KR20140043015A

KR20140043015A - Method and apparatus for image encoding

Info

Publication number: KR20140043015A
Application number: KR1020120145687A
Authority: KR
Inventors: 이호동; 최윤식; 홍순기
Original assignee: 연세대학교 산학협력단
Priority date: 2012-09-28
Filing date: 2012-12-13
Publication date: 2014-04-08

Abstract

The present invention relates to a method of encoding an image, the method comprising: obtaining depth information of a current coding unit, comparing depth information with a threshold value of the current coding unit, and performing prediction encoding according to a result of the comparing step. In addition, the present invention provides an image encoding method capable of encoding an image at high speed by reducing complexity in a coding process.

Description

[0001] The present invention relates to a method and apparatus for image encoding,

The present invention relates to a video encoding method and apparatus.

H.264 / AVC is a video compression standard technology with high compression efficiency. In H.264 / AVC, the original signal can be predictively encoded through an intra prediction technique for eliminating correlation in an image and an inter prediction technique for eliminating correlation between images. The H.264 / AVC encoder performs discrete cosine transform (DCT) encoding and quantization on the difference value between the original signal and the prediction signal. The quantized signal is then entropy encoded after being aligned by a zigzag scanning method.

Recently, ITU-T VCEG (Video Coding Experts Group) and ISO / IEC MPEG (Moving Picture Experts Group) have formed Joint Collaborative Team on Video Coding (JCT-VC) And it is known that the compression efficiency is improved by about 40% or more as compared with the existing standard H.264 / AVC. H.264 / AVC and HEVC are basically block-based image coders. However, unlike H.264 / AVC, which encodes MB (Macro Block) units with a fixed size of 16x16, Encoding according to a CU (Coding Unit) basis having various sizes ranging from a maximum 64x64 size to an 8x8 size.

However, HEVC, which has been standardized up to now, uses a method of selecting the CU with the highest compression efficiency by performing encoding on all possible sizes of CU while having high compression efficiency, thus requiring very high computational complexity and long coding time. There is a problem. This may cause problems in watching real-time video or providing high-definition content. Therefore, a method for solving the problem is needed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a video encoding method and apparatus for simplifying an operation and shortening a encoding time at the time of encoding.

It is another object of the present invention to provide an image encoding method and apparatus for providing high-quality image information in real time through high-speed encoding by improving the performance of an encoder.

In accordance with another aspect of the present invention, there is provided a video encoding method comprising: acquiring depth information of a current coding unit; Comparing depth information with a threshold of the current coding unit; And performing predictive encoding according to the result of the comparing step.

Here, when the depth information of the current coding unit is smaller than the threshold, the prediction encoding is performed by the size of the symmetric prediction unit, and when the depth information of the current coding unit is larger than the threshold, the symmetric prediction unit size and the asymmetric prediction unit size. Predictive encoding is preferable.

In addition, the threshold is preferably set to two.

In addition, the size of the current coding unit is preferably 64x64 or 32x32.

Meanwhile, the size of the symmetric prediction unit may be 2N × 2N (where N is an integer greater than 0 and 2N is the number of pixels) or two 2N × N or two N × 2N.

In addition, the size of the symmetric prediction unit may be four N × N.

In addition, the size of the asymmetric prediction unit is composed of two, 2NxnU, 2NxnD, nLx2N, nRx2N (where N is an integer greater than 0, 2N is the number of pixels, U, D, L, R is a coding unit And an integer different from N as a unit representing the length of the top, bottom, left, and right side of.

On the other hand, after the prediction encoding, it is preferable to include the step of dividing into the next coding unit depth.

According to the present invention, the complexity of the encoder is reduced by omitting the encoding process of the asymmetric prediction unit by using the depth information of the current coding unit.

In addition, according to the present invention it is possible to provide high-speed video coding more efficiently, real-time video, high-definition video.

1 schematically shows an example of the structure of an image encoding apparatus.
2 schematically shows an example of the structure of a video decoding apparatus.
Fig. 3 is a view for schematically explaining how data is divided into CU units when processing. Fig.
4 is a diagram illustrating a process of dividing a CU in the LCU in more detail.
5 is a view for explaining an example in which one CU is divided into several types of PUs.
FIG. 6 is a diagram schematically showing various types of PUs that can be divided from one CU.
7 is a diagram illustrating an image encoding result for a test sequence.
8 is a flowchart of an image encoding method according to an embodiment of the present invention.

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

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

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

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

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

1 schematically shows an example of the structure of an image encoding apparatus.

1, the image encoding apparatus 100 includes a motion prediction unit 111, a motion compensation unit 112, an intra prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, A quantization unit 140, an entropy encoding unit 150, an inverse quantization unit 160, an inverse transformation unit 170, an adder 175, a filter unit 180, and a reference image buffer 190.

The image encoding apparatus 100 performs encoding in an intra mode or an inter mode with respect to an input image and outputs a bit stream. In the embodiment of the present invention, intra prediction can be used in the same way as inter prediction, and inter prediction can be used in the same meaning as inter prediction. The intra prediction method and the inter prediction method may be selectively used for the prediction unit in order to determine an optimal prediction method for the prediction unit. The image encoding apparatus 100 generates a prediction block for the original block of the input image, and then encodes the difference between the original block and the prediction block.

In the intra-picture prediction mode, the intra-prediction unit 120 (or the intra-picture prediction unit can also be used as a term having the same meaning) performs spatial prediction using pixel values of already coded blocks around the current block And generates a prediction block.

In the case of the inter-picture prediction mode, the motion prediction unit 111 finds a motion vector by searching an area of the reference picture stored in the reference picture buffer 190, which is best matched with the input block, in the motion prediction process. The motion compensation unit 112 generates a prediction block by performing motion compensation using a motion vector.

The subtracter 125 generates a residual block by a difference between the input block and the generated prediction block. The transforming unit 130 performs a transform on the residual block to output a transform coefficient. The quantization unit 140 quantizes the input transform coefficient according to the quantization parameter and outputs a quantized coefficient. The entropy encoding unit 150 entropy-codes the input quantized coefficients according to a probability distribution to output a bit stream.

Since the HEVC performs inter prediction coding, i.e., inter prediction coding, the currently encoded image needs to be decoded and stored for use as a reference image. Accordingly, the quantized coefficients are inversely quantized in the inverse quantization unit 160 and inversely transformed in the inverse transformation unit 170. The inverse quantized and inverse transformed coefficients are added to the prediction block through the adder 175 and a reconstruction block is generated.

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

2 schematically shows an example of the structure of a video decoding apparatus.

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

The video decoding apparatus 200 receives the bit stream output from the encoder and decodes the video stream into an intra mode or an inter mode, and outputs a reconstructed video, i.e., a reconstructed video. In the intra mode, a prediction block is generated using an intra prediction mode, and a prediction block is generated using an inter prediction method in an inter mode. The video decoding apparatus 200 obtains a residual block from the input bitstream, generates a prediction block, and then adds the residual block and the prediction block to generate a reconstructed block, that is, a reconstruction block.

The entropy decoding unit 210 entropy-decodes the input bitstream according to a probability distribution and outputs a quantized coefficient. The quantized coefficients are inversely quantized in the inverse quantization unit 220 and inversely transformed in the inverse transformation unit 230. As a result of inverse quantization / inverse transformation of the quantized coefficients, a residual block is generated.

In the intra-picture prediction mode, the intra-prediction unit 240 (or the inter-picture prediction unit) performs spatial prediction using the pixel values of the already coded blocks around the current block to generate a prediction block.

In the inter-view prediction mode, the motion compensation unit 250 generates a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference image buffer 270.

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

Methods for improving the prediction performance of the encoding / decoding apparatus include a method of increasing the accuracy of the interpolation image and a method of predicting the difference signal. Here, the difference signal is a signal indicating the difference between the original image and the predicted image.

In the present invention, the term " difference signal " may be replaced by a " difference signal ", " residual block ", or " difference block " depending on the context. Those skilled in the art may influence the idea You will be able to distinguish this within the scope of not giving.

In the embodiment of the present invention, a coding unit (CU) is used as a coding unit for convenience of explanation, but it may be a unit for performing not only coding but also decoding. Hereinafter, the video encoding method described with reference to FIGS. 3 to 5 according to an embodiment of the present invention may be implemented according to the functions of the respective modules described above with reference to FIGS. 1 and 2, and such an encoder and a decoder are within the scope of the present invention. Included. That is, the image encoding / decoding method to be described later in the embodiment of the present invention can be performed in each component included in the image encoder and the image decoder described in FIG. 1 and FIG. The meaning of the constituent part may include not only a hardware meaning but also a software processing unit which can be performed through an algorithm.

In the image encoding / decoding according to the embodiments of FIGS. 1 and 2, a CU structure in which a single-sized macro block is expanded to various sizes may be defined for efficient encoding of an image. The CU is a unit in which a video is encoded by a video encoder and can be hierarchically divided with depth information based on a quad tree structure. CUs can have various sizes such as 8 × 8, 16 × 16, 32 × 32, and 64 × 64. The largest CU is called the LCU (Largest Coding Unit), and the smallest CU is called the SCU (Smallest Coding Unit). All CUs except SCUs are assigned split_flag information and indicate whether or not the corresponding CU is divided according to the value of split_flag. The encoder may adjust the size of the LCU in the encoding process according to various video signal characteristics.

FIG. 3 is a diagram for explaining a CU, which schematically illustrates performing division in units of CU when processing data.

Referring to FIG. 3, an image is divided into basic CU units defined beforehand, and then the CU is divided while being divided. Starting with the LCU, the size of the block can be divided into four CUs, reduced by half the length, if necessary. The division of the CU is determined according to the characteristics of the image on the coding side. In the case of a complex image, it may be divided into smaller CUs, and in a case of uncomplicated images, it may not be divided into small CUs. Therefore, it can be said that whether the CU is divided or not is determined according to efficiency in terms of compression efficiency and image quality.

The information on whether to split the CU is expressed through a split flag. This split information is included in all the CUs except the smallest unit CU that can not be further divided. If the value of the split information (split_flag) is '0', the split CU is not divided and the split information ) Is '1', the corresponding CU is hierarchically divided into four small CUs divided into two halves.

Each time the CU is divided, the depth is increased by one. CUs of the same size can have the same depth. The maximum depth of a CU can be predefined, but the CU can not be split beyond a predefined maximum depth. Therefore, the CU segmentation can be divided until the depth reaches the maximum depth by increasing the depth by 1 while splitting the CU from the LCU with a depth of 0.

Referring to FIG. 3, for a CU (LCU) having a depth of 0, if the division information value is 0, it is not further divided and divided into four smaller CUs if the division information value is 1 . At this time, indexes (0, 1, 2, 3) may be assigned to the divided small CUs to be distinguished.

When split, the depth increases. The example of Fig. 3 is a case where the maximum depth is set to 4, and as shown, if divided up to the maximum depth of 4, it is not further divided.

FIG. 3 is a diagram schematically illustrating the division of the CU according to the depth when the LCU is 2N × 2N pixels (N = 64) and the maximum depth is 4. FIG. For convenience of explanation, the case where the LCU is 128x128 has been described as an example, but the present invention is not limited to this, and the LCU may be defined as another size.

4 is a diagram illustrating a process of dividing a CU in the LCU in more detail.

According to FIG. 4, the case where the size of the LCU 400 is 64x64 pixels and the maximum depth is 3 will be described as an example. When the encoding is not performed in units of 64x64 pixels, '1' indicating that splitting is performed as a split flag value of the 64x64 pixel CU is stored. Thus, a 64x64 pixel CU is divided into four CUs of 32x32 pixels that are small in width and length.

When the 32x32 pixel CUs 410, 420, and 430 divided in the 64x64 pixel CU are no longer divided, '0' indicating that they are not divided as the split information value is stored. In this case, the CUs 410, 420, and 430 may be encoded in an intra or inter mode in units of 32 × 32 pixels.

When the 32x32 pixel CU 440 is divided into four smaller 16x16 pixel CUs, '1' is stored as the split information value for the CU 440, and encoding is performed on four 16x16 pixel CUs. Even if the preset maximum depth is 3, if the 16x16 pixel CU is set to the smallest CU (depth 2), it may not be split any more and thus may not include split information. If the 16x16 pixel CU is not set to the smallest CU, '0' is stored as the split information when the 16x16 pixel is no longer divided.

FIG. 5 is a diagram schematically illustrating an example in which a single CU is divided into a prediction unit (PU).

FIG. 5A schematically shows one CU 510.

5B illustrates an example in which one CU is divided into two PUs. For example, the CU 520 may be divided into two PUs 525 and 530 having the same width as the CU 520 and half the height. In addition, the CU 535 can be divided into two PUs 540 and 545 having the same height as the CU 535 and a half width.

5C illustrates an example in which one CU is divided into four PUs. For example, the CU 550 may be divided into four PUs 555, 560, 565, and 570 whose width and height are half of the CU 550.

FIG. 6 is a diagram schematically showing various types of PUs that can be divided from one CU.

Referring to FIG. 6, a PU 610 in the case where one CU block is encoded by itself is denoted by " PART_2Nx2N ". Where N is an integer greater than 0, 2N is the number of pixels and represents the width and / or height of the block.

When one CU is coded into two PUs, two PUs 620, which are " PART_2NxN ", two PUs 630, " PART_Nx2N & Two PUs 660 of "PART_2NxnD", two PUs 670 of "PART_nLx2N", two PUs 680 of "PART_nRx2N", and the like. Where U, D, L, and R are terms used instead of N to distinguish asymmetric shapes from symmetric shapes, respectively.

When one CU is coded into four PUs, it can be divided into four PUs 640 which are " PART_NxN ".

As shown in FIGS. 3 to 6, the HEVC encoder uses a unit called CU in encoding. After encoding all possible CU unit depths, the rate-distortion cost (RD-Cost) is the highest. Since the CU depth is selected and encoded in a low case, it can be used as reliable information indicating the complexity characteristics of the LCU. In order to achieve the above object, the maximum depth of the CU depth of the LCU is used as the information. When the CU depth is 0, it means that the LCU of 64x64 size is not divided. When the CU depth is 1, it means that it is divided into 32x32 size. When the CU depth is 2, it means that the CU is divided into 16x16 size, and if it is 3, it means that the CU is divided into 8x8 size.

The rate-distortion optimization process of each CU is performed through inter or intra picture prediction, which is determined using a block of a unit called PU.

7 is a diagram illustrating an image encoding result for a test sequence.

The sequence used for the test is the Basketball drill test sequence, and the encoding result using HM-7.1.

In FIG. 7, each rectangle represents each CU, the largest rectangle means that the LCU itself is not divided, and the smallest rectangle represents an SCU subdivided to the maximum depth. That is, as a result of performing encoding on all CU sizes, a partition structure having the most compression efficiency is shown as shown in FIG. 7. In general, CUs are subdivided when the activity, complexity, or motion of the region is high. On the contrary, in the case of a low-motion or flat region, coding is performed by a large CU.

Therefore, the CU depth of the LCU includes information about the complexity or the degree of movement of the area.

In FIG. 7, (A) shows the CU splitting result of CUVC encoding, (B) shows a CU having a size of 64x64 or 32x32, and (C) shows a case where a PU among 64x64 or 32x32 sizes has a symmetric size. It is shown.

According to the encoding result, it can be seen that in the case of a relatively large CU such as 64x64 or 32x32, a PU having a symmetric size is often selected rather than a PU having an asymmetric size. As a result of the coding result, the probability of selecting a PU having a symmetrical size is about 88%, and the probability of selecting an asymmetric PU is very low (12%). In addition, since the loss in the rate-distortion point of time when the portion encoded by the asymmetric PU is encoded by the symmetric PU is also insignificant, there is no significant loss in compression efficiency even when the PU is encoded only in the symmetrical size. Able to know.

8 is a flowchart of an image encoding method according to an embodiment of the present invention.

Referring to FIG. 8, the image encoding method according to an embodiment of the present invention includes comparing the depth information of the current CU with a threshold (S110) and performing prediction encoding according to the result of the comparing step (S110). (S120, S130).

Before the comparison step (S110), depth information of the current CU should be acquired, which can be known through depth information included in the CU. The depth information can also be known from the size of the CU. If the CU size is 64x64 LCU, the depth is 0, if the 32x32, it can be seen that the depth is 1.

The prediction encoding process is changed through the step of comparing the acquired current CU depth information with the threshold (S110).

That is, when the depth information of the current CU is smaller than the threshold, the prediction encoding step S120 is performed with the size of the symmetrical prediction unit (PU), and when the depth information of the current CU is larger than the threshold, the symmetric PU size and asymmetry are performed. The predictive encoding step S130 is performed using the PU size.

The predictive encoding steps S120 and S130 are performed through inter or intra prediction. The size of the symmetric prediction unit may be 2N × 2N (where N is an integer greater than 0 and 2N is the number of pixels), two 2N × N or two N × 2N, or four N × N.

The size of the asymmetric prediction unit is composed of two, 2NxnU, 2NxnD, nLx2N, nRx2N (where N is an integer greater than 0, 2N is the number of pixels, U, D, L, R is the top of the coding unit, It may be a unit representing the length of the bottom, left, and right, and may be an integer different from N).

On the other hand, the threshold is preferably set to 2. When set to 2, when the CU depth information is 0 or 1, that is, when the size of the CU is 64x64 or 32x32, prediction encoding of an asymmetric PU size is omitted so that a simpler and faster image encoding method can be provided. do.

When the prediction encoding steps S120 and S130 are completed, the data is divided into the next CU depths (S140), and the comparison step S110 and the prediction encoding steps S120 and S130 are recursively performed.

After the prediction encoding steps S120 and S130 of the current CU are completed at various depths, rate-distortion optimization is performed, and then the current CU is encoded. Rate-distortion optimization is a step of determining an optimal mode. The CU is encoded in units of PUs and a rate-distortion cost is calculated for the encoded image. The rate-distortion cost is used to determine both the distortion and the data rate of the encoded image. It is calculated in consideration. The prediction mode having the lowest rate-distortion cost is selected as the optimal prediction mode.

When encoding of all CUs in the LCU is performed (S150), image encoding is performed by repeating the same process for the next LCU.

In the image encoding method according to an embodiment of the present invention, a high-speed image encoding is possible by omitting a prediction step of a PU size having an asymmetric size by comparing a threshold value and a depth of a current CU (S110).

As described above, the analysis of the tendency of the Coding Unit Depth data obtained in the encoding process of the HEVC encoder of the present invention is omitted, since the probability of selecting a PU having an asymmetric size is very low for a large CU. Although the decrease in the compression efficiency is low, the result is inferred from the characteristics that the encoding speed can be improved.

Table 1 and Table 2 below compare the results using the conventional video encoding method and the video encoding method according to an embodiment of the present invention.

kbps Y psnr encoding time (sec) averege (sec) Basketball
Drill 3894.14 40.11 10216.96 8766.02 1796.06 36.91 9155.55 856.14 34.03 8252.20 436.02 31.56 7439.35 BQMall 4557.58 39.96 11221.19 9563.35 1969.94 37.10 9867.58 939.45 34.17 8980.77 471.40 31.30 8183.85 PartyScene 9203.12 38.15 11045.71 8900.61 3660.82 34.30 9279.05 1549.80 30.94 8148.34 654.22 27.76 7129.36 RaceHorsesC 6020.66 39.81 8890.58 7448.09 2349.48 36.04 7814.34 1017.73 32.90 6963.23 464.50 30.08 6124.23 average 2496.24 34.69 6917.27 8669.52

(Encoding result of conventional video encoding method)

kbps Y psnr encoding time (sec) averege (sec) BD-Rate Basketball
Drill 3897.93 40.11 8244.29 6929.04 0.43 1798.94 36.91 7252.59 860.77 34.02 6481.18 439.81 31.56 5738.11 BQMall 4571.29 39.96 9045.07 7618.05 0.83 1979.96 37.10 7874.60 947.17 34.16 7115.63 476.60 31.28 6436.89 PartyScene 9206.84 38.15 9151.88 7239.00 0.46 3670.91 34.30 7567.95 1556.26 30.93 6553.57 659.46 27.75 5682.58 RaceHorsesC 6025.75 39.81 7153.91 5882.98 0.63 2354.70 36.04 6223.47 1023.99 32.89 5473.49 469.45 30.06 4681.03 average 2496.24 34.69 6917.27 6917.27 0.59

(Encoding Result of Image Encoding Method According to an Embodiment of the Present Invention)

Table 1 and Table 2 show the results of using HM-7.1. Table 2, which is the result of performing the encoding method according to the present invention, has a remaining BD-Rate value of 0.59% compared to Table 1, indicating that the encoding time is reduced by 20% or more without a significant decrease in compression efficiency. .

As described above, since the CU depth information is closely related to the selection of the PU, it is possible to predict the PU encoding according to the CU depth information well in performing encoding, and as a result, it is possible to conclude that the computational complexity can be reduced. have. When the depth of the CU is less than or equal to the threshold, some encoding processes may be omitted, thereby enabling high-speed video encoding.

100: image encoding device 111: motion prediction unit
112: motion compensation unit 120: intra prediction unit
125: subtracter 130:
140: quantization unit 150: entropy coding unit

Claims

In the image encoding method,
Acquiring depth information of the current coding unit;
Comparing depth information with a threshold of the current coding unit; And
And performing predictive encoding according to the result of the comparing step.

The method according to claim 1,
If the depth information of the current coding unit is smaller than the threshold,
An image encoding method for predicting encoding by a symmetric prediction unit size.

The method according to claim 1,
If the depth information of the current coding unit is greater than the threshold,
An image encoding method for predictive encoding by a symmetric prediction unit size and an asymmetric prediction unit size.

The method according to claim 2 or 3,
And the threshold is set to two.

The method according to claim 1,
And the size of the current coding unit is 64x64 or 32x32.

The method according to claim 2 or 3,
The size of the symmetric prediction unit is 2Nx2N, where N is an integer greater than 0, 2N is the number of pixels.

The method according to claim 2 or 3,
The size of the symmetric prediction unit is two 2NxN or two Nx2N, where N is an integer greater than 0, 2N is the number of pixels.

The method according to claim 2 or 3,
The size of the symmetric prediction unit is four NxN, where N is an integer greater than 0, 2N is the number of pixels.

The method of claim 3,
The size of the asymmetric prediction unit is composed of two, 2NxnU, 2NxnD, nLx2N, nRx2N (where N is an integer greater than 0, 2N is the number of pixels, U, D, L, R is the top of the coding unit , An integer different from N in units representing the bottom, left, and right lengths.

The method according to claim 2 or 3,
And dividing into the next coding unit depth after the prediction encoding.

A processor; And
And a memory coupled to the processor and storing information for driving the processor,
And the processor is configured to acquire depth information of the current coding unit, compare the depth information of the current coding unit with a threshold, and then perform prediction encoding according to the result of the comparing step.

The method of claim 11,
If the depth information of the current coding unit is smaller than the threshold,
And predictively encode a symmetric prediction unit.

The method of claim 11,
If the depth information of the current coding unit is greater than the threshold,
And predictively encode the symmetric prediction unit size and the asymmetric prediction unit size.

The method according to claim 12 or 13,
And the threshold is set to two.

The method of claim 11,
And the size of the current coding unit is 64x64 or 32x32.

The method according to claim 12 or 13,
The size of the symmetric prediction unit is 2Nx2N, where N is an integer greater than 0, 2N is the number of pixels.

The method according to claim 12 or 13,
The size of the symmetric prediction unit is two 2NxN or two Nx2N, where N is an integer greater than 0, 2N is the number of pixels.

The method according to claim 12 or 13,
And the size of the symmetric prediction unit is four N × N, where N is an integer greater than 0 and 2N is the number of pixels.

The method according to claim 13,
The size of the asymmetric prediction unit is composed of two, 2NxnU, 2NxnD, nLx2N, nRx2N (where N is an integer greater than 0, 2N is the number of pixels, U, D, L, R is the top of the coding unit , An integer different from N in units representing the bottom, left, and right lengths.

The method according to claim 12 or 13,
And dividing into the next coding unit depth after the prediction encoding.