KR101631277B1 - Method and apparatus for encoding/decoding image based on skip mode - Google Patents

Abstract

A video encoding and decoding method for comparing a pixel value of a first block with a pixel value of a second block encoded or decoded before the first block of the current slice and encoding or decoding the first block in a skip mode based on the comparison result And an apparatus are disclosed.

Description

[0001] The present invention relates to a method and apparatus for encoding and decoding an image according to a skip mode,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for encoding and decoding an image, and more particularly, to a method and apparatus for encoding and decoding an image on a block-by-block basis.

As wireless network technologies evolve, interconnection between devices over wireless networks is becoming an issue. Many companies are making efforts to secure interconnection technology between devices over wireless networks. Recently, standardization of HD interconnect technology to replace High Definition Multimedia Interface (HDMI) is being conducted through WiHD (Wireless HD). According to WiHD, various devices such as TVs, home theater, DVD players, Blu-ray players and camcorders are interconnected via a wireless network.

According to an aspect of the present invention, there is provided a method and apparatus for encoding and decoding an image on a block basis, and a computer-readable recording medium having recorded thereon a program for executing the method.

According to an aspect of the present invention, there is provided a method of encoding an image, the method comprising: determining whether a pixel value of a first block is equal to a pixel value of a second block encoded before the first block of a current slice; Determining whether to encode one block into a first mode; And selectively encoding the first block in the first mode based on the determination, wherein the first mode is a mode in which the first block is the same as the second block and indicates that the first block is coded in the first mode Information is encoded in place of the pixel value of the first block.

According to another embodiment of the present invention, the encoding step may include a second mode for encoding a predetermined block based on the first mode, a discrete cosine transform based on the determination, and a second mode for encoding a plurality of bit planes and a third mode for encoding a predetermined block based on a bit plane of the first block.

According to another embodiment of the present invention, the information is flag information indicating that the first block is coded according to the first mode.

According to another embodiment of the present invention, the image encoding method further includes encoding flag information indicating that the current slice includes a block encoded according to the first mode.

According to an aspect of the present invention, there is provided a method of decoding an image, the method including decoding a first block of a current block and a second block of the current block, Decoding the information indicating that the first mode is coded; And selectively decoding the first block in accordance with the first mode based on the information, wherein the first mode is one in which the first block is the same as the second block and is coded in the first mode And the information indicating the first block is encoded in place of the pixel value of the first block.

According to an aspect of the present invention, there is provided an image encoding apparatus for determining whether a pixel value of a first block is equal to a pixel value of a second block encoded before a first block of a current slice, A mode decision unit for deciding whether to encode one block in the first mode; And an encoding unit for selectively encoding the first block in the first mode based on the determination, wherein the first mode is a mode in which the first block is the same as the second block and indicates that the first block is encoded in the first mode Information is encoded in place of the pixel value of the first block.

According to an aspect of the present invention, there is provided an apparatus and method for decoding an image, the apparatus comprising: a first block including a first block, a second block, A mode information decoding unit decoding information indicating that the first mode is coded; And a decoding unit for decoding the first block according to the first mode selectively based on the information, wherein the first mode is a mode in which the first block is encoded in the first mode, And the information indicating the first block is encoded in place of the pixel value of the first block.

According to an aspect of the present invention, there is provided a computer-readable recording medium having recorded thereon a program for executing the image encoding method and the image decoding method.

According to the present invention, an image in which the same block is repeated in one frame can be more efficiently encoded and decoded.

1 illustrates an image encoding apparatus according to an embodiment of the present invention.
FIG. 2 illustrates an image encoding unit according to an embodiment of the present invention.
3 is a diagram for explaining a method of determining a skip mode according to an embodiment of the present invention.
FIG. 4 illustrates an image encoding apparatus according to another embodiment of the present invention.
FIG. 5 illustrates a natural mode encoding unit according to an embodiment of the present invention.
6A illustrates a graphic mode encoding unit according to an embodiment of the present invention.
FIG. 6B illustrates a bit plane-based encoding method according to an embodiment of the present invention.
FIG. 7 illustrates an image encoding apparatus according to another embodiment of the present invention.
FIG. 8 illustrates an image decoding apparatus according to an embodiment of the present invention.
FIG. 9 illustrates an image decoding apparatus according to another embodiment of the present invention.
10 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.
11 is a flowchart illustrating an image encoding method according to another embodiment of the present invention.
12 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

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

1 illustrates an image encoding apparatus according to an embodiment of the present invention.

Referring to FIG. 1, an image encoding apparatus 100 according to an embodiment of the present invention includes a mode determination unit 110, an encoding unit 120, and a mode information encoding unit 130.

The mode determination unit 110 determines a mode used for encoding the current block. Technologies for effective connection of devices over a wireless network are intended to transmit and receive high definition content over HD over a wireless network. However, standardization is under way with focus on low memory and low complexity to enable interconnection between various devices. Accordingly, the present invention is directed to a video encoding method according to the related art such as MPEG-1, MPEG-2 and MPEG-4 H.264 / MPEG-4 AVC (Advanced Video Coding) It does not use complicated techniques for increasing the compression ratio.

However, since transmitting pixel values of an image without compressing at all requires a wireless network with a high data rate, this can also be an obstacle to interconnection between various devices. Accordingly, it is possible to guarantee low complexity and an appropriate level of compression rate by encoding and decoding an image using three modes of a skip mode, a natural mode and a graphic mode, which will be described later.

The skip mode is a mode for encoding a current block based on whether the current block is the same as a block adjacent to the current block. The natural mode is a mode for discrete cosine transform (DCT) and a discrete cosine transform And a current block is encoded using a bit plane division. The graphics mode is a mode for encoding a current block using bit plane division if the current block is a block for an artificially generated image such as text. The skip mode, the natural mode and the graphic mode will be described later in detail with reference to FIGS.

The mode determination unit 110 determines which mode among the plurality of modes described above to code the current block. First, the mode determination unit 110 determines whether the current block is the same as or similar to another block of a current slice that has been coded adjacent to the current block. The pixel value of the current block is compared with the pixel value of the previously coded block of the current slice to determine whether they are the same or similar. Will be described in detail with reference to Figs. 2 and 3. Fig.

FIG. 2 illustrates an image encoding unit according to an embodiment of the present invention.

Referring to FIG. 2, the image encoding apparatus 100 encodes an image in slice units, block units, and bit plane units. The current picture 210 is divided into a plurality of slices 212 to 216. [ Can be divided into a plurality of slices (212 to 216) having a length of N. Then, each slice is divided into NxN sized blocks. The block may again be divided into a plurality of bitplanes from the bitplane for the most significant bit to the bitplane for the least significant bit. If the pixel value of the block or the discrete cosine coefficient is represented by M bits, it can be divided into M bit planes.

3 is a diagram for explaining a method of determining a skip mode according to an embodiment of the present invention.

Referring to FIG. 3, the current picture 310 may be divided into a plurality of slices, as described above with respect to FIG. The case where the image coding apparatus 100 codes the slice 320 shown in FIG. 3 will be described as an example.

The mode determination unit 110 of the image encoding apparatus 100 determines whether or not the current block 322 is the same as the previously encoded block 324 adjacent to the current block to encode the current block 322 of the current slice 320, . The current block 322 to be coded is likely to be the same or similar to a previously coded block that is spatially adjacent. Accordingly, if the current block 322 is the same as or similar to the previously encoded block 324 adjacent to the current block 322, the mode determination unit 110 can determine the encoding mode of the current block 322 as a skip mode. The adjacent block 324 may be a block coded immediately before the encoding of the current block.

The determination as to whether the current block 322 and the adjacent block 324 are the same or similar can be performed in various ways. A cost is calculated based on a Sum of Absolute Difference (SAD), a Mean Square Error (MSE), a Signal to Noise Ratio (SNR), a Max Difference, etc. between the current block 322 and the adjacent block 324 And determines whether the current block 322 and the adjacent block 324 are the same or similar according to the calculated cost. As the SAD, MSE, maximum difference approaches '0', it can be determined that the current block 322 and the adjacent block 324 are the same or similar.

The mode determination unit 110 may determine the encoding mode of the current block 322 to be a skip mode only when the current block 322 and the neighboring block 324 are completely the same, (322) may be determined as a skip mode. In other words, the coding mode of the current block 322 may be determined to be a skip mode only when the above-described SAD, MSE, maximum difference, etc. is '0', and even when the current block 322 is less than the predetermined threshold value, And determines the coding mode of the current block 322 as a skip mode.

If the mode determination unit 110 determines that the current block is not the skip mode as a result of determining whether or not the current block is the same as or similar to the current block, the mode determination unit 110 again determines the current block as a natural mode, Mode to be coded. If it is determined that the current block is a natural associative block, that is, a block for an artificially generated image, the encoding mode of the current block is determined to be the natural mode. On the contrary, if the current block is a block for artificially generated images such as text, The encoding mode of the current block is determined to be the graphic mode.

There is no limitation on the criterion for determining whether to encode the current block according to the mode of the natural mode or the graphic mode, and it is possible to determine whether the current block is a block for an artificially generated image by using various algorithms. For example, since an artificial image has a high probability that the same pixel values are distributed in a specific region, the pixel values of the current block are compared, and if the same pixel values are equal to or more than a predetermined number, it is determined that the block is an artificially generated image .

According to another embodiment of the present invention, the current block is encoded according to the natural mode and the graphic mode, and the encoding result is encoded in the natural mode or the graphics mode on the basis of the RD cost (Rate Distortion Cost) Mode, which will be described later in detail with reference to FIG.

When the mode determination unit 110 determines a mode to be used for encoding the current block, the encoding unit encodes the current block according to the encoding mode determined by the mode determination unit 110.

If the current block is the same as or similar to the previously encoded neighboring block and the encoding mode of the current block is determined to be the skip mode, information indicating that the current block is encoded in the skip mode is encoded instead of the pixel value of the current block. The flag information indicating that the current block is coded in the skip mode can be encoded in place of the pixel value of the current block.

The current block can be encoded with 1-bit flag information instead of directly encoding the pixel value of the current block, thereby improving the compression rate of the image. In addition, since the current block is coded in the skip mode, only the block immediately before the current block is referred to, so that the skip mode can be implemented with low complexity.

If it is determined that the current block is not the skip mode because the current block is not the same as or similar to the previously encoded neighboring block, the encoding unit 130 encodes the current block according to the natural mode or the graphic mode. If the mode determining unit 110 determines that the encoding mode of the current block is the natural mode, the current block is encoded according to the natural mode. If the mode determining unit 110 determines the encoding mode of the current block as the graphic mode, . The encoding method according to the natural mode and the graphic mode will be described in detail with reference to FIGS.

FIG. 4 illustrates an image encoding apparatus according to another embodiment of the present invention.

4, an image encoding apparatus 400 according to an exemplary embodiment of the present invention includes a mode determination unit 410, a natural mode encoding unit 420, a graphic mode encoding unit 430, and a mode information encoding unit 440 ). 1, and the natural mode encoding unit 420, the graphic mode encoding unit 430, and the mode information encoding unit 440 correspond to the encoding unit (not shown) of FIG. 1 120).

The mode determination unit 410 determines the encoding mode of the current block. A mode to be used for encoding the current block, among the skip mode, the natural mode and the graphic mode, can be determined.

If the mode determination unit 410 determines the encoding mode of the current block as a skip mode, the mode information encoding unit 440 encodes information indicating that the current block has been encoded in the skip mode. It is possible to encode flag information indicating that the current block has been coded in the skip mode instead of the pixel value of the current block.

If the mode determination unit 410 determines that the encoding mode of the current block is the natural mode, the natural mode encoding unit 420 encodes the current block according to the natural mode. The current block is subjected to discrete cosine transform to generate discrete cosine coefficients, the generated coefficients are divided into a plurality of bit planes, and each bit plane is encoded using a bit plane basis encoding method. Will be described in detail with reference to FIG.

FIG. 5 illustrates a natural mode encoding unit according to an embodiment of the present invention.

5, the natural mode encoding unit 420 according to an embodiment of the present invention includes a transform unit 510, a bit plane selector 520, and a bit plane encoder 530.

The transform unit 510 generates discrete cosine transform coefficients by performing a discrete cosine transform (DCT) on the current block. Discrete cosine transform is merely an example of a method of transforming a pixel value of a pixel domain into a frequency domain to generate coefficients of the frequency domain and it is possible that another method can be used for transforming a current block. A person with knowledge can easily know.

The bit stream for the DC (direct current) coefficient of the discrete cosine transform coefficients generated by the transform unit 510 by discrete cosine transforming the current block is inserted into the bit stream as it is. However, the coefficients of the AC (alternating current) component are encoded according to the bit plane-based encoding method.

The bit plane selector 520 separates the coefficients of the AC component into a plurality of bit planes. From the bit plane constituted by the most significant bits of the coefficients of the AC component to the bit plane constituted by the least significant bits. And separates the coefficients of the AC component of M bits in bit units to generate M bit planes. Separates a first bit plane composed of the most significant bits of the bit strings for coefficients of the AC component, and separates a second bit plane composed of bits following the most significant bit. The separation of the bit planes is repeated up to the least significant bit to separate the M bit planes.

When the bit plane selector 520 separates a plurality of bit planes, the bit plane encoder 530 encodes each of the plurality of generated bit planes using a bit plane based encoding method. There is no limitation on the method of coding the bit plane, and the present invention can be applied to all the bit plane based coding methods according to the related art. Also, according to an embodiment of the present invention, each bit plane can be encoded using a bit mask. It is possible to set a region where significant bits exist in each bit plane using a bit mast and to perform bit plane based encoding only on the set region.

As described above, the method of separating the DC coefficients and the AC coefficients separately and coding them separately has been described with reference to FIG. However, the encoding method described above with reference to FIG. 5 is an exemplary one, and all the methods using the current block using the discrete cosine transform and the bit plane based encoding method can be applied to the natural mode encoding unit 420. FIG.

Referring again to FIG. 4, when the mode determination unit 410 determines the encoding mode of the current block to be a graphic mode, the graphic mode encoding unit 430 encodes the current block according to the graphic mode. The pixel values of the current block are divided into a plurality of bit planes and each bit plane is encoded using a bit plane basis coding method. Will be described in detail with reference to Figs. 6A and 6B.

6A illustrates a graphic mode encoding unit according to an embodiment of the present invention.

Referring to FIG. 6A, the graphic mode encoding unit 430 includes a bit plane selecting unit 610 and a bit plane encoding unit 620.

The bit plane selector 610 separates the pixel values of the current block into a plurality of bit planes. Separates pixel values of P bits in a bit unit, and generates P bit planes from a bit plane constituted by the most significant bits of the pixel value to a bit plane constituted by the least significant bits of the pixel value.

When the bit plane selecting unit 610 separates a plurality of bit planes, the bit plane encoding unit 620 encodes each of the generated plurality of bit planes using a bit plane based encoding method.

FIG. 6B illustrates a bit plane-based encoding method according to an embodiment of the present invention.

Referring to FIG. 6B, the bit plane encoding unit 620 encodes bit planes by grouping the same bit values. For example, when the size of the block is 4x4 and the pixel value is 8 bits, the bit plane encoding unit 620 first encodes the bit plane for bit 7, which is the most significant bit, as shown in FIG. 6B. The bit plane for bit 7 is divided into a group 631 of '0' and a group 632 of '1'. Since the bit plane for the most significant bit 7 does not contain the same bit, '1' is encoded first and '000111111111000' is encoded to indicate the division type.

The bit planes for bit 6 are encoded according to whether groups are again divided by different bit values based on the groups of bits 7. 00 'indicating that the group 631 of' 0 'is not divided because the group 631 of' 0 'and the group 632 of' 1 'are not all divided in the embodiment shown in FIG. 6B, And '01' indicating that the group 632 of '1' is not divided.

In the bit plane for bit 5, the group 632 of bit planes '1' for bit 6 is divided into two groups 634 and 644. Accordingly, '00' indicating that the group of '0' is not divided is encoded first, and '1' is encoded to indicate that the group 632 of '1' is divided. Then, '0000011111' is encoded to indicate the divided form of the group 632 of '1'.

In the bit plane for bit 4, the group 632 of '1' is divided and the group 633 of '0' among the generated groups 633 and 634 is once again divided. Accordingly, '00' is encoded first to indicate that the group 631 of '0' is not divided. 1 'is encoded to indicate that the group 633 of' 0 'among the groups 633 and 634 generated by dividing the group 632 of' 1 'is divided, and the group of' 0 ' ≪ RTI ID = 0.0 > 633). ≪ / RTI > Then, '01' is encoded to indicate that the group 634 of '1' is not segmented.

The bit-plane coding unit 620 codes each bit-plane by repeatedly applying the bit-plane-based coding method based on the bit group generated by grouping the same bit values to the least significant bit.

Referring again to FIG. 4, the mode information encoding unit 440 encodes information on the mode used for encoding the current block. When the mode determination unit 410 determines the encoding mode of the current block as a skip mode, the mode information encoding unit 440 encodes information indicating that the current block has been encoded according to the skip mode. The flag information indicating that the current block has been coded according to the skip mode can be encoded as described above.

If the mode determination unit 410 determines the encoding mode of the current block to be a natural mode or a graphic mode, the mode information encoding unit 440 outputs information indicating that the current block has been encoded according to the natural mode, or information indicating that the current block has been encoded according to the graphic mode Can be encoded. Like the skip mode, flag information indicating that the current block has been encoded according to the natural mode or the graphic mode can be encoded.

In addition, the mode information encoding unit 440 may encode information indicating whether the current slice including the current block includes a block encoded according to a skip mode, a natural mode, or a graphics mode. Since it is the flag information for the current slice, the flag information can be encoded as a syntax element of the current slice.

FIG. 7 illustrates an image encoding apparatus according to another embodiment of the present invention.

7, an image encoding apparatus 700 according to another embodiment of the present invention includes a skip mode determination unit 710, a natural mode encoding unit 720, a graphics mode encoding unit 730, a mode determination unit 730, 740 and a mode information encoding unit 750.

The skip mode determination unit 710 and the mode determination unit 740 correspond to the mode determination unit 110 of FIG. 1 and include a natural mode encoding unit 720, a graphic mode encoding unit 730, and a mode information encoding unit 750 Corresponds to the encoding unit 120 in Fig.

The skip mode determination unit 710 determines whether or not to encode the current block into the skip mode. The pixel value of the current block is compared with the pixel value of the previously encoded block adjacent to the current block. If it is determined that the current block and the adjacent block are the same or similar, the encoding mode of the current block is determined as a skip mode.

When the skip mode determination unit 710 determines the skip mode of the current block encoding mode, the mode information encoding unit 750 encodes information indicating that the current block has been skipped in the skip mode. Flag information indicating that the current block is coded in the skip mode can be encoded by the mode information encoding unit 750 as described above.

If the skip mode determining unit 710 determines that the current block encoding mode is not the skip mode, the natural mode encoding unit 720 and the graphic mode encoding unit 730 encode the current block into the natural mode and the graphic mode, respectively .

The mode determination unit 740 compares the encoding result of the natural mode encoding unit 720 and the encoding result of the graphic mode encoding unit 730 and determines whether to encode the current block into the natural mode or the graphic mode.

The RD cost is calculated based on the result of coding in the natural mode and the result of coding in the graphic mode. The cost is calculated according to the cost = (Rate) + (lambda) x (distortion), and the mode with a small cost is determined as the encoding mode of the current block. 'lambda' can be set differently according to the embodiment, and the selection ratio of the natural mode and the graphic mode can be changed by adjusting 'lambda'.

When the mode determination unit 740 determines the encoding mode of the current block to be the natural mode or the graphic mode, the mode information encoding unit 750 encodes information on the determined encoding mode. Flag information indicating that the current block is coded in the natural mode or flag information indicating that the current block is coded in the graphic mode can be encoded.

In addition, as described above, the mode information encoding unit 750 may encode information indicating whether the current slice includes a block coded according to a skip mode, a natural mode, or a graphics mode, in addition to the mode information of each block.

FIG. 8 illustrates an image decoding apparatus according to an embodiment of the present invention.

Referring to FIG. 8, an apparatus 800 for decoding an image according to an embodiment of the present invention includes a mode information decoding unit 810 and a decoding unit 820.

The mode information decoding unit 810 decodes information on the encoding mode of the current block included in the bitstream. And parses the bitstream to decode information indicating whether the current block is coded in a skip mode, a natural mode, or a graphic mode.

The decoding unit 820 decodes the current block based on the mode information decoded by the mode information decoding unit 810. [ If the current block is coded in the skip mode as the decoding result of the mode information, the current block is restored based on the same or similar block as the current block, i.e., based on the adjacent previously decoded block. Adjacent blocks may be blocks decoded immediately prior to decoding of the current block. If the current block is coded in the natural mode or the graphic mode, the encoding methods described above with reference to FIGS. 5 and 6A are reversed to restore the current block. Will be described in detail with reference to FIG.

FIG. 9 illustrates an image decoding apparatus according to another embodiment of the present invention.

9, the image decoding apparatus 900 according to another exemplary embodiment of the present invention includes a mode information decoding unit 910, a skip mode decoding unit 920, a natural mode decoding unit 930, and a graphics mode decoding unit 940). 8, the skip mode decoding unit 920, the natural mode decoding unit 930, and the graphic mode decoding unit 940 correspond to the mode information decoding unit 810 of FIG. 8, and the mode information decoding unit 910 corresponds to the mode information decoding unit 810 of FIG. 820 < / RTI >

The mode information decoding unit 910 decodes the information on the encoding mode of the current block included in the bitstream like the mode information decoding unit 810 of FIG.

If the decoded mode information is information on the skip mode, the skip mode decoding unit 920 decodes the current block according to the skip mode. And restores the current block based on the previously decoded block adjacent to the current block. The current block can be restored by copying the adjacent block as it is.

If the decoded mode information is information on the natural mode, the natural mode decoding unit 930 decodes the current block according to the natural mode. The natural mode decoding unit 930 first parses the coefficient of the DC component among the discrete cosine coefficients included in the bitstream. Then, the bit plane-based decoding method is used to recover a plurality of bit planes for the coefficients of the AC component among the discrete cosine coefficients. When the reconstructed plurality of bit planes are combined and the coefficients of the AC component are reconstructed, the inverse discrete cosine transform is performed based on the coefficients of the reconstructed AC component and the coefficients of the parsed DC component. As a result of the inverse discrete cosine transform, the current block is restored.

If the decoded mode information is information on the graphics mode, the graphics mode decoding unit 940 decodes the current block according to the graphics mode. And reconstructs a plurality of bit planes for the pixel values of the current block using the bit plane-based decoding method. Then, the reconstructed bit planes are combined to reconstruct the pixel values of the current block.

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

Referring to FIG. 10, in step 1010, the image encoding apparatus 100 or 400 according to an embodiment of the present invention determines whether to encode a current block in a skip mode. The skip mode is a mode for coding information indicating that the current block is coded in the skip mode instead of the pixel value of the current block if the current block and the neighboring blocks are the same or similar.

If it is determined in step 1010 that the current block encoding mode is not the skip mode, the image encoding apparatus 100 or 400 determines in step 1020 whether to encode the current block in the natural mode or in the graphic mode. It is determined whether the current block is a block for a natural image or a block for an artificially created image, and determines whether to encode the current block in the natural mode or in the graphic mode, as described above with reference to the mode determination unit 110 of FIG. do.

In operation 1030, the image encoding apparatus 100 or 400 encodes the current block into a natural mode. If it is determined in step 1020 that the current block is a block for the natural image, the current block is encoded according to the natural mode. The encoding method of the natural mode has been described above with reference to FIG.

In operation 1040, the image encoding apparatus 100 or 400 encodes the current block in the graphic mode. If it is determined in step 1020 that the current block is a block for artificially generated video, the current block is encoded according to the graphics mode. The coding method of the graphic mode has been described above with reference to FIG. 6A.

In operation 1050, the image encoding apparatus 100 or 400 encodes information on the encoding mode used for encoding the current block. If the coding mode of the current block is determined to be the skip mode in step 1010, information indicating that the current block is coded in the skip mode is encoded instead of the pixel value of the current block. If it is determined in step 1010 that the encoding mode of the current block is not skip mode and the current block is coded according to the natural mode or the graphic mode in steps 1030 to 1040, information indicating that the current block is encoded according to the natural mode, And encodes the information indicating that it has been coded according to the following equation.

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

Referring to FIG. 11, in step 1110, the image encoding apparatus 100 or 700 according to an embodiment of the present invention determines whether to encode a current block in a skip mode. Step 1110 corresponds to step 1010 in FIG.

If it is determined in step 1110 that the encoding mode of the current block is not the skip mode, in steps 1120 and 1130, the image encoding apparatus 100 or 700 encodes the current block according to the natural mode and the graphic mode, respectively.

In operation 1140, the image encoding apparatus 100 or 700 determines the encoding mode of the current block by comparing the result of encoding the current block in the natural mode and the encoded result in the graphic mode. (Rate Distortion Cost) is calculated based on the result of encoding in the natural mode and the result of encoding in the graphic mode. The cost calculation result is determined to be the encoding mode of the current block.

In operation 1150, the image encoding apparatus 100 or 700 encodes the information on the encoding mode used for encoding the current block. If it is determined in step 1110 that the encoding mode of the current block is the skip mode, information indicating that the current block is encoded in the skip mode is encoded instead of the pixel value of the current block. If it is determined in step 1110 that the encoding mode of the current block is not a skip mode and the encoding mode of the current block is determined to be the natural mode or the graphic mode in step 1140, information indicating that the current block is encoded according to the natural mode, And encodes the information indicating that it is coded according to the mode.

12 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

Referring to FIG. 12, in operation 1210, an apparatus 800 or 900 according to an embodiment of the present invention decodes information on a coding mode of a current block included in a bitstream. And parses the bit stream to decode the information on the encoding mode indicating which mode the current block has been coded into the skip mode, the natural mode, and the graphic mode.

In operation 1220, the image decoding apparatus 800 or 900 decodes the current block based on the decoded mode information. If the current block is coded in the skip mode as a result of the decoding of the mode information in step 1210, the current block is reconstructed based on the same or similar block as the current block, i.e., based on the adjacent previously decoded block. If the current block is coded in the natural mode or the graphic mode, the encoding methods described above with reference to FIGS. 5 and 6A are reversed to restore the current block.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Modification is possible. Accordingly, the spirit of the present invention should be understood only in accordance with the following claims, and all of the equivalent or equivalent variations will fall within the scope of the present invention. In addition, the system according to the present invention can be embodied as computer-readable codes on a computer-readable recording medium.

For example, an image encoding apparatus and an image decoding apparatus according to an exemplary embodiment of the present invention includes a bus coupled to each unit of the apparatus as shown in Figs. 1, 4, 7, 8 and 9, Lt; RTI ID = 0.0 > and / or < / RTI > It may also include a memory coupled to the bus for storing instructions, received messages or generated messages and coupled to the at least one processor for performing the instructions as described above.

In addition, the computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and a carrier wave (for example, transmission via the Internet). The computer-readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner.

Claims (17)

Determining whether to encode the first block in the first mode by determining whether the pixel value of the first block is the same as the pixel value of the second block encoded before the first block of the current slice;
Selectively encoding the first block into the first mode based on the determination; And
Encoding flag information of 1 bit indicating whether the current slice includes the block encoded in the first mode,
Wherein the first mode is a mode for encoding information indicating that the first block is the same as the second block and is encoded in the first mode instead of the pixel value of the first block. 2. The method of claim 1,
A second mode for encoding a predetermined block based on the first mode, the discrete cosine transformation, and a third mode for encoding a predetermined block based on a plurality of bit planes for pixel values based on the determination; And encoding the first block according to one of the first and second blocks. 3. The method of claim 2,
And flag information indicating that the first block is coded according to the first mode. delete Decoding the information indicating that the first block is coded in the first mode because the pixel value of the first block is the same as the pixel value of the second block encoded before the first block of the current slice; And
And selectively decoding the first block according to the first mode based on the information,
Wherein the first mode is a mode for encoding information indicating that the pixel value of the first block is equal to the pixel value of the second block and is encoded in the first mode instead of the pixel value of the first block,
Wherein the step of decoding the information comprises parsing flag information of one bit indicating whether the current slice includes a block encoded in the first mode. 6. The method of claim 5, wherein the decoding comprises:
A second mode for encoding a predetermined block based on the first mode and a discrete cosine transform based on the information, and a third mode for encoding a predetermined block based on a plurality of bit planes for pixel values And decoding the first block according to one of the first and second blocks. 7. The method of claim 6, wherein decrypting the information comprises:
And parsing flag information indicating that the first block is coded according to the first mode. delete A mode determining unit determining whether to encode the first block in the first mode by determining whether the pixel value of the first block is the same as the pixel value of the second block encoded before the first block of the current slice; And
And an encoding unit for selectively encoding the first block into the first mode based on the determination,
Wherein the first mode is a mode for encoding information indicating that the first block is the same as the second block and is encoded in the first mode instead of the pixel value of the first block,
Wherein the encoding unit encodes 1-bit flag information indicating whether the current slice includes the block encoded in the first mode. The apparatus of claim 9, wherein the encoding unit
A second mode for encoding a predetermined block based on the first mode, the discrete cosine transformation, and a third mode for encoding a predetermined block based on a plurality of bit planes for pixel values based on the determination; And the first block is encoded according to one of the first and second blocks. 11. The apparatus of claim 10, wherein the encoding unit
Wherein the encoding unit encodes flag information indicating that the first block is encoded according to the first mode. delete A mode information decoding unit decoding the information indicating that the first block is encoded in the first mode because the pixel value of the first block is the same as the pixel value of the second block encoded before the first block of the current slice; And
And a decoding unit that selectively decodes the first block according to the first mode based on the information,
Wherein the first mode is a mode for encoding information indicating that the first block is the same as the second block and is encoded in the first mode instead of the pixel value of the first block,
Wherein the decoding unit parses 1-bit flag information indicating whether the current slice includes the block encoded in the first mode. 14. The apparatus of claim 13, wherein the decoding unit
A second mode for encoding a predetermined block based on the first mode and a discrete cosine transform based on the information, and a third mode for encoding a predetermined block based on a plurality of bit planes for pixel values And decodes the first block according to one of the first and second blocks. 14. The apparatus of claim 13, wherein the mode information decoding unit
And parsing flag information indicating that the first block is coded according to the first mode. delete A computer-readable recording medium storing a program for executing the method according to any one of claims 1 to 3 or 5 to 7.

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