KR20170124080A - Method and apparatus for encoding/decoding a video signal - Google Patents

Abstract

According to the present invention, a method for decoding an image signal comprises the steps of: generating a weighted value prediction parameter set on a current block based on a weighted value prediction parameter of a neighboring block adjacent to the current block; determining a weighted value prediction parameter of the current block based on the weighted value prediction parameter set and index information; and performing inter-prediction on the current block by using the weighted value prediction parameter of the current block. By performing the inter-prediction using a weighted value, the inter-prediction efficiency is improved.

Description

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

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

In recent years, demand for multimedia data such as video has been rapidly increasing on the Internet. However, the rate at which the bandwidth of a channel develops is hard to follow the amount of multimedia data that is rapidly increasing. Accordingly, Video Coding Expert Group (VCEG) of ITU-T and Moving Picture Expert Group (ISO / IEC) of Moving Picture Expert Group (MPEG) of International Standardization Organization have agreed to implement High Efficiency Video Coding (HEVC) Respectively.

HEVC defines techniques such as intra prediction, inter prediction, transform, quantization, entropy coding, and in-loop filters. Among them, inter-picture prediction is performed by using motion information such as a motion vector, a reference picture index, an inter prediction indicator, and the like, it means.

The higher the correlation between images, the higher the prediction efficiency can be obtained. However, if there is a change in brightness between images such as a fade-in or a fade-out, the inter-picture prediction result may be inaccurate if the correlation between the images is lowered. In order to solve such a problem, the present invention proposes weight prediction. Here, the weight prediction may mean that, when there is a change in brightness between images, the weight is estimated by the degree of brightness change, and the estimated weight is applied to the inter-view prediction.

The main object of the present invention is to improve inter picture prediction efficiency by performing inter picture prediction using a weight in coding / decoding an image.

The present invention relates to an apparatus and a method capable of effectively performing inter-picture prediction even when a plurality of light sources exist in an image or a brightness change exists only in a local region by selectively using a weight in coding / decoding an image The main purpose is to provide.

The method and apparatus for decoding a video signal according to the present invention generate a set of weighted prediction parameters for the current block based on weighted prediction parameters of neighboring blocks neighboring the current block, The weight prediction parameter for the current block may be determined and the inter prediction may be performed for the current block using the weight prediction parameter of the current block.

In the video signal decoding method and apparatus according to the present invention, the weight prediction parameter set may include at least one of a forward weighted prediction parameter of the neighboring block or a reverse weighted prediction parameter of the neighboring block in accordance with a prediction direction of the current block Can be created on the basis of.

In the method and apparatus for decoding a video signal according to the present invention, when the prediction direction of the current block is bidirectional, the weight prediction parameter set includes both the forward weighting parameter of the neighboring block and the backward weighting prediction parameter of the neighboring block .

In the method and apparatus for decoding a video signal according to the present invention, when the number of weight prediction parameters obtainable from the neighboring block is smaller than the number of maximum weight prediction parameters that can be included in the weight prediction parameter set, The parameter set may further include a combined weight prediction parameter generated by combining the weight prediction parameters of the neighboring blocks.

In the video signal decoding method and apparatus according to the present invention, a plurality of weight prediction parameters included in the weight prediction parameter set may be arranged in a predetermined order.

A method and apparatus for encoding an image signal according to the present invention includes generating a set of weighted prediction parameters for the current block based on weighted prediction parameters of neighboring blocks neighboring the current block, A weight prediction parameter for the current block is determined, and index information for specifying the determined weight prediction parameter is encoded.

In the method and apparatus for encoding an image signal according to the present invention, the weight prediction parameter set may include at least one of a forward weighted prediction parameter of the neighboring block or an inverse weighted prediction parameter of the neighboring block, Can be created on the basis of.

In the method and apparatus for encoding an image signal according to the present invention, when the prediction direction of the current block is bidirectional, the weight prediction parameter set includes both the forward weighting parameter of the neighboring block and the backward weighting prediction parameter of the neighboring block .

When the number of weight prediction parameters obtainable from the neighboring block is smaller than the number of maximum weight prediction parameters that can be included in the weight prediction parameter set, The parameter set may further include a combined weight prediction parameter generated by combining the weight prediction parameters of the neighboring blocks.

In the video signal encoding method and apparatus according to the present invention, a plurality of weight prediction parameters included in the weight prediction parameter set may be arranged in a predetermined order.

Determining whether there is a brightness change between a current image including a current block and a reference image of the current image; and determining whether there is a brightness change between the current image and the reference image, Determines a weight prediction parameter for the current block based on index information for specifying any one of the weight prediction parameter candidates, and performs prediction on the current block based on the weight prediction parameter can do.

In the video signal decoding method and apparatus according to the present invention, the weight prediction parameter candidate may include a first weight prediction parameter for the reference image.

In the method and apparatus for decoding a video signal according to the present invention, when the current image includes at least one region capable of deriving a second weight prediction parameter, the weight prediction parameter candidate includes at least one second weight value And may further include a prediction parameter.

In the video signal decoding method and apparatus according to the present invention, the first weight prediction parameter may be derived based on a predicted value for the first weight prediction parameter and a residual value for the first weight prediction parameter.

In the video signal decoding method and apparatus according to the present invention, the predicted value for the first weight prediction parameter may be determined according to the accuracy of the current block.

In the video signal decoding method and apparatus according to the present invention, the maximum number of weight prediction parameter candidates may be adaptively determined according to the size of the current block.

In the video signal decoding method and apparatus according to the present invention, the weight prediction parameter candidate may include an initial weight prediction parameter having a predetermined weight value.

The method and apparatus for encoding an image signal according to the present invention determine whether there is a change in brightness between a current image including a current block and a reference image of the current image and if there is a change in brightness between the current image and the reference image Determining a weight prediction parameter candidate for the current block, determining a weight prediction parameter for the current block from among the weight prediction parameter candidates, encoding the index information for specifying the determined weight prediction parameter, Based on the weight prediction parameter, prediction of the current block can be performed.

In the video signal encoding method and apparatus according to the present invention, the weight prediction parameter candidate may include a first weight prediction parameter for the reference image.

In the method and apparatus for encoding an image signal according to the present invention, when the current image includes at least one region capable of deriving a second weight prediction parameter, the weight prediction parameter candidate includes at least one second weight And may further include a prediction parameter.

The method and apparatus for encoding an image signal according to the present invention can encode a difference value indicating a difference between the predicted values for the first weighted prediction parameter and the first weighted prediction parameter.

In the video signal encoding method and apparatus according to the present invention, the predicted value for the first weight prediction parameter may be determined according to the accuracy of the current block.

In the video signal encoding method and apparatus according to the present invention, the maximum number of weight prediction parameter candidates may be adaptively determined according to the size of the current block.

In the video signal encoding method and apparatus according to the present invention, the weight prediction parameter candidate may include an initial weight prediction parameter having a preset weight value.

In the present invention, inter picture prediction is performed using a weight in encoding / decoding an image, thereby improving inter picture prediction efficiency.

The present invention can effectively perform inter-picture prediction even when a plurality of light sources exist in an image or a brightness change exists only in a local region by selectively using a weight in encoding / decoding an image.

1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating an image decoding apparatus according to an embodiment of the present invention.
3 is a block diagram schematically illustrating a motion estimation method according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating locations of neighboring blocks for obtaining motion information to be applied to a current block to be coded according to an embodiment of the present invention.
5 is a diagram illustrating a brightness change pattern between a current image including a current block and a reference image.
6 is a flowchart showing a method of using a weight prediction parameter in an encoding apparatus.
7 is a diagram illustrating weight prediction parameters of neighboring blocks neighboring the current block.
8 is a view for explaining an example in which only some of the pixels are used for the weighted prediction parameter estimation of the current block.
9 shows an example in which combined weighted prediction parameters are generated.
10 shows an example of decoding a weight prediction parameter in the decoding apparatus.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals will be used for the same constituent elements in the drawings, and redundant explanations for the same constituent elements will be omitted.

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

1, an image encoding apparatus 100 includes an image divider 110, prediction units 120 and 125, a transform unit 130, a quantization unit 135, a reorder unit 160, an entropy encoding unit An inverse quantization unit 140, an inverse transform unit 145, a filter unit 150, and a memory 155. [

Each of the components 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 configuration unit. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of the constituent units may be combined to 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 separate embodiments of the components are also included within 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 image divider 110 may divide the input image into at least one block. At this time, a block may mean a coding unit (CU), a prediction unit (PU), or a conversion unit (TU). The partitioning may be performed based on at least one of a quadtree or a binary tree. The quad tree is a method of dividing the upper block into sub-blocks whose width and height are half of the upper block. A binary tree is a method of dividing an upper block into sub-blocks, either width or height, which is half of the upper block. Through the quadtree or binary tree based partitioning described above, a block can have a square as well as a non-square shape.

Hereinafter, in the embodiment of the present invention, a coding unit may be used as a unit for performing coding, or may be used as a unit for performing decoding.

The prediction units 120 and 125 may include an inter-picture prediction unit 120 for performing inter-picture prediction and an intra-picture prediction unit 125 for performing intra-picture prediction. It is possible to determine whether to use intra-picture prediction or intra-picture prediction for a prediction unit, and to determine concrete information (for example, intra-picture prediction mode, motion vector, reference picture, etc.) according to each prediction method. At this time, the processing unit in which the prediction is performed may be different from the processing unit in which the prediction method and the concrete contents are determined. For example, the method of prediction, the prediction mode and the like are determined as a prediction unit, and the execution of the prediction may be performed in a conversion unit.

The residual value (residual block) between the generated prediction block and the original block can be input to the conversion unit 130. [ In addition, the prediction mode information, motion vector information, and the like used for the prediction may be encoded by the entropy encoding unit 165 together with the residual value and transmitted to the decoder. When a particular encoding mode is used, it is also possible to directly encode the original block and transmit it to the decoding unit without generating a prediction block through the prediction units 120 and 125.

The inter-picture predicting unit 120 may predict a prediction unit based on information of at least one of a previous image or a following image of the current image, and may predict a prediction unit based on information of a partially- The prediction unit may also be predicted. The inter-frame prediction unit 120 may include a reference image interpolator, a motion information generator, and a motion compensator.

The reference image interpolator receives the reference image information from the memory 155 and generates pixel information of an integer number or less from the reference image. In the case of a luminance pixel, a DCT-based 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 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 motion information generating unit may generate motion information based on the reference image interpolated by the reference image interpolating unit. Here, the motion information refers to a motion vector, a reference image index, a prediction direction, and the like. As a method for estimating a motion vector, 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. Further, the motion vector may have a motion vector value of 1/2 or 1/4 pixel unit based on the interpolated pixel. In the inter-picture prediction, the current prediction unit can be predicted by differently generating the motion information. As the motion information generation method, various methods such as a merge method using a motion vector of a neighboring block and a motion estimation method (e.g., AMVP (Adaptive Motion Vector Prediction)) can be used.

For example, FIG. 3 shows an example of generating motion information through motion estimation. The motion estimation is to determine a motion vector of a current block, a reference image index, and an inter-picture prediction direction according to the determination, when a reference block identical or similar to a prediction block in a reference image that has already been encoded and decoded is determined.

When the AMVP method is used, the encoding device generates a predicted motion vector (MVP) by predicting a motion vector estimated in the current block, calculates a difference value (MVD) between the motion vector and the generated predicted motion vector, Motion Vector Difference) can be encoded.

A method of using a motion vector of a neighboring block is to apply motion information of a neighboring block neighboring the current block to the current block. In this case, the neighboring block may include a spatial neighboring block adjacent to the current block and a temporal neighboring block existing at the same position as the current block included in the reference image. For example, FIG. 4 illustrates neighboring blocks of the current block. The encoding apparatus may determine motion information of a current block by applying motion information of neighboring blocks (spatial neighboring blocks: A to E, temporal neighboring block: Col) of the current block shown in FIG. 4 to the current block. Here, Col denotes a block having the same or similar position as the current block existing in the reference image.

The intra prediction unit 125 can generate a prediction unit based on the reference pixel information around the current block which is pixel information in the current image. In the case where the neighboring block of the current prediction unit is a block in which inter-view prediction is performed and the reference pixel is a reconstructed pixel by performing inter-picture prediction, a reference pixel included in the inter- Can be replaced with the reference pixel information of the performed block. That is, when the reference pixel is not available, the usable reference pixel information can be replaced by at least one of the available reference pixels.

In the intra prediction, the prediction mode may have a directional prediction mode in which reference pixel information is used according to a prediction direction, and a non-directional mode in which direction information is not used in prediction. The mode for predicting the luminance information may be different from the mode for predicting the chrominance information and the intra prediction mode information or predicted luminance signal information used for predicting the luminance information may be utilized to predict the chrominance information .

In the intra prediction method, an AIS (Adaptive Intra Smoothing) filter can be applied to a reference pixel according to a prediction mode, and a prediction block can be generated. The type of the AIS filter applied to the reference pixel may be different. To perform the intra prediction method, the intra prediction mode of the current prediction unit can be predicted from the intra prediction mode of the prediction unit existing around the current prediction unit. When the intra prediction mode of the current prediction unit is predicted using the intra prediction mode information predicted from the peripheral prediction unit and the intra prediction mode of the current prediction unit is the same as the intra prediction mode of the current prediction unit, Information indicating that the prediction mode of the prediction unit is the same as the prediction mode of the surrounding prediction unit can be transmitted. If the prediction mode of the current prediction unit is different from the prediction mode of the surrounding prediction unit, the prediction mode information of the current block can be encoded by performing entropy coding.

In addition, a residual block including a prediction unit that has been predicted based on the prediction unit generated by the prediction units 120 and 125 and a residual value that is a difference value from the original block of the prediction unit may be generated. The generated residual block may be input to the transform unit 130. [

The transforming unit 130 may transform the residual block including residual data using a transform method such as DCT, DST, Karhunen Loeve Transform (KLT), or the like. In this case, the conversion method can be determined based on the intra prediction mode of the prediction unit used to generate the residual block. For example, DCT may be used in the horizontal direction, and DST may be used in the vertical direction, depending on the intra prediction mode.

The quantization unit 135 may quantize the values converted into the frequency domain by the conversion unit 130. [ The quantization factor may vary depending on the block or the importance of the image. The values calculated by the quantization unit 135 may be provided to the inverse quantization unit 140 and the reorder unit 160.

The transforming unit 130 and / or the quantizing unit 135 may be selectively included in the image encoding apparatus 100. That is, the image encoding apparatus 100 can perform at least one of conversion or quantization on the residual data of the residual block, or may skip both the conversion and the quantization, thereby encoding the residual block. A block entering the input of the entropy encoding unit 165 is generally referred to as a transform block even though either transformation or quantization is not performed in the image coding apparatus 100 or both transformation and quantization are not performed.

The reordering unit 160 can reorder the coefficient values with respect to the quantized residual values.

The reordering unit 160 may change the two-dimensional block type coefficient to a one-dimensional vector form through a coefficient scanning method. For example, the reordering unit 160 may scan a DC coefficient to a coefficient in the high frequency region using a predetermined scan type, and change it into a one-dimensional vector form.

The entropy encoding unit 165 may perform entropy encoding based on the values calculated by the reordering unit 160. 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 unit 165 receives the residual coefficient information of the encoding unit, the block type information, the prediction mode information, the division unit information, the prediction unit information, the transmission unit information, the motion Vector information, reference image information, interpolation information of a block, filtering information, and the like. In the entropy coding unit 165, the coefficients of the transform block include a flag indicating whether the absolute value of the coefficient is greater than 1, whether or not the absolute value of the coefficient is greater than 2 And the like may be coded. The entropy encoding unit 165 encodes the sign of the coefficient only for non-zero coefficients. A coefficient having an absolute value of the coefficient larger than 2 is encoded by subtracting 2 from the absolute value.

The entropy encoding unit 165 can entropy-encode the coefficient value of the encoding unit input by the reordering unit 160. [

The inverse quantization unit 140 and the inverse transformation unit 145 inverse quantize the quantized values in the quantization unit 135 and inversely transform the converted values in the conversion unit 130. [ The residual value generated by the inverse quantization unit 140 and the inverse transform unit 145 may be combined with a prediction block generated for each prediction unit through the prediction units 120 and 125 to generate a reconstructed block.

The filter unit 150 may include at least one of a deblocking filter, an offset correction unit, and an adaptive loop filter (ALF).

The deblocking filter can remove the block distortion caused by the boundary between the blocks in the reconstructed image. It may be determined whether to apply the 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 the deblocking filter. 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 in performing vertical filtering and horizontal filtering.

The offset correction unit may correct the offset of the deblocked image with respect to the original image on a pixel-by-pixel basis. In order to perform offset correction for a specific image, a method of dividing a pixel included in an image into an arbitrary area and then determining an area to perform an offset and applying an offset to the corresponding area, or a method of calculating an offset by considering edge information of each pixel You can use the method to apply.

Adaptive Loop Filtering (ALF) can be performed based on a value obtained by comparing the filtered restored image and 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 to apply the ALF may be transmitted for each coding unit (CU) in the case of a luminance signal, and the shape and the filter coefficient of the ALF filter to be applied may vary depending on each block. Also, an ALF filter of the same type (fixed form) may be applied irrespective of the characteristics of the application target block.

The memory 155 may store the restored block or image calculated through the filter unit 150 and the stored restored block or image may be provided to the predicting units 120 and 125 when the inter-view prediction is performed.

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

2, the image decoder 200 includes an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, prediction units 230 and 235, 240, and a memory 245 may be included.

When an image bitstream is input in the image encoder, the input bitstream may be decoded in a procedure opposite to that of the image encoder.

The entropy decoding unit 210 can perform entropy decoding in a procedure opposite to that in which entropy encoding is performed in the entropy encoding unit of the image encoder. For example, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be applied in accordance with the method performed by the image encoder. In the entropy decoding unit 210, the coefficients of the transform block include a flag indicating whether the absolute value of the coefficient is greater than 1 or not, a flag indicating whether the absolute value of the coefficient is greater than 1, And the like can be decoded. Then, the entropy decoding unit 210 decodes the coefficient code for non-zero coefficients. A coefficient whose absolute value is larger than 2 can be decoded by subtracting 2.

The entropy decoding unit 210 can decode information related to intra-picture prediction and inter-picture prediction performed by the encoder.

The reordering unit 215 can perform reordering based on a method in which the entropy decoding unit 210 rearranges 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 unit 215 can perform reordering by receiving 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 unit 220 can perform inverse quantization based on the quantization parameters provided by the encoder and the coefficient values of the re-arranged blocks.

The inverse transform unit 225 may inversely transform the dequantized transform coefficients using a predetermined transform method. At this time, the conversion method can be determined based on prediction method (inter-screen / intra-picture prediction), size / type of block, intra-picture prediction mode,

The prediction units 230 and 235 may generate a prediction block based on the prediction block generation related information provided by the entropy decoding unit 210 and the previously decoded block or image information provided in the memory 245. [

The prediction units 230 and 235 may include a prediction unit determination unit, an inter picture prediction unit, and an intra prediction unit. 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 identifies prediction units in the current coding unit , It is possible to determine whether the prediction unit performs inter-picture prediction or intra-picture prediction. The inter-picture predicting unit 230 may use the information necessary for the inter-picture prediction of the current prediction unit provided by the image encoder, based on the information included in at least one of the previous image or the following image of the current image including the current prediction unit The inter prediction can be performed on the current prediction unit. Alternatively, inter-picture prediction may be performed on the basis of the information of the partial-region reconstructed in the current image including the current prediction unit.

In order to perform inter-picture prediction, it is possible to determine whether a motion information generation method of a prediction unit included in the coding unit is generated based on a coding unit, such as a merge method or a motion estimation method.

The intra prediction unit 235 can generate a prediction block based on the pixel information in the current image. 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. The intra prediction unit 235 may include an Adaptive Intra Smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter performs filtering on the reference pixels of the current block and can 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 pixel of the current block using the prediction mode of the prediction unit provided in the image encoder and the AIS filter information. When the prediction mode of the current block is a mode in which AIS filtering is not performed, the AIS filter may not be applied.

The reference pixel interpolator may interpolate the reference pixels to generate reference pixels in units of pixels less than an integer value when the prediction mode of the prediction unit is a prediction unit that performs intra-frame prediction on the basis of the pixel value obtained by interpolating the reference pixels . The reference pixel may not be interpolated in the prediction mode in which the prediction mode of the current prediction unit generates the prediction block without interpolating the reference pixel. The DC filter can generate a prediction block through filtering when the prediction mode of the current block is the DC mode.

The restored block or image may be provided to the filter unit 240. The filter unit 240 may include a deblocking filter, an offset correction unit, and an ALF.

When information on whether a deblocking filter is applied to a corresponding block or an image from the image encoder or a deblocking filter is applied, information on whether a strong filter or a weak filter is applied can be provided. In the deblocking filter of the video decoder, the deblocking filter related information provided by the video encoder is provided, and the video decoder can perform deblocking filtering for 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, offset information, and the like during encoding.

The ALF can be applied to an encoding unit on the basis of ALF application information and ALF coefficient information provided from an encoder. Such ALF information may be provided in a specific set of parameters.

The memory 245 may store the reconstructed image or block to be used as a reference image or a reference block, and may provide the reconstructed image to the output unit.

5 is a diagram illustrating a brightness change pattern between a current image including a current block and a reference image.

In the case of inter-picture prediction for the current block, the greater the change in brightness between the current image and the reference image, the greater the change in brightness between the current block and the prediction block to be selected in the reference image. Therefore, it can be expected that as the error due to the inter-picture prediction of the current block increases, the energy for the residual signal of the current block also increases. And, as the energy for the residual signal increases, it can be expected that the error due to the quantization also increases. As a result, when there is a brightness change between the current image and the reference image, the error for the residual block will increase as compared to the case where there is no brightness change.

Accordingly, the present invention proposes a method of estimating a brightness change between images, generating a weight prediction parameter, and performing inter-view prediction using the weight prediction parameter. It is possible to prevent the energy of the residual block from increasing suddenly by using the weight prediction parameter in the inter-picture prediction for the prediction block.

The weight prediction parameter may be generated in consideration of a change in the brightness of the current image and the reference image, such as a fade-in or a fade-out. However, when the weight prediction parameter is determined by considering only the above factors, it is difficult to cope with the case where the brightness of the current image and the reference image are changed by a plurality of light sources or the brightness of only the local area in the current image changes. Accordingly, the present invention proposes a method of selectively using at least one of a plurality of weighted prediction parameters, thereby effectively performing inter-picture prediction even when the brightness changes by a plurality of light sources or when the brightness of only the local area changes I would like to suggest a way to do this.

Hereinafter, inter picture prediction using the weight prediction parameter will be described in detail with reference to the drawings.

6 is a flowchart showing a method of using a weight prediction parameter in an encoding apparatus.

The encoding apparatus can generate a set of weighted prediction parameters for the current block based on the weighted prediction parameters of the blocks coded before the current block to be coded (S601). Here, the weight prediction parameter set may include a weight prediction parameter of blocks in which inter-picture prediction is used, among the blocks encoded before the current block.

The encoding apparatus can generate a set of weighted prediction parameters based on the weighted prediction parameters used in neighboring blocks neighboring the current block among the blocks coded prior to the current block. Here, the neighboring block neighboring the current block may include a spatial neighboring block and a temporal neighboring block. For example, the spatial neighbor block may include a left upper block, an upper block, a right upper block, a left block, and a lower left block adjacent to a current block, and a temporally neighboring block of the current block may include a current block And a collocated block existing at the same position.

The encoding apparatus can construct a set of weight prediction parameters based on the weight prediction parameters for the reconstruction block encoded before the current block and the prediction block corresponding to the reconstruction block.

The weight prediction parameter may be set differently according to the inter-picture prediction direction. For example, the forward weighted prediction parameter may be used when a block to be coded is used for forward prediction, and the backward weighted prediction parameter may be used when a block to be coded performs backward prediction. When a block is encoded by performing bidirectional prediction, both a forward weighted prediction parameter and a backward weighted prediction parameter can be used. In this case, the forward direction indicates a reference image that is past the current image (i.e., a reference image having a POC smaller than the POC of the current image), and the reverse direction indicates a reference image that is the future of the current image Reference picture with a POC that is greater than POC).

The encoding apparatus can construct a weight prediction parameter set of the current block by using at least one of the forward weighted prediction parameter and the backward weighted prediction parameter for the neighboring block based on the inter-picture prediction direction of the current block.

7 is a diagram illustrating weight prediction parameters of neighboring blocks neighboring the current block.

In the example shown in FIG. 7, A to E denote the spatial neighboring blocks of the current block, and Col denotes the temporally neighboring block of the current block. Refer to the example shown in Fig. 4 for the positions of A to E and Col.

Referring to FIG. 7, neighboring blocks include at least one of a forward weighted prediction parameter (i.e., a weight parameter assigned to list 0) and a backward weighted prediction parameter (i.e., a weight parameter assigned to list 1) Lt; / RTI >

The encoding apparatus can determine a weight prediction parameter of neighboring blocks to be included in the weight prediction parameter set according to the prediction direction of the current block. For example, if the current block is coded using forward prediction, a set of weighted prediction parameters is constructed using forward weighted prediction parameters of neighboring blocks, and if the current block is coded through backward prediction, the inverse weight A predictive parameter set can be constructed using the predictive parameter. If the current block is coded using bidirectional prediction, a set of weighted prediction parameters can be constructed using the forward weighted prediction parameters and the backward weighted parameters of neighboring blocks.

For example, in the example shown in FIG. 7, if the current block is encoded with forward prediction, the forward weighted prediction parameters of the neighboring blocks are (65,1), (64,2), (66,2) (61, 7), (59, -2) may be included in the weight prediction parameter set.

Here, the weight prediction parameter may include at least one of a multiplication parameter multiplied by the prediction sample or an addition parameter added to the prediction sample. In FIG. 7, the weight prediction parameter is expressed in the form of (w, o). Where w denotes a multiplication parameter, and o denotes an addition parameter.

The encoding apparatus can select an optimal weight prediction parameter for the current block from the weight prediction parameters included in the weight prediction parameter set (S602). When the optimal weight prediction parameter for the current block is selected, the encoding apparatus can encode information (e.g., index information) specifying the selected weight prediction parameter.

When the optimal weight prediction parameter is selected, inter-picture prediction of the current block may be performed based on the selected weight prediction parameter (S603). For example, the inter-picture prediction of the current block can be performed by multiplying the prediction pixel obtained through motion compensation by the multiplication parameter, and then adding the addition parameter.

If a prediction block is generated as a result of the inter-picture prediction on the current block, the current block can be restored based on the generated prediction block and the residual block after the inverse quantization and inverse transform (S604).

Assuming that a block to be coded next to the current block is coded as an inter-picture prediction, a weight prediction parameter set of the next block may be generated using a weight prediction parameter of the current block. At this time, the weight prediction parameter of the current block usable in the next block may be any one selected from the weight prediction parameter set of the current block.

As another example, the weight prediction parameter of the current block available for the next block may be estimated from the restoration block and the prediction block of the current block. In this case, the encoding apparatus can perform a weighted prediction parameter estimation on the current block so as to configure a weighted prediction parameter set in the next block of the current block (S605).

The restoration block has a quantization error with respect to the original block, but the brightness change characteristic in the restoration block has a pattern similar to that of the original block. Accordingly, in the decoding apparatus, the weight prediction parameter for the current block can be estimated using the restoration block and the prediction block for the current block in order to estimate the weight prediction parameter in the same way as the encoding apparatus.

Specifically, if a restoration block is generated for the current block, the weight prediction parameter of the current block for the next block can be estimated by using the restoration block and the prediction block to which the weight prediction parameter is not applied. Equation (1) represents an example of a regression analysis model.

In Equation (1), Y represents the data of the reconstruction block, X represents the data of the prediction block, w represents the slope of the regression line, o represents the intercept value of the regression line, and e represents the error of the regression line prediction. Specifically, Y denotes a pixel value of a reconstruction block, and X denotes a pixel value of a prediction block.

The weight prediction parameter of the current block can be obtained by partially differentiating Equation 1 into w and o, respectively. For example, when the equation (1) is partially differentiated into w and o, w and o, which minimize the square of the error (e), can be derived as multiplication parameters and addition parameters, respectively.

The weight prediction parameter calculated based on Equation (1) may have a real value. The weight prediction parameter of the current block may be set to a real value calculated based on Equation (1) or may be set to a value obtained by integerizing a real value calculated based on Equation (1). In one example, the weighted prediction parameter may be derived as an integer value that is derived by multiplying a real number value calculated based on Equation (1) by ^2N . The variable N used for integerizing the weight prediction parameter can be encoded through the bit stream. Alternatively, by using the predetermined N value of the same value in the encoding apparatus and the decoding apparatus, the weight prediction parameter can be integerized.

In Equation (1), all the pixels in the reconstruction block are set to the input range for X, and all the pixels in the prediction block are set to the input range for Y. [ As another example, instead of using the pixels of the entire block, only some of the pixels through subsampling may be used to estimate the weight prediction parameters of the current block.

For example, FIG. 8 is a diagram for explaining an example in which only some of the pixels are used for the weight prediction parameter estimation of the current block. Assuming that the reconstruction block for the current block and the prediction block are subsampled by 1/2 in the horizontal and vertical directions, one of the four samples (2x2) may be used as the input of X or Y. [ For example, in the example shown in FIG. 8, only black pixels can be used for regression analysis.

In the example shown in FIG. 8, a sample located at the upper left of 2x2 samples is shown to be used for the regression analysis, but a right upper pixel, a left lower pixel, or a right lower pixel among 2x2 pixels may be set to be used for regression analysis . Alternatively, whether the regression analysis is used by using any of the four positions mentioned above may be encoded through a bitstream using an index.

The encoding apparatus and the decoding apparatus may perform subsampling according to a predefined value or perform subsampling according to a value derived under a predefined condition. Alternatively, the encoding apparatus may encode the sub-sampling unit M and encode the sub-sampling unit M through a bitstream, thereby notifying the decoding apparatus that sub-sampling has been performed by 1 / M.

The weighted prediction parameter estimated for the current block may be used to construct a set of weighted prediction parameters for the next block.

The maximum number of weight prediction parameters that can be included in the weight prediction parameter set of the current block may have a fixed number or may have a variable number depending on the size or type of the current block or the information signaled through the bit stream . For example, the maximum number P of maximum weight prediction parameters that the weight prediction parameter set may include may be encoded through the bit stream.

In Fig. 7, the blocks used for constructing the weight prediction parameter set of the current block are limited to A to E and Col, but blocks at other positions can also be used for constructing the weight prediction parameter set of the current block.

For example, the encoding apparatus may construct a weight prediction parameter set of a current block using a block at a predetermined position. Alternatively, the encoding device constructs a weight prediction parameter set of the current block using an arbitrary location block, and encodes information specifying the location or block of the block used for constructing the weight prediction parameter set of the current block through a bitstream You may. At this time, the information specifying the position of the block or the block can be encoded through the bit stream.

When the weight prediction parameter set includes a plurality of weight prediction parameters, the weight prediction parameters may be arranged in a predetermined order. In one example, the weight prediction parameters may be ordered in the order of the spatial neighbor block and the temporal neighbor block. Accordingly, in Fig. 7, after adding the weight prediction parameters A to E to the weight prediction parameter set, the weight prediction parameter of Col may be added to the weight prediction parameter set. As another example, the weight prediction parameters may be arranged in the order most similar to the motion information of the current block (for example, motion vectors). Alternatively, priority can be assigned to a weight prediction parameter set that has priority given to a weight prediction parameter derived based on a surrounding restoration block and its corresponding prediction block, and added to a weight prediction parameter set. On the other hand, To be added to the weight prediction parameter set.

The set of weighted prediction parameters may include an initial weighted prediction parameter set. The initial weight prediction parameter means that the multiplication parameter and the addition parameter are set to initial values. Here, the initial values of the multiplication parameter and the addition parameter may be 1 and 0, respectively. As another example, the initial value of the multiplication parameter may be set to 1 " N, and the initial value of the addition parameter may be set to zero.

The information on the initial weight prediction parameter may be encoded through a bitstream and transmitted to a decoder. Alternatively, the initial weight prediction parameter may be set to have a fixed index in the weight prediction parameter set. In one example, the initial weight prediction parameter may be set to have index 0 in the weight prediction parameter set.

The weight prediction parameter set may include a weight prediction parameter induced in an image unit. Here, the set of weight prediction parameters derived in units of images may be generated based on the change in brightness between the current image and the reference image of the current image. For example, the weight prediction parameter induced in an image unit may be derived by Equation (1). At this time, all the pixels in the current image are set to the input range for X, and all the pixels in the reference image can be set to the input range for Y. [

The information on the weight prediction parameter of the image unit can be encoded through the bit stream and transmitted to the decoder. Here, the information on the weight prediction parameter may include a weight prediction parameter value or a residual value for the weight prediction parameter. For example, in a decoder, a weight prediction parameter of an image unit can be obtained by adding a predictive value and a residual value of a weight prediction parameter. At this time, the predicted value of the weight prediction parameter is determined by the precision N for the current block, and the residual value can be determined based on the information to be decoded from the bit stream.

At this time, the precision N of the current block can be encoded through the bit stream and transmitted to the decoding apparatus through the bit stream.

Alternatively, it is also possible to determine the precision N of the current block in the same way in the encoding apparatus and the decoding apparatus. For example, the precision N of the current block may be determined adaptively according to the size, type, etc. of the current block.

When the image unit weight prediction parameter is included in the weight prediction parameter set, the index assigned to the image unit weight prediction parameter may be encoded through the bit stream or may have a predetermined value. Assuming, for example, that the set of weighted prediction parameters consists of a maximum of six weighted prediction parameters, the initial weighted prediction parameter may be set to have index 0, and the unitary weighted prediction parameter may be set to have index 1. Index 2 to index 5 may be used for the weight prediction parameter derived from the neighboring block.

The initial weight prediction parameter or the image unit weight prediction parameter may be added to the weight prediction parameter set when the number of weight prediction parameters derived from the neighboring block is smaller than the maximum number that can be included in the weight prediction parameter set. For example, if the number of weighted prediction parameters that can be used is four but the neighboring block neighboring the current block is coded by intra prediction or the current block is at the image boundary and the weighting prediction parameter of the neighboring block is not available , It is possible to include at least one of the initial weight prediction parameter or the image unit weight prediction parameter in the weight prediction parameter set if the four weight prediction parameters can not be derived from the neighboring block because of the reason.

The set of weighted prediction parameters may include a combined weighted prediction parameter generated by combining two or more weighted prediction parameters. For example, when the number of weight prediction parameters that can be derived from neighboring blocks is smaller than the number of usable weight prediction parameters, a combined weight prediction parameter generated by combining two or more weight prediction parameters is added to a weight prediction parameter set can do.

Assuming that the weight prediction parameter is composed of (w, o), the combined weight prediction parameter may be generated considering the prediction mode of neighboring blocks or the prediction direction of neighboring blocks.

For example, FIG. 9 shows an example in which combined weighted prediction parameters are generated.

In FIG. 9, A to D denote neighboring blocks neighboring the current block, and List 0 and 1 denote weighting prediction parameters of a neighboring block when a forward reference image and a backward reference image are used, respectively.

In FIG. 9, A is shown to have only a forward weighted prediction parameter as it performs forward prediction, and D has only a backward weighted prediction parameter as it performs backward prediction. C is shown to have both a forward weighted prediction parameter and a backward weighted prediction parameter as performing bidirectional prediction. B is shown to have neither forward weighted prediction parameters nor backward weighted prediction parameters. In one example, if B is coded with intra prediction, then B will not have a weight prediction parameter.

Accordingly, in the example shown in Fig. 9, the forward weighted prediction parameter (i.e., the weighted prediction parameter for List 0) is obtained only from the A and C blocks and the backward weighted prediction parameter ) Can only be obtained from the C and D blocks.

Assuming that the set of weighted prediction parameters of the current block can include four forward weighted prediction parameters, the remaining two forward weighted prediction parameters, excluding the two forward weighted prediction parameters derived from the neighboring block, Parameters. ≪ / RTI > Alternatively, if it is assumed that the set of weighted prediction parameters of the current block may include four backward weighted prediction parameters, the remaining two backward weighted prediction parameters, excluding the two backward weighted parameters derived from the neighboring block, Parameters. ≪ / RTI > In Fig. 9, the forward weighted prediction parameters of A and C are combined, the forward weighted prediction parameters of B and D are generated, and the backward weighted prediction parameters of C and D are combined to generate the backward weighted prediction parameters of A and B .

When the combined weight prediction parameter is added to the weight prediction parameter set, the index given to the combined weight prediction parameter may be determined by a predetermined priority.

If all of the weighted prediction parameter sets are not generated despite the combination of the weighted prediction parameters in the neighboring block, all of the remaining weighted prediction parameters can be set as the initial weighted prediction parameters.

10 shows an example of decoding a weight prediction parameter in the decoding apparatus. 10, the decoding apparatus may generate a set of weighted prediction parameters based on weighted prediction parameters of neighboring blocks neighboring the current block among the decoded blocks preceding the current block (S1001). The generation of the weighted prediction parameter set has been described in detail in the operation of the encoding apparatus, and a detailed description thereof will be omitted.

When the weight prediction parameter set for the current block is configured, the decoding apparatus can determine the weight prediction parameter for the current block based on the index information specifying any one of the weight prediction parameters included in the weight prediction parameter set (S1002 ). Here, the index information can be decoded from the bitstream.

When the weight prediction parameter for the current block is determined, the inter-screen prediction for the current block can be performed using the determined weight prediction parameter (S1003). As an example, inter-picture prediction of a current block can be performed by multiplying a prediction sample obtained through motion compensation by a multiplication parameter and then adding an addition parameter.

If a prediction block is generated as an inter-picture prediction result for the current block, the current block can be restored based on the generated prediction block and the residual block (S1004).

When the restoration of the current block is completed, the weight prediction parameter for the current block can be estimated so that the block to be decoded next to the current block can be used (S1005). Estimation of the weight prediction parameter set of the current block has been described in detail in the operation of the encoding apparatus, and a detailed description thereof will be omitted.

Although the exemplary methods of this disclosure are represented by a series of acts for clarity of explanation, they are not intended to limit the order in which the steps are performed, and if necessary, each step may be performed simultaneously or in a different order. In order to implement the method according to the present disclosure, the illustrative steps may additionally include other steps, include the remaining steps except for some steps, or may include additional steps other than some steps.

The various embodiments of the disclosure are not intended to be all-inclusive and are intended to illustrate representative aspects of the disclosure, and the features described in the various embodiments may be applied independently or in a combination of two or more.

In addition, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. In the case of hardware implementation, one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays A general processor, a controller, a microcontroller, a microprocessor, and the like.

The scope of the present disclosure is to be accorded the broadest interpretation as understanding of the principles of the invention, as well as software or machine-executable instructions (e.g., operating system, applications, firmware, Instructions, and the like are stored and are non-transitory computer-readable medium executable on the device or computer.

Claims (10)

Generating a set of weighted prediction parameters for the current block based on a weighted prediction parameter of a neighboring block neighboring the current block;
Determining a weight prediction parameter for the current block based on the weight prediction parameter set and the index information; And
And performing inter-picture prediction on the current block using a weight prediction parameter of the current block. The method according to claim 1,
Wherein the weight prediction parameter set is generated based on at least one of a forward weighted prediction parameter of the neighboring block or a backward weighted prediction parameter of the neighboring block according to a prediction direction of the current block. 3. The method of claim 2,
Wherein if the prediction direction of the current block is bidirectional, the weight prediction parameter set includes both the forward weighted prediction parameter of the neighboring block and the backward weighted prediction parameter of the neighboring block. The method according to claim 1,
When the number of weight prediction parameters obtainable from the neighboring block is smaller than the number of maximum weight prediction parameters that can be included in the weight prediction parameter set, the weight prediction parameter set is a combination of weight prediction parameters of the neighboring blocks And generating a combined weighted prediction parameter by generating a combined weighted prediction parameter. The method according to claim 1,
Wherein a plurality of weight prediction parameters included in the weight prediction parameter set are arranged in a predefined order. Generating a set of weighted prediction parameters for the current block based on a weighted prediction parameter of a neighboring block neighboring the current block;
Determining a weight prediction parameter for the current block based on the weight prediction parameter set; And
And encoding index information specifying the determined weight prediction parameter. The method according to claim 6,
Wherein the weight prediction parameter set is generated based on at least one of a forward weighted prediction parameter of the neighboring block or an inverse weighted prediction parameter of the neighboring block according to a prediction direction of the current block. 8. The method of claim 7,
Wherein when the prediction direction of the current block is bidirectional, the weight prediction parameter set includes both the forward weighted prediction parameter of the neighboring block and the backward weighted prediction parameter of the neighboring block. The method according to claim 6,
When the number of weight prediction parameters obtainable from the neighboring block is smaller than the number of maximum weight prediction parameters that can be included in the weight prediction parameter set, the weight prediction parameter set is a combination of weight prediction parameters of the neighboring blocks And generating a combined weighted prediction parameter based on the combined weighted prediction parameter. The method according to claim 6,
Wherein a plurality of weight prediction parameters included in the weight prediction parameter set are arranged in a predefined order.

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