KR102248172B1 - Method and apparatus for video encoding/decoding using image analysis - Google Patents

Abstract

Disclosed are a method and apparatus for encoding/decoding a video based on image characteristics according to image analysis. A video encoding method using image analysis includes: classifying a pixel included in a current block based on a predetermined band division; Analyzing an image characteristic of a current block by using the classification result for the pixel; And performing intra prediction on the current block according to the analysis result of the image characteristics. Accordingly, it is possible to improve coding efficiency and reduce complexity through intra prediction to which inversion motion is applied and in-loop filtering to which replacement values are applied to an image having an image characteristic different from a natural image, such as a screen content.

Description

Video encoding/decoding method and apparatus using image analysis {METHOD AND APPARATUS FOR VIDEO ENCODING/DECODING USING IMAGE ANALYSIS}

The present invention relates to video encoding/decoding, and more particularly, to a method and apparatus for encoding/decoding a video based on image characteristics according to image analysis.

As a next-generation video compression standard technology known to have a compression efficiency of about twice or more compared to the conventional H.264/AVC, the standardization of High Efficiency Video Coding (HEVC) has been progressed and has been recently completed.

HEVC defines a coding unit (CU), a prediction unit (PU), and a transform unit (TU) having a quadtree structure, and is a sample adaptive offset (SAO). Offset) and in-loop filters such as deblocking filters are applied. In addition, compression coding efficiency is improved by improving existing intra prediction and inter prediction.

In the case of conventional intra prediction, it is difficult to perform accurate prediction according to the characteristics of an image. In particular, when a prediction block is generated by an extrapolation method, there is a disadvantage in that the accuracy of prediction decreases as the distance between the prediction pixel and the reference pixel increases.

In addition, when a pattern, such as a certain shape and line, is repeatedly displayed in the screen, accurate prediction cannot be performed with the existing intra prediction. To overcome this problem, prediction is performed using motion search and compensation in the same manner as the block matching algorithm used in inter prediction, or a template constructed using neighboring reference pixels of the current block is used. Using this, motion search and compensation can be performed. Furthermore, when it is performed using another method having a similar purpose to the above-mentioned methods, the accuracy of the prediction can be improved.

For example, in the case of the block matching algorithm, the optimal encoding cost (SAD (sum of absolute) is based on the similarity between pixels by searching and compensating for motion in the current block unit in the region where the encoding and decoding is completed before the current block. difference), sum of absolute transformed difference (SATD), sum of the squared difference (SSD), or other methods may be used, and similarity and occurrence between pixels in a rate-distortion method such as rate distortion optimization (RDO) A method of inducing cost in consideration of bits and the like may be used.

However, when a prediction block is generated using motion search and compensation as a method of intra prediction, the accuracy of prediction may be degraded in a region having characteristics of some images such as screen content.

In addition, there is a problem that the efficiency of the SAO technique is deteriorated in a region having characteristics of some images such as screen content.

An object of the present invention for solving the above problems is to provide a method of adaptively encoding and decoding a video through analysis of an image.

Another object of the present invention for solving the above problems is to provide an apparatus for adaptively encoding and decoding a video through analysis of an image.

A video encoding method using image analysis according to an embodiment of the present invention for achieving the above object includes: classifying a pixel included in a current block based on a preset band division; Analyzing an image characteristic of a current block by using the classification result for the pixel; And performing intra prediction on the current block according to the analysis result of the image characteristics.

Here, in the step of classifying the pixels included in the current block, the classification result for the pixel may be calculated in the form of an index map including information on a band to which the luminance of the pixel belongs and information on the frequency occupied by the band. have.

Here, analyzing the image characteristics of the current block may include at least one of whether an edge exists in the current block, whether the current block is a background area, or whether the current block is a screen content area, based on the classification result for the pixel. One can be analyzed.

Here, in the performing of intra prediction on the current block, the intra prediction is performed on the current block by determining whether to apply reverse motion to intra prediction according to block matching or template matching based on the analysis result of the image characteristics. can do.

Here, in the step of performing intra prediction on the current block, when an edge exists in the current block or when the current block is a screen content area, intra prediction may be performed on the current block by applying an inversion motion.

Here, the method may further include performing in-loop filtering on the reconstructed block reconstructing the current block according to the analysis result of the image characteristic.

Here, in the performing of the in-loop filtering, filtering may be performed using a sample adaptive offset (SAO) or a substitute value.

Here, in the performing of the in-loop filtering, when an edge exists in the current block or when the current block is a screen content area, filtering may be performed by applying a replacement value to a reconstructed block reconstructing the current block. have.

A video decoding method using image analysis according to an embodiment of the present invention for achieving the above object includes: determining a decoding method for a current block according to an analysis result of an image characteristic of the current block; And performing intra prediction on the current block by determining whether to apply the inversion motion based on a decoding method for the current block according to the analysis result of the image characteristics.

Here, the analysis result of the image characteristics may be calculated by analyzing at least one of whether an edge exists in the current block, whether the current block is a background area, and whether the current block is a screen content area.

Here, in the performing of intra prediction on the current block, the intra prediction is performed on the current block by determining whether to apply reverse motion to intra prediction according to block matching or template matching based on the analysis result of the image characteristics. can do.

Here, in the step of performing intra prediction on the current block, when an edge exists in the current block or when the current block is a screen content area, intra prediction may be performed on the current block by applying an inversion motion.

Here, the method may further include performing in-loop filtering on the current block based on a decoding method for the current block according to a result of analyzing the image characteristics.

Here, in the performing of the in-loop filtering, filtering may be performed using a sample adaptive offset (SAO) or a substitute value.

Here, in the performing of the in-loop filtering, when an edge exists in the current block or when the current block is a screen content area, filtering may be performed by applying a substitute value to the current block.

In order to achieve the above object, a video decoding apparatus using image analysis according to another embodiment of the present invention includes an entropy decoder that calculates information on a decoding method for the current block according to an analysis result of an image characteristic of the current block. Wow; And an intra prediction unit that performs intra prediction on the current block by determining whether to apply the inversion motion based on a decoding method for the current block according to the analysis result of the image characteristics.

In order to achieve the above object, an apparatus for performing image analysis according to another embodiment of the present invention includes: a pixel classifying unit for classifying pixels included in a current block based on classification of a preset band; An image analysis unit that analyzes an image characteristic of a current block by using the classification result of the pixel; And a mode addition determination unit that determines whether addition of a new mode is necessary according to a result of analysis of the image characteristics.

Here, the mode addition determination unit, when an edge exists in the current block or when the current block is a screen content area, whether to perform intra prediction on the current block by applying a reversal motion, a sample adaptive offset (SAO: Sample Adaptive Offset) or alternative values can be used to determine whether to apply filtering.

In the video encoding/decoding method using image analysis according to the present invention as described above, an image having an image characteristic different from a natural image, such as a screen content, is subjected to intra prediction by applying inversion motion and in-loop filtering by applying a substitute value. It is possible to improve coding efficiency and reduce complexity.

1 is a block diagram illustrating an apparatus for performing image analysis according to an exemplary embodiment of the present invention.
2 is an exemplary diagram illustrating an index map generated through pixel analysis according to an exemplary embodiment of the present invention.
3 is an exemplary diagram for explaining a case where there is an inversion in a part of an image according to an embodiment of the present invention.
4 is an exemplary diagram for explaining an arrangement of pixels when there is an inversion in an image according to another exemplary embodiment of the present invention.
5 is an exemplary diagram for explaining motion estimation in case of having an inversion image characteristic according to an embodiment of the present invention.
6 is an exemplary diagram for explaining an analysis of image characteristics according to an embodiment of the present invention.
7 is an exemplary diagram for explaining an image characteristic according to an embodiment of the present invention based on pixel orientation.
8 is an exemplary diagram for explaining an additional mode setting based on pixel band classification according to an embodiment of the present invention.
9 is an exemplary diagram for describing a sample adaptive offset technique.
10 is an exemplary diagram for describing in-loop filtering according to an embodiment of the present invention.
11 is an exemplary diagram for explaining parameters used for in-loop filtering according to an embodiment of the present invention.
12 is an exemplary diagram for explaining in-loop filtering according to another embodiment of the present invention.
13 is an exemplary diagram for describing in-loop filtering according to another embodiment of the present invention.
14 is a block diagram illustrating a video encoding apparatus using image analysis according to an embodiment of the present invention.
15 is a block diagram illustrating a video decoding apparatus using image analysis according to an embodiment of the present invention.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention. In describing each drawing, similar reference numerals have been used for similar elements.

Terms such as first, second, A, and B may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. The term and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. It should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof does not preclude in advance.

Unless otherwise defined, all terms used herein including technical or scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in the present application. Does not.

The video encoding apparatus (Video Encoding Apparatus) and the video decoding apparatus (Video Decoding Apparatus), which will be described later, include a personal computer (PC), a notebook computer, a personal digital assistant (PDA), and a portable multimedia player (PMP). : Portable Multimedia Player), PlayStation Portable (PSP), Wireless Communication Terminal, Smart Phone, TV application server and service server. It is a user terminal or a communication device such as a communication modem for performing communication with a wired/wireless communication network, a memory for storing various programs and data for inter- or intra-screen prediction for encoding or decoding an image, or for encoding or decoding an image, and executing a program Thus, it may mean various devices including a microprocessor for calculation and control.

In addition, the image encoded as a bitstream by the image encoding device can be transmitted through wired or wireless communication networks such as the Internet, short-range wireless communication network, wireless LAN network, WiBro network, mobile communication network, etc. in real time or non-real time, or through a cable or a universal serial bus (USB: Universal Serial Bus) can be transmitted to an image decoding device through various communication interfaces, decoded by the image decoding device, and reconstructed and reproduced as an image.

In general, a moving picture may be composed of a series of pictures, and each picture may be divided into a predetermined area such as a frame or a block. When a region of an image is divided into blocks, the divided blocks may be largely classified into an intra block and an inter block according to an encoding method. Intra block refers to a block that is coded using an intra prediction coding (Intra Prediction Coding) method.Intra prediction coding is a block using pixels of previously coded, decoded, and reconstructed blocks in the current picture performing the current coding. This is a method of generating a prediction block by predicting a pixel of the current block and encoding a difference value from the pixel of the current block. Inter-block refers to a block that is coded using Inter Prediction Coding.Inter-prediction coding refers to one or more past pictures or future pictures to predict a current block in a current picture, thereby generating a prediction block. This is a method of encoding the difference between and. Here, a frame referred to when encoding or decoding a current picture is referred to as a reference frame. In addition, those of ordinary skill in the art to which the present embodiment pertains that the term "picture" described below may be substituted with other terms having an equivalent meaning such as image, frame, and the like. When you grow up, you can understand. In addition, it can be understood by those of ordinary skill in the art to which the present embodiment belongs that the picture referred to in the present invention means a reconstructed picture.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating an apparatus for performing image analysis according to an exemplary embodiment of the present invention, and FIG. 2 is an exemplary diagram illustrating an index map generated through pixel analysis according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the apparatus 10 for performing image analysis according to an embodiment of the present invention includes an image characteristic candidate selection unit 11, a pixel classification unit 12, an image analysis unit 13, and a mode addition determination unit. (14), an additional mode execution unit 15, an additional mode identification flag and a related parameter encoding unit 16 are included.

In addition, the apparatus 10 for performing image analysis according to an embodiment of the present invention may be implemented by being included in a video encoding apparatus.

The image characteristic candidate selector 11 may select an image belonging to a coding unit having a predetermined size from among a preset image characteristic candidate group, and select whether to set an additional mode in consideration of this.

Here, the image characteristic candidate group can be set in various ways, for example, whether or not an edge exists, whether or not it belongs to a background, whether or not an object exists, or an artificial image (computer graphic, computer capture screen). Etc.), whether it is a natural image, and whether or not it belongs to a character or figure.

If the image characteristic candidate to be considered among the various image characteristic candidate groups is 1. whether the region belongs to the background or not and 2. whether it is an artificial image or not, 1 and 2 are performed through the process of the pixel classification unit 12 and the image analysis unit 13, etc. If is true (that is, it belongs to the background and belongs to the artificial image), the process of applying a new in-loop filtering that can be well applied to the artificial image belonging to the background to the existing filter (existing mode) is set as an additional mode. Among these, an optimal filter can be applied.

In addition, if the image characteristic candidate to be considered among the various image characteristic candidate groups is 1. whether or not an artificial image and 2. whether or not it is a text area, this is also an existing image if 1 and 2 are true (ie, an artificial image and a text area) through the subsequent process. A new intra-prediction method that can be well applied to an artificial image including a character region can be added to the intra-screen prediction method of, and an optimal intra-prediction method can be applied among them.

In addition to the image characteristic candidate group described above, various characteristics may be included, and the range of additional modes considered according to the image characteristic candidate can be applied to a prediction unit, a transform unit, a quantization unit, and an in-loop filter unit to be described later.

In addition, information on an additional mode (or an image characteristic candidate selection flag) considered in association with the image characteristic candidate may be transmitted in units such as a sequence, a picture, and a slice.

Preparatory work for analysis of the image characteristics selected by the image characteristic candidate selection unit 11 is performed in the pixel classification unit 12. The pixel classifier 11 may classify pixels according to various criteria such as luminance, color difference, position, degree of gradient, correlation, or coefficient in a frequency domain of a pixel belonging to a coding unit having a predetermined size.

For example, the pixel classifier 12 may classify the pixels according to the luminance value of the pixels, or classify the pixels according to the transformation coefficient in the frequency domain, and use the luminance and color difference components of the pixels as one element. By configuring (for example, expressed in a vector format such as (Y, Cb, Cr) or (R, G, B)), pixels can be classified according to their displacement with neighboring pixels.

These criteria may be fixedly or adaptively applied depending on the resolution, quantization parameters, coding units and characteristics of the image. That is, the pixels included in the current block may be classified based on the preset band division.

For example, in the case of the luminance of a pixel, a zone may be divided into as many bands as 2n-k (k is a constant greater than 0 and less than n) according to the bit depth n of the pixel.

In addition, preset or transmitted information, quantization parameters, size of coding units, image resolution and parameters related to encoding (block division information, information related to prediction mode, information on the size of a transformation unit, coded block pattern, etc.) Thus, the brightness of the pixels may be classified for each band set. Here, the width of the band may have a uniform spacing, or may have an uneven spacing according to conditions such as image characteristics.

In addition, the number of bands may be an integer of 2 or more. For example, if pixels are classified according to luminance values in m bands (here, assuming that they have equal intervals), the frequency can be calculated according to which band belongs to each pixel.

An index map generated through pixel classification will be described with reference to FIG. 2.

For example, when one or more pixels belong to a certain band, NZ_i of the corresponding band may be classified as true, otherwise, it may be classified as false. In addition, it can be classified into a unit (Pi) such as a percentage of the frequency of pixels occupied by the corresponding band.

In addition, pixels can be classified according to two or more criteria. After classifying NZ_i of each band according to the luminance value of the pixel, a new index map may be constructed by allocating a new index to the corresponding band by considering only the band having a true value.

If NZ_i is true for bands 0 and m and the other bands are false, since only two candidate groups exist, 1 bit may be allocated and 0 and 1 may be allocated to each band. That is, a new index map can be constructed by assigning 0 to the index of band 0 and 1 to the m band.

The result of pixel classification may be stored in units of the index map in the form of a table generated through such classification.

In addition, classification is performed based on characteristics of one pixel, such as classification according to criteria such as luminance, color difference, position, etc. of pixels, or grouping them and performing classification according to the characteristics. It is also possible to classify according to correlation.

For example, there are various edge detection algorithms such as Sobel, Robert, Canny, etc. that are processed based on neighboring pixels. In this case, as for the neighboring pixels, pixels belonging to an M-sized block centered on the current pixel may be used for edge detection.

The image analysis unit 13 analyzes the characteristics of the image selected by the image characteristic candidate selection unit 11. The characteristics of the image may be variously performed according to the purpose of analyzing the image characteristics selected by the image characteristic candidate selection unit 11.

The image analysis unit 13 includes whether or not an edge exists, whether it belongs to a background, whether or not an object exists, whether it is an artificial image (computer graphic, computer capture screen, etc.) or a natural image, and whether it is a character or figure. It is possible to analyze the image such as whether it belongs to the region or not.

For example, in order to check whether the edge exists in the region, the characteristic may be checked based on information transmitted through the pixel classification unit 12. The image analysis unit 13 may analyze information obtained through an edge detection algorithm of the pixel classification unit 12.

In detail, when it is determined that N or more pixels are edges, the image analysis unit 13 may calculate an analysis result that the corresponding region has an edge. If not, the analysis result can be calculated as the edge does not exist in the corresponding region.

In addition, when it is determined that N or more pixels are identified as edges and have continuity, an analysis result may be calculated as the corresponding region has an edge. An example of continuity can be understood with reference to the description of FIG. 6 to be described later.

After classifying the band according to the luminance component of the pixel from the pixel classifying unit 12, the image analyzing unit 13 may analyze whether or not the corresponding region belongs to the background by using information on NZ_i.

For example, only when the sum of NZ_i has a value of N or less, the analysis can be performed with the criterion of background. If the sum of NZ_i has a value less than or equal to N, a result that the corresponding region is a background may be calculated, and otherwise, a result that it is not a background may be calculated.

Furthermore, the image analysis unit 13 may analyze an image from two or more pieces of information. That is, after analyzing different image characteristics from one piece of information, a new analysis result may be obtained through each image analysis result. For example, in order to analyze whether a corresponding region contains a character part, when the pixel classification unit 12 classifies it into a band according to the luminance component of the pixel, an analysis is performed using information about NZ_i and information about Pi. can do. In this case, whether NZ_i is a character part can be defined as a character part only when NZ_i is N or less (here, set to 2) and Pi of a band having the least frequency is less than Th. Therefore, by combining the analysis results according to each condition, if both conditions are true, the analysis result that the corresponding area contains letters, and if any of them are false, the analysis result that the corresponding area is not a text area. Can be calculated.

The mode addition determination unit 14 may determine whether to add a new mode based on one or more analysis results transmitted from the image analysis unit 13 and then determine whether to support the additional mode according to the result.

For example, when deciding whether to generate additional information related to reverse motion, which will be described later, first determine whether it is an image area with a possibility of reversal motion, and then, if it is determined that there is a possibility of reversal motion, the reverse motion related mode is selected. In addition, if it is determined that it is not, the same algorithm as before can be performed.

In order to confirm that there is a high possibility of reversal motion, the mode addition determination unit 14 determines whether an edge exists from the image analysis unit 13 or a figure (here, it is assumed that it is a specific area including a vertex of a rectangle). You can receive analysis results such as whether the area belongs to or not.

The additional mode execution unit 15 confirms that there is a high possibility of reversal motion from the mode addition determination unit 14 and, when it is decided to add a new prediction mode, performs encoding by applying a new prediction mode taking into account the reversal motion. can do.

The additional mode identification flag and related parameter encoder 16 may transmit an additional mode identification flag generated by adding a new prediction mode in the additional mode execution unit 15 and related parameters.

For example, a new prediction mode, such as a block matching algorithm to which inversion motion is applied, has been added, and if such an algorithm is optimal, inversion motion-related information and motion vector-related information may be transmitted together accordingly.

In the above example, only a description related to the reversal motion is presented, but other cases will be described through the following embodiments.

3 is an exemplary diagram for explaining a case in which a part of an image is inverted according to an embodiment of the present invention, and FIG. 4 is a diagram for explaining a pixel arrangement when an image is inverted according to another embodiment of the present invention 5 is an exemplary diagram for explaining motion estimation in case of having an inversion image characteristic according to an exemplary embodiment of the present invention.

Referring to FIG. 3, unlike a general natural image, a screen content image may have an inversion characteristic.

In detail, the image shown in FIG. 3 may have characteristics such as left and right inversion and vertical inversion.

For example, in FIG. 3, a1<->a2 and b may have a characteristic of being inverted left and right, and a1<->a3 and c may have a characteristic of being inverted vertically. Furthermore, a1<->a4 and d may have a characteristic in which the top, bottom, left and right are reversed together.

However, it is difficult to select a region having such a reversal characteristic as a prediction block by conventional motion search and compensation, although the value of using it as a prediction block is high. If motion search and compensation are performed through transformations such as left-right inversion and vertical inversion, since more accurate motion search and compensation is possible, encoding efficiency can be increased.

The arrangement of pixels will be described with reference to FIG. 4 as follows.

4A shows a general arrangement of pixels. If the motion search is performed by performing vertical inversion, prediction may be performed by performing pixel rearrangement in the scan order as shown in FIG. 4B.

4(c) and 4(d) show the case of left-right inversion and vertical-left-right inversion, respectively. When motion prediction is performed through the configuration of a target block through such pixel rearrangement (ya yb, yc, yd) and a candidate having an optimal coding efficiency is selected, the motion vector except for FIG. 4(a) Compensation of the current block may be performed through the pixel inverse rearrangement (yb, yc, yd ya) of the corresponding block.

In the case of a block in which the inversion has occurred, the decoder may perform compensation of the current block through inverse relocation of pixels of the block corresponding to the motion vector. 4 is only a partial example of the case inversion, and the present invention also includes modifications for similar purposes.

In addition, the same prediction may be performed by transmitting the information about the application to the inversion based on information previously determined on both sides so that the encoder and the decoder perform the same operation, or by transmitting the inversion information in units such as a picture, a slice, or a block. For example, an inversion candidate to which inversion can be applied may be set in advance according to the block size, or inversion may not be applied according to the block size.

For example, if a method of generating a prediction block using motion search and compensation as a method of intra prediction, and generating a prediction block through motion search and compensation by reversal is used, in an area having some characteristics of the image Encoding efficiency can be improved.

When motion search and compensation are performed by applying inversion, a prediction vector to be used for motion vector prediction may be set through various methods for the purpose of reducing data during motion vector encoding.

The motion search and compensation will be described with reference to FIG. 5 as follows.

A block or a motion vector of blocks that has been most recently coded through motion search and compensation may be selected as a candidate for the prediction vector (A in FIG. 5).

In addition, the relative position of the fixed coordinates (for example, the upper left coordinate of the left block or the upper left coordinate of the upper block) with the current block (if the horizontal and vertical blocks are v and w, respectively (-v, 0), (0, -w)) can be selected as a candidate group for the prediction vector (B in FIG. 5).

In addition, a block or a motion vector of blocks encoded through motion search and compensation to which the most recently inversion has been applied may be selected as a candidate for the prediction vector. A relative position with the current block may be selected as a candidate for the prediction vector (C in FIG. 5).

Also, upper left coordinates of a picture, a slice, or a block may be selected as candidates for the prediction vector. (D in Fig. 5)

Each of the prediction candidates described above can be configured in various combinations, and the priority for configuring the candidate group of the prediction vector may be determined according to preset conditions of the encoder and the decoding period, or in units such as sequence, picture, and slice. You can also set information about it.

For example, in FIG. 5, when A, B, C, etc. are possible as candidates for a prediction vector, only the candidates in C are used, candidates of C and B are used, or candidates of A and B are used. I can.

In the case of performing motion search and compensation in an area where encoding or decoding has been completed before the current block, if it is determined that there is a high possibility that a prediction block with motion by reversal exists according to a preset rule, inversion information is sent, otherwise it is omitted. can do.

For example, if it is 0, it may mean that existing motion search and compensation are performed without reversal, and additional information accordingly is also not required to be transmitted. In addition, if it is 1, it may mean that motion search and compensation with reversal are performed, and additional information on reversal accordingly is transmitted. However, when it is determined that the inversion information does not exist, even information such as 0 and 1 on whether the inversion information has been used may not be transmitted, and through this, the encoding performance can be improved.

6 is an exemplary diagram for explaining an analysis of image characteristics according to an embodiment of the present invention.

Referring to FIG. 6, the image analysis unit 13 may receive NZ_i and an index map from the pixel classification unit 12 and perform analysis on whether the image is a solid segmented area or a complex area. FIG. 6(a) shows a solid divided area, and FIG. 6(b) shows a complex area.

There may be two conditions for determining as a solid segmentation area.

The first condition is that NZ_i must be smaller than k (assuming 5 here), and the second condition must satisfy the continuity condition of pixels in each area, and that the pixels in each area must not be divided into two or more areas. It can be defined as having to satisfy the condition.

Here, the definition of continuity is as follows.

For example, pixels divided into respective bands as shown in area c of FIG. 6 (1) may have the same index map. Here, the definition of continuity is based on the relationship with neighboring pixels in a<x<a, -b<y<b (here, x, y are the position of the current pixel on the 2D plane) around the current pixel. It can be defined as being determined.

If, among the neighboring pixels in a<x<a, -b<y<b, there is even one pixel with the same index map as the current pixel, there is continuity, otherwise it is analyzed that there is no continuity. Can be calculated.

Therefore, in the case of region c of FIG. 6 (1) (here, the indexes of a, b, and c are assumed to be '0', '1', '2'), all pixels in the region having an index of 0 are continuous. And all the pixels with the index of '1' have continuity, and the analysis result that the pixels of the region with the index of '2' also have continuity, so that the pixels in all the corresponding areas have continuity. The analysis result can be obtained, and since there is no area divided into two or more areas, the analysis result can be obtained that the area is composed of solid divisions.

Compared to this, in the case of area c in Fig. 6(2) (here, the indexes of a, b, c, and d are assumed to be '0', '1', '2', '3'), 0, '1 It is possible to calculate an analysis result stating that all pixels in the region having the indices of', '2', and '3' have continuity.

However, since the remaining regions except for the region having the index of '3' are divided into two or more regions, this does not satisfy the above condition. Therefore, in this case, the first and second conditions are met, but the third condition is not met, so it is impossible to obtain an analysis that the corresponding region is composed of solid divisions.

As described above, conditions for image characteristics may be defined by a user. The analysis result can be obtained by checking all three conditions, and it is also possible to set to proceed to the step of confirming the next condition only when one condition is checked first and it is satisfied.

7 is an exemplary diagram for explaining an image characteristic according to an embodiment of the present invention based on pixel orientation.

Referring to FIG. 7, a case of performing an analysis on whether an area belongs to a figure (here, it is assumed that it is a vertex of a rectangle, that is, an area including a bent portion) will be described.

In order to analyze whether a region is a figure, information about an NZ_i of a band according to the pixel classification, an index map, and edge information may be received from the pixel classifying unit 12.

For example, the condition that NZ_i must be less than D, the condition that the pixels in each region must satisfy the continuity condition, the condition that N or more pixels turn out to be edges, and that L or more pixels have continuity in the edge index map. It can be defined as generating an analysis result saying that there is a possibility that it is a figure area when the condition and the condition that K or more break points exist are satisfied.

Assuming that all other conditions are satisfied, let's check the condition for the break point.

In the index map for the edges confirm the presence kkeokin point with respect to a pixel classified in (that here 0,1 only two assumptions, one assumes that this edge portion) to the edge, where the center A (the current pixel -a You can check the direction of the neighboring pixels in <x<a, -b<y<b).

If the direction is checked within -2<x<2 and -2<y<2, as shown in FIG. 5, several candidate groups such as 180 degrees, 135 degrees, 90 degrees, and 45 degrees can be placed. In addition, when directionality is confirmed in 3<x<3 and -3<y<3, candidate groups for more various directionalities can be added.

In addition, it is possible to check whether or not there is a broken point by checking the relationship with the directionality of the pixels classified as neighboring edges. If the difference in directionality between the pixel classified by the previously positioned edge and the current pixel (here, when the difference is calculated by an angle) is less than d, it can be said that a broken point has occurred, and otherwise, a broken point does not occur. For example, when d is set to 30 degrees, it is possible to calculate an analysis result that no break points occur because all cases of FIG. 7 are larger than 30. When d is set to 135 degrees, a result is obtained that the break point does not occur because Fig. 7 (a) does not satisfy the condition, whereas Figs. 7 (b), (c), and (d) satisfy the condition. I get the result that it occurred.

If you want to perform image analysis on the area to check whether it is the same area as the vertex of the square, in order to set conditions that can characterize it (for example, or when you want to know whether the area has the same shape), the area It can also be configured to obtain an analysis result such as true only if the break point occurs only once, and false if not.

In the case of a square shape, since the part to the break point will have an angle of 90 degrees, you can perform an analysis on this by changing the conditions in the area to check the break point above (break point occurs only when d is 90). have.

An example of adding a new mode from the above-described embodiment will be described in more detail as follows.

Referring back to FIG. 1, the image characteristic candidate selection unit 11 attempts to determine whether to put a new additional mode for intra prediction in consideration of whether it belongs to an artificial image and 2. a robust segmentation area. To this end, the pixel classifier 12 may receive NZ_i of a band for pixel classification, an index map, and the like.

The image analysis unit 13 may analyze whether a condition that NZ_i must be smaller than D, a continuity condition of pixels in each region, and a condition that pixels in each region should not be divided into two or more regions are satisfied. .

If the image analysis unit 13 satisfies all of the above conditions, an analysis result of a solid segmented area belonging to an artificial image may be calculated.

Through this, the mode addition determination unit 14 determines to add an intra prediction mode that exhibits performance in a region having a robust segmentation belonging to an artificial image in addition to the existing intra prediction mode.

8 is an exemplary diagram for explaining an additional mode setting based on pixel band classification according to an embodiment of the present invention.

Referring to FIG. 8, when pixels are classified by bands as shown in FIG. 8(a) and indicated by assigning a new index to a band in which NZ_i is true, the corresponding block is solidly segmented belonging to an artificial image. Let's say we got an analysis of the domain with

The additional mode execution unit 15 executes a new intra prediction mode in addition to the existing intra prediction mode. For example, a method of finding similar blocks in a previously coded region may be added through a block matching algorithm.

In addition, a method of copying neighboring pixels on a pixel or pixel basis may be added. 8(a), when the coordinates of the upper left side of the block are (0,0), the pixel at the position (1,0) is the pixel (0,0) before the scan (assuming it is a raster scan here). Since the index (0) with) is the same, mode information called CL (copy left) can also be transmitted. In the case of copying a value from a pixel above the current pixel, such as the position of (7,1), mode information called CT (copy top) can be transmitted to express this.

In addition, it is also possible to encode the number of repetitions in succession. In order to encode the first row in FIG. 8A, the index 0 that occurs first may be encoded, and the number of repetitive indexes that appear in succession may be encoded.

Here, the number of consecutive indexes may be limited in units of rows (index (0) + number of consecutive indices (7)), and may not be limited in units of rows (index (0) + number of consecutive indices (10)).

Also, multiple pixels can be copied. For example, since the pixels from (0,1) to (2,1) are the same as the pixels from (0,0) to (2,0), (CT(copy top), 3 (total number to be copied)) It can also be encoded in the same way as ). It is also possible to perform copying from additional directions other than CL and CT.

Also, since the pixels from (0,2) to (4,2) are the same as the pixels from (1,1) to (5,1), (CTR(copy top right), 5 (total number to be copied)) and The encoding can be performed in the same way.

In addition, copying may be performed in units of rows (or in units of columns depending on the scanning direction). For example, the 8th row ((0,7) to (7,7)) is the same as the 7th row ((0,6) to (7,6)), so the copy top line (CTL) and This can also be expressed by transmitting the same mode information.

In addition, in Fig.8(b), the pixels from (0,1) to (3,1) are the same as the pixels from (4,1) to (7,1), so that the CM (copy mirror) This can be expressed by transmitting mode information such as. For this, since the left and right lengths must be the same, this mode information can be encoded only at the middle start point of the row.

Another example of utilizing reversal is the case of Fig. 8(c). In Fig. 8(c), unlike Fig. 8(b), a lot of vertically inverted rows (from 2nd to 6th row) can be found. In the case of the basic scan direction (assuming that it is a raster scan), the pixel rearrangement as shown in FIG. 4 can be performed because encoding is impossible using inversion as described above.

That is, when pixel rearrangement such as rotation by 90 degrees as shown in FIG. 8(d) is performed, encoding may be performed using the aforementioned CM mode.

The above provides various examples of the intra prediction method, but is not limited to the above-described embodiments, and various examples of modifications having similar purposes may be included.

In addition, through the mode addition decision unit 14, the analysis on whether it belongs to an artificial image and 2. a solid segmentation area is transmitted from the image analysis unit 13, and whether a new intra prediction mode is added for this. As determined, it is possible to consider whether to add another mode.

When an analysis result of a robust segmented region belonging to an artificial image is obtained from the image analysis unit 13, a new mode for transform or quantization can be added as well as an intra-screen prediction method accordingly. have.

After performing the above-described new intra prediction, the existing transformation and quantization and the reverse process are performed, and the pixels in each band are mapped to one pixel representing the band without restoring the actual pixel values. Restoration can be performed by performing the process of doing so. In this case, the transformation or quantization process may be omitted. That is, not only a new intra prediction method is considered, but a new mode of transformation and quantization accordingly (e.g., not performing transformation, not performing quantization, not performing both, or adaptively performing transformation. Whether to decide whether to do or not, the addition of, etc.) may also be determined in the mode addition determination unit 14.

M1: New intra prediction + transformation + quantization

M2: New intra prediction + quantization

M3: New in-screen prediction

The addition of various combinations of modes as described above may be considered. In the case of M1, when a residual component is obtained through new prediction, a coefficient obtained by transforming and quantizing the residual component may be transmitted.

In the case of M2, the quantized coefficient of the actual pixel value may be transmitted after performing prediction for the index (2, 3) having the smallest frequency in Fig. 8(a), and prediction is performed only on the index (3) having the smallest frequency. Afterwards, the quantized coefficients of the actual pixel values may be transmitted.

In the case of M3, after performing prediction, pixels in each band are mapped to representative values of each band, so that coefficients for residual components are not separately transmitted, and encoding may be performed by transmitting information on representative values of each band.

In the above description, through the mode addition decision unit 14, the analysis of whether it belongs to an artificial image or not, and 2. a robust segmentation area, is performed through the image analysis unit 13 for encoding as in the above-described example. Although described, this is only an example and is not limited to the above case.

Referring to FIG. 7, a case of performing an analysis on whether an area belongs to a figure (here, it is assumed that it is a vertex of a rectangle, that is, an area including a bent portion) will be described.

In order to analyze whether a region is a figure, information about an NZ_i of a band according to the pixel classification, an index map, and edge information may be received from the pixel classifying unit 12.

For example, the condition that NZ_i must be less than D, the condition that the pixels in each region must satisfy the continuity condition, the condition that N or more pixels turn out to be edges, and that L or more pixels have continuity in the edge index map. It can be defined as generating an analysis result saying that there is a possibility that it is a figure area when the condition and the condition that K or more break points exist are satisfied.

As in the many examples described above, one or more image characteristics can be defined through various methods, and the definition of each image characteristic may follow the rules set in the encoder and decoder, or the information of the definition of the characteristic is generated by the encoder. Then, it can be transmitted to the decoder. That is, detailed information for each image characteristic may be divided and transmitted, and transmission units may be transmitted in units such as sequence, picture, slice, and block.

9 is an exemplary diagram for describing a sample adaptive offset technique.

Referring to FIG. 9, after the band offset is classified into bands having similar luminance values in a corresponding block, offsets are transmitted to four consecutive bands (transmission offset). The pixel value of the reconstructed image may be corrected by adding the transmitted offset value to the pixels in the band in which the offset is transmitted.

10 is an exemplary diagram for explaining in-loop filtering according to an embodiment of the present invention, FIG. 11 is an exemplary diagram for explaining parameters used for in-loop filtering according to an embodiment of the present invention, and FIG. 12 is It is an exemplary diagram for explaining in-loop filtering according to another embodiment of the present invention, and FIG. 13 is an exemplary diagram for explaining in-loop filtering according to another embodiment of the present invention.

Referring to FIG. 10, in the conventional case, in order to reduce an error with the original image data, a pixel unit offset is added to a pixel within a specific band of a luminance (or color difference) value. Can be replaced with a value in or near a specific band.

For example, in the case of some images (computer capture screens), unlike natural images, there are many cases that are classified into values near some luminance components and appear. Therefore, encoding performance can be improved by replacing values in a corresponding band with a specific band instead of pixel-by-pixel correction as shown in FIG. 10.

Specifically, unlike in the conventional case that information about the start position of a continuous band is transmitted to the decoder, information about the start position of a continuous band that performs filtering is transmitted and the start position of each individual band that performs filtering. It is optional among sending information about the reconstructed pixel and finding information about the start position of the continuous band performing filtering or the start position of each individual band performing filtering through the analysis of reconstructed pixels from the encoder and the decoder. Can be set to.

It may be promised to use the choice between sending the start position of a continuous band from the encoder and decoder, sending the start position of an individual band, or automatically finding the start position of the band through analysis of reconstructed pixels. , It is also possible to transmit the selection information in units of pictures, slices, and blocks. For example, if the bit depth is 8 and the width of the band is 8, the total number of bands is 32.

The information on the start position of the band may be an absolute position in the entire band or may be a relative position according to various conditions. For example, it may be a relative position from a position determined according to an image characteristic. In this case, the image characteristic is when pixels are concentrated in a certain band, the minimum or maximum value in the block before the in-loop filter is applied. The starting position of the band including the pixels of the block may be the reference, the starting position of the band having the average value of the luminance components of the pixels of the block may be the reference, and the starting position of the band with the highest frequency may be the reference. It could be.

In addition, the band width may also have various values rather than a fixed value. The band may be divided in proportion to the bit depth (for example, when the bit depth is 8, the width is 8), or may be divided into bands having an adaptive width according to the quantization parameter.

Furthermore, for more precise filtering (when the pixel value is corrected through offset) when the image characteristics are concentrated in a certain band, the bandwidth (e.g., when the conventional is 8, the size of less than 8) It is also possible to improve the performance of filtering (in this case, correction through pixel value offset) by reducing the width with ().

In the case of sending the start positions of individual bands, the positions of each band may be sent to an absolute position in the entire band, or position information may be sent through a relative difference value of each band. For example, the position information of each band can be sent to the absolute position of the entire band, the start position of the first band is sent to the absolute position of the entire band, and the start position of the second band is based on the start position of the first band. As a result, the relative difference may be transmitted as location information.

In addition, the location of each band may be a relative location according to various conditions. For example, a relative position from a position determined according to image characteristics may be exemplified. Here, when pixels are concentrated in a specific band, the image characteristic may be the start position of the band including the pixel having the minimum or maximum value in the block before applying the in-loop filter. It may be the start position of the band having the average value of the luminance component, or the start position of the band with the highest frequency.

In addition, it is possible to select several candidate groups for the starting position. Candidate group 1 may compare encoding costs such as an initial starting point in the entire band, and candidate group 2 may determine which point to generate start position information around by comparing encoding costs, such as a starting point of a band with the highest frequency of a corresponding block. If the candidate with the highest selectability among several candidate groups is set as the prediction candidate, and the actual start position and the candidate judged with the highest selectability match, 1 bit may be transmitted because it is true. Otherwise, the actual start position is excluded. Information on the remaining candidates may be generated and transmitted.

Filtering related parameters (offset or substitute value) are information to minimize errors between the reconstructed image of the corresponding band and the original image, and are transmitted for each band. It can be transmitted by selecting one of the methods. For example, it may be used mixed in units such as blocks, or only one method may be applied.

If the in-loop filter (here, SAO), various selection trees can be configured to perform filtering. Filtering may not be performed, correction may be performed through edge offset, correction may be performed through band offset, and correction may be performed through replacement values. It can also be done in a new way with a similar purpose.

The setting for this may be configured by an encoder and a decoder under an appointment, or by transmitting information on which selection tree is to be configured. That is, information about this can be transmitted in units of pictures, slices, and blocks.

For example, no filtering + edge offset, no filtering + band offset + edge offset, no filtering + edge offset + replacement value, etc. can be configured.

In addition, the probability of occurrence may be different according to the encoding parameters of the neighboring blocks. For example, if the in-loop filter is applied to all of the neighboring blocks with edge offsets, the current block also has a higher probability of applying correction through edge offsets. Therefore, the probability of generating edge offsets is set higher than other methods, and entropy encoding through this is more effective. By generating fewer bits, it is also possible to improve coding performance.

As another example, when an in-loop filter is applied as a band offset for the left block and an in-loop filter as a substitute value for the upper block, the occurrence frequency is defined in advance and the probability of each occurrence according to this combination can be set and entropy coding can be performed through this. have.

In addition, this can be set through other encoding parameters. If an in-loop filter is applied to the left block as a band offset and the upper block as a substitute value, a different probability of occurrence may be set by checking the prediction mode of the corresponding block (here, it is limited to the intra prediction mode).

If the prediction mode of the corresponding block coincides with one of the neighboring blocks, the probability of occurrence of the in-loop filter of the neighboring block may be increased. For example, if the prediction mode of the left block and the prediction mode of the current block are the same, the probability of occurrence of the band offset is increased, and if the prediction mode of the upper block and the prediction mode of the current block are the same, occurrence of a replacement value The probability is increased, and if neither is the case, a different probability of occurrence can be set.

In addition, different probability information may be set according to the type of picture, slice, or the like. For example, it is possible to set the probability information differently according to an inter picture or an intra picture.

Furthermore, by copying all or part of the parameter information of the in-loop filter of the neighboring block and using it, the amount of information of the in-loop filter parameter of the corresponding block can be reduced, thereby increasing encoding efficiency.

A parameter used for in-loop filtering according to an embodiment of the present invention will be described with reference to FIG. 11 as follows.

For example, suppose that a neighboring block uses a band offset and has parameter information as shown in FIG. 11 (a).

If the current block applies the in-loop filter through the band offset, if the parameter information of the neighboring block is '1' through a 1-bit flag indicating the entire copy, the in-loop filter parameter information is completely copied from the neighboring block.' In the case of 0', the parameter information of the current block can be obtained from the neighboring block by selecting one of not copying.

In addition, parameter information of the current block may be obtained from the neighboring block by partially copying the parameter information of the neighboring block. In this case, through a 1-bit flag, if '1', in-loop filter parameter information is partially copied from a neighboring block, and if '0', in-loop filter parameter information is not copied from a neighboring block.

If it is '1', the flag can be transmitted in a preset order to know what information is to be partially copied from the neighboring block. For example, if the information on the starting position of the band to which the filtering is applied means that the preceding flag is '1', it means that it is obtained from the neighboring block at the same time, a flag indicating whether to fetch the offset information for each remaining band. Can follow.

If all four offsets are to be copied from a neighboring block, a flag of 1-1-1-1 can be transmitted.

In addition, as shown in FIG. 11 (a), if all the remaining bands except the second band are to be copied from neighboring blocks, a flag of 1-0-1-1 can be transmitted, and in the case of the second band not copied The offset can be transmitted separately.

As another example, it is assumed that a neighboring block performs in-loop filtering through a substitute value, and a current block also performs in-loop filtering through a substitute value, and parameter information of the neighboring block is as shown in FIG. 11(b).

Even in this case, all of the in-loop filter parameter information can be copied from the neighboring block or partial copy can be performed.

If the current block applies the in-loop filter through the replacement value, if the parameter information of the neighboring block is '1' through a 1-bit flag indicating the entire copy, the in-loop filter parameter information is copied entirely from the neighboring block.' In the case of 0', the parameter information of the current block can be obtained from the neighboring block by selecting one of not copying.

In addition, parameter information of the current block may be obtained from the neighboring block by partially copying the parameter information of the neighboring block. In this case, through a 1-bit flag, if '1', in-loop filter parameter information is partially copied from a neighboring block, and if '0', in-loop filter parameter information is not copied from a neighboring block.

If it is '1', the flag can be transmitted in a predetermined order to know what information is to be partially copied from the neighboring block. If there are four bands to be filtered, a flag indicating whether or not to be copied can be transmitted for the start position of each band.

In addition, if all four bands want to copy the start position from a neighboring block, a flag such as 1-1-1-1 can be transmitted.

If the start positions of the remaining bands except the last are the same as shown in FIG. 11 (b), the 1-1-1-0 flag can be transmitted and the start position information for the remaining bands can be transmitted, and the replacement value is also the same as the above method. Can be transmitted through.

If all four bands have copied the start positions from neighboring blocks, a flag indicating whether to copy replacement values for the four bands may be transmitted (1-1-1-1 or 1-0-1-1).

11(b), if only 3 copies are made for the band start position and the start position is separately transmitted for the last band, the replacement value copy flag accordingly is sent only for the 3 bands where the band start position is copied. In the case of a band, an alternative value may be transmitted separately (1-1-1-0 <Band start position copy flag> ~~ 1-1-0 or 1-0-1, etc. <Band where the band start position copy flag is 1 Copy flags of the replacement values of >).

The above-described neighboring blocks may be blocks such as adjacent left, upper left, upper, and upper right, or may be constructed from various blocks such as non-adjacent blocks and co-located blocks adjacent in time. The neighboring block candidate group may be set according to a predetermined rule of an encoder and a decoder, or may be transmitted in units such as a picture or a slice. In addition, when there are two or more candidate groups, a flag of 1 bit or more may be transmitted.

A method such as fixed-length encoding or variable-length encoding (Exp-golomb, Truncated rice, etc.) can be applied to filtering-related parameters (offset or substitute value).

In addition, it is possible to set various starting positions for expressing related parameters. If it is set centered on the left side of the band, it can be set centered on the center of the band. The range for expressing the related parameter can be set in a limited range within the corresponding band, and it is also possible to set the range beyond the band.

In addition, it is also possible to express related parameters in a standard such as an average value or an intermediate value of the pixels in the corresponding band. Related parameters can be expressed by absolute values and signs, and by omitting signs depending on the starting position, they can be expressed only by absolute values.

When two or more bands are used, all bands may be corrected through offsets or all bands may be corrected through replacement values.

Referring to FIG. 12, it is also possible to adaptively perform correction through an offset or substitute value according to a band. Information about this may be shared according to the same setting of the encoder and the decoder, and may be transmitted in units of pictures, slices, and blocks.

Referring to FIG. 13, if it is determined that it is a special region of an image, correction through a substitute value is additionally added to the edge offset and band offset in the existing SAO, and if not, the edge offset and the band offset as before. Can only support.

For example, suppose that the image characteristic candidate selection unit selects whether or not it is a character region among several image characteristic candidate groups, and determines whether to put the additional mode in consideration of the additional mode in the existing SAO.

The pixel classification unit 12 classifies the bands according to the luminance component. In the image analysis unit 13, in order to determine whether or not a character region is a character region, the number of subbands in which NZ_i is true is greater than 1 to less than k, and as shown in FIG. Assume that it is determined that the character region (assuming that the difference between the luminance component of the character portion and the luminance component of the background portion is large) satisfies the condition that NZ_i is not a true subband) equal to or greater than TH.

In this case, if the analysis result that the block is actually a character area is highly likely to be generated from the mode addition decision unit 14 when the corresponding block satisfies the condition, the existing edge offset and band offset are in a mode called'correction through substitution values'. Is additionally executed, and if the corresponding block does not satisfy the condition, it is unlikely that it is a character area. Therefore, SAO is supported only with the existing edge offset and band offset, excluding correction through the replacement value.

When the optimum filter is determined by executing in the additional mode, parameters related thereto are transmitted through the additional mode identification flag and related parameter encoder 16.

The correction through the replacement value depends on the existing SAO and may be used together with the existing methods, or may be configured and used with another in-loop filter.

14 is a block diagram illustrating a video encoding apparatus using image analysis according to an embodiment of the present invention.

Referring to FIG. 14, a video encoding apparatus according to an embodiment of the present invention includes a subtraction unit 110, a transform unit 120, a quantization unit 130, an inverse quantization unit 131, an inverse transform unit 121, and an entropy. An encoding unit 140, an addition unit 150, an in-loop filter unit 160, a frame memory 170, an intra prediction unit 180, and a motion compensation unit 190 are included.

The subtraction unit 110 generates a residual image between the current image and the predicted image by subtracting a prediction image generated by intra prediction or inter prediction from a target image to be encoded (current image), which is a received input image.

The conversion unit 120 functions to convert the residual image generated by the subtraction unit 110 from the spatial domain to the frequency domain. Here, the transform unit 120 converts the residual image into the frequency domain by using a technique for transforming an image signal on the spatial axis into a frequency axis, such as Hadamard transform, Discrete Cosine Transform, and Discrete Sine Transform. Can be converted to

The quantization unit 130 quantizes the transformed data (frequency coefficient) provided from the transform unit 120. That is, the quantization unit 130 calculates a quantization result value by dividing and approximating the frequency coefficients, which are data transformed by the transform unit 120, by a quantization step size.

The entropy encoding unit 140 generates a bitstream by entropy encoding the quantization result value calculated by the quantization unit 130. In addition, the entropy encoding unit 140 may entropy-encode the quantization result value calculated by the quantization unit 130 using a CAVLC (Context-Adaptive Variable Length Coding) or CABAC (Context-Adaptive Binary Arithmetic Coding) technique. In addition, in addition to the quantization result value, information necessary for decoding an image may be entropy-encoded.

The inverse quantization unit 131 inverse quantizes the quantization result value calculated by the quantization unit 130. That is, the inverse quantization unit 131 restores a value (frequency coefficient) in the frequency domain from the quantization result value.

The inverse transform unit 121 restores the residual image by converting the frequency domain value (frequency coefficient) provided to the inverse quantization unit 131 from the frequency domain to the spatial domain, and the adder 150 performs intra prediction or inter prediction. A reconstructed image of the input image is generated by adding the residual image restored by the inverse transform unit 121 to the predicted image generated by the inverse transform unit 121 and stored in the frame memory 170.

The intra prediction unit 180 performs intra prediction, and the motion compensation unit 190 compensates a motion vector for inter prediction. Here, the intra prediction unit 180 and the motion compensation unit 190 may be collectively referred to as a prediction unit.

The prediction unit generates a prediction block of the current block through intra or inter prediction. In the case of intra prediction, a prediction block can be constructed in a region where the previous encoding or decoding of the current picture has been completed using an extrapolation method and a neighboring reference pixel using a DC or planar mode, or by using an algorithm such as a block matching algorithm and a template. An optimal prediction block can be determined in consideration of encoding cost.

Here, the region in which the encoding or decoding is completed may be composed of at least one block unit, may be divided into slice units, or may be composed of a region having a size limited in a direction in which encoding or decoding is completed based on the current block. , It may be configured as a region in which encoding or decoding is completed, which is placed horizontally or vertically of the current block.

The parameters related to the optimal prediction mode determined at this time are block division information, prediction method (information on whether to use an extrapolation method or a block matching method), prediction direction and motion information (in the case of extrapolation, which direction is used). In the case of whether or not, block matching, etc., a motion vector indicating how much a block or pixel unit of an arbitrary shape is to be generated from a block having a moving distance from a specific location defined by a current block or a current slice start point or by a specific method. Information, information on which candidate to select from the candidate list for multiple motion vectors), the composition of the candidate list (how many motion vectors to put as candidates, which motion vectors to put in the candidate group, etc.), motion search range (integer, 1/2, 1/4, 1/8, etc.), information for inducing a motion vector using a preset skip or merge or other method, etc. may be included.

In particular, the intra prediction unit 180 according to an embodiment of the present invention improves the accuracy of prediction when motion search and compensation is performed on a target block to which inversion of left and right and up and down is applied using a method such as a block matching algorithm and a template. I can make it. For example, the intra prediction unit 180 may perform intra prediction on the current block by applying an inversion motion when an edge exists in the current block or when the current block is a screen content area.

Whether to use a method such as a block matching algorithm and a template to which the inversion motion is applied may be set according to a setting previously promised to an encoder and a decoder, or may be transmitted in units of pictures, slices, and blocks. In addition, information on which inversion is to be supported can be shared according to settings previously promised to the encoder and decoder. In addition, information on which reversal is supported can be shared according to previously accumulated statistics (GOP unit, picture unit, etc.). Including the above-mentioned examples, other information related to inversion may be included in the optimal prediction mode related parameter and configured.

The in-loop filter unit 160 performs filtering on the reconstructed image, and may include a deblocking filter (DF) and a sample adaptive offset (SAO).

The in-loop filter unit 160 applies filtering to reduce an error between the reconstructed image data and the original image data. An offset value for correcting an error between the reconstructed image and the original image is calculated, and information about this is transmitted to the decoder. In the case of SAO, an offset in units of pixels is added to a picture to which a deblocking filter is applied. SAO is subdivided into a case where an error is corrected for an edge by subdividing pixel characteristics in a corresponding block (edge offset), and a case where an error is corrected for a specific luminance component value band (band offset, band offset). For the purpose of efficiently calculating and transmitting an offset, four offsets for a luminance component and a chrominance component may be transmitted in a coding unit.

Furthermore, the in-loop filter unit 160 may perform filtering by configuring various selection trees. That is, filtering may not be performed, correction may be performed through edge offset, correction may be performed through band offset, and correction may be performed through replacement values.

For example, the in-loop filter unit 160 may perform in-loop filtering on a reconstructed block from which the current block is reconstructed according to an analysis result of image characteristics. That is, the in-loop filter unit 160 may perform filtering by using a sample adaptive offset (SAO) or a substitute value. For example, the in-loop filter unit 160 may perform filtering by applying a replacement value to a reconstructed block reconstructing the current block when an edge exists in the current block or when the current block is a screen content area. .

15 is a block diagram illustrating a video decoding apparatus using image analysis according to an embodiment of the present invention.

Referring to FIG. 15, a video decoding apparatus according to an embodiment of the present invention includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an addition unit 240, and an in-loop filter unit 250. ), a frame memory 260, an intra prediction unit 270, and a motion compensation unit 280. Here, the intra prediction unit 270 and the motion compensation unit 280 may be collectively referred to as a prediction unit.

In particular, the intra prediction unit 270 may perform intra prediction on the current block by determining whether to apply the inversion motion based on the decoding method for the current block according to the analysis result of the image characteristics. That is, the intra prediction unit 270 may perform intra prediction on the current block by determining whether to apply the inversion motion to intra prediction according to block matching or template matching based on the analysis result of the image characteristics.

For example, when an edge exists in the current block or when the current block is a screen content area, the intra prediction unit 270 may apply an inversion motion to perform intra prediction on the current block.

The in-loop filter unit 250 may perform in-loop filtering on the current block based on a decoding method for the current block according to a result of analyzing the image characteristics. That is, the in-loop filter unit 250 may perform filtering by using a sample adaptive offset (SAO) or a substitute value. For example, the in-loop filter unit 250 may perform filtering by applying a substitute value to the current block when an edge exists in the current block or when the current block is a screen content area.

Meanwhile, since each component of the video decoding apparatus corresponds to the component of the video encoding apparatus of FIG. 14 and can be understood, a detailed description thereof will be omitted.

The video encoding/decoding apparatus according to the present invention can be implemented as a computer-readable program or code on a computer-readable recording medium. The computer-readable recording medium includes all types of recording devices that store data that can be read by a computer system. In addition, a computer-readable recording medium may be distributed over a computer system connected through a network to store and execute a computer-readable program or code in a distributed manner.

The above-described video encoding/decoding method using image analysis according to an embodiment of the present invention includes intra prediction by applying inversion motion and in-loop filtering by applying replacement values to images having different image characteristics from natural images such as screen content. Through this, coding efficiency can be improved and complexity can be reduced.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can do it.

11: image characteristic candidate selection unit 12: pixel classification unit
13: image analysis unit 14: mode addition decision unit
15: additional mode execution unit 16: additional mode identification flag and related parameter encoding unit
110: subtraction unit 120: conversion unit
121, 230: inverse transform unit 130: quantization unit
131, 220: inverse quantization unit 140: entropy encoding unit
150, 240: addition unit 160, 250: in-loop filter unit
170, 260: frame memory 180, 270: intra prediction unit
190, 280: motion compensation unit 210: entropy decoding unit

Claims (21)

Obtaining a prediction mode related parameter signaled from the bitstream, the prediction mode related parameter including at least one of a decoding method parameter, a candidate list configuration parameter, and a motion vector selection parameter;
Determining whether a decoding method of a current block is a decoding method by block matching, based on the decoding method parameter;
When the decoding method of the current block is a decoding method based on the block matching,
Constructing a motion vector candidate list from a plurality of motion vectors of the current block based on the candidate list configuration parameter;
Selecting one motion vector from the configured motion vector candidate list based on the motion vector selection parameter; And
Including the step of generating a prediction block of the current block based on the selected motion vector,
The selected motion vector indicates a location of a block matching the current block based on the current block. The method of claim 1,
The block matching the current block belongs to the same picture as the current block and is a block that has been decoded before the current block. The method of claim 1,
The candidate list configuration parameter includes a candidate list number parameter indicating the number of the plurality of motion vectors constituting the motion vector candidate list. The method of claim 1,
The generation of the prediction block is performed by copying pixels of a block matching the current block indicated by the selected motion vector. Determining whether a current block encoding method is a block matching method;
When the encoding method of the current block is an encoding method based on the block matching,
Constructing a motion vector candidate list from a plurality of motion vectors of the current block;
Selecting any one motion vector from the constructed motion vector candidate list;
Generating a prediction block of the current block based on the selected motion vector; And
Including the step of encoding a residual block generated based on the prediction block and a parameter related to a prediction mode,
The prediction mode related parameter includes at least one of a decoding method parameter, a candidate list configuration parameter, or a motion vector selection parameter,
The decoding method parameter is determined according to whether the encoding method of the current block is an encoding method based on block matching,
The candidate list configuration parameter is determined based on the configured motion vector candidate list,
The motion vector selection parameter is determined based on the selected motion vector. The method of claim 5,
A video encoding method, wherein the block matching the current block belongs to the same picture as the current block, and decoding is completed before the current block. The method of claim 5,
The candidate list configuration parameter includes a candidate list number parameter indicating the number of the plurality of motion vectors constituting the motion vector candidate list. The method of claim 5,
The generation of the prediction block is performed by copying pixels of a block matching the current block indicated by the selected motion vector. A computer-readable recording medium storing a bitstream decoded in a video decoding method, comprising:
The video decoding method,
Obtaining a prediction mode related parameter signaled from the bitstream, the prediction mode related parameter including at least one of a decoding method parameter, a candidate list configuration parameter, and a motion vector selection parameter;
Determining whether a decoding method of a current block is a decoding method by block matching, based on the decoding method parameter;
When the decoding method of the current block is a decoding method based on the block matching,
Constructing a motion vector candidate list from a plurality of motion vectors of the current block based on the candidate list configuration parameter;
Selecting one motion vector from the configured motion vector candidate list based on the motion vector selection parameter;
Including the step of generating a prediction block of the current block based on the selected motion vector,
The selected motion vector is a computer-readable recording medium indicating a position of a block matching the current block based on the current block. delete delete delete delete delete delete delete delete delete delete delete delete

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