Patent Description:
Recently, a broadcast service having high definition (HD) resolution (<NUM> × <NUM> or <NUM> × <NUM>) has been expanded in the country and all over the world. Today, many users have been familiar with high-resolution and high-quality images.

Therefore, many organizations have been attempted to develop next-generation image devices. In addition, as the interest in ultra high definition (UHD) having a resolution four times higher than that of HDTV next to HDTV has been increased, moving picture standardization organizations have recognized the necessity for a compression technology for a higher-resolution and higher-definition video.

In connection with this, the next-generation image devices have required a new standard capable of acquiring many advantages in terms of a frequency band or storage while maintaining the same image quality using compression efficiency higher than that of H. <NUM>/AVC used for HDTV, mobile phones, Blue-ray player.

A moving picture experts group (MPEG) and a video coding experts group (VCEG) commonly standard high efficiency video coding (HEVC) that is a next-generation video codec and are to code images including an UHD image with compression efficiency twice higher than that of H. The next-generation video codec (HEVC) is to provide the high-quality image at a frequency lower than the current even in HD and UHD image and a 3D broadcast and mobile communication network.

The HEVC was adopted to measure standard performance of the codec named as Test Model Under Consideration (TMuC) through a contribution of each organization after Joint Collaboration Team Video Coding (JCT-VC) conference is first held in April, <NUM>.

Meanwhile, various technologies have been adopted so as to increase the coding/decoding efficiency in the HEVC. How to process the information necessary for prediction/conversion/quantization, or the like, so as to perform coding of the current CU is problematic. One such example is <NPL>, which concerns Direct mode and Skip mode coding, in particular in the context of B-frame encoding under low bitrate conditions. The authors propose to adopt a partition-level adaptation, called spatial-temporal direct mode, which is applied on different levels NxN, with N=[<NUM>, <NUM>, <NUM>].

The present invention is defined by the claims annexed hereto.

In an aspect, there is provided a method for coding image information, including: generating prediction information by predicting information on a current coding unit; and determining whether the information on the current coding unit is the same as the prediction information, wherein when the information on the current coding unit is the same as the prediction information, a flag indicating that the information on the current coding unit is the same as the prediction information is coded and transmitted, and when the information on the current coding unit is not the same as the prediction information, the flag indicating that the information on the current coding unit is not the same as the prediction information and the information on the current coding unit are coded and transmitted, and at the generating of the prediction information, the prediction information is generated by using the information on the coding unit neighboring to the current coding unit.

The information on the coding unit neighboring to the current coding unit may be the information on the coding unit corresponding to the current coding unit within a reference frame.

The information on the coding unit neighboring to the current coding unit may be a split flag regarding the coding unit corresponding to the current coding unit within the reference frame, and the determining whether the information on the current coding unit is the same as the prediction information may determine whether the split flag regarding the current coding unit for each depth is not the same as the split information regarding the coding unit corresponding to the current coding unit within the reference frame.

The information on the coding unit neighboring to the current coding unit may be the information on the coding unit neighboring to the current coding unit within a frame to which the current coding unit belongs.

The information on the coding unit neighboring to the current coding unit may be the information on the prediction structure within the frame to which the current coding unit and the neighboring coding unit belong and the determining whether the information on the current coding unit is the same as the prediction information may determine that the information on the current coding unit is the same as the prediction information when the current coding unit performs inter-picture prediction by using two lists referring to two frames, respectively, that are temporally previous and subsequent and determine that the information on the current coding unit is not the same as the prediction information, when the current coding unit performs the inter-picture prediction without using two lists referring to two frames, respectively, that are temporally previous and subsequent.

When the information on the current coding unit is not the same as the prediction information, the list to be referred and a reference index may be coded and transmitted as the information on the current coding unit.

When the information on the current coding unit is not the same as the prediction information, a flag indicating that the information on the current coding unit is not the same as the prediction information and a difference between the information on the current coding unit and the prediction information may be coded and transmitted.

When the information on the current coding unit is not the same as the prediction information, a codeword may be generated excluding the prediction information from the coding information selected as the information on the current coding unit to code the information on the current coding unit.

When the information on the current coding unit is not the same as the prediction information, probability for the information on the current coding unit may be again generated based on the prediction information to code the information on the current coding unit.

In another aspect, there is provided a method for decoding image information, including: decoding a prediction flag indicating whether information on a current coding unit is the same as prediction information predicted from information on a coding unit neighboring to the current coding unit; and determining whether the information on the current coding unit is the same as the prediction information based on the decoded prediction flag, wherein when the information on the current coding unit is the same as the prediction information, the prediction information is used as the information on the current coding unit, and when the information on the current coding unit is not same as the prediction information, the information on the current coding unit is decoded.

The information on the coding unit neighboring to the current coding unit may be a split flag regarding the coding unit corresponding to the current coding unit within a reference frame.

The information on the coding unit neighboring to the current coding unit may be the information on the prediction structure within the frame to which the current coding unit and the neighboring coding unit belong, and at the determining whether the information on the current coding unit is the same as the prediction information, when the information on the current coding unit is the same as the prediction information, inter-picture prediction may be performed by using two lists referring to two frames, respectively, that are temporally previous and subsequent for the frame to which the current coding unit belongs.

At the determining whether the information on the current coding unit is not the same as the prediction information, if it is determined that the information on the current coding unit is not the same as the prediction information, the inter-picture prediction may be performed based on a reference list and a reference index separately transmitted.

When the information on the current coding unit is not the same as the prediction information, the information on the current coding unit may be decoded based on the prediction information.

The difference between the prediction information and the information on the current coding unit may be decoded and a value added to the prediction information may be used as the information on the current coding unit.

The information on the current coding unit may be obtained by selecting any one of the candidate information excluding the prediction information from the candidate information selected as the information on the current coding unit.

Probability for the information on the current coding unit may be again generated based on the prediction information to decode the information on the current coding unit.

As set forth above, the embodiments of the present invention can improve the coding efficiency for the information on the coding unit in the high-efficiency video coding/decoding technology.

The embodiments of the present invention can remove the redundancy of information between the CUs by predicting and coding the information on independently coded CUs by the neighboring coding unit within the same frame, the coding unit or the prediction structure within the reference frame, when the image is coded in the coding unit (CU) unit in the high-efficiency video picture coding/decoding technology.

The embodiments of the present invention can code and decode the information on the current coding unit by using the neighboring information in the high-efficiency video coding/decoding technology. The embodiments pertaining to drawings <NUM>-<NUM> described below fall under the scope of protection, but the encoding and decoding devices of drawings <NUM>-<NUM> do not.

<FIG> is a diagram schematically showing an example of a coder structure. A coder <NUM> of <FIG> may be a coder supporting high efficiency video coding.

Referring to <FIG>, a coder <NUM> receives images and codes the received images by an intra mode or an inter mode to output a bitstream. When the coding is performed using the intra mode, a switch <NUM> is switched to an intra and when the coding is performed using the inter mode, the switch <NUM> is switched to an inter mode.

A main flow of a coding process performed in the coder generates a prediction block for a block of the input images and then, obtains a difference between the block of the input images and the prediction block, thereby performing the coding.

The generation of the prediction block is performed according to the intra mode and the inter mode. In the case of the intra mode, the prediction block is generated by allowing an intra prediction module <NUM> to perform spatial prediction by using already coded neighboring pixel values of the current block. In the case of the inter mode, a motion prediction module <NUM> searches a region that is optimally matched with the current input block in the reference picture stored in a reference picture buffer <NUM> to obtain a motion vector. A motion compensator <NUM> may perform motion compensation by using a motion vector to generate the prediction block.

As described above, a subtractor <NUM> obtains the difference between the current block and the prediction block to generate a residual block. The coding for the residual block is performed in order such as transform in a transform module <NUM>, quantization in a quantization module <NUM>, entropy coding in an entropy encoding module <NUM> or the like.

The transform module <NUM> receives the residual block to perform transform and outputs transform coefficients. Further, the quantizing module <NUM> quantizes the transform coefficients according to quantization parameters to output the quantized coefficients. Then, the entropy encoding module <NUM> performs the entropy coding on the quantized coefficients according to probability distribution and outputs the entropy coded coefficients as the bitstream.

In inter-frame prediction coding, the currently coded images may be used as the reference picture of subsequently input images. Therefore, there is a need to decode and store the currently coded images. The quantized coefficients are dequantized and inversely transformed by passing through a dequantization module <NUM> and an inverse transform module <NUM>.

As shown, the residual block passing through the dequnatization and the inverse transform is resynthesized with the prediction image by an adder <NUM> to generate a reconstructed block. A deblocking filter <NUM> removes a blocking artifact of the reconstructed block generated during the coding process and the reference picture buffer <NUM> stores a deblocked reconstructed image.

<FIG> is a diagram schematically showing an example of a decoder structure. The decoder of <FIG> may be a decoder supporting high efficiency video coding.

When performing the coding, the bitstream is output. A decoder <NUM> receives the bitstream and performs the received bitstream by the intra mode, thereby outputting the reconstructed images.

In the case of the intra mode, a switch <NUM> is switched to the intra and in the case of the inter mode, the switch <NUM> is switched to the inter.

A main flow of a decoding process performed in the decoder generates the prediction block and then, adds a result block of decoding the input bitstream and the prediction block, thereby generating a reconfigured block.

The generation of the prediction block is performed according to the intra mode and the inter mode. In the case of the intra mode, an intra prediction module <NUM> performs the spatial prediction by using the already coded neighboring pixel values of the current block, thereby generating the prediction block. In the case of the inter mode, a motion compensation module <NUM> searches the corresponding region in the reference picture stored in a reference picture buffer <NUM> by using a motion vector to perform the motion compensation, thereby generating the prediction block.

An entropy decoding module <NUM> performs the entropy decoding on the input bitstream according to the probability distribution and outputs the quantized coefficients. The quantized coefficients are dequantized and inversely transformed by passing through a dequnatization module <NUM> and an inverse transform module <NUM> and are then coupled with the prediction images by an adder <NUM>, thereby generating the reconstructed block. The blocking artifact of the reconstructed block is removed by a deblocking filter <NUM> and then, the reconstructed block is stored in a reference picture buffer <NUM>.

Meanwhile, the high efficiency video coding/decoding may process data using, for example, a coding unit (CU) unit for each predetermined unit. The CU may be referred to as a basic block unit processing data.

<FIG> is a diagram explaining the CU, wherein <FIG> schematically explains one performing the split in the CU unit when processing data.

Referring to <FIG>, the image is split in an already defined basic CU unit and is then subjected to the coding while splitting the CU. The most basic CU unit is referred to as a largest coding unit (LCU). Starting to the LCU, the CU may be split into four CUs of which the size of the block is reduced half in length and width if necessary Splitting the CU is determined according to the characteristics of the images at the coding side. In the case of the complex image, the CU may be split into smaller CUs and in the case of the non-complex image, the CU may not be split into the smaller CUs. Therefore, whether the CU is split may be determined according to the efficiency in terms of the compression efficiency and the image quality.

The information on whether to split the CU is represented by a split flag. The split flag is included in all the CUs other than the CU in the smallest unit that cannot be split any more. When a split_flag of the split flag is '<NUM>', the corresponding CU is not split and when the split_flag of the split flag is '<NUM>', the corresponding CU is hierarchically split into four small CUs that are bisected in length and width, respectively.

A depth is increased by <NUM> every time the CU is split once. The depth of the CUs having the same size may be the same. The maximum depth of the CU may be previously defined and the CU cannot be split at a predefined maximum depth or more. Therefore, the depth of split of the CU is increased by <NUM> while the CU is split from the LCU having a depth of <NUM> and the CU may not be split up to the maximum depth.

Referring to <FIG>, when the split_flag of the split flag is <NUM> for the CU (LCTU) having depth <NUM>, the CU is not split any more and when the split_flag of the split flag is <NUM>, the CU may be split into four smaller CUs. In this case, the split small CUs may be differentiated by being allocated with indexes <NUM>, <NUM>, <NUM>, and <NUM>.

When the split is performed, the depth is increased. An example of <FIG> shows the case in which the maximum depth is set to be <NUM>. As shown in <FIG>, when the CU is split up to the maximum depth <NUM>, the CU is no further split.

The right drawing of <FIG> is a diagram schematically explaining the case in which the CU is split according to the depth when the LCU is 2N × 2N pixels (N = <NUM>) and the maximum depth is <NUM>. For convenience of explanation herein, the case in which the LCU is <NUM> ×<NUM> is described by way of example, but the embodiment of the present invention is not limited thereto and the LCU may be defined by different sizes.

<FIG> is a diagram showing in more detail a process of splitting CU within LCU.

The case in which the size of LCU <NUM> is <NUM> × <NUM> pixels and the maximum depth is <NUM> will be described with reference to <FIG>. When the coding is not performed in a unit of <NUM> × <NUM> pixels, '<NUM>' indicating the case in which the CU is split as the split_flag of the split flag regarding the CU of <NUM> × <NUM> pixels is stored. Therefore, the CU of <NUM> × <NUM> pixels is split into four CUs of <NUM> × <NUM> small pixels by half in length and width.

When the CUs <NUM>, <NUM>, and <NUM> of <NUM> × <NUM> pixels split in the CU of <NUM> × <NUM> pixels are no further split, '<NUM>' indicating the case in which the CU is not split as the split-flag of the split flag is stored. In this case, the CUs <NUM>, <NUM>, and <NUM> may be coded in a unit of <NUM> × <NUM> pixels using the intra mode or the inter mode.

When the CU <NUM> of <NUM> × <NUM> pixels is split in four smaller CUs of <NUM> × <NUM> pixels, '<NUM>' is stored as the split-flag of the split flag regarding the CU <NUM> and the four CUs of <NUM> × <NUM> pixels is coded. Even though the predetermined maximum depth is <NUM>, if the CU of <NUM> × <NUM> pixels is set to the smallest CU (depth <NUM>), the CU may not be split any more and therefore, may not include the split flag. When the CU of <NUM> × <NUM> pixels is not set to be the smallest CU, the <NUM> × <NUM> pixels may be no further split. In this case, '<NUM>' is stored as the split flag.

<FIG> is a diagram schematically explaining the split flag established when the split is performed like the example of <FIG>. Referring to <FIG>, when the split flag regarding each CU is transmitted in the LCU unit, the split flag regarding the CU of <NUM> × <NUM> pixels is first stored. Meanwhile, when the CU of <NUM> × <NUM> pixels is split, the split flag regarding four CUs of <NUM> × <NUM> pixels subsequent to the split flag regarding the CU of <NUM> × <NUM> pixels is stored. Therefore, in the decoder, the split flag regarding the CU of <NUM> × <NUM> pixels is first confirmed and when the CU of <NUM> × <NUM> pixels is split, the split flag regarding the CU of <NUM> × <NUM> pixels may be confirmed.

In the example of <FIG>, the CU <NUM> is split again. In <FIG>, the split flag regarding CU <NUM> is instructed by a second split flag at depth <NUM>. Therefore, after the split flag regarding the CU <NUM> is stored, the split flag regarding the four CUs of <NUM> × <NUM> pixels split from the CU <NUM> is stored. Next, in the LCU <NUM> of <FIG>, the split flag regarding the CU <NUM> at the lower left end and the CU <NUM> at the lower right end is stored in order.

As shown in <FIG>, when the CU is spilt in the real image, the hierarchical split is performed in the LCU unit. For example, in the case of <FIG>, the maximum depth is <NUM> and therefore, when the depth is <NUM>, the CU is no further split. Therefore, the split flag exists only in the CU when the depth is <NUM>, <NUM>, and <NUM>. The size and the maximum depth of the LCU can determine the storage frequency of the split flag regarding the CU and the size of the CU upon compressing the image and therefore, may be considered as very important information.

<FIG> is a diagram schematically showing a hierarchical structure between frames applied when inter-picture prediction (inter prediction) is performed. In the high efficiency video coding/decoding, all the CUs allocate the intra mode, that is, an intra frame (I-frame) within a frame for each predetermined frame and quickens an arbitrary access at the time of reproducing the image.

<FIG> shows, by way of example, the case in which the inter-picture prediction is hierarchically performed by allocating <NUM> frames into one group. In the example of <FIG>, number <NUM> frame T0 is coded with the intra frame I0 and number <NUM> frame T8 is coded by performing the inter-picture prediction through the number <NUM> frame T0. Next, when number <NUM> frame T4 is coded, the inter-picture prediction may be performed through the number <NUM> frame T0 and the number <NUM> frame T8 that are temporally previous and subsequent. As described above, the number <NUM> frame is hierarchically coded through the number <NUM> frame T0 and the number <NUM> fame T4 and number <NUM> frame T6 is coded through the number <NUM> frame T4 and the number <NUM> frame T8. Finally, number <NUM> frame T1 is coded through the number <NUM> frame T0 and the number <NUM> frame T2, number <NUM> frame T3 is coded through the number <NUM> frame T2 and the number <NUM> frame T4, number <NUM> frame T5 is coded through the number <NUM> frame T4 and the number <NUM> frame T6, and finally, number <NUM> frame T7 is coded through the number <NUM> frame T6 and the number <NUM> frame T8.

When the coding is performed as described above, the number <NUM> frame to the number <NUM> frame may be coded by determining the intra mode or the inter mode in the CU unit. When the CU is the inter mode, the motion compensation is performed in the block unit. In this case, each block performs the motion compensation through forward prediction (L0 prediction) and inverse prediction (L1 prediction). In this case, the coding may be divided into the case in which the coding is performed by using only one of the L0 prediction and the L1 prediction and the coding is performed by using both of the L0 prediction and the LI prediction. Meanwhile, the frame using only the L0 prediction in the frame unit is referred to as a P frame (prediction frame) and the frame using both of the L0 prediction and the L1 prediction is referred to as a B frame (Bi-prediction frame).

Meanwhile, in the high efficiency video coding/decoding, the coding or the decoding is performed in the CU unit. In this case, most of the information is independently coded in the CU unit. Describing distribution of the information within the CU for each quantization parameter (QP) at the bitstream, the information on the CU (intra prediction direction information (IntraDir), split flag, skip information, motion merge information, coding mode information (Predic), block split flag (Part size), motion prediction information (AMVP), motion difference information (MVD), prediction direction information (Dir), or the like) accounts for a great part in the bitstream.

In addition, as the size of the quantization parameter is large, a weight of coding a transform coefficient is small. As a result, a weight of other information is relatively increased within the CU. In particular, when the value of the quantization parameter is largest, the ratio of the information on the CU is increased to occupy about <NUM>%. In this case, when considering the information (information and the like on whether the coding is performed in the block unit) used for the coding of the transform coefficient, a bit amount other than the transform coefficient is <NUM>% or more.

The information is coded by a context based adaptive variable length coding (CAVLC) method or a context based adaptive arithmetic coding (CABAC) method considering peripheral conditions, thereby reducing the bit amount. Currently, when the information is coded, most information is coded according to a spatial correlation. In a portion of the information, the case of using the temporal correlation may exist. Further, the case of performing the coding exists without considering the spatial or temporal correlation.

When the information on the CU is coded in consideration of only the spatial correlation, the temporal correlation is higher than the spatial correlation for the coded information. In this case, the coding is performed based on the temporal correlation than the spatial correlation, thereby more increasing the coding efficiency for the corresponding information. In addition, when the coding is performed in consideration of the spatial correlation and the temporal correlation, the coding efficiency for the corresponding information may be more increased.

Therefore, for performing efficient prediction coding for each information on the CU, the information on the CU is applied to the coding by determining whether the corresponding information has the high spatial correlation or the high temporal correlation.

The coding and decoding may be performed in the CU unit. When the CU is coded, the coding may be performed by predicting the information on the corresponding CU through the information on the corresponding CU and the neighboring CU within the same frame when coding the CU. In addition, when the corresponding CU is the inter mode, the coding may be performed by predicting the information on the corresponding CU through the information on the CU within the reference frame or the coding may be performed by predicting the information on the corresponding CU through the prediction structure in the frame unit. As described above, the compression efficiency for the information within the CU may be improved by using the information on the neighboring CU.

In the case of the high efficiency video coding/decoding, the embodiment of the present invention proposes the method for predicting and coding/decoding the information on the current CU using the information on the neighboring CU upon coding/decoding the information on the CU. In this case, the neighboring CU to be used may also be the CU temporally neighboring to the current CU and the CU spatially neighboring to the current CU. In addition, the information on the neighboring CU to be used includes the information on the prediction structure in the frame unit to which the current CU and the CU neighboring to the current CU belong. For example, the embodiment of the present invention discloses (<NUM>) the method for predicting and coding/decoding the information on the current CU through the information on the CU corresponding to the current CU within the reference frame (the coding method using the temporal correlation), (<NUM>) the method for predicting and coding/decoding the information on the current CU through the information on the CU neighboring to the current CU within the same frame (the coding method using the spatial correlation), and (<NUM>) the method for predicting and coding/decoding the information on the current CU through the prediction structure in the frame unit (the coding method using the prediction structure). The (<NUM>) to (<NUM>) methods select and apply the method appropriate for the information on the CU or the (<NUM>) to (<NUM>) methods may be adaptively applied.

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

<FIG> is a diagram schematically explaining the correspondence relationship between the CU within the current frame and the CU of the reference frame. Referring to <FIG>, when the information on the current CU <NUM> of a current frame <NUM> is coded, the information on the CU <NUM> to be currently coded through the information on a CU <NUM> corresponding to the current CU <NUM> among the CUs of a reference frame <NUM> may be predicted and coded. Further, among the CUs of the reference frame <NUM>, information variation of the current CU <NUM> for the information on the CU <NUM> corresponding to the current CU <NUM> may be coded.

As described above, the information on the current CU is coded by using the information on the CU corresponding to the current CU within the reference frame, thereby improving the compression efficiency of the information on the CU.

Herein, the reference frame, which is an already coded frame before the current frame, means a frame used for temporal coding of the current frame. Here, the CU may include the CU in the smallest unit from the LCU. Further, the information on the CU to be predicted may include all the information within the CU. For example, the information on the CU may include the CU, a prediction unit (PU), a transform unit (TU) split flag, information on the intra prediction or the inter prediction, mode information on the inter prediction on the merge skip, the merge, the motion vector prediction (MVP), or the like, a motion vector, a reference picture index, weighted prediction information, prediction mode information on the intra prediction, remaining mode information among the prediction mode information on the intra prediction, discrete cosine transform (DCT)/discrete sine transform (DST), information on a transform method of quantization parameter, or the like, information on an entropy coding method, or the like.

<FIG> is a flow chart schematically explaining an example of a method for predicting and coding the information on the current CU by using information on a neighboring CU in a system to which the embodiment of the present invention is applied. In the example of <FIG>, the method for predicting and coding the information on the current CU by using the information on the CU corresponding to the current CU within the reference frame will be described.

Referring to <FIG>, when the information on the current CU is coded, the coder predicts the information on the current CU through the information on the CU corresponding to the current CU within the reference frame (S810).

The coder determines whether the predicted information is the same as the information on the current CU (S820) and when the predicted information is the same as the information on the current CU, only the prediction flag is coded and transmitted (S830). In this case, the value of the prediction flag to be coded becomes a value (for example, '<NUM>') indicating that the predicted information is the same as the information on the current CU.

When the predicted information is not the same as the information on the current CU, the prediction flag (for example, the value of the prediction flag may be '<NUM>') indicating that the two information are not the same as each other is coded and transmitted (S840). As such, when the predicted information is not the same as the information on the current CU, the information on the current CU is coded and transmitted together with the prediction flag indicating the case (S850).

When the information on the current CU is not the same as the information on the CU, various methods as described below may be applied to code and transmit the information on the current CU.

In addition to the above-mentioned (<NUM>) to (<NUM>) methods, when the information on the current CU is different from the information on the predicted CU, various methods may be applied as the method for coding the information on the current CU.

The method described in <FIG> may also be applied to the decoding process, in the same method as described above.

<FIG> is a flow chart schematically explaining an example of a method for predicting and decoding the information of the current CU by using information on the neighboring CU in a system to which the embodiment of the present invention is applied. In the example of <FIG>, the method for predicting and decoding the information on the current CU by using the information on the CU corresponding to the current CU within the reference frame will be described.

Referring to <FIG>, the decoder decodes the prediction flag so as to decode the information on the current CU (S910). The prediction flag may be coded by the coder and may be transmitted as the bitstream.

The decoder determines whether the value of the prediction flag is <NUM>, that is, the prediction flag indicates that the information on the current CU is the same as the predicted information (S920). When the value of the prediction flag is <NUM>, the information on the current CU is predicted from the CU corresponding to the current CU within the reference frame (S930). The decoder generates the information on the CU predicted from the CU corresponding to the current CU within the reference frame and substitutes the information on the generated CU into the information on the current CU (S940). That is, the information on the predicted CU is used as the information on the current CU.

When the value of the prediction flag is <NUM>, the decoder decodes the information on the current CU without using the information on the neighboring CU (S950).

When the value of the prediction flag does not indicate that the information on the current CU is the same as the predicted information, the information on the current CU may be decoded by various methods as described below.

In addition to the above-mentioned (<NUM>) to (<NUM>) methods, various methods may be applied as the method for decoding the information on the current CU.

As the embodiment of the present invention described in <FIG> and <FIG>, when coding the split flat of the LCU, the method for predicting and coding the split flag regarding the current LCU through the split flag regarding the LCU within the reference frame may be considered.

Actually, comparing the CU of the reference frame with the CU of the current frame, the split flat of both CUs is very similar in most cases.

<FIG> is a diagram for explaining the case of predicting the information on the current LCU through the information on the LCU corresponding to the current LCU within the reference frame. <FIG> shows the split flat of the LCU corresponding to the current LCU within the reference frame. <FIG> shows the split flag of the LCU of the current frame. Both of the LCUs of <FIG> show the split distribution of <NUM> × <NUM> pixels, by way of example. Referring to <FIG>, it can be confirmed that the split flag for the CU of the reference frame is similar to the split flag for the CU of the current frame.

<FIG> is a diagram schematically explaining a method for transmitting the split flag. In <FIG>, when the split_flag of the split flag is <NUM>, it indicates that the corresponding block is split and when the split_flag of the split flat is <NUM>, it indicates that the corresponding block is not split.

The example of <FIG> shows the split flag regarding the LCU shown in <FIG>. Referring to <FIG>, it can be appreciated that the split flag for the CU of the current frame is transferred at each CU level, regardless of the split structure of the reference frame.

In connection with this, the split flag for the current frame can be predicted and coded by using the split structure of the reference frame in the embodiment of the present invention.

<FIG> is a diagram schematically explaining a method for predicting the split flag regarding the current LCU by using split flag regarding LCU corresponding to the current LCU in the reference frame, in the system to which the present invention is applied. The example of <FIG> shows the split flag regarding the LCU shown in <FIG>.

The split prediction information, which is the largest CU (LCU) unit at depth '<NUM>', may be used as the information indicating that the split flag of the current CU is the same as that of the CU of the reference frame. The split flag may be predicted in the depth unit.

In the example of <FIG>, since the spilt flag regarding the LCU of FIGS. 11A and 11B for the depth <NUM> is different, '<NUM>' is transmitted as the split prediction information at the depth '<NUM>'.

The split flag is predicted by increasing the depth '<NUM>'. Comparing the split distribution in a unit of the four CUs of <NUM> × <NUM> pixels having the depth '<NUM>' with the CU of the reference frame, '<NUM>' is transferred to the split prediction information when they have the same split distribution and '<NUM>' is transferred when they do not have the same split distribution. Since the CU of <NUM> × <NUM> pixels at the upper left end does not have the same split distribution, '<NUM>' is transferred to the split prediction information. Meanwhile, the CU of <NUM> × <NUM> pixels at the upper right end has the same split distribution, '<NUM>' is transferred to the split prediction information.

When the spilt prediction information is '<NUM>', the split distribution of the CU within the reference frame may be applied to the current CU and the split flag regarding the CU for a depth deeper than the current depth may not be transferred. Next, '<NUM>' is stored as the split prediction information of the CU of <NUM> × <NUM> pixels at the lower left end and '<NUM>' is stored as the split prediction information of the CU of <NUM> × <NUM> pixels at the lower left end.

The split flag may be coded by the hierarchical method performing the prediction in a smaller unit CU by increasing the depth by '<NUM>' by the above-mentioned method only when the split prediction information is <NUM>.

<FIG> is a diagram schematically showing the current CU and the neighboring CU within the same frame.

In the high efficiency video coding, when the information on the current CU is coded, the compression efficiency of the information on the CU can be improved by predicting and coding the information on the current CU through the information on the CU neighboring to the current CU within the frame as shown in <FIG> or coding the information variation on the current CU for the information on the CU neighboring to the current CU.

Here, the CU may include the CU in the smallest unit from the LCU. Further, the information on the CU may include all the information within the CU. For example, the information on the CU may include the CU, a prediction unit (PU), a transform unit (TU) split flag, information on the intra prediction or the inter prediction, mode information on the inter prediction on the merge skip, the merge, the motion vector prediction (MVP), or the like, a motion vector, a reference picture index, weighted prediction information, prediction mode information on the intra prediction, remaining mode information among the prediction mode information on the intra prediction, discrete cosine transform (DCT)/discrete sine transform (DST), information on a transform method of quantization parameter, or the like, information on an entropy coding method, or the like.

Further, the information on the CU may be coded by adaptively selecting embodiment <NUM> and embodiment <NUM> in the CU unit and the information on the CU may be coded in consideration of both of the embodiments.

<FIG> is a flow chart for schematically explaining a method for predicting and coding information on the current CU through CU neighboring to the current CU when coding the information on the current CU according to the exemplary embodiment of the present invention.

Referring to <FIG>, when the information on the current CU is coded, the coder predicts the information on the current CU through the information on the already coded CU neighboring to the current CU to generate the prediction information (S <NUM>).

The coder determines whether the information on the current CU is the same as the predicted CU information (S1420). When the information on the current CU is the same as the predicted CU information, the coder transfers the prediction flag '<NUM>' indicating that the information on the current CU is the same as the predicted CU (S1430). When the information on the current CU is not the same as the predicted CU information, the coder codes and transmits the prediction flag into the value of '<NUM>' (S1440) and at the same time, codes and transmits the information on the current CU (S1450).

Here, when the information on the current CU is not the same as the information on the predicted CU, the information on the current CU may be coded by various methods as described below.

In addition to this, when the information on the current CU is not the same as the information on the predicted CU, the information on the current CU can be coded using various methods.

The method described in <FIG> may be similarly applied even when the decoding is performed.

<FIG> is a flow chart schematically explaining another example of a method for predicting and decoding the information on the current CU by using the information on the neighboring CU in a system to which the embodiment of the present invention is applied. In the example of <FIG>, the method for predicting and decoding the information on the current CU by using the information on the CU neighboring to the current CU within the current frame will be described.

Referring to <FIG>, the decoder decodes the prediction flag so as to decode the information on the current CU (S1510). The prediction flag may be coded by the coder and may be transmitted as the bitstream.

The decoder determines whether the value of the prediction flag is <NUM>, that is, the prediction flag indicates that the information on the current CU is the same as the predicted information (S1520). When the value of the prediction flag is <NUM>, the information on the current CU is predicted from the CU neighboring to the current CU (S1530). The decoder generates the information on the CU predicted from the CU neighboring to the current CU and substitutes the information on the generated CU into the information on the current CU (S1540). That is, the information on the predicted CU is used as the information on the current CU.

When the value of the prediction flag is <NUM>, the decoder decodes the information on the current CU without using the information on the neighboring CU (S1550).

As described above, the information on the current CU that may be decoded using the information on the neighboring CU may include the CU, a prediction unit (PU), a transform unit (TU) split flag, information on the intra prediction or the inter prediction, mode information on the inter prediction on the merge skip, the merge, the motion vector prediction (MVP), or the like, a motion vector, a reference picture index, weighted prediction information, prediction mode information on the intra prediction, remaining mode information among the prediction mode information on the intra prediction, discrete cosine transform (DCT)/discrete sine transform (DST), information on a transform method of quantization parameter, or the like, information on an entropy coding method, or the like.

For example, when the current CU is the intra prediction mode, if the target information to be decoded relates to the intra prediction mode of the current CU, the prediction flag may be a flag indicating whether the current CU is coded by the intra prediction mode of the neighboring CU. Therefore, in this case, provided that the above-mentioned S1520 to <NUM> are applied, the current CU may be predicted according to the intra prediction mode of the neighboring CU when the value of the decoded prediction flag is <NUM> and the current CU may be predicted according to another intra prediction mode, not the intra prediction mode of the neighboring CU, when the value of the decoded prediction flag is <NUM>.

<FIG> is a diagram explaining one predicting and coding the information on the current CU by using the neighboring CU. <FIG> shows the split distribution of two neighboring <NUM> × <NUM> LCUs <NUM> and <NUM>. According to the embodiment of the present invention, it is possible to use the information on the LCU <NUM> when the LCU <NUM> is coded.

Since the maximum CU of the LCU <NUM> is <NUM> × <NUM> pixels and the minimum CU is <NUM> × <NUM> pixels, the current LCU <NUM> may define the maximum CU and the minimum CU may be defined, like the LCU <NUM>. For example, when the current LCU <NUM> is coded, the split flag is coded starting from the UC in a unit of <NUM> × <NUM> pixels. In this case, the LCU <NUM> is not the CU in a unit of <NUM> × <NUM> pixels, such that that the current CU is hardly likely to become a unit of <NUM> × <NUM> pixels. Therefore, the split flag regarding the current CU may not be transmitted by spatially predicting the split flag.

In the case of the high efficiency video coding, when the CU information is coded, the compression efficiency can be improved by coding the CU information by predicting the information on the CU to be currently provided through the prediction structure. Herein, the CU may include the CU in the smallest unit from the LCU and the CU information may include all the information within the CU.

<FIG> is a flow chart schematically explaining an example of a method for predicting and coding the information on the current CU from the prediction structure when coding the information on the current CU according to the embodiment of the present invention.

Referring to <FIG>, when the current CU information is coded, the coder predicts the information on the current CU through the information on the already coded CU neighboring to the current CU through the prediction structure to generate the prediction information (S <NUM>).

The coder determines whether the information on the current CU is the same as the predicted CU information (S <NUM>). When the information on the current CU is the same as the information on the predicted CU, the coder transmits the prediction flag '<NUM>' indicating that the information on the current CU is the same as the predicted CU (S1730). When the information on the current CU is not the same as the information on the predicted CU, the coder codes and transmits the prediction flag into the value of '<NUM>' (S1740) and at the same time, codes and transmits the information on the current CU (S1750).

<FIG> is a flow chart schematically explaining an example of a method for predicting and decoding the information on the current CU by using the prediction structure to which the embodiment of the present invention is applied.

Referring to <FIG>, the decoder decodes the prediction flag so as to decode the information on the current CU (S1810). The prediction flag may be coded by the coder and may be transmitted as the bitstream.

The decoder determines whether the value of the prediction flag is <NUM>, that is, the prediction flag indicates that the information on the current CU is the same as the predicted information (S1820). When the value of the prediction flag is <NUM>, the information on the current CU is predicted from the prediction structure (S1830). The decoder generates the information on the CU predicted from the prediction structure and substitutes the information on the generated CU into the information on the current CU (<NUM>). That is, the information on the predicted CU is used as the information on the current CU.

When the value of the prediction flag is <NUM>, the decoder decodes the information on the current CU without using the prediction structure (S1850).

<FIG> is a diagram explaining one predicting and coding the information on the current CU by the prediction structure in a frame unit according to the embodiment of the present invention when including a hierarchical prediction structure.

Referring to <FIG>, when B frame, that is, the number <NUM> frame T4 is predicted and coded through the number <NUM> frame T0 and the number <NUM> frame T8, the information on the CU to be currently coded may be predicted through the prediction structure in the frame unit.

When the prediction is performed through two lists by referring to the temporally previous frame from the current frame and the temporally subsequent frame, respectively, all the CUs within the number <NUM> frame T4 designates L0 as the number <NUM> frame T0 and L1 as the number <NUM> frame T8. Since this has the hierarchical prediction structure in the frame unit, when the list is <NUM>, the number <NUM> frame T0 or the number <NUM> frame T8 may be designated as the reference frame, respectively, but when the list is two, only the two reference frames are present. Therefore, the L0 designates the temporally previous frame as the reference frame and the L1 designates the temporally subsequent frame as the reference frame. In the case of the prediction structure shown in <FIG>, many CUs perform the prediction by using two lists by referring to the temporally previous frame and the temporally subsequent frame, respectively. Therefore, when the reference index designating the reference frame is stored within the CU information, the reference index for each list is not transmitted in the case in which the prediction is performed by two lists by referring to the temporally previous frame and the temporally subsequent frame, respectively, and only the information corresponding to the case in which the prediction is performed by two lists by referring to the temporally previous frame and the temporally subsequent frame, respectively, is transmitted. In other cases, the compression efficiency for coding the reference index may be improved by transmitting the reference index of the corresponding list, together with the information that does not correspond to the case in which the prediction is performed by two lists by referring to the temporally previous frame and the temporally subsequent frame, respectively.

<FIG> is a flow chart schematically explaining an example of a method for decoding reference index prediction information according to the embodiment of the present invention.

Referring to <FIG>, the decoder decodes the reference index prediction flag received from the coder (S2010). When the prediction is performed by two lists by referring to the temporally previous frame and the temporally subsequent frame, respectively, the value of the decoded reference index prediction flag represents <NUM>. In other cases, the value of the decoded reference index prediction flag represents <NUM>.

The decoder determines whether the value of the reference index prediction flag represents <NUM> (S2020) and when the value of the reference index prediction flag is <NUM>, the reference index is predicted through the prediction structure (S2030). The decoder designates the temporally previous frame and the temporally subsequent frame, respectively, as the reference index in the L0 and the L1 through the prediction structure (S2040). In addition, when the reference index prediction flag is <NUM>, the decoder decodes the reference index corresponding to the list by the existing method (S2050).

<FIG> is a diagram showing a schematic configuration of a coder for predicting and coding the information on the current CU through the information on the CU corresponding to the current CU within the reference frame.

Referring to <FIG>, a coder <NUM> includes a CU information prediction module <NUM>, a determination module <NUM>, and a CU information coding module <NUM>.

The CU information prediction module <NUM> receives the information on the CU corresponding to the current CU within the reference frame to output the predicted CU information.

The determination module <NUM> receives the information on the current CU and the CU information predicted in the CU information prediction module <NUM> to determine whether the information on the current CU is the same as the information on the predicted CU and transmits the prediction flag information according to the determination result. When the information on the current CU is the same as the information on the predicted CU, the transmitted prediction flag information is set to be '<NUM>'.

When the transmitted prediction flag information is '<NUM>', the prediction flag information is coded without separately coding the information on the current CU and is transmitted through the bitstream.

When the information on the current CU is not the same as the information on the predicted CU, the prediction flag information to be transmitted is set to be '<NUM>'.

When the prediction flag information to be transmitted is '<NUM>', the CU information coding module <NUM> may code the information on the current CU by using the CU information predicted in the CU information prediction module <NUM>. The CU information coded in the CU information coding module <NUM> is transmitted to the decoder, being included in the bitstream.

<FIG> is a diagram showing a schematic configuration of a decoder for predicting and decoding the information on the current CU through the information on the CU corresponding to the current CU within the reference frame.

Referring to <FIG>, the decoder <NUM> includes a prediction flag decoding module <NUM>, a CU information prediction module <NUM>, and a CU information decoding module <NUM>.

When the bitstream is transmitted, the prediction flag decoding module <NUM> decodes the prediction flag information.

The CU information prediction module <NUM> performs the prediction through the information on the CU corresponding to the current CU.

When the value of the decoded prediction flag information is '<NUM>', the value predicted through the information on the CU corresponding to the current CU is stored as the information on the current CU within the reference frame.

When the value of the decoded prediction flag information is '<NUM>', the CU information decoding module <NUM> decodes the information on the coded CU transmitted within the bitstream and is stored as the information on the current CU. In this case, the CU information decoding module <NUM> may decode the information on the current CU by using the CU information predicted in the CU information prediction module <NUM>.

<FIG> is a diagram showing another example of a coder for predicting and coding the information on the current CU through the information on the CU corresponding to the current CU within the reference frame. In <FIG>, the coder predicts and codes the split flag regarding the current CU through the CU corresponding to the current CU within the reference frame.

Referring to <FIG>, the coder <NUM> includes a CU split flag prediction module <NUM>, a determination module <NUM>, and a CU split flag coding module <NUM>.

The CU split flag prediction module <NUM> receives the split flag regarding the CU corresponding to the current CU within the reference frame to output the predicted CU split flag.

The determination module <NUM> receives the split flag regarding the current CU and the CU split flag predicted in the CU split flag prediction module <NUM> to determine whether the split flag regarding the current CU is the same as the predicted CU split flag and transmits the split prediction flag information according to the determination result. When the split flag regarding the current CU is the same as the predicted CU split flag, the transmitted prediction flag information is set to be '<NUM>'.

When the transmitted prediction flag information is '<NUM>', the split prediction flag information is coded without separately coding the split flag regarding the current CU and is transmitted through the bitstream.

When the split flag regarding the current CU is not the same as the predicted CU split flag, the split prediction information to be transmitted is set to be '<NUM>'.

When the split prediction flag information to be transmitted is '<NUM>', the CU split flag coding module <NUM> may code the split flag regarding the current CU by using the CU split flag predicted in the CU split information prediction module <NUM>. The CU split flag decoded in the CU split flag decoding module <NUM> is transmitted to the decoder, being included in the bitstream together with the prediction flag information.

<FIG> is a diagram showing another example of a decoder for predicting and decoding the information on the current CU through the information on the CU corresponding to the current CU within the reference frame. In <FIG>, the decoder predicts and decodes the split flag regarding the current CU through the CU corresponding to the current CU within the reference frame.

Referring to <FIG>, the decoder <NUM> includes a split prediction flag decoding module <NUM>, a CU split flag prediction module <NUM>, and a CU split flag decoding module <NUM>.

When the bitstream is transmitted, the split prediction flag decoding module <NUM> decodes the split prediction flag information.

The CU split flag prediction module <NUM> receives the split flag regarding the current CU through the information on the CU corresponding to the current CU within the reference frame.

When the value of the decoded split prediction flag information is '<NUM>', the value predicted through the information on the CU corresponding to the current CU is stored as the split flag regarding the current CU within the reference frame.

When the value of the decoded split prediction flag information is '<NUM>', the CU split flag decoding module <NUM> decodes the split flag regarding the coded CU transmitted within the bitstream and is stored as the split flag regarding the current CU. In this case, the CU split flag decoding module <NUM> may decode the split flag regarding the current CU by using the CU split flag predicted in the CU split flag prediction module <NUM>.

<FIG> is a diagram schematically showing a configuration of the coder for predicting and coding the information on the current CU by using the information on the neighboring CU within the same frame.

The CU information prediction module <NUM> receives the information on the CU neighboring to the current CU to output the predicted CU information.

When the transmitted predict flag information is '<NUM>', the prediction flag information is coded without separately coding the information on the current CU and is transmitted through the bitstream.

When the prediction flag information to be transmitted is '<NUM>', the CU information coding module <NUM> may code the information on the current CU by using the CU information predicted in the CU information prediction module <NUM>. The CU information coded in the CU information coding module <NUM> is transmitted to the decoder, being included in the bitstream together with the prediction flag information.

<FIG> is a diagram schematically showing a configuration of the decoder for predicting and decoding the information on the current CU by using the information on the neighboring CU within the same frame.

Referring to <FIG>, a decoder <NUM> includes a prediction flag decoding module <NUM>, a CU information prediction module <NUM>, and a CU information decoding module <NUM>.

The CU information prediction module <NUM> predicts the information on the current CU through the information on the CU neighboring to the current CU.

When the value of the decoded prediction flag information is '<NUM>', the value predicted through the information on the CU neighboring to the current CU is stored as the information on the current CU.

<FIG> is a diagram schematically showing a configuration of the coder for predicting and decoding the information on the current CU through the prediction structure.

The CU information prediction module <NUM> receives the prediction structure to output the predicted CU information. The input prediction structure is as described in <FIG> and <FIG>.

The CU information prediction module <NUM> predicts the information on the current CU through the prediction structure. Here, the prediction structure used for the prediction is as described in <FIG> and <FIG>.

When the value of the decoded prediction flag information is '<NUM>', the information on the CU predicted through the prediction structure is stored as the information on the current CU.

In the above-mentioned exemplary system, although the methods have described based on a flow chart as a series of steps or blocks, the present invention is not limited to a sequence of steps but any step may be generated in a different sequence or simultaneously from or with other steps as described above.

Claim 1:
A method for decoding video information, the method comprising:
decoding a prediction flag indicating whether information of a current block is the same as prediction information derived from information of a neighboring block reconstructed earlier than the current block, the neighboring block is one of spatial neighboring blocks and a collocated block, the spatial neighboring blocks belong to a current frame to which the current block belongs, and the collocated block belongs to a reference frame having a different temporal order from the current frame;
deriving the information of the current block based on the decoded prediction flag; and
performing inter-prediction on the current block based on the derived information of the current block,
wherein the information of the current block includes information on a motion vector of the current block and information on a prediction direction of the current block,
wherein the prediction information includes prediction information on a motion vector and prediction information on a prediction direction,
wherein, when the prediction flag indicates the information of the current block is the same as the prediction information, the prediction information is used as the information of the current block,
wherein, when the prediction flag indicates the information of the current block is not the same as the prediction information, the information of the current block is derived by adding a difference value obtained from a bitstream to the prediction information,
wherein the inter-prediction is performed using one or more reference frames reconstructed earlier than the current frame, each of the reference frames has a different temporal order from the current frame and is identified by a reference index, and
wherein, when the number of the reference frames is <NUM> and the number of reference frame lists constructed from the reference frames is <NUM>, the reference index is determined as a specific value indicating each of the reference frames.