KR20150057801A - Video coding method for fast intra prediction and apparatus thereof - Google Patents

Abstract

The present invention relates to an intra-prediction method in order to improve the processing speed of the image encoding device. An image encoding method in accordance with the present invention comprises of the following steps: a step to tie together multiple intra-prediction modes for the current prediction units into groups; a step to determine groups which limit the encoding cost to a minimum by calculating sum-of-absolute transform difference-based encoding cost between each of the groups and the current prediction units; and a step to determine an intra-prediction mode which limits the SATD-based encoding cost to a minimum as the final encoding mode.

Description

TECHNICAL FIELD [0001] The present invention relates to a video encoding method and apparatus for fast intra prediction,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image encoding, and more particularly, to an intra prediction method for determining an intra prediction mode having various directional modes at high speed.

Recently, as broadcasting system supporting HD (High Definition) resolution has been expanded not only in domestic but also in the world, many users are accustomed to high resolution and high image quality, and accordingly, many organizations are spurring development for next generation video equipment . In addition, with the increasing interest in UHD (Ultra High Definition) that supports more than four times the resolution of HDTV in addition to HDTV, compression technology for higher resolution and higher image quality is required.

An inter prediction technique for predicting a pixel value included in a current picture from a preceding picture and / or a following picture for compression of an image, intra prediction using a pixel value in a picture to predict a pixel value, An entropy coding technique may be used in which a short code is assigned to a symbol having a high frequency of occurrence and / or appearance frequency, and a long code is assigned to a symbol having a low appearance frequency.

In the case of H.264 coding, intraprediction in the encoder makes a prediction picture by copying neighboring pixels according to 9 directional modes including a DC mode in case of 4x4 luminance pixels, and calculates a prediction error (SATD: Sum of the Absolute Transformed Differences) and determines the mode with the smallest value as the final intra prediction mode.

On the other hand, in HEVC, directional mode (or intra prediction mode) of intraprediction in the case of luminance pixels is divided into PLANAR and DC (as shown in FIG. 1) according to the size (maximum 64x64 to minimum 4x4) of CU Mode and 35 directional modes. In this case, the decoder receives the information on the intra-prediction mode from the encoder and restores the image only for one directional mode. However, the encoder generates a prediction picture for all the directional modes and calculates a minimum prediction error according to the directional mode, Mode.

Therefore, in order to implement 33 intra prediction modes sequentially or in parallel, the encoder requires a considerable amount of computation and time in processing with software, and it also uses a large amount of resources when implementing the intra prediction mode in hardware, .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a video encoding method and apparatus for high-speed intra prediction, in which the amount of computation required to determine an intra-prediction mode is shortened to improve the processing speed.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided an image encoding method for fast intra prediction, comprising: grouping a plurality of intra prediction modes for a current prediction unit into predetermined groups; Calculating a SATD (Sum of Absolute Transform Difference) coding cost between each of the groups and the current prediction unit to determine a group with the lowest coding cost; And determining an intra prediction mode in which the SATD-based coding cost for the current prediction unit is minimized among the intra prediction modes belonging to the determined group, as a final coding mode.

Preferably, the step of grouping into the predetermined groups includes a step of grouping a plurality of intra prediction modes into a predetermined group according to a direction in which prediction is performed.

In another embodiment, the step of grouping into the predetermined group includes, among a plurality of intra prediction modes supported for HEVC intra prediction, the ANGULAR (2) mode and the HORIZONTAL (10) (WS group), the HORIZONTAL (10) mode and the ANGULAR (18) mode adjacent thereto in the clockwise direction are grouped into the second group (WN group), and the ANGULAR (18) mode and the VERTICAL 26) mode to a third group (NW group), and a fourth group (NE group) up to a VERTICAL (26) mode and an ANGULAR (34) mode adjacent thereto in a clockwise direction.

Preferably, the step of determining a group in which the coding cost is minimized may include calculating a SATD-based coding cost for the current prediction unit for a predetermined intra prediction mode among a plurality of intra prediction modes belonging to the respective groups, Calculating a sum of the SATD-based coding costs for the predetermined intra-prediction mode for each of the groups, and determining a group in which the sum of the SATD-based coding costs is minimum .

In another embodiment, the step of determining a group in which the coding cost is minimized may include: determining, for an ANGULAR (2) mode, an ANGULAR (6) mode, and a HORIZONTAL (10) mode among intra prediction modes belonging to the first group, Calculating the sum of the SATD-based coding costs for the current prediction unit and the current prediction for the HORIZONTAL (10), ANGULAR (14), and ANGULAR (18) modes among intra prediction modes belonging to the second group; (22) mode, VERTICAL (26) mode among the intra prediction modes belonging to the third group to the current prediction unit, and calculating the sum of the SATD- (30) mode, ANGULAR (34) mode among the intra prediction modes belonging to the fourth group among the intra prediction modes belonging to the fourth group, Calculating a sum of the SATD-based coding costs, and determining a group in which the sum of the SATD-based coding costs is the smallest among the first to fourth groups.

Preferably, the step of determining a final encoding mode includes determining a group in which the encoding cost is the smallest among the intra prediction modes belonging to the determined group, And calculating SATD-based coding costs for the current prediction unit only for the modes.

In another embodiment, the step of determining a final encoding mode may be performed in an ANGULAR (3) mode, an ANGULAR (4) mode, an ANGULAR (5) mode, an ANGULAR Calculating a SATD-based coding cost for the current prediction unit for a current mode, an ANGULAR (8) mode, and an ANGULAR (9) mode; (3) mode, ANGULAR (4) mode, ANGULAR (5) mode, ANGULAR (7) mode, ANGULAR (8) mode for the ANGULAR mode, the ANGULAR mode and the HORIZONTAL Mode, and ANGULAR (9) mode, which is the minimum among the SATD-based coding costs for the ANGULAR (9) mode.

According to another aspect of the present invention, there is provided an image encoding apparatus for fast intra prediction, the intra prediction method comprising the steps of: performing intra prediction using a pixel value of a coded block around a current block, A prediction unit; And a subtractor for generating a residual block based on a difference between the current block and the prediction block.

Wherein the intra predictor groups a plurality of intra prediction modes for a current prediction unit into predetermined groups; Calculating a SATD (Sum of Absolute Transform Difference) coding cost between each of the groups and the current prediction unit to determine a group with a minimum coding cost; The intra prediction mode in which the SATD-based coding cost for the current prediction unit is minimized among the intra prediction modes belonging to the determined group is determined as the final coding mode.

In a preferred embodiment of the present invention, the intraprediction unit includes a first group (WS group) up to an ANGULAR (2) mode and a HORIZONTAL (10) mode adjacent thereto in a clockwise direction among a plurality of intraprediction modes supported for HEVC intra- And the ANGULAR 18 mode adjacent to the HORIZONTAL 10 mode and the ANGULAR 18 mode adjacent thereto are grouped into the second group WN group and the ANGULAR 18 mode and the VERTICAL 26 mode adjacent thereto clockwise Are grouped into a third group (NW group), and a VERTICAL (26) mode and a clockwise adjacent ANGULAR (34) mode are grouped into a fourth group (NE group).

In a preferred embodiment, the intraprediction unit calculates an SATD-based encoding cost for the current prediction unit for a predetermined intra prediction mode among a plurality of intra prediction modes belonging to the respective groups; Calculating a sum of the SATD-based coding costs for the predetermined intra-prediction mode for each of the groups; And determines the group in which the sum of the SATD-based coding costs becomes minimum.

In another embodiment, the intra-prediction unit may determine a final encoding mode among intra-prediction modes belonging to the determined group, wherein the intra-prediction modes include intra-prediction modes in which a coding cost is calculated, And calculates the SATD-based coding cost for the current prediction unit only for the intra prediction modes.

In another embodiment, when the first group is determined as a group in which the coding cost is minimized, the intra predictor may be configured to select one of an ANGULAR (3) mode, ANGULAR (4) mode, ANGULAR (5) Calculating an SATD-based coding cost for the current prediction unit for a mode (8) mode, an ANGULAR (9) mode; A SATD-based coding cost for the ANGULAR (2) mode, the ANGULAR (6) mode and the HORIZONTAL (10) mode calculated for determining the first group as a group with the minimum coding cost, and the ANGULAR The intra prediction mode which is the smallest among the SATD-based encoding costs for the (4) mode, the ANGULAR (5) mode, the ANGULAR (7) mode, the ANGULAR (8) mode and the ANGULAR (9) mode is determined as the final encoding mode.

As described above, according to the present invention, the intra-prediction mode is determined only in 15 directional modes out of the existing 35 directional prediction modes by predicting a specific direction of the HEVC image encoder and performing intra-prediction only on the predicted direction The computation amount can be reduced to 1/2 or more, thereby realizing a high-speed real-time encoder.

As a result, there is an advantage in that resources of HW / SW necessary for intraprediction of the encoder can be reduced and power consumption can be reduced.

1 shows 33 prediction directions of an intra prediction mode supported by HEVC;
2 is an exemplary diagram showing a configuration of a video encoding apparatus;
3 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.
FIG. 4 is a diagram showing an example of grouping prediction directions of intra prediction modes supported by the HEVC shown in FIG. 1; FIG.
5 illustrates an example of determining a final encoding mode in a group determined according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

2 is an exemplary diagram showing a configuration of a video encoding apparatus.

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

The image encoding apparatus 100 encodes an input image in an intra prediction mode or an inter prediction mode to output a bitstream. Intra prediction is intra prediction, and inter prediction is inter prediction. The image encoding apparatus 100 transitions between the intra prediction mode and the inter prediction mode through the switch 115. [ The image encoding apparatus 100 generates a prediction block for an input block of the input image, and then encodes a residual between the input block and the prediction block.

In the intra-prediction mode, the intra-prediction unit 120 performs spatial prediction using the pixel values of the already-coded blocks around the current block to generate a prediction block.

In the inter prediction mode, the motion predicting unit 111 finds a motion vector in a reference picture stored in the reference picture buffer 190 by searching for a reference block that best matches the input block. The motion compensation unit 112 performs motion compensation using the motion vector to generate a prediction block. Here, the motion vector is a two-dimensional vector used for inter prediction, and represents an offset between the current block of the encoding / decoding and the reference block.

The subtractor 125 generates a residual block based on the difference between the input block and the prediction block, and the transforming unit 130 transforms the differential block to output a transform coefficient. The quantization unit 140 quantizes the transform coefficients and outputs a quantized coefficient.

The entropy encoding unit 150 performs entropy encoding based on the information obtained in the encoding / quantization process to output a bitstream. Entropy encoding reduces the size of a bit stream for a symbol to be encoded by representing a frequently generated symbol in a small number of bits. Therefore, the compression performance of the image can be expected to be improved through entropy encoding. The entropy encoding unit 150 may use an encoding method such as exponential golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC) for entropy encoding.

A picture encoded for use as a reference picture for performing inter prediction coding needs to be decoded and stored again. Accordingly, the dequantizer 160 dequantizes the quantized coefficients, and the dequantizer 170 performs an inverse transform on the dequantized coefficients to output a recovered differential block. The adder 175 adds the reconstructed difference block to the prediction block to generate a reconstructed block.

The filter unit 180 is also referred to as an adaptive in-loop filter. At least one of deblocking filtering, SAO (Sample Adaptive Offset) compensation, and ALF (Adaptive Loop Filtering) Is applied. Deblocking filtering means eliminating block distortion occurring at the block boundary, and SAO compensation means adding a proper offset to pixel values to compensate for coding errors. Also, ALF means performing filtering based on a value obtained by comparing a reconstructed image with an original image.

On the other hand, the reference picture buffer 190 stores a restoration block that has passed through the filter unit 180. [

Hereinafter, a block means a unit of encoding / decoding. In the encoding / decoding process, the image is divided into a predetermined size and then encoded / decoded. Therefore, the block may also be referred to as a macro block (MB), a coding unit (CU), a prediction unit (PU), a transform unit (TU) It may be divided into sub-blocks of smaller size.

Here, the prediction unit means a basic unit of performing prediction and / or motion compensation. The prediction unit can be divided into a plurality of partitions, each of which is called a prediction unit partition. When the prediction unit is divided into a plurality of partitions, the prediction unit partition may be a basic unit of performing prediction and / or motion compensation. Hereinafter, in the embodiment of the present invention, the prediction unit may mean a prediction unit partition.

Meanwhile, JCT-VC, an international video compression standardization organization, is working on standardization of HEVC (High Efficiency Video Coding), a new video compression standard. HEVC introduced various coding methods to go beyond the coding performance of H.264 / AVC, the previous video compression standard.

The intra prediction technique, which is one of the image compression techniques, is a method of predicting a current coding tree block using only spatial surrounding information in a current picture without referring to other temporally different pictures to be. The intra prediction technique not only contributes to enhancement of the coding performance with the inter prediction technique but also enables random access and improves the error tolerance of the encoded bit stream. In HEVC, the number of intraprediction modes is extended up to 35, so that it has higher coding performance than the existing video compression standard.

The image coding method using the intra prediction mode effectively predicts a current block to be coded by referring to already decoded spatial surrounding information and codes only difference values between the predicted block and the current block. The intra prediction mode has a generally lower coding performance than the inter prediction mode because the amount of information available as a reference sample is smaller than temporal surrounding information. However, If the block is difficult to predict, it has better performance than the inter prediction mode.

The most significant feature of the intra prediction technique in the HEVC when compared with the intra prediction technique in the previous video compression standard is that it supports a larger number of prediction modes as shown in Table 1. [

PU size Number of intra prediction modes 4X4 18 8X8 35 16X16 35 32X32 35 64X64 4

H.264 / AVC supports up to 9 intra prediction modes depending on the size of the prediction unit, but HEVC supports up to 35 intra prediction modes. Therefore, intraprediction is performed using more various prediction modes, so that the accuracy of prediction can be enhanced. However, if the number of prediction modes increases, the number of bits allocated to the indicator indicating the prediction mode used by the decoding apparatus also increases simultaneously. Therefore, increasing the number of prediction modes unconditionally improves the coding performance It is not. Although it supports up to 35 intra prediction modes, the high coding performance proves that the intra prediction mode is well designed in the HEVC.

On the other hand, in order to select an optimal encoding mode from a large number of prediction modes, the complexity required for the encoding apparatus has also increased greatly. Therefore, a high-speed intra prediction algorithm capable of maintaining the coding performance while reducing the complexity of the coding apparatus is required.

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

Referring to FIG. 3, an image encoding method according to an embodiment of the present invention includes a step (S10) of grouping a plurality of intra prediction modes into a predetermined group, a step (S20) of determining a group in which a coding cost is minimized And determining a mode in which encoding cost is minimized among the intra prediction modes belonging to the group to a final encoding mode (S30).

In order to perform the fast intra prediction method according to an embodiment of the present invention, the intraprediction unit of the encoding apparatus divides a plurality of intra prediction modes for the current encoding unit (current PU) into a plurality of groups by a predetermined rule S10).

As described above, the HEVC supports the intra prediction mode in 33 directions excluding the DC mode and the PLANAR mode. In the present invention, considering the fact that there is considerable similarity in directionality between the current encoding unit and the neighboring encoding unit to be predicted, prediction is performed by dividing a total of 33 intra prediction modes into four groups. FIG. 4 shows an intra prediction mode of HEVC divided into four groups.

Referring to FIG. 4, the 33 intra prediction modes supported by the HEVC are divided into a first group in the WS direction, a second group in the WN direction, a third group in the NW direction, and a fourth group in the NE direction. Here, the first group includes the ANGULAR (2) mode and the HORIZONTAL (10) mode adjacent thereto in the clockwise direction, the second group includes the HORIZONTAL (10) mode and the ANGULAR And the third group includes up to ANGULAR (18) mode and VERTICAL (26) mode clockwise adjacent thereto. In addition, the fourth group consists of the VERTICAL (26) mode and the ANGULAR (34) mode which is clockwise adjacent thereto. Table 2 below shows the intra prediction modes belonging to each group.

group Intra prediction mode Group 1 2,3,4,5,6,7,8,9,10 Group 2 10,11,12,13,14,15,16,17,18 Group 3 18,19,20,21,22,23,24,25,26 Group 4 26,27,28,29,30,31,32,33,34

Next, the intra predictor calculates an encoding cost based on a Sum of Absolute Transform Difference (SATD) for the current prediction unit for a predetermined intra prediction mode among a plurality of intra prediction modes belonging to the respective groups.

For example, the intraprediction unit computes the SATD-based encoding cost only for mode 2, mode 6, and mode 10 in group 1, and only for mode 10, mode 14, and mode 18 in group 2, mode 18, mode 22 , The coding cost can be calculated only for the mode 26, and for the mode 26, the mode 30, and the mode 34 in the group 4. Here, the modes calculated in each group mean a representative value indicating the directionality of each group.

Then, the intra predictor determines a group in which the sum of the SATD-based coding costs for the modes calculated for each group is the minimum. The group determination step S10 may be referred to as a rough mode decision, and is a procedure for primarily selecting candidates of modes having directions most similar to those of the current prediction unit.

The sum of the SATD-based encoding costs for the modes representing each group can be calculated as shown in Equation 1 below.

Also, the group having the smallest value among the sum of the SATD-based coding costs is determined by the following equation (2).

Here, Coarse Predicted Direction = WS , WN , NW or NE

In operation S30, the intra prediction unit determines an intra prediction mode in which the SATD-based coding cost for the current prediction unit is the smallest among the intra prediction modes belonging to the determined group.

At this time, in step S20, the intra-prediction unit determines a group in which the coding cost is the smallest among the intra-prediction modes belonging to the determined group, for only the remaining intra-prediction modes except for the intra- And calculates a SATD-based coding cost for the current prediction unit.

For convenience of explanation, it is assumed that the prediction direction is WS (group 1).

As shown in FIG. 5, the intra prediction unit performs fine intra prediction only for six directional modes indicated by solid lines. At this time, the intra prediction predictions for the three directions indicated by the dotted lines are not calculated additionally because they are already calculated by CIP (Coarse Intra Prediction, S20). After the intraprediction of the modes indicated by the solid lines is completed, the SATD-based encoding cost with the current prediction unit is calculated.

The intra prediction unit then determines a mode having a minimum prediction error value for the intra prediction modes in all nine directions belonging to the group of predicted directions as the final coding mode. The modes used in determining the group according to step S20 and determining the final encoding mode according to step S30 are described in Table 3 below.

Coarse Intra Prediction mode (S20) Predicted Direction Fine Intra Prediction mode (S30) 2,6,10,
14, 18,
22, 26,
30,34 WS (Group 1) 3,4,5,7,8,9 WN (group 2) 11,12,13,15,16,17 NW (Group 3) 19,20,21,23,24,25 NE (Group 4) 27, 28, 29, 31, 32, 33

Referring to Table 3, the intraprediction unit calculates the SATD-based encoding costs for the modes 2, 6, and 10, calculated in operation S20, and the modes 3, 4, 5, 7, 8, 9 A mode having a minimum value among a total of 9 encoding costs including SATD-based encoding costs for a total of 6 modes is determined as a final encoding mode. For the remaining groups (groups 2, 3, and 4), the final encoding mode is determined in the same manner as group 1, and a specific description thereof is replaced with a description of group 1.

Meanwhile, the intraprediction coding method according to the present invention can be implemented as a computer-readable code on a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording media storing data that can be decoded by a computer system. For example, there may be a ROM (Read Only Memory), a RAM (Random Access Memory), a magnetic tape, a magnetic disk, a flash memory, an optical data storage device and the like. The computer-readable recording medium may also be distributed and executed in a computer system connected to a computer network and stored and executed as a code that can be read in a distributed manner.

 It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (12)

A video encoding method in a video encoding apparatus,
Comprising: grouping a plurality of intra prediction modes for a current prediction unit into predetermined groups;
Calculating a SATD (Sum of Absolute Transform Difference) coding cost between each of the groups and the current prediction unit to determine a group with the lowest coding cost; And
Determining an intra prediction mode in which a SATD-based coding cost for the current prediction unit is minimized among intra prediction modes belonging to the determined group to a final coding mode
Wherein the intra prediction method comprises:
2. The method of claim 1, wherein the grouping into the predetermined groups comprises:
And a step of grouping the plurality of intra prediction modes into a predetermined group according to a direction in which prediction is performed
A method of encoding an image for fast intra prediction.

3. The method of claim 2,
Among the plurality of intra prediction modes supported for HEVC intra prediction, the ANGULAR (2) mode and the HORIZONTAL (10) mode adjacent thereto in the clockwise direction are grouped into the first group (WS group) The ANGULAR 18 mode and the VERTICAL mode 26 adjacent to the ANGULAR mode are grouped into the second group WG group and the ANGULAR mode and the VERTICAL mode, (26) mode and a clockwise adjacent ANGULAR (34) mode to a fourth group (NE group)
A method of encoding an image for fast intra prediction.
2. The method of claim 1, wherein the step of determining a group in which the encoding cost is minimum includes:
Calculating an SATD-based coding cost for the current prediction unit for a predetermined intra prediction mode among a plurality of intra prediction modes belonging to the respective groups;
Calculating a sum of the SATD-based encoding costs for the predetermined intra-prediction mode for each of the groups;
And determining a group in which the sum of the SATD-based coding costs is at a minimum
A method of encoding an image for fast intra prediction.
4. The method as claimed in claim 3, wherein the step of determining a group in which the encoding cost is minimum includes:
Calculating a sum of SATD-based coding costs for the current prediction unit for ANGULAR (2), ANGULAR (6), and HORIZONTAL (10) modes among intra prediction modes belonging to the first group;
Calculating a sum of SATD-based coding costs for the current prediction unit for HORIZONTAL (10) mode, ANGULAR (14) mode and ANGULAR (18) mode among intra prediction modes belonging to the second group;
Calculating a sum of SATD-based coding costs for the current prediction unit for ANGULAR (18), ANGULAR (22), and VERTICAL (26) modes among the intra prediction modes belonging to the third group;
Calculating a sum of SATD-based coding costs for the current prediction unit for VERTICAL (26), ANGULAR (30), and ANGULAR (34) modes among the intra prediction modes belonging to the fourth group;
And determining a group in which the sum of the SATD-based coding costs is the smallest among the first to fourth groups
A method of encoding an image for fast intra prediction.
2. The method of claim 1, wherein determining a final encoding mode comprises:
Determining a group in which the coding cost is the smallest among the intra prediction modes belonging to the determined group is performed only for the intra prediction modes except for the intra prediction modes in which the SATD- Including a step of calculating a coding cost
A method of encoding an image for fast intra prediction.
6. The method of claim 5, wherein the step of determining a final encoding mode comprises:
(3) mode, ANGULAR (4) mode, ANGULAR (5) mode, ANGULAR (7) mode, ANGULAR (8) mode, ANGULAR (9) mode, Calculating a SATD-based coding cost for the current prediction unit for a mode,
(2) mode, the ANGULAR (6) mode, and the HORIZONTAL (10) mode, and the ANGULAR (3) mode and the ANGULAR (4) mode calculated in the step of determining the group in which the coding cost is minimum, Determining an intra prediction mode that is the smallest among the SATD-based encoding costs for the ANGULAR (5), ANGULAR (7), ANGULAR (8), and ANGULAR (9) modes as the final encoding mode that
A method of encoding an image for fast intra prediction. An intra predictor for generating a prediction block by performing spatial prediction using a pixel value of a coded block around a current block to be coded; And
And a subtractor for generating a residual block based on a difference between the current block and the predictive block,
The intra-
Grouping a plurality of intra prediction modes for a current prediction unit into predetermined groups;
Calculating a SATD (Sum of Absolute Transform Difference) coding cost between each of the groups and the current prediction unit to determine a group with a minimum coding cost;
Determining an intra prediction mode in which the SATD-based coding cost for the current prediction unit is the smallest among the intra prediction modes belonging to the determined group to be the final coding mode
For intra prediction of high speed.
9. The apparatus of claim 8,
Among the plurality of intra prediction modes supported for HEVC intra prediction, the ANGULAR (2) mode and the HORIZONTAL (10) mode adjacent thereto in the clockwise direction are grouped into the first group (WS group) The ANGULAR 18 mode and the VERTICAL mode 26 adjacent to the ANGULAR mode are grouped into the second group WG group and the ANGULAR mode and the VERTICAL mode, Grouping the VERTICAL (26) mode and the clockwise adjacent ANGULAR (34) mode into the fourth group (NE group)
For intra prediction of high speed.
9. The apparatus of claim 8,
Calculating an SATD-based coding cost for the current prediction unit for a predetermined intra prediction mode among a plurality of intra prediction modes belonging to the respective groups;
Calculating a sum of the SATD-based coding costs for the predetermined intra-prediction mode for each of the groups;
Determining a group in which the sum of the SATD-based coding costs is the minimum
For intra prediction of high speed.
9. The apparatus of claim 8,
And determining a final encoding mode among the intra prediction modes belonging to the determined group. The method of claim 1, wherein, in determining the final encoding mode among the intra prediction modes belonging to the determined group, only the intra prediction modes except the intra prediction modes, Calculating the SATD-based coding cost for a unit
For intra prediction of high speed.
The apparatus of claim 9, wherein the intra-
(3) mode, ANGULAR (4) mode, ANGULAR (5) mode, ANGULAR (7) mode, ANGULAR (8) mode, ANGULAR (9) mode, Calculating an SATD-based coding cost for the current prediction unit for a mode;
A SATD-based coding cost for the ANGULAR (2) mode, the ANGULAR (6) mode and the HORIZONTAL (10) mode calculated for determining the first group as a group with the minimum coding cost, and the ANGULAR The intra prediction mode which is the smallest among the SATD-based encoding costs for the (4) mode, the ANGULAR (5) mode, the ANGULAR (7) mode, the ANGULAR (8) mode and the ANGULAR
For intra prediction of high speed.

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