KR20140073430A - Method and apparatus for image encoding/decoding - Google Patents

Method and apparatus for image encoding/decoding Download PDF

Info

Publication number
KR20140073430A
KR20140073430A KR1020130149063A KR20130149063A KR20140073430A KR 20140073430 A KR20140073430 A KR 20140073430A KR 1020130149063 A KR1020130149063 A KR 1020130149063A KR 20130149063 A KR20130149063 A KR 20130149063A KR 20140073430 A KR20140073430 A KR 20140073430A
Authority
KR
South Korea
Prior art keywords
block
current block
scanning
decoded
mode
Prior art date
Application number
KR1020130149063A
Other languages
Korean (ko)
Inventor
이진호
강정원
이하현
최진수
김진웅
Original Assignee
한국전자통신연구원
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 한국전자통신연구원 filed Critical 한국전자통신연구원
Publication of KR20140073430A publication Critical patent/KR20140073430A/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/187—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a scalable video layer
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding

Abstract

Disclosed are a method and an apparatus for encoding/decoding a video, capable of supporting a plurality of layers. The method of decoding the video comprises the steps of: performing a scanning operation by selecting a scanning mode for a decoding target block at an upper layer; performing an inter-layer prediction operation for the decoding target block using information of a corresponding block at a lower layer corresponding to the decoding target block; and creating restore sample values using prediction sample values of the decoding target block created through the inter-layer prediction operation and residual values of the decoding target block.

Description

METHOD AND APPARATUS FOR IMAGE ENCODING / DECODING [0002]

The present invention relates to image encoding and decoding, and more particularly, to image encoding and decoding based on scalable video coding (SVC).

Recently, as a multimedia environment has been established, a variety of terminals and networks have been used, and user demands have been diversified accordingly.

For example, as the performance and computing capability of a terminal are diversified, the performance to be supported varies depending on a device. In addition, the network in which the information is transmitted is also diversified not only by the external structure such as a wired / wireless network, but also by the type of information to be transmitted, information amount and speed, and the like. The user selects the terminal and the network to be used according to the desired function, and the spectrum of the terminal and the network provided by the enterprise to the user is also diversified.

In this regard, recently, broadcasting having a high definition (HD) resolution has been expanded not only in the domestic market but also in the world, so that many users are accustomed to high resolution and high quality video. Accordingly, many video service related organizations are making efforts to develop next generation video equipment.

In addition, with the increasing interest in UHD (Ultra High Definition), which has a resolution more than four times that of HDTV in addition to HDTV, there is a growing demand for a technology for compressing and processing higher resolution and higher quality images.

An inter prediction technique for predicting a pixel value included in a current picture from a previous and / or a temporal picture in order to compress and process an image, an inter prediction technique for predicting a pixel value included in a current picture, An entropy encoding technique for assigning a short code to a symbol having a high appearance frequency and a long code to a symbol having a low appearance frequency can be used.

As described above, considering the requirements of each terminal, network, and diversified user with different functions to be supported, the quality, size, and frame of a supported image need to be diversified accordingly.

As described above, scalability that supports various image quality, resolution, size, frame rate, etc. due to heterogeneous communication networks and various functions and types of terminals 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, and image quality in order to provide a service required by a user in various environments based on a highly efficient video encoding method.

The present invention provides an image encoding / decoding method and apparatus capable of improving encoding / decoding efficiency.

The present invention provides an inter-layer prediction method and apparatus in scalable video coding capable of improving coding / decoding efficiency.

The present invention provides a method and apparatus for inter-layer image coding / decoding using adaptive scanning in scalable video coding capable of improving coding / decoding efficiency.

According to an embodiment of the present invention, an image decoding method supporting a plurality of layers is provided. The method comprising the steps of: selecting a scanning mode for a current block to be decoded in an upper layer and scanning the block; performing a scanning operation on the block to be decoded using information on a corresponding block in a lower layer corresponding to the current block; And generating a reconstructed sample value using the predictive sample value of the to-be-decoded block generated by the inter-layer prediction and the residual value of the to-be-decoded block.

Wherein the step of performing the scanning further comprises a step of performing an intra prediction based on the intra prediction mode or the scanning mode for at least one of the reconstructed block around the current block to be decoded, the reconstructed block around the current block to be decoded, The scanning mode of the block to be decoded can be selected.

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 scanning unit for performing scanning by selecting a scanning mode for a current block to be decoded of an upper layer, a scanning unit for performing scanning on the decoding target block using information on a corresponding block of a lower layer corresponding to the decoding target block, And a prediction unit for generating a reconstructed sample value using the predictive sample value of the current block to be decoded generated by the inter-layer prediction and the residual value of the current block to be decoded.

Wherein the scanning unit is configured to perform an intra prediction mode or a scanning mode for at least one of a block to be decoded, a reconstruction block around the to-be-decoded block, and a reconstruction block around the corresponding block and the corresponding block, Can be selected.

According to another embodiment of the present invention, an image encoding method supporting a plurality of layers is provided. The image encoding method includes the steps of performing inter-layer prediction on the current block using information on a corresponding block of a lower layer corresponding to a current block to be coded of an upper layer, Generating a residual value of the current block to be coded based on a predicted sample value of the block and selecting a scanning mode for the coefficients of the current block to be coded obtained through at least one of transforming and quantizing the residual value And performing a scanning operation.

Wherein the step of performing the scanning step comprises a step of performing a scanning process based on an intra prediction mode or a scanning mode for at least one of a current block, a restoration block around the current block, a corresponding block, and a restoration block around the corresponding block, The scanning mode of the current block can be selected.

According to another embodiment of the present invention, an image encoding apparatus supporting a plurality of layers is provided. Wherein the image encoding apparatus comprises: a prediction unit that performs inter-layer prediction on the current block using information on a corresponding block of a lower layer corresponding to a current block to be coded of an upper layer; A residual value generating unit for generating a residual value of the current block based on a predicted sample value of the current block and a coefficient generating unit for generating a residual value of the current block using the coefficients of the current block obtained through at least one of transforming and quantizing the residual value And a scanning unit for performing scanning by selecting a scanning mode for the scanning unit.

Wherein the scanning unit scans the current block to be coded based on an intra prediction mode or a scanning mode for at least one of a current block, a restoration block around the current block, a corresponding block, and a restoration block around the corresponding block, Can be selected.

When scalable video coding is performed for an upper layer, it is possible to perform inter-layer prediction using samples or parameters of a lower layer. Entropy coding can be performed on a quantized coefficient (or a transform coefficient) obtained through transformation or quantization after generating a residual using the prediction value of the upper layer obtained through inter-layer prediction. At this time, by applying the scanning mode adaptively selected using the coding parameters of the upper or lower layer to the quantized coefficients, the coding efficiency can be improved in entropy coding. In addition, the decoding efficiency can be improved by applying the scanning mode adaptively to the parsed coefficients in the same manner.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention.
3 is a conceptual diagram schematically showing an example of a scalable video coding structure using a plurality of layers to which the present invention can be applied.
4 is a diagram for explaining a scanning method according to a scanning mode (scanning order) to which the present invention can be applied.
5 is a diagram showing an example of the intra prediction mode.
6 is a flowchart schematically illustrating an image encoding method using adaptive scanning according to an embodiment of the present invention.
7 is a diagram illustrating an inter-layer prediction method according to an embodiment of the present invention.
8 is a flowchart schematically illustrating a method of decoding an image using adaptive scanning according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In describing the embodiments of the present invention, if the detailed description of related known structures or functions is deemed to obscure the subject matter of the present specification, the description may be omitted.

When an element is referred to herein as being "connected" or "connected" to another element, it may mean directly connected or connected to the other element, Element may be present. In addition, the content of " including " a specific configuration in this specification does not exclude a configuration other than the configuration, and means that additional configurations can be included in the scope of the present invention or the scope of the present invention.

The terms first, second, etc. may be used to describe various configurations, but the configurations are not limited by the term. The terms are used for the purpose of distinguishing one configuration from another. For example, without departing from the scope of the present invention, the first configuration may be referred to as the second configuration, and similarly, the second configuration may be named as the first configuration.

In addition, the constituent elements shown in the embodiments of the present invention are shown independently to represent different characteristic functions, which do not mean that each constituent element is composed of separate hardware or a single software constituent unit. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of each constituent unit may form one constituent unit or one constituent unit may be divided into a plurality of constituent units to perform a function. The integrated embodiments and the separate embodiments of each component are also included in the scope of the present invention unless they depart from the essence of the present invention.

In addition, some of the components are not essential components to perform essential functions in the present invention, but may be optional components only to improve performance. The present invention can be implemented only with components essential for realizing the essence of the present invention, except for the components used for the performance improvement, and can be implemented by only including the essential components except the optional components used for performance improvement Are 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 of the present invention.

A scalable video encoding / decoding method or apparatus may be implemented by a general image encoding / decoding method or apparatus extension that does not provide scalability, and the block diagram of FIG. 1 shows an embodiment of a video encoding apparatus that can be a basis of a good video encoding apparatus.

1, the image encoding apparatus 100 includes a motion prediction unit 111, a motion compensation unit 112, an intra prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, A quantization unit 140, an entropy encoding unit 150, an inverse quantization unit 160, an inverse transformation 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 bit stream. In the intra mode, the switch 115 is switched to the intra mode, and in the inter mode, the switch 115 can be switched to the inter mode. Intra prediction is intra prediction, and inter prediction is inter prediction. The image encoding apparatus 100 may generate a prediction block for an input block of an input image, and then may code a residual between the input block and the prediction block. At this time, the input image may mean an original picture.

In the intra mode, the intraprediction unit 120 may generate a prediction block by performing spatial prediction using the pixel values of the already coded / decoded blocks around the current block.

In the inter mode, the motion predicting unit 111 can obtain a motion vector by searching an area of the reference picture stored in the reference picture buffer 190 that is best matched with the input block. The motion compensation unit 112 may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector is a two-dimensional vector used for inter prediction, and can represent an offset between the current image to be encoded / decoded and the reference image.

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

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

The quantization unit 140 may quantize the input transform coefficient according to a quantization parameter (or a quantization parameter) to output a quantized coefficient. The quantized coefficients may be referred to as quantized transform coefficient levels. At this time, the quantization unit 140 can quantize the input transform coefficients using the quantization matrix.

The entropy encoding unit 150 may perform entropy encoding based on the values calculated by the quantization unit 140 or the encoding parameter values calculated in the encoding process to output a bitstream. 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, thereby expressing symbols, The size of the column can be reduced. Therefore, the compression performance of the image encoding can be enhanced through the entropy encoding. The entropy encoding unit 150 may use an encoding method such as Exponential-Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) for entropy encoding.

Since the image encoding apparatus 100 according to the embodiment of FIG. 1 performs inter-prediction encoding, that is, inter-view prediction encoding, the currently encoded image needs to be decoded and stored for use as a reference image. Accordingly, the quantized coefficients are inversely quantized in the inverse quantization unit 160 and inversely transformed in the inverse transformation unit 170. The inverse quantized and inverse transformed coefficients are added to the prediction block through the adder 175 and a reconstructed block is generated.

The restoration block passes through the filter unit 180 and the filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) can do. The filter unit 180 may be referred to as an adaptive in-loop filter. The deblocking filter can remove block distortion occurring at the boundary between the blocks. The SAO may add a proper offset value to the pixel value to compensate for coding errors. ALF can perform filtering based on the comparison between the reconstructed image and the original image. The reconstruction block having passed through the filter unit 180 can be stored in the reference picture buffer 190.

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

As described above with reference to FIG. 1, the scalable video encoding / decoding method or apparatus can be implemented by expanding a general image encoding / decoding method or apparatus that does not provide scalability, and the block diagram of FIG. 2 shows a scalable 1 shows an embodiment of an image decoding apparatus which can be a basis of a video decoding apparatus.

2, the image decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, a motion compensation unit 250, an adder 255 A filter unit 260, and a reference picture buffer 270.

The video decoding apparatus 200 receives the bit stream output from the encoder and decodes the video stream into the intra mode or the inter mode, and outputs the reconstructed video, that is, the reconstructed video. In the intra mode, the switch is switched to the intra mode, and in the inter mode, the switch can be switched to the inter mode.

The image decoding apparatus 200 may obtain a reconstructed residual block from the input bitstream, generate a prediction block, and add the reconstructed residual block and the prediction block to generate a reconstructed block, i.e., a reconstructed block .

The entropy decoding unit 210 may entropy-decode the input bitstream according to a probability distribution to generate symbols including a symbol of a quantized coefficient type.

When the entropy decoding method is applied, a small number of bits are assigned to a symbol having a high probability of occurrence, and a large number of bits are assigned to a symbol having a low probability of occurrence, so that the size of a bit string for each symbol is Can be reduced.

The quantized coefficients are inversely quantized in the inverse quantization unit 220 and inversely transformed in the inverse transformation unit 230. The reconstructed residual block can be generated as a result of inverse quantization / inverse transformation of the quantized coefficients. At this time, the inverse quantization unit 220 can apply the quantization matrix to the quantized coefficients.

In the intra mode, the intraprediction unit 240 may generate a prediction block by performing spatial prediction using the pixel value of the already decoded block around the current block. In the inter mode, the motion compensation unit 250 may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference picture buffer 270. [

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

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

In order to transmit video data, a transmission medium is required, and the performance of the transmission medium varies depending on various network environments. A scalable video coding method may be provided for application to these 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 utilizing texture information, motion information, residual signals, etc. between layers Thereby improving the encoding and decoding performance. The scalable video coding method can provide a variety of scalability in terms of spatial, temporal, picture quality (or quality, quality) depending on the surrounding conditions such as transmission bit rate, transmission error rate, have.

Scalable video coding can 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 for compressing and processing image data using a general image decoding method, and compressing and compressing the image data using the decoding information of the base layer and a general image decoding method. Lt; RTI ID = 0.0 > layer. ≪ / RTI >

Here, the layer may be classified into a video and a bit classified based on spatial (e.g., image size), temporal (e.g., decoding order, video output order, frame rate), image quality, Means a set of bitstreams.

The base layer may be referred to as a base layer or may be referred to as 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 lower scalability than the specific layer, and the upper layer may mean a layer supporting higher scalability than a specific layer. A layer that a particular layer refers to in encoding or decoding may be referred to as a reference layer.

Referring to FIG. 3, for example, the base layer may be defined by a standard definition (SD), a frame rate of 15 Hz, a bit rate of 1 Mbps, and a first enhancement layer may be defined as high definition (HD), a frame rate of 30 Hz, 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, the frame rate, the bit rate, and the like are one example, and can be determined as needed. Also, the number of layers to be used is not limited to the present embodiment, but can be otherwise determined depending on the situation. For example, if the transmission bandwidth is 4 Mbps, the frame rate of the first enhancement layer HD may be reduced to 15 Hz or less.

The scalable video coding method can provide temporal, spatial, and image quality scalability by the method described in the embodiment of FIG.

In this specification, scalable video coding has the same meaning as scalable video encoding in terms of encoding and scalable video decoding in decoding.

On the other hand, as described above, the sub-decoder performs intra-picture prediction (hereinafter referred to as intra prediction) or inter-picture prediction (inter prediction) on the sub-picture to be decoded when the sub- can do.

In this case, the block to be decoded may be a square block of NxN size or a rectangular block of NxM size, and N or M may have a value of 4, 8, 16, 32, The block to be coded / decoded includes a coding block (CB), a prediction block (PB), a prediction block (PU) or a prediction unit (PU) (TB: Transform Block, or TU: Transform Unit).

The encoder can generate a residual value which is a difference between a value predicted through intra prediction or inter prediction for the current block and the original value of the current block. The encoder may encode the residual value by transforming and quantizing the residual value.

The decoder can generate a residual value by decoding the coefficients encoded by the encoder, and de-quantizing and inverse transforming the coefficients. The decoder may generate a reconstructed sample for the current block by adding the residual value and a predicted value through intra prediction or inter prediction.

When a transform skip is applied in the subdecryption, the subdecoder can skip the conversion process. At this time, flag information (e.g., transform_skip_flag) may be used as to whether to apply the conversion skip. When the value of the transform_skip_flag is 1, it indicates that the conversion skip is applied. When the value of the transform_skip_flag is 0, it indicates that the conversion skip is not applied.

In the adder / decoder, it is possible to perform scanning with respect to at least one of a residual value or a transform coefficient obtained through conversion, a quantized coefficient obtained through quantization, and an entropy added / decoded coefficient.

At this time, the scanning may be performed by applying a scanning mode (scanning order) adaptively selected according to the coding parameters. The scanning mode (scan order) may include an up-right diagonal scan order, a horizontal scan order, and a vertical scan order. The scanning mode may be specified by a scan index (scanIdx). For example, if the scan index is 0, the scan direction is the upward diagonal scan. If the scan index is 1, the horizontal scan order is indicated. If the scan index is 2, the vertical scan order can be displayed.

The coding parameters include a coding mode (e.g., an intra picture coding mode or an inter picture coding mode), an intra prediction mode, an inter prediction mode, a scanning mode (scan index), a block size, a quantization parameter (QP) Flag) or the like.

4 is a diagram for explaining a scanning method according to a scanning mode (scanning order) to which the present invention can be applied.

In the example of FIG. 4, the block size is 4x4 for convenience of explanation, and the scan order shown in FIG. 4 can be applied to the block having any size as well.

4 (a) shows a method of scanning by applying a right-upward diagonal scanning order to a 4x4 block. The rightward diagonal scanning order refers to scanning from 0 to 15 in order as shown in FIG. 4 (a). The rightward diagonal scan order may be a scanning mode when the scan index value is zero.

For example, when a rightward diagonal scanning order is applied, the encoder scans quantized coefficients arranged in a 4x4 size two-dimensional array according to a right-upward diagonal scanning order as shown in FIG. 4 (a) And rearrange them into quantized coefficients of a one-dimensional array. In the decoder, the quantized coefficients of the one-dimensional array are sequentially read out, and can be rearranged into a 4-by-4 size two-dimensional array according to a right-upward diagonal scanning order as shown in (a) of FIG.

4 (b) shows a method of scanning a 4x4 block by applying a horizontal scanning order. The horizontal scanning order refers to scanning from 0 to 15 in order as shown in FIG. 4 (b). The horizontal scan order may be a scanning mode when the scan index value is 1.

For example, when the horizontal scanning order is applied, the encoder scans the quantized coefficients arranged in a 2-dimensional array of 4x4 size according to the horizontal scanning order as shown in FIG. 4 (b) Can be rearranged into quantized coefficients of a one-dimensional array. In the decoder, the quantized coefficients of the one-dimensional array are sequentially read out and rearranged into a 2-dimensional array of 4x4 size according to the horizontal scanning order as shown in FIG. 4 (b).

4 (c) shows a method of scanning a 4x4 block by applying a vertical scanning order. The vertical scanning order refers to scanning from 0 to 15 in order as shown in FIG. 4 (c). The vertical scanning order may be a scanning mode when the scan index value is 2.

For example, when the vertical scanning order is applied, the encoder scans quantized coefficients arranged in a two-dimensional array of 4x4 size according to the vertical scanning order as shown in FIG. 4C Can be rearranged into quantized coefficients of a one-dimensional array. In the decoder, the quantized coefficients of the one-dimensional array are sequentially read out and rearranged into a 4-by-4 size two-dimensional array according to the vertical scanning order as shown in FIG. 4 (c).

The scanning may be performed in the reverse order of the upward diagonal scanning order, the horizontal scanning order, and the vertical scanning order. 4 (a), 4 (b), and 4 (c), scanning can be performed in reverse order from 15 to 0. In other words, the scanning can be performed in a scanning order from a specific scanning position in which quantized coefficients are present in reverse order. For example, when the specific scanning position is 11 and the scan index is 0, scanning can be performed in reverse order from 11 to 0 according to the right-up scan order shown in FIG. The specific scanning position can be determined by the encoder and transmitted to the decoder.

In the above-described FIG. 4, a quantization coefficient is used as an example of the scanning method, but this is merely an example, and the present invention is not limited thereto. The scanning method of FIG. 4 can be applied not only to quantized coefficients, but also to residual, transform coefficients, entropy-added / decoded coefficients, and the like.

For the sake of convenience, the adaptive scanning method will be described with reference to a quantized coefficient. However, the present invention is not limited thereto. The present invention can also be applied to residual, transform coefficient, and entropy coding / decoding coefficient.

As described above, the scanning mode can be adaptively selected according to the encoding parameters.

For example, if the encoding mode is the inter-picture encoding mode, a right-upward diagonal scan order may be applied to the quantized coefficients.

If the coding mode is the intra picture coding mode, the scanning mode is adaptively selected and applied to the quantized coefficients according to the coding parameters such as the size of the block to be scanned (for example, the transform block), the intra prediction mode, can do.

At this time, for the luma component, the scanning mode can be adaptively selected when the size of the block to be scanned is 4x4 or 8x8, and when the size of the block to be scanned is 4x4 for the chroma component, The scanning mode can be selected. In this case, the scanning mode can be adaptively selected according to the intra prediction mode of the scanning target block, as shown in FIG.

5 is a diagram showing an example of the intra prediction mode. Different intra mode prediction modes may be assigned different mode numbers.

As shown in FIG. 5, when the intra-prediction mode of the block to be scanned is a mode having a horizontal direction of 6 to 14, a vertical scanning order which is a vertical scanning mode can be selected and applied.

When the intra prediction mode of the block to be scanned is a mode having a vertical direction of 22 to 30, a horizontal scanning order which is a horizontal scanning mode can be selected and applied.

When the intra prediction mode of the scanning target block is a mode other than 6 to 14 and 22 to 30, i.e., a non-directional mode or a non-directional mode or a non-directional mode of 0 to 5, 15 to 21, and 31 to 34 , It is possible to select and apply the right-up diagonal scan sequence.

The scanning target block to which the above-described adaptive scanning mode is applied may be a transform block.

On the other hand, in the scalable video coding, prediction can be performed using samples or parameters of a lower layer at the time of prediction of a block to be added / decoded in an upper layer. Based on the prediction samples of the block to be decoded / obtained in the upper layer obtained through the prediction, the residual can be obtained, and the transform and quantization processes can be performed. Then, entropy coding / decoding can be performed by scanning the transform coefficient or the quantized coefficient obtained through conversion or quantization. At this time, the sub-block to be decoded of the upper layer, which is predicted using information of the lower layer, may not have the parameter information such as the intra prediction mode. In this case, since the scanning mode can not be selected adaptively, the basic scanning mode is used. As a result, the entropy coding / decoding efficiency tends to be lowered.

Accordingly, in the present invention, when an upper layer performs prediction using information of a lower layer, an adaptive scanning mode is selected using coding parameters of an upper layer or a lower layer (for example, an intra prediction mode of a lower layer) I suggest a way to do it. The entropy coding / decoding efficiency can be improved by adaptively selecting and applying a scanning mode according to the present invention to be described later.

Hereinafter, the present invention can be applied to a scalable video coding scheme supporting a plurality of layers or a scalable video coding scheme supporting a plurality of views.

6 is a flowchart schematically illustrating an image encoding method using adaptive scanning according to an embodiment of the present invention. The method of FIG. 6 can be performed in the encoding apparatus of FIG. 1 described above.

Referring to FIG. 6, in the case of performing prediction on a current block of a higher layer (current layer) in scalable video coding in which a plurality of layers exist, the encoder can perform prediction using information of a lower layer (S600). As a result of performing the prediction, a predicted sample value of the current block can be generated.

A method of predicting using information of a lower layer at the time of prediction of an upper layer will be described in detail with reference to FIG. At this time, a method of predicting an upper layer using information of a lower layer may be referred to as inter-layer prediction or inter-layer prediction.

7 is a diagram illustrating an inter-layer prediction method according to an embodiment of the present invention.

Referring to FIG. 7, when the prediction of the current block 700 of the upper layer is performed, the encoding apparatus performs a prediction of the current block 700 of the lower layer corresponding to the current block 700 of the upper layer, Can be determined. The predicted sample value of the current block 700 of the upper layer can be generated using the reconstructed sample, the residual, or the encoding parameter of the corresponding lower layer corresponding block 710.

For example, when the reconstructed sample of the lower layer corresponding block 710 is used to predict the current block 700 of the upper layer, the reconstructed sample value of the corresponding block 710 is referred to as the It can be used as a predicted sample value. Alternatively, the weighted sum of the predicted sample value of the current block to be coded 700 and the restored sample value of the corresponding block 710 may be used as the final predicted sample value of the current block 700 to be coded.

When the prediction of the current block 700 of the upper layer using the residual of the lower layer corresponding block 710 is performed by using the weighted sum of the predicted sample value of the current block 700 and the residual value of the corresponding block 710 Can be used as the final predicted sample value of the current block 700 to be coded.

The intra prediction mode or the motion information of the corresponding block 710 can be used when the current block 700 of the upper layer is predicted using the coding parameters of the corresponding block 710 of the lower layer. For example, the prediction sample value of the current block 700 can be generated by performing prediction with reference to reconstructed samples around the current block 700 based on the intra prediction mode of the corresponding block 710. [ Alternatively, the predictive sample value of the current block 700 can be generated by referring to the reference intra-reference block of the current block 700 based on the motion information of the corresponding block 710.

The weighted sum may be a value calculated using a weight ratio between an upper layer and a lower layer. For example, the weight ratio of the upper layer and the lower layer can be [1: 1], [1/2: 1/2], [1: 2], [2: 1]

In this case, the corresponding block 710 of the lower layer may be a block existing at the position of the lower layer converted by considering the resolution of the lower layer, of the block 700 of the upper layer. In addition, the image of the lower layer may be scaled by a method such as up-sampling in accordance with the scalability (e.g., size, resolution, etc.) of the upper layer.

The encoding apparatus can use information of a lower layer to determine information indicating whether prediction of the current layer is to be performed, for example, flag information indicating whether information of a lower layer is used or not, and transmit the information to the decoding apparatus. The flag indicating whether the lower layer uses the information may be determined in units of a coding unit (CTU: Coding Tree Unit or CU: Coding Unit) or a prediction unit (PU: Prediction Unit) and signaled to the decoding apparatus.

Referring back to FIG. 6, the encoding apparatus can generate a residual for a current block of a higher layer (S610).

The residual for the current block of the upper layer may be a difference value between the predicted sample value of the current block to be coded generated through inter-layer prediction in step S600 and the original sample value of the current block to be coded.

Alternatively, the encoding apparatus may derive the residual of the upper layer using the residual of the lower layer. For example, the residual of the current block to be coded of the upper layer and the residual of the corresponding block of the lower layer corresponding to the current block to be coded can be determined and determined as the final residual of the upper layer.

The encoding device may transform or / or quantize the residual to generate transform coefficients and / or quantized coefficients.

The encoding apparatus can perform adaptive scanning on the quantized coefficients (S620). The encoding apparatus can perform scanning and entropy encoding on a quantized coefficient (or a transform coefficient) obtained through transformation / quantization of residuals by selecting a scanning mode adaptively using an upper metric or a lower layer encoding parameter .

A method of adaptively selecting a scanning mode (scanning order) according to an embodiment of the present invention may be as follows.

- The scanning mode can be adaptively selected according to the intra prediction mode for the current block of the upper layer.

For example, if the predicted sample value of the current block to be coded in the upper layer is a predicted sample value obtained by performing intra prediction on the current block and a reconstructed sample value of the corresponding block in the lower layer corresponding to the current block Residual value), the scanning mode can be selected according to the intra prediction mode for the current block of the upper layer. At this time, the method of selecting the scanning mode according to the intra prediction mode can be applied to the embodiment of FIG.

- The scanning mode can be adaptively selected according to the intra prediction mode or the scanning mode of the reconstructed block located around the current block of the upper layer.

For example, when the prediction sample value of the current block of the upper layer is generated using the sample value of the corresponding block of the lower layer corresponding to the current block, the intra prediction mode for the current block of the upper layer exists . In this case, the scanning mode for the current block of the upper layer can be selected based on the intra prediction mode (or the scanning mode) obtained from the reconstructed blocks around the current block of the upper layer. At this time, the method of selecting the scanning mode based on the intra prediction mode can be applied to the embodiment of FIG.

For example, when the left block and the upper block of the current block to be coded of the upper layer are in the intra prediction mode (or the vertical scanning order) having the horizontal direction, the scanning mode for the current block to be coded of the upper layer can be selected in the vertical scanning order . When the left block and the upper block of the current block to be coded of the upper layer are in the intra prediction mode (or the horizontal scanning order) having the vertical direction, the scanning mode for the current block to be coded of the upper layer can be selected in the horizontal scanning order. When the left block or the upper block of the current block of the upper layer does not have the intra mode with the horizontal and vertical directions, or in the case of the right upward diagonal scan order or the intra prediction mode information, scanning for the current block Mode can be selected in the order of upward-diagonal scanning.

- The scanning mode can be adaptively selected according to the intra prediction mode or the scanning mode for the corresponding block of the lower layer corresponding to the current block of the upper layer.

For example, when the prediction sample value of the current block of the upper layer is generated using the sample value of the corresponding block of the lower layer, there is no intra prediction mode for the current block of the higher layer. At this time, when the corresponding block in the lower layer has the intra prediction mode, the scanning mode for the current block in the upper layer can be selected based on the intra prediction mode for the corresponding block in the lower layer. At this time, the method of selecting the scanning mode based on the intra prediction mode can be applied to the embodiment of FIG.

As another example, when the prediction sample value of the current block of the upper layer is predicted and generated based on the intra prediction mode of the corresponding block of the lower layer, The scanning mode can be selected. At this time, the method of selecting the scanning mode based on the intra prediction mode can be applied to the embodiment of FIG.

- The scanning mode can be adaptively selected according to the intra prediction mode or the scanning mode for the restored block around the corresponding block of the lower layer corresponding to the current block of the upper layer.

For example, when the corresponding block of the lower layer does not have the intra-prediction mode information, the intra-prediction mode (or the scanning mode) obtained from the reconstructed blocks around the corresponding block, You can select the scanning mode. At this time, the method of selecting the scanning mode based on the intra prediction mode can be applied to the embodiment of FIG.

The scanning mode can be adaptively selected using the intra prediction mode for the current block of the upper layer and the intra prediction mode or the scanning mode for the corresponding block of the lower layer.

For example, when a residual for a current block of an upper layer is generated using a residual of a corresponding block of a lower layer, an intra prediction mode may exist in both the current block of the upper layer and the corresponding block of the lower layer . In this case, the scanning mode can be determined using the respective intra prediction modes, and the scanning mode of the upper layer can be determined as in the embodiments (1) and (2) below.

(1) If the current block and the corresponding block have the same scanning mode, the scanning mode can be selected as the final scanning mode for the current block to be coded of the upper layer. Otherwise, when the scanning mode of the current block is different from that of the corresponding block, the right-upward diagonal scanning order can be selected as the final scanning mode for the current block to be coded of the upper layer. This can be expressed as:

Figure pat00001

(2) One of the scanning modes of the block to be coded and the corresponding block is a scanning mode having a directionality (horizontal or vertical scanning mode) and the other is a scanning mode having no directionality (a direction of upward diagonal scanning) Mode can be selected as the final scanning mode for the current block of the upper layer. This can be expressed as:

Figure pat00002

- If prediction is performed using information of the lower layer as in step S600, the residual value of the block to be coded of the upper layer may not show directionality. For example, even if intra prediction having a vertical direction is performed on a current block to be coded in an upper layer, the directionality may disappear due to information in a lower layer. In this case, regardless of the intra prediction mode, scanning can be performed on the current block of the upper layer by fixing the scanning mode to a specific scanning mode.

At this time, the specific scanning mode can be fixed in the upward-diagonal scanning order. Alternatively, it may be fixed in the vertical scanning order, or may be fixed in the horizontal scanning order.

8 is a flowchart schematically illustrating a method of decoding an image using adaptive scanning according to an embodiment of the present invention. The method of FIG. 8 can be performed in the decoding apparatus of FIG. 2 described above.

Referring to FIG. 8, when performing decoding on a block to be decoded of an upper layer (current layer) in scalable video coding in which a plurality of layers exist, the decoding apparatus can perform adaptive scanning on the quantized coefficients (S800).

The decoding apparatus entropy-decodes the bitstream received from the encoder to obtain quantized coefficients of the one-dimensional array for the current block to be decoded. Then, the scanning mode is selected adaptively for the quantized coefficients of the one-dimensional array obtained through the entropy decoding, so that scanning can be performed to rearrange the quantized coefficients of the two-dimensional array.

At this time, the quantized coefficients of the one-dimensional array are classified into a decoded block of the upper layer, a restored block located around the decoded block of the upper layer, a corresponding block of the lower layer corresponding to the decoded block, (Scanning order) may be selected and scanned adaptively based on the intra-prediction mode or the scanning mode for at least one of the restored blocks located in the block. The adaptive scanning mode (scanning order) selection method may be the same as the adaptive scanning mode selection method of the encoding apparatus, and has been described above with reference to FIG. 6, so a detailed description will be omitted.

The decoding apparatus can perform prediction on a block to be decoded of an upper layer using information of a lower layer (S810).

At this time, the decoding target block of the upper layer can be predicted by using at least one of the restored sample, residual, and coding parameters for the corresponding block of the lower layer corresponding to the block to be decoded. As a result of performing prediction, a predicted sample value of a block to be decoded can be generated.

The method of predicting (inter-layer prediction) using the information of the lower layer at the time of prediction of the upper layer may be the same as that of the inter-layer prediction method of the encoding apparatus, and has been described above with reference to FIGS. 6 and 7, and thus a detailed description thereof will be omitted.

The decoding apparatus may generate the restored block using the predicted sample value of the current block to be decoded and the residual value of the current block to be decoded (S820).

The residual value of the current block to be decoded may be a value generated by performing inverse quantization or inverse transform of the quantized coefficients (quantized coefficients of the two-dimensional array rearranged through scanning).

Alternatively, the residual value of the current block to be decoded may be derived using the residual of the lower layer. For example, the residual of the current block to be decoded of the upper layer and the residual of the corresponding block of the lower layer corresponding to the current block to be decoded can be determined and determined as the final residual of the upper layer.

The reconstruction block may be a reconstructed sample value of the current block to be decoded generated by adding the predictive sample value of the current block to be decoded generated through inter-layer prediction in step S810 and the residual value of the current block to be decoded.

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 different orders or simultaneously . It will also be understood by those skilled in the art that the steps depicted in the flowchart illustrations are not exclusive, that 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 foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the claims, and all technical ideas within the scope of the claims should be construed as being included in the scope of the present invention.

Claims (19)

A video decoding method for supporting a plurality of layers,
Selecting a scanning mode for a decoding target block of an upper layer and performing scanning;
Performing inter-layer prediction on the to-be-decoded block using information on a corresponding block in a lower layer corresponding to the to-be-decoded block; And
And generating a reconstructed sample value using a predictive sample value of the current block to be decoded generated by the inter-layer prediction and a residual value of the current block to be decoded,
In the scanning step,
A scanning mode of the current block to be decoded is determined based on an intra prediction mode or a scanning mode for at least one of a current block to be decoded, a restored block around the current block to be decoded, and a restored block around the corresponding block and the corresponding block And selecting the video decoding method. The method according to claim 1,
In the scanning step,
When the inter-layer prediction of the current block is performed using the predicted sample value of the intra-predicted current block to be decoded and the restored sample value of the corresponding block,
And a scanning mode of the current block to be decoded is selected based on the intra prediction mode of the current block to be decoded. The method according to claim 1,
In the scanning step,
When the inter-layer prediction for the current block is performed using the restored sample value of the corresponding block,
Wherein a scanning mode of the current block is selected based on an intra prediction mode or a scanning mode for a reconstructed block around the current block to be decoded. The method of claim 3,
In the scanning step,
And selects a scanning mode of the current block to be decoded in the vertical scanning order if the left reconstruction block and the upper reconstruction block around the current block to be decoded have a horizontal direction or an intra prediction mode or a vertical scanning order,
And selects a scanning mode of the current block as a horizontal scanning order if the left and right upper and lower reconstruction blocks in the vicinity of the current block to be decoded have a vertical direction,
The scanning mode of the current block to be decoded is selected in a right upward diagonal scanning order if the left reconstruction block or the upper reconstruction block around the current block to be decoded is not the intra prediction mode having the horizontal direction and the vertical direction, . The method according to claim 1,
In the scanning step,
When the inter-layer prediction for the current block is performed using the reconstructed sample value of the corresponding block or the intra prediction mode of the corresponding block,
Wherein the scanning mode of the current block is selected based on the intra prediction mode or the scanning mode of the corresponding block. 6. The method of claim 5,
In the scanning step,
Wherein the scanning mode of the current block is selected based on an intra prediction mode or a scanning mode for a reconstructed block around the corresponding block when information on an intra prediction mode of the corresponding block does not exist, Way. The method according to claim 1,
In the scanning step,
And selects a scanning mode of the current block as a final scanning mode when the decoding mode of the current block is the same as the scanning mode of the corresponding block,
Wherein when the decoding mode is different from the scanning mode of the corresponding block to be decoded, a right-upward diagonal scanning order is selected as a final scanning mode of the current block to be decoded,
The scanning mode of the current block to be decoded is selected as the final scanning mode if the scanning mode of the current block to be decoded is a horizontal or vertical scanning order and the scanning mode of the corresponding block is a rightward and upward diagonal scanning order,
And selects the scanning mode of the corresponding block as the final scanning mode of the current block if the scanning mode of the current block is the rightward diagonal scanning order and the scanning mode of the corresponding block is the horizontal or vertical scanning order. Decoding method. The method according to claim 1,
In the scanning step,
When there is no information on the intra-prediction mode of the current block and the corresponding block,
The scanning mode of the current block to be decoded is fixed to a specific scanning mode,
Wherein the specific scan mode is one of a rightward diagonal scan order, a vertical scan order, and a horizontal scan order. The method according to claim 1,
In the step of performing inter-layer prediction on the block to be decoded,
Wherein the predicted sample value of the current block is generated using at least one of a reconstruction sample, a residual, and a coding parameter of the corresponding block. 10. The method of claim 9,
In the step of performing inter-layer prediction on the block to be decoded,
Sampling the restoration sample of the corresponding block according to the resolution of the upper layer and determining the prediction sample value of the block to be decoded. 10. The method of claim 9,
In the step of performing inter-layer prediction on the block to be decoded,
Wherein the weighted sum of the restored sample of the corresponding block and the predicted sample of the current block is determined as a final predicted sample value of the current block. 10. The method of claim 9,
In the step of performing inter-layer prediction on the block to be decoded,
Wherein the weighted sum of the residual of the corresponding block and the predicted sample value of the current block is determined as a final predicted sample value of the current block. 10. The method of claim 9,
In the step of performing inter-layer prediction on the block to be decoded,
Wherein the predicted sample value of the current block is generated by referring to a reconstructed block around the current block to be decoded based on the intra prediction mode of the corresponding block. 10. The method of claim 9,
In the step of performing inter-layer prediction on the block to be decoded,
Predicted sample value of the current block to be decoded is generated by referring to the reference intra-reference block of the current block to be decoded based on the motion information of the corresponding block. The method according to claim 1,
In the step of generating the reconstructed sample value,
Wherein a weighted sum of a residual value of the current block to be decoded and a residual value of the corresponding block is calculated and determined as a final residual value of the current block to be decoded. The method according to claim 1,
In the scanning step,
Obtaining quantized coefficients of the one-dimensional array for the block to be decoded through entropy decoding; And
Determining a scanning mode for the quantized coefficients of the one-dimensional array; And
And rearranging the quantized coefficients of the one-dimensional array into quantized coefficients of the two-dimensional array by applying the scanning mode. In an image decoding apparatus supporting a plurality of layers,
A scanning unit for selecting a scanning mode for a decoding target block of an upper layer and performing scanning;
And a decoding step of performing inter-layer prediction of the current block using information on a corresponding block in a lower layer corresponding to the current block to be decoded and decoding the prediction sample value of the current block to be decoded generated by the inter- And a prediction unit for generating a restored sample value using the residual value of the target block,
The scanning unit includes:
A scanning mode of the current block to be decoded is determined based on an intra prediction mode or a scanning mode for at least one of a current block to be decoded, a restored block around the current block to be decoded, and a restored block around the corresponding block and the corresponding block And outputs the decoded video data. A video encoding method for supporting a plurality of layers,
Performing inter-layer prediction on the current block using information on a corresponding block of a lower layer corresponding to a current block of a higher layer;
Generating a residual value of the current block based on a predicted sample value of the current block generated by the inter-layer prediction; And
And performing scanning by selecting a scanning mode for the coefficients of the current block obtained through at least one of conversion and quantization of the residual value,
In the scanning step,
A scanning mode of the current block to be coded is determined based on an intra prediction mode or a scanning mode for at least one of a current block to be coded, a restoration block around the current block, a restored block around the corresponding block, And selecting the image. A video encoding apparatus supporting a plurality of layers,
A prediction unit for performing inter-layer prediction on the current block using information about a corresponding block of a lower layer corresponding to a current block to be coded of an upper layer;
A residual value generation unit for generating a residual value of the current block based on a prediction sample value of the current block generated by the inter-layer prediction; And
And a scanning unit for performing scanning by selecting a scanning mode for the coefficients of the current block obtained through at least one of conversion and quantization of the residual value,
The scanning unit includes:
A scanning mode of the current block to be coded is determined based on an intra prediction mode or a scanning mode for at least one of a current block to be coded, a restoration block around the current block, a restored block around the corresponding block, And selects the image to be encoded.
KR1020130149063A 2012-12-03 2013-12-03 Method and apparatus for image encoding/decoding KR20140073430A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR20120138696 2012-12-03
KR1020120138696 2012-12-03

Publications (1)

Publication Number Publication Date
KR20140073430A true KR20140073430A (en) 2014-06-16

Family

ID=51126971

Family Applications (1)

Application Number Title Priority Date Filing Date
KR1020130149063A KR20140073430A (en) 2012-12-03 2013-12-03 Method and apparatus for image encoding/decoding

Country Status (1)

Country Link
KR (1) KR20140073430A (en)

Similar Documents

Publication Publication Date Title
KR101867884B1 (en) Method for encoding/decoding an intra prediction mode and apparatus for the same
KR101979681B1 (en) Method for image encoding and computer readable redording meduim thereof
TWI766844B (en) Improved video intra-prediction using position-dependent prediction combination for video coding
KR101542586B1 (en) Method and apparatus for encoding/decoding image
KR102508989B1 (en) Method and apparatus for scalable video coding using intra prediction mode
KR20140008503A (en) Method and apparatus for image encoding/decoding
WO2014055345A1 (en) Intra-coding for 4:2:2 sample format in video coding
KR20140043037A (en) Method and apparatus for compensating sample adaptive offset for encoding inter layer prediction error
KR20120033289A (en) Method and apparatus for image encoding/decoding using prediction of filter information
US20150312571A1 (en) Method and device for encoding/ decoding image supporting plurality of layers
KR20140122189A (en) Method and Apparatus for Image Encoding and Decoding Using Inter-Layer Combined Intra Prediction
KR20110043407A (en) Video coding and decoding method and apparatus
KR101685556B1 (en) Method and apparatus for image encoding/decoding
KR101420718B1 (en) Method and apparatus for scalable video encoding and decoding
JP7451722B2 (en) Image coding method and device based on transformation
KR20140073430A (en) Method and apparatus for image encoding/decoding
KR20150008337A (en) Video decoding method and apparatus using the same
KR20140106450A (en) Method and apparatus for scalable video encoding considering memory bandwidth and calculation complexity, method and apparatus for scalable video decoding considering memory bandwidth and calculation complexity

Legal Events

Date Code Title Description
WITN Withdrawal due to no request for examination