KR101981687B1 - Method and apparatus for coding offset information and decoding using the same - Google Patents

Abstract

According to another aspect of the present invention, there is provided a method of encoding an offset information of an image, comprising the steps of: identifying a plurality of offset units; checking offset information of each of the plurality of offset units; encoding the offset information of each of the plurality of offset units And encoding the offset information for some offset units among the plurality of offset units

Description

[0001] METHOD AND APPARATUS FOR CODING OFFSET INFORMATION AND DECODING USING THE SAME [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video encoding and decoding method and apparatus, and more particularly, to a method and apparatus for encoding and decoding offset information.

Recently, the demand for high resolution and high quality images such as high definition (HD) image and ultra high definition (UHD) image is increasing in various applications. As the image data has high resolution and high quality, the amount of data increases relative to the existing image data. Therefore, when the image data is transmitted using a medium such as a wired / wireless broadband line or stored using an existing storage medium, The storage cost is increased. High-efficiency image compression techniques can be used to solve these problems caused by high-resolution and high-quality image data.

An inter picture prediction technique for predicting a pixel value included in a current picture from a previous or a subsequent picture of a current picture by an image compression technique, an intra picture prediction technique for predicting a pixel value included in a current picture using pixel information in the current picture, There are various techniques such as an entropy encoding technique in which a short code is assigned to a value having a high appearance frequency and a long code is assigned to a value having a low appearance frequency. Image data can be effectively compressed and transmitted or stored using such an image compression technique.

On the other hand, demand for high-resolution images is increasing, and demand for stereoscopic image content as a new image service is also increasing. Video compression techniques are being discussed to effectively provide high resolution and ultra-high resolution stereoscopic content.

The present invention can provide a method and apparatus for reducing the amount of bits generated for encoding offset information in a process of encoding / decoding a video signal.

In addition, the present invention can provide a method and an apparatus that can reduce the number of encoding bits using simple processing and calculation.

In addition, the present invention can provide a method and an apparatus capable of adaptively encoding offset information in consideration of a hardware environment of an encoding apparatus and a decoding apparatus, a communication environment between the encoding apparatus and a decoding apparatus, and the like.

According to an aspect of the present invention, there is provided a method of encoding an offset information of an image, comprising: identifying a plurality of offset units; checking offset information of each of the plurality of offset units; And encoding the offset information for some offset units of the plurality of offset units.

According to another aspect of the present invention, there is provided an apparatus for encoding image data, the apparatus comprising: an offset correction unit for identifying a plurality of offset units and checking and providing offset information for each of the plurality of offset units; And an offset encoding unit encoding the offset information for each of the plurality of offset units and encoding the offset information for some offset units of the plurality of offset units.

According to another aspect of the present invention, there is provided a method of decoding encoded image data, the method including decoding the offset information for each of a plurality of offset units, decoding the offset information for some offset units of the plurality of offset units, Decoding the offset information for a residual offset unit not included in some offset units among the plurality of offset units; providing offset information for the partial offset unit and the residual offset unit; And restoring the pixel information of the encoding unit by reflecting offset information on the unit and the residual offset unit.

According to another aspect of the present invention, there is provided an apparatus for decoding encoded image data, the apparatus comprising: a decoder for decoding the offset information for each of a plurality of offset units, decoding the offset information for some offset units of the plurality of offset units, An offset information decoding unit for decoding the offset information for a residual offset unit not included in some offset units among a plurality of offset units and providing the offset information for the remaining offset units; And an offset correction unit for restoring the pixel information of the pixel.

According to the present invention, it is possible to reduce the number of bits generated for encoding offset information in a process of encoding / decoding a video signal.

Further, according to the present invention, it is possible to reduce the number of encoding bits by using a simple process and an arithmetic operation, and further to adaptively store offset information in consideration of a hardware environment of the encoding apparatus and the decoding apparatus, a communication environment between the encoding apparatus and the decoding apparatus, Can be encoded.

1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating an image decoding apparatus according to an embodiment of the present invention.
3 is a block diagram illustrating a detailed configuration of an offset information encoding unit included in an image encoding apparatus according to an embodiment of the present invention.
FIG. 4A is a diagram illustrating an edge class, an edge category, and the like that are processed by the offset information encoding unit in FIG.
FIG. 4B is a diagram illustrating a band category processed by the offset information encoding unit of FIG. 3; FIG.
FIG. 5A is a diagram illustrating edge offset information processed by the offset information encoding unit of FIG. 3; FIG.
FIG. 5B is a diagram illustrating band offset information processed by the offset information encoding unit of FIG. 3. FIG.
6 is a block diagram illustrating a detailed configuration of an offset information decoding unit included in an image decoding apparatus according to an exemplary embodiment of the present invention.
7 is a flowchart illustrating a procedure of an offset information encoding method according to an embodiment of the present invention.
8 is a flowchart showing a procedure of an offset information restoration method according to an embodiment of the present disclosure.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, etc. 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 a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

The definitions of the terms used in the present disclosure are as follows.

The temporary prediction direction may be a direction in which the range of the entire prediction direction is divided into a predetermined number according to a predetermined rule.

The temporary block may include a block predicted based on reference pixel information existing in each temporary prediction direction.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals will be used for the same constituent elements in the drawings, and redundant explanations for the same constituent elements will be omitted.

1 is a block diagram illustrating an image encoding apparatus according to an embodiment of the present invention.

1, the image encoding apparatus 100 includes a picture division unit 110, prediction units 120 and 125, a transform unit 130, a quantization unit 135, a reordering unit 160, an entropy encoding unit An inverse quantization unit 140, an inverse transform unit 145, a filter unit 150, and a memory 155. [

Each of the components shown in FIG. 1 is shown independently to represent different characteristic functions in the image encoding apparatus, and does not mean that each component is composed of separate hardware or one software configuration unit. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of the constituent units may be combined to 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 separate embodiments of the components are also included within 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.

The picture division unit 110 may divide the input picture into at least one processing unit. At this time, the processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU). The picture division unit 110 divides one picture into a plurality of coding units, a prediction unit, and a combination of conversion units, and generates a coding unit, a prediction unit, and a conversion unit combination So that the picture can be encoded.

For example, one picture may be divided into a plurality of coding units. In order to divide a coding unit in a picture, a recursive tree structure such as a quad tree structure can be used. In a coding or decoding scheme in which one picture or a largest coding unit is used as a root and divided into other coding units A unit can be divided with as many child nodes as the number of divided coding units. Under certain constraints, an encoding unit that is no longer segmented becomes a leaf node. That is, when it is assumed that only one square division is possible for one coding unit, one coding unit can be divided into a maximum of four different coding units.

Hereinafter, in the embodiment of the present invention, a coding unit may be used as a unit for performing coding, or may be used as a unit for performing decoding.

The prediction unit may be one divided into at least one square or rectangular shape having the same size in one coding unit, and one of the prediction units in one coding unit may be divided into another prediction Or may have a shape and / or size different from the unit.

If a prediction unit performing intra prediction on the basis of an encoding unit is not the minimum encoding unit at the time of generation, intraprediction can be performed without dividing the prediction unit into a plurality of prediction units NxN.

The prediction units 120 and 125 may include an inter prediction unit 120 for performing inter prediction and an intra prediction unit 125 for performing intra prediction. It is possible to determine whether to use inter prediction or intra prediction for a prediction unit and to determine concrete information (e.g., intra prediction mode, motion vector, reference picture, etc.) according to each prediction method. At this time, the processing unit in which the prediction is performed may be different from the processing unit in which the prediction method and the concrete contents are determined. For example, the method of prediction, the prediction mode and the like are determined as a prediction unit, and the execution of the prediction may be performed in a conversion unit. The residual value (residual block) between the generated prediction block and the original block can be input to the conversion unit 130. [ In addition, the prediction mode information, motion vector information, and the like used for prediction can be encoded by the entropy encoding unit 165 together with the residual value and transmitted to the decoder. When a particular encoding mode is used, it is also possible to directly encode the original block and transmit it to the decoding unit without generating a prediction block through the prediction units 120 and 125.

The inter-prediction unit 120 may predict a prediction unit based on information of at least one of a previous picture or a following picture of the current picture, and may predict a prediction unit based on information of a partially- Unit may be predicted. The inter prediction unit 120 may include a reference picture interpolation unit, a motion prediction unit, and a motion compensation unit.

In the reference picture interpolating unit, reference picture information is supplied from the memory 155 and pixel information of an integer pixel or less can be generated in the reference picture. In the case of a luminance pixel, a DCT-based Interpolation Filter (DCT) based on a different filter coefficient may be used to generate pixel information of less than an integer number of pixels in quarter-pixel units. In the case of a color difference signal, a DCT-based 4-tap interpolation filter may be used that generates a pixel information of an integer number of pixels or less in units of 1/8 pixel.

The motion prediction unit may perform motion prediction based on the reference picture interpolated by the reference picture interpolating unit. Various methods such as Full Search-based Block Matching Algorithm (FBMA), Three Step Search (TSS), and New Three-Step Search Algorithm (NTS) can be used as methods for calculating motion vectors. The motion vector may have a motion vector value of 1/2 or 1/4 pixel unit based on the interpolated pixel. The motion prediction unit can predict the current prediction unit by making the motion prediction method different. Various methods such as a skip method, a merge method, an AMVP (Advanced Motion Vector Prediction) method, and an Intra Block Copy method can be used as the motion prediction method.

The intraprediction unit 125 may set a prediction unit based on reference pixel information around the current block, which is pixel information in the current picture, and perform intra prediction on the set prediction unit to generate a prediction block. In the case where the neighboring block of the current prediction unit is the block in which the inter prediction is performed so that the reference pixel is the pixel performing the inter prediction, the reference pixel included in the block in which the inter prediction is performed is referred to as the reference pixel Information. That is, when the reference pixel is not available, the reference pixel information that is not available may be replaced by at least one reference pixel among the available reference pixels.

In intra prediction, the prediction mode may have a directional prediction mode in which reference pixel information is used according to a prediction direction, and a non-directional mode in which direction information is not used in prediction. The mode for predicting the luminance information may be different from the mode for predicting the chrominance information and the intra prediction mode information or predicted luminance signal information used for predicting the luminance information may be utilized to predict the chrominance information.

When intraprediction is performed, when the size of the prediction unit is the same as the size of the conversion unit, intra prediction is performed on the prediction unit based on pixels existing on the left side of the prediction unit, pixels existing on the upper left side, Can be performed. However, when intra prediction is performed, when the size of the prediction unit differs from the size of the conversion unit, intraprediction can be performed using the reference pixel based on the conversion unit. It is also possible to use intra prediction using N x N divisions for only the minimum coding units.

In the intra prediction method, an adaptive intra-smoothing filter (AISFAdaptive Intra Smoothing Filter) may be applied to a reference pixel according to a prediction mode, and then a prediction block may be generated. The type of adaptive intra smoothing filter applied to the reference pixel may be different. In order to perform the intra prediction method, the intra prediction mode of the current prediction unit can be predicted from the intra prediction mode of the prediction unit existing around the current prediction unit. In the case where the prediction mode of the current prediction unit is predicted using the mode information predicted from the peripheral prediction unit, if the intra prediction mode of the current prediction unit is the same as the intra prediction mode of the current prediction unit, The prediction mode information of the current block can be encoded by performing entropy encoding if the prediction mode of the current prediction unit is different from the prediction mode of the neighbor prediction unit.

In addition, a residual block including a prediction unit that has been predicted based on the prediction unit generated by the prediction units 120 and 125 and a residual value that is a difference value from the original block of the prediction unit may be generated. The generated residual block may be input to the transform unit 130. [

The transforming unit 130 transforms the residual block including the residual information of the prediction unit generated through the original block and the predictors 120 and 125 into a DCT (Discrete Cosine Transform), a DST (Discrete Sine Transform), a KLT Karhunen-Loeve Transform). The decision to apply the DCT, DST, or KLT to transform the residual block may be based on the intra prediction mode information of the prediction unit used to generate the residual block.

The quantization unit 135 may quantize the values converted into the frequency domain by the conversion unit 130. [ The quantization factor may vary depending on the block or the importance of the image. The values calculated by the quantization unit 135 may be provided to the inverse quantization unit 140 and the reorder unit 160.

The reordering unit 160 can reorder the coefficient values with respect to the quantized residual values.

The reordering unit 160 may change the two-dimensional block type coefficient to a one-dimensional vector form through a coefficient scanning method. For example, the rearranging unit 160 may scan a DC coefficient to a coefficient in a high frequency region using a Zig-Zag scan method, and change the DC coefficient to a one-dimensional vector form. Instead of the jig-jag scan, a vertical scan may be used to scan two-dimensional block type coefficients in a column direction, and a horizontal scan to scan a two-dimensional block type coefficient in a row direction depending on the size of the conversion unit and the intra prediction mode. That is, it is possible to determine whether any scanning method among the jig-jag scan, the vertical direction scan and the horizontal direction scan is used according to the size of the conversion unit and the intra prediction mode.

The entropy encoding unit 165 may perform entropy encoding based on the values calculated by the reordering unit 160. For entropy encoding, various encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be used.

The entropy encoding unit 165 receives the residual value count information of the encoding unit, the block type information, the prediction mode information, the division unit information, the prediction unit information and the transmission unit information, and the motion information of the motion unit from the reordering unit 160 and the prediction units 120 and 125 Vector information, reference frame information, interpolation information of a block, filtering information, and the like.

The entropy encoding unit 165 can entropy-encode the coefficient value of the encoding unit input by the reordering unit 160. [

The inverse quantization unit 140 and the inverse transformation unit 145 inverse quantize the quantized values in the quantization unit 135 and inversely transform the converted values in the conversion unit 130. [ The residual value generated by the inverse quantization unit 140 and the inverse transform unit 145 is combined with the prediction unit predicted through the motion estimation unit, the motion compensation unit and the intra prediction unit included in the prediction units 120 and 125, A block (Reconstructed Block) can be generated.

The filter unit 150 may include at least one of a deblocking filter, an offset correction unit, and an adaptive loop filter (ALF).

The deblocking filter can remove block distortion caused by the boundary between the blocks in the reconstructed picture. It may be determined whether to apply a deblocking filter to the current block based on pixels included in a few columns or rows included in the block to determine whether to perform deblocking. When a deblocking filter is applied to a block, a strong filter or a weak filter may be applied according to the deblocking filtering strength required. In applying the deblocking filter, horizontal filtering and vertical filtering may be performed concurrently in performing vertical filtering and horizontal filtering.

The offset correction unit may correct the offset of the deblocked image with respect to the original image in units of pixels. In order to perform offset correction for a specific picture, pixels included in an image are divided into a predetermined number of areas, and then an area to be offset is determined and an offset is applied to the area. Alternatively, Can be used.

 The adaptive loop filter can be performed based on a value obtained by comparing the filtered reconstructed image with the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the group may be determined and different filtering may be performed for each group. Information related to whether to apply the adaptive loop filter may be transmitted for each coding unit (CU), and the shape and the filter coefficient of the adaptive loop filter to be applied to each block may be different. Also, an adaptive loop filter filter of the same type (fixed form) may be applied regardless of the characteristics of the application target block.

The memory 155 may store the reconstructed block or picture calculated through the filter unit 150 and the reconstructed block or picture stored therein may be provided to the predictor 120 or 125 when the inter prediction is performed.

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

2, the image decoder 200 includes an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, prediction units 230 and 235, 240, and a memory 245 may be included.

When an image bitstream is input in the image encoder, the input bitstream may be decoded in a procedure opposite to that of the image encoder.

The entropy decoding unit 210 can perform entropy decoding in a procedure opposite to that in which entropy encoding is performed in the entropy encoding unit of the image encoder. For example, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be applied in accordance with the method performed by the image encoder.

The entropy decoding unit 210 may decode information related to intra prediction and inter prediction performed in the encoder.

The reordering unit 215 can perform reordering based on a method in which the entropy decoding unit 210 rearranges the entropy-decoded bitstreams in the encoding unit. The coefficients represented by the one-dimensional vector form can be rearranged by restoring the coefficients of the two-dimensional block form again. The reordering unit 215 can perform reordering by receiving information related to the coefficient scanning performed by the encoding unit and performing a reverse scanning based on the scanning order performed by the encoding unit.

The inverse quantization unit 220 can perform inverse quantization based on the quantization parameters provided by the encoder and the coefficient values of the re-arranged blocks.

The inverse transform unit 225 may perform an inverse DCT, an inverse DST, and an inverse KLT on the DCT, DST, and KLT transformations performed by the transform unit on the quantization result performed by the image encoder. The inverse transform can be performed based on the transmission unit determined by the image encoder. In the inverse transform unit 225 of the image decoder, a transform technique (e.g., DCT, DST, KLT) may be selectively performed according to a plurality of information such as a prediction method, a size of a current block, and a prediction direction.

The prediction units 230 and 235 can generate a prediction block based on the prediction block generation related information provided by the entropy decoding unit 210 and the previously decoded block or picture information provided in the memory 245. [

As described above, when intra prediction is performed in the same manner as in the image encoder, when the size of the prediction unit is the same as the size of the conversion unit, pixels existing on the left side of the prediction unit, pixels existing on the upper left side, However, when the size of the prediction unit differs from the size of the prediction unit in intra prediction, intraprediction is performed using a reference pixel based on the conversion unit . It is also possible to use intra prediction using N x N divisions for only the minimum coding unit.

The prediction units 230 and 235 may include a prediction unit determination unit, an inter prediction unit, and an intra prediction unit. The prediction unit determination unit receives various information such as prediction unit information input from the entropy decoding unit 210, prediction mode information of the intra prediction method, motion prediction related information of the inter prediction method, and identifies prediction units in the current coding unit. It is possible to determine whether the unit performs inter prediction or intra prediction. The inter prediction unit 230 predicts the current prediction based on the information included in at least one of the previous picture of the current picture or the following picture including the current prediction unit by using information necessary for inter prediction of the current prediction unit provided by the image encoder, Unit can be performed. Alternatively, the inter prediction may be performed on the basis of the information of the partial region previously reconstructed in the current picture including the current prediction unit.

In order to perform inter prediction, a motion prediction method of a prediction unit included in a corresponding encoding unit on the basis of an encoding unit includes a skip mode, a merge mode, an AMVP mode, and an intra block copy mode It is possible to judge whether or not it is any method.

The intra prediction unit 235 can generate a prediction block based on the pixel information in the current picture. If the prediction unit is a prediction unit that performs intra prediction, intra prediction can be performed based on intra prediction mode information of a prediction unit provided by the image encoder to generate a prediction block. The intraprediction unit 235 may include an Adaptive Intra Smoothing Filter (AISF), a reference pixel interpolator, and a DC filter. The adaptive intra-smoothing filter performs filtering on the reference pixels of the current block, and can determine whether to apply the filter according to the prediction mode of the current prediction unit. The adaptive intra-smoothing filtering can be performed on the reference pixels of the current block by using the prediction mode of the prediction unit provided in the image encoder and the adaptive intra-smoothing filter information. If the prediction mode of the current block is a mode in which adaptive intra-smoothing filtering is not performed, the adaptive intra-smoothing filter may not be applied.

The reference pixel interpolator may interpolate the reference pixel to generate a reference pixel in units of pixels less than an integer value when the prediction mode of the prediction unit is a prediction unit that performs intra prediction based on the pixel value obtained by interpolating the reference pixel. The reference pixel may not be interpolated in the prediction mode in which the prediction mode of the current prediction unit generates a prediction block without interpolating the reference pixel. The DC filter can generate a prediction block through filtering when the prediction mode of the current block is the DC mode.

The restored block or picture may be provided to the filter unit 240. The filter unit 240 may include a deblocking filter, an offset correction unit, and an adaptive loop filter.

When information on whether a deblocking filter is applied to a corresponding block or picture from the image encoder or a deblocking filter is applied, information on whether a strong filter or a weak filter is applied can be provided. In the deblocking filter of the video decoder, the deblocking filter related information provided by the video encoder is provided, and the video decoder can perform deblocking filtering for the corresponding block.

The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction applied to the image and the offset value information during encoding.

The adaptive loop filter can be applied to an encoding unit based on adaptive loop filter application information provided from an encoder, adaptive loop filter coefficient information, and the like. Such adaptive loop filter information may be provided in a specific set of parameters.

The memory 245 may store the reconstructed picture or block to be used as a reference picture or a reference block, and may also provide the reconstructed picture to the output unit.

As described above, in the embodiment of the present invention, a coding unit (coding unit) is used as a coding unit for convenience of explanation, but it may be a unit for performing not only coding but also decoding.

3 is a block diagram illustrating a detailed configuration of an offset processing unit 30 included in an image encoding apparatus according to an embodiment of the present invention.

 Referring to FIG. 3, the offset processing unit 30 included in the image encoding apparatus according to an exemplary embodiment of the present invention may include an offset correction unit 31 and an offset information encoding unit 35.

The offset correction unit 31 may be included in the filter unit 150 of the image coding apparatus 100. The offset information coding unit 35 may include the filter unit 150 of the image coding apparatus 100, ) Or the entropy encoding unit 165. [

The offset correcting unit 31 may correct the offset of the reconstructed image with respect to the original image in units of pixels. The reconstructed image may be an image subjected to deblocking filtering. In order to perform offset correction for a specific picture, a method of dividing a pixel included in an image into a predetermined number of regions (for example, encoding units), determining an area to be offset and applying an offset to the corresponding area, A method of applying an offset in consideration of edge information can be used.

More specifically, the offset correcting unit 31 can determine an offset type (e.g., SAO type) for the encoding unit. The offset type may include an edge type and a band type. Accordingly, the offset correcting unit 31 can determine whether the encoding unit is suitable to classify the pixels according to the edge type or the pixels according to the band type.

When the offset type is determined to be an edge type, the offset correcting unit 31 corrects the direction of the reconstructed pixels in accordance with the direction and shape of the edge reconstructed by the encoding unit with the neighboring pixels or the difference / The offset between the pixels of the original image can be determined.

The offset correcting unit 31 can determine the offset class for each of the restored pixels according to the offset type of the encoding unit. In the edge type, the offset correcting unit 31 can determine the offset class for each reconstruction pixel in the encoding unit. The offset class determined in the edge type is referred to as an edge class.

The edge class 410 (see FIG. 4A) may include information about the direction of the edge that the reconstructed pixel forms with neighboring pixels, and in particular represents a direction of 0 DEG, 90 DEG, 45 DEG, or 135 DEG . That is, the first edge class 411 represents the edge direction of 0 占 the second edge class 412 represents the edge direction of 90 占 the third edge class 413 represents the edge direction of 135 占, The fourth edge class 414 may represent an edge direction of 45 degrees. The neighboring pixels may include at least one of left, right, top, bottom, or pixels adjacent to each corner based on the restored pixel. The position of the neighboring pixel may be determined in consideration of the edge direction according to the edge class. The neighboring pixels may be consecutive N pixels based on the restored pixel. Where N may be an integer greater than or equal to one. The N may be set in the image encoding apparatus or may be variably set in consideration of the filter type, the filter strength, the size / shape of the encoding unit, and the like.

In addition, the offset correcting unit 31 can set the edge category 420 based on the edge type that the reconstruction pixel of the encoding unit forms with neighboring pixels. For example, the offset correction unit 31 sets the first edge category 421 when the edge shape formed by the restoration pixel with neighboring pixels indicates a local valley of concave, Is set to the second edge category 422 when the curve corner of the edge is indicated and to the third edge category 423 when the curve corner of the convex edge is represented and the local peak of the convex edge peak) is set, the fourth edge category 424 is set.

Also, the offset correcting unit 31 can determine the offset value using the difference value between the restored pixel and the original pixels, for restored pixels that belong to the same edge category in the encoding unit. Specifically, for each edge category, the average of the differences between the restored pixel and the original pixel, that is, the average error of the restored pixels, can be determined as the offset value of the corresponding edge category.

For example, when the offset type of an encoding unit is an edge type and the restored pixels are classified into four categories according to the edge type, the offset correcting unit 31 calculates the average error between the restored pixel belonging to the four edge categories and the original pixel The four edge offset values calculated based on the four edge offset values can be determined.

Although the offset corrector 31 exemplifies the edge class and the edge category in the embodiment of the present disclosure, the present disclosure is not limited thereto, and the edge class may include various numbers And the edge category can also be set to various numbers reflecting various edge types.

On the other hand, when the offset type is determined to be a band type, the offset correcting unit 31 can set a predetermined band in consideration of the total range of pixel values of the encoding unit. That is, when the total range of pixel values of the encoding unit is divided into a predetermined number of consecutive pixel value intervals, each pixel value interval can be set to a band. On the basis of this, the offset correcting unit 31 can confirm the bands of the interval in which the pixel values continuously exist, and set the information about the start point of the bands.

For example, if the pixel value is an 8-bit sample, the total range of pixel values in the encoding unit is 0 to 255, and the pixel value can be divided into a total of 32 bands 450 (see FIG. 4B). In this case, a predetermined number of bands to which the pixel values of the restored pixels belong may be determined from a total of 32 bands 450. Accordingly, the offset correcting unit 31 can set the starting position (left starting point) of the consecutive predetermined number of bands to the band starting point 451. This band start point can be determined using a band index value of 0 to 31. [

In the band type, the offset correcting unit 31 can set a predetermined number of band categories 455 according to the position of the band to which the pixel value of the reconstruction pixel of the encoding unit belongs. For example, according to the band index of consecutive m (e.g., four) bands from the band start point 451, the restored pixels may be classified into m band categories 455. [ For each restoration pixel of the coding unit, the offset correcting unit 31 determines which band category belongs to m (for example, four) band categories depending on which band among m (for example, four) bands belongs And this value can be set to the value of the band category 455. [

In addition, the offset correcting unit 31 can set an offset value in units of a band category (455). That is, the offset correcting unit 31 may determine an average error value between the restored pixels belonging to each band category 455 and the original pixels as the offset of the corresponding band category 455.

Further, bands may optionally divide the total range of pixel values at evenly spaced intervals or at unequal intervals. Therefore, the offset correcting unit 31 can determine the offset type of the encoding unit indicating whether the edge type or the band type, based on the spatial characteristic of the pixel values of the encoding unit.

Although the embodiments of the present disclosure illustrate the band start point and the band category, the present disclosure is not limited thereto, and the band may be set to various numbers reflecting the total range of the pixel values of the encoding unit and the bit values Of course, the band category can also be set to various numbers.

Thus, when the offset value of the category unit (edge category, band category) is determined by the offset correcting unit 31, the determined offset value is provided to the offset information encoding unit 35. [ The offset information encoding unit 35 may encode and output an offset parameter including at least one of information on the offset value, that is, an offset type, an offset class, or an offset value of the encoding unit.

More specifically, the offset correcting unit 31 can provide the offset type and the offset value to the offset information encoding unit 35. [ The offset type may include an Off type, an Edge type, or a Band type. Accordingly, the offset information encoding unit 35 can encode an identifier that identifies an Off type, an Edge type, or a Band type.

In the case of the edge type, the offset correcting unit 31 can provide the offset information encoding unit 35 with offset values in the edge class, the edge category, and the edge category unit. Correspondingly, the offset information encoding unit 35 can generate an offset value reflecting the edge class and the edge category, and can code the offset value. The encoding may further include rearranging the generated offset values. The rearrangement may be performed considering at least one of whether the offset value is a predetermined constant or the size of the offset. The predetermined constant may be a fixed value (for example, " 0 ") pre-assigned to the image encoding apparatus. The offset information encoding unit 35 encodes the information necessary for the reordering and outputs the encoded information.

For example, when the offset correcting unit 31 provides the offset value 500 illustrated in FIG. 5A, the offset information encoding unit 35 obtains the edge value of each edge category 510 in the order of the edge class and the edge category. The offset value 520 can be encoded. At this time, the offset value 520 of the edge category may exist in various ways, and the offset value 520 of the edge category 510 may be a value of " 0 ". Accordingly, when the offset value 520 is aligned according to the order of the edge categories, the edge category 521 having an offset value of " 0 " may cause the bit string to increase in size. Taking this into consideration, the offset information encoding unit 35 relatively arranges the edge category 531 having the offset value other than " 0 " in the forward direction and the edge category 521 having the offset value of " 0 & . ≪ / RTI > The offset information encoding unit 35 encodes the offset value of the edge category 531 having an offset value other than "0", and the offset value of the edge category 521 having the offset value of "0" It can be encoded so as not to be included.

On the other hand, in the case of the band type, the offset correcting unit 31 can provide the offset information encoding unit 35 with the offset value of the band starting point and the band category unit. In response to this, the offset information encoding unit 35 can generate and encode an offset value reflecting the band start point and the band category. The encoding may further include rearranging the offset value, as described in the edge type.

For example, when the offset correcting unit 31 provides the offset value 550 illustrated in FIG. 5B, the offset information encoding unit 35 outputs the offset information 550 shown in FIG. 5B to each band category 560 in the order of the band start point and the band category. The absolute value 561 of the offset and the code value 562 of the frame can be encoded. At this time, the offset absolute value 561 and the sign value 562 of the band category may exist in various ways, and the offset absolute value 561 of the band category 560 may be a value of " 0 ". Accordingly, when the offset absolute value 561 is aligned in the order of the band category, the problem arises that the bit string is increased in size by the band category 571 having an offset value of " 0 ". Taking this into consideration, the offset information encoding section 35 relatively arranges the band category 571 having the offset value other than " 0 " in the forward direction and the band category 572 having the offset value " 0 " . ≪ / RTI > The offset information encoding unit 35 encodes the offset absolute value and the sign value of the band category 571 having an offset value other than " 0 ", and outputs the offset value of the band category 572 having the offset value of & The value can be encoded so that it is not included in the bit stream.

As described above, since the offset value of the category having the offset value of " 0 " is not included in the bit string, the number of bits consumed for encoding the encoded value of " 0 " can be saved and the encoded data efficiency can be increased .

Furthermore, the offset processing unit 30 according to the embodiment of the present invention can variously change the number or types of edge categories or band categories so that the number of edge categories or band categories having an offset value of " 0 & have.

For example, if the number of pixels corresponding to the edge category or band category is small enough, then the pixel has a high probability that the gain for the offset is not very high. That is, it is meaningful only when the gain of the image quality improved by the offset is relatively larger than the bit amount necessary for transmitting the offset. Taking this into consideration, if the number of pixels included in the corresponding category (edge category or band category) is sufficiently small, the offset value for the corresponding category (edge category or band category) can be set to 0 and encoded. Specifically, the offset information encoding unit 35 confirms the number of pixels included in the category (edge category or band category), and when the number of pixels included in the category is equal to or smaller than a predetermined threshold value, Can be set to " 0 ". At this time, the offset information encoding unit 35 determines an optimum value by using a fixed predetermined threshold value or considering the relationship between the image quality gain by the offset amount of the encoded bit amount of the offset information and the determined optimum value May be encoded.

Further, the optimal value may not be encoded, and the image decoding unit may derive the optimal value using a method of determining the optimum value.

6 is a block diagram illustrating a detailed configuration of an offset information restoring unit included in an image decoding apparatus according to an embodiment of the present disclosure.

The offset information reconstructing unit 60 may perform offset correction on an image reconstructed based on an offset type and an offset value applied to the image during encoding.

More specifically, the offset information reconstructing unit 60 may include an offset information decoding unit 61 and an offset correcting unit 65.

The offset information decoding unit 61 identifies an offset type (e.g., SAO type) from the encoded information. That is, the offset information decoding unit 61 can determine the offset type by checking the identifiers identifying the Off type, Edge type, or Band type.

In the case of the edge type, the offset information decoding unit 61 can restore the information about the edge class and the offset value in units of the edge category and provide it to the offset correction unit 65. [

At this time, the offset value of the edge category unit is encoded only in the offset value of the edge category having an offset value other than " 0 ", and the offset value of the edge category having the offset value of " 0 " Accordingly, the offset information decoding unit 61 restores the offset value of the edge category having the offset value other than " 0 ", and then sets the offset value of the category not included in the bit string to " 0 ". The offset information decoding unit 61 may rearrange the offset values of the edge categories and provide the offset values corresponding to the order of the edge categories to the offset correction unit 65. [ The reordering may be performed based on the reordering related information signaled by the image encoding apparatus.

Corresponding to this, the offset correcting unit 65 can apply the offset value of the edge class and the edge category to recover the value of the corresponding pixel.

On the other hand, in the case of the band type, the offset information decoding unit 61 may decode the offset values of the band starting point and the band category unit and provide them to the offset correcting unit 65.

At this time, only the offset value of the band category having the offset value other than " 0 " is coded and the offset value of the band category having the offset value of " 0 & The value is not included in the bit string. Accordingly, the offset information decoding unit 61 restores the offset value of the band category having an offset value other than " 0 ", and then sets the offset value of the category not included in the bit string to " 0 ". The offset information decoding unit 61 may rearrange the offset values of the band categories and provide the offset values corresponding to the order of the band categories to the offset correction unit 65. [ The reordering may be performed based on the reordering related information signaled by the image encoding apparatus.

Corresponding to this, the offset correcting unit 65 may apply the offset value of the band start point and the band category to recover the value of the corresponding pixel.

7 is a flowchart illustrating a procedure of an offset information encoding method according to an embodiment of the present invention.

 Referring to FIG. 7, the offset information encoding method according to an embodiment of the present invention may be performed by the offset processing unit 30 of the image encoding apparatus described above.

First, the offset processing unit 30 can determine an offset type (e.g., SAO type) for a coding unit (S701). The offset type may include an edge type and a band type. Accordingly, the offset processing unit 30 can determine whether to process the offset encoding for the encoding unit, classify the encoding unit according to the edge type, or classify the pixels according to the band type.

When the offset coding is not performed (S702-a), the offset processing unit 30 completes the offset coding for the coding unit.

If the offset type is determined to be an edge type (S702-b), the offset processing unit 30 determines whether the restored pixels of the encoding unit form the direction and shape of the edge formed with the neighboring pixels or the difference / variation between the restored pixel and neighboring pixels, The offset between the restored pixels and the pixels of the original image can be determined.

The offset processing unit 30 can determine an offset class for each of the restored pixels according to the offset type of the encoding unit (S703). In the edge type, the offset processing unit 30 can determine an edge class for each reconstruction pixel in an encoding unit. Here, the edge class 410 (see FIG. 4A) may include information about the direction of the edge that the reconstructed pixel forms with neighboring pixels, and in particular, the direction of 0 DEG, 90 DEG, 45 DEG, Lt; / RTI > That is, the first edge class 411 represents the edge direction of 0 占 the second edge class 412 represents the edge direction of 90 占 the third edge class 413 represents the edge direction of 135 占, The fourth edge class 414 may represent an edge direction of 45 degrees. The neighboring pixels may include at least one of left, right, top, bottom, or pixels adjacent to each corner based on the restored pixel. The position of the neighboring pixel may be determined in consideration of the edge direction according to the edge class. The neighboring pixels may be consecutive N pixels based on the restored pixel. Where N may be an integer greater than or equal to one. The N may be set in the image encoding apparatus or may be variably set in consideration of the filter type, the filter strength, the size / shape of the encoding unit, and the like.

In step S704, the offset processing unit 30 can set the edge category 420 based on the edge type that the reconstruction pixel of the encoding unit forms with the neighboring pixels. For example, the offset processing unit 30 sets the first edge category 421 when the edge shape that the reconstruction pixel forms with neighboring pixels indicates a local valley of concave, Is set to the second edge category 422 when the curve corner of the convex edge is indicated and to the third edge category 423 when the curve corner of the convex edge is indicated and the local peak ) Is set to the fourth edge category 424.

In step S705, the offset processing unit 30 may determine the offset value using the difference value between the restored pixel and the original pixels, for the restored pixels that belong to the same edge category in the encoding unit. That is, for each edge category, the average of the difference values between the restored pixel and the original pixel, that is, the average error of the restored pixels, can be determined as the offset value of the corresponding edge category.

For example, when the offset type of an encoding unit is an edge type and the restored pixels are classified into four categories according to the edge type, the offset correcting unit 31 calculates the average error between the restored pixel belonging to each of the four edge categories and the original pixel The four edge offset values calculated based on the four edge offset values can be determined.

Next, the offset processing unit 30 can encode the offset value in units of the edge class and the edge category. The encoding may further include rearranging the generated offset values. The rearrangement may be performed considering at least one of whether the offset value is a predetermined constant or the size of the offset. The predetermined constant may be a fixed value (for example, " 0 ") pre-assigned to the image encoding apparatus. The offset processing unit 30 encodes the information necessary for the reordering and outputs the encoded information.

For example, the offset processing unit 30 may encode the offset value 500 illustrated in FIG. 5A. At this time, the offset value 520 of the edge category may exist in various ways, and the offset value 520 of the edge category 510 may be a value of " 0 ". Accordingly, when the offset value 520 is aligned according to the order of the edge categories, the edge category 521 having an offset value of " 0 " may cause the bit string to increase in size. In consideration of this, the offset processing unit 30 arranges the edge category 531 having the offset value other than " 0 " relatively forward, and the edge category 521 having the offset value of " 0 & (S705).

In step S706, the offset processing unit 30 encodes the offset value of the edge category 531 having an offset value other than "0", and the offset value of the edge category 521 having the offset value of "0" It can be encoded so as not to be included.

On the other hand, when the offset type is determined to be a band type (S702-c), the offset processing unit 30 can set a predetermined band in consideration of the total range of pixel values in the encoding unit. That is, when the total range of pixel values of the encoding unit is divided into a predetermined number of consecutive pixel value intervals, each pixel value interval can be set to a band. On the basis of this, the offset processing unit 30 can confirm the band of the section in which the pixel values continuously exist, and set information about the starting point of the band (S707).

For example, if the pixel value is an 8-bit sample, the total range of pixel values in the encoding unit is 0 to 255, and the pixel value can be divided into a total of 32 bands 450 (see FIG. 4B). In this case, a predetermined number of bands to which the pixel values of the restored pixels belong may be determined from a total of 32 bands 450. Accordingly, the offset processing section 30 can set the starting position (left starting point) of the continuous predetermined number of bands to the band starting point 451. This band start point can be determined using a band index value of 0 to 31. [

In step S708, the offset processing unit 30 may set a predetermined number of band categories 455 according to the positions of the bands to which the pixel values of the reconstruction pixels in the encoding unit belong. For example, according to the band index of consecutive m (e.g., four) bands from the band start point 451, the restored pixels may be classified into m band categories 455. [ For each restoration pixel of the coding unit, the offset correcting unit 31 determines which band category belongs to m (for example, four) band categories depending on which band among m (for example, four) bands belongs And this value can be set to the value of the band category 455. [

In step S709, the offset processing unit 30 can set an offset value in units of a band category (455). That is, the offset processing unit 30 can determine an average error value between the restored pixels belonging to each band category 455 and the original pixels as the offset of the corresponding band category 455.

Next, an offset value reflecting the band start point and the band category can be generated and encoded. The encoding may further include rearranging the offset value, as described in the edge type.

For example, the offset processing unit 30 can encode the offset absolute value 561 and the code value 562 of each band category 550 in the order of the band start point and the band category. At this time, the offset absolute value 561 and the sign value 562 of the band category may exist in various ways, and the offset absolute value 561 of the band category 550 may be " 0 ". Accordingly, when the offset absolute value 561 is aligned in the order of the band category, the problem arises that the bit string is increased in size by the band category 571 having an offset value of " 0 ". In consideration of this, the offset processing unit 30 arranges the band category 571 having the offset value other than " 0 " relatively forward and locates the band category 572 having the offset value " 0 & (S710).

In step S711, the offset processing unit 30 encodes the offset absolute value and the sign value of the band category 571 having an offset value other than " 0 ", and determines the offset of the band category 572 having the offset value of & The value can be encoded so that it is not included in the bit stream.

As described above, since the offset value of the category having the offset value of " 0 " is not included in the bit string, the number of bits consumed for encoding the encoded value of " 0 " can be saved and the encoded data efficiency can be increased .

Furthermore, the offset processing unit 30 according to the embodiment of the present invention can variously change the number or types of edge categories or band categories so that the number of edge categories or band categories having an offset value of " 0 & have.

For example, if the number of pixels corresponding to the edge category or band category is small enough, then the pixel has a high probability that the gain for the offset is not very high. That is, it is meaningful only when the gain of the image quality improved by the offset is relatively larger than the bit amount necessary for transmitting the offset. Taking this into consideration, if the number of pixels included in the corresponding category (edge category or band category) is sufficiently small, the offset value for the corresponding category (edge category or band category) can be set to 0 and encoded.

Specifically, in step S706 or S710, the offset processing unit 30 confirms the number of pixels included in the corresponding category (edge category or band category), and when the number of pixels included in the category is equal to or smaller than a predetermined threshold value, The encoded value of the category can be set to " 0 ". At this time, the offset processing unit 30 determines an optimum value by using a fixed predetermined threshold value or considering the relationship between the image quality gain by the offset amount and the encoding bit amount of the offset information, and encodes the determined optimum value You may.

In addition, the offset processing unit 30 may not encode the optimal value and may derive the optimal value using a method of deciding the optimal value.

8 is a flowchart showing a procedure of an offset information restoration method according to an embodiment of the present disclosure.

The offset information decoding method according to an embodiment of the present invention may be performed by the offset information restoration unit 60 described above).

The offset information reconstruction unit 60 confirms an offset type (e.g., SAO type) from the encoded information (S801). That is, the offset information restoring unit 60 can confirm the offset type by checking the identifier identifying the Off type, Edge type, or Band type.

If offset coding is not performed (S802-a), the offset information restoring unit 60 completes decoding of the offset information for the coding unit.

In the case of the edge type (S802-b), the offset information restoration unit 60 can restore the information about the edge class and the offset value in units of the edge category.

At this time, the offset value of the edge category unit is encoded only in the offset value of the edge category having an offset value other than " 0 ", and the offset value of the edge category having the offset value of " 0 " Accordingly, the offset information restoring unit 60 restores the offset value of the edge category having an offset value other than " 0 " (S803).

Next, the offset information restoration unit 60 sets the offset value of the category not included in the bit string to " 0 ", and rearranges the offset value of the edge category to the order of the edge category (S804). The reordering may be performed based on the reordering related information signaled by the image encoding apparatus. Accordingly, the offset information restoration unit 60 can confirm the offset value of the rearranged edge category in accordance with the order of the edge category.

Thereafter, the offset information restoration unit 60 can restore the information about the edge class (S805). The offset information restoring unit 60 may restore the pixel value of the corresponding pixel by reflecting the edge class and the offset value of each edge category to each pixel (S806).

On the other hand, in the case of the band type (S802-c), the offset information restoration unit 60 can decode the offset value of the band start point and the band category unit.

Only the offset value of the band category having an offset value other than " 0 " is coded and the offset value of the band category having the offset value of " 0 " It is not included in the bit string. Accordingly, the offset information restoration unit 60 can restore the offset value of the band category having an offset value other than " 0 " (S808).

In step S809, the offset information restoration unit 60 sets the offset value of the category not included in the bit string to " 0 ", and the offset value of the band category having the offset value other than " 0 " The band category value is rearranged to correspond to the order of the band category. The reordering may be performed based on the reordering related information signaled by the image encoding apparatus.

In addition, the offset information reconstruction unit 60 may check the information on the band starting point from the encoded information (S810).

Then, the offset information restoring unit 60 may restore the value of the corresponding pixel by applying the offset value of the band start point and the band category (S811).

Although the exemplary methods of the present invention are represented by a series of acts for clarity of explanation, they are not intended to limit the order in which the steps are performed, and if necessary, each step may be performed simultaneously or in a different order. In order to implement the method according to the present invention, the illustrative steps may additionally include other steps, include the remaining steps except for some steps, or may include additional steps other than some steps.

The various embodiments of the present invention are not intended to be all-inclusive and are intended to illustrate representative aspects of the present invention, and the elements described in the various embodiments may be applied independently or in a combination of two or more.

Furthermore, various embodiments of the invention may be implemented by means of hardware, firmware, software, or a combination thereof. In the case of hardware implementation, one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays A general processor, a controller, a microcontroller, a microprocessor, and the like.

The scope of the present invention includes software or machine-executable instructions (e.g., operating system, applications, firmware, programs, etc.) that cause an operation in accordance with the methods of the various embodiments to be performed on a device or computer, Instructions, and the like are stored and are non-transitory computer-readable medium executable on the device or computer.

Claims (20)

A method of encoding image data,
Identifying a plurality of offset units;
Determining offset information for each of the plurality of offset units;
Encoding the offset information for each of the plurality of offset units and encoding the offset information for some offset units of the plurality of offset units,
Wherein the step of encoding the offset information comprises:
Arranging the plurality of offset units in descending order based on the offset information;
And encoding only offset information in an offset unit having an offset value other than " 0 " out of a plurality of offset units arranged in descending order. The method according to claim 1,
The partial offset unit includes:
Is an offset unit having an offset value other than " 0 ". The method according to claim 1,
Wherein the plurality of offset units include the partial offset unit and the residual offset unit,
Wherein the residual offset unit is an offset unit having an offset value of " 0 ". delete The method of claim 1, wherein the encoding of the offset information comprises:
Determining a number of pixels included in the plurality of offset units;
Aligning the pixels in descending order based on the number of pixels included in the plurality of offset units;
And encoding only the offset information for an offset unit in which the number of pixels included in the plurality of offset units exceeds a predetermined threshold value. 6. The method of claim 5,
Wherein the coding rate is set in consideration of rate-distortion of the image coding or is a predetermined fixed value. The apparatus of claim 1,
Edge category or band category of the image. An apparatus for encoding video data, the apparatus comprising:
An offset correcting unit for identifying a plurality of offset units and confirming and providing offset information for each of the plurality of offset units;
And an offset encoding unit encoding the offset information for each of the plurality of offset units provided from the offset correcting unit and encoding the offset information for some offset units of the plurality of offset units,
Wherein the offset-
Arranging the plurality of offset units in descending order based on the offset information,
Wherein only the offset information of the offset unit having an offset value other than " 0 " out of a plurality of offset units arranged in descending order is encoded. 9. The method of claim 8,
The partial offset unit includes:
Is an offset unit having an offset value other than " 0 ". 9. The method of claim 8,
Wherein the plurality of offset units include the partial offset unit and the residual offset unit,
Wherein the residual offset unit is an offset unit having an offset value of " 0 ". delete 9. The method of claim 8,
Wherein the offset correcting unit determines the number of pixels included in the plurality of offset units and provides the number of pixels to the offset encoding unit,
Wherein the offset coding unit arranges the pixels in descending order of the number of pixels included in the plurality of offset units and encodes only offset information for offset units in which the number of pixels included in the plurality of offset units exceeds a predetermined threshold value And outputs the offset information. 13. The method of claim 12,
Wherein the rate information is set in consideration of a rate-distortion of the image encoding, or is a predetermined fixed value. The apparatus of claim 8,
Edge category or a band category. A method for decoding coded image data,
Decoding the offset information for each of a plurality of offset units and decoding the offset information for some offset units of the plurality of offset units;
Decoding the offset information for a residual offset unit not included in some offset units among the plurality of offset units;
Providing offset information for the partial offset unit and the residual offset unit;
And restoring pixel information of an encoding unit by reflecting offset information for the partial offset unit and the residual offset unit,
Wherein the step of providing the offset information for the partial offset unit and the residual offset unit comprises:
Determining offset information in an offset unit having an offset value that is not " 0 " corresponding to the partial offset unit from the encoded image data;
Determining offset information in an offset unit having an offset value that is not " 0 " corresponding to the residual offset unit by a predetermined rule;
Rearranging the plurality of offset units based on the offset information;
And providing the offset information for the reordered plurality of offset units.
delete 16. The apparatus of claim 15,
Edge category or band category of the image. An apparatus for decoding coded image data, the apparatus comprising:
The method comprising: decoding the offset information for each of a plurality of offset units, decoding the offset information for some offset units of the plurality of offset units, and decoding the offset information for the remaining offset units not included in some offset units An offset information decoding unit decoding the offset information and providing the offset information;
And an offset correction unit for restoring pixel information of a coding unit by reflecting offset information for the partial offset unit and the residual offset unit,
The offset information decoding unit
And an offset information detector for detecting offset information in an offset unit having an offset value other than " 0 " corresponding to the partial offset unit from the encoded image data,
Restores offset information in an offset unit having an offset value that is not " 0 " corresponding to the residual offset unit by a predetermined rule,
And rearranges the plurality of offset units based on the offset information.
delete 19. The apparatus of claim 18,
Edge category or a band category.

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