WO2016159631A1 - 비디오 신호의 인코딩/디코딩 방법 및 장치 - Google Patents
비디오 신호의 인코딩/디코딩 방법 및 장치 Download PDFInfo
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Definitions
- the present invention relates to a method and apparatus for encoding / decoding a video signal, and more particularly, to a method and apparatus for performing efficient intra prediction.
- Compression coding refers to a series of signal processing techniques for transmitting digitized information through a communication line or for storing in a form suitable for a storage medium.
- Media such as an image, an image, an audio, and the like may be a target of compression encoding.
- a technique of performing compression encoding on an image is called video image compression.
- Next-generation video content will be characterized by high spatial resolution, high frame rate and high dimensionality of scene representation. Processing such content would result in a tremendous increase in terms of memory storage, memory access rate, and processing power.
- the present invention proposes a method for setting an intra directional prediction mode with more direction and precision in performing intra prediction.
- the present invention proposes a method for adaptively setting an intra prediction mode according to a characteristic of an image when performing intra prediction.
- the present invention proposes a method of changing or adjusting the position interval of intra directional prediction modes.
- An object of the present invention is to propose a method of biasing a prediction mode in a specific direction corresponding to a characteristic of an image in performing intra prediction.
- the present invention proposes a method for adaptively selecting at least one of the number of modes or the position of each mode corresponding to an intra angular prediction mode.
- the present invention proposes a method for non-uniformly setting the position interval of the intra directional prediction mode.
- the present invention proposes a method of signaling information for performing the above methods.
- the present invention provides a method for defining an intra directional prediction mode with more direction and precision.
- the present invention provides a method for adaptively setting an intra prediction mode according to characteristics of an image when performing intra prediction.
- the present invention provides a method of changing or adjusting the position interval of intra directional prediction modes.
- the present invention provides a method of biasing a prediction mode in a specific direction corresponding to a characteristic of an image in performing intra prediction.
- the present invention provides a method for adaptively selecting at least one of the number of modes or the location of each mode corresponding to an intra angular prediction mode.
- the present invention provides a method for non-uniformly setting the position interval of the intra directional prediction mode.
- the present invention provides a method of signaling information for performing the above methods.
- the present invention can increase the prediction accuracy and further improve the coding efficiency by defining an intra directional prediction mode having more direction and precision in intra prediction coding.
- the present invention provides a method of biasing a prediction mode in a specific direction corresponding to a characteristic of an image in performing intra prediction, and further provides an adaptive intra prediction by providing a method of changing or adjusting the position interval of intra directional prediction modes. Can be performed.
- the present invention can perform more efficient intra prediction by adaptively setting the intra prediction mode according to the characteristics of the image.
- the present invention can perform more adaptive intra prediction by non-uniformly setting the position interval of the intra directional prediction mode.
- the present invention can process video signals more efficiently by reducing the amount of residual data to be transmitted by performing more accurate intra prediction.
- FIG. 1 is a schematic block diagram of an encoder in which encoding of a video signal is performed as an embodiment to which the present invention is applied.
- FIG. 2 is a schematic block diagram of a decoder in which decoding of a video signal is performed as an embodiment to which the present invention is applied.
- FIG. 3 is a diagram for describing a division structure of a coding unit according to an embodiment to which the present invention is applied.
- FIG. 4 is a diagram for describing a prediction unit according to an embodiment to which the present invention is applied.
- FIG. 5 is a diagram for describing an intra prediction method according to an embodiment to which the present invention is applied.
- FIG. 6 is a diagram for describing a prediction direction according to an intra prediction mode according to an embodiment to which the present invention is applied.
- FIG. 7 is a diagram for describing a method of interpolating a reference pixel at a subpixel position according to another embodiment to which the present invention is applied.
- FIG. 8 is a diagram for describing an angle parameter according to an intra prediction mode according to an embodiment to which the present invention is applied.
- FIG. 9 illustrates an embodiment to which the present invention is applied and adaptively selects a mode when the intra prediction mode has 1 / M precision.
- FIG. 10 is a schematic block diagram of an encoder for encoding an adaptively selected mode in intra prediction, according to an embodiment to which the present invention is applied.
- FIG. 11 is a schematic block diagram of a decoder for decoding an adaptively selected mode in intra prediction as an embodiment to which the present invention is applied.
- FIGS. 12 to 13 are diagrams for describing various intra directional prediction modes according to prediction accuracy
- FIG. 14 is an angle parameter corresponding to each intra directional prediction mode. (angle parameter) is a table.
- FIG. 15 illustrates a method of obtaining a prediction sample according to a newly defined intra direction prediction mode according to an embodiment to which the present invention is applied.
- FIG. 16 is a diagram for describing a scan order used in intra prediction as an embodiment to which the present invention is applied.
- FIG. 17 to 18 illustrate embodiments to which the present invention is applied.
- FIG. 17 illustrates a method of allocating a scan index according to a newly defined intra direction prediction mode
- FIG. 18 illustrates a scan index allocated according to an intra direction prediction mode. Indicates.
- 19 to 21 are diagrams for explaining scan orders of coefficients in a TU as embodiments to which the present invention is applied.
- FIG. 22 is a diagram for describing a method of changing an interval between angle parameters according to an embodiment to which the present invention is applied.
- FIG. 23 is a diagram for describing a method of changing an interval between angle parameters in units of a 45 degree region according to an embodiment to which the present invention is applied.
- FIG. 24 is a diagram for describing a method of changing an interval between angle parameters in units of a horizontal / vertical region as an embodiment to which the present invention is applied.
- FIG. 25 is an embodiment to which the present invention is applied and is a syntax defining a flip flag indicating whether to change an interval between an angle parameter in a sequence parameter set and a slice header.
- FIG. 26 is a flowchart illustrating a process of performing intra prediction according to a flip flag according to an embodiment to which the present invention is applied.
- FIG. 27 is a flowchart illustrating a process of performing intra prediction according to a flip flag in units of a horizontal / vertical region according to an embodiment to which the present invention is applied.
- FIG. 28 is a diagram for describing a method of explicitly transmitting interval information between angle parameters according to an embodiment to which the present invention is applied.
- FIG. 29 is a diagram for describing a method of explicitly transmitting interval information between angle parameters in units of a 45 degree region according to an embodiment to which the present invention is applied.
- FIG. 30 is a diagram for explaining a method of explicitly transmitting interval information between angle parameters in units of a horizontal / vertical region according to an embodiment to which the present invention is applied.
- FIG. 31 is a syntax illustrating an embodiment to which the present invention is applied and defines a method of explicitly transmitting interval information between angle parameters.
- 32 is a flowchart illustrating a process of performing intra prediction based on an angle transmission flag according to an embodiment to which the present invention is applied.
- 33 is a flowchart illustrating a process of performing intra prediction using interval information between angle parameters according to an embodiment to which the present invention is applied.
- FIG. 34 is a diagram for explaining a method of setting intra directional prediction modes at non-uniform intervals according to an embodiment to which the present invention is applied.
- a method of decoding a video signal comprising: obtaining a flip flag indicating whether to perform a flip of an angle interval in intra prediction from the video signal; Deriving a flip angle variable according to an intra prediction mode when performing flip of an angular interval during intra prediction according to the flip flag; And generating an intra prediction sample based on the flip angle variable, wherein the angle interval represents an interval between angle parameters indicating a prediction direction.
- the flip angle variable corresponds to an angle parameter
- the angle parameter is characterized by representing a value set according to the intra prediction mode.
- the flip flag is set in a specific area unit, and the specific area unit may be a horizontal / vertical area or a 45 degree area.
- the flip flag is obtained from at least one of a sequence parameter set, a picture parameter set, a slice, a block, a coding unit, or a prediction unit.
- the present invention also provides a method of decoding a video signal, the method comprising: obtaining an angle transmission flag indicating whether the video signal includes prediction angle information indicating an intra prediction direction; Acquiring prediction angle information when the video signal includes prediction angle information according to the angle transmission flag; Deriving an angle parameter based on the prediction angle information; And generating an intra prediction sample based on the angle parameter, wherein the prediction angle information includes at least one of an angle interval or an angle parameter, wherein the angle interval indicates a prediction direction. It provides a method characterized by indicating the interval between the representing angle parameter (angle parameter).
- the angle transmission flag is set in a specific area unit, and the specific area unit is a horizontal / vertical area or a 45 degree area.
- the angle transmission flag when the angle transmission flag is set in units of horizontal / vertical region, the angle transmission flag is obtained for both the horizontal region and the vertical region, and the prediction angle information is based on the horizontal angle transmission flag And at least one of an area and a vertical area.
- the angle transmission flag is obtained from at least one of a sequence parameter set, a picture parameter set, a slice, a block, a coding unit, or a prediction unit.
- the prediction angle information is characterized in that the flip is performed on the angle interval or the angle parameter.
- the present invention provides an apparatus for decoding a video signal, the apparatus comprising: a parser configured to obtain a flip flag indicating whether to flip an angle interval during intra prediction from the video signal; And an intra predictor configured to derive a flip angle variable according to an intra prediction mode and generate an intra prediction sample based on the flip angle variable when performing flip of an angular interval during intra prediction according to the flip flag.
- the angle interval provides an apparatus characterized in that the interval between the angle parameter (angle parameter) representing the prediction direction.
- the present invention provides an apparatus for decoding a video signal, comprising: a parser for obtaining an angle transmission flag indicating whether the video signal includes prediction angle information indicating an intra prediction direction; If the video signal includes prediction angle information according to the angle transmission flag, obtain prediction angle information, derive an angle parameter based on the prediction angle information, and generate an intra prediction sample based on the angle parameter.
- An intra prediction unit wherein the prediction angle information includes at least one of an angle interval or an angle parameter, wherein the angle interval indicates an interval between angle parameters indicating a prediction direction. It provides a device characterized in that.
- terms used in the present invention may be replaced for more appropriate interpretation when there are general terms selected to describe the invention or other terms having similar meanings.
- signals, data, samples, pictures, frames, blocks, etc. may be appropriately replaced and interpreted in each coding process.
- partitioning, decomposition, splitting, and division may be appropriately replaced and interpreted in each coding process.
- FIG. 1 is a schematic block diagram of an encoder in which encoding of a video signal is performed as an embodiment to which the present invention is applied.
- the encoder 100 may include an image splitter 110, a transformer 120, a quantizer 130, an inverse quantizer 140, an inverse transformer 150, a filter 160, and a decoder. It may include a decoded picture buffer (DPB) 170, an inter predictor 180, an intra predictor 185, and an entropy encoder 190.
- DPB decoded picture buffer
- the image divider 110 may divide an input image (or a picture or a frame) input to the encoder 100 into one or more processing units.
- the processing unit may be a Coding Tree Unit (CTU), a Coding Unit (CU), a Prediction Unit (PU), or a Transform Unit (TU).
- CTU Coding Tree Unit
- CU Coding Unit
- PU Prediction Unit
- TU Transform Unit
- the terms are only used for the convenience of description of the present invention, the present invention is not limited to the definition of the terms.
- the term coding unit is used as a unit used in encoding or decoding a video signal, but the present invention is not limited thereto and may be appropriately interpreted according to the present invention.
- the encoder 100 may generate a residual signal by subtracting a prediction signal output from the inter predictor 180 or the intra predictor 185 from the input image signal, and generate the residual signal. Is transmitted to the converter 120.
- the transformer 120 may generate a transform coefficient by applying a transform technique to the residual signal.
- the conversion process may be applied to pixel blocks having the same size as the square, or may be applied to blocks of variable size rather than square.
- the quantization unit 130 may quantize the transform coefficients and transmit the quantized coefficients to the entropy encoding unit 190, and the entropy encoding unit 190 may entropy code the quantized signal and output the bitstream.
- the quantized signal output from the quantization unit 130 may be used to generate a prediction signal.
- the quantized signal may restore the residual signal by applying inverse quantization and inverse transformation through the inverse quantization unit 140 and the inverse transform unit 150 in the loop.
- a reconstructed signal may be generated by adding the reconstructed residual signal to a prediction signal output from the inter predictor 180 or the intra predictor 185.
- the filtering unit 160 applies filtering to the reconstruction signal and outputs it to the reproduction apparatus or transmits the decoded picture buffer to the decoding picture buffer 170.
- the filtered signal transmitted to the decoded picture buffer 170 may be used as the reference picture in the inter predictor 180. As such, by using the filtered picture as a reference picture in the inter prediction mode, not only image quality but also encoding efficiency may be improved.
- the decoded picture buffer 170 may store the filtered picture for use as a reference picture in the inter prediction unit 180.
- the inter prediction unit 180 performs temporal prediction and / or spatial prediction to remove temporal redundancy and / or spatial redundancy with reference to a reconstructed picture.
- the reference picture used to perform the prediction is a transformed signal that has been quantized and dequantized in units of blocks at the time of encoding / decoding in the previous time, blocking artifacts or ringing artifacts may exist. have.
- the inter prediction unit 180 may interpolate the signals between pixels in sub-pixel units by applying a lowpass filter in order to solve performance degradation due to discontinuity or quantization of such signals.
- the subpixel refers to a virtual pixel generated by applying an interpolation filter
- the integer pixel refers to an actual pixel existing in the reconstructed picture.
- the interpolation method linear interpolation, bi-linear interpolation, wiener filter, or the like may be applied.
- the interpolation filter may be applied to a reconstructed picture to improve the precision of prediction.
- the inter prediction unit 180 generates an interpolation pixel by applying an interpolation filter to integer pixels, and uses an interpolated block composed of interpolated pixels as a prediction block. You can make predictions.
- the intra predictor 185 may predict the current block by referring to samples around the block to which current encoding is to be performed.
- the intra prediction unit 185 may perform the following process to perform intra prediction. First, reference samples necessary for generating a prediction signal may be prepared. The prediction signal may be generated using the prepared reference sample. Then, the prediction mode is encoded. In this case, the reference sample may be prepared through reference sample padding and / or reference sample filtering. Since the reference sample has been predicted and reconstructed, there may be a quantization error. Accordingly, the reference sample filtering process may be performed for each prediction mode used for intra prediction to reduce such an error.
- the present invention provides a method of defining an intra directional prediction mode having more directions and precision in order to increase prediction accuracy when performing intra prediction.
- the present invention also provides a method for adaptively setting an intra prediction mode according to characteristics of an image when performing intra prediction.
- the present invention also provides a method of changing or adjusting the position interval of intra directional prediction modes.
- the present invention also provides a method of biasing a prediction mode in a specific direction corresponding to a characteristic of an image when performing intra prediction.
- the present invention also provides a method for adaptively selecting at least one of the number of modes or the position of each mode corresponding to an intra angular prediction mode.
- the present invention also provides a method for non-uniformly setting the position interval of the intra directional prediction mode.
- a prediction signal generated through the inter predictor 180 or the intra predictor 185 may be used to generate a reconstruction signal or to generate a residual signal.
- FIG. 2 is a schematic block diagram of a decoder in which decoding of a video signal is performed as an embodiment to which the present invention is applied.
- the decoder 200 includes a parser (not shown), an entropy decoder 210, an inverse quantizer 220, an inverse transformer 230, a filter 240, and a decoded picture buffer (DPB).
- a decoded picture buffer unit 250, an inter predictor 260, and an intra predictor 265 may be included.
- the reconstructed video signal output through the decoder 200 may be reproduced through the reproducing apparatus.
- the decoder 200 may receive a video signal output from the encoder 100 of FIG. 1 and parse syntax elements from the video signal through a parser (not shown).
- the parsed signal may be entropy decoded through the entropy decoding unit 210 or transmitted to another functional unit.
- the inverse quantization unit 220 obtains a transform coefficient from the entropy decoded signal using the quantization step size information.
- the inverse transform unit 230 inversely transforms the transform coefficient to obtain a residual signal.
- a reconstructed signal is generated by adding the obtained residual signal to a prediction signal output from the inter predictor 260 or the intra predictor 265.
- the filtering unit 240 applies filtering to the reconstructed signal and outputs the filtering to the reproducing apparatus or transmits it to the decoded picture buffer unit 250.
- the filtered signal transmitted to the decoded picture buffer unit 250 may be used as the reference picture in the inter predictor 260.
- the embodiments described by the filtering unit 160, the inter prediction unit 180, and the intra prediction unit 185 of the encoder 100 are respectively the filtering unit 240, the inter prediction unit 260, and the decoder. The same may be applied to the intra predictor 265.
- FIG. 3 is a diagram for describing a division structure of a coding unit according to an embodiment to which the present invention is applied.
- the encoder may split one image (or picture) in units of a rectangular Coding Tree Unit (CTU).
- CTU Coding Tree Unit
- one CTU is sequentially encoded according to a raster scan order.
- the size of the CTU may be set to any one of 64x64, 32x32, and 16x16, but the present invention is not limited thereto.
- the encoder may select and use the size of the CTU according to the resolution of the input video or the characteristics of the input video.
- the CTU may include a coding tree block (CTB) for a luma component and a coding tree block (CTB) for two chroma components corresponding thereto.
- One CTU may be decomposed into a quadtree (QT) structure.
- QT quadtree
- one CTU may be divided into four units having a square shape and each side is reduced by half in length.
- the decomposition of this QT structure can be done recursively.
- a root node of a QT may be associated with a CTU.
- the QT may be split until it reaches a leaf node, where the leaf node may be referred to as a coding unit (CU).
- CU coding unit
- a CU may mean a basic unit of coding in which an input image is processed, for example, intra / inter prediction is performed.
- the CU may include a coding block (CB) for a luma component and a CB for two chroma components corresponding thereto.
- CB coding block
- the size of the CU may be determined as any one of 64x64, 32x32, 16x16, and 8x8.
- the present invention is not limited thereto, and in the case of a high resolution image, the size of the CU may be larger or more diverse.
- the CTU corresponds to a root node and has the smallest depth (ie, level 0) value.
- the CTU may not be divided according to the characteristics of the input image. In this case, the CTU corresponds to a CU.
- the CTU may be decomposed in QT form, and as a result, lower nodes having a depth of level 1 may be generated. And, a node that is no longer partitioned (ie, a leaf node) in a lower node having a depth of level 1 corresponds to a CU.
- CU (a), CU (b) and CU (j) corresponding to nodes a, b and j are divided once in the CTU and have a depth of level 1.
- At least one of the nodes having a depth of level 1 may be split into QT again.
- a node that is no longer partitioned (ie, a leaf node) in a lower node having a level 2 depth corresponds to a CU.
- CU (c), CU (h), and CU (i) corresponding to nodes c, h and i are divided twice in the CTU and have a depth of level 2.
- At least one of the nodes having a depth of 2 may be divided into QTs.
- a node that is no longer partitioned (ie, a leaf node) in a lower node having a depth of level 3 corresponds to a CU.
- CU (d), CU (e), CU (f), and CU (g) corresponding to nodes d, e, f, and g are divided three times in the CTU, and level 3 Has a depth of
- the maximum size or the minimum size of the CU may be determined according to characteristics (eg, resolution) of the video image or in consideration of encoding efficiency. Information about this or information capable of deriving the information may be included in the bitstream.
- a CU having a maximum size may be referred to as a largest coding unit (LCU), and a CU having a minimum size may be referred to as a smallest coding unit (SCU).
- LCU largest coding unit
- SCU smallest coding unit
- a CU having a tree structure may be hierarchically divided with predetermined maximum depth information (or maximum level information).
- Each partitioned CU may have depth information. Since the depth information indicates the number and / or degree of division of the CU, the depth information may include information about the size of the CU.
- the size of the SCU can be obtained by using the size and maximum depth information of the LCU. Or conversely, using the size of the SCU and the maximum depth information of the tree, the size of the LCU can be obtained.
- information indicating whether the corresponding CU is split may be delivered to the decoder.
- the information may be defined as a split flag and may be represented by a syntax element "split_cu_flag".
- the division flag may be included in all CUs except the SCU. For example, if the split flag value is '1', the corresponding CU is divided into four CUs again. If the split flag value is '0', the CU is not divided any more and the coding process for the CU is not divided. Can be performed.
- the division process of the CU has been described as an example, but the QT structure described above may also be applied to the division process of a transform unit (TU) which is a basic unit for performing transformation.
- TU transform unit
- the TU may be hierarchically divided into a QT structure from a CU to be coded.
- a CU may correspond to a root node of a tree for a transform unit (TU).
- the TU divided from the CU may be divided into smaller lower TUs.
- the size of the TU may be determined by any one of 32x32, 16x16, 8x8, and 4x4.
- the present invention is not limited thereto, and in the case of a high resolution image, the size of the TU may be larger or more diverse.
- information indicating whether the corresponding TU is divided may be delivered to the decoder.
- the information may be defined as a split transform flag and may be represented by a syntax element "split_transform_flag".
- the division conversion flag may be included in all TUs except the TU of the minimum size. For example, if the value of the division conversion flag is '1', the corresponding TU is divided into four TUs again. If the value of the division conversion flag is '0', the corresponding TU is no longer divided.
- a CU is a basic unit of coding in which intra prediction or inter prediction is performed.
- a CU may be divided into prediction units (PUs).
- the PU is a basic unit for generating a prediction block, and may generate different prediction blocks in PU units within one CU.
- the PU may be divided differently according to whether an intra prediction mode or an inter prediction mode is used as a coding mode of a CU to which the PU belongs.
- FIG. 4 is a diagram for describing a prediction unit according to an embodiment to which the present invention is applied.
- the PU is divided differently according to whether an intra prediction mode or an inter prediction mode is used as a coding mode of a CU to which the PU belongs.
- FIG. 4A illustrates a PU when an intra prediction mode is used
- FIG. 4B illustrates a PU when an inter prediction mode is used.
- one CU may be divided into two types (ie, 2Nx2N or NxN). Can be.
- N ⁇ N type PU when divided into N ⁇ N type PU, one CU is divided into four PUs, and different prediction blocks are generated for each PU unit.
- the division of the PU may be performed only when the size of the CB for the luminance component of the CU is the minimum size (that is, the CU is the SCU).
- one CU has 8 PU types (ie, 2Nx2N, NxN, 2NxN). , Nx2N, nLx2N, nRx2N, 2NxnU, 2NxnD).
- PU splitting in the form of NxN may be performed only when the size of the CB for the luminance component of the CU is the minimum size (that is, the CU is the SCU).
- nLx2N, nRx2N, 2NxnU, and 2NxnD types which are Asymmetric Motion Partition (AMP).
- 'n' means a 1/4 value of 2N.
- AMP cannot be used when the CU to which the PU belongs is a CU of the minimum size.
- an optimal partitioning structure of a coding unit (CU), a prediction unit (PU), and a transformation unit (TU) is subjected to the following process to perform a minimum rate-distortion. It can be determined based on the value. For example, looking at an optimal CU partitioning process in a 64x64 CTU, rate-distortion cost can be calculated while partitioning from a 64x64 CU to an 8x8 CU.
- the specific process is as follows.
- the partition structure of the optimal PU and TU that generates the minimum rate-distortion value is determined by performing inter / intra prediction, transform / quantization, inverse quantization / inverse transform, and entropy encoding for a 64x64 CU.
- the 32x32 CU is subdivided into four 16x16 CUs, and a partition structure of an optimal PU and TU that generates a minimum rate-distortion value for each 16x16 CU is determined.
- a prediction mode is selected in units of PUs, and prediction and reconstruction are performed in units of actual TUs for the selected prediction mode.
- the TU means a basic unit in which actual prediction and reconstruction are performed.
- the TU includes a transform block (TB) for a luma component and a TB for two chroma components corresponding thereto.
- TB transform block
- the TUs are hierarchically divided into quadtree structures from one CU to be coded.
- the TU divided from the CU may be divided into smaller lower TUs.
- the size of the TU may be set to any one of 32 ⁇ 32, 16 ⁇ 16, 8 ⁇ 8, and 4 ⁇ 4.
- a root node of the quadtree is associated with a CU.
- the quadtree is split until it reaches a leaf node, and the leaf node corresponds to a TU.
- the CU may not be divided according to the characteristics of the input image.
- the CU corresponds to a TU.
- a node ie, a leaf node
- TU (a), TU (b), and TU (j) corresponding to nodes a, b, and j are divided once in a CU and have a depth of 1.
- FIG. 3B TU (a), TU (b), and TU (j) corresponding to nodes a, b, and j are divided once in a CU and have a depth of 1.
- a node (ie, a leaf node) that is no longer divided in a lower node having a depth of 2 corresponds to a TU.
- TU (c), TU (h), and TU (i) corresponding to nodes c, h, and i are divided twice in a CU and have a depth of two.
- a node that is no longer partitioned (ie, a leaf node) in a lower node having a depth of 3 corresponds to a CU.
- TU (d), TU (e), TU (f), and TU (g) corresponding to nodes d, e, f, and g are divided three times in a CU. Has depth.
- a TU having a tree structure may be hierarchically divided with predetermined maximum depth information (or maximum level information). Each divided TU may have depth information. Since the depth information indicates the number and / or degree of division of the TU, it may include information about the size of the TU.
- information indicating whether the corresponding TU is split may be delivered to the decoder.
- This partitioning information is included in all TUs except the smallest TU. For example, if the value of the flag indicating whether to split is '1', the corresponding TU is divided into four TUs again. If the value of the flag indicating whether to split is '0', the corresponding TU is no longer divided.
- FIG. 5 to 7 illustrate embodiments to which the present invention is applied.
- FIG. 5 is a diagram illustrating an intra prediction method
- FIG. 6 is a diagram illustrating a prediction direction according to an intra prediction mode
- FIG. 7 is a subpixel.
- the decoder may derive an intra prediction mode of the current processing block (S501).
- the prediction direction may have a prediction direction with respect to the position of the reference sample used for the prediction according to the prediction mode.
- an intra prediction mode having a prediction direction is referred to as an intra_angular prediction mode or an intra directional mode.
- an intra prediction mode having no prediction direction there are an intra planner (INTRA_PLANAR) prediction mode and an intra DC (INTRA_DC) prediction mode.
- Table 1 illustrates an intra prediction mode and related names
- FIG. 6 illustrates a prediction direction according to the intra prediction mode.
- intra prediction prediction is performed on the current processing block based on the derived prediction mode. Since the reference sample used for the prediction and the specific prediction method vary according to the prediction mode, when the current block is encoded in the intra prediction mode, the decoder may derive the prediction mode of the current block to perform the prediction.
- the decoder may check whether neighboring samples of the current processing block can be used for prediction and configure reference samples to be used for prediction (S502).
- neighboring samples of the current processing block are samples adjacent to the left boundary of the current processing block of size nSxnS and a total of 2xnS samples neighboring the bottom-left, top of the current processing block.
- the decoder can construct reference samples for use in prediction by substituting samples that are not available with the available samples.
- the decoder may perform filtering of reference samples based on the intra prediction mode (S503).
- Whether filtering of the reference sample is performed may be determined based on the size of the current processing block.
- the filtering method of the reference sample may be determined by the filtering flag transmitted from the encoder.
- the decoder may generate a prediction block for the current processing block based on the intra prediction mode and the reference samples (S504). That is, the decoder predicts the current processing block based on the intra prediction mode derived in the intra prediction mode derivation step S501 and the reference samples obtained through the reference sample configuration step S502 and the reference sample filtering step S503.
- a block may be generated (ie, predictive sample generation).
- the left boundary sample ie, the sample in the prediction block adjacent to the left boundary
- the upper side of the prediction block in step S504.
- (top) boundary samples i.e., samples in prediction blocks adjacent to the upper boundary
- filtering may be applied to the left boundary sample or the upper boundary sample in the vertical direction mode and the horizontal mode among the intra directional prediction modes similarly to the INTRA_DC mode.
- the value of the prediction sample may be derived based on a reference sample located in the prediction direction.
- a boundary sample which is not located in the prediction direction among the left boundary sample or the upper boundary sample of the prediction block may be adjacent to a reference sample which is not used for prediction. That is, the distance from the reference sample not used for prediction may be much closer than the distance from the reference sample used for prediction.
- the decoder may adaptively apply filtering to left boundary samples or upper boundary samples depending on whether the intra prediction direction is vertical or horizontal. That is, when the intra prediction direction is the vertical direction, the filtering may be applied to the left boundary samples, and when the intra prediction direction is the horizontal direction, the filtering may be applied to the upper boundary samples.
- FIG. 7 is a diagram for describing a method of interpolating a reference pixel at a subpixel position.
- the directional prediction method for constructing a prediction block by copying reference pixels located in a specific direction and making the most of the referenceable pixels are used. It can be divided into non-directional prediction methods (DC mode, planar mode).
- the directional prediction method is designed to express the structure of various directions that can appear on the screen.
- the directional prediction method may be performed by designating a specific direction as a mode and then copying a reference pixel corresponding to the prediction mode angle around the position of the sample to be predicted.
- the interpolated pixel is copied by using the distance ratio between the two corresponding pixels and the two pixels obtained by the angle as shown in FIG. Can be.
- the X coordinate Xsub of the sub reference pixel T may be obtained according to Equation 1 below.
- d represents a distance between the pixel A and the pixel E
- ⁇ represents an angle along the prediction direction
- the pixel value of the sub-reference pixel T can be obtained based on the distance ratio between two adjacent integer pixels, pixel B and pixel C.
- a prediction pixel value corresponding to the pixel E may be determined based on the pixel value of the sub reference pixel T.
- FIG. 8 is a diagram for describing an angle parameter according to an intra prediction mode according to an embodiment to which the present invention is applied.
- FIG. 8 (a) shows the intra directional prediction mode, and it can be seen that eight angles are defined for each octant according to 1/32 precision.
- FIG. 8B illustrates an angle parameter according to the intra prediction mode.
- the angle parameter refers to a prediction angle corresponding to an intra prediction mode and may be represented as 'intraPredAngle'.
- the prediction sample may be obtained by projecting onto a reference array according to the angle of the intra prediction mode. For example, when the intra prediction mode is 18 or more, the prediction sample is obtained through Equations 2 to 4 below. Can be.
- 'iIdx' means a position of an adjacent integer sample when projected onto a reference array
- 'iFact' means a fraction of a position of an integer sample
- FIG. 9 illustrates an embodiment to which the present invention is applied and adaptively selects a mode when the intra prediction mode has 1 / M precision.
- the prediction direction has a +/- [0, 2, 5, 9, 13, 17, 21, 26, 32] / 32 angle.
- the angle represents the difference between the lower row of the PU and the reference row above the PU in the vertical mode, and the difference between the rightmost column and the left reference column of the PU in the horizontal mode. Then, pixel reconstruction is achieved by using linear interpolation of upper or left reference samples with 1/32 pixel accuracy.
- the present invention can adaptively select at least one of the number of modes or the mode positions in intra prediction.
- FIG. 9 is an embodiment to which the present invention is applied, and may adaptively select the number L of modes corresponding to an angle within an area corresponding to 45 ° to the right in the intra vertical mode.
- the present invention provides a method for adaptively selecting a mode number L in intra prediction.
- the mode number L may be differently selected according to the characteristics of the image of the current block.
- the characteristic of the image of the current block may be confirmed from surrounding reconstructed samples.
- a reference sample (or reference array) used in intra prediction may be used.
- the reference sample may be samples at positions p (-1, -2N + 1) to p (-1, -1) to p (2N-1, -1).
- the characteristic of the image may be determined by an upper reference array or a left reference array.
- the present invention is not limited to the upper or left sample array.
- two rows of top or left sample arrays or more may be used.
- the encoder or decoder to which the present invention is applied may determine the minimum number of modes L for intra prediction.
- edge inspection or the like may be used as a method of determining whether the characteristics of the image are homogeneous. If it is determined that there is a strong edge in a particular part during imaging, many directional modes can be allocated intensively.
- various measurement methods may be used to determine characteristics of an image, for example, information such as average, variance, edge intensity, and edge direction of pixel values.
- FIG. 10 is a schematic block diagram of an encoder for encoding an adaptively selected mode in intra prediction, according to an embodiment to which the present invention is applied.
- the encoder to which the present invention is applied schematically shows the encoder block diagram of FIG. 1, and focuses on the functions of the parts to which the present invention is applied.
- the encoder may include a prediction direction inducer 1000 and an intra predictor 1010.
- the prediction direction inducing unit 1000 may determine a dominant direction based on the information of the neighboring blocks.
- L modes may be selected based on the dominant direction of the neighboring block.
- the prediction direction deriving unit 1000 may transmit the selected L modes to the entropy encoding unit, and transmit the total number M of intra prediction modes to the intra prediction unit 1010.
- the intra prediction unit 1010 may determine an optimal prediction mode among the M intra prediction modes transmitted from the prediction direction deriving unit 1000.
- the determined optimal prediction mode may be transmitted to the entropy encoding unit.
- FIG. 11 is a schematic block diagram of a decoder for decoding an adaptively selected mode in intra prediction as an embodiment to which the present invention is applied.
- the decoder to which the present invention is applied schematically shows the decoder block diagram of FIG. 2, and focuses on the functions of the parts to which the present invention is applied.
- the decoder may include a prediction direction deriving unit 1100 and an intra predicting unit 1110.
- the prediction direction deriving unit 1100 may transmit the selected number of L intra prediction modes to the entropy decoding unit, and the entropy decoding unit may perform entropy decoding based on the selected mode number L.
- the entropy decoding unit may receive a video signal, and transmit an intra prediction mode to the intra prediction unit 1110.
- the intra prediction unit 1110 may perform intra prediction by receiving an intra prediction mode.
- the predicted value output through the intra prediction is summed with the residual value subjected to inverse quantization and inverse transformation to reconstruct the video signal.
- FIGS. 12 to 15 are embodiments to which the present invention is applied, and FIGS. 12 to 13 are diagrams for explaining various intra directional prediction modes according to prediction accuracy, and FIG. 14 is an angle parameter corresponding to each intra directional prediction mode. (angle parameter) is shown in a table, and FIG. 15 shows a method of obtaining a prediction sample according to a newly defined intra direction prediction mode.
- the present invention provides a method for defining an intra directional prediction mode with more direction and precision.
- Example 1 has 1/32 precision, the number of prediction modes per eighth octant is eight and the total number of directional prediction modes is 33 Indicates an individual case.
- Example 2 has a 1/16 precision, and the number of prediction modes per eighth octant is 16 and the total number of directional prediction modes is 65. .
- Example 3 has a 1/32 precision, and the number of prediction modes per eighth octant is 32 and the total number of directional prediction modes is 129. .
- Example 4 has a 1/64 precision, and the number of prediction modes per eighth octant is 64 and the total number of directional prediction modes is 257. .
- 15 (a) to 15 (d) show equations for obtaining prediction samples in each of the first to fourth embodiments.
- the present invention can increase prediction accuracy and further improve coding efficiency by defining an intra directional prediction mode having more direction and precision in intra prediction coding.
- FIG. 16 is a diagram for describing a scan order used in intra prediction as an embodiment to which the present invention is applied.
- Intra-coded blocks have different scan indices (scanIdx) according to prediction modes at specific block sizes.
- scanIdx scan indices
- the 8x8 TU shows a diagonal scan order, a horizontal scan order, and a vertical scan order.
- the scan index scanIdx may be defined as follows. 0 indicates an up-right diagonal scan order, 1 indicates a horizontal scan order, 2 indicates a vertical scan order, and 0 indicates a vertical scan order. Indicates.
- the scan index scanIdx may be derived based on at least one of a prediction mode and a size of a transform block. For example, it can be derived through the following process.
- the scan index scanIdx may be derived as follows.
- the scan index scanIdx may be set to 2
- the scan index scanIdx may be set to 1. have.
- the scan index scanIdx may be set to zero.
- the present invention is not limited to the above embodiment, and when various intra prediction modes described herein are defined, an application range of the intra prediction mode may be set differently according to the corresponding embodiment.
- FIG. 17 to 18 illustrate embodiments to which the present invention is applied.
- FIG. 17 illustrates a method of allocating a scan index according to a newly defined intra direction prediction mode
- FIG. 18 illustrates a scan index allocated according to an intra direction prediction mode. Indicates.
- FIG. 17 various embodiments of allocating a scan index based on an intra prediction mode are illustrated. 17 to 18 correspond to the embodiments described with reference to FIGS. 12 to 15, respectively.
- 17A illustrates a method of allocating a scan index based on an intra prediction mode when the number of prediction modes per eighth octant is 33 and the total number of directional prediction modes is 33.
- FIG. 17A illustrates a method of allocating a scan index based on an intra prediction mode when the number of prediction modes per eighth octant is 33 and the total number of directional prediction modes is 33.
- the scan index scanIdx is set to 2. If the intra prediction mode is 22 to 30, the scan index scanIdx is set to 1. Otherwise, the scan index scanIdx is 0. Can be set.
- a scan index (scanIdx) of 0 indicates an up-right diagonal scan order, 1 indicates a horizontal scan order, and 2 indicates a vertical scan order. Indicates.
- Example 2 when the number of prediction modes per eighth octet is 16 and the total number of directional prediction modes is 65, a method of allocating a scan index based on the intra prediction mode is provided. Indicates.
- the scan index scanIdx is set to 2. If the intra prediction mode is 42 to 58, the scan index scanIdx is set to 1. Otherwise, the scan index scanIdx is 0. Can be set.
- Example 3 when the number of prediction modes per eighth octant is 32 and the number of total directional prediction modes is 129, a method of allocating a scan index based on the intra prediction mode is provided. Indicates.
- the scan index (scanIdx) is set to 2; if the intra prediction mode is 82 to 114, the scan index (scanIdx) is set to 1; otherwise, the scan index (scanIdx) is 0 Can be set.
- the scan index (scanIdx) is set to 2 when the intra prediction mode is 34 to 98, and the scan index (scanIdx) is set to 1 when the intra prediction mode is 162 to 226, and the scan index (scanIdx) is 0 otherwise. Can be set.
- 18 (a) to 18 (d) show scan indexes scanIdx corresponding to each of the first to fourth embodiments.
- 19 to 21 are diagrams for explaining scan orders of coefficients in a TU as embodiments to which the present invention is applied.
- the scan order shown in FIG. 19 may be used at 16x16 TU or more while maintaining the 4x4 subgroup as it is (maintaining scan orders within the 4x4 block). It can be extended in the same way for 32x32 TU and 64x64 TU.
- 19 (a), 19 (b), and 19 (c) define scan orders of 16 ⁇ 16 TUs, and represent diagonal scan orders, horizontal scan orders, and vertical scan orders in units of 4 ⁇ 4 blocks, respectively.
- the scan may be performed according to the number described in the 4x4 block.
- a basic subgroup may be extended to fit the TU size.
- the size of a subgroup may be extended to 8x8.
- the subgroup size may be 8x8 in all 16x16 TU or more.
- the size of the subgroup may be extended in proportion to the TU size.
- an 8x8 TU may use a subgroup size of 4x4, a 16x16 TU may be 8x8, and a 32x32 TU may be used as 16x16.
- a subgroup is extended to 16x16 in a 32x32 TU.
- the scan order in a subgroup can use the scan order in a 4x4 block as it is.
- FIG. 22 is a diagram for describing a method of changing an interval between angle parameters according to an embodiment to which the present invention is applied.
- a predictor When performing intra prediction, a predictor is generated using sample values around the current block.
- the predictor may be generated through an average or weighted average of the surrounding samples, or by copying the surrounding samples in a particular direction.
- the direction in the image is mostly biased in the horizontal direction and the vertical direction, but there are cases where the distribution of the image is different depending on the image content.
- the direction in the image may be biased in the diagonal direction.
- the present invention provides a method for changing the spacing between angle parameters.
- the angle parameter means a prediction angle corresponding to the intra prediction mode and may be expressed as 'intraPredAngle'.
- the angle parameter may be used to define a direction or indicate a position in the intra directional prediction mode.
- the angle parameter corresponding to each prediction mode may be defined as [0 2 5 9 13 17 21 26 32]. This is also an intraPredAngle value corresponding to intra prediction modes 26 to 34, as described with reference to FIG. 14 (a).
- an interval between angle parameters becomes [2 3 4 4 4 4 5 6], which can be seen in FIG.
- an interval between angle parameters is called an angle interval, and in some cases, it is called interval information or displacement difference.
- An embodiment of the present invention may flip the angle interval to flip the direction of the predefined prediction mode in another direction.
- the angle interval when the angle interval is configured as [2 3 4 4 4 4 5 6], that is, the prediction modes are biased in the vertical direction.
- the angle interval when the angle interval [2 3 4 4 4 5 6] is flipped, the angle interval may be changed as [6 5 4 4 4 4 3 2]. . This may confirm that prediction modes are biased in the diagonal direction according to the changed angle interval.
- the present invention can perform more sophisticated prediction by changing the predefined prediction modes to be biased in a specific direction according to the characteristics of the image.
- the angle parameter may be derived from the transmitted angle interval information at the decoder after transmitting the angle interval information without explicitly transmitting the angle parameter.
- information on whether to flip the angle interval may be defined. For example, when the flip flag flip_flag is information indicating whether to flip the angle interval, the flip flag is 1 to indicate the flip of the angle interval. In this case, a flip of an angle interval is not performed.
- the flip flag flip_flag may be defined in units of a horizontal direction and a vertical direction.
- the decoder may receive the intra prediction mode, check whether the intra prediction mode is vertical or horizontal, and then check whether the flip is performed in the vertical direction or the horizontal direction.
- the flip flag flip_flag may be defined for each quarter in units of 45 degrees.
- the flip flag flip_flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- the encoder or decoder may use a predefined flip table or derive from other information when not performing flip of the angle interval.
- the encoder or the decoder may have at least one angle parameter set or angle interval set.
- the flip table may be calculated based on a set of precision and angle parameters, or may be calculated based on an angle interval.
- the flip table uses Equation 5 below. Can be calculated.
- the flip table can be calculated by subtracting the angle parameter in the reverse order from the value indicating the precision. For example, if an angle parameter set is defined as [0, 2, 5, 9, 13, 17, 21, 26, 32], the flip table is ⁇ 0, 6, 11, 15, 19. , 23, 27, 30, 32 ⁇ .
- a predefined angle parameter set (or angle parameter table) may be used according to the flip flag, or a flip table may be used.
- FIG. 23 is a diagram for describing a method of changing an interval between angle parameters in units of a 45 degree region according to an embodiment to which the present invention is applied.
- an intra prediction adaptive to a characteristic of an image may be performed by defining a flip flag in a specific area unit.
- the flip flag may be defined in units of 45 degrees.
- the prediction mode may be biased in the diagonal direction only in the first 45 degree region through the above setting.
- the flip flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- FIG. 24 is a diagram for describing a method of changing an interval between angle parameters in units of a horizontal / vertical region as an embodiment to which the present invention is applied.
- an intra prediction adaptive to a characteristic of an image may be performed by defining a flip flag in a specific area unit.
- the flip flag may be defined in units of horizontal and vertical regions.
- flip flags indicating whether to flip angle intervals in the horizontal area and the vertical area may be expressed as DirHorFlip and DirVerFlip, respectively.
- FIG. 25 is an embodiment to which the present invention is applied and is a syntax defining a flip flag indicating whether to change an interval between an angle parameter in a sequence parameter set and a slice header.
- the flip flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- the flip flag defined in the sequence parameter set may be defined as sps_intra_dir_flip_flag (S2510).
- the sequence may mean that no flip is performed during intra prediction.
- the flip flag defined in the slice may be defined as slice_intra_dir_flip_flag.
- slice_intra_dir_flip_flag may be dependent on the flip flag of the upper stage.
- slice sp_intra_dir_flip_flag may be defined when sps_intra_dir_flip_flag is 1 in the sequence parameter set (S2520).
- the flip flag defined in the slice may be defined in units of horizontal / vertical regions.
- a flip flag indicating whether to flip the angle interval in the horizontal area may be referred to as hor_flip_flag (S2530), and indicating whether to flip the angle interval in the vertical area.
- the flip flag may be referred to as ver_flip_flag (S2540).
- hor_flip_flag and ver_flip_flag may be examples of slice_intra_dir_flip_flag.
- hor_flip_flag 1
- the flip of the angular interval is performed when the intra prediction mode is 2 to 17
- hor_flip_flag 0
- the flip of the angular interval is not performed when the intra prediction mode is 2 to 17.
- ver _flip_flag 1
- the flip of the angular interval is performed when the intra prediction mode is 18 to 34.
- ver _flip_flag 0
- the flip of the angular interval is not performed when the intra prediction mode is 18 to 34.
- Another embodiment of the present invention provides a method of obtaining a prediction sample based on a flip flag.
- isIntraAngleFlip may be set to '2 + hor_flip_flag', and if it is not 1, it may be set to hor_flip_flag value.
- the isIntraAngleFlip may be used as an input value for obtaining prediction samples.
- the present invention may define a variable intraFlip indicating a flip in the horizontal or vertical direction, and obtain a prediction sample based on the intraFlip.
- the angle parameter intraPredAngle may be defined as follows.
- absIntraPredAngle may be set to Abs (intraPredAngle).
- a mapping table between absIntraPredAngle and flip angle variable (flipIntraPredAngle) may be defined as shown in Table 3 below.
- intraPredAngle may be defined as follows.
- intra prediction mode predModeIntra
- intraPredAngle flipIntraPredAngle
- intraPredAngle (-) flipIntraPredAngle may be set.
- intraPredAngle may be defined as follows.
- intra prediction mode predModeIntra
- intraPredAngle flipIntraPredAngle
- intraPredAngle ( ⁇ ) flipIntraPredAngle may be set.
- intraPredAngle may be defined as follows.
- intraPredAngle flipIntraPredAngle may be set.
- intraPredAngle may be set to (-) flipIntraPredAngle.
- invAngle may be set to 256 * 32 / intraPredAngle.
- FIG. 26 is a flowchart illustrating a process of performing intra prediction according to a flip flag according to an embodiment to which the present invention is applied.
- the decoder may obtain a flip flag from the received video signal (S2610).
- the flip flag may mean whether to perform flip in intra prediction, which may be defined at various levels in the video signal.
- the flip flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- the decoder may check whether the flip flag is 1 (S2620). As a result of the check, if the flip flag is 1, it indicates that flip is performed during intra prediction, and if it is 0, it indicates that flip is not performed during intra prediction. In addition, when the flip flag does not exist, it may mean that no flip is performed during intra prediction.
- the decoder may induce a flip angle variable (flipintraPredAngle) according to the prediction mode (S2630).
- the flip angle variable flipintraPredAngle may be defined as a value corresponding to the angle parameter intraPredAngle as shown in Table 2 above.
- the angle parameter intraPredAngle may be a value set according to a prediction mode.
- Intra prediction may be performed based on the flip angle variable flipintraPredAngle (S2640).
- intra prediction may be performed based on the angle parameter intraPredAngle (S2650).
- the angle parameter intraPredAngle may be set to a value corresponding to the intra prediction mode as described with reference to FIG. 14.
- FIG. 27 is a flowchart illustrating a process of performing intra prediction according to a flip flag in units of a horizontal / vertical region according to an embodiment to which the present invention is applied.
- the decoder may obtain a sequence flip flag from a sequence parameter set (S2710).
- the sequence may mean that no flip is performed during intra prediction.
- the decoder may check whether the sequence flip flag sps_intra_dir_flip_flag is 1 (S2720).
- the sequence flip flag sps_intra_dir_flip_flag is 1, at least one of a horizontal flip flag and a vertical flip flag may be obtained from a slice header (S2730).
- the horizontal flip flag indicates whether or not to flip the angle interval in the horizontal region, which may be represented by hor_flip_flag
- the vertical flip flag is the angle of the angle interval (vertical interval) in the vertical region Indicates whether to perform a flip, which may be expressed as ver_flip_flag.
- the decoder uses intra prediction using at least one of an angle parameter and an inverse angle parameter. It may be performed (S2780).
- the decoder may check whether the horizontal flip flag hor_flip_flag is 1 (S2740).
- the flip of the angle interval is performed when the intra prediction mode is 2 to 17.
- a flip may be performed on at least one of an angle parameter and an inverse angle parameter (S2750).
- the decoder may check whether the vertical flip flag ver_flip_flag is 1 (S2760).
- the flip of the angle interval is performed when the intra prediction mode is 18 to 34.
- a flip may be performed on at least one of an angle parameter and an inverse angle parameter (S2770).
- the decoder may perform intra prediction using at least one of a flipped angle parameter and an inverse angle parameter (S2780).
- the decoder does not perform the flip of the angle interval when the intra prediction mode is 2 to 17, and the decoder determines whether the vertical flip flag ver_flip_flag is 1 or not. You can check.
- the decoder determines the angle parameter and the inverse angle parameter.
- Intra prediction may be performed using at least one of an inverse angle parameter.
- a sequence flip flag and a horizontal / vertical flip flag at a slice level have been described as examples, but the present invention is not limited thereto, and the first flip flag and the second flip flag may be described using the terms.
- the second flip flag may mean whether to flip at a lower level than the first flip flag.
- the sequence flip flag is defined as a first flap flag
- the second flip flag may mean whether to perform flip during intra prediction at the slice level.
- the first, second and third flip flags may be used at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, and a prediction unit.
- FIG. 28 is a diagram for describing a method of explicitly transmitting interval information between angle parameters according to an embodiment to which the present invention is applied.
- the present invention provides a method of changing and signaling the distance between angle parameters.
- the angle parameter means a prediction angle corresponding to the intra prediction mode and may be expressed as 'intraPredAngle'.
- the angle parameter may be used to define a direction or indicate a position in the intra directional prediction mode.
- the angle parameter corresponding to each prediction mode may be defined as [0 2 5 9 13 17 21 26 32]. This is also an intraPredAngle value corresponding to intra prediction modes 26 to 34, as described with reference to FIG. 14 (a).
- the angle interval when the angle interval is configured as [2 3 4 4 4 4 5 6], that is, the prediction modes are biased in the vertical direction.
- the angle interval when the angle interval [2 3 4 4 4 5 6] is flipped, the angle interval may be changed as [6 5 4 4 4 4 3 2]. . This may confirm that prediction modes are biased in the diagonal direction according to the changed angle interval.
- the present invention proposes a method for signaling and transmitting the changed angle interval as described above.
- the changed angle interval may be transmitted at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, an LCU, a CU, and a PU.
- the changed angle interval [6 5 4 4 4 4 3 2] is signaled to generate a sequence parameter set, picture parameter set, slice, block, LCU, CU, and PU. It may be transmitted at at least one level.
- the decoder may configure the intra prediction mode by receiving the changed angle interval and perform intra prediction based on the intra prediction mode.
- FIG. 29 is a diagram for describing a method of explicitly transmitting interval information between angle parameters in units of a 45 degree region according to an embodiment to which the present invention is applied.
- the present invention defines an angle transmission flag in units of a specific region and performs adaptive intra prediction by transmitting at least one of an angle interval or an angle parameter in units of the specific region. can do.
- the angle transmission flag indicates whether to transmit prediction angle information, which may be expressed as explicit_angle_flag.
- the prediction angle information is information indicating an intra prediction direction and may include at least one of an angle interval or an angle parameter. For example, if explicit_angle_flag is 1, prediction angle information is transmitted. If explicit_angle_flag is 0, prediction angle information is not transmitted. If explicit_angle_flag does not exist, this indicates that prediction angle information is not transmitted.
- the prediction angle information may include at least one of a flipped angle interval or a flipped angle parameter.
- an angle transmission flag may be defined in units of a 45 degree region, and at least one of an angle interval or an angle parameter may be transmitted in units of a 45 degree region.
- Equation 7 when only the first 45 degree region transmits prediction angle information, it may be set as in Equation 7 below.
- the prediction mode is biased in the diagonal direction only in the first 45 degree region through the above setting, and only the angular interval in the first 45 degree region can be transmitted.
- Equation 8 when only the first and third 45 degree regions transmit the prediction angle information, Equation 8 may be set.
- the first 45 degree region may be biased in the prediction mode in the diagonal direction
- the third 45 degree region may be biased in the prediction mode in the diagonal direction and the vertical direction.
- the angular spacing of the first 45 degree region and the angular spacing of the third 45 degree region can be transmitted.
- the flip flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- FIG. 30 is a diagram for explaining a method of explicitly transmitting interval information between angle parameters in units of a horizontal / vertical region according to an embodiment to which the present invention is applied.
- the present invention defines an angle transmission flag in units of a specific region and performs adaptive intra prediction by transmitting at least one of an angle interval or an angle parameter in units of the specific region. can do.
- the angle transmission flag indicates whether to transmit prediction angle information, which may be expressed as explicit_angle_flag.
- the prediction angle information is information indicating an intra prediction direction and may include at least one of an angle interval or an angle parameter.
- the prediction angle information may include at least one of a flipped angle interval or a flipped angle parameter.
- an angle transmission flag may be defined in units of a horizontal / vertical region, and at least one of an angle interval or an angle parameter may be transmitted in units of a horizontal / vertical region.
- Equation 9 when only the first 45 degree region transmits prediction angle information, it may be set as in Equation 9 below.
- the prediction mode is biased in the diagonal direction only in the horizontal area through the above setting, and only the angular interval in the horizontal area can be transmitted.
- the prediction mode may be biased in the diagonal direction in the horizontal area and the prediction mode in the vertical direction in the vertical area.
- the angular intervals of the horizontal region and the angular intervals of the vertical region may be transmitted.
- the angle transmission flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- FIG. 31 is a syntax illustrating an embodiment to which the present invention is applied and defines a method of explicitly transmitting interval information between angle parameters.
- the present invention defines an angle transmission flag in units of a specific region and performs adaptive intra prediction by transmitting at least one of an angle interval or an angle parameter in units of the specific region. can do.
- the angle transmission flag indicates whether to transmit prediction angle information
- the prediction angle information is information indicating an intra prediction direction, and includes at least one of an angle interval or an angle parameter. It may include one.
- the prediction angle information may include at least one of a flipped angle interval or a flipped angle parameter.
- the angle transmission flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- the angle transmission flag is sps_explicit_displacement_flag. It can be expressed as.
- sps_explicit_displacement_flag may be referred to as a sequence angle transmission flag, and the sequence angle transmission flag may mean whether to transmit prediction angle information at a sequence level (S3110). Alternatively, the sequence angle transmission flag may mean whether the sequence has explicit prediction direction information. Alternatively, the sequence angle transmission flag may mean whether the sequence has explicit intra prediction direction information.
- sps_explicit_displacement_flag 1, this indicates that prediction angle information is transmitted at the sequence level, and 0 indicates that no prediction angle information is transmitted at the sequence level.
- the sequence may mean that the prediction angle information is not transmitted.
- an angular transmission flag defined in a slice may be defined as slice_explicit_displacement_flag.
- slice_explicit_displacement_flag may be dependent on the angle transmission flag of the upper stage.
- slice_explicit_displacement_flag may be defined when sps_explicit_displacement_flag is 1 in the sequence parameter set.
- the angle transmission flag defined in the slice may be defined in units of 45 degree region.
- the angle transmission flag in units of the 45 degree region will be referred to as a quarter angle transmission flag.
- the quarter angle transmission flag may indicate whether prediction angle information is transmitted when the intra prediction modes are 2 to 9, 10 to 17, 18 to 25, and 26 to 33, respectively.
- sps_explicit_displacement_flag 1 (S3120)
- the prediction angle information may be obtained based on the quarter angle transmission flag dirQuarterFlag [i].
- the prediction angle information is information indicating an intra prediction direction and may include at least one of an angle interval or an angle parameter.
- n 0, 1, 2, 3, 4, 5, 6, 7
- the angular interval may be expressed as disp_val [i] [n].
- n may be defined as eight when eight prediction modes exist within a 45 degree interval.
- the present invention is not limited thereto, and n may be variable based on the number of prediction modes.
- the sum of the disp_val [i] [n] values may mean precision, for example, 32 in this embodiment.
- the prediction direction position in the 45 degree region may be obtained as in Equation 11 below.
- DispVal [i] [j] represents the prediction direction position in the 45 degree region
- disp_val [i] [n] represents the angular interval between prediction modes.
- the prediction direction position in the 45 degree region starts at 0, and the next prediction direction position can be known by adding the obtained angular interval disp_val [i] [n].
- the prediction angle information may include at least one of a flipped angle interval or a flipped angle parameter.
- Another embodiment of the present invention provides a method of obtaining a prediction sample based on an angle transmission flag.
- iDispValIdx may be set as in Equation 12 below.
- angle parameter intraPredAngle may be defined as follows.
- iIdx may be set to ((predIntraMode-2) / 8).
- iIdx represents a 45 degree region corresponding to the intra prediction mode and may be set as in Equation 13.
- the angle parameter intraPredAngle and the inverse angle parameter invAngle may be derived as follows.
- iDispValIdx may be set to (8 ⁇ iDispValIdx ⁇ 2).
- the angle parameter intraPredAngle may be set to (signValue * DispVal [iIdx] [iDispValIdx]).
- the inverse angle parameter invAngle may be set to (256 * 32 / intraPredAngle).
- Table 4 shows a mapping table between iIdx and startValue
- Table 5 shows a mapping table between iIdx and signtValue.
- the decoder may derive at least one of the angle parameter intraPredAngle and the inverse angle parameter invAngle based on the angle transmission flag.
- the prediction sample may be generated based on at least one of the derived angle parameter intraPredAngle and the inverse angle parameter invAngle.
- 32 is a flowchart illustrating a process of performing intra prediction based on an angle transmission flag according to an embodiment to which the present invention is applied.
- the present invention defines an angle transmission flag in units of a specific region and performs adaptive intra prediction by transmitting at least one of an angle interval or an angle parameter in units of the specific region. can do.
- the decoder may obtain an angle transmission flag from the received video signal (S3210).
- the angle transmission flag indicates whether to transmit prediction angle information.
- the prediction angle information is information indicating an intra prediction direction and may include at least one of an angle interval or an angle parameter.
- the prediction angle information may include at least one of a flipped angle interval or a flipped angle parameter.
- the angle transmission flag may be defined at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, or a coding unit.
- the decoder may check whether the angle transmission flag is 1 (S3220).
- the decoder may obtain prediction angle information (S3230).
- intra prediction may be performed based on an angle parameter intraPredAngle without obtaining additional prediction angle information.
- the decoder may derive at least one of an angle parameter intraPredAngle and an inverse prediction angle based on the prediction angle information in operation S3240.
- Intra prediction may be performed based on at least one of the derived angle parameter intraPredAngle and an inverse prediction angle InvAngle (S3250).
- 33 is a flowchart illustrating a process of performing intra prediction using interval information between angle parameters according to an embodiment to which the present invention is applied.
- the decoder may obtain a sequence angle transmission flag sps_explicit_displacement_flag from the sequence parameter set (S3310).
- the decoder may check whether the sequence angle transmission flag sps_explicit_displacement_flag is 1 (S3320).
- a quarter angle transmission flag dirQuarterFlag [i] and prediction angle information may be obtained from a slice header (S3330).
- the quarter angle transmission flag indicates whether the prediction angle information is transmitted in the 45 degree region. For example, when the intra prediction mode is 2 to 9, 10 to 17, 18 to 25, and 26 to 33, the prediction angle information is displayed. It may indicate whether to transmit.
- the prediction angle information may be obtained based on the quarter angle transmission flag dirQuarterFlag [i].
- the prediction angle information is information indicating an intra prediction direction and may include at least one of an angle interval or an angle parameter.
- the decoder may check whether the quarter angle transmission flag dirQuarterFlag [i] is 1 (S3340).
- intra prediction may be performed based on an angle parameter intraPredAngle without obtaining additional prediction angle information.
- the decoder may derive at least one of an angle parameter intraPredAngle and an inverse prediction angle invAngle based on the prediction angle information in operation S3360.
- Intra prediction may be performed based on at least one of the derived angle parameter intraPredAngle and an inverse prediction angle invAngle (S3370).
- the sequence angle transmission flag and the quarter angle transmission flag of the slice level have been described by way of example, but the present invention is not limited thereto.
- the second angle transmission flag may mean whether prediction angle information is transmitted at a lower level than the first angle transmission flag.
- the sequence angle transmission flag is defined as a first angle transmission flag
- the second angle transmission flag may mean whether to transmit prediction angle information in intra prediction at the slice level.
- the first, second, and third angle transmission flags may be used at at least one level of a sequence parameter set, a picture parameter set, a slice, a block, and a prediction unit.
- FIG. 34 is a diagram for explaining a method of setting intra directional prediction modes at non-uniform intervals according to an embodiment to which the present invention is applied.
- the present invention provides a method for generating an unequal intra prediction mode.
- One embodiment of the present invention adds a new prediction direction to the intra prediction mode, and the newly added prediction direction may be generated unevenly.
- an embodiment of the present invention selects eight or more arbitrary angles based on 1/32 accuracy, and at this time, selects angles unevenly to increase the prediction accuracy.
- images have strong vertical and horizontal characteristics, so they are closely selected in the vertical and horizontal vicinity, and are rarely selected in the vertical and horizontal vicinity.
- Fig. 34 (a) shows the selection of eight angles (0, 2, 5, 9, 13, 17, 21, 26, 32) based on 1/32 accuracy
- Fig. 34 (b) shows 1/32 accuracy. 16 angles are selected unevenly based on.
- the angles near 0, which are vertical and horizontal directions, are densely selected, and are rarely selected as they move away from the vertical and horizontal directions.
- various precisions such as 1/64 precision or 1/128 precision may be used for angle selection.
- a total of 67 prediction modes are used in intra prediction encoding.
- a large amount of directionality is applied to a small PU block such as a 4x4 block, a large amount of bits are wasted in encoding mode information, thereby reducing encoding performance.
- the present invention proposes a method using 35 directionality in the 4x4 PU block and 67 directional extended in the remaining PU blocks. That is, 5 bits are used to encode the prediction mode in the 4x4 PU block, and 6 bits are used to encode the prediction mode in the other PU blocks.
- whether to use some prediction modes in intra prediction encoding may be variably determined according to the PU block size.
- the embodiments described herein may be implemented and performed on a processor, microprocessor, controller, or chip.
- the functional units illustrated in FIGS. 1, 2, 10, and 11 may be implemented by a computer, a processor, a microprocessor, a controller, or a chip.
- the decoder and encoder to which the present invention is applied include a multimedia broadcasting transmitting and receiving device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video chat device, a real time communication device such as video communication, a mobile streaming device, Storage media, camcorders, video on demand (VoD) service providing devices, internet streaming service providing devices, three-dimensional (3D) video devices, video telephony video devices, and medical video devices Can be used for
- the processing method to which the present invention is applied can be produced in the form of a program executed by a computer, and can be stored in a computer-readable recording medium.
- Multimedia data having a data structure according to the present invention can also be stored in a computer-readable recording medium.
- the computer readable recording medium includes all kinds of storage devices for storing computer readable data.
- the computer-readable recording medium may include, for example, a Blu-ray disc (BD), a universal serial bus (USB), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. Can be.
- the computer-readable recording medium also includes media embodied in the form of a carrier wave (eg, transmission over the Internet).
- the bit stream generated by the encoding method may be stored in a computer-readable recording medium or transmitted through a wired or wireless communication network.
Abstract
Description
인트라 예측 모드(Intra prediction mode) | 관련 명칭(Associated name) |
0 | 인트라 플래너(INTRA_PLANAR) |
1 | 인트라 DC(INTRA_DC) |
2...34 | 인트라 방향성 2 ... 인트라 방향성 34(INTRA_ANGULAR2 ... INTRA_ANGULAR34) |
(i) | 현재 변환 블록의 크기(log2TrafoSize)가 2인 경우 |
(ii) | 현재 변환 블록의 크기(log2TrafoSize)가 3이고 cIdx가 0인 경우 |
(iii) | 현재 변환 블록의 크기(log2TrafoSize)가 3이고 ChromaArrayType 이 3인 경우 |
absIntraPredAngle | 0 | 2 | 5 | 9 | 13 | 17 | 21 | 26 | 32 |
flipIntraPredAngle | 0 | 6 | 11 | 15 | 19 | 23 | 27 | 30 | 32 |
iIdx | 0 | 1 | 2 | 3 |
startValue | 32 | 0 | -32 | 0 |
iIdx | 0 | 1 | 2 | 3 |
signtValue | 1 | -1 | -1 | 1 |
Claims (15)
- 비디오 신호를 디코딩하는 방법에 있어서,상기 비디오 신호로부터 인트라 예측시 각도 간격(angle interval)의 플립(flip)을 수행하는지 여부를 나타내는 플립 플래그를 획득하는 단계;상기 플립 플래그에 따라 인트라 예측시 각도 간격의 플립(flip)을 수행하는 경우, 인트라 예측 모드에 따라 플립 각도 변수를 유도하는 단계; 및상기 플립 각도 변수에 기초하여 인트라 예측 샘플을 생성하는 단계를 포함하되,상기 각도 간격(angle interval)은 예측 방향을 나타내는 각도 파라미터(angle parameter) 간의 간격을 나타내는 것을 특징으로 하는 방법.
- 제1항에 있어서,상기 플립 각도 변수는 각도 파라미터에 대응되며, 상기 각도 파라미터는 상기 인트라 예측 모드에 따라 설정되는 값을 나타내는 것을 특징으로 하는 방법.
- 제1항에 있어서,상기 플립 플래그는 특정 영역 단위로 설정되고, 상기 특정 영역 단위는 수평/수직 영역을 나타내거나 45도 영역을 나타내는 것을 특징으로 하는 방법.
- 제1항에 있어서,상기 플립 플래그는 시퀀스 파라미터 셋, 픽쳐 파라미터 셋, 슬라이스, 블록, 코딩 유닛 또는 예측 유닛 중 적어도 하나로부터 획득되는 것을 특징으로 하는 방법.
- 비디오 신호를 디코딩하는 방법에 있어서,상기 비디오 신호가 인트라 예측 방향을 나타내는 예측 각도 정보를 포함하고 있는지 여부를 나타내는 각도 전송 플래그를 획득하는 단계;상기 각도 전송 플래그에 따라 상기 비디오 신호가 예측 각도 정보를 포함하고 있는 경우, 예측 각도 정보를 획득하는 단계;상기 예측 각도 정보에 기초하여 각도 파라미터를 유도하는 단계; 및상기 각도 파라미터에 기초하여 인트라 예측 샘플을 생성하는 단계를 포함하되,상기 예측 각도 정보는 각도 간격(angle interval) 또는 각도 파라미터(angle parameter) 중 적어도 하나를 포함하고,상기 각도 간격은 예측 방향을 나타내는 각도 파라미터(angle parameter) 간의 간격을 나타내는 것을 특징으로 하는 방법.
- 제5항에 있어서,상기 각도 전송 플래그는 특정 영역 단위로 설정되고, 상기 특정 영역 단위는 수평/수직 영역을 나타내거나 45도 영역을 나타내는 것을 특징으로 하는 방법.
- 제6항에 있어서,상기 각도 전송 플래그가 수평/수직 영역 단위로 설정된 경우, 상기 각도 전송 플래그는 수평 영역 및 수직 영역에 대해 모두 획득되고,상기 예측 각도 정보는 상기 각도 전송 플래그에 기초하여 상기 수평 영역 및 수직 영역 중 적어도 하나에 대해 획득되는 것을 특징으로 하는 방법.
- 제5항에 있어서,상기 각도 전송 플래그는 시퀀스 파라미터 셋, 픽쳐 파라미터 셋, 슬라이스, 블록, 코딩 유닛 또는 예측 유닛 중 적어도 하나로부터 획득되는 것을 특징으로 하는 방법.
- 제5항에 있어서,상기 예측 각도 정보는 상기 각도 간격(angle interval) 또는 상기 각도 파라미터(angle parameter)에 대해 플립이 수행된 값인 것을 특징으로 하는 방법.
- 비디오 신호를 디코딩하는 장치에 있어서,상기 비디오 신호로부터 인트라 예측시 각도 간격(angle interval)의 플립(flip)을 수행하는지 여부를 나타내는 플립 플래그를 획득하는 파싱부; 및상기 플립 플래그에 따라 인트라 예측시 각도 간격의 플립(flip)을 수행하는 경우, 인트라 예측 모드에 따라 플립 각도 변수를 유도하고, 상기 플립 각도 변수에 기초하여 인트라 예측 샘플을 생성하는 인트라 예측부를 포함하되,상기 각도 간격(angle interval)은 예측 방향을 나타내는 각도 파라미터(angle parameter) 간의 간격을 나타내는 것을 특징으로 하는 장치.
- 제10항에 있어서,상기 플립 각도 변수는 각도 파라미터에 대응되며, 상기 각도 파라미터는 상기 인트라 예측 모드에 따라 설정되는 값을 나타내는 것을 특징으로 하는 장치.
- 제10항에 있어서,상기 플립 플래그는 특정 영역 단위로 설정되고, 상기 특정 영역 단위는 수평/수직 영역을 나타내거나 45도 영역을 나타내는 것을 특징으로 하는 장치.
- 비디오 신호를 디코딩하는 장치에 있어서,상기 비디오 신호가 인트라 예측 방향을 나타내는 예측 각도 정보를 포함하고 있는지 여부를 나타내는 각도 전송 플래그를 획득하는 파싱부;상기 각도 전송 플래그에 따라 상기 비디오 신호가 예측 각도 정보를 포함하고 있는 경우, 예측 각도 정보를 획득하고, 상기 예측 각도 정보에 기초하여 각도 파라미터를 유도하고, 상기 각도 파라미터에 기초하여 인트라 예측 샘플을 생성하는 인트라 예측부를 포함하되,상기 예측 각도 정보는 각도 간격(angle interval) 또는 각도 파라미터(angle parameter) 중 적어도 하나를 포함하고,상기 각도 간격은 예측 방향을 나타내는 각도 파라미터(angle parameter) 간의 간격을 나타내는 것을 특징으로 하는 장치.
- 제13항에 있어서,상기 각도 전송 플래그는 특정 영역 단위로 설정되고, 상기 특정 영역 단위는 수평/수직 영역을 나타내거나 45도 영역을 나타내는 것을 특징으로 하는 장치.
- 제14항에 있어서,상기 각도 전송 플래그가 수평/수직 영역 단위로 설정된 경우, 상기 각도 전송 플래그는 수평 영역 및 수직 영역에 대해 모두 획득되고,상기 예측 각도 정보는 상기 각도 전송 플래그에 기초하여 상기 수평 영역 및 수직 영역 중 적어도 하나에 대해 획득되는 것을 특징으로 하는 장치.
Priority Applications (2)
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US15/562,304 US20180255304A1 (en) | 2015-03-29 | 2016-03-29 | Method and device for encoding/decoding video signal |
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WO2019081926A1 (en) * | 2017-10-27 | 2019-05-02 | Sony Corporation | CODING AND DECODING IMAGE DATA |
CN112236997A (zh) * | 2018-07-16 | 2021-01-15 | 腾讯美国有限责任公司 | 视频压缩中帧内预测的参考样本填充和过滤 |
CN114245115A (zh) * | 2018-12-30 | 2022-03-25 | 北京达佳互联信息技术有限公司 | 用于对视频进行编码的方法和装置 |
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US10841593B2 (en) | 2015-06-18 | 2020-11-17 | Qualcomm Incorporated | Intra prediction and intra mode coding |
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KR102028015B1 (ko) | 2016-05-02 | 2019-10-02 | 한양대학교 산학협력단 | 화면 내 예측을 이용한 영상 부호화/복호화 방법 및 장치 |
KR20230070062A (ko) * | 2016-10-04 | 2023-05-19 | 주식회사 비원영상기술연구소 | 영상 데이터 부호화/복호화 방법 및 장치 |
US11277644B2 (en) | 2018-07-02 | 2022-03-15 | Qualcomm Incorporated | Combining mode dependent intra smoothing (MDIS) with intra interpolation filter switching |
US10469845B1 (en) * | 2018-09-21 | 2019-11-05 | Tencent America, Llc | Method and apparatus for intra mode coding |
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US11438583B2 (en) * | 2018-11-27 | 2022-09-06 | Tencent America LLC | Reference sample filter selection in intra prediction |
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