KR20070076391A - A method and apparatus for decoding/encoding a video signal - Google Patents

Abstract

A method and an apparatus for decoding/encoding a video signal are provided to minimize information to be transmitted for illumination compensation by estimating an offset value of a current block by using information of a neighbor block and sending a difference between the current block and the neighbor block. To decode a video signal, flag information representing execution of illumination compensation for a current block is obtained from a video signal(S410). If illumination compensation is executed according to the flag information, an offset value of the current block representing a difference between a mean pixel value of the current block and a mean pixel value of a reference block is restorable(S420). To encode a video signal, an offset value of the current block representing a difference between a mean pixel value of the current block and a mean pixel value of a reference block is obtained. An optimum reference block matched with the current block is searched by using the offset value. A motion vector is obtained from the searched reference block for encoding.

Description

A method and apparatus for decoding / encoding a video signal

1 illustrates a multi-view sequence encoding and decoding system to which the present invention is applied.

2 shows an example of a prediction structure between pictures in multi-view video coding to which the present invention is applied.

3 is a diagram for describing a process of obtaining an offset value of a current block according to an embodiment to which the present invention is applied.

4 is an embodiment to which the present invention is applied and shows a flowchart for explaining a process of performing lighting compensation using flag information indicating whether lighting compensation is performed on a current block and an offset value of the current block.

5A to 5B illustrate an embodiment to which the present invention is applied to illustrate a method of performing illumination compensation using flag information and offset values for blocks belonging to a P slice and a B slice, respectively.

FIG. 6 is a flowchart illustrating a method of performing lighting compensation when a current block is predictively coded using two or more reference blocks according to an embodiment to which the present invention is applied.

FIG. 7 is a flowchart illustrating a process of performing lighting compensation using flag information indicating whether lighting compensation is performed on a current block according to an embodiment to which the present invention is applied.

8A to 8C are diagrams illustrating the use range of flag information indicating whether lighting compensation is performed on a current block as an embodiment to which the present invention is applied.

9 is a flowchart illustrating a process of obtaining a motion vector in consideration of an offset value of a current block according to an embodiment to which the present invention is applied.

The present invention relates to a method and apparatus for decoding / encoding a video signal.

The mainstream video broadcasting image is a single view image acquired with one camera. Multi-view video, on the other hand, is a three-dimensional (3D) image processing method that geometrically corrects images taken by more than one camera and provides users with various viewpoints in various directions through spatial synthesis. It is a field. A multi-view video may provide a 3D stereoscopic image or an image of many viewpoints to a user, and has a feature that includes a larger area than an image area that can be acquired using a single camera.

Since the view sequences of the multi-view video described above are images obtained from different cameras, illumination differences may occur due to internal and external factors of the camera. For example, a camera heterogeneity, a difference in camera calibration, or a camera alignment is caused. Since the illumination difference significantly lowers the correlation between different views, thereby inhibiting effective coding, an illumination compensated coding technique is required to prevent this.

An object of the present invention is to perform efficient lighting compensation by using an identifier indicating whether to apply lighting compensation to a certain layer.

Another object of the present invention is to improve coding efficiency of a video signal by performing lighting compensation using an identifier indicating whether lighting compensation is performed on a current block and an offset value indicating an average pixel value difference between blocks.

Another object of the present invention is to improve coding efficiency of a video signal by effectively using correlations between blocks or views.

Another object of the present invention is to improve coding efficiency of a video signal by considering an offset value representing an average pixel value difference between blocks when performing motion estimation.

In order to achieve the above object, the present invention obtains flag information indicating whether or not to perform lighting compensation of a current block, and when lighting compensation is performed according to the flag information, an average pixel value of the current block and an average of a reference block. And restoring an offset value of a current block representing a difference in pixel values.

The present invention also provides a method of obtaining flag information for inducing illumination compensation for a certain layer of a video signal, and decoding a layer of the video signal for which illumination compensation is performed according to the flag information. The predetermined layer of the video signal may include a sequence layer, a view layer, a picture group layer, a picture layer, a slice layer, and a macroblock. Provided is a video signal decoding method characterized in that either of a layer or a block layer.

The present invention also provides a method of obtaining an offset value of a current block representing a difference between an average pixel value of a current block and an average pixel value of a reference block, and searching for a reference block that is optimally matched to the current block using the offset value. And obtaining and encoding a motion vector from the searched reference block.

The above objects and features of the construction will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In addition, the terms used in the present invention was selected as a general term widely used as possible now, but in some cases, the term is arbitrarily selected by the applicant, in which case the meaning is described in detail in the description of the invention, It is to be understood that the present invention is to be understood as the meaning of terms rather than the names of terms.

1 illustrates a multi-view sequence encoding and decoding system to which the present invention is applied. As shown in FIG. 1, the multiview image encoding system to which the present invention is applied includes a multiview image generator 10, a preprocessing part 20, and an encoding part 30. . In addition, the decoding system includes an extractor 40, an extractor 50, a decoding part 50, a post processing part 60, and a display part 70.

The multi-view image generator 10 includes an image obtaining apparatus (for example, cameras # 1 to #N) corresponding to the number of multi-views to acquire independent images for each viewpoint. When the multiview image data is input, the preprocessing unit 20 performs a function of increasing the correlation between the multiview image data through a preprocessing process while solving noise removal and imbalancing problems. The encoder 30 includes a motion estimator, a motion compensator, and a disparity estimator, a disparity compensator, an illumination compensator, a bit rate control, and a residual image encoder. do. The encoding unit 30 may apply a generally known method.

The lighting compensator of the encoding unit 30 to which the present invention is applied performs motion compensation adaptive to lighting changes for MVC. Coding efficiency may be increased by using flag information indicating whether lighting compensation is performed on a current block. Also, by obtaining the average pixel value of the current block and the average pixel value of the corresponding reference block, the difference between the two average pixel values can be obtained and transmitted, thereby enabling efficient encoding. In this case, a difference between the average pixel value of the current block and the average pixel value of the reference block corresponding thereto is referred to as an offset value. In transmitting the offset value of the current block, it is necessary to further reduce the number of bits to be coded. For example, a predicate of an offset value of the current block may be obtained using neighboring blocks of the current block, a difference value between the offset value and the predictor may be obtained, and only the difference value may be transmitted. When the above process is performed, a picture of another view may be used as a reference picture. At this time, a view identifier indicating a view of the picture may be used.

The extractor 40 functions to extract only a bitstream corresponding to a desired view from the transmitted MVC bitstream. The extractor 40 may view the header and selectively decode only the desired time point. In addition, view scalability may be implemented by extracting only a bitstream corresponding to a desired view using a view identifier that distinguishes a view of a picture. Since MVC must be fully compatible with H.264 / AVC, it is necessary to decode only a specific point in time that is compatible with H.264 / AVC. In this case, a view identifier that distinguishes a view of the picture may be used to decode only compatible views. The bitstream extracted through the extractor 40 is transmitted to the decoding unit 50. The decoder 50 includes a motion compensator, an illumination compensator, a weight predictor, a deblocking filter, and the like. The decoding unit 50 receives the bitstream encoded by the above-described method, and decodes it in reverse.

The lighting compensator of the decoding unit 50 to which the present invention is applied performs motion compensation adaptive to lighting changes for MVC. Accordingly, in order to recover the current block, an offset value of the current block, which is a difference between the average pixel value of the current block and the average pixel value of the reference block corresponding thereto, must be transmitted from the encoding unit 30. In addition, flag information indicating whether lighting compensation is performed on the current block may be transmitted together. In transmitting the offset value, as an example of a method for further reducing the number of bits to be coded, using the neighboring blocks of the current block, a predictor of the offset value of the current block is obtained, and the offset value and the free value are obtained. The difference with the dict was obtained and only the difference was transmitted. Accordingly, the decoding unit 50 extracts flag information and offset values of neighboring blocks of the current block, index information of corresponding reference blocks of the current block and its neighboring blocks from the video signal, and uses the predictor to extract the predictor. Can be obtained. The offset value may be obtained between the offset value and the predictor, and the offset value of the current block may be restored using the difference value and the predictor. When performing the process of acquiring the predictor as described above, when a picture of another view is used as a reference picture, a view identifier indicating a view of the picture may be used.

In addition, the post-processing unit 60 performs a function of increasing the reliability and resolution of the decoded data. Finally, the display unit 70 provides the decoded data to the user in various ways depending on the function of the display, in particular, the ability to process a multi-view image. For example, it is a 2D display 71 that provides only a planar two-dimensional image, or a stereo type display 73 that provides two views as a stereoscopic image, or a stereoscopic view of M views (2 <M). The display 75 may provide an image.

2 shows an example of a prediction structure between pictures in multi-view video coding to which the present invention is applied.

As shown in FIG. 2, T0 to T100 on the horizontal axis represent frames according to time, and S0 to S7 on the vertical axis represent frames according to viewpoints, respectively. For example, pictures in T0 refer to images taken by different cameras in the same time zone (T0), and pictures in S0 refer to images in different time zones taken by one camera. In addition, the arrows in the drawing indicate the prediction direction and the order of each picture. For example, a P0 picture at S2 time point in the T0 time zone is a picture predicted from I0, and the P0 picture is also at S4 time point in the TO time zone. It becomes a reference picture of another P0 picture. It is also a reference picture of the B1 and B2 pictures in the T4 and T2 time zones at the time S2.

The lighting compensation to which the present invention is applied may be applied, for example, in the process of performing motion estimation or motion compensation, and the lighting compensation may be applied using a reference block at which the current block is different. The prediction structure may be applied when performed. Even in this case, an identifier for distinguishing the viewpoints between the blocks may be needed.

3 is a diagram for describing a process of obtaining an offset value of a current block according to an embodiment to which the present invention is applied.

Illumination compensation may be performed in the motion estimation process. When comparing the similarity between the current block and the candidate reference block, the lighting difference between the two blocks should be considered. New motion estimation / motion compensation is performed to compensate for the illumination difference. New sum of absorptive differences (SAD) can be obtained using Equation 2 below.

Here, M _c represents an average pixel value of the current block and M _r represents an average pixel value of the reference block. I _c (x, y) represents the pixel value at the (x, y) coordinate of the current block, and I _r (x + Δx, y + Δy) is the motion vector (Δx, Δy) of the reference block. Indicates a pixel value. By performing motion estimation based on the new SAD of Equation 1, an average pixel value difference between the current block and the reference block may be obtained. The obtained average pixel value difference is referred to as an offset value IC_offset.

When motion estimation with illumination compensation is performed, an offset value and a motion vector are obtained, and illumination compensation is performed using Equation 3 using the offset value and the motion vector.

Here, R (x, y) represents an error value in which illumination compensation is performed.

The offset value IC_offset = M _c -M _r must be transmitted to the decoding unit 50. Lighting compensation in the decoding unit 50 is performed as follows.

^R, (x, y) denotes a two restored, the illumination compensation values to perform the error _{(residual), I 'c (} x, y) represents the pixel value of the restored current block.

In order to recover the current block, an offset value must be transmitted to the decoding unit 50, and the offset value can be predicted from information of neighboring blocks. In order to further reduce the number of bits to code the offset value , only the difference value RIC_offset between the offset value IC_offset of the current block and the offset value IC_offset_pred of the neighboring block may be sent. This is shown in Equation 5 below.

RIC _ offset  = IC _ offset  ― IC _ offset _ pred

4 is an embodiment to which the present invention is applied and shows a flowchart for explaining a process of performing lighting compensation using flag information indicating whether lighting compensation is performed on a current block and an offset value of the current block.

The decoding unit 50 extracts flag information and offset values of neighboring blocks of the current block, index information of corresponding reference blocks of the current block and its neighboring blocks, and the like from the video signal to perform lighting compensation. It can be used to obtain the predictor of the current block. The offset value of the current block and the predictor may be obtained, and the offset value of the current block may be restored using the obtained difference value and the predictor. In this case, when restoring the offset value of the current block, flag information IC_flag indicating whether illumination compensation of the current block is performed may be used. First, flag information indicating whether illumination compensation is performed on the current block is obtained from the video signal (S410). When illumination compensation is performed according to the flag information, the offset value of the current block indicating the difference between the average pixel value of the current block and the average pixel value of the reference block may be restored (S420). As such, the illumination compensation technique codes difference values of average pixel values of blocks belonging to different pictures. When a flag indicating whether the illumination compensation technique is applied to each block is used, when the corresponding block is a block belonging to a P slice, one flag information and one offset value may be encoded / decoded. However, if the corresponding block is a block belonging to a B slice, various methods may be possible. Hereinafter, the detailed description will be made with reference to FIGS. 5A to 5B.

5A to 5B illustrate an embodiment to which the present invention is applied to illustrate a method of performing illumination compensation using flag information and offset values for blocks belonging to a P slice and a B slice, respectively.

In FIG. 5A, "C" represents a current block C, "N" represents a block neighboring the current block C, "R" represents a block referred to by the current block C, and "S". Denotes a block referenced by a block N neighboring the current block C. "m _c " represents an average pixel value of the current block, and "m _r " represents an average pixel value of the block referenced by the current block. If the offset value of the current block (C) is called "IC_offset", then IC_offset = m _c- m _r becomes Similarly, if the offset value of the neighboring block N is "IC_offset_pred", the encoding unit 30 does not transmit the value as it is to restore "IC_offset", which is the offset value of the current block C, but the offset value of the current block. Only the difference value RIC_offset between (IC_offset) and the offset value (IC_offset_pred) of the neighboring block may be sent. Here, RIC _ offset is the same as Equation 5. Here, various methods may be applied when generating the predicate of the current block from the flag information or the offset value of the neighboring block. For example, information of only one neighboring block may be used, or information of two or more neighboring blocks may be used. When information of two or more neighboring blocks is used, an average value may be used or a median may be used. As such, when the current block is predictively coded using one reference block, lighting compensation may be performed using one offset value and one flag information.

However, if the corresponding block belongs to a B slice, that is, the current block is predictively coded using two or more reference blocks, various methods may be possible. For example, in FIG. 5B, "C" represents the current block C, "N" represents a block neighboring the current block C, and "R0" corresponds to reference picture 1 of List 0 referenced by the current block. It is assumed that "S0" represents a reference block in reference picture 1 of List 0 referenced by the neighboring block. In addition, it is assumed that "R1" represents a reference block in reference picture 3 of List 1 referred to by the current block, and "S0" represents a reference block in reference picture 3 of List 1 referred to by the neighboring block. In this case, since the flag information and the offset value of the current block exist for each reference block, two values exist. Accordingly, at least one of the flag information and the offset value may be used.

For example, the predictor of the current block may be obtained by combining information about two reference blocks through motion compensation. Here, whether to apply lighting compensation to the current block is indicated by one flag information, and when the flag information is true, one offset value may be obtained from the current block and the predictor to perform encoding / decoding. As another example, in the process of performing motion compensation, it is determined whether lighting compensation is applied to each of two reference blocks. Flag information is provided for each reference block, and one offset value obtained using the flag information can be encoded / decoded. In this case, two flag information may be used based on the reference block and one offset value may be used based on the current block. As another example, whether or not to apply lighting compensation to the block based on the current block may be indicated in one flag information. Each offset value may be encoded / decoded with respect to two reference blocks. In the encoding process, when the illumination compensation is not applied to any one of the reference blocks, the offset value corresponding thereto is zero. In this case, one flag information may be used based on the current block and two offset values may be used based on the reference block. As another example, each flag information and an offset value may be encoded / decoded for each reference block. In this case, both the flag information and the offset value may be used in each of two reference blocks.

In each case, the offset value is not encoded as it is, and after predicting from the offset value of the neighboring block, only the error value can be encoded.

FIG. 6 is a flowchart illustrating a method of performing lighting compensation when a current block is predictively coded using two reference blocks according to an embodiment to which the present invention is applied.

If the current block is a block belonging to a B slice, in order to perform lighting compensation, flag information and offset values of neighboring blocks of the current block, index information of corresponding reference blocks of the current block and its neighboring blocks, etc. are extracted from the video signal. In addition, the information of the current block may be obtained using the information. The offset value of the current block and the predictor may be obtained, and the offset value of the current block may be restored using the obtained difference value and the predictor. In this case, when restoring the offset value of the current block, flag information IC_flag indicating whether illumination compensation of the current block is performed may be used. First, flag information indicating whether illumination compensation of the current block is performed is obtained from the video signal (S610). When illumination compensation is performed according to the flag information, the offset value of the current block indicating the difference between the average pixel value of the current block and the average pixel value of the reference block may be restored (S620). However, when the current block is predictively coded using two reference blocks as described above, the decoder cannot directly know an offset value corresponding to each reference block. This is because, when the offset value of the current block is obtained, the pixel value obtained by averaging the two reference blocks is used. Therefore, in an embodiment of the present invention, an offset value corresponding to each reference block may be obtained to enable more accurate prediction. Therefore, when the current block is predictively coded using two reference blocks, an offset value corresponding to each reference block may be obtained using the offset value (S630). This is shown in Equation 6 below.

IC_offset = - * - *

IC_offset =-*-*

-

= IC_offset + (

-1)*

+

*

IC_offsetL0 =

-

= IC_offset + (

-One)*

+

*

-

= IC_offset +

*

+ (

-1)*

.IC_offsetL1 =

-

= IC_offset +

*

+ (

-One)*

.

Here, m _c represents the average pixel value of the current block, and m _{r , 1} , m _{r , 2} represent the average pixel value of the reference block, respectively. w ₁ and w ₂ represent weight coefficients in bi-predictive coding.

When the illumination compensation is performed in this manner, the accurate offset value corresponding to each reference block can be obtained and used separately, thereby enabling more accurate predictive coding. When restoring the offset value of the current block, the offset value may be obtained by adding the restored offset difference value and the predictor value. At this time, a predictor for each of List0 and List1 may be obtained, and the combination may be combined to obtain a predicator required when restoring the offset value of the current block.

FIG. 7 is a flowchart illustrating a process of performing lighting compensation using flag information indicating whether lighting compensation is performed on a predetermined layer of a video signal according to an embodiment to which the present invention is applied.

Lighting compensation techniques are intended to compensate for lighting or color differences between cameras. This technique is further extended and can be applied between sequence images obtained from the same camera. This technique ensures that lighting or color differences do not significantly affect motion estimation. However, in actual encoding, flag information indicating whether lighting compensation is applied is used. The scope of illumination compensation may be a sequence, a view, a group of pictures (GOP), a picture, a slice, a macroblock, a sub-block, and the like. have. If the lighting compensation technique is used in a small area range, it is possible to adjust the more local area, but instead, it takes a lot of bits for the flag information. Also, in many cases, lighting compensation techniques may not be needed. Therefore, by assigning a flag bit indicating whether the illumination compensation technique is used for each region range, it is possible to effectively use the illumination compensation technique. First, flag information for inducing lighting compensation for a predetermined layer of a video signal is obtained (S710). For example, flag information may be set for each region range as follows. "Seq_IC_flag" for sequence layer, "view_IC_flag" for view layer, "GOP_IC_flag" for GOP layer, "pic_IC_flag" for picture layer, "slice_IC_flag" for slice layer, "mb_IC_flag" for macroblock layer, block For the layer, flag bits may be allocated with "blk_IC_flag". This will be described in detail with reference to FIGS. 8A to 8C. In operation S720, a predetermined layer of the video signal on which illumination compensation is performed may be decoded according to the flag information.

8A to 8C are diagrams for explaining a range of use of flag information for inducing lighting compensation of a current block as an embodiment to which the present invention is applied.

An application range of flag information for inducing lighting compensation may be divided by layers. For example, as shown in FIGS. 8A to 8B, "seq_IC_flag" 810 for the sequence layer, "view_IC_flag" 820 for the view layer, "GOP_IC_flag" 830 for the GOP layer, and "" for the picture layer. pic_IC_flag "840," slice_IC_flag "850 for the slice layer," mb_IC_flag "860 for the macroblock layer, and" blk_IC_flag "870 for the block layer. Here, each flag is 1 bit information, and at least one flag may exist. In addition, flags such as sequence / view / picture / slice range may be located in the corresponding parameter set or header, or in other parameter sets. For example, "seq_IC_flag" 810 may be located in a sequence parameter set, "view_IC_flag" 820 may be located in a view parameter set, and "pic_IC_flag" ( 840 may be located in a picture parameter set. In addition, the "slice_IC_flag" 850 may be located in the slice header.

When two or more flag information exist, whether to perform lighting compensation of a lower layer among two or more predetermined layers may be controlled by performing lighting compensation of a higher layer. That is, when each flag bit value is set to 1, it indicates that the lighting compensation technique may be applied in the lower range. For example, if pic_IC_flag = 1, the slice_IC_flag value can be set to 1 or 0 for each slice within the corresponding picture range, or the mb_IC_flag value can be set to 1 or 0 for each macroblock, or each A blk_IC_flag value may be set to 1 or 0 for a block. If there is a viewpoint parameter set, if seq_IC_flag = 1, the view_IC_flag value can be set to 1 or 0 for each viewpoint. However, when view_IC_flag = 1, the flag bit value for each GOP, picture, slice, macroblock, or block belonging to the corresponding viewpoint may be set to 1 or 0, as shown in FIG. 8A, or may not be the case. . In this case, otherwise, the flag for each GOP, picture, slice, macroblock, or block is not controlled by the flag information on the viewpoint as in FIG. 8B.

When the flag bit value of the upper range is 0, the flag bit values of the lower range are automatically zero. For example, when seq_IC_flag = 0, this means that the lighting compensation technique is not applied to the sequence, and thus, view_IC_flag, GOP_IC_flag, pic_IC_flag, slice_IC_flag, mb_IC_flag, and blk_IC_flag are all set to zero. In addition, only one mb_IC_flag and blk_IC_flag may be used according to a specific implementation method of the lighting compensation technique. In addition, the flag information view_IC_flag about the viewpoint may be applied when a viewpoint parameter set is newly applied in multiview video coding. The offset value of the current block may be additionally encoded / decoded according to the flag bit value in the macroblock or subblock which is the lowest unit.

Also, as shown in FIG. 8C, an embodiment in which a flag for applying an IC technology is applied only to a slice and a macroblock layer may be considered. For example, when slice_IC_flag is 0, it may mean that the IC is not applied to the slice. If slice_IC_flag is 1, it may mean that the IC is applied to the corresponding slice. In this case, if mb_IC_flag is 1, IC_offset is restored in the corresponding macroblock. If mb_IC_flag is 0, this may mean that the IC is not applied to the corresponding macroblock.

According to another embodiment of the present invention, when flag information of a layer higher than a macroblock layer is true, an offset value of a current block indicating a difference between an average pixel value of a current block and an average pixel value of a reference block may be obtained. In this case, flag information on the macroblock layer or the block layer may not be used. When applying the lighting compensation technology, whether or not to apply the lighting compensation technology to each block may be indicated through the flag information. However, it may be sufficient to indicate only its value, such as a motion vector. This may be operated together with the application range of the lighting compensation technology, and may indicate whether lighting compensation is applied in the lower range through flag information on the upper range (sequence, view, GOP, picture). In the lowest block, the macroblock layer or block layer, the offset value may be sufficient without using the flag bit. It can basically perform prediction and encoding in a manner similar to a motion vector. For example, when performing predictive coding on the current block, the offset value of the neighboring block is assigned to the offset value of the current block. In the case of bidirectional predictive coding, an offset value for each reference block is obtained through calculation with reference blocks found in List 0 and List 1. Therefore, when encoding offset values of the current block, only offset errors are encoded / decoded without directly encoding the offset value for each reference block by using offset values of neighboring blocks. The prediction method of the offset value may use the above offset prediction method or a method of obtaining a median used in motion vector prediction. Even in the direct mode of the bidirectional prediction, offset values may be obtained through the information already given in the same manner as the motion vector without encoding / decoding the additional information.

In addition, as another embodiment of the present invention, when using a decoder other than the MVC decoder (for example, H.264), the view image compatible with the existing decoder should be able to be decoded by the existing decoder Therefore, "view_IC_flag = false or 0" should be set. Here we need to explain the concept of base views. We may need at least one view sequence to be compatible with the H.264 / AVC decoder. Therefore, it is necessary to define time points that can be independently decoded, which is called a reference time point. This reference time point becomes a reference of encoding among multiviews, which corresponds to a reference view. In MVC, an image corresponding to a reference time point is encoded by a conventional general video encoding method (MPEG-2, MPEG-4, H.263, H.264, etc.) to form an independent bitstream. The image corresponding to the reference time point may or may not be compatible with H.264 / AVC. However, an image of a viewpoint compatible with H.264 / AVC is always a reference viewpoint.

9 is a flowchart illustrating a process of obtaining a motion vector in consideration of an offset value of a current block according to an embodiment to which the present invention is applied.

The offset value of the current block may be obtained from the video signal (S910). The reference block that is optimally matched to the current block is searched using the offset value (S920). A motion vector may be obtained and encoded from the searched reference block (S930). Here, there are considerations when performing motion estimation when applying illumination compensation. For example, in the case of comparing the similarity of two blocks by canceling the average pixel value between blocks, when the motion estimation is performed, the similarity degree is determined by subtracting the average pixel value of each block from the pixel values of each block. Calculate In this case, since the offset value between the two blocks is encoded separately, such a cost should be reflected in the motion estimation process. The existing cost calculation is shown in Equation 7 below.

In the case of applying illumination compensation, the sum of absolute differences (SAD) is calculated as follows.

은 각각 현재 블록과 참조 블록의 화소값을 나타낸다.

은 각각 현재 블록과 참조 블록의 평균 화소값을 나타낸다. 오프셋 값의 비용은 SAD 계산에 포함하여 반영할 수 있다.here,

Denote pixel values of the current block and the reference block, respectively.

Denote average pixel values of the current block and the reference block, respectively. The cost of the offset value can be reflected in the SAD calculation.

SAD_IC = α | offset-offset_pred | + ∑ ｜ (I_c(m, n) -M_c )-(I_r(m, n)-M_r ) ｜

는 가중치가 되며, 1일 때, 오프셋 값의 절대치가 반영된다. 또한, 조명 보상 비용을 반영하는 다른 방법으로서, 오프셋 값을 부호화하는 데에 쓰이는 비트수를 추정해서 반영하는 방법이 있다. here,

Is a weight, and when 1, the absolute value of the offset value is reflected. As another method of reflecting the illumination compensation cost, there is a method of estimating and reflecting the number of bits used to encode the offset value.

This estimates and reflects the offset encoding bits as in Equation 11 below. Here, the coded bits may be estimated to be proportional to the magnitude of the offset difference value.

In this case, the new cost can be obtained using Equation 12 below.

Cost =

Cost =

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features.

Therefore, it is to be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

Each viewpoint image of the multi-view video is caused by a difference in illumination due to internal and external factors of the camera. This illumination difference significantly reduces the correlation between different viewpoints, which hinders effective encoding. Therefore, in the present invention, by predicting the offset value of the current block using the information of the neighboring block and transmitting only the difference value, it is possible to minimize the information to be transmitted for lighting compensation. It is also possible to minimize the information to be transmitted by predicting flag information indicating whether the current block performs lighting compensation and transmitting only the difference value. In addition, when the prediction coding is performed using two or more reference blocks, more efficient coding may be performed by applying the offset value and the flag information in at least one or more various methods. In addition, by assigning a flag bit indicating whether to use the illumination compensation technique for each region range of the video signal, it is possible to effectively use the illumination compensation technique. In addition, it is possible to perform more accurate predictive coding by calculating the cost by reflecting the illumination difference in the process of performing the motion estimation.

Claims (12)

Obtaining flag information indicating whether lighting compensation is performed on a current block; Restoring an offset value of a current block indicating a difference between an average pixel value of the current block and an average pixel value of a reference block when illumination compensation is performed according to the flag information. Video signal decoding method comprising a. The method of claim 1, If the current block is predictively coded using two or more reference blocks, The flag information is obtained using one flag information obtained from flag information of the two or more reference blocks, And the offset value is reconstructed using one offset value obtained from offset values corresponding to the two or more reference blocks. The method of claim 1, If the current block is predictively coded using two or more reference blocks, The flag information is obtained using at least two flag information for each of the at least two reference blocks, And the offset value is reconstructed using one offset value obtained from offset values corresponding to the two or more reference blocks. The method of claim 1, If the current block is predictively coded using two or more reference blocks, The flag information is obtained using one flag information obtained from flag information of the two or more reference blocks, And the offset value is reconstructed using at least two offset values for each of the at least two reference blocks. The method of claim 1, If the current block is predictively coded using two or more reference blocks, The flag information is obtained using at least two flag information for each of the at least two reference blocks, And the offset value is reconstructed using at least two offset values for each of the at least two reference blocks. The method of claim 1, wherein the video signal decoding method comprises: If the current block is predictively coded using the at least two reference blocks, obtaining an offset value for each reference block of the current block using the offset value The video signal decoding method further comprising. Obtaining flag information for inducing illumination compensation for a certain layer of the video signal; Decoding a layer of the video signal on which illumination compensation is performed according to the flag information, The predetermined layer of the video signal may include a sequence layer, a view layer, a group of picture layer, a picture layer, a slice layer, a macroblock layer, or a block ( block) any one of the layers. The method of claim 7, wherein And if there are two or more pieces of flag information obtained, whether to perform lighting compensation of a lower layer among the two or more predetermined layers in the decoding step is controlled by whether lighting compensation is performed by a higher layer. The method of claim 7, wherein the video signal decoding method, If flag information of a layer higher than the macroblock layer is true, obtaining an offset value of a current block indicating a difference between an average pixel value of a current block and an average pixel value of a reference block, And the flag information on the macroblock layer or the block layer is not used. Obtaining an offset value of the current block indicating a difference between the average pixel value of the current block and the average pixel value of the reference block; Searching for a reference block that optimally matches a current block using the offset value; Acquiring and encoding a motion vector from the searched reference block Video signal encoding method comprising a. The method of claim 10, wherein the video signal encoding method comprises: Measuring an error energy (SAD) between the current block and the reference block; Obtaining offset values of blocks neighboring the current block; Acquiring a predictor of a current block using the obtained offset values Include more, And measuring an error energy using an error value that is a difference between the offset value of the current block and the predictor. The method of claim 10, wherein the video signal encoding method comprises: Obtaining offset values of blocks neighboring the current block; Obtaining a predictor of a current block using the obtained offset values; Obtaining an error value that is a difference between the offset value of the current block and the predictor; And Estimating a bit necessary for encoding the error value Include more, And encoding the bit to be proportional to the error value.

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