WO2012036436A2

WO2012036436A2 - Method and apparatus for entropy encoding/decoding

Info

Publication number: WO2012036436A2
Application number: PCT/KR2011/006726
Authority: WO
Inventors: 임성창; 김휘용; 정세윤; 조숙희; 김종호; 이하현; 이진호; 최진수; 김진웅; 안치득; 최해철
Original assignee: 한국전자통신연구원; 한밭대학교 산학협력단
Priority date: 2010-09-13
Filing date: 2011-09-09
Publication date: 2012-03-22
Also published as: WO2012036436A3

Abstract

Provided is an entropy decoding method. The entropy decoding method according to the present invention comprises the steps of: drawing context information about a symbol to be decoded using at least either context information about corresponding layer or context information about other layers; and performing entropy decoding on the symbol using the drawn context information. According to the present invention, image compression efficiency can be enhanced.

Description

Entropy encoding / decoding method and apparatus

The present invention relates to image processing, and more particularly, to an entropy encoding / decoding method and apparatus.

Recently, as broadcasting services having high definition (HD) resolution have been expanded not only in Korea but also in the world, many users are accustomed to high resolution and high quality images, and many organizations are accelerating the development of next generation video equipment. In addition, as interest in Ultra High Definition (UHD), which has four times the resolution of HDTV, is increasing along with HDTV, a compression technology for higher resolution and higher quality images is required.

For image compression, an inter prediction technique for predicting pixel values included in a current picture from a previous and / or subsequent picture in time, and predicting pixel values included in a current picture using pixel information in the current picture. An intra prediction technique, an entropy encoding technique of allocating a short code to a symbol with a high frequency of appearance and a long code to a symbol with a low frequency of appearance may be used.

Video compression technology is a technology that provides a constant network bandwidth under a limited operating environment of hardware without considering a fluid network environment. However, a new compression technique is required to compress image data applied to a network environment in which bandwidth changes frequently, and a scalable video encoding / decoding method may be used for this purpose.

An object of the present invention is to provide an entropy encoding method and apparatus capable of improving image compression efficiency.

Another object of the present invention is to provide a scalable video encoding method and apparatus for improving image compression efficiency.

Another technical problem of the present invention is to provide an entropy decoding method and apparatus which can improve image compression efficiency.

Another technical problem of the present invention is to provide a scalable video decoding method and apparatus capable of improving image compression efficiency.

One embodiment of the present invention is an entropy decoding method for multi-layer-based scalable video decoding. The method may include deriving context information of a symbol to be decoded using at least one of context information of a target layer and context information of another layer, and using the derived context information to decode the symbol to be decoded. And performing entropy decoding on the target layer, wherein the target layer is a layer including the decoding target symbol, and the other layer is a layer excluding the target layer, which can be used for decoding in the target layer. .

According to the present invention, entropy encoding / decoding performance and image compression efficiency can be improved.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment.

2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment.

3 is a conceptual diagram schematically illustrating an embodiment of a scalable video coding structure using multiple layers to which the present invention can be applied.

4 is a flowchart schematically showing an embodiment of an entropy encoding method according to the present invention.

5 is a flowchart schematically illustrating an embodiment of an entropy encoding method including a process of deriving context information.

6 is a flowchart schematically showing another embodiment of an entropy encoding method according to the present invention.

7 is a flowchart schematically illustrating still another embodiment of an entropy encoding method according to the present invention.

8 is a flowchart schematically illustrating still another embodiment of an entropy encoding method according to the present invention.

9 is a flowchart schematically showing an embodiment of an entropy decoding method according to the present invention.

10 is a flowchart schematically illustrating an embodiment of an entropy decoding method including a context information derivation process.

11 is a flowchart schematically showing another embodiment of an entropy decoding method according to the present invention.

12 is a flowchart schematically illustrating still another embodiment of an entropy decoding method according to the present invention.

13 is a flowchart schematically showing still another embodiment of an entropy decoding method according to 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, when it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present specification, the detailed description thereof will be omitted.

When a component is said to be “connected” or “connected” to another component, it may be directly connected to or connected to that other component, but it may be understood that another component may exist in between. Should be. In addition, the description "include" a specific configuration in the present invention does not exclude a configuration other than the configuration, it means that additional configuration may be included in the scope of the technical spirit of the present invention or 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. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that each component is made of separate hardware or one software component unit. In other words, each component is included in each component for convenience of description, and at least two of the components may be combined into one component, or one component may be divided into a plurality of components to perform a function. Integrated and separate embodiments of the components are also included within the scope of the present invention without departing from the spirit of the invention.

In addition, some of the components may not be essential components for performing essential functions in the present invention, but may be optional components for improving performance. The present invention can be implemented including only the components essential for implementing the essentials of the present invention except for the components used for improving performance, and the structure including only the essential components except for the optional components used for improving performance. Also included in the scope of the present invention.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment. A scalable video encoding / decoding method or apparatus may be implemented by an extension of a general video encoding / decoding method or apparatus that does not provide scalability, and the block diagram of FIG. 1 is scalable. An embodiment of an image encoding apparatus that may be the basis of a video encoding apparatus is illustrated.

Referring to FIG. 1, the image encoding apparatus 100 may include a motion predictor 111, a motion compensator 112, an intra predictor 120, a switch 115, a subtractor 125, and a converter 130. And 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 may perform encoding in an intra mode or an inter mode on an input image and output a bit stream. 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 may generate a prediction block for an input block of an input image and then encode a difference between the input block and the prediction block.

In the intra mode, the intra predictor 120 may generate a prediction block by performing spatial prediction using pixel values of blocks that are already encoded around the current block.

In the inter mode, the motion predictor 111 may obtain a motion vector by searching for a region that best matches an input block in the reference image stored in the reference image buffer 190 during the motion prediction process. The motion compensator 112 may generate a prediction block by performing motion compensation using the motion vector and the reference image stored in the reference image buffer 190.

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 output a transform coefficient by performing transform on the residual block. The quantization unit 140 may output the quantized coefficient by quantizing the input transform coefficient according to the quantization parameter.

The entropy encoding unit 150 entropy encodes a symbol according to a probability distribution based on values calculated by the quantization unit 140 or encoding parameter values calculated in the encoding process, thereby generating a bit stream. You can print The entropy encoding method is a method of receiving a symbol having various values and expressing it in a decodable column while removing statistical redundancy.

Here, the symbol means a syntax element, a coding parameter, a residual signal value, or the like that is to be encoded / decoded. Encoding parameters are parameters necessary for encoding and decoding, and may include information that may be inferred during encoding or decoding, as well as information encoded by an encoder and transmitted to a decoder, such as syntax elements. Means necessary information. Coding parameters may be, for example, intra / inter prediction modes, moving / motion vectors, reference picture indexes, coding block patterns, presence or absence of residual signals, transform coefficients, quantized transform coefficients, quantization parameters, block sizes, block partitioning information, or the like. May include statistics. In addition, the residual signal may mean a difference between the original signal and the prediction signal, and a signal in which the difference between the original signal and the prediction signal is transformed or a signal in which the difference between the original signal and the prediction signal is converted and quantized It 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, whereby the size of the bit string for the symbols to be encoded is increased. Can be reduced. Therefore, compression performance of image encoding may be increased through entropy encoding.

For entropy coding, coding methods such as exponential golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC) may be used. For example, the entropy encoder 150 may store a table for performing entropy encoding, such as a variable length coding (VLC) table, and the entropy encoder 150 may store the stored variable length encoding. Entropy encoding may be performed using the (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 a probability model. You may.

Here, binarization means expressing a symbol value as a binary sequence (bin sequence / string). A bin means the value of each binary number (0 or 1) when the symbol is represented as a column of binary numbers through binarization.

The probability model refers to a predicted probability of a symbol / bin to be encoded / decoded, which can be derived through a context information / context model. The context information / context model refers to information for determining a probability of a symbol / bin to be encoded / decoded.

More specifically, the CABAC entropy encoding method binarizes non-binarized symbols to transform them into bins, and uses the encoding information of neighboring and encoding target blocks or the information of symbols / bins encoded in the previous step to construct a context model. The bitstream may be generated by performing an arithmetic encoding of the bin by predicting the occurrence probability of the bin according to the determined context model. In this case, after determining the context model, the CABAC entropy encoding method may update the context model using information on the encoded symbol / bin for the context model of the next symbol / bin.

The quantized coefficients may be inversely quantized by the inverse quantizer 160 and inversely transformed by the inverse transformer 170. The inverse quantized and inverse transformed coefficients are added to the prediction block through the adder 175 and a reconstruction block can be generated.

The reconstruction block passes through the filter unit 180, and the filter unit 180 applies at least one or more of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstruction block or the reconstruction picture. can do. The reconstructed block that has passed through the filter unit 180 may be stored in the reference image buffer 190.

2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment. As described above with reference to FIG. 1, a scalable video encoding / decoding method or apparatus may be implemented by extension of a general video encoding / decoding method or apparatus that does not provide scalability, and the block diagram of FIG. 2 is scalable video decoding. An embodiment of an image decoding apparatus that may be the basis of an apparatus is shown.

2, the image decoding apparatus 200 may include an entropy decoder 210, an inverse quantizer 220, an inverse transformer 230, an intra predictor 240, a motion compensator 250, and a filter. 260 and a reference picture buffer 270.

The image decoding apparatus 200 may receive a bitstream output from the encoder and perform decoding in an intra mode or an inter mode, and output a reconstructed image, that is, a reconstructed image. In the intra mode, the switch may be switched to intra, and in the inter mode, the switch may be switched to inter. The image decoding apparatus 200 may generate a reconstructed block, that is, a reconstructed block by obtaining a residual block reconstructed from the received bitstream, generating a prediction block, and adding the reconstructed residual block and the prediction block.

The entropy decoder 210 may entropy decode the input bitstream according to a probability distribution to generate symbols including symbols in the form of quantized coefficients. The entropy decoding method is a method of generating each symbol by receiving a binary string. The entropy decoding method is similar to the entropy coding method described above.

More specifically, the CABAC entropy decoding method receives a bin corresponding to each syntax element in a bitstream, and decodes syntax element information, decoding information of neighboring and decoding target blocks, or information of a symbol / bin decoded in a previous step. A context model may be determined using the context model, and a probability corresponding to the value of each syntax element may be generated by performing arithmetic decoding of the bin by predicting a probability of occurrence of a bin according to the determined context model. In this case, after determining the context model, the CABAC entropy decoding method may update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin.

When the entropy decoding method 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, whereby the size of the bit string for each symbol is increased. Can be reduced. Therefore, the compression performance of image decoding can be improved through an entropy decoding method.

The quantized coefficients are inversely quantized by the inverse quantizer 220 and inversely transformed by the inverse transformer 230, and as a result of the inverse quantization / inverse transformation of the quantized coefficients, a reconstructed residual block may be generated.

In the intra mode, the intra predictor 240 may generate a predictive block by performing spatial prediction using pixel values of an already encoded block around the current block. In the inter mode, the motion compensator 250 may generate a prediction block by performing motion compensation using the motion vector and the reference image stored in the reference image buffer 270.

The reconstructed 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 or more of the deblocking filter, SAO, and ALF to the reconstructed block or the reconstructed picture. The filter unit 260 outputs a reconstructed image, that is, a reconstructed image. The reconstructed picture may be stored in the reference picture buffer 270 to be used for inter prediction.

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

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

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 may provide various scalability in terms of spatial, temporal, and image quality according to ambient conditions such as a transmission bit rate, a transmission error rate, and a system resource.

Scalable video coding may be performed using multiple layers structure 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 the image data using both the encoding information of the base layer and a general image encoding method. May include an enhancement layer for processing.

Here, the layer may be a set of images and bitstreams classified based on space (eg, image size), time (eg, encoding order, image output order), image quality, complexity, and the like. it means. In addition, the plurality of layers may have a dependency between each other.

Referring to FIG. 3, for example, the base layer may be defined as a QCIF (Quarter Common Intermediate Format), a frame rate of 15 Hz, a 3 Mbps bit rate, and the first enhancement layer may include a CIF (Common Intermediate Format), a frame rate of 30 Hz, It may be defined as a 0.7Mbps bit rate, the second enhancement layer may be defined as a standard definition (SD), a frame rate of 60Hz, 0.19Mbps bit rate. The format, frame rate, bit rate, etc. are exemplary and may be determined differently as necessary. In addition, the number of hierarchies used is not limited to this embodiment and may be determined differently according to a situation.

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

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

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 correspond to the target layer, the target image, the target slice, the target unit, the target block, the target symbol, and the target bin, respectively. Means image, slice, unit, block, symbol, and bin. The corresponding image refers to an image of another layer existing on the same time axis as the target image. When the display order of an image in another layer and an image in another layer are the same, it may be said that an image in the target layer and an image in another layer exist on the same time axis. Whether the pictures exist on the same time axis may be identified using an encoding parameter such as a picture order count (POC). The corresponding slice refers to a slice existing in a position corresponding to the same or similar to the target slice of the target image in the corresponding image. The corresponding unit refers to a unit existing in a corresponding position in the corresponding image that is spatially identical to or similar to the target unit of the target image. The corresponding block refers to a block existing at a position corresponding to the same as or similar to the target block of the target image in the corresponding image.

In addition, hereinafter, a slice indicating a unit in which an image is divided is used to mean a division unit such as a tile or an entropy slice. Independent image encoding and decoding are possible between the divided units.

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

In addition, scalable video coding has the same meaning as scalable video encoding from a coding point of view and scalable video decoding from a decoding point of view.

In the entropy encoding / decoding method used in a general image compression technique that does not provide scalability, context information of a target layer is used and context information of another layer available in a scalable video coding method is not utilized.

In the scalable video coding method, redundancy between layers may be removed by utilizing texture information, motion information, residual signal information, and the like between layers. However, after the encoding parameters, the final residual signal, etc. are obtained, entropy encoding / decoding may be performed independently in each layer. In this case, the scalable video coding method may have a limitation in improving encoding performance.

Therefore, in the scalable video coding method, when entropy encoding / decoding is performed on encoding / decoding target information (symbols such as encoding parameters and residual signals) of a target layer, context information of another layer as well as context information of the target layer are performed. Also used may be a method of use together. In this case, in performing the scalable video encoding / decoding method, since entropy encoding / decoding is performed using information between layers, compression performance of image encoding / decoding may be improved.

Referring to the embodiment of FIG. 4, the entropy encoder of the encoder derives context information of a symbol to be encoded (S410). As described above, the context information of the encoding target symbol may be derived using the context information in the target layer, or may be derived using the context information in the other layer.

The contextual information in the target layer or another layer may include a combination of frequencies and combinations of values and values of symbols and / or bins present in the target layer or other layers. Hereinafter, the value of the symbol / bin and the combination of values are collectively referred to as symbol / bin value information, and the combination of the frequency and the symbol frequency is referred to as symbol / bin frequency information. In addition, the value of the bin and the combination of values are collectively referred to as bin value information, and the combination of the frequency and the frequency of the bin collectively referred to as frequency information of the bin.

There may be various types of context information in a target layer or another layer, which is used for deriving context information of a symbol to be encoded.

As described above, the context information of the encoding target symbol may be derived using the context information in the target layer. As an embodiment of the context information in the target layer used to derive the context information of the symbol to be encoded, there may be the following types of context information.

1. The context information in the target layer may be the same as the encoding target symbol / bin and the value of the symbol / bin already encoded according to the encoding order in the target layer, and the frequency information.

2. The context information in the target layer may be a value or frequency information of a symbol / bin associated with or dependent on the encoding target symbol / bin and already encoded according to the encoding order in the target layer.

3. The context information in the target layer is a symbol / bin which is the same as the encoding target symbol / bin, and may be the value and frequency information of all symbols / bins existing in the image, slice, unit, or block of the target layer.

4. The context information in the target layer is a symbol / bin present in the encoding target slice, unit or block in the target layer, and may be the same symbol / bin value and frequency information as the encoding target symbol / bin. In this case, the slice, unit or block may be a slice, unit or block in which a specific encoding target symbol / bin exists.

5. The context information in the target layer is a symbol / bin present in the encoding target slice, unit or block in the target layer, which is the same as the encoding target symbol / bin and has a spatial position and a scanning position of an already encoded symbol / bin. Information. In this case, the slice, unit or block may be a slice, unit or block in which a specific encoding target symbol / bin exists.

6. The context information in the target layer may be a value and frequency information of a bin that is the same as the encoding target bin and is already encoded in a specific encoding target symbol existing in the target layer.

7. The context information in the target layer is a symbol / bin present in the neighboring unit of the encoding target unit or the neighboring block of the encoding target block in the target layer, and is equal to the encoding target symbol / bin and the value of the symbol / bin already encoded, It may be frequency information. In this case, the encoding target unit or the encoding target block may be a unit or block in which a specific encoding target symbol / bin exists.

The context information of the symbol to be encoded may be derived using context information in another layer. As an embodiment of context information in another layer used to derive context information of a symbol to be encoded, there may be the following context information types.

1. The context information in the other layer is the same symbol / bin as the symbol / bin to be encoded, and the value of the symbol / bin already encoded according to the coding order in the corresponding video, corresponding slice, corresponding unit or corresponding block of the other layer, It may be frequency information.

2. The context information in another layer is a symbol / bin associated with or dependent on a symbol / bin to be encoded, and a symbol / bin already encoded according to an encoding order in a corresponding video, corresponding slice, corresponding unit, or corresponding block of another layer. It may be a value of, frequency information.

3. The context information in the other layer is the same symbol / bin as the symbol / bin to be encoded, and may be the value of the corresponding symbol / bin in the corresponding layer, the corresponding slice, the corresponding unit or the block of another layer, and the frequency information. .

4. The context information in the other layer is the same symbol / bin as the symbol / bin to be encoded, and the spatial position and scanning of the symbol / bin already encoded in the corresponding image, corresponding slice, corresponding unit or corresponding block of another layer. ) May be location information.

5. The context information in the other layer may be a value and frequency information of a bin that is the same as the encoding target bin and is already encoded in the symbol existing in the corresponding image, the corresponding slice, the corresponding unit, or the corresponding block of the other layer. In this case, the symbol may be the same symbol as a specific encoding target symbol.

6. The context information in the other layer is a symbol / bin present in the neighbor slice of the corresponding slice, the neighbor unit of the corresponding unit, or the neighboring block of the corresponding block in another layer, and is the same symbol as the encoding target symbol / bin and already encoded / The value of the bin may be frequency information. In this case, the corresponding slice, the corresponding unit, or the corresponding block may be a slice, a unit, or a block in which the same symbol / bin as a specific encoding target symbol / bin exists.

7. The context information in another layer may be context information used for encoding processing of a corresponding video, corresponding slice, corresponding unit, or corresponding block of another layer. That is, the context information for the encoding target symbol / bin in the target layer may be initialized using the context information of the corresponding image, the corresponding slice, the corresponding unit, or the corresponding block of another layer.

8. The context information in another layer may be context information used for encoding processing of a corresponding video, corresponding slice, corresponding unit, or corresponding block of another layer. That is, the context information about the encoding target symbol / bin in the target layer may be initialized using the context information of the encoded symbol / bin in another layer.

The entropy encoder of the encoder may derive the context information of the encoding target symbol by using at least one of the above-described context information in the target layer and context information in the other layer.

Referring back to the embodiment of FIG. 4, the entropy encoder of the encoder entropy encodes a symbol to be encoded using the derived context information (S420).

According to an embodiment of the present invention, since scalable context encoding information may be used to perform entropy encoding in a target layer, a probability characteristic of a symbol / bin to be encoded may be predicted more accurately. Therefore, compression performance of video or video encoding may be improved.

The encoder may use an explicit method to inform the decoder of which layer of context information in the target layer and context information in another layer is used. Also, an implicit method may be used so that the information obtained in the encoder can be obtained in the same way in the decoder.

When an explicit method is used, in one embodiment, the encoder generates and transmits a flag including information indicating whether to use context information in the target layer and / or information indicating whether to use context information in another layer. And / or store. In this case, the decoder may receive and / or store the flag from the encoder. The decoder may use the flag to derive information about whether context information in the target layer is used and / or information about whether context information in another layer is used.

When contextual information in another layer is used in an explicit method, in one embodiment the encoder may generate, send and / or store a flag indicating whether one of the other layers uses contextual information. In this case, the decoder may receive and / or store the flag from the encoder. The decoder may derive information on which of the other layer context information is used using the flag.

When an implicit method is used, according to an embodiment, the encoder and the decoder may use the same method to derive information about which layer's context information is used according to encoding parameter values of the target layer and another layer. At this time, the context information derivation method used by the encoder and the decoder in the same manner may be determined between the encoder and the decoder in advance.

Referring to FIG. 5, the encoder detects whether there is context information available in a target layer with respect to a symbol or a string of symbols to be encoded (S510). The encoder determines whether there is context information available in the target layer according to the search result (S520).

If there is context information available in the target layer, the encoder derives context information of the target layer (S530). There may be various types of context information in the target layer, and embodiments of the context information available in the target layer have been described above with reference to FIG. 4. Thus, the contextual information derived from the encoder may be of the type described above in the embodiment of FIG. 4 or some other type.

If there is no context information available in the target layer, the encoder searches for available context information of another layer (S540).

If there is context information available in another layer, the encoder derives context information of another layer (S550). There may be various types of context information in other layers, and embodiments of the context information available in other layers have been described above with reference to FIG. 4. Thus, the contextual information derived from the encoder may be of the type described above in the embodiment of FIG. 4 or some other type.

The encoder performs entropy encoding on the symbol to be encoded using the derived context information (S560). The encoder may generate a bitstream by performing entropy encoding.

The encoder may inform the decoder of information on whether there is context information available for the target layer and / or another layer according to the search and determination result. In addition, the encoder may inform the decoder of information of which layer among other layers is used. The above information may be obtained equally in the encoder and the decoder by an implicit method.

According to the embodiment of FIG. 5, context information of another layer may be used to perform entropy encoding in a target layer in a scalable video encoding process. Therefore, the probability characteristic of the symbol / bin to be encoded can be predicted more accurately, and the compression performance of video or video encoding can be improved.

Referring to the embodiment of FIG. 6, the encoder derives context information of a symbol to be encoded (S610). The context information of the symbol to be encoded may be derived using context information in the target layer, or may be derived using context information in another layer. In addition, context information in the target layer and other layers may have various types as described above in the embodiment of FIG. 4.

The encoder derives the probability model of the symbol / bin to be encoded using the derived context information (S620). Since the derived context information may also be derived from context information of another layer, the probability model of the symbol / bin to be encoded may be derived using context information of another layer as well as the target layer.

The encoder performs entropy encoding on the symbol / bin to be encoded using the derived probability model (S630).

Referring to the embodiment of FIG. 7, the encoder derives context information of a symbol to be encoded (S710). The context information of the symbol to be encoded may be derived using context information in the target layer, or may be derived using context information in another layer. In addition, context information in the target layer and other layers may have various types as described above in the embodiment of FIG. 4.

The encoder derives the binarization method of the encoding target symbol by using the derived context information (S720). Since the derived context information may also be derived using context information of another layer, the binarization method of an encoding target symbol may be derived using context information of another layer as well as the target layer.

The encoder performs entropy encoding on the symbol to be encoded using the derived binarization method (S730).

Referring to the embodiment of FIG. 8, the encoder derives context information of a symbol to be encoded (S810). The context information of the symbol to be encoded may be derived using context information in the target layer, or may be derived using context information in another layer. In addition, context information in the target layer and other layers may have various types as described above in the embodiment of FIG. 4.

The encoder derives the VLC table of the symbol to be encoded using the derived context information (S820). Since the derived context information may also be derived by context information of another layer, the VLC table of the symbol to be encoded may be derived using context information of another layer as well as the target layer.

The encoder performs entropy encoding on the symbol to be encoded using the derived VLC table (S830).

6 to 8, since context information of another layer may be used for entropy encoding, a probability characteristic of an encoding target symbol / bin may be more accurately reflected. Therefore, entropy encoding performance and image compression efficiency can be improved.

Referring to the embodiment of FIG. 9, the entropy decoding unit of the decoder derives context information of a decoding target symbol (S910). As described above, the context information of the decoding object symbol may be derived using the context information in the target layer, or may be derived using the context information in the other layer.

There may be various types of context information in a target layer or another layer, which is used for deriving context information of a decoding target symbol.

The context information of the decoding target symbol may be derived using the context information in the target layer. As an embodiment of the context information in the target layer used to derive the context information of the decoding target symbol, there may be the following context information types.

1. The context information in the target layer may be the same as the decoding target symbol / bin and the value and frequency information of the symbol / bin already decoded according to the decoding order in the target layer.

2. The context information in the target layer may be a value or frequency information of a symbol / bin associated with or dependent on the decoding target symbol / bin and already decoded according to the decoding order in the target layer.

3. The context information in the target layer is a symbol / bin which is the same as the decoding target symbol / bin, and may be a value and frequency information of all symbols / bins existing in the image, slice, unit, or block of the target layer.

4. The context information in the target layer is a symbol / bin present in the decoding target slice, unit, or block in the target layer, and may be the same as the decoding target symbol / bin and the value of the already decoded symbol / bin, frequency information. In this case, the slice, unit or block may be a slice, unit or block in which a specific decoding target symbol / bin exists.

5. The context information in the target layer is a symbol / bin present in the decoding target slice, unit or block in the target layer, which is the same as the decoding target symbol / bin and the spatial position and scanning position of the already decoded symbol / bin. Information. In this case, the slice, unit or block may be a slice, unit or block in which a specific decoding target symbol / bin exists.

6. The context information in the target layer may be a value and frequency information of a bin that is the same as the decoding target bin and is already decoded in a specific decoding target symbol existing in the target layer.

7. The context information in the target layer is a symbol / bin present in the neighboring unit of the decoding target unit or the neighboring block of the decoding target block in the target layer, and is equal to the decoding target symbol / bin and the value of the symbol / bin already decoded, It may be frequency information. In this case, the decoding object unit or the decoding object block may be a unit or block in which a specific decoding object symbol / bin exists.

The context information of the decoding target symbol may be derived using context information in another layer. As an embodiment of the context information in another layer used to derive the context information of the decoding target symbol, there may be the following context information types.

1. The context information in the other layer is the same symbol / bin as the decoding target symbol / bin, and the value of the symbol / bin already decoded in the decoding order in the corresponding video, corresponding slice, corresponding unit or corresponding block of another layer, It may be frequency information.

2. The context information in the other layer is a symbol / bin associated with or dependent on the decoding target symbol / bin, and the symbol / bin already decoded in the decoding order in the corresponding image, the corresponding slice, the corresponding unit or the corresponding block of the other layer. It may be a value of, frequency information.

3. The context information in the other layer is the same symbol / bin as the decoding target symbol / bin, and may be the value of the corresponding symbol / bin in the other layer, the corresponding slice, the corresponding unit or the corresponding block, or the frequency information of the other layer. .

4. The context information in the other layer is the same symbol / bin as the decoding target symbol / bin, and the spatial position and scanning of the symbol / bin already decoded in the corresponding image, the corresponding slice, the corresponding unit or the corresponding block of the other layer. ) May be location information.

5. The context information in another layer may be a value and frequency information of a bin that is the same as a decoding target bin and is already decoded in a symbol existing in a corresponding image, corresponding slice, corresponding unit, or corresponding block of another layer. In this case, the symbol may be the same symbol as a specific decoding target symbol.

6. The context information in the other layer is a symbol / bin present in the neighbor slice of the corresponding slice, the neighbor unit of the corresponding unit, or the neighboring block of the corresponding block in another layer, and is the same symbol as the decoding target symbol / bin and already decoded symbol / The value of the bin may be frequency information. In this case, the corresponding slice, the corresponding unit, or the corresponding block may be a slice, a unit, or a block in which the same symbol / bin as a specific decoding target symbol / bin exists.

7. The context information in another layer may be context information used for decoding processing of a corresponding video, corresponding slice, corresponding unit, or corresponding block of another layer. That is, the context information about the decoding target symbol / bin in the target layer may be initialized using the context information of the corresponding image, the corresponding slice, the corresponding unit, or the corresponding block of another layer.

8. The context information in the other layer may be context information used for decoding processing of the corresponding video, the corresponding slice, the corresponding unit, or the corresponding block of the other layer. That is, the context information for the decoding target symbol / bin in the target layer may be initialized using the context information of the decoded symbol / bin in another layer.

The entropy decoding unit of the decoder may derive the context information of the decoding target symbol by using at least one of the above-described context information in the target layer and context information in the other layer.

Referring back to the embodiment of FIG. 9, the entropy decoding unit of the decoder performs entropy decoding on the decoding target symbol by using the derived context information (S920).

According to an embodiment of the present invention, since scalable information may be used to perform entropy decoding in a target layer in scalable video decoding, a probability characteristic of a symbol / bin to be decoded may be more accurately predicted. Therefore, the compression performance of the image or video decoding can be improved.

The decoder may receive from the encoder information about which layer of context information in the target layer and context information in another layer is used by an explicit method, or may derive the information by an implicit method. have.

As described above in the embodiment of FIG. 4, when the explicit method is used, the decoder includes a flag including information indicating whether to use context information in the target layer and / or information indicating whether to use context information in another layer ( flag). The decoder may also receive a flag indicating whether any of the other layers uses context information. In this case, the decoder may obtain information about which layer context information is used by using the flag.

When an implicit method is used, according to an embodiment, the encoder and the decoder may use the same method to derive information about which layer's context information is used according to encoding parameter values of the target layer and another layer.

Referring to FIG. 10, the decoder receives a bitstream and searches whether there is context information available in a target layer for a decoding target symbol (S1010). The decoder determines whether there is context information available in the target layer according to the search result (S1020). In this case, the decoder may search for and determine whether there is context information in the target layer through flag information transmitted from the encoder. Also, the decoder may search for and determine whether there is context information in the target layer by using the same method as the encoder according to the encoding parameter value.

If there is context information available in the target layer, the decoder derives context information of the target layer (S1030). There may be various types of context information in the target layer, and embodiments of the context information available in the target layer have been described above with reference to FIG. 9. Thus, the contextual information derived from the decoder may be of the type described above in the embodiment of FIG. 9 or some other type.

If there is no context information available in the target layer, the decoder searches for available context information of another layer (S1040). In this case, the decoder may search for and determine whether there is context information in another layer through flag information transmitted from the encoder. The decoder may also search for and determine whether there is context information in another layer using the same method as the encoder according to the encoding parameter value.

If there is context information available in another layer, the decoder derives context information of another layer (S1050). There may be various types of context information in other layers, and embodiments of the context information available in other layers have been described above with reference to FIG. 9. Thus, the contextual information derived from the decoder may be of the type described above in the embodiment of FIG. 9 or some other type.

The decoder performs entropy decoding on the decoding object symbol by using the derived context information (S1060). The decoder may generate a symbol or a sequence of symbols by performing entropy decoding.

According to the embodiment of FIG. 10, context information of another layer may be used to perform entropy decoding in a target layer in a scalable video decoding process. Therefore, the probability characteristic of the decoding target symbol / bin can be predicted more accurately, and the performance of video or video decoding can be improved.

Referring to the embodiment of FIG. 11, the decoder derives context information of a decoding target symbol (S1110). The context information of the decoding target symbol may be derived using context information in the target layer, or may be derived using context information in another layer. In addition, context information in the target layer and other layers may have various types as described above in the embodiment of FIG. 9.

The decoder derives a probability model of the symbol / bin to be decoded using the derived context information (S1120). Since the derived context information may also be derived from context information of another layer, the probability model of the symbol / bin to be decoded may be derived using context information of another layer as well as the target layer.

The decoder performs entropy decoding on the symbol / bin to be decoded using the derived probability model (S1130).

Referring to the embodiment of FIG. 12, the decoder derives context information of a decoding target symbol (S1210). The context information of the decoding target symbol may be derived using context information in the target layer, or may be derived using context information in another layer. In addition, context information in the target layer and other layers may have various types as described above in the embodiment of FIG. 9.

The decoder derives the binarization method of the decoding object symbol by using the derived context information (S1220). Since the derived context information may also be derived by context information of another layer, the binarization method of the decoding target symbol may be derived using context information of another layer as well as the target layer.

The decoder performs entropy decoding on the decoding object symbol by using the derived binarization method (S1230).

Referring to the embodiment of FIG. 13, the decoder derives context information of a decoding target symbol (S1310). The context information of the decoding target symbol may be derived using context information in the target layer, or may be derived using context information in another layer. In addition, context information in the target layer and other layers may have various types as described above in the embodiment of FIG. 9.

The decoder derives the VLC table of the symbol to be decoded using the derived context information (S1320). Since the derived context information may also be derived by context information of another layer, the VLC table of the decoding target symbol may be derived using context information of another layer as well as the target layer.

The decoder performs entropy decoding on the symbol to be decoded using the derived VLC table (S1330).

11 to 13, since context information of another layer may be used for entropy decoding, a probability characteristic of a symbol / bin to be decoded may be more accurately reflected. Therefore, entropy decoding performance and image compression efficiency can be improved.

In the above-described embodiment, the methods are described based on a flowchart as a series of steps or blocks, but the present invention is not limited to the order of steps, and any steps may occur in a different order or at the same time than the other steps described above. have. Also, one of ordinary skill in the art appreciates that the steps shown in the flowcharts are not exclusive, that other steps may be included, or that one or more steps in the flowcharts may be deleted without affecting the scope of the present invention. I can understand.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Claims

An entropy decoding method for multi-layer scalable video decoding,
Deriving context information of a symbol to be decoded using at least one of context information of a target layer and context information of another layer; And
Performing entropy decoding on the decoding object symbol by using the derived context information,
The target layer is a layer including the decoding target symbol, and the other layer is a layer excluding the target layer and may be used for decoding in the target layer.