KR20230037527A - Method and apparatus for scalable video coding using intra prediction mode - Google Patents

Abstract

The present invention relates to a scalable video coding method and apparatus using an intra prediction mode. A decoding method includes the steps of: allowing a maximum probability mode set for predicting an intra prediction mode for a decoding target block in an enhancement layer to include an intra prediction mode for a corresponding block in a reference layer; and restoring the decoding target block of the enhancement layer using one of intra prediction modes included in the maximum probability mode set. Therefore, encoding/decoding efficiency can be improved.

Description

Intra prediction mode scalable coding method and apparatus {METHOD AND APPARATUS FOR SCALABLE VIDEO CODING USING INTRA PREDICTION MODE}

The present invention relates to image processing technology, and more particularly, to a scalable video coding method and apparatus for encoding/decoding an image.

Recently, as broadcasting services with HD (High Definition) resolution (1280x720 or 1920x1080) are expanding not only domestically but also globally, many users are getting used to high-resolution and high-definition images, and many organizations are spurring the development of next-generation video equipment. is applying In addition, as interest in UHD (Ultra High Definition), which has a resolution four times higher than that of HDTV, has increased along with HDTV, video standardization organizations have recognized the need for compression technology for higher resolution and higher quality images. In addition, through higher compression efficiency than H.264/AVC (Advanced Video Coding), a video compression coding standard currently used for HDTVs and mobile phones, it provides the same picture quality as the existing coding method, while providing many gains in terms of frequency band and storage. A new standard that can provide is required. Currently, Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) are jointly working on standardization for High Efficiency Video Coding (HEVC), a next-generation video codec. The general goal of HEVC is to encode video, including UHD video, with twice the compression efficiency compared to H.264/AVC. HEVC can provide not only HD and UHD video, but also high-definition video at a lower frequency than the present in 3D broadcasting and mobile communication networks.

In HEVC, a predicted image may be generated by spatially or temporally predicting an image, and a difference between an original image and a predicted image may be encoded. Efficiency of image encoding can be increased by such predictive encoding.

An object of the present invention is to provide a scalable video coding method and apparatus capable of improving coding/decoding efficiency.

In order to solve the above problem, a scalable video decoding method according to an embodiment of the present invention uses a maximum probability mode set for predicting an intra prediction mode for a decoding target block of an enhancement layer. configuring to include an intra prediction mode for a corresponding block of a reference layer; and restoring the decoding target block of the enhancement layer using one of intra prediction modes included in the maximum probability mode set.

A scalable video decoding apparatus according to an embodiment of the present invention is configured such that a maximum probability mode set for predicting an intra prediction mode for a decoding target block of an enhancement layer includes an intra prediction mode for a corresponding block of a reference layer. a mode set construction unit that does; and a mode selector selecting one of the intra prediction modes included in the maximum probability mode set as an intra prediction mode for a decoding object block of the enhancement layer.

According to an embodiment of the present invention, the maximum probability mode set for predicting the intra prediction mode of the enhancement layer is configured to include the intra prediction mode for the corresponding block of the reference layer, thereby reducing the number of bits required for encoding and decoding. Thus, coding efficiency can be increased, and thus, more improved picture quality can be provided at the same bit rate.

In addition, according to another embodiment of the present invention, pixel values of a block corresponding to the reference layer are corrected using a correlation parameter obtained according to neighboring pixel values reconstructed in the enhancement layer and the reference layer, thereby determining the target block for decoding of the enhancement layer. By using it as a prediction signal, coding efficiency can be improved.

1 is a block diagram showing a configuration according to an embodiment of an image encoding apparatus to which the present invention is applied.
2 is a block diagram showing a configuration according to an embodiment of a video decoding apparatus to which the present invention is applied.
3 is a conceptual diagram illustrating intra prediction modes used in an embodiment of the present invention.
4 is a conceptual diagram schematically illustrating an embodiment of a scalable video coding structure based on multiple layers.
FIG. 5 is a block diagram illustrating a first embodiment of a configuration of an intra prediction unit shown in FIG. 2 .
6 is a flowchart illustrating a scalable video coding method according to the first embodiment of the present invention.
7 is a diagram for explaining a first embodiment of an inter-layer intra prediction method.
8 is a table showing an embodiment of the number of selectable intra prediction modes according to the block size.
9 is a flowchart illustrating a scalable video coding method according to a second embodiment of the present invention.
10 is a flowchart illustrating a scalable video coding method according to a third embodiment of the present invention.
FIG. 11 is a block diagram illustrating a second embodiment of the configuration of an intra prediction unit shown in FIG. 2 .
12 is a flowchart illustrating a scalable video coding method according to a fourth embodiment of the present invention.
13 is a diagram for explaining a second embodiment of an inter-layer intra prediction method.
14 is a table showing an embodiment of intra prediction modes additionally selectable in the enhancement layer according to block sizes of the enhancement layer and the reference layer.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to drawings. In describing the embodiments of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the detailed description thereof will be omitted.

It is understood that when a component is referred to as being "connected" or "connected" to another component, it may be directly connected or connected to the other component, but other components may exist in the middle. It should be. In addition, the description of "including" a specific configuration in the present invention does not exclude configurations other than the corresponding configuration, and means that additional configurations may be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention.

In addition, the components appearing in the embodiments of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is made of separate hardware or a single software component unit. That is, each component is listed and included as each component for convenience of explanation, and at least two components of each component can be combined to form a single component, or one component can be divided into a plurality of components to perform a function, and each of these components can be divided into a plurality of components. Integrated embodiments and separated embodiments of components are also included in the scope of the present invention as long as they do not depart from the essence of the present invention.

In addition, some of the components may be optional components for improving performance rather than essential components that perform essential functions in the present invention. The present invention can be implemented by including only components essential to implement the essence of the present invention, excluding components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement. Also included in the scope of the present invention.

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

Referring to FIG. 1 , the video encoding apparatus 100 includes a motion estimation unit 111, a motion compensation unit 112, an intra prediction unit 120, a switch 115, a subtractor 125, and a transform unit 130. , a quantization unit 140, an entropy encoding unit 150, an inverse quantization unit 160, an inverse transform unit 170, an adder 175, a filter unit 180, and a reference image buffer 190.

The image encoding apparatus 100 encodes an input image in an intra mode or an inter mode and outputs a bitstream. Intra prediction means prediction within a picture, and inter prediction means prediction between pictures. In the intra mode, the switch 115 is switched to intra, and in the inter mode, the switch 115 is switched to inter. After generating a prediction block for an input block of an input image, the image encoding apparatus 100 encodes a difference between the input block and the prediction block.

In the case of the intra mode, the intra prediction unit 120 generates a prediction block by performing spatial prediction using pixel values of previously encoded blocks adjacent to the current block.

In the case of the inter mode, the motion estimation unit 111 finds a region that best matches the input block in the reference image stored in the reference image buffer 190 in the motion estimation process and obtains a motion vector. The motion compensation unit 112 generates a prediction block by performing motion compensation using a motion vector.

The subtractor 125 generates a residual block by the difference between the input block and the generated prediction block. The transform unit 130 performs transform on the residual block and outputs a transform coefficient. The quantization unit 140 quantizes the input transform coefficient according to a quantization parameter and outputs a quantized coefficient. The entropy encoding unit 150 entropy-codes the input quantized coefficients according to a probability distribution and outputs a bit stream.

Since HEVC performs inter-prediction encoding, that is, inter-prediction encoding, a currently encoded image needs to be decoded and stored in order to be used as a reference image. Therefore, the quantized coefficient is inversely quantized in the inverse quantization unit 160 and inversely transformed in the inverse transformation unit 170. The inverse quantized and inverse transformed coefficients are added to the prediction block through an adder 175, and a reconstructed block is generated.

The reconstructed block passes through a filter unit 180, and the filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstructed block or the reconstructed picture. can do. The filter unit 180 may also be called an adaptive in-loop filter. The deblocking filter may remove block distortion generated at a boundary between blocks. SAO may add an appropriate offset value to a pixel value to compensate for a coding error. ALF may perform filtering based on a value obtained by comparing a reconstructed image with an original image, and may be performed only when high efficiency is applied. A reconstructed block that has passed through the filter unit 180 is stored in the reference image buffer 190 .

2 is a block diagram showing a configuration according to an embodiment of a video decoding apparatus to which the present invention is applied.

Referring to FIG. 2 , the image decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, a motion compensation unit 250, and a filter unit. 260 and a reference image buffer 270.

The image decoding apparatus 200 receives the bitstream output from the encoder, performs decoding in an intra mode or inter mode, and outputs a reconstructed image, that is, a reconstructed image. In the intra mode, the switch is converted to intra, and in the case of inter mode, the switch is converted to inter. The image decoding apparatus 200 obtains a residual block from the input bitstream, generates a prediction block, and then adds the residual block and the prediction block to generate a reconstructed block, that is, a reconstructed block.

The entropy decoding unit 210 entropy-decodes the input bitstream according to a probability distribution and outputs a quantized coefficient. The quantized coefficients are inversely quantized in the inverse quantization unit 220 and inversely transformed in the inverse transform unit 230, and as a result of the inverse quantization/inverse transformation of the quantized coefficients, a residual block is generated.

In the intra mode, the intra predictor 240 generates a prediction block by performing spatial prediction using pixel values of previously encoded blocks adjacent to the current block.

In the case of the inter mode, the motion compensation unit 250 generates a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference image buffer 270 .

The residual block and the prediction block are added through the adder 255, and the added block passes through the filter unit 260. The filter unit 260 may apply at least one of a deblocking filter, SAO, and ALF to a reconstructed block or a reconstructed picture. The filter unit 260 outputs a reconstructed image, that is, a restored image. The reconstructed image may be stored in the reference image buffer 270 and used for inter prediction.

* Methods for improving the prediction performance of the encoding/decoding device include a method of increasing the accuracy of an interpolation image and a method of predicting a difference signal. Here, the difference signal is a signal indicating a difference between the original image and the predicted image. In the present invention, "difference signal" may be replaced with "difference signal", "residual block" or "difference block" depending on the context, and those skilled in the art may affect the spirit and essence of the invention. You will be able to distinguish them within the range not given.

Even if the accuracy of the interpolation image is increased, a difference signal is inevitable. Therefore, it is necessary to improve the encoding performance by reducing the difference signal to be encoded as much as possible by improving the performance of prediction of the difference signal.

A filtering method using a fixed filter coefficient may be used as a difference signal prediction method. However, this filtering method has limitations in prediction performance because filter coefficients cannot be used adaptively according to image characteristics. Therefore, it is necessary to improve prediction accuracy by performing filtering according to the characteristics of each prediction block.

Meanwhile, the encoding object block is a set of spatially connected pixels in the current encoding object image. The encoding target block is a unit in which encoding and decoding is performed, and may have a rectangular shape or an arbitrary shape. The neighboring reconstruction block is a block that has been encoded and decoded before the current encoding target block is encoded in the current encoding target image.

The predicted image is an image in which prediction blocks used for encoding each block from the first encoding target block of the image to the current encoding target block are collected in the current encoding target image. Here, the prediction block refers to a block having a prediction signal used for encoding each encoding target block in the current encoding target image. That is, a prediction block refers to each block in a prediction image.

A neighboring block means a neighboring reconstruction block of a current encoding target block and a neighboring prediction block that is a prediction block of each neighboring reconstruction block. That is, a neighboring block refers to both a neighboring reconstruction block and a neighboring prediction block.

The prediction block of the current encoding object block may be a prediction block generated by the motion compensation unit 112 or the intra prediction unit 120 according to the embodiment of FIG. 1 . In this case, after the prediction block filtering process is performed on the prediction block generated by the motion compensation unit 112 or the intra prediction unit 120, the subtractor 125 performs the difference between the filtered final prediction block and the original block. can

The neighboring block may be a block stored in the reference image buffer 190 in the embodiment of FIG. 1 or a separate memory. In addition, a neighboring reconstruction block or a neighboring prediction block generated in an image encoding process may be used as a neighboring block.

3 is a conceptual diagram illustrating intra prediction modes used in an embodiment of the present invention.

Referring to FIG. 3 , a different number of selectable intra prediction modes may exist according to a block size of a coding unit (CU).

That is, by using different numbers of intra prediction modes according to the size of the coding unit (CU), efficient intra prediction can be performed by determining an intra prediction direction according to the size of a block to be encoded (or decoded).

For example, in the case of H.264/AVC, there are 9 selectable intra prediction modes for a 4x4 luma block and 4 selectable intra prediction modes for a 16x16 luma block and chrominance component.

Meanwhile, in the case of HEVC, there may be 18 selectable intra prediction modes for a 4x4 luma block, 35 for an 8x8/16x16/32x32 luma block, and 4 selectable intra prediction modes for a 64x64 luma block.

Each of the 35 selectable intra prediction modes may have direction and mode values as shown in FIG. 3, and some of the 35 intra prediction modes shown in FIG. 3 are selected for a 4x4 luma block and a 64x64 luma block. It could be possible.

The encoding apparatus 100 selects a prediction mode that minimizes a difference between a prediction block and an encoding target block among selectable intra prediction modes according to the block size of the coding unit (CU), and decodes the selected intra prediction mode. In order to notify 200, an intra prediction mode signal may be signaled.

In addition, since the intra prediction modes of the encoding object block and its neighboring blocks may be correlated with each other, the intra prediction mode of the encoding object block is set to the intra prediction modes of the neighboring blocks (eg, the left block and the upper block). It can be predicted and signaled to the decoding device.

4 is a conceptual diagram schematically illustrating an embodiment of a scalable video coding structure using multiple layers to which the present invention can be applied. In FIG. 4, a group of pictures (GOP) represents a picture group, that is, a group of pictures.

In order to transmit image data, a transmission medium is required, and its performance varies depending on the transmission medium according to various network environments. A scalable video coding method may be provided for application to such various transmission media or network environments.

A scalable video coding method is a coding method that improves encoding/decoding performance by removing redundancy between layers by utilizing texture information, motion information, residual signals, etc. between layers. The scalable video coding method can provide various scalability in terms of space, time, and quality according to surrounding conditions such as transmission bit rate, transmission error rate, and system resources.

Scalable video coding may be performed using a multiple layer structure to provide a bitstream applicable to various network conditions. For example, the scalable video coding structure may include a base layer that compresses and processes image data using a general image encoding method, and compresses the image data using both encoding information of the base layer and a general image encoding method. An enhancement layer for processing may be included.

Here, the layer is a set of images and bitstreams classified on the basis of space (eg, video size), time (eg, encoding order, video output order), quality, complexity, and the like. it means. Also, a plurality of layers may have dependencies on each other.

Referring to FIG. 4, for example, a base layer may be defined as a Quarter Common Intermediate Format (QCIF), a frame rate of 15 Hz, and a bit rate of 3 Mbps, and a first enhanced layer may be defined as a Common Intermediate Format (CIF). Format), a frame rate of 30 Hz, and a bit rate of 0.7 Mbps, and the second enhancement layer may be defined as Standard Definition (SD), a frame rate of 60 Hz, and a bit rate of 0.19 Mbps. The format, frame rate, bit rate, etc. are one embodiment and may be determined differently as needed. Also, the number of layers used is not limited to the present embodiment and may be determined differently according to circumstances.

At this time, if a CIF 0.5 Mbps bit stream is required, the bit stream may be cut and transmitted so that the bit rate becomes 0.5 Mbps in the first enhancement layer. The scalable video coding method can provide temporal, spatial, and quality scalability by the method described above in the embodiment of FIG. 3 .

Hereinafter, target layer, target image, target slice, target unit, target block, target symbol, and target bin refer to a layer, image, slice, unit, block, symbol, and bin currently encoded or decoded, respectively. Thus, for example, the target layer may be a layer to which the target symbol belongs. In addition, the other layer is a layer other than the target layer, and means a layer available in the target layer. That is, other layers may be used to perform decoding in the target layer. Layers usable in the target layer may include, for example, temporal, spatial, and quality sublayers.

Corresponding layers, corresponding images, corresponding slices, corresponding units, corresponding blocks, corresponding symbols, and corresponding bins hereinafter refer to a layer corresponding to a target layer, a target image, a target slice, a target unit, a target block, a target symbol, and a target bin, respectively. It means image, slice, unit, block, symbol and bin. Corresponding video means an image of another layer existing on the same time axis as the target image. If the display order of an image in the target layer and an image in another layer are the same, it can be said that the image in the target layer and the image in the other layer exist on the same time axis. Whether images exist on the same time axis may be identified using an encoding parameter such as picture order count (POC). Corresponding slice means a slice existing in a corresponding position in the corresponding image, spatially identical to or similar to the target slice of the target image. The corresponding unit means a unit existing in a corresponding position in the corresponding image, spatially identical to or similar to the target unit of the target image. The corresponding block refers to a block existing in a corresponding position in the corresponding image, spatially identical to or similar to the target block of the target image.

In addition, hereinafter, a slice representing a unit in which an image is divided is used as a generic term for division units such as a tile and an entropy slice. Independent image encoding and decoding is possible between each divided unit.

Hereinafter, a block means a unit of video encoding and decoding. When encoding and decoding an image, the encoding or decoding unit refers to the divided unit when one image is divided into subdivided units and encoded or decoded. : Prediction Unit), Transform Unit (TU), Transform Block, and the like. One block may be further divided into smaller sub-blocks.

Considering the characteristics of scalable video coding as described above, inter-layer intra prediction, inter-layer inter prediction, or inter-layer differential signal prediction may be performed to remove redundancy between layers.

The inter-layer intra prediction is a method of enlarging a reconstructed pixel value of a reference layer to suit the resolution of an enhancement layer and then using it as a prediction signal, which will be described in detail below.

Hereinafter, a scalable video coding method according to an embodiment of the present invention will be described in detail with reference to FIGS. 5 to 10 . Meanwhile, a method of coding an enhancement layer as described with reference to FIG. 4 will be described below.

FIG. 5 is a block diagram briefly illustrating the configuration of a decoding apparatus according to an embodiment of the present invention, and shows a specific configuration of the intra prediction unit 240 shown in FIG. 2 .

Referring to FIG. 5 , the intra prediction mode adjusting unit 241 may adjust the intra prediction mode of a block of a reference layer corresponding to a block to be decoded of an enhancement layer.

The mode set configuration unit 242 may configure a maximum probability mode set to predict an intra prediction mode for a decoding target block of an enhancement layer.

The maximum probability mode set includes intra prediction modes that are highly likely to be used for the decoding target block of the enhancement layer, and may include, for example, two intra prediction modes with the highest probability.

According to an embodiment of the present invention, when a block of a reference layer corresponding to a block to be decoded of an enhancement layer has an intra prediction mode, the intra prediction mode adjusting unit 241 converts the corresponding intra prediction mode to that of the intra prediction mode of the enhancement layer. It can be adjusted according to the number and block size.

For example, when the intra prediction mode of a block of the reference layer corresponding to the decoding object block of the enhancement layer is greater than the number of intra prediction modes of the decoding object block of the enhancement layer, the corresponding value is predicted for the intra prediction mode of the enhancement layer. The value is adjusted to a value smaller than the number of intra prediction modes of the enhancement layer so that it can be used as a value. Otherwise, the intra prediction mode value for the corresponding block of the reference layer is not changed.

According to an embodiment of the present invention, the mode set configuration unit 242 may configure the maximum probability mode set for the decoding target block of the enhancement layer to include an adjusted intra prediction mode for the corresponding block of the reference layer. there is.

For example, the reference layer may be a base layer.

Meanwhile, the mode selector 243 may select one of the intra prediction modes belonging to the maximum probability mode set configured as described above as a prediction value for the intra prediction mode of the decoding target block of the enhancement layer. That is, the intra prediction unit 240 that performs intra prediction on the enhancement layer can more effectively predict the intra prediction mode of the decoding target block of the enhancement layer by referring to the intra prediction mode of the corresponding block of the reference layer. let it be

The intra prediction unit 240 uses an intra prediction mode belonging to the maximum probability mode set configured as described above using the intra prediction mode bit signaled by the encoding apparatus 100, and uses the final intra prediction mode to be applied to the decoding target block of the enhancement layer. A prediction mode can be selected and a prediction signal can be generated through intra prediction.

This means that the intra prediction mode of the decoding target block of the enhancement layer is the intra prediction mode of the corresponding block of the reference layer according to the association between the corresponding blocks between the enhancement layer and the reference layer (eg, the base layer). because it is likely to coincide with As a result, encoding/decoding efficiency can be improved.

FIG. 6 is a flowchart illustrating a scalable video coding method according to the first embodiment of the present invention, and blocks showing the configuration of the decoding apparatus according to the embodiment shown in FIG. 5 for the video coding method shown in FIG. Let's help and explain.

Referring to FIG. 6 , an intra prediction mode adjusting unit 241 configured to adjust a mode of a reference layer in order to predict an intra prediction mode for a block to be decoded in an enhancement layer among the intra prediction unit 240 corresponds to a block corresponding to the reference layer. The intra prediction mode for is adjusted based on the context information of the enhancement layer (step S300).

The mode set configuration unit 242 infers the adjusted intra prediction mode for the corresponding block of the reference layer (step S310).

After that, the mode set configuration unit 242 configures a maximum probability mode set for predicting an intra prediction mode for a decoding object block of the enhancement layer to include an intra prediction mode for a corresponding block of the reference layer ( Step S320).

The mode selection unit 243 selects one of the intra prediction modes included in the configured maximum probability mode set according to the intra prediction mode signal signaled from the encoding apparatus 100 (step S320).

The intra prediction unit 240 generates an intra prediction mode of the enhancement layer using the intra prediction mode selected by the above steps and a flag related to intra prediction mode prediction, and uses the intra prediction mode to be decoded by the enhancement layer. Blocks can be restored.

Referring to FIG. 7 , the mode set configuration unit 242 selects an adjusted intra prediction mode for a corresponding block B2 of the base layer in order to predict the intra prediction mode of the decoding object block B1 of the enhancement layer. The maximum probability mode set can be reconstructed to include.

For example, the corresponding block B2 of the base layer is a block that best matches the decoding target block B1 of the enhancement layer among blocks existing in the base layer, or a block to be decoded of the enhancement layer. It may be a block (co-located block) having a position corresponding to the block B1.

Referring to FIG. 8 , when the size of the decoding target block of the enhancement layer is 64x64, the intra prediction mode adjusting unit 241 sets a value greater than 3 (= the number of intra prediction modes in the 64x64 block - 1) of the reference layer. If there is, adjust the corresponding intra mode in the range of 0 to 3.

As another example, when the size of the decoding target block of the enhancement layer is 4x4, and the intra mode of the reference layer has a value greater than 17 (= the number of intra prediction modes of the 4x4 block - 1), the corresponding intra mode is set to 0 to 18. adjusted to the range of

Hereinafter, with reference to FIG. 9, an embodiment of a method for constructing a maximum probability mode set in step S310 will be described in detail.

Referring to FIG. 9 , the mode set configuration unit 242 first checks whether two intra prediction modes referable to neighboring blocks of the enhancement layer exist (step S400).

For example, when different intra prediction modes are used for the left block and the upper block of the decoding target block of the enhancement layer, it can be determined that there are two referable intra prediction modes.

Alternatively, if either of the left block and the above block does not use intra prediction (eg, uses inter prediction), or the same intra prediction mode is used for the left block and the above block, It may be determined that two referable intra prediction modes do not exist.

When there are two referable intra prediction modes, the mode set construction unit 242 sets the maximum probability mode set as the minimum value among the intra prediction mode for the corresponding block of the reference layer and the two referable intra prediction modes. Configure (step S410).

If two referable intra prediction modes do not exist, the mode set configuration unit 242 checks whether at least one referable intra prediction mode exists in neighboring blocks of the enhancement layer (S420).

For example, if one of the left block and the upper block uses intra prediction, or the same intra prediction mode is used for the left block and the upper block, it is determined that there is one intra prediction mode that can be referred to. It can be.

In contrast, when neither the left block nor the upper block uses intra prediction, it may be determined that there is no intra prediction mode that can be referred to.

If there is one intra prediction mode that can be referenced, the mode set configuration unit 242 configures the maximum probability mode set to include the intra prediction mode of the neighboring block and the intra prediction mode of the corresponding block of the reference layer. (step S430).

Meanwhile, when there is no intra prediction mode available for reference, the mode set configuration unit 242 configures the maximum probability mode set to include the DC mode and the intra prediction mode for the corresponding block of the reference layer (S440). step).

In this case, the encoding apparatus 100 selects one intra prediction mode among the set of maximum probability modes configured as described above as the intra prediction mode for the decoding target block of the enhancement layer, and then transmits information on the selected intra prediction mode. It can be signaled with an intra prediction mode signal.

Hereinafter, referring to FIG. 10, an embodiment of a method of constructing the maximum probability mode set when the intra prediction mode of the reference layer is not used will be described in detail.

Referring to FIG. 10 , the mode set configuration unit 242 first checks whether two intra prediction modes available for reference exist in neighboring blocks of the enhancement layer (step S500).

If there are two referable intra prediction modes, the mode set construction unit 242 configures the maximum probability mode set with the minimum and maximum values of the two referable intra prediction modes (step S510).

If there are no two referenceable intra prediction modes, the mode set configuration unit 242 checks whether there is at least one referenceable intra prediction mode in neighboring blocks of the enhancement layer (step S520).

If there is one referable intra prediction mode, the mode set configuration unit 242 configures the maximum probability mode set to include the intra prediction mode of the neighboring block and a DC mode or a planar mode (step S530).

On the other hand, if there is no referenceable intra prediction mode, the mode set configuration unit 242 configures the maximum probability mode set to include the DC mode and the planar mode (step S540).

According to another embodiment of the present invention, the intra prediction unit 240 for reconstructing the decoding target block of the enhancement layer generates a prediction signal for the enhancement layer using pixel values reconstructed for a corresponding block of the reference layer. can do.

For example, before enlarging the reconstructed pixel values of the reference layer corresponding to the decoding object block to match the resolution of the enhancement layer, the intra predictor 240 determines the reconstructed pixel values around the corresponding block of the reference layer and Based on the context between the reconstructed neighboring pixel values of the enhancement layer, the corresponding reconstructed pixel values of the reference layer may be filtered and enhanced. Thereafter, a texture obtained by enlarging the pixel values of the filtered reference layer according to the resolution may be used as a prediction signal for the decoding target block of the enhancement layer.

Hereinafter, a scalable video coding method according to another embodiment of the present invention will be described in detail with reference to FIGS. 11 to 13.

FIG. 11 is a block diagram of a second embodiment of the configuration of the intra prediction unit shown in FIG. can include

Referring to FIG. 11, the context-based parameter calculation unit 245 is based on context information such as reconstructed neighboring pixel values of the decoding target block of the enhancement layer and reconstructed neighboring pixel values of the corresponding block of the reference layer. Correlation parameters (eg, α and β) between inter-layer reconstructed pixel values can be obtained with .

Meanwhile, the texture generator 246 may generate a prediction signal for the decoding object block of the enhancement layer by correcting the reconstructed pixel values of the corresponding block of the reference layer using the obtained correlation parameter.

FIG. 12 is a flowchart illustrating a scalable video coding method according to another embodiment of the present invention, and the shown video coding method is a flowchart showing the configuration of a decoding apparatus according to another embodiment of the present invention shown in FIG. It will be explained in conjunction with a block diagram.

Referring to FIG. 12 , the decoding apparatus 200 first checks whether a block of a reference layer corresponding to a block to be decoded of an enhancement layer is an intra block (step S600).

As a result of the check, if the corresponding block of the reference layer is not an intra block, the motion compensation unit 250 provided in the decoding apparatus 200 may perform inter prediction on the decoding target block of the enhancement layer.

Meanwhile, when the corresponding block of the reference layer is an intra block, the decoding apparatus 200 checks whether information of the reference layer is to be used to perform intra prediction on the decoding target block of the enhancement layer (step S620). ).

When the information of the reference layer is not used, the intra prediction unit 240 provided in the decoding apparatus 200 performs intra prediction on the decoding target block of the enhancement layer using only the information of the enhancement layer ( Step S630).

For example, in step S630, the intra prediction unit 240 generates a prediction block by performing spatial prediction using pixel values of an already encoded block around the current decoding target block of the enhancement layer according to a specific intra prediction mode. can be

Meanwhile, when using the information of the reference layer, the decoding apparatus 200 checks whether texture prediction is possible (step S640).

For example, when the reference layer is an inter-slice, pixel values are not reconstructed for a block corresponding to the reference layer, and accordingly, a prediction signal for a block to be decoded in the enhancement layer is generated using the reconstructed pixel values of the reference layer. It may not be possible to generate or predict a texture using a correlation parameter representing the context between reconstructed pixel values between layers.

If texture prediction is not possible, the intra prediction unit 240 reconstructs a maximum probability mode set by adding an intra prediction mode for the corresponding block of the reference layer (step S650), and is signaled from the encoding device 100 Intra prediction is performed by selecting one of the reconstructed maximum probability mode sets according to the intra prediction mode signal (step S660).

That is, the method described with reference to FIGS. 5 to 10 may be used as an intra prediction method when the texture prediction is not possible.

On the other hand, if texture prediction is possible, the context-based parameter calculation unit 245 provided in the intra prediction unit 240 obtains a correlation parameter using the reconstructed neighboring pixel values of the enhancement layer and the reference layer (step S670).

Then, the texture generator 246 corrects the restored pixel values of the corresponding block of the reference layer using the obtained correlation parameter (step S680).

Referring to the example shown in FIG. 13 , the context-based parameter calculator 245 based on context information such as reconstructed neighboring pixel values 711 of the reference layer and reconstructed neighboring pixel values 701 of the enhancement layer, A correlation between inter-reconstructed pixel values may be expressed as parameters (eg, α and β).

The texture generation unit 246 uses the parameters output from the context-based parameter calculation unit 245 and the reconstructed pixel values 710 for the corresponding block of the reference layer to match the resolution of the enhancement layer and inter-layer pixels. A texture 700 reflecting context similarity may be generated, and the generated texture 700 is used as a prediction signal for a decoding target block of the enhancement layer.

For example, the texture generator 246 may generate the texture 700 used as a prediction signal for the decoding target block of the enhancement layer using Equation 1 below.

In Equation 1, Pred _c [x,y] is the texture 700 predicted by the texture generator 246, α and β are parameter values obtained by the context-based parameter calculator 245, and Rec _L [x,y] is the reconstructed pixel values 710 of the corresponding block of the reference layer, and Rec _L '[x,y] is the reconstructed pixel values 710 of the corresponding block of the reference layer. These are values scaled according to the resolution difference between the layer and the reference layer.

According to another embodiment of the present invention, the intra prediction unit 240 for reconstructing the decoding target block of the enhancement layer may reuse the intra prediction mode of the corresponding block of the reference layer in the enhancement layer.

For example, the intra predictor 240 determines the corresponding block of the reference layer when the corresponding block of the reference layer corresponding to the decoding target block is an intra mode and the block to be decoded more refined mode of the enhancement layer is used. The intra mode may be additionally used in the intra mode selection process of the enhancement layer.

Hereinafter, a scalable video coding method according to another embodiment of the present invention will be described in detail with reference to FIG. 14 .

FIG. 14 illustrates an operation of the third embodiment of the configuration of the intra prediction unit shown in FIG. 2 .

Referring to FIG. 14, when the size of the decoding object block of the enhancement layer is 4x4 or 64x64 and the size of the decoding object block of the reference layer is any one of 8x8/16x32/32x32, the predetermined selectable intra prediction modes By adding an intra prediction mode for a corresponding block of the reference layer, the number of selectable intra prediction modes for the decoding target block of the enhancement layer may be increased by one.

Adding the intra prediction mode for the corresponding block of the reference layer to the predetermined selectable intra prediction modes as described above means that the number of selectable intra prediction modes for the decoding target block of the enhancement layer It may be performed when the number of intra prediction modes selectable for the corresponding block is smaller than the number.

In the above, the scalable video coding method and apparatus according to an embodiment of the present invention have been described with a focus on the video decoding method and apparatus, but the scalable video coding method according to an embodiment of the present invention is illustrated in FIGS. It can be implemented by performing a series of steps according to the decoding method as described with reference to FIG. 14 .

Specifically, a scalable video encoding method and apparatus according to an embodiment of the present invention performs intra prediction having the same configuration as the decoding method and apparatus described with reference to FIGS. An intra prediction mode may be selected, and a prediction signal may be generated according to the selected intra prediction mode.

In the foregoing embodiments, the methods are described on the basis of a flow chart as a series of steps or blocks, but the present invention is not limited to the order of steps, and some steps may occur in a different order or concurrently with other steps as described above. there is. In addition, those skilled in the art will understand that the steps shown in the flow chart are not exclusive, that other steps may be included, or that one or more steps of the flow chart may be deleted without affecting the scope of the present invention. You will understand.

The foregoing embodiment includes examples of various aspects. It is not possible to describe all possible combinations to represent the various aspects, but those skilled in the art will recognize that other combinations are possible. Accordingly, it is intended that the present invention cover all other substitutions, modifications and variations falling within the scope of the following claims.

Claims (3)

A method for decoding a scalable video signal based on inter-layer prediction using a video decoding apparatus,
Determining whether inter-layer prediction is performed for a current picture of an enhancement layer;
Filtering a reference picture of a reference layer to be used for the inter-layer prediction based on a resolution difference between the enhancement layer and the reference layer;
Obtaining a prediction block of a current block of the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block of the filtered reference picture, wherein the correlation parameter is a weight value determined by an alpha parameter and an offset determined by a beta parameter values, the correlation parameter is calculated based on the reference picture of the reference layer, and the prediction pixel value of the current block is obtained by multiplying the reconstructed pixel value of the reference block by the weight value and the offset value Characterized in that it is obtained by adding;
entropy decoding an input bitstream to generate quantized transform coefficients of the current block of the enhancement layer;
inverse quantizing the quantized transform coefficients to generate transform coefficients of the current block;
inverse transforming the transform coefficient to produce a residual block of the current block; and
and reconstructing the current block using the residual block and the prediction block. A method for encoding a scalable video signal based on inter-layer prediction using a video encoding apparatus,
Determining whether inter-layer prediction is performed for a current picture of an enhancement layer;
Filtering a reference picture of a reference layer to be used for the inter-layer prediction based on a resolution difference between the enhancement layer and the reference layer;
Obtaining a prediction block of a current block of the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block of the filtered reference picture, wherein the correlation parameter is a weight value determined by an alpha parameter and an offset determined by a beta parameter values, the correlation parameter is calculated based on the reference picture of the reference layer, and the prediction pixel value of the current block is obtained by multiplying the reconstructed pixel value of the reference block by the weight value and the offset value Characterized in that it is obtained by adding;
obtaining a residual block of the current block using the prediction block;
generating transform coefficients of the current block by transforming the residual block;
quantizing the transform coefficient to generate a quantized transform coefficient of the current block; and
and generating a bitstream by entropy encoding the quantized transform coefficient. In a computer-readable recording medium storing a bitstream decoded by a video decoding method,
The video decoding method,
Determining whether inter-layer prediction is performed for a current picture of an enhancement layer;
Filtering a reference picture of a reference layer to be used for the inter-layer prediction based on a resolution difference between the enhancement layer and the reference layer;
Obtaining a prediction block of a current block of the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block of the filtered reference picture, wherein the correlation parameter is a weight value determined by an alpha parameter and an offset determined by a beta parameter values, the correlation parameter is calculated based on the reference picture of the reference layer, and the predicted pixel value of the current block is a value obtained by multiplying a reconstructed pixel value of the reference block by the weight value and the offset value Characterized in that it is obtained by adding;
entropy decoding an input bitstream to generate quantized transform coefficients of the current block of the enhancement layer;
inverse quantizing the quantized transform coefficients to generate transform coefficients of the current block;
inverse transforming the transform coefficient to produce a residual block of the current block; and
and restoring the current block using the residual block and the prediction block.

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