WO2015060642A1 - Méthode et appareil d'encodage/de décodage de signal vidéo à multiples couches - Google Patents

Méthode et appareil d'encodage/de décodage de signal vidéo à multiples couches Download PDF

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Publication number
WO2015060642A1
WO2015060642A1 PCT/KR2014/009955 KR2014009955W WO2015060642A1 WO 2015060642 A1 WO2015060642 A1 WO 2015060642A1 KR 2014009955 W KR2014009955 W KR 2014009955W WO 2015060642 A1 WO2015060642 A1 WO 2015060642A1
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layer
prediction
tile
picture
inter
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PCT/KR2014/009955
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English (en)
Korean (ko)
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이배근
김주영
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주식회사 케이티
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Priority claimed from KR20140142461A external-priority patent/KR20150046742A/ko
Application filed by 주식회사 케이티 filed Critical 주식회사 케이티
Priority to CN201480058386.XA priority Critical patent/CN105659596A/zh
Priority to US15/029,622 priority patent/US10045020B2/en
Priority to MX2016005198A priority patent/MX364015B/es
Publication of WO2015060642A1 publication Critical patent/WO2015060642A1/fr
Priority to US16/006,104 priority patent/US10602136B2/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards

Definitions

  • the present invention relates to a method and apparatus for encoding / decoding multilayer video signals.
  • High efficiency image compression techniques can be used to solve these problems caused by high resolution and high quality image data.
  • An inter-screen prediction technique for predicting pixel values included in the current picture from a picture before or after the current picture using an image compression technique an intra prediction technique for predicting pixel values included in a current picture using pixel information in the current picture
  • An object of the present invention is to provide a method and apparatus for determining an interlayer reference picture of a current picture of a higher layer in encoding / decoding a multilayer video signal.
  • An object of the present invention is to provide a method and apparatus for upsampling a picture of a lower layer in encoding / decoding a multilayer video signal.
  • An object of the present invention is to provide a method and apparatus for effectively deriving texture information of a higher layer through inter-layer prediction in encoding / decoding a multilayer video signal.
  • An object of the present invention is to provide an inter-layer prediction method and apparatus based on inter-layer tile alignment in encoding / decoding a multilayer video signal.
  • the method and apparatus for decoding a multilayer video signal determine a corresponding picture belonging to a lower layer used for inter-layer prediction of a current picture belonging to an upper layer, and use the current picture using the determined corresponding picture of the lower layer.
  • the inter-layer prediction of the picture is performed.
  • the inter-layer prediction is limited according to a tile boundary alignment flag indicating whether tiles are aligned between the upper layer and the lower layer.
  • the corresponding picture belonging to the lower layer is determined based on interlayer reference information of the current picture.
  • the interlayer reference information may include at least one of an interlayer prediction flag, information on the number of reference pictures, and a reference layer identifier.
  • the value of the tile boundary alignment flag is 1, if two samples of the current picture belonging to the upper layer belong to one tile, If two samples of the corresponding picture belonging to the same tile belong to one tile, and two samples of the current picture belonging to the upper layer belong to different tiles, the two samples of the corresponding picture belonging to the lower layer also belong to different tiles. It is characterized by belonging.
  • the tile boundary alignment flag may be obtained on a limited basis based on the number of tiles of the current picture.
  • the method and apparatus for encoding a multi-layer video signal according to the present invention may determine a corresponding picture belonging to a lower layer used for inter-layer prediction of a current picture belonging to an upper layer, and use the current picture by using the determined corresponding picture of the lower layer.
  • the inter-layer prediction of the picture is performed.
  • the inter-layer prediction is limited according to a tile boundary alignment flag indicating whether tiles are aligned between the upper layer and the lower layer.
  • the corresponding picture belonging to the lower layer is determined based on interlayer reference information of the current picture.
  • the interlayer reference information may include at least one of an interlayer prediction flag, information about the number of reference pictures, and a reference layer identifier.
  • the value of the tile boundary alignment flag is 1, if two samples of the current picture belonging to the upper layer belong to one tile, If two samples of the corresponding picture belonging to the same tile belong to one tile, and two samples of the current picture belonging to the upper layer belong to different tiles, the two samples of the corresponding picture belonging to the lower layer also belong to different tiles. It is characterized by belonging.
  • the tile boundary alignment flag may be obtained on a limited basis based on the number of tiles of the current picture.
  • the memory can be effectively managed by adaptively using the picture of the lower layer as the inter-layer reference picture of the current picture of the upper layer.
  • texture information of an upper layer can be effectively derived through inter-layer prediction.
  • coding efficiency of a video signal can be improved by performing inter-layer prediction based on inter-layer tile alignment in a multilayer structure.
  • FIG. 1 is a block diagram schematically illustrating an encoding apparatus according to an embodiment of the present invention.
  • FIG. 2 is a block diagram schematically illustrating a decoding apparatus according to an embodiment of the present invention.
  • FIG. 3 is a flowchart illustrating a process of performing inter-layer prediction of an upper layer using a corresponding picture of a lower layer according to an embodiment to which the present invention is applied.
  • FIG. 4 illustrates a method of determining a corresponding picture of a lower layer based on a reference active flag according to an embodiment to which the present invention is applied.
  • FIG. 5 illustrates a method of acquiring interlayer reference information about a current picture according to an embodiment to which the present invention is applied.
  • FIG. 6 illustrates a syntax table of interlayer reference information according to an embodiment to which the present invention is applied.
  • FIG. 7 illustrates a relationship between slices and tiles as an embodiment to which the present invention is applied.
  • FIG. 8 illustrates a method of performing inter-layer prediction using tile alignment between multi-layers as an embodiment to which the present invention is applied.
  • FIG. 9 illustrates a method for adaptively performing inter-layer tile alignment based on a discardable flag as an embodiment to which the present invention is applied.
  • 10 to 12 illustrate a method of adaptively performing inter-layer tile alignment based on a temporal ID (TemporalID) of a lower layer as an embodiment to which the present invention is applied.
  • TempooralID Temporal ID
  • FIG. 13 is a flowchart illustrating a method of performing inter-layer prediction limited according to whether tiles between layers are aligned according to an embodiment to which the present invention is applied.
  • 14 to 16 illustrate syntax of a tile boundary alignment flag according to an embodiment to which the present invention is applied.
  • 17 is a flowchart illustrating a method of upsampling a corresponding picture of a lower layer according to an embodiment to which the present invention is applied.
  • the method and apparatus for decoding a multilayer video signal determine a corresponding picture belonging to a lower layer used for inter-layer prediction of a current picture belonging to an upper layer, and use the current picture using the determined corresponding picture of the lower layer.
  • the inter-layer prediction of the picture is performed.
  • the corresponding picture belonging to the lower layer is determined based on interlayer reference information of the current picture.
  • the interlayer reference information may include at least one of an interlayer prediction flag, information on the number of reference pictures, and a reference layer identifier.
  • the value of the tile boundary alignment flag is 1, if two samples of the current picture belonging to the upper layer belong to one tile, If two samples of the corresponding picture belonging to the same tile belong to one tile, and two samples of the current picture belonging to the upper layer belong to different tiles, the two samples of the corresponding picture belonging to the lower layer also belong to different tiles. It is characterized by belonging.
  • the tile boundary alignment flag may be obtained on a limited basis based on the number of tiles of the current picture.
  • the method and apparatus for encoding a multi-layer video signal according to the present invention may determine a corresponding picture belonging to a lower layer used for inter-layer prediction of a current picture belonging to an upper layer, and use the current picture by using the determined corresponding picture of the lower layer.
  • the inter-layer prediction of the picture is performed.
  • the inter-layer prediction is limited according to a tile boundary alignment flag indicating whether tiles are aligned between the upper layer and the lower layer.
  • the corresponding picture belonging to the lower layer is determined based on interlayer reference information of the current picture.
  • the interlayer reference information may include at least one of an interlayer prediction flag, information about the number of reference pictures, and a reference layer identifier.
  • the value of the tile boundary alignment flag is 1, if two samples of the current picture belonging to the upper layer belong to one tile, If two samples of the corresponding picture belonging to the same tile belong to one tile, and two samples of the current picture belonging to the upper layer belong to different tiles, the two samples of the corresponding picture belonging to the lower layer also belong to different tiles. It is characterized by belonging.
  • the tile boundary alignment flag may be obtained on a limited basis based on the number of tiles of the current picture.
  • first and second may be used to describe various configurations, but the configurations are not limited by the terms. The terms are used to distinguish one configuration from another.
  • first configuration may be referred to as the second configuration, and similarly, the second configuration may also be referred to as the first configuration.
  • each component shown in the embodiments of the present invention are independently shown to represent different characteristic functions, and do not mean that each component is made of separate hardware or one software component unit.
  • each component is listed as a component for convenience of description, and at least two of the components may form one component, or one component may be divided into a plurality of components to perform a function.
  • the integrated and separated embodiments of each component are also included in the scope of the present invention without departing from the spirit of the present invention.
  • the components may not be essential components for performing essential functions in the present invention, but may be optional components for improving performance.
  • the present invention can be implemented including only the components essential for implementing the essentials of the present invention except for the components used for improving performance, and the structure including only the essential components except for the optional components used for improving performance. Also included in the scope of the present invention.
  • Encoding and decoding of video that supports multiple layers in a bitstream is called scalable video coding. Since there is a strong correlation between the plurality of layers, the prediction may be performed by using this correlation to remove redundant elements of data and to improve encoding performance of an image. Performing prediction of the current layer using information of another layer is referred to as inter-layer prediction or inter-layer prediction in the following.
  • the plurality of layers may have different resolutions, where the resolution may mean at least one of spatial resolution, temporal resolution, and image quality. Resampling such as up-sampling or downsampling of a layer may be performed to adjust the resolution during inter-layer prediction.
  • FIG. 1 is a block diagram schematically illustrating an encoding apparatus according to an embodiment of the present invention.
  • the encoding apparatus 100 includes an encoder 100a for an upper layer and an encoder 100b for a lower layer.
  • the upper layer may be expressed as a current layer or an enhancement layer
  • the lower layer may be expressed as an enhancement layer, a base layer, or a reference layer having a lower resolution than the upper layer.
  • the upper layer and the lower layer may have at least one of a spatial resolution, a temporal resolution according to a frame rate, and an image quality according to a color format or a quantization size. When a resolution change is necessary to perform inter-layer prediction, upsampling or downsampling of a layer may be performed.
  • the encoder 100a of the upper layer may include a divider 110, a predictor 120, a transformer 130, a quantizer 140, a reorderer 150, an entropy encoder 160, and an inverse quantizer ( 170, an inverse transform unit 180, a filter unit 190, and a memory 195.
  • the encoder 100b of the lower layer includes a divider 111, a predictor 125, a transformer 131, a quantizer 141, a reordering unit 151, an entropy encoder 161, and an inverse quantizer ( 171, an inverse transform unit 181, a filter unit 191, and a memory 196.
  • the encoder may be implemented by the image encoding method described in the following embodiments of the present invention, but operations in some components may not be performed to reduce the complexity of the encoding apparatus or for fast real time encoding.
  • some limited number of methods are used without selecting the optimal intra intra coding method using all intra prediction modes in order to perform encoding in real time.
  • a method of selecting one intra prediction mode among them as a final intra prediction mode using the intra prediction mode of the image may be used.
  • the unit of a block processed by the encoding apparatus may be a coding unit that performs encoding, a prediction unit that performs prediction, or a transformation unit that performs transformation.
  • a coding unit may be represented by a term such as a coding unit (CU), a prediction unit is a prediction unit (PU), and a transformation unit is a transform unit (TU).
  • the splitters 110 and 111 divide a layer image into a combination of a plurality of coding blocks, prediction blocks, and transform blocks, and one of the coding blocks, prediction blocks, and transform blocks according to a predetermined criterion (for example, a cost function). You can split the layer by selecting the combination of. For example, to split a coding unit in a layer image, a recursive tree structure such as a quad tree structure may be used.
  • a recursive tree structure such as a quad tree structure may be used.
  • the meaning of the coding block may be used not only as a block for encoding but also as a block for decoding.
  • the prediction block may be a unit for performing prediction such as intra prediction or inter prediction.
  • the block for performing intra prediction may be a block having a square shape such as 2N ⁇ 2N or N ⁇ N.
  • As a block for performing inter prediction there is a prediction block partitioning method using Asymmetric Motion Partitioning (AMP), which is a square form such as 2Nx2N and NxN, or a rectangular form or asymmetric form such as 2NxN and Nx2N.
  • AMP Asymmetric Motion Partitioning
  • the transform unit 115 may change a method of performing the transform.
  • the prediction units 120 and 125 of the encoders 100a and 100b may include the intra prediction units 121 and 126 performing intra prediction and the inter prediction unit performing inter prediction. (122, 127).
  • the predictor 120 of the higher layer encoder 100a may further include an inter-layer predictor 123 that performs prediction on the higher layer by using information of the lower layer.
  • the prediction units 120 and 125 may determine whether to use inter prediction or intra prediction on the prediction block.
  • the process of determining the intra prediction mode in units of prediction blocks and performing the intra prediction based on the determined intra prediction mode may be performed in units of transform blocks.
  • the residual value (residual block) between the generated prediction block and the original block may be input to the transformers 130 and 131.
  • prediction mode information and motion information used for prediction may be encoded by the entropy encoder 130 together with the residual value and transmitted to the decoding apparatus.
  • the original block may be encoded as it is and transmitted to the decoder without performing prediction through the prediction units 120 and 125.
  • PCM Pulse Coded Modulation
  • the intra prediction units 121 and 126 may generate an intra prediction block based on reference pixels present around the current block (the block to be predicted).
  • the intra prediction mode may have a directional prediction mode using a reference pixel according to a prediction direction and a non-directional mode without considering the prediction direction.
  • the mode for predicting luma information and the mode for predicting color difference information may be different.
  • an intra prediction mode in which luma information is predicted or predicted luma information may be used. If the reference pixel is not available, the unusable reference pixel may be replaced with another pixel, and a prediction block may be generated using the reference pixel.
  • the prediction block may include a plurality of transform blocks. If the prediction block has the same size as the transform block when the intra prediction is performed, pixels present on the left side of the prediction block, pixels present on the upper left side, and top Intra-prediction of the prediction block may be performed based on the pixels present in the. However, when the prediction block is different from the size of the transform block when the intra prediction is performed, and a plurality of transform blocks are included in the prediction block, intra prediction is performed by using neighboring pixels adjacent to the transform block as reference pixels. Can be done.
  • the neighboring pixel adjacent to the transform block may include at least one of the neighboring pixel adjacent to the prediction block and the pixels already decoded in the prediction block.
  • the intra prediction method may generate a prediction block after applying a mode dependent intra smoothing (MDIS) filter to a reference pixel according to the intra prediction mode.
  • MDIS mode dependent intra smoothing
  • the type of MDIS filter applied to the reference pixel may be different.
  • the MDIS filter is an additional filter applied to the predicted block in the picture by performing the intra prediction and may be used to reduce the residual present in the predicted block in the picture generated after performing the prediction with the reference pixel.
  • filtering on a reference pixel and some columns included in the predicted block in the screen may perform different filtering according to the direction of the intra prediction mode.
  • the inter prediction units 122 and 127 may perform prediction by referring to information of a block included in at least one of a previous picture or a subsequent picture of the current picture.
  • the inter prediction units 122 and 127 may include a reference picture interpolator, a motion predictor, and a motion compensator.
  • the reference picture interpolation unit may receive reference picture information from the memories 195 and 196 and generate pixel information of an integer pixel or less in the reference picture.
  • a DCT-based 8-tap interpolation filter having different filter coefficients may be used to generate pixel information of integer pixels or less in units of 1/4 pixels.
  • a DCT-based interpolation filter having different filter coefficients may be used to generate pixel information of an integer pixel or less in units of 1/8 pixels.
  • the inter prediction units 122 and 127 may perform motion prediction based on the reference picture interpolated by the reference picture interpolator.
  • various methods such as a full search-based block matching algorithm (FBMA), a three step search (TSS), and a new three-step search algorithm (NTS) may be used.
  • the motion vector may have a motion vector value of 1/2 or 1/4 pixel units based on the interpolated pixels.
  • the inter prediction units 122 and 127 may perform prediction on the current block by applying one inter prediction method among various inter prediction methods.
  • various methods such as a skip method, a merge method, and a motion vector predictor (MVP), may be used as the inter prediction method.
  • MVP motion vector predictor
  • motion information that is, information such as a reference index, a motion vector, and a residual signal
  • motion information is entropy coded and transmitted to a decoder.
  • the skip mode since the residual signal is not generated, the conversion and quantization processes for the residual signal may be omitted.
  • the interlayer prediction unit 123 performs interlayer prediction for predicting an upper layer by using information of a lower layer.
  • the inter-layer prediction unit 123 may perform inter-layer prediction using texture information, motion information, etc. of the lower layer.
  • prediction of a current block of an upper layer may be performed using motion information on a picture of a lower layer (reference layer) using a picture of a lower layer as a reference picture.
  • the picture of the reference layer used as the reference picture in inter-layer prediction may be a picture sampled according to the resolution of the current layer.
  • the motion information may include a motion vector and a reference index. In this case, the value of the motion vector for the picture of the reference layer may be set to (0,0).
  • the inter-layer prediction unit 123 may perform inter-layer texture prediction, inter-layer motion prediction, inter-layer syntax prediction, and inter-layer difference prediction.
  • Inter-layer texture prediction may derive the texture of the current layer based on the texture of the reference layer.
  • the texture of the reference layer may be sampled according to the resolution of the current layer, and the inter-layer predictor 123 may predict the texture of the current layer based on the sampled texture of the reference layer.
  • Inter-layer motion prediction may derive the motion vector of the current layer based on the motion vector of the reference layer.
  • the motion vector of the reference layer may be scaled according to the resolution of the current layer.
  • the syntax of the current layer may be predicted based on the syntax of the reference layer.
  • the inter-layer prediction unit 123 may use the syntax of the reference layer as the syntax of the current layer.
  • the picture of the current layer may be reconstructed using the difference between the reconstructed image of the reference layer and the reconstructed image of the current layer.
  • a residual block including residual information which is a difference between the predicted block generated by the predictors 120 and 125 and the reconstructed block of the predicted block, is generated, and the residual block is input to the transformers 130 and 131.
  • the transform units 130 and 131 may transform the residual block using a transform method such as a discrete cosine transform (DCT) or a discrete sine transform (DST). Whether DCT or DST is applied to transform the residual block may be determined based on intra prediction mode information of the prediction block used to generate the residual block and size information of the prediction block. That is, the transformers 130 and 131 may apply the transformation method differently according to the size of the prediction block and the prediction method.
  • a transform method such as a discrete cosine transform (DCT) or a discrete sine transform (DST).
  • DCT discrete cosine transform
  • DST discrete sine transform
  • the quantizers 140 and 141 may quantize the values transformed by the transformers 130 and 131 into the frequency domain.
  • the quantization coefficient may change depending on the block or the importance of the image.
  • the values calculated by the quantizers 140 and 141 may be provided to the dequantizers 170 and 17 and the reordering units 150 and 151.
  • the reordering units 150 and 151 may reorder coefficient values with respect to the quantized residual value.
  • the reordering units 150 and 151 may change the two-dimensional block shape coefficients into a one-dimensional vector form through a coefficient scanning method.
  • the realignment units 150 and 151 may scan DC coefficients to coefficients in the high frequency region by using a Zig-Zag scan method and change them into one-dimensional vectors.
  • a vertical scan method for scanning two-dimensional block shape coefficients in a column direction, not a zig-zag scan method, and a horizontal scan method for scanning two-dimensional block shape coefficients in a row direction Can be used. That is, according to the size of the transform block and the intra prediction mode, it is possible to determine which scan method among zigzag-scan, vertical scan and horizontal scan is used.
  • the entropy encoders 160 and 161 may perform entropy encoding based on the values calculated by the reordering units 150 and 151. Entropy encoding may use various encoding methods such as, for example, Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC).
  • Exponential Golomb Context-Adaptive Variable Length Coding
  • CABAC Context-Adaptive Binary Arithmetic Coding
  • the entropy encoders 160 and 161 transmit residual value coefficient information, block type information, prediction mode information, partition unit information, prediction block information, and the like of the coding block from the reordering units 150 and 151 and the prediction units 120 and 125. Entropy encoding may be performed based on a predetermined encoding method by receiving various information such as unit information, motion information, reference frame information, block interpolation information, and filtering information. In addition, the entropy encoder 160 or 161 may entropy-encode coefficient values of coding units input from the reordering unit 150 or 151.
  • the entropy encoders 160 and 161 may encode the intra prediction mode information of the current block by performing binarization on the intra prediction mode information.
  • the entropy encoder 160 or 161 may include a codeword mapping unit for performing such a binarization operation, and may perform different binarization according to the size of a prediction block for performing intra prediction.
  • the codeword mapping unit the codeword mapping table may be adaptively generated or stored in advance through a binarization operation.
  • the entropy encoders 160 and 161 may express prediction mode information in the current screen using a codenum mapping unit for performing codenum mapping and a codeword mapping unit for performing codeword mapping. In the codenum mapping unit and the codeword mapping unit, a codenum mapping table and a codeword mapping table may be generated or stored.
  • the inverse quantizers 170 and 171 and the inverse transformers 180 and 181 inverse quantize the quantized values in the quantizers 140 and 141 and inversely transform the converted values in the transformers 130 and 131.
  • the residual values generated by the inverse quantizers 170 and 171 and the inverse transformers 180 and 181 may be predicted by the motion estimator, the motion compensator, and the intra prediction unit included in the predictors 120 and 125. It may 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 correction unit.
  • the deblocking filter may remove block distortion caused by boundaries between blocks in the reconstructed picture.
  • it may be determined whether to apply a deblocking filter to the current block based on the pixels included in several columns or rows included in the block.
  • a strong filter or a weak filter may be applied according to the required deblocking filtering strength.
  • horizontal filtering and vertical filtering may be performed in parallel when vertical filtering and horizontal filtering are performed.
  • the offset correction unit may correct the offset with respect to the original image on a pixel-by-pixel basis for the deblocking image.
  • the pixels included in the image are divided into predetermined areas, and then, the area to be offset is determined and the offset is applied to the corresponding area, or the offset is applied considering the edge information of each pixel. Can be used.
  • the filter units 190 and 191 may apply only the deblocking filter or both the deblocking filter and the offset correction without applying both the deblocking filter and the offset correction.
  • the memories 195 and 196 may store reconstructed blocks or pictures calculated by the filters 190 and 191, and the stored reconstructed blocks or pictures may be provided to the predictors 120 and 125 when performing inter prediction. have.
  • the information output from the entropy encoder 100b of the lower layer and the information output from the entropy encoder 100a of the upper layer may be multiplexed by the MUX 197 and output as a bitstream.
  • the MUX 197 may be included in the encoder 100a of the upper layer or the encoder 100b of the lower layer, or may be implemented as an independent device or module separate from the encoder 100.
  • FIG. 2 is a block diagram schematically illustrating a decoding apparatus according to an embodiment of the present invention.
  • the decoding apparatus 200 includes a decoder 200a of an upper layer and a decoder 200b of a lower layer.
  • the decoder 200a of the upper layer includes an entropy decoder 210, a reordering unit 220, an inverse quantization unit 230, an inverse transform unit 240, a prediction unit 250, a filter unit 260, and a memory 270. ) May be included.
  • the lower layer decoding unit 200b includes an entropy decoding unit 211, a reordering unit 221, an inverse quantization unit 231, an inverse transform unit 241, a prediction unit 251, a filter unit 261, and a memory 271. ) May be included.
  • the DEMUX 280 may demultiplex information for each layer and transmit the information to the decoders 200a and 200b for each layer.
  • the input bitstream may be decoded in a procedure opposite to that of the encoding apparatus.
  • the entropy decoders 210 and 211 may perform entropy decoding in a procedure opposite to that of the entropy encoder in the encoding apparatus.
  • Information for generating a prediction block among the information decoded by the entropy decoders 210 and 211 is provided to the predictors 250 and 251, and the residual value obtained by entropy decoding by the entropy decoders 210 and 211 is a reordering unit. It may be input to (220, 221).
  • the entropy decoders 210 and 211 may use at least one of CABAC and CAVLC.
  • the entropy decoders 210 and 211 may decode information related to intra prediction and inter prediction performed by the encoding apparatus.
  • the entropy decoder 210 or 211 may include a codeword mapping unit and include a codeword mapping table for generating a received codeword as an intra prediction mode number.
  • the codeword mapping table may be stored in advance or generated adaptively.
  • a codenum mapping unit for performing codenum mapping may be additionally provided.
  • the reordering units 220 and 221 may reorder the bitstreams entropy decoded by the entropy decoding units 210 and 211 based on a method of rearranging the bitstreams by the encoder. Coefficients expressed in the form of a one-dimensional vector may be reconstructed by reconstructing the coefficients in a two-dimensional block form.
  • the reordering units 220 and 221 may be realigned by receiving information related to coefficient scanning performed by the encoder and performing reverse scanning based on the scanning order performed by the corresponding encoder.
  • the inverse quantization units 230 and 231 may perform inverse quantization based on quantization parameters provided by the encoding apparatus and coefficient values of the rearranged block.
  • the inverse transformers 240 and 241 may perform inverse DCT or inverse DST on the DCT or DST performed by the transformers 130 and 131 with respect to the quantization result performed by the encoding apparatus.
  • the inverse transform may be performed based on a transmission unit determined by the encoding apparatus.
  • the DCT and the DST may be selectively performed by the transform unit of the encoding apparatus according to a plurality of pieces of information, such as a prediction method, a size of the current block, and a prediction direction.
  • the inverse transformers 240 and 241 of the decoding apparatus may convert Inverse transformation may be performed based on the performed transformation information. When the transform is performed, the transform may be performed based on the coding block rather than the transform block.
  • the prediction units 250 and 251 may generate the prediction blocks based on the prediction block generation related information provided by the entropy decoding units 210 and 211 and previously decoded blocks or picture information provided by the memories 270 and 271. .
  • the predictors 250 and 251 may include a prediction unit determiner, an inter prediction unit, and an intra prediction unit.
  • the prediction unit discriminator receives various information such as prediction unit information input from the entropy decoder, prediction mode information of the intra prediction method, and motion prediction related information of the inter prediction method, and distinguishes the prediction block from the current coding block. It is possible to determine whether to perform this inter prediction or intra prediction.
  • the inter prediction unit uses information required for inter prediction of the current prediction block provided by the encoding apparatus to the current prediction block based on information included in at least one of a previous picture or a subsequent picture of the current picture including the current prediction block. Inter prediction can be performed.
  • a motion prediction method of a prediction block included in a coding block based on a coding block uses a skip mode, a merge mode, a motion vector predictor (MVP) (AMVP). Mode) can be determined.
  • the intra prediction unit may generate a prediction block based on the reconstructed pixel information in the current picture.
  • intra prediction may be performed based on intra prediction mode information of the prediction block provided by the encoding apparatus.
  • the intra prediction unit is an MDIS filter that performs filtering on the reference pixel of the current block, a reference pixel interpolator that generates a reference pixel of an integer value or less by interpolating the reference pixel, and filters when the prediction mode of the current block is DC mode. It may include a DC filter for generating a prediction block through.
  • the predictor 250 of the upper layer decoder 200a may further include an inter-layer predictor that performs inter-layer prediction for predicting an upper layer by using information of the lower layer.
  • the inter-layer prediction unit may perform inter-layer prediction using intra prediction mode information and motion information.
  • prediction of a current block of an upper layer may be performed using motion information of a lower layer (reference layer) picture using a picture of a lower layer as a reference picture.
  • the picture of the reference layer used as the reference picture in inter-layer prediction may be a picture sampled according to the resolution of the current layer.
  • the motion information may include a motion vector and a reference index.
  • the value of the motion vector for the picture of the reference layer may be set to (0,0).
  • inter-layer prediction 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 may derive the texture of the current layer based on the texture of the reference layer.
  • the texture of the reference layer may be sampled according to the resolution of the current layer, and the inter-layer predictor may predict the texture of the current layer based on the sampled texture.
  • Inter-layer motion prediction may derive the motion vector of the current layer based on the motion vector of the reference layer. In this case, the motion vector of the reference layer may be scaled according to the resolution of the current layer.
  • the syntax of the current layer may be predicted based on the syntax of the reference layer.
  • the inter-layer prediction unit 123 may use the syntax of the reference layer as the syntax of the current layer.
  • the picture of the current layer may be reconstructed using the difference between the reconstructed image of the reference layer and the reconstructed 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.
  • the deblocking filter of the decoding apparatus may receive the deblocking filter related information provided by the encoding apparatus and perform the deblocking filtering on the corresponding block in the decoding apparatus.
  • the offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction and offset value information applied to the image during encoding.
  • the memories 270 and 271 may store the reconstructed picture or block to be used as the reference picture or the reference block, and output the reconstructed picture.
  • the encoding apparatus and the decoding apparatus may encode three or more layers instead of two layers.
  • a plurality of encoders for a higher layer and a decoder for a higher layer may be provided in correspondence to the number of upper layers. Can be.
  • SVC Scalable Video Coding
  • the current layer may generate a prediction sample of the current layer by using a decoded picture of a reference layer used for inter-layer prediction as a reference picture.
  • the picture of the decoded reference layer matches the scalability of the current layer.
  • Resampling may be performed and then used as a reference picture for inter-layer prediction of the current layer. Resampling means up-sampling or downsampling samples of a reference layer picture according to a picture size of a current layer.
  • the current layer refers to a layer on which current encoding or decoding is performed, and may be an enhancement layer or an upper layer.
  • the reference layer refers to a layer referenced by the current layer for inter-layer prediction and may be a base layer or a lower layer.
  • a picture (ie, a reference picture) of a reference layer used for inter-layer prediction of the current layer may be referred to as an interlayer reference picture or an inter-layer reference picture.
  • FIG. 3 is a flowchart illustrating a process of performing inter-layer prediction of an upper layer using a corresponding picture of a lower layer according to an embodiment to which the present invention is applied.
  • a corresponding picture belonging to a lower layer used for inter-layer prediction of a current picture belonging to an upper layer may be determined (S300).
  • the lower layer may mean another enhancement layer having a lower resolution than the base layer or the upper layer.
  • the corresponding picture may mean a picture located at the same time zone as the current picture of the upper layer.
  • the corresponding picture may be a picture having the same picture order count (POC) information as the current picture of the upper layer.
  • the corresponding picture may belong to the same Access Unit (AU) as the current picture of the upper layer.
  • the corresponding picture may have the same temporal level identifier (TemporalID) as the current picture of the upper layer.
  • the temporal level identifier may mean an identifier for specifying each of a plurality of layers that are coded scalable according to temporal resolution.
  • the current block may use corresponding pictures of one or more lower layers for inter-layer prediction, and a method of determining the corresponding picture will be described with reference to FIGS. 4 to 6.
  • Inter-layer prediction of the current picture may be performed using the corresponding picture of the lower layer determined in step S300 (S310).
  • inter-layer prediction may be performed in parallel on a tile basis of a multi-layer through tile alignment between an upper layer and a lower ray. This will be described with reference to FIGS. 8 to 12.
  • inter-layer prediction of the current picture of the upper layer may be limited depending on whether tiles are arranged between the multi-layers, which will be described with reference to FIGS. 13 to 16.
  • the current picture may be used as an interlayer reference picture by upsampling the corresponding picture of the lower layer.
  • a method of upsampling a corresponding picture of a lower layer will be described with reference to FIG. 17.
  • FIG. 4 illustrates a method of determining a corresponding picture of a lower layer based on a reference active flag according to an embodiment to which the present invention is applied.
  • a reference active flag may be obtained from a bitstream (S400).
  • the reference active flag all_ref_layers_active_flag may indicate whether a constraint is applied that the corresponding pictures of all layers having direct dependency with the upper layer are used for inter-layer prediction of the current picture.
  • the reference active flag may be obtained from a video parameter set of the bitstream.
  • whether the layer has a direct dependency with the upper layer may be determined based on the direct dependency flag direct_dependency_flag [i] [j].
  • the direct dependency flag direct_dependency_flag [i] [j] may indicate whether the j th layer is used for inter-layer prediction of the i th upper layer.
  • the j th layer may be used for inter-layer prediction of the i th higher layer. If the value of the direct dependency flag is 0, the j th layer may be used. It may not be used for inter-layer prediction of the i th upper layer.
  • the value of the reference active flag is 1, the constraint that the corresponding picture of all layers having direct dependency with the upper layer is used for inter-layer prediction of the current picture is applied.
  • corresponding pictures of all layers having direct dependency with the upper layer may be included in the reference picture list of the current picture. Accordingly, the corresponding picture of all layers having direct dependency with the upper layer may be determined as the corresponding picture used for inter-layer prediction of the current picture (S420).
  • the current picture of the upper layer may perform inter-layer prediction by using corresponding pictures of all layers having direct dependency on the upper layer, and only some corresponding pictures among all layers having direct dependency on the upper layer may be used. Inter-layer prediction may be performed selectively. That is, when the value of the reference active flag is 0, the corresponding picture of all layers having direct dependency with the upper layer may be included in the reference picture list of the current picture, or only some of the corresponding pictures may be selectively included. Therefore, it is necessary to specify the corresponding picture used for inter-layer prediction of the current picture among the layers having the direct dependency with the upper layer. To this end, interlayer reference information about the current picture may be obtained (S430).
  • the interlayer reference information may include at least one of an interlayer prediction flag, information on the number of reference pictures, or a reference layer identifier.
  • the interlayer prediction flag may indicate whether inter-layer prediction is used in the decoding process of the current picture.
  • the number information of the reference picture may indicate the number of corresponding pictures used for inter-layer prediction of the current picture. Information about the number of reference pictures may be encoded and signaled by subtracting 1 from the number of corresponding pictures used for inter-layer prediction of the current picture for coding efficiency.
  • the reference layer identifier may mean a layer identifier (layerId) of a layer including a corresponding picture used for inter-layer prediction of the current picture.
  • a corresponding picture used for inter-layer prediction may be determined based on the interlayer reference information obtained in S430 (S440).
  • the corresponding picture of the layer specified by the reference layer identifier among the layers having direct dependency with the upper layer may be determined as the corresponding picture used for inter-layer prediction of the current picture.
  • FIG. 5 illustrates a method of obtaining interlayer reference information on a current picture as an embodiment to which the present invention is applied
  • FIG. 6 illustrates a syntax table of interlayer reference information as an embodiment to which the present invention is applied. It is shown.
  • an interlayer prediction flag may be obtained based on a reference active flag (S500).
  • the interlayer prediction flag inter_layer_pred_enabled_flag may be obtained only when the value of the reference active flag all_ref_layers_active_flag is 0 (S600).
  • the value of the reference active flag is 1, this may mean that corresponding pictures of all layers having direct dependency with a higher layer are used for inter-layer prediction of the current picture. Thus, in this case, there is no need to signal the interlayer prediction flag in the header information (eg, slice segment header) of the current picture.
  • the header information eg, slice segment header
  • the interlayer prediction flag may be obtained. This is because when the layer identifier of the upper layer is 0, the upper layer corresponds to a base layer which does not perform inter-layer prediction in the multilayer.
  • the interlayer prediction flag may be obtained when the number NumDirectRefLayers of the layer having the direct dependency with the upper layer is at least one or more. This is because when there is no layer having direct dependency on the upper layer, all the pictures of the upper layer do not perform inter-layer prediction.
  • the number information of the reference picture may indicate the number of corresponding pictures used for inter-layer prediction of the current picture among the corresponding pictures of the layer having the direct dependency with the upper layer.
  • the number of corresponding pictures used for inter-layer prediction of the current picture may not exceed one. It is not necessary to signal the number information (num_inter_layer_ref_pics_minus1) of the reference picture. In this case, the number information of the reference picture may not be obtained, and the number of corresponding pictures used for inter-layer prediction of the current picture may be derived as one.
  • the number information of the reference picture may be obtained limitedly based on the maximum active reference flag.
  • the maximum active reference flag may indicate whether only at least one corresponding picture is used for inter-layer prediction of the current picture. For example, when the value of the maximum active reference flag is 1, the current picture performs inter-layer prediction using only at least one corresponding picture. When the value of the maximum active reference flag is 0, the current picture is one or more corresponding. Inter-layer prediction may be performed using a picture.
  • the number information of the reference picture may be obtained only when the value of the maximum active reference flag max_one_active_ref_layer_flag is 0. That is, when the value of the maximum active reference flag is 1, since the number of corresponding pictures used for inter-layer prediction of the current picture is limited to one, it is not necessary to signal the number information of the reference picture.
  • a reference layer identifier may be obtained based on the number information of the reference pictures acquired in S520 (S530).
  • the number NumDirectRefLayers is different, a reference layer identifier may be obtained.
  • the variable NumActiveRefLayerPics is a variable derived from the number information of the reference picture. For example, when information on the number of reference pictures is encoded by subtracting 1 from the number of corresponding pictures used for inter-layer prediction of the current picture, the variable NumActiveRefLayerPics adds 1 to the information on the number of reference pictures acquired in S520. Can be derived from a value.
  • FIG. 7 illustrates a relationship between slices and tiles as an embodiment to which the present invention is applied.
  • One picture may be divided into at least one slice.
  • the slice may be a basic unit capable of independently performing entropy decoding.
  • One slice may be composed of a plurality of slice segments.
  • one picture may be divided into at least one tile.
  • the tile is a rectangular area composed of a plurality of coding tree units, and entropy decoding may be performed in units of tiles. Furthermore, it enables parallel processing of decoding a plurality of tiles simultaneously.
  • the size or unit of the tile may be encoded by the optimum size or unit in the encoder and transmitted to the decoder.
  • the size or unit of the tile of the upper layer may be derived based on inter-layer tile alignment, that is, the size or unit of the tile of the lower layer.
  • FIG. 7A illustrates a case where a picture is divided into one independent slice segment and four dependent slice segments.
  • the independent slice segment means that the slice segment header is included.
  • the dependent slice segment does not include a slice segment header, which may use the same header of the independent slice segment.
  • the slice segment is composed of a plurality of coding tree units, and the coding tree unit corresponds to a maximum size of a coding unit that is a basic unit of video signal processing.
  • one tile may include a plurality of slice segments, and one slice segment may exist in one tile.
  • one slice segment may exist in one tile.
  • a plurality of tiles may exist in one slice.
  • Figure 7 (b) shows a case where one tile is composed of two or more slices. That is, referring to FIG. 7B, slice 0 may be composed of independent slice segment 0 and dependent slice segment 1, and slice 1 may be composed of independent slice segment 1 and dependent slice segment 2. Slice 0 and slice 1 may be included in one tile (tile 0).
  • FIG. 8 illustrates a method of performing inter-layer prediction using tile alignment between multi-layers as an embodiment to which the present invention is applied.
  • tile alignment between multiple layers may be performed (S800).
  • tile alignment between multiple layers may mean deriving the size or unit of the tile of the upper layer based on the size or unit of the tile of the lower layer.
  • the size or unit of the tile of the upper layer may be set to be the same as the size or unit of the tile of the lower layer.
  • the size or unit of the tile of the upper layer may be derived by using information about the size or unit of the tile of the lower layer.
  • inter-layer prediction between tiles of a multi-layer may be performed in parallel (S810).
  • one tile of the lower layer may be decoded and then one tile of the upper layer may be decoded. After decoding the next tile of the lower layer, the next tile of the upper layer may be decoded.
  • interposing a tile size or a tile unit between an upper layer and a lower layer inter prediction between an upper layer and a lower layer may be performed in parallel.
  • the lower layer may be decoded and then the upper layer may be decoded.
  • FIG. 9 illustrates a method for adaptively performing inter-layer tile alignment based on a discardable flag as an embodiment to which the present invention is applied.
  • a discardable flag of a corresponding picture of a lower layer may be obtained (S900).
  • the discardable flag may mean information indicating whether an encoded picture is used as a reference picture or an interlayer reference picture in the decoding process of a lower priority picture in decoding order. That is, when the discardable flag is 1, it means that the encoded picture is not used as the reference picture or the interlayer reference picture in the decoding process of the lower priority picture in decoding order. In this case, for efficient management of a decoded picture buffer (DPB), the encoded picture may be marked as an unused for reference indicating that it is not used as a reference picture. On the contrary, when the discardable flag is 0, it means that the hatched picture can be used as a reference picture or an interlayer reference picture in the decoding process of a lower priority picture in decoding order.
  • DPB decoded picture buffer
  • the discardable flag is not limited to being acquired in a picture unit, but may be obtained in a slice or slice segment.
  • the value of the discardable flag acquired in step S900 may be checked (S910).
  • the current picture of the upper layer may not perform tile alignment between layers based on the tile size or the tile unit of the corresponding picture of the lower layer (S920).
  • the current picture of the upper layer may perform tile alignment between layers based on the tile size or the tile unit of the corresponding picture of the lower layer (S930).
  • 10 to 12 illustrate a method of adaptively performing inter-layer tile alignment based on a temporal ID (TemporalID) of a lower layer as an embodiment to which the present invention is applied.
  • TempooralID Temporal ID
  • tile alignment between layers may be adaptively performed according to the value of the temporal level identifier of a picture belonging to a specific layer.
  • a maximum temporal level identifier of a lower layer may be obtained (S1000).
  • a method of obtaining the maximum time level identifier has been described with reference to FIG. 5, and a detailed description thereof will be omitted.
  • the maximum temporal level identifier obtained in step S1000 may be compared with the temporal level identifiers of the corresponding pictures of the lower layer (S1010).
  • step S1010 when the temporal level identifier of the corresponding picture of the lower layer is larger than the maximum temporal level identifier of the lower layer, the corresponding picture of the lower layer is not used as an interlayer reference picture of the current picture of the upper layer. Therefore, the current picture of the upper layer may not perform tile alignment between layers based on the corresponding picture of the lower layer (S1020).
  • step S1010 when the comparison result of step S1010 indicates that the temporal level identifier of the corresponding picture of the lower layer is equal to or smaller than the maximum temporal level identifier of the lower layer, the corresponding picture of the lower layer is used as the interlayer reference picture of the current picture of the upper layer. Can be. Therefore, the current picture of the upper layer may perform tile alignment between layers based on the corresponding picture of the lower layer (S1030).
  • a temporal level identifier of a current picture of an upper layer and a temporal level identifier of a corresponding picture of a lower layer may be compared (S1100).
  • the temporal level identifier of the current picture of the upper layer and the temporal level identifier of the corresponding picture of the lower layer corresponding thereto may be compared with the same value or different values.
  • the current picture of the upper layer and the corresponding picture of the lower layer have different temporal level identifiers, it may be inefficient to perform inter-layer prediction or inter-layer tile alignment.
  • tile alignment between multiple layers may be performed (S1110).
  • tile alignment between layers may not be performed.
  • tile alignment between layers may be performed only when the current picture of the upper layer and the corresponding picture of the lower layer have the same temporal level identifier.
  • Inter-layer tile alignment may be adaptively performed based on the combination of the method of (1) and (2) described above.
  • a maximum temporal level identifier of a lower layer may be obtained (S1200).
  • the maximum temporal level identifier obtained in step S1200 may be compared with the temporal level identifiers of the corresponding pictures of the lower layer (S1210).
  • step S1210 when the temporal level identifier of the corresponding picture of the lower layer is larger than the maximum temporal level identifier of the lower layer, the corresponding picture of the lower layer is not used as an interlayer reference picture of the current picture of the upper layer. Therefore, the current picture of the upper layer may not perform tile alignment between layers based on the corresponding picture of the lower layer (S1220).
  • step S1210 when the temporal level identifier of the corresponding picture of the lower layer is equal to or smaller than the maximum temporal level identifier of the lower layer, the temporal level identifier of the current picture of the upper layer and the temporal level identifier of the corresponding picture of the lower layer It may be compared (S1230).
  • tile alignment between the multi-layers may be performed (S1240).
  • tile alignment between layers may not be performed.
  • tile alignment between layers may be performed only when the current picture of the upper layer and the corresponding picture of the lower layer have the same temporal level identifier.
  • the maximum temporal level identifier of the lower layer is compared with the temporal level identifiers of the corresponding pictures of the lower layer, and then, whether the temporal level identifier is the same between the upper layer and the lower layer is compared, but this does not limit the comparison order.
  • the maximum temporal level identifier of the lower layer and the temporal level identifier of the corresponding picture of the lower layer may be compared.
  • FIG. 13 is a flowchart illustrating a method of performing inter-layer prediction limited according to whether tiles between layers are aligned according to an embodiment to which the present invention is applied.
  • the tile alignment between the upper layer and the lower layer may be checked based on the tile boundary alignment flag tile_boundaries_aligned_flag [i] [j].
  • tile boundary alignment flag (tile_boundaries_aligned_flag [i] [j]) is 1, this means that if two samples of the current picture belonging to the i th layer (ie, the upper layer) belong to one tile, j If two samples of the corresponding picture belonging to the first layer (that is, the lower layer) also belong to one tile, and two samples of the current picture belonging to the i-th layer belong to another tile, the corresponding picture belonging to the j-th layer Two samples also belong to different tiles.
  • the value of the tile boundary alignment flag is 1, this may mean that the size or unit of the tile is aligned between the current picture of the upper layer and the corresponding picture of the lower layer.
  • the value of the tile boundary alignment flag is 0, this may mean that tile alignment is not performed between layers.
  • the j th layer may mean a layer having direct dependency on the i th layer. Whether the layer has a direct dependency with the upper layer may be determined based on the direct dependency flag direct_dependency_flag [i] [j].
  • the direct dependency flag direct_dependency_flag [i] [j] may indicate whether the j th layer is used for inter-layer prediction of the i th upper layer.
  • the j th layer may be used for inter-layer prediction of the i th higher layer. If the value of the direct dependency flag is 0, the j th layer may be used. It may not be used for inter-layer prediction of the i th upper layer.
  • two samples of the corresponding picture belonging to the j-th layer may mean a sample at the same position as the two samples of the current picture.
  • the tile boundary alignment flag may be obtained from video usability information (VUI) belonging to a video parameter set.
  • VUI video usability information
  • the video usability information may not be used to decode the luminance component or the chrominance component, but may refer to information used for decoder conformance or output timing conformance.
  • the tile boundary alignment flag is obtained when information on the size or unit of a tile exists for at least one picture belonging to each of an upper layer (ie, the i-th layer) and a lower layer (ie, the j-th layer).
  • a method of obtaining the tile boundary alignment flag will be described with reference to FIGS. 14 to 16.
  • a limited inter-layer prediction may be performed based on the check result in operation S1300 (S1310).
  • a sample of a specific area belonging to the corresponding picture of the lower layer may be limited not to be used for inter-layer prediction of the current picture of the upper layer.
  • samples located outside the tile belonging to the corresponding picture may be restricted from being used for inter-layer prediction of samples located inside the tile belonging to the current picture. Can be. That is, when the value of the tile boundary alignment flag of the current picture is 1, inter-layer prediction may be performed using only samples located inside the tile belonging to the corresponding picture for samples located inside the tile belonging to the current picture.
  • the constraint that a sample located outside the tile belonging to the corresponding picture is not used for inter-layer prediction of a sample located inside the tile belonging to the current picture is applied. Can not be. That is, when the tile boundary alignment flag value of the current picture is 0, samples located inside the tile belonging to the current picture may perform inter-layer prediction using samples located inside and / or outside the tile belonging to the corresponding picture. Can be.
  • the tile belonging to the current picture may mean a tile corresponding to a tile belonging to the corresponding picture through tile alignment between layers.
  • each tile belonging to the current picture and the corresponding picture may mean one tile or a tile set composed of a plurality of tiles.
  • 14 to 16 illustrate syntax of a tile boundary alignment flag according to an embodiment to which the present invention is applied.
  • tile boundary alignment flag tile_boundaries_aligned_flag [i] [j] may be obtained (S1400).
  • the tile boundary alignment flag tile_boundaries_aligned_flag [i] [j] may indicate whether the i th layer is aligned with the tile size or unit of the j th layer.
  • the j th layer refers to a layer having direct dependency with the i th layer among the plurality of layers included in the video sequence. That is, the j th layer refers to a layer used for inter-layer prediction of the i th layer.
  • the tile boundary alignment flag may be obtained by the number of layers (NumDirectRefLayers_id_in_nuh [i]) having the direct dependency on the i th layer.
  • tile alignment between layers may not be used in all layers in the video sequence, and a non-tile alignment flag (tile_boundaries_non_aligned_flag) may be signaled for this purpose.
  • a non-tile aligned flag (tile_boundaries_non_aligned_flag) may be obtained (S1500).
  • the non-tile alignment flag may indicate whether inter-layer tile alignment is limited in the layer in the video sequence.
  • tile alignment between layers may not be performed. If a picture in the video sequence does not use a tile, the value of the non-tile alignment flag will be encoded as one. Conversely, if the value of the non-tile alignment flag is 1, this may mean that the picture in the video sequence does not use tiles, and the constraint that no tile alignment is performed on the layers in the video sequence is applied. can do.
  • the value of the non-tile alignment flag when the value of the non-tile alignment flag is 0, this means that the constraint that the tile alignment between the layers in the video sequence is not performed is not applied. That is, when the value of the non-tile alignment flag is 0, it means that a picture belonging to a layer in the video sequence uses a tile. Alternatively, when the value of the non-tile alignment flag is 0, it means that tile alignment between layers may be performed on at least one layer among the layers in the video sequence.
  • the non-tile alignment flag may indicate whether the tile boundary alignment flag is present or whether the tile boundary alignment flag is extracted from the bitstream.
  • the tile boundary alignment flag tile_boundaries_aligned_flag [i] [j] may be limitedly obtained only when the value of the non-tile alignment flag is 0 (S1510).
  • the non-tile alignment flag when the value of the non-tile alignment flag is 1, since the layers in the video sequence do not perform tile alignment between layers, it is not necessary to signal a tile boundary alignment flag indicating whether tiles are aligned for each layer.
  • the tile boundary alignment flag tile_boundaries_aligned_flag [i] [j] indicates whether the i th layer is aligned with the tile size or unit of the j th layer, and the j th layer is included in the video sequence. It means a layer having direct dependency on the i-th layer among the plurality of layers included. That is, the j th layer refers to a layer used for inter-layer prediction of the i th layer. Accordingly, the tile boundary alignment flag may be obtained by the number of layers (NumDirectRefLayers_id_in_nuh [i]) having the direct dependency on the i th layer.
  • tile alignment between layers may occur in all layers except for layers that do not perform inter-layer prediction within a video sequence (for example, layers encoded by H.264 / AVC or HEVC codec).
  • the tile alignment present flag (tile_boundaries_aligned_present_flag) may be signaled.
  • tile alignment present flag (tile_boundaries_aligned_present_flag) may be obtained (S1600).
  • the tile alignment present flag may indicate whether tile boundaries of all layers except the layer that does not perform inter-layer prediction in the video sequence are inferred.
  • the tile alignment present flag when the value of the tile alignment present flag is 1, it indicates that the tile boundary of all the layers is inferred, and when the value of the tile alignment present flag is 0, the tile boundary of all the layers is not inferred. Can be represented.
  • tile boundary alignment flag tile_boundaries_aligned_flag [i] [j] may be obtained in a limited manner only when the value of the tile alignment present flag is 0 (S1610).
  • tile alignment present flag when the value of the tile alignment present flag is 1, this indicates that tile boundaries belonging to the picture or slice are inferred, and thus it is not necessary to signal the tile boundary alignment flag for each layer.
  • the value of the tile alignment present flag when the value of the tile alignment present flag is 0, tile boundaries belonging to the picture or slice are not inferred, and thus, it is necessary to signal a tile boundary alignment flag indicating whether tiles are aligned for each layer.
  • whether a tile boundary belonging to a picture or slice is inferred may be determined based on the number of tiles belonging to the picture or slice.
  • the tile boundary can be inferred identically to the picture boundary. Therefore, when the number of tiles of the picture of the video sequence is 1, the tile alignment present flag may be encoded as 1, and the tile boundary alignment flag may not be signaled for each layer. That is, the tile boundary alignment flag may be limited so as not to be acquired when the number of tiles of the picture of the video sequence is one.
  • the tile boundary alignment flag may be obtained when the number of tiles belonging to the picture of the video sequence is plural.
  • the case where the number of tiles belonging to a picture of the video sequence is plural may mean that a tile is used in the corresponding picture.
  • the tile boundary alignment flag indicates whether the i th layer is aligned with the tile size or unit of the j th layer, and the j th layer includes a plurality of layers included in the video sequence.
  • the layer has a direct dependency on the i-th layer among the layers. That is, the j th layer refers to a layer used for inter-layer prediction of the i th layer. Accordingly, the tile boundary alignment flag may be obtained by the number of layers (NumDirectRefLayers_id_in_nuh [i]) having the direct dependency on the i th layer.
  • 17 is a flowchart illustrating a method of upsampling a corresponding picture of a lower layer according to an embodiment to which the present invention is applied.
  • a reference sample position of a lower layer corresponding to a current sample position of an upper layer may be derived (S1700).
  • a reference sample position corresponding to the current sample position may be derived in consideration of the resolution difference between the two layers. That is, the aspect ratio may be considered between the picture of the upper layer and the picture of the lower layer.
  • an offset may be required to correct this.
  • the reference sample position may be derived in consideration of the scale factor and the upsampled lower layer offset.
  • the scale factor may be calculated based on a ratio of the width and the height between the current picture of the upper layer and the corresponding picture of the lower layer.
  • the upsampled lower layer offset may mean position difference information between any one sample located at the edge of the current picture and any one sample located at the edge of the interlayer reference picture.
  • the upsampled lower layer offset includes horizontal position information in the horizontal / vertical direction between the upper left sample of the current picture and the upper left sample of the interlayer reference picture, and the lower right sample of the current picture and the lower right sample of the interlayer reference picture.
  • Position difference information in the horizontal / vertical direction of the liver may be included.
  • the upsampled lower layer offset may be obtained from the bitstream.
  • the upsampled lower layer offset may be obtained from at least one of a video parameter set, a sequence parameter set, a picture parameter set, and a slice header. Can be.
  • the filter coefficient of the upsampling filter may be determined in consideration of the phase of the reference sample position derived in step S1700 (S1710).
  • the upsampling filter may be any one of a fixed upsampling filter and an adaptive upsampling filter.
  • the fixed upsampling filter may mean an upsampling filter having a predetermined filter coefficient without considering the feature of the image.
  • a tap filter may be used as the fixed upsampling filter, which may be defined for the luminance component and the chrominance component, respectively.
  • a fixed upsampling filter having an accuracy of 1/16 sample units will be described with reference to Tables 1 to 2.
  • Table 1 is a table that defines the filter coefficients of the fixed upsampling filter for the luminance component.
  • an 8-tap filter is applied. That is, interpolation may be performed using a reference sample of a reference layer corresponding to the current sample of the upper layer and a neighboring sample adjacent to the reference sample.
  • the neighbor sample may be specified according to the direction in which interpolation is performed. For example, when performing interpolation 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 performing interpolation 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.
  • the fixed upsampling filter may use different filter coefficients for each phase p. Except in the case where phase p is zero, the magnitude of each filter coefficient may be defined to fall in the range of 0 to 63. This means that the filtering is performed with a precision of 6 bits.
  • a phase p of 0 means a position of an integer multiple of n times when interpolated in units of 1 / n samples.
  • Table 2 is a table that defines the filter coefficients of the fixed upsampling filter for the chrominance components.
  • a 4-tap filter may be applied unlike the luminance component. That is, interpolation may be performed using a reference sample of a reference layer corresponding to the current sample of the upper layer and a neighboring sample adjacent to the reference sample.
  • the neighbor sample may be specified according to the direction in which interpolation is performed. For example, when performing interpolation in the horizontal direction, the neighboring sample may include one sample to the left and two samples to the right based on the reference sample. Alternatively, when performing interpolation in the vertical direction, the neighboring sample may include one sample continuous to the top and two samples continuous to the bottom based on the reference sample.
  • each filter coefficient may be defined to be in the range of 0 to 62. This also means filtering with 6bits precision.
  • an 8-tap filter is applied to the luminance component and a 4-tap filter to the chrominance component
  • the present invention is not limited thereto, and the order of the tap filter may be variably determined in consideration of coding efficiency.
  • the order of the tap filter may be variably determined in consideration of coding efficiency.
  • an optimal filter coefficient may be determined by an encoder in consideration of characteristics of an image, signaled, and transmitted to a decoder.
  • the adaptive upsampling filter uses the filter coefficients that are adaptively determined in the encoder. Since the characteristics of the image are different in picture units, coding efficiency can be improved by using an adaptive upsampling filter that can express the characteristics of the image better than using a fixed upsampling filter in all cases.
  • the interlayer reference picture may be generated by applying the filter coefficient determined in operation S1710 to the corresponding picture of the lower layer (S1720).
  • interpolation may be performed by applying the determined filter coefficients of the upsampling filter to samples of the corresponding picture.
  • the interpolation may be performed primarily in the horizontal direction, and may be performed in the vertical direction secondary to the sample generated after the horizontal interpolation.
  • the present invention can be used to code a video signal.

Abstract

Selon la présente invention, une méthode de décodage de signal vidéo extensible détermine une image correspondante appartenant à une couche inférieure utilisée pour une prévision entre couches d'une image actuelle appartenant à une couche supérieure, et effectue la prévision entre couches de l'image actuelle en utilisant l'image correspondante de la couche inférieure déterminée, la prévision entre couches étant effectuée de façon restreinte en fonction d'un drapeau d'alignement de limite de pavé indiquant si des pavés entre la couche supérieure et la couche inférieure sont alignés.
PCT/KR2014/009955 2013-10-22 2014-10-22 Méthode et appareil d'encodage/de décodage de signal vidéo à multiples couches WO2015060642A1 (fr)

Priority Applications (4)

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CN201480058386.XA CN105659596A (zh) 2013-10-22 2014-10-22 用于对多层视频信号进行编码/解码的方法和装置
US15/029,622 US10045020B2 (en) 2013-10-22 2014-10-22 Method and apparatus for encoding/decoding multilayer video signal
MX2016005198A MX364015B (es) 2013-10-22 2014-10-22 Metodo y aparato para codificar/descodificar una señal de video de multicapa.
US16/006,104 US10602136B2 (en) 2013-10-22 2018-06-12 Method and apparatus for encoding/decoding multilayer video signal

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KR10-2013-0125922 2013-10-22
KR20130125922 2013-10-22
KR20140142461A KR20150046742A (ko) 2013-10-22 2014-10-21 멀티 레이어 비디오 신호 인코딩/디코딩 방법 및 장치
KR10-2014-0142461 2014-10-21

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US16/006,104 Continuation US10602136B2 (en) 2013-10-22 2018-06-12 Method and apparatus for encoding/decoding multilayer video signal

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