 may be included in the encoding unit 100a of the upper layer or the encoding unit 100b of the lower layer or may be implemented as an independent device or module separate from the encoding unit 100. [

2 is a block diagram schematically illustrating a decoding apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the decoding apparatus 200 includes a decoding unit 200a of an upper layer and a decoding unit 200b of a lower layer.

The decryption unit 200a of the upper layer includes an entropy decoding unit 210, a reordering unit 220, an inverse quantization unit 230, an inverse transformation unit 240, a prediction unit 250, a filter unit 260, a memory 270 ).

The lower layer decoding unit 200b includes an entropy decoding unit 211, a rearrangement unit 221, an inverse quantization unit 231, an inverse transformation unit 241, a prediction unit 251, a filter unit 261, a memory 271 ).

When a bitstream including a plurality of layers is transmitted from the encoding apparatus, the DEMUX 280 demultiplexes information for each layer and transmits the demultiplexed information to the decoding units 200a and 200b for the respective layers. The input bitstream can be decoded in a procedure opposite to that of the encoding apparatus.

The entropy decoding units 210 and 211 may perform entropy decoding in a procedure opposite to that in which entropy encoding is performed in the entropy encoding unit of the encoding apparatus. The information for generating a prediction block from the information decoded by the entropy decoding units 210 and 211 is provided to the predictors 250 and 251 and the residual values obtained by performing entropy decoding in the entropy decoding units 210 and 211, (220, 221).

As with the entropy encoding units 160 and 161, the entropy decoding units 210 and 211 may use at least one of CABAC and CAVLC.

The entropy decoding units 210 and 211 can decode information related to the intra-picture prediction and the inter-picture prediction performed by the coding apparatus. The entropy decoding units 210 and 211 may include a codeword mapping table for generating a codeword including the codeword mapping unit in the in-picture prediction mode number. The codeword mapping table may be pre-stored or adaptively generated. When using the code-mapped mapping table, a code-mapped mapping unit for performing code-mapped mapping may additionally be provided.

The reordering units 220 and 221 can perform reordering based on a method in which the entropy decoding units 210 and 211 rearrange the entropy-decoded bitstreams in the encoding unit. The coefficients represented by the one-dimensional vector form can be rearranged by restoring the coefficients of the two-dimensional block form again. The reordering units 220 and 221 can perform reordering by providing information related to the coefficient scanning performed by the encoding unit and performing a reverse scanning based on the scanning order performed by the encoding unit.

The inverse quantization units 230 and 231 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 units 240 and 241 may perform inverse DCT or inverse DST on the DCT or DST performed by the transform units 130 and 131 with respect to the quantization result performed by the encoding apparatus. The inverse transform can be performed based on the transmission unit determined by the encoding apparatus. In the transforming unit of the encoding apparatus, DCT and DST can be selectively performed according to a plurality of information such as a prediction method, a size and a prediction direction of a current block, and the inverse transforming units 240 and 241 of a decoding apparatus It is possible to perform an inverse conversion based on the performed conversion information. Conversion can be performed based on an encoding block rather than a conversion block.

The prediction units 250 and 251 can generate prediction blocks based on the prediction block generation related information provided by the entropy decoding units 210 and 211 and the previously decoded blocks or picture information provided in the memories 270 and 271 .

The prediction units 250 and 251 may include a prediction unit determination unit, an inter-frame prediction unit, and an intra-frame prediction unit.

The prediction unit determination unit receives various information such as prediction unit information input from the entropy decoding unit, prediction mode information of the intra prediction method, motion prediction related information of the inter picture prediction method, and separates prediction blocks in the current coding block. It is possible to determine whether the inter-picture prediction is performed or the intra-picture prediction is performed.

The inter-picture prediction unit uses the information necessary for the inter-picture prediction of the current prediction block provided by the coding apparatus to predict the current picture based on the information included in at least one of the previous picture of the current picture or the following picture The inter-picture prediction can be performed. In order to perform inter-picture prediction, a motion prediction method of a prediction block included in a coded block based on a coded block is classified into a skip mode, a merge mode, a mode using an MVP (motion vector predictor) Mode) can be determined.

The intra prediction unit can generate a prediction block based on the reconstructed pixel information in the current picture. If the prediction block is a prediction block in which intra prediction is performed, intra prediction can be performed based on intra prediction mode information of the prediction block provided by the encoder. The intra-picture prediction unit includes an MDIS filter that performs filtering on the reference pixels of the current block, a reference pixel interpolator that interpolates reference pixels to generate reference pixels of a pixel unit less than an integer value, Lt; RTI ID = 0.0 > DCF < / RTI >

The predicting unit 250 of the upper layer decoding unit 200a may further include an inter-layer predicting unit for performing inter-layer prediction for predicting an upper layer using information of a lower layer.

The inter-layer prediction unit may perform inter-layer prediction using intra-picture prediction mode information, motion information, and the like.

Inter-layer prediction can predict a current block of an upper layer using motion information on a lower layer (reference layer) picture using a picture of a lower layer as a reference picture.

A picture of a reference layer used as a reference picture in inter-layer prediction may be a picture sampled according to the resolution of the current layer. In addition, the motion information may include a motion vector and a reference index. At this time, the value of the motion vector for the picture of the reference layer can be set to (0, 0).

As an example of inter-layer prediction, a prediction method of using a picture of a lower layer as a reference picture has been described, but the present invention is not limited to this. The inter-layer predicting unit 123 may further perform inter-layer texture prediction, inter-layer motion prediction, inter-layer syntax prediction, and inter-layer difference prediction.

Inter-layer texture prediction can derive the texture of the current layer based on the texture of the reference layer. The texture of the reference layer can be sampled to the resolution of the current layer, and the inter-layer prediction unit can predict the texture of the current layer based on the sampled texture. The inter-layer motion prediction can derive the motion vector of the current layer based on the motion vector of the reference layer. At this time, the motion vector of the reference layer can be scaled according to the resolution of the current layer. In the inter-layer syntax prediction, the syntax of the current layer can be predicted based on the syntax of the reference layer. For example, the inter-layer predicting unit 123 may use the syntax of the reference layer as the syntax of the current layer. In the inter-layer difference prediction, the picture of the current layer can be restored by using the difference between the restored image of the reference layer and the restored image of the current layer.

The reconstructed block or picture may be provided to the filter units 260 and 261. The filter units 260 and 261 may include a deblocking filter and an offset correction unit.

Information on whether or not a deblocking filter has been applied to the block or picture from the encoding device and information on whether a strong filter or a weak filter is applied can be provided when the deblocking filter is applied. In the deblocking filter of the decoding apparatus, the deblocking filter related information provided by the encoding apparatus is provided, and the decoding apparatus can perform deblocking filtering on the corresponding block.

The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction applied to the image and the offset value information during encoding.

The memories 270 and 271 can store the reconstructed picture or block to be used as a reference picture or a reference block, and can also output the reconstructed picture.

The encoding apparatus and the decoding apparatus can perform encoding on three or more layers instead of two layers. In this case, the encoding unit for the upper layer and the decoding unit for the upper layer are provided in a plurality corresponding to the number of the upper layers .

In SVC (Scalable Video Coding) which supports multi-layer structure, there is a relation between layers. By using this association, prediction can be performed to remove redundant elements of data and enhance the image coding performance.

Therefore, in the case of predicting a picture (video) of a current layer (enhancement layer) to be encoded / decoded, not only inter prediction or intra prediction using information of the current layer but also interlayer prediction using information of another layer can be performed .

In performing inter-layer prediction, the current layer may generate a prediction sample of a current layer using a decoded picture of a reference layer used for inter-layer prediction as a reference picture.

At this time, since at least one of the spatial resolution, the temporal resolution, and the image quality may be different between the current layer and the reference layer (i.e., due to the inter-layer scalability difference), the picture of the decoded reference layer, After resampling is performed, it can be used as a reference picture for interlayer prediction of the current layer. Resampling means up-sampling or down-sampling of the samples of the reference layer picture in accordance with the picture size of the current layer.

In this specification, a current layer refers to a layer on which encoding or decoding is currently performed, and may be an enhancement layer or an upper layer. A reference layer is a layer that the current layer refers to for interlayer prediction, and can be a base layer or a lower layer. A picture of a reference layer (i.e., a reference picture) used for inter-layer prediction of the current layer may be referred to as an inter-layer reference picture or a reference picture between layers.

3 is a flowchart illustrating a process of performing inter-layer prediction of a current layer using a reference picture of a reference layer according to an embodiment of the present invention.

Referring to FIG. 3, the filter coefficient of the up-sampling filter applied to the reference picture of the reference layer can be obtained (S300).

Here, the reference picture of the reference layer may refer to a picture corresponding to the current picture of the current layer performing inter-layer prediction.

Specifically, the reference layer may refer to a base layer or another enhancement layer having a lower resolution than the current layer. The reference picture may refer to a picture located in the same time zone as the current picture of the current layer. For example, the corresponding picture may be a picture having picture order count (POC) information that is the same as the current picture of the current layer.

Further, the filter coefficient of the up-sampling filter can be obtained in consideration of the phase of the reference sample in the reference picture corresponding to the current sample of the current layer. Here, the up-sampling filter may use either a fixed up-sampling filter or an adaptive up-sampling filter.

1. Fixed Upsampling Filter

The fixed up-sampling filter may refer to an up-sampling filter having a predetermined filter coefficient without considering the characteristics of the image. A tap filter can be used as the fixed up-sampling filter, which can be defined for the luminance component and the chrominance component, respectively. A fixed up-sampling filter having an accuracy of 1/16 sample units will be described with reference to Tables 1 to 2 below.

Phase p
Interpolation filter coefficient f [p, 0] f [p, 1] f [p, 2] f [p, 3] f [p, 4] f [p, 5] f [p, 6] f [p, 7] 0 0 0 0 64 0 0 0 0 One 0 One -3 63 4 -2 One 0 2 -One 2 -5 62 8 -3 One 0 3 -One 3 -8 60 13 -4 One 0 4 -One 4 -10 58 17 -5 One 0 5 -One 4 -11 52 26 -8 3 -One 6 -One 3 -3 47 31 -10 4 -One 7 -One 4 -11 45 34 -10 4 -One 8 -One 4 -11 40 40 -11 4 -One 9 -One 4 -10 34 45 -11 4 -One 10 -One 4 -10 31 47 -9 3 -One 11 -One 3 -8 26 52 -11 4 -One 12 0 One -5 17 58 -10 4 -One 13 0 One -4 13 60 -8 3 -One 14 0 One -3 8 62 -5 2 -One 15 0 One -2 4 63 -3 One 0

Table 1 is a table defining the filter coefficients of the fixed up-sampling filter with respect to the luminance component.

As shown in Table 1, in the case of upsampling on the luminance component, an 8-tap filter is applied. That is, interpolation can be performed using a reference sample of the reference layer corresponding to the current sample of the current layer and a neighboring sample adjacent to the reference sample. Here, the neighbor samples can be specified according to the direction in which the interpolation is performed. For example, when interpolation is performed in the horizontal direction, the neighboring sample may include three consecutive samples to the left and four consecutive samples to the right based on the reference sample. Alternatively, when interpolation is performed in the vertical direction, the neighboring sample may include three consecutive samples at the top and four consecutive samples at the bottom based on the reference sample.

Since interpolation is performed with an accuracy of 1/16 sample units, there are a total of 16 phases. This is to support resolution of various magnifications such as 2 times and 1.5 times.

In addition, the fixed up-sampling filter may use different filter coefficients for each phase (p). The size of each filter coefficient may be defined to fall within a range of 0 to 63, except when the phase p is zero. This means that the filtering is performed with a precision of 6 bits. Here, the phase (p) of 0 means the position of an integer multiple of n when interpolation is performed in 1 / n sample units.

Phase p
Interpolation filter coefficient f [p, 0] f [p, 1] f [p, 2] f [p, 3] 0 0 64 0 0 One -2 62 4 0 2 -2 58 10 -2 3 -4 56 14 -2 4 -4 54 16 -2 5 -6 52 20 -2 6 -6 46 28 -4 7 -4 42 30 -4 8 -4 36 36 -4 9 -4 30 42 -4 10 -4 28 46 -6 11 -2 20 52 -6 12 -2 16 54 -4 13 -2 14 56 -4 14 -2 10 58 -2 15 0 4 62 -2

Table 2 defines the filter coefficients of the fixed up-sampling filter for the chrominance components.

As shown in Table 2, in case of up-sampling for the chrominance components, a 4-tap filter can be applied unlike the luminance component. That is, interpolation can be performed using a reference sample of the reference layer corresponding to the current sample of the current layer and a neighboring sample adjacent to the reference sample. Here, the neighbor samples can be specified according to the direction in which the interpolation is performed. For example, when interpolation is performed in the horizontal direction, the neighboring sample may include one continuous sample to the left and two consecutive samples to the right based on the reference sample. Alternatively, when interpolation is performed in the vertical direction, the neighboring sample may include one continuous sample at the top and two consecutive samples at the bottom based on the reference sample.

On the other hand, as in the case of the luminance component, since interpolation is performed with an accuracy of 1/16 sample units, there are a total of 16 phases, and different filter coefficients can be used for each phase (p). And, the size of each filter coefficient can be defined to fall in the range of 0 to 62, except when the phase (p) is zero. This also means that filtering is performed with a precision of 6 bits.

The 8-tap filter is applied to the luminance component and the 4-tap filter is applied to the chrominance component. However, the present invention is not limited to this, and the order of the tap filter may be variably determined in consideration of the coding efficiency Of course it is.

2. Adaptive up-sampling filter

It is possible to determine the optimum filter coefficient in the encoder considering the feature of the image without using the fixed filter coefficient, signaling it to the decoder, and transmit it to the decoder. It is the adaptive up-sampling filter that uses adaptively determined filter coefficients in the encoder. Since the characteristics of the image are different in picture units, it is possible to improve the coding efficiency by using an adaptive up-sampling filter capable of expressing characteristics of the image better than using a fixed up-sampling filter in all cases.

(1) Filter coefficient coding method

The encoder may determine the filter coefficients of the adaptive up-sampling filter and code it as is. In this case, the decoder can obtain the filter coefficient from the bitstream through entropy decoding, and apply it to the reference picture to generate an interlayer reference picture.

The determined filter coefficient may not be coded as it is, and the number of bits required for coding the filter coefficient may be reduced through differential coding.

For example, the encoder may determine an optimal filter coefficient for the adaptive up-sampling filter for each phase p. The filter coefficient for the i-th phase p may be coded by a difference coefficient with the filter coefficient for the (i-1) -th phase p. Here, when interpolation is performed in 1 / n sample units, since n phases exist, i means a natural number equal to or greater than 1 and less than or equal to (n-1).

Thus, the i-th phase (p _i) if the coded difference between the filter coefficients for the (i-1) th phase (p _(i-1)) the filter coefficients for the decoder is the i-th phase from the bit stream (p _i ) and derive a filter coefficient for the i th phase (p _i ) by adding it to the filter coefficient for the (i-1) th phase p _(i-1) have.

Alternatively, the encoder may determine filter coefficients and encoding the difference to the coefficient of the filter coefficients for the i th phase of the up-sampling filter fixing them (p _i) for the i-th phase (p _i).

In this case, the decoder i th phase (p _i) i th phase obtaining the difference filter coefficients, and in addition the filter coefficients for the i th phase of the up-sampling filter fixing them (p _i) for from a bitstream (p _i ) May be derived.

However, as described above, when the filter coefficient is coded by the differential coding method, the size of the differential filter coefficient may be limited to not exceed 7. This is to prevent the overflow of the temporary buffer from occurring by coding the difference filter coefficient within 3 bits. Meanwhile, the differential filter coefficient can be entropy coded by a fixed length code or a truncated unary code scheme.

(2) Unit of transmission of filter coefficient

If a separate syntax for the adaptive upsampling filter is defined, it may be obtained from the corresponding syntax (e.g., an adaptive parameter set). Alternatively, the encoder may determine and transmit filter coefficients that are commonly applicable to all pictures belonging to the video sequence. In this case, the decoder may obtain the filter coefficients of the adaptive up-sampling filter in a sequence level syntax (e.g., a sequence parameter set), or the encoder may determine filter coefficients applied in picture or slice units, It may be transmitted. In this case, the decoder may obtain a filter coefficient in a syntax of a picture level syntax or a slice level syntax (e.g., a picture parameter set, a slice header, and a slice segment header). Hereinafter, a method of acquiring the filter coefficient of the adaptive up-sampling filter in the decoder will be described in detail with reference to FIGS. 4 to 9. FIG.

Referring to FIG. 3, an interlayer reference picture may be generated by applying the filter coefficient obtained in step S300 to a reference picture (S310).

Specifically, by performing the interpolation using the obtained filter coefficients, the reference picture can be upsampled. Here, the interpolation may be performed primarily in the horizontal direction and may be performed in the vertical direction with respect to the sample generated after the interpolation in the horizontal direction.

The inter-prediction of the current block may be performed based on the inter-layer reference picture generated in step S310 (S320).

It is possible to generate a reference picture list including an interlayer reference picture for inter prediction.

For example, it is possible to construct a reference picture list by using a reference picture belonging to the same layer as the current block, that is, a temporal reference picture, and arrange an interlayer reference picture after the temporal reference picture.

Alternatively, an interlayer reference picture may be added between temporal reference pictures. For example, the interlayer reference pictures may be arranged after the first temporal reference picture in the reference picture list composed of temporal reference pictures. The first temporal reference picture in the reference picture list may refer to a reference picture having a reference index 0. [ In this case, the reference index 1 may be assigned to the interlayer reference pictures arranged after the first temporal reference picture.

Furthermore, a reference picture may be specified in the generated reference picture list using the reference index of the current block, and the reference block reference block may be specified using the motion vector of the current block. Therefore, the current block can perform inter prediction using the specified reference block. However, when the current block uses an inter-layer reference picture as a reference picture, the current block can perform inter-layer prediction using blocks in the same position in the inter-layer reference picture. For this purpose, when the reference index of the current block specifies an interlayer reference picture in the reference picture list, the motion vector of the current block can be set to (0, 0).

FIG. 4 illustrates a method of selectively using an adaptive up-sampling filter for a reference picture according to an embodiment to which the present invention is applied.

In FIG. 4, the adaptive upsampling flag (adaptive_upsampling_flag) may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter. FIG. 4 illustrates a process of acquiring filter coefficients at a slice level. However, it is needless to say that it is possible to acquire the filter coefficients at the sequence level and the picture level as shown in FIG.

Referring to FIG. 4, an adaptive up-sampling flag for the current slice may be obtained (S400).

If the adaptive up-sampling flag obtained in step S400 specifies that the adaptive up-sampling filter is used, the filter coefficient of the adaptive up-sampling filter may be obtained (S410).

Specifically, the filter coefficients of the adaptive up-sampling filter can be obtained for the luminance component and the chrominance component, respectively. Further, the filter coefficients can be obtained for each phase p _i . A filter coefficient of the n-tap filter may be obtained for each luminance component for each phase p _i , and a filter coefficient of the m-tap filter may be obtained for each chrominance component. Here, n and m mean natural numbers greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, when a fixed up-sampling filter is an 8-tap filter for a luminance component and a 4-tap filter for a chrominance component, as shown in FIG. 4, And the filter coefficients of the 4-tap filter may be obtained for the chrominance components, respectively.

On the other hand, when it is specified that the adaptive up-sampling flag obtained in step S400 uses the fixed up-sampling filter, the filter coefficient of the adaptive up-sampling filter is not obtained from the bit stream, Lt; / RTI >

Thus, by using the adaptive up-sampling flag, the up-sampling filter for the reference picture can be selectively used.

FIG. 5 illustrates a method of selectively using an adaptive up-sampling filter for each of a luminance component and a chrominance component to which the present invention is applied.

First, an adaptive up-sampling luma flag (adaptive_upsampling_luma_flag) may be obtained (S500).

The adaptive upsampling luma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the luminance component of the reference picture.

If the adaptive upsampling luma flag obtained in step S500 specifies that an adaptive upsampling filter is used, a filter coefficient applied to the luminance component may be obtained (S510).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficient of the n-tap filter can be obtained for each luminance component for each phase p _i . Here, n means a natural number greater than 1.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, if the fixed up-sampling filter is an 8-tap filter for the luminance component, the filter coefficient of the 8-tap filter may be obtained for the luminance component as shown in Fig.

Conversely, when the adaptive upsampling flag obtained in step S500 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

On the other hand, an adaptive upsampling chroma flag (adaptive_upsampling_chroma_flag) may be obtained (S520).

The adaptive upsampling chroma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component of the reference picture.

If the adaptive upsampling chroma flag obtained in step S520 specifies that the adaptive upsampling filter is used, a filter coefficient applied to the chrominance component may be obtained (S530).

Here, the filter coefficients can be obtained for each phase p _i . A filter coefficient of an m-tap filter for a chrominance component can be obtained for each phase p _i . Here, m means a natural number greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, if the fixed up-sampling filter is a 4-tap filter for the chrominance components, the filter coefficients of the 4-tap filter may be obtained for the chrominance components as shown in FIG.

In contrast, when the adaptive upsampling chroma flag obtained in step S520 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

FIG. 6 illustrates a method of selectively using an adaptive up-sampling filter for each of a luminance component and two chrominance components (Cb and Cr) to which the present invention is applied.

First, an adaptive up-sampling luma flag (adaptive_upsampling_luma_flag) may be obtained (S600).

The adaptive upsampling luma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the luminance component of the reference picture.

If the adaptive upsampling luma flag obtained in step S600 specifies that an adaptive upsampling filter is used, a filter coefficient applied to the luminance component may be obtained (S610).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficient of the n-tap filter can be obtained for each luminance component for each phase p _i . Here, n means a natural number greater than 1.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, if the fixed up-sampling filter is an 8-tap filter for the luminance component, the filter coefficient of the 8-tap filter may be obtained for the luminance component as shown in FIG.

Conversely, when the adaptive upsampling flag obtained in step S600 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

On the other hand, the chrominance components Cb and Cr may have different characteristics from each other. It is possible to determine whether to use the adaptive upsampling filter for each of Cb and Cr in the encoding step and to perform signaling without determining whether to use the adaptive upsampling filter for the entire chrominance components.

Referring to FIG. 6, a first adaptive upsampling chroma flag (adaptive_upsampling_Cb_flag) for the current slice may be obtained (S620).

The first adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component Cb of the reference picture.

If the first adaptive upsampling chroma flag obtained in step S620 specifies that the adaptive upsampling filter is used, a filter coefficient applied to the chrominance component Cb may be obtained (S630).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficients of the m-tap filter for the chrominance component Cb can be obtained for each phase p _i , respectively. Here, m means a natural number greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, if the fixed up-sampling filter is a 4-tap filter for a chrominance component, the filter coefficients of the 4-tap filter may be obtained for the chrominance component Cb as shown in FIG.

In contrast, when the first adaptive upsampling chroma flag obtained in step S620 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

Then, a second adaptive upsampling chroma flag (adaptive_upsampling_Cr_flag) for the current slice may be obtained (S640).

The second adaptive upsampling chroma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component Cr of the reference picture.

If the second adaptive upsampling chroma flag obtained in step S640 specifies that the adaptive upsampling filter is used, a filter coefficient applied to the chrominance component Cr may be obtained (S650).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficients of the m-tap filter for the chrominance component Cr can be obtained for each phase p _i , respectively. Here, m means a natural number greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, when the fixed up-sampling filter is a 4-tap filter for the chrominance component Cr, the filter coefficients of the 4-tap filter may be obtained for the chrominance component Cr, respectively, as shown in FIG.

In contrast, when the second adaptive upsampling chroma flag obtained in step S640 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

FIG. 7 illustrates a method of obtaining filter coefficients of an adaptive up-sampling filter based on a first adaptive component flag, according to an embodiment to which the present invention is applied.

5, in order to specify whether an adaptive up-sampling filter is used for each of the luminance component and chrominance component of the reference picture, two flags, i.e., an adaptive up-sampling luma flag and an adaptive up- All should be coded.

A first adaptive component flag (adaptive_component_flag) may be used to reduce the coding burden. The first adaptive component flag may refer to information specifying whether an adaptive up-sampling filter is used for at least one of a luminance component and a chrominance component of the reference picture.

If the first adaptive component flag specifies that an adaptive up-sampling filter is used for at least one of the luminance component and the chrominance component, an adaptive up-sampling luma flag and an adaptive up- It is necessary to acquire a chroma flag.

However, when the first adaptive component flag specifies that an adaptive up-sampling filter is not used for both the luminance component and the chrominance component, an adaptive up-sampling luma flag and an adaptive up- There is no need to acquire chroma flags.

Referring to FIG. 7, a first adaptive component flag (adaptive_component_flag) for the current slice may be obtained (S700).

If the first adaptive component flag specifies that an adaptive up-sampling filter is to be used for at least one of the luminance component and the chrominance component, an adaptive up-sampling luma flag (adaptive_upsampling_luma_flag) may be obtained (S710).

The adaptive upsampling luma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the luminance component of the reference picture.

If the adaptive upsampling luma flag obtained in step S710 specifies that an adaptive upsampling filter is used, a filter coefficient applied to the luminance component may be obtained (S720).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficient of the n-tap filter can be obtained for each luminance component for each phase p _i . Here, n means a natural number greater than 1.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, in the case where the fixed up-sampling filter is an 8-tap filter for the luminance component, the filter coefficient of the 8-tap filter may be obtained for the luminance component as shown in Fig.

Conversely, when the adaptive upsampling flag obtained in step S710 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

On the other hand, if the first adaptive component flag specifies that an adaptive up-sampling filter is used for at least one of the luminance component and the chrominance component, the adaptive up-sampling chroma flag (adaptive_upsampling_chroma_flag) may be obtained (S730).

The adaptive upsampling chroma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component of the reference picture.

If the adaptive upsampling chroma flag obtained in step S730 specifies that the adaptive upsampling filter is used, a filter coefficient applied to the chrominance component may be obtained (S740).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficients of the m-tap filter for the chrominance components can be obtained for each phase p _i , respectively. Here, m means a natural number greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, if the fixed up-sampling filter is a 4-tap filter for the chrominance components, the filter coefficients of the 4-tap filter may be obtained for the chrominance components as shown in FIG. Although not shown in FIG. 7, the filter coefficients for the chrominance components may be obtained for each of the chrominance components Cb and Cr.

In contrast, when the adaptive upsampling chroma flag obtained in step S730 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

Figure 8 illustrates a method of obtaining the filter coefficients of an adaptive up-sampling filter based on a second adaptive component flag, as an example of an application to which the present invention is applied.

6, in order to specify whether the adaptive upsampling filter is used for each of the luminance component of the reference picture and the chrominance components Cb and Cr, three flags, i.e., an adaptive upsampling luma flag, a first adaptive Both the up-sampling chroma flag and the second adaptive up-sampling chroma flag must be coded.

A second adaptive component flag (adaptive_component_flag) may be used to reduce the coding burden. The second adaptive component flag may refer to information specifying whether the adaptive up-sampling filter is used for at least one of the luminance component of the reference picture and the chrominance components Cb and Cr.

If the second adaptive component flag specifies that an adaptive up-sampling filter is to be used for at least one of the luminance component and the chrominance components Cb and Cr, an adaptive up-sampling luma Flag and an adaptive upsampling chroma flag.

However, when the second adaptive component flag specifies that the adaptive up-sampling filter is not used for both the luminance component and the chrominance components Cb and Cr, an adaptive up-sampling luma Flags, a first adaptive upsampling chroma flag, and a second adaptive upsampling chroma flag.

Referring to FIG. 8, a second adaptive component flag (adaptive_component_flag) for the current slice may be obtained (S800).

If the second adaptive component flag specifies that an adaptive up-sampling filter is used for at least one of the luminance component and the chrominance components Cb and Cr, an adaptive up-sampling luma flag (adaptive_upsampling_luma_flag) may be obtained (S810) .

The adaptive upsampling luma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the luminance component of the reference picture.

If the adaptive upsampling luma flag obtained in step S810 specifies that the adaptive upsampling filter is used, a filter coefficient applied to the luminance component may be obtained (S820).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficient of the n-tap filter can be obtained for each luminance component for each phase p _i . Here, n means a natural number greater than 1.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, when the fixed up-sampling filter is an 8-tap filter for the luminance component, the filter coefficient of the 8-tap filter may be obtained for the luminance component as shown in Fig.

Conversely, when the adaptive upsampling flag obtained in step S810 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

On the other hand, when the second adaptive component flag specifies that the adaptive up-sampling filter is used for at least one of the luminance component and the chrominance components Cb and Cr, the first adaptive up-sampling chroma flag (adaptive_upsampling_Cb_flag) (S830).

The first adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component Cb of the reference picture.

If the first adaptive upsampling chroma flag obtained in step S830 specifies that the adaptive upsampling filter is used, a filter coefficient applied to the chrominance component Cb may be obtained (S840).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficients of the m-tap filter for the chrominance component Cb can be obtained for each phase p _i , respectively. Here, m means a natural number greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, if the fixed up-sampling filter is a 4-tap filter for the chrominance component Cb, the filter coefficients of the 4-tap filter may be obtained for the chrominance component Cb as shown in FIG.

In contrast, when the first adaptive upsampling chroma flag obtained in step S830 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

In addition, when the second adaptive component flag specifies that an adaptive up-sampling filter is used for at least one of the luminance component and the chrominance components Cb and Cr, a second adaptive up-sampling chroma flag (adaptive_upsampling_Cr_flag) (S850).

The second adaptive upsampling chroma flag may refer to information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component Cr of the reference picture.

If the second adaptive upsampling chroma flag obtained in step S850 specifies that the adaptive upsampling filter is used, a filter coefficient applied to the chrominance component Cr may be obtained (S860).

Here, the filter coefficients can be obtained for each phase p _i . The filter coefficients of the m-tap filter for the chrominance component Cr can be obtained for each phase p _i , respectively. Here, m means a natural number greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, when the fixed up-sampling filter is a 4-tap filter for the chrominance component Cr, the filter coefficients of the 4-tap filter may be obtained for the chrominance component Cr, respectively, as shown in FIG.

In contrast, when the second adaptive upsampling chroma flag obtained in step S850 specifies that a fixed upsampling filter is used, the filter coefficient can be obtained from the predefined table shown in FIG.

FIG. 9 illustrates a method of adaptively acquiring filter coefficients for each phase of a reference sample according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 9, an adaptive upsampling flag (adaptive_upsampling_flag) for the current slice may be obtained (S900).

As discussed above, the adaptive upsampling flag may refer to information that specifies whether to use a fixed upsampling filter or an adaptive upsampling filter for the reference picture. However, the present invention is not limited to obtaining the filter coefficients at the slice level, and can be obtained at the sequence level and the picture level.

If the adaptive upsampling flag obtained in step S900 specifies that the adaptive upsampling filter is to be used, an adaptive luma phase flag (adaptive_luma_phase_flag) may be obtained (S910).

Here, the adaptive luma phase flag may mean information specifying whether or not a filter coefficient for the i-th phase applied to the luminance component exists. That is, based on the adaptive luma phase flag, it is possible to identify the presence or absence of the filter coefficient applied to the luminance component on a phase-by-phase basis.

If the adaptive luma phase flag obtained in step S910 specifies that there is a coded filter coefficient for the i < th > phase, the filter coefficient applied to the luminance component may be obtained (S920).

Specifically, the filter coefficient of the n-tap filter for the i-th phase can be obtained. Here, n means a natural number greater than 1.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, when the fixed up-sampling filter is an 8-tap filter for the luminance component, the filter coefficient of the 8-tap filter may be obtained for the luminance component as shown in Fig.

Conversely, if the adaptive luma phase flag obtained in step S910 specifies that there is no coded filter coefficient for the i-th phase, the filter coefficient for that i-th phase is not extracted.

Also, if the adaptive upsampling flag obtained in step S900 specifies that the adaptive upsampling filter is used, an adaptive chroma phase flag (adaptive_chroma_phase_flag) may be obtained (S930).

Here, the adaptive chroma phase flag may be information for specifying whether or not a filter coefficient for the i-th phase applied to the chrominance component exists. That is, the presence or absence of the filter coefficient applied to the chrominance component for each phase can be confirmed based on the adaptive chroma phase flag.

If the adaptive chroma phase flag obtained in step S930 specifies that there is a coded filter coefficient for the i-th phase, the filter coefficient applied to the chrominance component may be obtained (S940).

Specifically, the filter coefficient of the m-tap filter for the i-th phase can be obtained. Here, m means a natural number greater than one.

In addition, a tap filter of the same order as the fixed up-sampling filter can be used for compatibility with the fixed up-sampling filter. For example, if the fixed up-sampling filter is a 4-tap filter for a chrominance component, the filter coefficients of the 4-tap filter may be obtained for chrominance components as shown in FIG.

Further, a filter coefficient can be obtained for each of the color difference components Cb and Cr. However, the present invention is not limited to this, and filter coefficients that are equally applicable to the chrominance components Cb and Cr may be obtained.

On the other hand, when the adaptive chroma phase flag obtained in step S930 specifies that there is no coded filter coefficient for the i-th phase, the filter coefficient for the i-th phase is not extracted.

On the other hand, the adaptive luma phase flag and the adaptive chroma phase flag as described above are not limited to this embodiment and can be used in the same manner in the embodiments of Figs.

Claims (15)

Obtaining a filter coefficient of an up-sampling filter applied to a reference picture of a reference layer; Here, the up-sampling filter is either a fixed up-sampling filter or an adaptive up-sampling filter,
Generating the inter-layer reference picture by applying the obtained filter coefficient to the reference picture; And
And performing inter-prediction on the current block of the current layer based on the generated inter-layer reference picture. 2. The method of claim 1, wherein obtaining the filter coefficient comprises:
Obtaining an adaptive up-sampling flag for the current picture of the current layer; And
Sampling the filter coefficients of the adaptive up-sampling filter based on the adaptive up-sampling flag,
Wherein the adaptive upsampling flag is information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter. 3. The method of claim 2,
Wherein the adaptive upsampling flag is obtained for a luminance component and a chrominance component of the reference picture, respectively. The method of claim 3,
An adaptive upsampling flag for each of the luminance component and chrominance component is obtained based on an adaptive component flag,
Wherein the adaptive component flag is information for specifying whether an adaptive up-sampling filter is used for at least one of a luminance component and a chrominance component of the reference picture. 3. The method of claim 2, wherein obtaining the filter coefficients of the adaptive up-
Obtaining an adaptive luma phase flag that specifies whether there is a filter coefficient for an i-th phase applied to a luminance component of the reference picture; And
And obtaining a filter coefficient for an i-th phase applied to a luminance component of the reference picture based on the adaptive luma phase flag. An entropy decoding unit for obtaining a filter coefficient of an up-sampling filter applied to a reference picture of a reference layer; And
And a prediction unit that applies the obtained filter coefficient to the reference picture to generate an inter-layer reference picture, and performs inter-prediction on the current block of the current layer based on the generated inter-layer reference picture,
Wherein the upsampling filter is one of a fixed upsampling filter and an adaptive upsampling filter. 7. The apparatus of claim 6, wherein the entropy decoding unit comprises:
Acquiring an adaptive up-sampling flag for the current picture of the current layer,
Obtaining a filter coefficient of the adaptive up-sampling filter based on the obtained adaptive up-sampling flag,
Wherein the adaptive up-sampling flag is information specifying whether to use a fixed up-sampling filter or an adaptive up-sampling filter. 8. The apparatus of claim 7, wherein the entropy decoding unit comprises:
And obtains the adaptive upsampling flag for each of a luminance component and a chrominance component of the reference picture. The apparatus of claim 8, wherein the entropy decoding unit comprises:
An adaptive up-sampling flag for each of the luminance component and the chrominance component is obtained based on an adaptive component flag,
Wherein the adaptive component flag is information for specifying whether an adaptive up-sampling filter is used for at least one of a luminance component and a chrominance component of the reference picture. 8. The apparatus of claim 7,
Acquiring an adaptive luma phase flag that specifies whether a filter coefficient for an i-th phase applied to a luminance component of the reference picture exists,
And obtains a filter coefficient for an i-th phase applied to a luminance component of the reference picture based on the adaptive luma phase flag. Obtaining a filter coefficient of an up-sampling filter applied to a reference picture of a reference layer; Here, the up-sampling filter is either a fixed up-sampling filter or an adaptive up-sampling filter,
Generating the inter-layer reference picture by applying the obtained filter coefficient to the reference picture; And
And performing inter-prediction on the current block of the current layer based on the generated inter-layer reference picture. 12. The method of claim 11, wherein obtaining the filter coefficients comprises:
Obtaining an adaptive up-sampling flag for the current picture of the current layer; And
Sampling the filter coefficients of the adaptive up-sampling filter based on the adaptive up-sampling flag,
Wherein the adaptive upsampling flag is information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter. 13. The method of claim 12,
Wherein the adaptive upsampling flag is obtained for the luminance component and chrominance component of the reference picture, respectively. 14. The method of claim 13,
An adaptive upsampling flag for each of the luminance component and chrominance component is obtained based on an adaptive component flag,
Wherein the adaptive component flag is information for specifying whether an adaptive up-sampling filter is used for at least one of a luminance component and a chrominance component of the reference picture. 13. The method of claim 12, wherein obtaining the filter coefficients of the adaptive up-
Obtaining an adaptive luma phase flag that specifies whether there is a filter coefficient for an i-th phase applied to a luminance component of the reference picture; And
And obtaining a filter coefficient for an i-th phase applied to a luminance component of the reference picture based on the adaptive luma phase flag.

Images