KR20200128375A - Method and apparatus for scalable video coding using intra prediction mode - Google Patents

Abstract

The present invention relates to a scalable video coding method using an intra prediction mode and a device therefor. A decoding method comprises the following steps of: configuring a maximum probability mode set for predicting an intra prediction mode for a block to be decoded of an enhancement layer to include an intra prediction mode for a corresponding block of a reference layer; and restoring the block to be decoded of the enhancement layer by using any one of intra prediction modes included in the maximum probability mode set. Therefore, the 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) have been expanded not only in Korea but also around the world, many users are getting used to high-definition and high-definition images, and accordingly, many organizations spur development of next-generation video devices Is putting. In addition, as interest in UHD (Ultra High Definition) having a resolution of 4 times or more than HDTV along with HDTV has increased, moving image standardization organizations have recognized the need for compression technology for higher resolution and high-definition images. In addition, through higher compression efficiency than H.264/AVC (Advanced Video Coding), which is a video compression coding standard currently used in HDTVs and mobile phones, it provides the same image quality as the existing coding method, while providing many gains in terms of frequency band and storage. New standards that can be provided are required. Currently, Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) are jointly working on standardization of HEVC (High Efficiency Video Coding), a next-generation video codec. The outline goal of HEVC is to encode a video including UHD video at twice the compression efficiency of H.264/AVC. HEVC can provide high-definition images at lower frequencies than the current in 3D broadcasting and mobile communication networks as well as HD and UHD images.

In HEVC, a prediction image may be generated by performing spatial or temporal prediction on an image, and a difference between the original image and the predicted image may be encoded. By such predictive encoding, the efficiency of image encoding may be increased.

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

A scalable video decoding method according to an embodiment of the present invention for solving the above problem includes a maximum probability mode set for predicting an intra prediction mode for a block to be decoded of an enhancement layer. Configuring to include an intra prediction mode for a corresponding block of a reference layer; And restoring a decoding target block of the enhancement layer by 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 to include a maximum probability mode set for predicting an intra prediction mode for a block to be decoded of an enhancement layer and an intra prediction mode for a corresponding block of the reference layer. A mode set configuration unit; And a mode selector for 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, a maximum probability mode set for predicting an intra prediction mode of an enhancement layer is configured to include an intra prediction mode for a corresponding block of a reference layer, thereby reducing the number of bits required for encoding and decoding. By doing so, coding efficiency can be improved, and accordingly, more improved picture quality at the same bit rate can be provided.

In addition, according to another embodiment of the present invention, pixel values of a corresponding block of a reference layer are corrected using a correlation parameter obtained according to values of neighboring pixels reconstructed from the enhancement layer and the reference 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 an image 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 multilayer-based scalable video coding structure.
5 is a block diagram showing a configuration of an intra prediction unit shown in FIG. 2 according to a first embodiment.
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 intra prediction modes selectable according to a 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.
11 is a block diagram illustrating a second embodiment of the configuration of the 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 describing a second embodiment of an inter-layer intra prediction method.
14 is a table showing an embodiment of an intra prediction mode additionally selectable in an enhancement layer according to block sizes of an enhancement layer and a reference layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In describing the embodiments of the present specification, when it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present specification, a detailed description thereof will be omitted.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it is directly connected to or may be connected to the other component, but other components may exist in the middle. 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 scope of the implementation of the present invention or the technical idea 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 used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is formed of separate hardware or a single software component. That is, each constituent part is listed and included as a respective constituent part for convenience of explanation, and at least two of the constituent parts are combined to form one constituent part, or one constituent part is divided into a plurality of constituent parts to perform a function Integrated embodiments and separate embodiments of the components are also included in the scope of the present invention unless departing from the essence of the present invention.

In addition, some of the components are not essential components that perform essential functions in the present invention, but may be optional components only for improving performance. The present invention can be implemented by including only the 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 image encoding apparatus 100 includes a motion prediction 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 intra prediction, and inter prediction means inter prediction. In the intra mode, the switch 115 is switched to intra, and in the inter mode, the switch 115 is switched to inter. The image encoding apparatus 100 generates a prediction block for an input block of an input image and then 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 an already coded block around the current block.

In the case of the inter mode, the motion prediction unit 111 finds a region in the reference image stored in the reference image buffer 190 that best matches the input block in the motion prediction 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 based on the difference between the input block and the generated prediction block. The transform unit 130 outputs a transform coefficient by performing transform on the residual block. In addition, the quantization unit 140 quantizes the input transform coefficient according to the quantization parameter and outputs a quantized coefficient. The entropy encoder 150 entropy-encodes the input quantized coefficient according to a probability distribution and outputs a bit stream.

Since HEVC performs inter prediction encoding, that is, inter prediction encoding, the currently encoded image needs to be decoded and stored in order to be used as a reference image. Accordingly, the quantized coefficients are inverse quantized by the inverse quantization unit 160 and inversely transformed by the inverse transform 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 restoration block passes through the 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 a restoration block or a reconstructed picture. can do. The filter unit 180 may also be referred to as an adaptive in-loop filter. The deblocking filter can remove block distortion occurring at the 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 the reconstructed image and the original image, and may be performed only when high efficiency is applied. The 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 an image 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 an inter mode, and outputs a reconstructed image, that is, a reconstructed image. In the intra mode, the switch is switched to intra, and in the inter mode, the switch is switched to inter. The image decoding apparatus 200 obtains a residual block from the received 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 inverse quantized in the inverse quantization unit 220 and inversely transformed in the inverse transform unit 230, and as a result of inverse quantization/inverse transformation of the quantized coefficients, a residual block is generated.

In the case of the intra mode, the intra prediction unit 240 generates a prediction block by performing spatial prediction using pixel values of an already coded block around the current block.

In 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 reconstructed 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 an 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 representing the 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 of ordinary skill in the art may influence the spirit and nature of the invention. You will be able to distinguish this within the scope not given.

Even if the accuracy of the interpolated image increases, a difference signal is inevitably generated. Therefore, it is necessary to improve the encoding performance by improving the performance of the difference signal prediction and reducing the difference signal to be encoded as much as possible.

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

Meanwhile, the encoding target block is a set of spatially connected pixels in the current encoding target image. The encoding target block is a unit in which encoding and decoding are performed, and may have a square or arbitrary shape. The neighboring reconstructed block is a block in which encoding and decoding are completed before the current encoding object block is encoded in the current encoding object image.

The predicted image is an image obtained by collecting prediction blocks used for encoding each block from the first encoding object block of the image to the current encoding object block in the current encoding object 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.

The neighboring block means a neighboring reconstructed block of a current encoding target block and a neighboring prediction block that is a prediction block of each neighboring reconstructed block. That is, the neighboring block refers to the neighboring restoration block and the neighboring prediction block together.

The prediction block of the current encoding target 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 a 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 a difference between the filtered final prediction block and the original block. I can.

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

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

Referring to FIG. 3, different numbers of selectable intra prediction modes may exist according to a block size of an encoding 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 coded (or decoded).

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

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

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

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

In addition, since the intra prediction mode 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 defined as the intra prediction modes of neighboring blocks (for example, a left block and an upper block). It can be predicted and signaled to the decoding device.

4 is a conceptual diagram schematically showing 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.

A transmission medium is required to transmit image data, and its performance varies for each 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.

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

Scalable video coding may be performed using a multiple layers structure so as to provide a bitstream applicable to various network situations. 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 image data using both encoding information of the base layer and a general image encoding method. It may include an enhancement layer to process.

Here, the layer is a set of images and bitstreams classified based on space (eg, image size), time (eg, encoding order, image output order), quality, complexity, etc. 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 enhancement layer is a Common Intermediate (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 a 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 differently determined as necessary. In addition, the number of layers to be used is not limited to this embodiment and may be determined differently according to circumstances.

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

Hereinafter, a target layer, a target image, a target slice, a target unit, a target block, a target symbol, and a target bin mean a currently encoded or decoded layer, image, slice, unit, block, symbol, and bin, respectively. Therefore, for example, the target layer may be a layer to which the target symbol belongs. In addition, the other layer is a layer excluding the target layer and refers to a layer available in the target layer. That is, another layer can be used to perform decoding in the target layer. Layers usable in the target layer may include temporal, spatial, and quality lower layers, for example.

In addition, hereinafter, the corresponding layer, the corresponding image, the corresponding slice, the corresponding unit, the corresponding block, the corresponding symbol, and the corresponding bin are respectively a target layer, a target image, a target slice, a target unit, a target block, a target symbol, a layer corresponding to the target bin, It means image, slice, unit, block, symbol and bin. The corresponding image means an image of another layer existing on the same time axis as the target image. If the display order of the image in the target layer and the image in the other layer is 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 or not images exist on the same time axis can be identified using an encoding parameter such as a picture order count (POC). The corresponding slice refers to a slice present in a corresponding position in the corresponding image, which is spatially identical or similar to the target slice of the target image. The corresponding unit refers to a unit present in the corresponding position in the corresponding image, which is spatially identical or similar to the target unit of the target image. The corresponding block refers to a block present in the corresponding image at a spatially identical or similar position to the target block of the target image.

In addition, hereinafter, a slice indicating a unit into which an image is divided is used as a general term for a division unit such as a tile and an entropy slice. Independent image encoding and decoding are possible between each divided unit.

In addition, hereinafter, a block means a unit of image encoding and decoding. When encoding and decoding an image, an encoding or decoding unit refers to a divided unit when one image is divided into subdivided units and encoded or decoded. Therefore, a macroblock, a coding unit (CU), and a prediction unit (PU) : Prediction Unit), transform unit (TU: Transform Unit), may be called a transform block (transform block). One block may be further divided into sub-blocks having smaller sizes.

In consideration of 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 inter-layer redundancy.

In the inter-layer intra prediction, a reconstructed pixel value of a reference layer is enlarged to suit the resolution of the enhancement layer and then used as a prediction signal, and a detailed description thereof 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 schematic block diagram of a configuration of a decoding apparatus according to an embodiment of the present invention, and illustrates a specific configuration of the intra prediction unit 240 illustrated in FIG. 2.

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

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

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

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 adjuster 241 changes the intra prediction mode to the intra prediction mode of the enhancement layer. It can be adjusted according to the number and block size.

For example, if the intra prediction mode of the block of the reference layer corresponding to the block to be decoded of the enhancement layer is greater than the number of intra prediction modes of the block to be decoded 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 be configured such that the maximum probability mode set for the decoding target block of the enhancement layer includes an adjusted intra prediction mode for a corresponding block of the reference layer. have.

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

Meanwhile, the mode selector 243 may select any one of intra prediction modes belonging to the maximum probability mode set configured as described above as a prediction value for an intra prediction mode for a 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 for the decoding target block of the enhancement layer by referring to the intra prediction mode for the corresponding block of the reference layer. To be.

The intra prediction unit 240 uses the intra prediction mode belonging to the maximum probability mode set configured as described above by using the intra prediction mode bits 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 may be selected and a prediction signal may be generated through intra prediction.

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

FIG. 6 is a flowchart illustrating a scalable video coding method according to a first embodiment of the present invention, and a block showing the configuration of a decoding apparatus according to an embodiment of the present invention illustrated in FIG. It will be explained in conjunction with the help.

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

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

Thereafter, the mode set construction unit 242 configures a maximum probability mode set for predicting an intra prediction mode for a block to be decoded of the enhancement layer to include an intra prediction mode for a corresponding block of the reference layer ( Step S320).

The mode selector 243 selects any one of the intra prediction modes included in the configured maximum probability mode set according to the intra prediction mode signal signaled by 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 steps as described above and the flag related to the intra prediction mode prediction, and uses this to generate the decoding target of the enhancement layer. Blocks can be restored.

Referring to FIG. 7, in order to predict an intra prediction mode for the decoding target block B1 of the enhancement layer, the mode set construction unit 242 configures an adjusted intra prediction mode for a corresponding block B2 of the base 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 decoding target of the enhancement layer It may be a 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 adjuster 241 sets a value greater than 3 (= number of intra prediction modes of 64x64 block-1) of the reference layer. If so, the intra mode is adjusted in the range of 0 to 3.

As another example, when the size of the decoding target block of the enhancement layer is 4x4, when 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 0 to 18 Adjust to the range of.

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

Referring to FIG. 9, the mode set construction unit 242 first checks whether there are two referenceable intra prediction modes in neighboring blocks of the enhancement layer (step S400).

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

On the contrary, when either one of the left block and the upper block does not use intra prediction (eg, uses inter prediction), or the same intra prediction mode is used for the left block and the upper block, It may be determined that there are no two referenceable intra prediction modes.

When there are two referenceable intra prediction modes, the mode set construction unit 242 determines 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 referenceable intra prediction modes. Configure (S410 step).

When there are no two referenceable intra prediction modes, the mode set configuration unit 242 checks whether there is any referenceable intra prediction mode in neighboring blocks of the enhancement layer (step S420).

For example, when either 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 referenceable intra prediction mode. Can be.

In contrast, when both the left block and the upper block do not use intra prediction, it may be determined that none of the referenceable intra prediction modes exist.

When there is one referenceable intra prediction mode, the mode set configuration unit 242 configures the maximum probability mode set to include an intra prediction mode of the neighboring block and an intra prediction mode of a corresponding block of the reference layer. (S430 step).

Meanwhile, when none of the referenceable intra prediction modes exist, the mode set configuration unit 242 configures the maximum probability mode set to include an intra prediction mode and a DC mode for a corresponding block of the reference layer (S440). step).

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

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

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

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

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

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

Meanwhile, when none of the referenceable intra prediction modes exist, the mode set construction unit 242 configures the maximum probability mode set to include a DC mode and a 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 by using the reconstructed pixel values for the corresponding block of the reference layer. can do.

For example, before expanding the reconstructed pixel values of the reference layer corresponding to the decoding target block according to the resolution of the enhancement layer, the intra prediction unit 240 may determine the reconstructed pixel values around the corresponding block of the reference layer and The reconstructed pixel values of the corresponding reference layer may be filtered and enhanced based on a context between reconstructed neighboring pixel values of the enhancement layer. Thereafter, a texture obtained by enlarging the filtered pixel value of the 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 showing a second embodiment of the configuration of the intra prediction unit shown in FIG. 2, and the illustrated intra prediction unit 240 includes a context-based parameter calculation unit 245 and a texture generation unit 246. Can include.

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

Meanwhile, the texture generator 246 may generate a prediction signal for a decoding target block of the enhancement layer by correcting reconstructed pixel values for a 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. The illustrated video coding method is shown in FIG. 11 and shows the configuration of a decoding apparatus according to another embodiment of the present invention. It will be described in conjunction with the 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 confirmation, 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 to use information of the reference layer to perform intra prediction on the decoding target block of the enhancement layer (step S620). ).

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

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

Meanwhile, when using the reference layer information, 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 restored for the corresponding block of the reference layer, and accordingly, a prediction signal for the decoding target block of the enhancement layer is used using the reconstructed pixel values of the reference layer It may not be possible to predict a texture using a correlation parameter indicating a context between generated or reconstructed pixel values between layers.

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

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

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

Thereafter, the texture generator 246 corrects reconstructed pixel values for 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 calculation unit 245 is based on context information such as reconstructed neighboring pixel values 711 of the reference layer and restored neighboring pixel values 701 of the enhancement layer. The correlation between the reconstructed pixel values may be expressed as parameters (eg, α, 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 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 a texture 700 used as a prediction signal for a decoding target block of the enhancement layer by using Equation 1 as follows.

In Equation 1, Pred _c [x,y] is the texture 700 predicted by the texture generating unit 246, α and β are parameter values obtained by the context-based parameter calculation unit 245, Rec _L [x,y] are reconstructed pixel values 710 for the corresponding block of the reference layer, Rec _L '[x,y] is the reconstructed pixel values 710 for 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, when a block corresponding to a reference layer corresponding to a block to be decoded is an intra mode and a more subdivided mode of a block to be decoded of the enhancement layer is used, the intra prediction unit 240 The intra mode can be additionally used in the process of selecting the intra mode 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.

14 shows the 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 are As an intra prediction mode for a corresponding block of the reference layer is added, the number of intra prediction modes selectable for a decoding object block of the enhancement layer may be increased by one.

As described above, adding an intra prediction mode for a corresponding block of the reference layer to predetermined selectable intra prediction modes includes the number of intra prediction modes selectable for a decoding target block of the enhancement layer of the reference layer. It may be performed when it is smaller than the number of selectable intra prediction modes for the corresponding block.

In the above, a scalable video coding method and apparatus according to an embodiment of the present invention have been described with a focus on a video decoding method and apparatus, but the scalable video coding method according to an embodiment of the present invention is illustrated in FIGS. 5 and 13. It may be implemented by performing a series of steps according to the decoding method described with reference to FIG. 14.

Specifically, the scalable video encoding method and apparatus according to an embodiment of the present invention performs intra prediction of the same configuration as the decoding method and apparatus described with reference to FIGS. 5 to 13 to determine the encoding target block of the enhancement layer. An intra prediction mode may be selected, and a prediction signal may be generated according to the selected intra prediction mode.

In the above-described embodiment, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with those described above. have. In addition, those of ordinary skill in the art understand that the steps shown in the flowchart are not exclusive, other steps are included, or one or more steps in the flowchart may be deleted without affecting the scope of the present invention. You can understand.

The above-described embodiments include examples of various aspects. Although not all possible combinations for representing the various aspects can be described, those of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the present invention will be said to cover all other replacements, modifications and changes falling within the scope of the following claims.

Claims (6)

In the video decoding method,
Determining whether inter-layer texture prediction is performed on a current picture included in an enhancement layer;
Scaling a reconstructed reference picture included in a reference layer used for inter-layer texture prediction based on a difference in resolution between the enhancement layer and the reference layer;
Obtaining a predicted pixel value of a current block included in the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block included in the scaled reference picture;
Decoding a bitstream for the current block to obtain a residual pixel value of the current block; And
Restoring the current block using a residual pixel value and a prediction pixel value of the current block,
The correlation parameter includes a first parameter and a second parameter,
The correlation parameter is calculated based on the reconstructed reference picture,
The predicted pixel value of the current block is obtained by multiplying the reconstructed pixel value of the reference block by the first parameter and adding the second parameter. The method of claim 1,
The reconstructed reference picture has the same POC (Picture Output Order) as the current picture, an image decoding method The method of claim 1,
The reference block is a co-located block of the current block in the scaled reference picture. The method of claim 1,
The reference picture has a lower spatial resolution than the current picture. In the video encoding method,
Determining whether inter-layer texture prediction is performed on a current picture included in an enhancement layer;
Scaling a reconstructed reference picture included in a reference layer used for inter-layer texture prediction based on a difference in resolution between the enhancement layer and the reference layer;
Obtaining a predicted pixel value of a current block included in the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block included in the scaled reference picture;
Obtaining a residual pixel value of the current block by using the predicted pixel value; And
Including the step of encoding information on the residual pixel value of the current block through a bitstream,
The correlation parameter includes a first parameter and a second parameter,
The correlation parameter is calculated based on the reconstructed reference picture,
The prediction pixel value of the current block is obtained by multiplying the reconstructed pixel value of the reference block by the first parameter and adding the second parameter. A computer-readable recording medium storing a bitstream input to an image decoding apparatus to restore an image,
Determining whether inter-layer texture prediction is performed on a current picture included in an enhancement layer;
Scaling a reconstructed reference picture included in a reference layer used for inter-layer texture prediction based on a difference in resolution between the enhancement layer and the reference layer;
Obtaining a predicted pixel value of a current block included in the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block included in the scaled reference picture;
Obtaining a residual pixel value of the current block by using the predicted pixel value; And
Encoding information on the residual pixel value of the current block through the bitstream,
The correlation parameter includes a first parameter and a second parameter,
The correlation parameter is calculated based on the reconstructed reference picture,
The predicted pixel value of the current block is obtained by adding the second parameter to a value obtained by multiplying the reconstructed pixel value of the reference block by the first parameter. Readable recording medium.

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