KR20210149673A - Method and apparatus for image encoding/decoding - Google Patents

Abstract

An image encoding/decoding method and device for supporting a plurality of layers are disclosed. The image decoding method for supporting the plurality of layers includes the steps of: decoding information of a first layer referenced by the picture of a second layer including a current decoding target block; mapping the information of the first layer to the picture size of the second layer; constructing a reference picture list for the picture of the second layer by adding the mapped information of the first layer; and generating prediction samples of the current decoding target block by performing prediction on the current decoding target block of the second layer based on the reference picture list.

Description

Image encoding/decoding method and apparatus

The present invention relates to image encoding and decoding, and more particularly, to a method of predicting, encoding and decoding an image of an upper layer using information of a lower layer when encoding and decoding an image having a multi-layer structure.

With the recent establishment of a multimedia environment, various terminals and networks are being used, and thus user needs are also diversifying.

For example, as the performance and computing capability of the terminal diversify, the supported performance also diversifies for each device. In addition, the network through which information is transmitted is also diversifying not only in the external structure like a wired/wireless network, but also in terms of functions such as the type of information to be transmitted, the amount of information and the speed. Users select terminals and networks to use according to desired functions, and the spectrum of terminals and networks provided by companies to users is also diversifying.

In this regard, as broadcasting having a high definition (HD) resolution has recently been expanded and serviced not only domestically but also worldwide, many users are getting used to high-resolution and high-definition images. Accordingly, many video service-related organizations are making great efforts to develop next-generation video devices.

Also, along with HDTV, as interest in Ultra High Definition (UHD) having a resolution four times higher than that of HDTV increases, the demand for a technology for compressing and processing images of higher resolution and higher quality is increasing.

In order to compress and process an image, an inter prediction technology that predicts pixel values included in the current picture from temporally previous and/or later pictures, other pixels included in the current picture by using pixel information in the current picture An intra prediction technique for predicting a value, an entropy encoding technique for allocating a short code to a symbol with a high frequency of occurrence, and an entropy encoding technique for assigning a long code to a symbol with a low frequency of occurrence may be used.

As described above, in consideration of each terminal and network having different supported functions, and diversified user needs, the quality, size, frame, etc. of supported images need to be diversified accordingly.

As described above, due to heterogeneous communication networks and various functions and types of terminals, scalability to support image quality, resolution, size, frame rate, etc. in various ways has become an important function of a video format.

Therefore, it is necessary to provide a scalability function to enable efficient video encoding and decoding in terms of time, space, image quality, etc. in order to provide services required by users in various environments based on a highly efficient video encoding method.

The present invention provides a method and apparatus for encoding/decoding an upper layer using information of a lower layer in scalable video coding.

The present invention provides a method and apparatus for mapping a lower layer image in scalable video coding.

The present invention provides a method and apparatus for constructing a reference picture list of a higher layer image by using a lower layer image in scalable video coding and performing prediction.

According to an embodiment of the present invention, an image decoding method supporting a plurality of layers is provided. The image decoding method includes decoding information of a first layer referenced by a picture of a second layer including a current decoding object block, and mapping the information of the first layer to the picture size of the second layer. step, constructing a reference picture list for the picture of the second layer by adding the mapped information of the first layer, and performing prediction on the current block to be decoded of the second layer based on the reference picture list and generating prediction samples of the current decoding object block.

The first layer information may include at least one of a sample value and motion information of the first layer picture.

According to another embodiment of the present invention, an image decoding apparatus supporting a plurality of layers is provided. The image decoding apparatus includes a decoder that decodes information of a first layer referenced by a picture of a second layer including a current decoding target block, and a picture size of the second layer. Mapping the information of the first layer and constructing a reference picture list for the picture of the second layer by adding the mapped information of the first layer, and performing prediction on the current block to be decoded of the second layer based on the reference picture list and a prediction unit generating prediction samples of the current decoding object block.

The first layer information may include at least one of a sample value and motion information of the first layer picture.

According to another embodiment of the present invention, an image encoding method supporting a plurality of layers is provided. The video encoding method may include decoding information of a first layer referenced by a picture of a second layer including a current encoding target block, and mapping the information of the first layer to the picture size of the second layer. step, constructing a reference picture list for the picture of the second layer by adding the mapped information of the first layer, and performing prediction on the current encoding object block of the second layer based on the reference picture list and generating prediction samples of the current encoding object block.

The first layer information may include at least one of a sample value and motion information of the first layer picture.

According to another embodiment of the present invention, an image encoding apparatus supporting a plurality of layers is provided. The image encoding apparatus maps the information of the first layer to the encoder for encoding information of the first layer referenced by the picture of the second layer including the current encoding target block and the picture size of the second layer. and constructing a reference picture list for the picture of the second layer by adding the mapped information of the first layer, and performing prediction on the current encoding target block of the second layer based on the reference picture list. and a prediction unit generating prediction samples of the current encoding object block.

The first layer information may include at least one of a sample value and motion information of the first layer picture.

In the prior art, in the process of mapping motion information of a lower layer, even when temporal motion vector prediction of an upper layer is not performed, there is a problem in that an unnecessary motion information mapping process is performed. In addition, when motion information mapping of the lower layer is not performed, since the decoded picture of the lower layer can be indicated as a collocated picture for the temporal motion vector in the upper layer, the temporal motion vector prediction of the upper layer is performed There is a problem in that encoding efficiency is lowered due to cases in which it cannot be done.

According to the present invention, encoding/decoding efficiency is improved by mapping motion information of a lower layer referenced by an upper layer to an image size of an upper layer and then predicting and restoring the upper layer using the mapped image signal of the lower layer. can be improved In addition, by modifying the upper-level syntax, it is possible to omit a mapping process for unnecessary lower-layer motion information and to reduce complexity. In addition, it is possible to prevent an erroneous corresponding picture from being used, thereby preventing a decrease in encoding efficiency.

1 is a block diagram illustrating a configuration of an image encoding apparatus to which the present invention is applied according to an embodiment.
2 is a block diagram illustrating a configuration of an image decoding apparatus to which the present invention is applied according to an embodiment.
3 is a conceptual diagram schematically illustrating an embodiment of a scalable video coding structure using a plurality of layers to which the present invention can be applied.
4 is a flowchart schematically illustrating a method of performing inter-layer prediction (inter-layer prediction) in scalable video coding according to an embodiment of the present invention.
5 and 6 are diagrams illustrating an inter-layer motion information mapping method according to an embodiment of the present invention.

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 corresponding description may be omitted.

In this specification, when a component is referred to as being “connected” or “connected” to another component, it may mean that it is directly connected or connected to the other component, or another component in the middle. It can also mean that the element is present. In addition, the description of “including” a specific configuration in the present specification does not exclude configurations other than the corresponding configuration, and it 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, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first configuration may be named as a second configuration, and similarly, a second configuration may also be called a first configuration.

In addition, the components shown in the embodiment 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 component is listed as each component for convenience of description, and at least two components among each component may form one component, or one component may be divided into a plurality of components to perform a function. Integrated embodiments and separate embodiments of each component are also included in the scope of the present invention without departing from the essence of the present invention.

In addition, some of the components are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention, except for 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 illustrating a configuration of an image encoding apparatus to which the present invention is applied according to an embodiment.

A scalable video encoding apparatus supporting a multi-layer structure may be implemented by extending a general image encoding apparatus having a single layer structure. The block diagram of FIG. 1 shows an embodiment of an image encoding apparatus that may be the basis of a scalable video encoding apparatus applicable to a multi-layer structure.

Referring to FIG. 1 , the image encoding apparatus 100 includes an inter prediction unit 110 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , a transform unit 130 , a quantization unit 140 , and entropy. It includes an encoder 150 , an inverse quantizer 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference picture buffer 190 .

The image encoding apparatus 100 may encode an input image in an intra mode or an inter mode and output a bitstream.

In the intra mode, the switch 115 may be switched to the intra mode, and in the inter mode, the switch 115 may be switched to the inter mode. Intra prediction refers to intra prediction, and inter prediction refers to inter prediction. The image encoding apparatus 100 may generate a prediction block for an input block of an input image, and then encode a residual between the input block and the prediction block. In this case, the input image may mean an original picture.

In the intra mode, the intra prediction unit 120 may use a sample value of an already encoded/decoded block around the current block as a reference sample. The intra prediction unit 120 may perform spatial prediction using a reference sample and generate prediction samples for the current block.

In the inter mode, the inter prediction unit 110 selects a motion vector specifying a reference block having the smallest difference from the input block (current block) in the reference picture stored in the reference picture buffer 190 during the motion prediction process. can be saved The inter prediction unit 110 may generate a prediction block for the current block by performing motion compensation using the motion vector and the reference picture stored in the reference picture buffer 190 .

In the case of a multi-layer structure, inter prediction applied in the inter mode may include inter-layer prediction. The inter prediction unit 110 may sample a picture of a reference layer to construct an inter-layer reference picture, and may perform inter-layer prediction by including the inter-layer reference picture in a reference picture list. A reference relationship between layers may be signaled through information specifying a dependency between layers.

Meanwhile, when the current layer picture and the reference layer picture have the same size, sampling applied to the reference layer picture may mean copying a sample from the reference layer picture or generating a reference sample by interpolation. When the resolution of the current layer picture and the reference layer picture are different, sampling applied to the reference layer picture may mean upsampling.

For example, when resolutions between layers are different, an inter-layer reference picture may be configured by upsampling a reconstructed picture of a reference layer between layers supporting resolution-related scalability.

Whether the picture of which layer is used to construct the inter-layer reference picture may be determined in consideration of encoding cost and the like. The encoding apparatus may transmit information specifying a layer to which a picture to be used as an inter-layer reference picture belongs to the decoding apparatus.

Also, a layer referenced in inter-layer prediction, that is, a picture used for prediction of a current block in a reference layer, may be a picture of the same access unit (AU) as the current picture (prediction target picture in the current layer).

The subtractor 125 may generate a residual block by the difference between the input block and the generated prediction block.

The transform unit 130 may perform transform on the residual block to output a transform coefficient. Here, the transform coefficient may mean a coefficient value generated by performing transform on the residual block and/or the residual signal. Hereinafter, in the present specification, a quantized transform coefficient level generated by applying quantization to a transform coefficient may also be referred to as a transform coefficient.

When a transform skip mode is applied, the transform unit 130 may skip transform on the residual block.

The quantization unit 140 may quantize the input transform coefficient according to a quantization parameter (or quantization parameter) to output a quantized coefficient. The quantized coefficient may be referred to as a quantized transform coefficient level. In this case, the quantization unit 140 may quantize the input transform coefficient using a quantization matrix.

The entropy encoding unit 150 may entropy-encode the values calculated by the quantization unit 140 or the encoding parameter values calculated during the encoding process according to a probability distribution to output a bitstream. The entropy encoder 150 may entropy-encode information for video decoding (eg, a syntax element, etc.) in addition to pixel information of the video.

The encoding parameter is information necessary for encoding and decoding, and may include information that is encoded in the encoding apparatus and transmitted to the decoding apparatus, such as a syntax element, as well as information that can be inferred during encoding or decoding.

For example, the coding parameter includes values such as intra/inter prediction mode, motion/motion vector, reference image index, coding block pattern, presence or absence of residual signal, transform coefficient, quantized transform coefficient, quantization parameter, block size, block partition information, etc. or statistics.

The residual signal may mean a difference between the original signal and the predicted signal, and a signal in which the difference between the original signal and the predicted signal is transformed or a signal in which the difference between the original signal and the predicted signal is transformed and quantized. may mean The residual signal may be referred to as a residual block in block units.

When entropy encoding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence and a large number of bits are allocated to a symbol having a low probability of occurrence to express the symbol, so that the size of the bit stream for the symbols to be encoded is increased. can be reduced. Accordingly, compression performance of image encoding may be improved through entropy encoding.

The entropy encoder 150 may use an encoding method such as exponential golomb, Context-Adaptive Variable Length Coding (CAVLC), or Context-Adaptive Binary Arithmetic Coding (CABAC) for entropy encoding. For example, the entropy encoding unit 150 may perform entropy encoding using a variable length coding (VLC) table. In addition, the entropy encoder 150 derives a binarization method of a target symbol and a probability model of a target symbol/bin, and then performs entropy encoding using the derived binarization method or probability model. You may.

Since the image encoding apparatus 100 according to the embodiment of FIG. 1 performs inter prediction encoding, that is, inter prediction encoding, the currently encoded image needs to be decoded and stored to be used as a reference image. Accordingly, the quantized coefficient may be inverse quantized by the inverse quantizer 160 and inversely transformed by the inverse transform unit 170 . The inverse quantized and inverse transformed coefficients are added to the prediction block through the adder 175, and a reconstructed block is generated.

The reconstructed 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 the reconstructed block or the reconstructed picture. can do. The filter unit 180 may be referred to as an adaptive in-loop filter. The deblocking filter can remove block distortion caused at the boundary between blocks. The SAO may add an appropriate offset value to a pixel value to compensate for a coding error. The ALF may perform filtering based on a value obtained by comparing the reconstructed image and the original image. The reconstructed block that has passed through the filter unit 180 may be stored in the reference picture buffer 190 .

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

A scalable video decoding apparatus supporting a multi-layer structure may be implemented by extending a general image decoding apparatus having a single layer structure. The block diagram of FIG. 2 illustrates an embodiment of an image decoding apparatus that can be the basis of a scalable video decoding apparatus applicable to a multi-layer structure.

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 , an inter prediction unit 250 , and an adder 255 . ), a filter unit 260 and a reference picture buffer 270 .

The image decoding apparatus 200 may receive a bitstream output from the encoder, perform decoding in an intra mode or an inter mode, and output a reconstructed image, that is, a reconstructed image.

In the case of the intra mode, the switch may be switched to the intra mode, and in the case of the inter mode, the switch may be switched to the inter mode.

The image decoding apparatus 200 obtains a reconstructed residual block from the received bitstream, generates a prediction block, and then adds the reconstructed residual block and the prediction block to generate a reconstructed block, that is, a reconstructed block. .

The entropy decoding unit 210 may entropy-decode the input bitstream according to a probability distribution and output information such as a quantized coefficient and a syntax element.

The quantized coefficient is inverse quantized by the inverse quantization unit 220 and inversely transformed by the inverse transform unit 230 . As a result of inverse quantization/inverse transformation of the quantized coefficient, a reconstructed residual block may be generated. In this case, the inverse quantizer 220 may apply a quantization matrix to the quantized coefficients.

In the intra mode, the intra prediction unit 240 may perform spatial prediction using sample values of an already decoded block around the current block, and generate prediction samples for the current block.

In the inter mode, the inter prediction unit 250 may generate a prediction block for the current block by performing motion compensation using a motion vector and a reference picture stored in the reference picture buffer 270 .

In the case of a multi-layer structure, inter prediction applied in the inter mode may include inter-layer prediction. The inter prediction unit 250 may sample a picture of a reference layer to construct an inter-layer reference picture, and may perform inter-layer prediction by including the inter-layer reference picture in a reference picture list. A reference relationship between layers may be signaled through information specifying a dependency between layers.

Meanwhile, when the current layer picture and the reference layer picture have the same size, sampling applied to the reference layer picture may mean copying a sample from the reference layer picture or generating a reference sample by interpolation. When the resolution of the current layer picture and the reference layer picture are different, sampling applied to the reference layer picture may mean upsampling.

For example, if inter-layer prediction is applied between layers supporting resolution-related scalability when resolutions between layers are different, an inter-layer reference picture may be configured by upsampling the reconstructed picture of the reference layer.

In this case, information specifying a layer to which a picture to be used as an inter-layer reference picture belongs may be transmitted from the encoding apparatus to the decoding apparatus.

Also, a layer referenced in inter-layer prediction, that is, a picture used for prediction of a current block in a reference layer, may be a picture of the same access unit (AU) as the current picture (prediction target picture in the current layer).

The reconstructed residual block and the prediction block are added by an adder 255 to generate a reconstructed block. In other words, a reconstructed sample or a reconstructed picture is generated by adding the residual sample and the prediction sample.

The reconstructed picture is filtered by 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 or filtered reconstructed picture. The reconstructed image may be stored in the reference picture buffer 270 and used for inter prediction.

Also, the image decoding apparatus 200 may further include a parsing unit (not shown) that parses information related to the encoded image included in the bitstream. The parsing unit may include the entropy decoding unit 210 or may be included in the entropy decoding unit 210 . This parsing unit may also be implemented as one component of the decoding unit.

1 and 2, it has been described that one encoding apparatus/decoding apparatus processes both encoding/decoding for multi-layers, but this is for convenience of description, and the encoding apparatus/decoding apparatus may be configured for each layer.

In this case, the encoding/decoding apparatus of the higher layer may perform encoding/decoding of the corresponding higher layer by using the information of the higher layer and the information of the lower layer. For example, the prediction unit (inter prediction unit) of the higher layer may perform intra prediction or inter prediction on the current block using pixel information or picture information of the upper layer, and receives picture information reconstructed from the lower layer and It may be used to perform inter prediction (inter-layer prediction) on the current block of a higher layer. Here, only inter-layer prediction has been described as an example, but the encoding/decoding apparatus performs encoding/decoding on the current layer using information of another layer, regardless of whether the encoding apparatus/decoding apparatus is configured for each layer or whether one apparatus processes multi-layers. can do.

In the present invention, a layer may include a view. In this case, in the case of inter-layer prediction, the prediction of the upper layer is not simply performed using the information of the lower layer, but information of another layer between the layers specified as having dependence by the information specifying the inter-layer dependence. Inter-layer prediction may be performed using .

3 is a conceptual diagram schematically illustrating an embodiment of a scalable video coding structure using a plurality of layers to which the present invention can be applied. In FIG. 3 , a group of pictures (GOP) indicates a picture group, that is, a group of pictures.

A transmission medium is required to transmit image data, and its performance is different 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.

A video coding method supporting scalability (hereinafter referred to as 'scalable coding' or 'scalable video coding') removes redundancy between layers by using texture information, motion information, and residual signals between layers. This is a coding method that improves encoding and decoding performance. The scalable video coding method uses a variety of scalers in terms of spatial, temporal, picture quality (or quality), and view, depending on ambient conditions such as transmission bit rate, transmission error rate, and system resources. You can provide a property.

Scalable video coding may be performed using a structure of multiple layers 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 decoding method, and compresses image data using both decoding information of the base layer and a general image decoding method. It may include an enhancement layer that handles it.

The base layer may be referred to as a base layer or a lower layer. The enhancement layer may be referred to as an enhancement layer or a higher layer. In this case, the lower layer may mean a layer supporting scalability lower than a specific layer, and the upper layer may mean a layer supporting scalability higher than a specific layer. Also, a layer referenced for encoding/decoding of another layer may be referred to as a reference layer (reference layer), and a layer encoded/decoded using another layer may be referred to as a current layer (current layer). The reference layer may be a lower layer than the current layer, and the current layer may be a layer higher than the reference layer.

Here, the layer is based on spatial (eg, image size), temporal (eg, decoding order, image output order, frame rate), image quality, complexity, view, etc. It means a set of differentiated images and bitstreams.

Referring to FIG. 3 , for example, the base layer may be defined as SD (standard definition), a frame rate of 15 Hz, and a bit rate of 1 Mbps, and the first enhancement layer is HD (high definition), a frame rate of 30 Hz, and a bit rate of 3.9 Mbps. may be defined, and the second enhancement layer may be defined as 4K-UHD (ultra high definition), a frame rate of 60 Hz, and a bit rate of 27.2 Mbps.

The format, frame rate, bit rate, etc. are one embodiment and may be differently determined as needed. Also, the number of layers to be used is not limited to the present embodiment and may be determined differently according to circumstances. For example, if the transmission bandwidth is 4 Mbps, the frame rate of the first enhancement layer HD may be reduced to transmit at 15 Hz or less.

The scalable video coding method may provide temporal, spatial, image quality, and view scalability by the method described above in the embodiment of FIG. 3 . In the present specification, scalable video coding has the same meaning as scalable video encoding from an encoding point of view and scalable video decoding from a decoding point of view.

In general, in inter prediction (hereinafter, inter prediction), at least one of a picture before or after a current picture is used as a reference picture, and prediction of the current block may be performed based on the reference picture.

An image used for prediction of the current block is referred to as a reference picture or a reference frame.

A region (reference block) used for prediction of a current block in a reference picture may be indicated using a reference picture index refIdx indicating a reference picture, a motion vector, and the like.

Inter prediction may generate a prediction block for the current block by selecting a reference picture and a reference block corresponding to the current block in the reference picture. In this case, in the inter prediction, a prediction block may be generated such that a residual signal with a current block is minimized and a motion vector size is also minimized.

In order to use the information of the reference picture in inter prediction, information on neighboring blocks located around the current block may be used. For example, for inter prediction, a skip mode, a merge mode, Advanced Motion Vector Prediction (AMVP), etc. may be applied according to a method of using information of neighboring blocks. The skip mode, merge mode, and AMVP mode may generate a prediction block for the current block based on information on neighboring blocks.

In the skip mode, information of a neighboring block may be used for the current block as it is. Therefore, when the skip mode is applied, the encoder only needs to transmit information indicating which neighboring block motion information to use as the motion information of the current block to the decoder, and other syntax information such as residuals are not transmitted to the decoder. .

In the merge mode, a prediction block for the current block may be generated by using motion information of a neighboring block as it is. When the merge mode is applied, the encoder may transmit information indicating whether the merge mode is applied to the current block, information indicating which neighboring block motion information is to be used, residual information on the current block, etc. to the decoder. . The decoder may generate a prediction block for the current block by using motion information of the neighboring block indicated by the encoder, and may reconstruct the current block by adding the generated prediction block to the residual transmitted from the encoder.

AMVP may predict the motion vector of the current block by using motion information of neighboring blocks. When AMVP is applied, the encoder may transmit information indicating which neighboring block motion information to use, the difference between the motion vector of the current block and the predicted motion vector, a reference picture index indicating a reference picture, etc. to the decoder. . The decoder may predict the motion vector of the current block using motion information (motion vector) of the neighboring block, and may derive the motion vector for the current block using the difference between the motion vectors received from the encoder. The decoder may generate a prediction block for the current block based on the derived motion vector and reference picture index information received from the encoder.

In the case of inter prediction, the decoder checks the skip flag and merge flag received from the encoder, and according to the checked information, the motion information required for inter prediction of the current block (for example, information about a motion vector, reference picture index, etc.) is derived. can

A processing unit in which prediction is performed may be different from a processing unit in which a prediction method and specific content are determined. For example, whether inter prediction or intra prediction is determined in units of a coding unit (CU) may be determined, and a prediction mode for intra prediction and a prediction mode for inter prediction may be determined in units of prediction units (PU). have. Alternatively, a prediction mode may be determined in units of prediction units and prediction may be performed in units of transform units (TUs).

On the other hand, in a scalable video coding structure that supports a plurality of layers, strong correlation exists between layers. Therefore, if prediction is performed using this correlation, duplicate elements of data can be removed and image encoding performance can be improved. have. Therefore, when predicting a picture (video) of a current layer (higher layer) to be encoded/decoded, inter-layer prediction using information of other layers as well as inter prediction or intra prediction using information of the current layer (inter-layer prediction, Alternatively, inter-layer prediction) may be performed.

Since at least one of a resolution, a frame rate, a color format, and a viewpoint of a plurality of layers may be different from each other (ie, a scalability difference between layers), signal distortion may occur during inter-layer prediction for the current layer, and a residual signal may increase.

Therefore, in the present invention, the motion information of the reference layer (lower layer) referred to by the current layer (upper layer) is mapped to the image size of the current layer and then added to the reference picture list of the current layer to the current layer. A method for performing inter prediction for

In addition, the present invention relates to encoding and decoding of an image including a plurality of layers or views, wherein the plurality of layers or views includes a first, second, third, n-th layer or a first; The second, third, and n-th views may be expressed.

Hereinafter, in an embodiment of the present invention, an image in which the first layer and the second layer exist is described as an example for convenience of description, but the same method may be applied to an image in which more layers or viewpoints exist. In addition, the first layer may be expressed as a lower layer, a base layer, or a reference layer, and the second layer may be expressed as an upper layer, an enhancement layer, or a current layer.

4 is a flowchart schematically illustrating a method of performing inter-layer prediction (inter-layer prediction) in scalable video coding according to an embodiment of the present invention. The method of FIG. 4 may be performed by the above-described image encoding apparatus of FIG. 1 and the image decoding apparatus of FIG. 2 .

Referring to FIG. 4 , the encoding/decoding apparatus decodes information of a first layer referred to by an image (picture) of a second layer (S400).

As described above, the second layer means a layer currently performing encoding/decoding, and may be a higher layer that provides higher scalability than the first layer. The first layer may be a layer referred to for encoding/decoding of the second layer, and may be referred to as a reference layer or a lower layer.

The encoding/decoding apparatus may decode and use information of the first layer as a reference signal for predicting an encoding/decoding target block in an image of the second layer.

Information on the first layer to be decoded (information on the decoding target of the first layer) may include sample values and motion information of the first layer image (picture). Here, the motion information includes a motion vector value, a reference picture index, a prediction direction indicator, a reference picture picture order count (POC), a prediction mode, a reference picture list, a merge flag, a merge index, and a picture type of the reference picture (short-term ) may be information about a reference picture, a long-term reference picture), and the like.

The decoded motion information of the first layer may be compressed and stored in NxN unit blocks. For example, the decoded motion information of the first layer may be compressed and stored for every 16x16 block.

The encoding/decoding apparatus maps the decoded information of the first layer to the image size of the second layer (S410).

Here, the mapping may be to perform sampling on a sample of an image in order to adjust the image size or resolution to be the same when the size or resolution between the images is different, and sampling of image sample values and motion information of the image sampling may be included.

In other words, the encoding/decoding apparatus may perform sampling on the decoded first hierarchical image in order to map the decoded first hierarchical image to the size of the second hierarchical image, and a sample value of the sampled first hierarchical image and motion information.

In the scalable video coding structure, since the size of an image between layers may be different, when the size of an image between layers (between the first layer and the second layer) is different, the encoding/decoding apparatus adjusts the size of the image of the decoded first layer. Resampling may be performed on sample values of the decoded first layer image to be mapped to the image size of the second layer.

For example, when the decoded image size of the first layer is 960x540 and the image size of the second layer is 1920x1080, the encoding/decoding apparatus converts the decoded image size of the first layer to the size of 1920x1080, which is the image size of the second layer. Upsampling for mapping may be performed. Upsampling may be performed to adjust the image size between layers having different image sizes, and interpolated samples are derived by applying interpolation to images of a layer (reference layer or lower layer) having a small image size. and the image size can be adjusted.

The encoding/decoding apparatus may use the decoded motion information of the first layer by mapping it to the image size of the second layer. In the inter-layer motion information mapping for mapping the decoded motion information of the first layer image to the image size of the second layer, the second layer image is divided into NxN unit blocks, and for each NxN unit block of the second layer The corresponding motion information of the first layer may be used as motion information of the corresponding block of the second layer.

Hereinafter, an inter-layer motion information mapping method according to an embodiment of the present invention will be described with reference to FIGS. 5 and 6 .

5 and 6 are diagrams illustrating an inter-layer motion information mapping method according to an embodiment of the present invention.

5 shows an image of the second layer divided into NxN unit blocks.

For example, as shown in FIG. 5, when the size of the image of the second layer is 1920x1080 and N=16, the encoding/decoding apparatus can divide the image of the second layer into a total of 8160 16x16 unit blocks, The motion information of the first layer block corresponding to each unit block of the second layer may be used as the motion information of the corresponding block of the second layer.

In this case, the motion information may be stored for each unit block. Alternatively, the motion information may be stored in the form of a look-up table for each picture and used by reference by each unit block.

6 shows an NxN block of the second layer, and as an example, a 16x16 block 600 in the case of N=16 is shown. Each rectangle in the 16x16 block 600 means one sample, and it is assumed that the left-most sample position in the 16x16 block 600 is (xP, yP).

As described above, when mapping the inter-layer motion information, the motion information of the first layer block corresponding to each NxN unit block of the second layer is used by mapping the motion information of the second layer. In this case, the motion information of the first layer block corresponding to each NxN block of the second layer may be motion information of the first layer sample position corresponding to the reference sample position of the second layer NxN block.

For example, as shown in FIG. 6 , the encoding/decoding apparatus determines the (xP+8, yP+8) position in the 16x16 block 600 of the second layer as the reference sample position, and the reference sample position (xP Inter-layer motion information mapping may be performed using motion information of the first layer sample position corresponding to +8, yP+8).

Alternatively, the encoding/decoding apparatus determines the (xP, yP) position in the 16x16 block 600 of the second layer as the reference sample position, and motion information of the first layer sample position corresponding to the reference sample position (xP, yP) can be used to perform inter-layer motion information mapping.

Alternatively, the encoding/decoding apparatus determines the (xP+15, yP) position in the 16x16 block 600 of the second layer as the reference sample position, and the first layer sample corresponding to the reference sample position (xP+15, yP) Inter-layer motion information mapping may be performed using motion information of a location.

Alternatively, the encoding/decoding apparatus determines the (xP, yP+15) position in the 16x16 block 600 of the second layer as the reference sample position, and the first layer sample corresponding to the reference sample position (xP, yP+15) Inter-layer motion information mapping may be performed using motion information of a location.

Alternatively, the encoding/decoding apparatus determines the (xP+15, yP+15) position in the 16x16 block 600 of the second layer as the reference sample position, and corresponds to the reference sample position (xP+15, yP+15). Inter-layer motion information mapping may be performed using the motion information of the first layer sample location.

Alternatively, the encoding/decoding apparatus determines the position (xP+1, yP+1) in the 16x16 block 600 of the second layer as the reference sample position, and corresponds to the reference sample position (xP+1, yP+1). Inter-layer motion information mapping may be performed using the motion information of the first layer sample location.

The encoding/decoding apparatus may perform inter-layer motion information mapping using motion information of the first layer sample location corresponding to the reference sample location as well as the aforementioned reference sample location using another reference sample location.

The sample position of the first layer corresponding to the reference sample position of the second layer may be calculated as in Equation 1 below in consideration of the size of the inter-layer image.

Here, xRef and yRef are the sample positions of the first layer, xP and yP are the reference sample positions of the second layer, ScaledW and ScaledH are the horizontal and vertical sizes of the scaled first layer picture, and picWRL and picHRL are the first The horizontal and vertical sizes of the hierarchical picture.

For example, if the motion information of the first layer is compressed and stored in units of 16x16, the sample position of the first layer calculated by Equation 1 may use the motion information in units of 16x16 through Equation 2 below. can be adjusted to

As another example, when the motion information of the first layer is compressed and stored in units of 8x8, the sample position of the first layer calculated by Equation 1 is determined so that the motion information in units of 8x8 can be used through Equation 3 below. can be adjusted.

When the prediction mode of the sample position of the first layer corresponding to the reference sample position of the second layer is the intra prediction mode, the encoding/decoding apparatus may use (0, 0) as the motion vector value of the corresponding block of the second layer, A value of -1 may be assigned to the reference picture index and reference picture POC of the second layer corresponding block.

Alternatively, when the prediction mode of the sample position of the first layer corresponding to the reference sample position of the second layer is the intra prediction mode, the encoding/decoding apparatus may use (0, 0) as the motion vector value of the corresponding block of the second layer. In the second layer, a specific value (for example, the reference picture index is assigned as 0, and the reference picture POC is assigned as the POC of the picture indicated by the reference picture index 0) is assigned to the reference picture index and the reference picture POC of the second layer corresponding block. can be assigned

When the prediction mode of the sample position of the first layer corresponding to the reference sample position of the second layer is the inter prediction mode, the encoding/decoding apparatus refers to the motion vector value of the sample position of the first layer as motion information of the corresponding block of the second layer. A picture index and a reference picture POC value may be used.

When using the motion vector of the first layer, the encoding/decoding apparatus may use the motion vector of the first layer by reflecting the size of the inter-layer image as shown in Equation 4 below.

The encoding/decoding apparatus obtains picture type information (picture type information on whether the reference picture is a short-term reference picture or a long-term reference picture) of the reference picture referenced by the corresponding block of the first layer corresponding to the block of the second layer. It can be used as information of the layer corresponding block.

The above-described inter-layer motion information mapping may be determined at a higher level, and the encoding apparatus may transmit inter-layer motion information mapping related information at a higher level. The decoding apparatus may obtain inter-layer motion information mapping related information from a higher level.

The higher level may be a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), a slice segment header, and the like.

Hereinafter, a method of signaling information related to motion information mapping at a higher level according to an embodiment of the present invention will be described.

According to an embodiment of the present invention, as shown in Table 1, information related to motion information mapping of a corresponding layer may be signaled in the VPS.

Referring to Table 1, when inter_layer_mfm_enable_flag is 0, motion information mapping of the i-th layer may not be performed.

When inter_layer_mfm_enable_flag is 1, motion information mapping of the i-th layer may be performed.

According to another embodiment of the present invention, as shown in Table 2, information related to motion information mapping of a corresponding layer may be signaled in the extension of the SPS.

Referring to Table 2, when sps_inter_layer_mfm_enable_flag is 0, motion information mapping of the first layer may not be performed.

When sps_inter_layer_mfm_enable_flag is 1, motion information mapping of the first layer may be performed.

* According to another embodiment of the present invention, as shown in Table 3, according to information indicating whether to use temporal motion vector prediction transmitted from the SPS (eg, sps_temporal_mvp_enabled_flag) It may determine whether to transmit information (eg, sps_inter_layer_mfm_enable_flag).

Referring to Table 3, when sps_temporal_mvp_enabled_flag indicating whether to use temporal motion vector prediction is 1, sps_inter_layer_mfm_enable_flag indicating whether to perform motion information mapping of the first layer may be transmitted.

When sps_temporal_mvp_enabled_flag is 1 and sps_inter_layer_mfm_enable_flag is 0, motion information of the first layer may not be used in the second layer. That is, the reconstructed image of the first layer may not be used as a temporal motion vector predictor (TMVP) of the second layer.

According to another embodiment of the present invention, whether or not to perform motion information mapping of a corresponding layer may be determined by the sps_temporal_mvp_enabled_flag value without transmission of sps_inter_layer_mfm_enable_flag as in Table 3 above. For example, when sps_temporal_mvp_enabled_flag is 1, it is assumed that sps_inter_layer_mfm_enable_flag is 1, and motion information mapping of the corresponding layer may be performed. When sps_temporal_mvp_enabled_flag is 0, it is assumed that sps_inter_layer_mfm_enable_flag is 0, and motion information mapping of the corresponding layer may be performed.

According to another embodiment of the present invention, as shown in Table 4, information related to motion information mapping of a corresponding layer may be signaled in the extension of the PPS.

Referring to Table 4, when pps_inter_layer_mfm_enable_flag is 0, motion information mapping of the first layer may not be performed.

When pps_inter_layer_mfm_enable_flag is 1, motion information mapping of the first layer may be performed.

According to another embodiment of the present invention, as shown in Table 5, information related to motion information mapping of a corresponding layer may be signaled in an extension of a slice segment header.

Referring to Table 5, when slice_inter_layer_mfm_enable_flag is 0, motion information mapping of the first layer may not be performed.

When slice_inter_layer_mfm_enable_flag is 1, motion information mapping of the first layer may be performed.

According to another embodiment of the present invention, as shown in Table 6, information related to motion information mapping of a corresponding layer may be signaled in an extension of a slice segment header.

Referring to Table 6, when slice_temporal_mvp_enabled_flag indicating whether to use temporal motion vector prediction is 1, slice_inter_layer_mfm_enable_flag indicating whether to perform motion information mapping of the first layer may be transmitted. slice_inter_layer_mfm_enable_flag is transmitted only in layers other than the base layer (ie, enhancement layer), and in the case of the enhancement layer, if a layer used for motion prediction does not exist, slice_inter_layer_mfm_enable_flag may not be transmitted. If the corresponding flag does not exist, the corresponding flag value can be inferred to be 0.

When slice_temporal_mvp_enabled_flag is 1 and slice_inter_layer_mfm_enable_flag is 0, the motion information of the first layer may not be used in the second layer. That is, the reconstructed image of the first layer may not be used as a temporal motion vector prediction (TMVP) of the second layer.

When slice_inter_layer_mfm_enable_flag is transmitted in a layer other than the base layer (ie, enhancement layer), slice_inter_layer_mfm_enable_flag may exist above the slice_segement_header_extension_present_flag in the slice segment header of the layer other than the base layer (ie, enhancement layer) as shown in Table 7.

Referring to Table 7, when slice_temporal_mvp_enabled_flag indicating whether to use temporal motion vector prediction is 1, slice_inter_layer_mfm_enable_flag indicating whether to perform motion information mapping of the first layer may be transmitted.

When slice_temporal_mvp_enabled_flag is 1 and slice_inter_layer_mfm_enable_flag is 0, the motion information of the first layer may not be used in the second layer. That is, the reconstructed image of the first layer may not be used as a temporal motion vector predictor (TMVP) of the second layer.

When slice_temporal_mvp_enabled_flag is 1 and slice_inter_layer_mfm_enable_flag is 1, motion information of the first layer may be used in the second layer. That is, after mapping the motion information of the first layer to the size of the second layer, the reconstructed image of the first layer may be used as a corresponding picture (ColPic, Collocated picture) for TMVP of the second layer.

When slice_inter_layer_mfm_enable_flag is 1, as shown in Table 8, information on a corresponding picture (ColPic, Collocated picture) of the first layer for TMVP of the second layer may be signaled through additional syntax information. For example, information of a referenced layer may be known through collocated_ref_layer_idx, and motion information of a picture corresponding to the reference layer may be mapped to an image size of a second layer. Also, in the case of a B slice, a reference picture list direction in which a picture of a reference layer that can be used as a corresponding picture is located may be determined through collocated_ref_layer_from_10_flag.

Referring to Table 8, collocated_ref_layer_idx is an indicator indicating information of reference layers used for motion prediction when the number of reference layers used for motion prediction is two or more. When the number of reference layers used for motion prediction is one, collocated_ref_layer_idx may be omitted. In this case, a constraint that all slices in a picture must have the same value may be applied.

collocated_ref_layer_from_10_flag is transmitted in B slice. When the collocated_ref_layer_from_10_flag value is 1, the picture of the reference layer existing in LIST0 is set as the corresponding picture (ColPic). When the collocated_ref_layer_from_10_flag value is 0, the picture of the reference layer existing in LIST1 is set as the corresponding picture (ColPic). Thereafter, in the process of obtaining the motion vector of the corresponding block ColPb in the corresponding picture ColPic, the collocated_ref_layer_from_10_flag value may be used with the same meaning instead of collocated_from_10_flag. In this case, a constraint that all slices in a picture must have the same value may be applied. Alternatively, if the corresponding block has motion information in both LIST0 and LIST1 directions in the process of obtaining the motion vector of the corresponding block ColPb in the corresponding picture ColPic, the same direction as the direction indicated by the current encoding/decoding target picture of motion information can be obtained.

When the base layer or slice_inter_layer_mfm_enable_flag is 0, the list direction and the corresponding picture in the second layer can be informed by using collocated_from_10_flag and collocated_ref_idx without using motion information of the reference layer.

When slice_inter_layer_mfm_enable_flag is 1, information on the corresponding picture (ColPic, Collocated picture) of the first layer for TMVP of the second layer and reference picture list direction information may be signaled using additional syntax information as shown in Table 9. . For example, when slice_temporal_mvp_enabled_flag is 1, for the B slice, the reference picture list direction of the corresponding picture can be determined from the collocated_from_10_flag value, and the referenced layer can be known from the collocated_ref_layer_idx value.

Referring to Table 9, collocated_from_10_flag indicates a reference picture list direction to which a corresponding picture belongs when slice_temporal_mvp_enabled_flag is 1 and it is a B slice. When collocated_from_10_flag does not exist, collocated_from_10_flag may be inferred to be 1. In this case, a constraint that all slices in a picture must have the same value may be applied.

collocated_ref_layer_idx is an indicator indicating information of a reference layer used for motion prediction when the number of reference layers used for motion prediction is two or more. When the number of reference layers used for motion prediction is one, collocated_ref_layer_idx may be omitted. In this case, a constraint that all slices in a picture must have the same value may be applied. The list direction for the corresponding picture can be determined from the collocated_from_10_flag transmitted from the upper layer.

When the base layer or slice_inter_layer_mfm_enable_flag is 0, the list direction and the corresponding picture in the second layer can be informed by using collocated_from_10_flag and collocated_ref_idx without using motion information of the reference layer.

When slice_inter_layer_mfm_enable_flag is 1, as shown in Table 10, information of a referenced layer can be known through collocated_ref_layer_idx, and motion information of a picture corresponding to the reference layer can be mapped to the image size of the second layer. At this time, according to the slice type, in the case of a P slice, a picture of a reference layer existing in LIST0 is used as a corresponding picture, and in the case of a B slice, a contract is made in either direction of LIST0 or LIST1, and the picture of the corresponding reference layer is the corresponding picture. Therefore, the encoding/decoding device can use the same.

When the base layer or slice_inter_layer_mfm_enable_flag is 0, the list direction and the corresponding picture in the second layer can be informed by using collocated_from_10_flag and collocated_ref_idx without using motion information of the reference layer.

According to another embodiment of the present invention, when a picture is divided into N independent slices, slice_inter_layer_mfm_enable_flag in each slice segment header must have the same value, and according to the value of slice_inter_layer_mfm_enable_flag in the first independent slice segment header A motion information mapping process may be performed once per picture.

In the above-described embodiments of the present invention, 'sps_inter_layer_mfm_enable_flag' transmitted from a higher level is used as information indicating whether motion information mapping is performed. have. For example, when sps_inter_layer_mfm_enable_flag is 1, not only motion information mapping but also inter-layer syntax (motion information) prediction may be performed.

In the above-described embodiments of the present invention, a separate syntax indicating whether motion information mapping is performed is used. However, motion information mapping may be performed according to a syntax information value for performing inter-layer prediction without separate syntax transmission.

In the present invention, it is possible to determine whether motion information mapping is performed using syntax information indicating whether inter-layer prediction signaled by a higher layer is performed. Syntax information indicating whether the inter-layer prediction is performed may be signaled at a higher level.

Here, the higher level may be a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), a slice segment header, and the like.

According to an embodiment of the present invention, as shown in Table 11, a syntax indicating whether inter-layer prediction is performed in the VPS may be transmitted.

Referring to Table 11, when a syntax indicating whether inter-layer prediction is performed in the VPS is transmitted, if no_inter_layer_pred_flag is 1, motion information mapping may not be performed, and if no_inter_layer_pred_flag is 0, motion information mapping may be performed.

In the present invention, it is possible to determine whether to perform motion information mapping using syntax information indicating whether or not to perform inter-layer syntax prediction signaled by a higher layer. Syntax information indicating whether to perform the inter-layer syntax prediction may be signaled at a higher level.

Here, the higher level may be a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), a slice segment header, and the like.

According to an embodiment of the present invention, as shown in Table 12, a syntax indicating whether inter-layer syntax prediction is performed in the PPS may be transmitted.

Referring to Table 12, when a syntax indicating whether to perform inter-layer syntax prediction is transmitted in the PPS, motion information mapping may be performed if no_inter_layer_syntax_pred_flag is 0, and if no_inter_layer_syntax_pred_flag is 1, motion information mapping may not be performed. have.

According to another embodiment of the present invention, as shown in Table 13, a syntax indicating whether inter-layer syntax prediction is performed may be transmitted in the slice segment header.

Referring to Table 13, when a syntax indicating whether to perform inter-layer syntax prediction is transmitted in the slice segment header, if no_inter_layer_syntax_pred_flag is 0, motion information mapping may be performed. If no_inter_layer_syntax_pred_flag is 1, motion information mapping is not performed. may not be

Referring back to FIG. 4 , the encoding/decoding apparatus encodes/decodes the image of the second layer by adding the information of the first layer to the reference picture list of the second layer ( S420 ).

That is, the encoding/decoding apparatus converts the decoded sample values and motion information of the first layer mapped to the second layer image size through the above-described steps S400 to S410 to the reference picture list for the current encoding/decoding target image of the second layer. can be added, and the reference picture list of the second layer image can be constructed using the added information of the first layer. In addition, the encoding/decoding apparatus may perform inter prediction for generating a prediction signal with respect to the image of the second layer based on the reference picture list.

When constructing the reference picture list of the second layer, the decoded image of the first layer may be added to the last position of the reference picture list for the current encoding/decoding target image of the second layer.

Alternatively, the decoded image of the first layer may be added to a specific position of the reference picture list for the current encoding/decoding target image of the second layer. In this case, the specific location may be informed at a higher level (eg, VPS, SPS, PPS, slice segment header, etc.), or the specific location may be designated by a set protocol without transmitting additional information.

Alternatively, the decoded image of the first layer may be added to the reference picture lists L0 and L1 for the current encoding/decoding target image of the second layer. In this case, the positions added to the reference picture lists L0 and L1 may be the same or different. For example, the decoded image of the first layer may be added to the first position in the reference picture list L0, and the decoded image of the first layer may be added to the last position in the reference picture list L1.

Alternatively, the decoded image of the first layer may be added to any one of the reference picture list directions (L0 and L1) for the current encoding/decoding target image of the second layer. For example, when the current encoding/decoding target image of the second layer is encoded/decoded into a B slice, the decoded image of the first layer may be added only to the reference picture list L0 or the reference picture list L1.

In this case, when adding the decoded image of the first layer to the reference picture list in a specific direction, at a higher level (eg, VPS, SPS, PPS, slice segment header, etc.) in the reference picture list in a specific direction at any position The location to be added may be indicated, or a specific location may be designated according to a set protocol without transmitting additional information.

Alternatively, the decoded image of the first layer may be added to different positions of the reference picture list according to the depth using hierarchical depth information of the prediction structure. In this case, information on the location may be informed at a higher level (eg, VPS, SPS, PPS, slice segment header, etc.). For example, the first layer decoded image may have a different position added to the reference picture list based on a temporal level (temporal_Id) value according to the hierarchical depth. For example, when the temporal level (temporal_Id) is 2 or more, the decoded image of the first layer may be added to the last position of the reference picture list, and when the temporal level (temporal_Id) is less than 2, the reference picture list The decoded image of the first layer may be added to the first position of . In this case, the reference time level value may be informed at a higher level (eg, VPS, SPS, PPS, slice segment header, etc.).

The above-described decoded image of the first layer may include decoded motion information of the first layer mapped to the image size of the second layer as well as decoded sample values of the first layer.

The encoding/decoding apparatus adds the decoded image of the first layer to the reference picture list for the current encoding/decoding target image of the second layer in the same manner as described above, and then, using a normal inter prediction method, Prediction may be performed on the current encoding/decoding target image.

When prediction is performed using the decoded image of the first layer as a reference signal of the current encoding target image of the second layer (when inter-layer prediction is performed), the encoding apparatus predicts in the current encoding target image without a motion prediction process The first layer sample value at the same position as the block may be used as a prediction signal. In this case, the encoding apparatus may not transmit motion information (eg, a motion vector difference value, a motion prediction candidate flag, etc.) of the corresponding block.

When the image indicated by the reference picture index of the second layer is the decoded image of the first layer in the reference picture list, the decoding apparatus provides motion information (eg, motion) on the prediction block in the current decoding target image of the second layer. A first layer sample value at the same position as a prediction block in a current decoding target image may be used as a prediction signal without decoding a vector difference value, a motion prediction candidate flag, etc.).

When the image indicated by the reference picture index of the current decoding object block of the second layer is the decoded image of the first layer in the reference picture list (inter-layer prediction is performed), the decoding apparatus is at a higher level (eg, VPS , SPS, PPS, slice segment header, etc.), whether to decode motion information (eg, motion vector difference value, motion prediction candidate flag, etc.) for the current decoding object block of the second layer By determining whether or not there is a current decoding target block of the second layer, prediction may be performed.

Table 14 shows an example of a syntax in which information (sps_inter_layer_mv_zero_flag) indicating whether an inter-layer motion vector has a value (0, 0) is transmitted in the SPS.

Referring to Table 14, when sps_inter_layer_mv_zero_flag transmitted from the SPS has a value of 1 and the reference picture index of the current decoding object block indicates the decoded image of the first layer in the reference picture list, the decoding apparatus determines the motion vector difference Without decoding the value and the motion prediction candidate flag, a sample value of the decoded first layer image having the same position as the position of the current decoding object block may be used as a prediction signal for the current decoding object block.

When sps_inter_layer_mv_zero_flag transmitted from the SPS has a value of 0 and the reference picture index of the current decoding object block indicates the decoded image of the first layer in the reference picture list, the decoding apparatus performs the motion vector difference value and the motion prediction candidate flag After decoding , a motion vector value may be obtained, and a sample value of the decoded first layer image at the obtained motion vector value may be used as a prediction signal for the current decoding object block.

Meanwhile, in order to use the mapped motion information of the first layer as a temporal motion vector candidate for the current encoding object block of the second layer, the encoding apparatus performs temporal motion vector prediction of the second layer on the decoded image of the first layer. It can be used as a collocated picture for In this case, the encoding apparatus may designate the decoded image of the first layer as the corresponding image through information (collocated_ref_idx) indicating the corresponding picture in the slice segment header.

When the information (collocated_ref_idx) indicating the corresponding picture in the slice segment header transmitted from the encoder indicates the decoded image of the first layer, the decoding apparatus converts the mapped motion information of the first layer to the temporal motion vector candidate of the second layer can be used as

When the mapped motion information of the first layer is used as a temporal motion vector candidate of the second layer, the encoding/decoding apparatus performs the mapped motion information of the first layer, that is, the reference picture POC, the reference picture list, and the picture of the reference picture. One or more of type (short-term reference picture, long-term reference picture) information can be used, and by using one or more mapped motion information of the first layer, the motion vector of the second layer can be scaled to fit the temporal distance. have.

When prediction is performed by adding only reference sample values of the decoded first layer image to the reference picture list without allowing motion information mapping of the first layer in a higher level, information indicating a corresponding picture (collocated_ref_idx) is the first layer A restriction may be placed on the standard document so as not to indicate the decoded image of the corresponding picture.

As another example of using the mapped motion information of the first layer as the motion information of the second layer, the mapped motion information of the first layer may be used as an additional candidate mode other than the temporal motion vector candidate of the second layer. In this case, so that the temporal motion vector candidate of the second layer can be derived from the reference picture of the second layer, the information (collocated_ref_idx) indicating the corresponding picture does not indicate the decoded image of the first layer as the corresponding picture. Constraints can be placed on standard documents. In addition, in order to use the motion information of the first layer mapped to the additional candidate mode, the encoding apparatus additionally adds an index (eg, base_ref_idx) that can inform the location of the mapped image of the first layer in the reference picture list slice segment It can be transmitted in headers, etc. The position of the additional rear mode in the reference picture list may be equally applied to the encoding apparatus and the decoding apparatus.

The method according to the present invention described above may be produced as a program to be executed by a computer and stored in a computer-readable recording medium. Examples of the computer-readable recording medium include ROM, RAM, CD-ROM, magnetic tape. , a floppy disk, an optical data storage device, and the like, and also includes those implemented in the form of a carrier wave (eg, transmission through the Internet).

The computer-readable recording medium is distributed in a network-connected computer system, so that the computer-readable code can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the method can be easily inferred by programmers in the art to which the present invention pertains.

In the above-described embodiments, 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 the steps, and some steps may occur in a different order or at the same time as other steps as described above. can In addition, those of ordinary skill in the art will recognize that the steps shown in the flowchart are not exclusive, other steps may be included, or that one or more steps in the flowchart may be deleted without affecting the scope of the present invention. You will understand.

The above description is merely illustrative of the technical spirit of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed by the claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (5)

In the image decoding method for performing inter-layer prediction,
determining whether inter-layer prediction is performed on the current decoding object block;
decoding a picture of a first layer; and
When the picture of the first layer is the picture of the layer referenced by the picture of the second layer including the current decoding object block, adding the picture of the first layer to the reference picture list for the picture of the second layer comprising steps,
The first layer is a base (Base) layer, the second layer is an enhancement layer,
When the picture of the first layer and the picture of the second layer have different sizes, the collocated-picture for prediction of the current decoding object block is not determined as the picture of the first layer, and the corresponding picture The picture decoding method, characterized in that the information indicating the picture does not indicate the picture of the first layer. The method of claim 1,
The picture of the first layer is characterized in that it is added to the reference picture list when the picture of the first layer and the picture of the second layer have the same picture order count (POC). The method of claim 1,
Whether the picture of the first layer is a picture of a layer referred to by the picture of the second layer is determined based on a layer ID of the picture of the second layer. In the video encoding method for performing inter-layer prediction,
determining that inter-layer prediction is to be performed on the current encoding object block;
deriving a picture of a first layer; and
When the picture of the first layer is the picture of the layer referenced by the picture of the second layer including the current encoding object block, adding the picture of the first layer to the reference picture list for the picture of the second layer comprising steps,
The first layer is a base (Base) layer, the second layer is an enhancement layer,
When the picture of the first layer and the picture of the second layer have different sizes, the collocated-picture for prediction of the current encoding object block is not determined as the picture of the first layer, and the corresponding picture The picture encoding method, characterized in that the information indicating the picture does not indicate the picture of the first layer. A recording medium for storing a bitstream generated by an image encoding method, the recording medium comprising:
The video encoding method comprises:
In the video encoding method for performing inter-layer prediction,
determining that inter-layer prediction is to be performed on the current encoding object block;
deriving a picture of a first layer; and
When the picture of the first layer is the picture of the layer referenced by the picture of the second layer including the current encoding object block, adding the picture of the first layer to the reference picture list for the picture of the second layer comprising steps;
The first layer is a base (Base) layer, the second layer is an enhancement layer,
When the picture of the first layer and the picture of the second layer have different sizes, the collocated-picture for prediction of the current encoding object block is not determined as the picture of the first layer, and the corresponding picture A recording medium for storing a bitstream generated by an image encoding method, characterized in that the information indicating the picture does not indicate the picture of the first layer.

Images