WO2012173315A1 - 인트라 예측 모드 부호화/복호화 방법 및 장치 - Google Patents
인트라 예측 모드 부호화/복호화 방법 및 장치 Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/46—Embedding additional information in the video signal during the compression process
- H04N19/463—Embedding additional information in the video signal during the compression process by compressing encoding parameters before transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
- H04N19/593—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial prediction techniques
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
- H04N19/103—Selection of coding mode or of prediction mode
- H04N19/11—Selection of coding mode or of prediction mode among a plurality of spatial predictive coding modes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
- H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
- H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
Definitions
- the present invention relates to image processing, and more particularly, to an intra prediction mode encoding / decoding method and apparatus.
- the demand for high resolution and high quality images such as high definition (HD) images and ultra high definition (UHD) images is increasing in various fields.
- the higher the resolution and the higher quality of the image data the more information or bit rate is transmitted than the existing image data. Therefore, the image data can be transmitted by using a medium such as a conventional wired / wireless broadband line or by using a conventional storage medium.
- the transmission cost and the storage cost are increased. High efficiency image compression techniques can be used to solve these problems.
- Image compression technology includes an inter prediction technique for predicting pixel values included in a current picture from before and / or after a current picture, and for predicting pixel values included in a current picture by using pixel information in the current picture.
- An object of the present invention is to provide an image encoding method and apparatus capable of improving image encoding / decoding efficiency.
- Another object of the present invention is to provide an image decoding method and apparatus capable of improving image encoding / decoding efficiency.
- Another object of the present invention is to provide an intra prediction mode encoding method and apparatus capable of improving image encoding / decoding efficiency.
- Another technical problem of the present invention is to provide an intra prediction mode decoding method and apparatus for improving image encoding / decoding efficiency.
- One embodiment of the present invention is an image decoding method for performing prediction on a current block in an intra mode.
- the method may include generating a current table index using a code number and MPM index information and applying an index mapping table to the current table index to derive a current prediction mode.
- the MPM index information includes the number of MPM candidates and a value of the index of the MPM candidate, wherein the index of the MPM candidate is an index assigned to the MPM candidate in the index mapping table.
- the current prediction mode is an intra prediction mode of a current prediction unit, and the current table index is an index assigned to the current prediction mode in the index mapping table.
- the method may further comprise converting the codeword received from the encoder to the code number using an inverse VLC table.
- the number of entries in the index mapping table may be equal to the number of intra prediction modes that the current prediction unit may have.
- the index value of the MPM candidate may be derived by applying an inverse index mapping table to the mode value of the MPM candidate.
- the number of MPM candidates may be a predetermined fixed value.
- the predetermined fixed value may be 2, 3 or 4.
- the method may further comprise updating the index mapping table based on the frequency of occurrence of the current table index.
- the index mapping table may be updated for a prediction unit in which one of the MPM candidates is selected as an intra prediction mode.
- the device generates a current table index by using a code number and MPM index information, and derives a current prediction mode by applying an index mapping table to the current table index.
- An entropy decoder and a predictor configured to perform intra prediction on the current block using the derived current prediction mode, wherein the MPM index information includes the number of MPM candidates and the value of the index of the MPM candidates.
- the index of the MPM candidate is an index assigned to the MPM candidate in the index mapping table
- the current prediction mode is an intra prediction mode of the current prediction unit
- the current table index is the current prediction in the index mapping table. The index assigned to the mode.
- the method may include generating a current table index using a code number and MPM index information and applying an index mapping table to the current table index to derive a current prediction mode.
- the MPM index information includes the number of MPM candidates and a value of the index of the MPM candidate, wherein the index of the MPM candidate is an index assigned to the MPM candidate in the index mapping table.
- the current prediction mode is an intra prediction mode of a current prediction unit, and the current table index is an index assigned to the current prediction mode in the index mapping table.
- the method may further comprise converting the codeword received from the encoder to the code number using an inverse VLC table.
- the number of entries in the index mapping table may be equal to the number of intra prediction modes that the current prediction unit may have.
- the index value of the MPM candidate may be derived by applying an inverse index mapping table to the mode value of the MPM candidate.
- the number of MPM candidates may be a predetermined fixed value.
- the predetermined fixed value may be 2, 3 or 4.
- the method may further comprise updating the index mapping table based on the frequency of occurrence of the current table index.
- the index mapping table may be updated for a prediction unit in which one of the MPM candidates is selected as an intra prediction mode.
- image encoding / decoding efficiency can be improved.
- image decoding method and apparatus According to the image decoding method and apparatus according to the present invention, image encoding / decoding efficiency can be improved.
- image encoding / decoding efficiency may be improved.
- image encoding / decoding efficiency can be improved.
- FIG. 1 is a block diagram schematically illustrating an image encoding apparatus according to an embodiment of the present invention.
- FIG. 2 is a conceptual diagram schematically illustrating a prediction unit according to an embodiment of the present invention.
- FIG. 3 is a block diagram schematically illustrating an image decoding apparatus according to an embodiment of the present invention.
- FIG. 4 is a conceptual diagram schematically illustrating a prediction unit of an image decoding apparatus according to an embodiment of the present invention.
- FIG. 5 is a conceptual diagram schematically showing an embodiment of an MPM derivation method.
- FIG. 6 is a conceptual diagram schematically illustrating an embodiment of a remaining mode used for transmission of intra prediction mode information.
- FIG. 7 is a conceptual diagram schematically illustrating a configuration of an index mapping table used for entropy decoding.
- FIG. 8 is a conceptual diagram illustrating an embodiment of an intra prediction mode encoding method using MPM.
- FIG. 9 is a conceptual diagram illustrating an embodiment of an intra prediction mode decoding method using MPM.
- FIG. 10 is a conceptual diagram illustrating another embodiment of an intra prediction mode encoding method using MPM.
- 11 is a flowchart illustrating an embodiment of a method of converting a current table index into a code number.
- FIG. 12 is a conceptual diagram illustrating another embodiment of an intra prediction mode decoding method using MPM.
- FIG. 13 is a flow diagram illustrating one embodiment of a method for converting a code number into a current table index.
- FIG. 14 is a flowchart schematically illustrating an intra prediction mode encoding method according to an embodiment of the present invention.
- 15 is a flowchart schematically illustrating an intra prediction mode decoding method according to an embodiment of the present invention.
- each of the components in the drawings described in the present invention are shown independently for the convenience of the description of the different characteristic functions in the image encoding / decoding apparatus, each component is implemented by separate hardware or separate software It does not mean to be.
- two or more of each configuration may be combined to form one configuration, or one configuration may be divided into a plurality of configurations.
- Embodiments in which each configuration is integrated and / or separated are also included in the scope of the present invention without departing from the spirit of the present invention.
- the components may not be essential components for performing essential functions in the present invention, but may be optional components for improving performance.
- the present invention can be implemented including only the components essential for implementing the essentials of the present invention except for the components used for improving performance, and the structure including only the essential components except for the optional components used for improving performance. Also included within the scope of the present invention.
- the image encoding apparatus 100 may include a picture splitter 105, a predictor 110, a transformer 115, a quantizer 120, a realigner 125, and an entropy encoder 130. , An inverse quantization unit 135, an inverse transform unit 140, a filter unit 145, and a memory 150.
- the picture dividing unit 105 may divide the input picture into at least one processing unit.
- the processing unit may be a prediction unit (PU), a transform unit (TU), or a coding unit (CU).
- the predictor 110 may include an inter predictor that performs inter prediction and an intra predictor that performs intra prediction.
- the prediction unit 110 may generate a prediction block by performing prediction on the processing unit of the picture in the picture division unit 105.
- the processing unit of the picture in the prediction unit 110 may be a coding unit, a transformation unit, or a prediction unit.
- the processing unit in which the prediction is performed may differ from the processing unit in which the prediction method and the details are determined.
- the method of prediction and the prediction mode are determined in units of prediction units, and the performance of prediction may be performed in units of transform units.
- the residual value (residual block) between the generated prediction block and the original block may be input to the converter 115.
- prediction mode information and motion vector information used for prediction may be encoded by the entropy encoder 130 together with the residual value and transmitted to the decoder.
- the transformer 115 performs a transform on the residual block in transform units and generates transform coefficients.
- the transform unit in the transform unit 115 may be a transform unit and may have a quad tree structure. In this case, the size of the transform unit may be determined within a range of a predetermined maximum and minimum size.
- the transform unit 115 may transform the residual block using a discrete cosine transform (DCT) and / or a discrete sine transform (DST).
- DCT discrete cosine transform
- DST discrete sine transform
- the quantization unit 120 may generate quantization coefficients by quantizing the residual values transformed by the transformation unit 115.
- the value calculated by the quantization unit 120 may be provided to the inverse quantization unit 135 and the reordering unit 125.
- the reordering unit 125 rearranges the quantization coefficients provided from the quantization unit 120. By rearranging the quantization coefficients, the efficiency of encoding in the entropy encoder 130 may be increased.
- the reordering unit 125 may rearrange the quantization coefficients in the form of a two-dimensional block into a one-dimensional vector form through a coefficient scanning method.
- the reordering unit 125 may increase the entropy coding efficiency of the entropy encoder 130 by changing the order of coefficient scanning based on probabilistic statistics of coefficients transmitted from the quantization unit.
- the entropy encoder 130 may perform entropy encoding on the quantized coefficients rearranged by the reordering unit 125.
- the entropy encoder 130 may include quantization coefficient information, block type information, prediction mode information, division unit information, prediction unit information, transmission unit information, and motion vector of the coding unit received from the reordering unit 125 and the prediction unit 110.
- Various information such as information, reference picture information, interpolation information of a block, and filtering information can be encoded.
- Entropy encoding may use encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC).
- the entropy encoder 130 may store a table for performing entropy coding, such as a variable length coding (VLC) table, and the entropy encoder 130. ) May perform entropy encoding using the stored VLC table.
- VLC variable length coding
- the entropy encoder 130 converts a symbol into a bin and binarizes the symbol, and then performs an arithmetic encoding on the bin according to the occurrence probability of the bin to generate a bitstream. You can also create
- a low value index and a corresponding short codeword are assigned to a symbol having a high probability of occurrence, and a high value index is assigned to a symbol having a low probability of occurrence.
- Corresponding long codewords may be assigned. Accordingly, the bit amount of the symbols to be encoded may be reduced, and image compression performance may be improved by entropy encoding.
- the inverse quantization unit 135 may inverse quantize the quantized values in the quantization unit 120, and the inverse transformer 140 may inversely transform the inverse quantized values in the inverse quantization unit 135.
- the residual value generated by the inverse quantization unit 135 and the inverse transformer 140 may be combined with the prediction block predicted by the prediction unit 110 to generate a reconstructed block.
- the filter unit 145 may apply a deblocking filter and / or an adaptive loop filter (ALF) to the reconstructed picture.
- ALF adaptive loop filter
- the deblocking filter may remove block distortion generated at the boundary between blocks in the reconstructed picture.
- the adaptive loop filter may perform filtering based on a value obtained by comparing a reconstructed image with an original image after the block is filtered through a deblocking filter. ALF may be performed only when high efficiency is applied.
- the filter unit 145 may not apply filtering to the reconstructed block used for inter prediction.
- the memory 150 may store the reconstructed block or the picture calculated by the filter unit 145.
- the reconstructed block or picture stored in the memory 150 may be provided to the predictor 110 that performs inter prediction.
- a coding unit is a unit in which coding / decoding of a picture is performed and may be divided with a depth based on a quad tree structure.
- the coding unit may have various sizes, such as 64x64, 32x32, 16x16, and 8x8.
- the encoder may transmit information about a largest coding unit (LCU) and a minimum coding unit (SCU) to the decoder.
- Information (depth information) regarding the number of splittable times together with information about the maximum coding unit and / or the minimum coding unit may be transmitted to the decoder.
- Information on whether the coding unit is split based on the quad tree structure may be transmitted from the encoder to the decoder through flag information such as a split flag.
- One coding unit may be divided into a plurality of prediction units.
- a prediction mode may be determined in units of prediction units, and prediction may be performed in units of prediction units.
- a prediction mode may be determined in units of prediction units, and intra prediction may be performed in units of transform units.
- the predictor 200 may include an inter predictor 210 and an intra predictor 220.
- the inter prediction unit 210 may generate a prediction block by performing prediction based on information of at least one picture of a previous picture or a subsequent picture of the current picture.
- the intra predictor 220 may generate a prediction block by performing prediction based on pixel information in the current picture.
- the inter prediction unit 210 may select a reference picture with respect to the prediction unit and select a reference block having the same size as the prediction unit in integer pixel sample units. Subsequently, the inter prediction unit 210 is most similar to the current prediction unit in sub-integer sample units such as 1/2 pixel sample unit and 1/4 pixel sample unit, so that the residual signal is minimized and the size of the motion vector to be encoded is also minimized. Can generate a predictive block.
- the motion vector may be expressed in units of integer pixels or less, for example, in units of 1/4 pixels for luma pixels and in units of 1/8 pixels for chroma pixels.
- Information about the index and the motion vector of the reference picture selected by the inter prediction unit 210 may be encoded and transmitted to the decoder.
- the image decoder 300 includes an entropy decoder 310, a reordering unit 315, an inverse quantizer 320, an inverse transformer 325, a predictor 330, and a filter 335. And a memory 340.
- the input bit stream may be decoded according to a procedure in which image information is processed by the image encoder.
- the entropy decoding unit 310 may perform entropy decoding on the input bitstream, and the entropy decoding method is similar to the entropy encoding method described above.
- VLC variable length coding
- the entropy decoder 310 may also be identical to the VLC table used in the encoder. Entropy decoding can be performed by implementing a VLC table. Even when CABAC is used to perform entropy encoding in the image encoder, the entropy decoder 310 may perform entropy decoding using CABAC correspondingly.
- a low value index and a corresponding short codeword are assigned to a symbol having a high probability of occurrence, and a high value index is assigned to a symbol having a low probability of occurrence.
- Corresponding long codewords may be assigned. Accordingly, the bit amount of the symbols to be encoded may be reduced, and image compression performance may be improved by entropy encoding.
- Information for generating a prediction block among the information decoded by the entropy decoder 310 may be provided to the predictor 330, and a residual value of which entropy decoding is performed by the entropy decoder may be input to the reordering unit 315.
- the reordering unit 315 may reorder the bit stream deentropy decoded by the entropy decoding unit 310 based on a method of reordering the image encoder.
- the reordering unit 315 may reorder the coefficients expressed in the form of a one-dimensional vector by restoring the coefficients in the form of a two-dimensional block.
- the reordering unit 315 may be realigned by receiving information related to coefficient scanning performed by the encoder and performing reverse scanning based on the scanning order performed by the corresponding encoder.
- the inverse quantization unit 320 may perform inverse quantization based on the quantization parameter provided by the encoder and the coefficient values of the rearranged block.
- the inverse transform unit 325 may perform inverse DCT and / or inverse DST on DCT and DST performed by the transform unit of the encoder with respect to the quantization result performed by the image encoder.
- the inverse transform may be performed based on a transmission unit determined by the encoder or a division unit of an image.
- the DCT and / or DST may be selectively performed according to a plurality of pieces of information, such as a prediction method, a size and a prediction direction of the current block, and the inverse transformer 325 of the decoder is performed by the transformer of the encoder.
- Inverse transformation may be performed based on the transformation information.
- the prediction unit 330 may generate the prediction block based on the prediction block generation related information provided by the entropy decoding unit 310 and the previously decoded block and / or picture information provided by the memory 340.
- the reconstruction block may be generated using the prediction block generated by the predictor 330 and the residual block provided by the inverse transform unit 325.
- the reconstructed block and / or picture may be provided to the filter unit 335.
- the filter unit 335 may apply deblocking filtering, sample adaptive offset (SAO), and / or adaptive loop filtering (ALF) to the reconstructed block and / or picture.
- deblocking filtering sample adaptive offset (SAO)
- ALF adaptive loop filtering
- the memory 340 may store the reconstructed picture or block to use as a reference picture or reference block, and may provide the reconstructed picture to the output unit.
- FIG. 4 is a conceptual diagram schematically illustrating a prediction unit of an image decoding apparatus according to an embodiment of the present invention.
- the predictor 400 may include an intra predictor 410 and an inter predictor 420.
- the intra prediction unit 410 may generate a prediction block based on pixel information in the current picture when the prediction mode for the corresponding prediction unit is an intra prediction mode (intra prediction mode).
- the inter prediction unit 420 may include information necessary for inter prediction of the current prediction unit provided by the image encoder, eg, a motion vector, Inter-prediction of the current prediction unit may be performed based on information included in at least one of a previous picture or a subsequent picture of the current picture including the current prediction unit by using information about the reference picture index.
- the motion information may be derived in response to the skip flag, the merge flag, and the like of the coding unit received from the encoder.
- a "picture” or a “picture” can represent the same meaning as a “picture” according to the configuration or expression of the invention, the “picture” may be described as a “picture” or a “picture”.
- inter prediction and inter prediction have the same meaning
- intra prediction and intra prediction have the same meaning.
- the intra predictor may generate a prediction block for the current block by performing prediction based on pixel information in the current picture.
- the intra prediction mode there may be a vertical, horizontal, DC, angular mode, etc. according to the position and prediction method of reference pixels used for pixel value prediction of the current block.
- the prediction In the vertical mode, the prediction may be performed in the vertical direction using the pixel values of the adjacent blocks, and in the horizontal mode, the prediction may be performed in the horizontal direction using the pixel values of the adjacent blocks.
- the prediction block In the DC mode, the prediction block may be generated by an average of pixel values in the current block.
- the angular mode prediction may be performed according to a predetermined angle and / or direction for each mode.
- the intra prediction mode information may be transmitted as a value indicating the prediction mode itself, a method of transmitting the intra prediction mode information using the mode value predicted for the intra prediction mode may be provided to increase the transmission efficiency.
- MPM Most Probable Mode
- the current prediction unit means a unit on which the current prediction is performed.
- A is a neighboring prediction unit adjacent to the top of the current prediction unit and B is a neighboring prediction unit adjacent to the left of the current prediction unit.
- the prediction unit A, the prediction unit B, and the current prediction unit may be the same size as shown in the embodiment of FIG. 5, but may have different sizes.
- the encoder and the decoder may construct the MPM candidate list using the prediction mode (mode A) of the prediction unit A and the prediction mode (mode B) of the prediction unit B.
- mode A and mode B are the same, the number of MPM candidates may be one, and when the mode A and mode B are different, the number of MPM candidates may be two.
- the number of MPM candidates is not limited to one or two as in the embodiment of FIG. 5, and may be three or more.
- the encoder and decoder may use a fixed number of MPM candidates.
- the number of entries of the MPM candidate list that is, the number of MPM candidates in the MPM candidate list may always be a fixed value.
- the number of fixed MPM candidates may be two, and may be three or four or more.
- the remaining MPM candidates may be one.
- the DC mode, the planar mode, or other predetermined prediction mode may be filled.
- the intra prediction mode of the current prediction unit may be the same prediction mode as any one of the MPM candidates.
- Information on whether any of the MPM candidates have the same prediction mode as the current prediction unit may be transmitted from the encoder to the decoder through a predetermined flag.
- the flag may be prev_intra_luma_pred_flag, and when the flag is 1, there may be a candidate having the same prediction mode as the current prediction unit among MPM candidates.
- the encoder may not transmit additional additional information to the decoder.
- the decoder cannot know which prediction mode of the MPM candidates is the same as the prediction mode of the MPM candidates. Therefore, at this time, the encoder may transmit an index indicating to the decoder the prediction mode of the current prediction unit is the same as the prediction mode of which MPM candidate.
- the decoder may determine the prediction mode of the current prediction unit using the index. For example, the index may be mpm_idx.
- Intra prediction mode information of the current unit may be transmitted to the decoder using a remaining mode.
- the encoder and the decoder may use not only MPM but also Most Probable Remaining Mode (MPRM) in performing intra prediction mode encoding / decoding.
- MPRM Most Probable Remaining Mode
- the encoder and the decoder may generate an MPRM list including the MPRM candidates using intra prediction modes except the MPM candidates.
- the coder may provide information on whether or not the MPRM candidates have the same prediction mode as the current prediction unit through a predetermined flag. Can be sent to the decoder.
- the flag may be mprm_pred_flag.
- the encoder may transmit an index to the decoder indicating the prediction mode of which MPRM candidate the prediction mode of the current prediction unit is the same.
- the index may be mprm_idx.
- the encoder may transmit the intra prediction mode information of the current unit to the decoder using a remaining mode.
- Embodiments described below may be applied not only when the MPM is used but also when the MPM and the MPRM are used together.
- FIG. 6 is a conceptual diagram schematically illustrating an embodiment of a remaining mode used for transmission of intra prediction mode information.
- the prediction mode of the MPM is 1 and the number of MPM candidates is one.
- the prediction mode of the current prediction unit is referred to as the current prediction mode
- the mode value of the current prediction mode is referred to as a current mode value.
- the encoder may transmit information on the current prediction mode among the prediction modes except for the MPM candidates to the decoder. At this time, the encoder transmits prediction mode information using the current mode value if the mode values of all the MPM candidates are larger than the current mode value, and if the MPM candidate having a mode value smaller than the current mode value exists, the encoder is smaller than the current mode value.
- the prediction mode information may be transmitted using a value obtained by subtracting the number of MPMs having the mode value from the current mode value. In this case, the prediction mode in which the number of MPMs having a mode value smaller than the current mode value is subtracted from the current mode value may be called a remaining mode.
- 610 of FIG. 6 indicates an intra prediction mode that a current prediction unit may have. Since the prediction mode value of the MPM is 1, the prediction mode that the current prediction unit may have may be one of the remaining prediction modes except for the prediction mode having the mode value of 1, as in 620 of FIG. 6. At this time, for example, when the current mode value is 2, the mode value of the current remaining mode may be 1 as in 630 of FIG. In addition, when the current mode value is 0, the mode value of the current remaining mode may be 0.
- the decoder may recognize that there is no candidate having the same prediction mode as the current prediction unit among MPM candidates through flag information such as prev_intra_luma_pred_flag and the like.
- the decoder may obtain the actual prediction mode value of the current prediction unit by using the remaining mode and the MPM.
- the mode values of the MPMs are mode1, mode2,... , modeN is assumed.
- modeX it is assumed that the smaller the X value, the smaller mode value is assigned.
- X is from 1 to N-1, if the mode value of the remaining mode is greater than or equal to modeX-(X-1) and less than mode (X + 1) -X, then X is added to the mode value of the remaining mode.
- the value may be the current prediction mode.
- the mode value of the remaining mode is greater than or equal to modeN-(N-1)
- the value of N added to the mode value of the remaining mode may be the current prediction mode.
- the mode value of the remaining mode received by the decoder may be 1. Since the mode value of the MPM is 1 and the number of MPM candidates is 1, the decoder can obtain the current mode value 2 by adding 1 to the mode value of the remaining mode.
- FIG. 7 is a conceptual diagram schematically illustrating a configuration of an index mapping table used for entropy decoding.
- Entropy encoding and decoding may be used for encoding and decoding information requiring high coding efficiency, such as DCT coefficients, motion vectors, and prediction modes. Symbols input during entropy encoding and decoding may be converted into consecutive codewords, and the length of the codeword may be variable.
- LCEC Low Complexity Entropy Coding
- CABAC Context-Adaptive Binary Arithmetic Coding
- a short codeword may be allocated to a symbol having a high occurrence probability, and a long codeword may be allocated to a symbol having a low occurrence probability. Accordingly, the bit amount of the symbols to be encoded and decoded may be reduced, and image compression performance may be improved by entropy encoding and decoding.
- a predetermined VLC table may be used, and the VLC table may be configured based on the occurrence probability of each symbol.
- the entropy decoding process is schematically described from the decoder's point of view.
- the decoder may obtain a code number from the codeword in the input bit stream using the corresponding VLC table.
- the code number may also be called a codeword index.
- the decoder may obtain a value of a syntax element by using a code number and an index mapping table corresponding thereto.
- the index mapping table may also be called a sorting table.
- the index mapping table may be used to adaptively adjust the value of a syntax element assigned to each code number according to the frequency of occurrence. In an embodiment, when the currently input code number is A and A is greater than 0, the probability of occurrence of a symbol corresponding to code number A increases, so that the value of the syntax element corresponding to code number A and the code number A-1 The values of the syntax elements corresponding to may be swapped with each other. That is, the index mapping table may be updated according to the currently input code number.
- FIG. 7 illustrates an embodiment of an index mapping table indicating a mapping relationship between code numbers and corresponding intra prediction modes.
- the maximum value of the code number may be predetermined to a predetermined value.
- the encoder may store an inverse index mapping table corresponding to the index mapping table.
- the intra prediction mode of the current prediction unit may be zero.
- the prediction mode 0 assigned to the code number 3 and the prediction mode 9 assigned to the code number 2 may be swapped with each other.
- prediction mode 9 may be mapped to code number 3 and prediction mode 0 may be mapped to code number 2.
- FIG. 8 is a conceptual diagram illustrating an embodiment of an intra prediction mode encoding method using MPM.
- FIG. 8 illustrates an embodiment in which no candidate having the same prediction mode as the current prediction unit is present among the MPM candidates, for example, when prev_intra_luma_pred_flag is zero.
- the encoder may derive a remaining mode corresponding to the current prediction mode from the current prediction mode information and the prediction mode information of the MPM candidate.
- the current prediction mode information may include a mode value of the current prediction mode
- the prediction mode information of the MPM candidate may include the number of MPM candidates and a mode value of each MPM candidate.
- the remaining mode corresponding to the current prediction mode is called a current remaining mode.
- the current remaining mode may be two. Since the mode value of the MPM candidate is smaller than the mode value of the current prediction mode, the current remaining mode may be a value obtained by subtracting 1 from the mode value of the current prediction mode. As another example, if the number of MPM candidates is 2, the mode values of the MPM candidates are 1 and 2, and the current prediction mode is 3, the current remaining mode may be 1. Since the mode values of the two MPM candidates are smaller than the mode value of the current prediction mode, the current remaining mode may be a value obtained by subtracting 2 from the mode value of the current prediction mode.
- the encoder may generate a code number using a current remaining mode and an inverse index mapping table corresponding to the current remaining mode.
- the code number may also be referred to as a codeword index and may indicate a ranking of a current remaining mode in the inverse index mapping table. Therefore, the code number in this case can also be called a table index.
- the number of prediction modes that the current prediction unit may have may vary depending on the size of the current prediction unit.
- the number of remaining modes that the current prediction unit can have varies according to the number of MPM candidates. Since the number of entries in the inverse index mapping table is the same as the number of remaining modes that the current prediction unit can have, the inverse index mapping table used may also change when the number of remaining modes that the current prediction unit can have varies. have. Therefore, in the above-described embodiment, the encoder may store a plurality of inverse index mapping tables. The encoder may select and use one inverse index mapping table among the predetermined plurality of inverse index mapping tables from information on the size of the current prediction unit and the number of MPM candidates.
- the encoder may convert the code number into a codeword using the VLC table, and the codeword may be transmitted to the decoder.
- FIG. 9 is a conceptual diagram illustrating an embodiment of an intra prediction mode decoding method using MPM.
- FIG. 9 illustrates an embodiment in which no candidate having the same prediction mode as the current prediction unit exists among the MPM candidates, for example, when prev_intra_luma_pred_flag is zero. In this case, the remaining mode for the current prediction unit may be parsed.
- the decoder may convert a codeword received from an encoder into a code number using an inverse VLC table.
- the code number may also be referred to as a codeword index and may indicate a ranking of a current remaining mode in an index mapping table used for decoding. Therefore, the code number in this case can also be called a table index.
- the decoder may generate a remaining mode by using an index mapping table corresponding to the code number and the current code number.
- the decoder may store a plurality of index mapping tables.
- the decoder may select and use one index mapping table among the predetermined plurality of index mapping tables from information on the size of the current prediction unit and the number of MPM candidates.
- the number of entries in the index mapping table may be equal to the number of remaining modes that the current prediction unit may have.
- the decoder may derive the current prediction mode from the current remaining mode information and the prediction mode information of the MPM candidate.
- the current remaining mode information may include a mode value of the current remaining mode
- the prediction mode information of the MPM candidate may include the number of MPM candidates and a mode value of each MPM candidate.
- the current prediction mode may be three. Since the mode value of the MPM candidate is the same as the mode value of the current remaining mode, the current prediction mode may be 1 plus the mode value of the current remaining mode.
- the mode values of the MPM candidates are 1 and 2, and the current remaining mode is 1, the mode value of the current remaining mode is 2 to 1, which is the larger of the mode values of the MPM candidates. (Number of MPM candidates-1) is equal to the subtracted value. Therefore, the decoder can obtain the mode value 3 of the current prediction mode by adding 2 (the number of MPM candidates) to the mode value of the current remaining mode.
- mapping table the inverse index mapping table and the index mapping table are collectively called a mapping table.
- the inverse index mapping table may be directly applied to the remaining mode.
- the direct remaining mode may be generated when the index mapping table is applied to the code number. Therefore, the number of entries in the mapping table is equal to the number of remaining modes that the current prediction unit may have. Since the number of remaining modes may vary depending on the number of MPM candidates, in the above-described embodiment of FIG. 8, the encoder may have a disadvantage of using different inverse index mapping tables according to the number of MPM candidates. In the embodiment of FIG. 9, the decoder may have a disadvantage that different index mapping tables are used according to the number of MPM candidates. However, when a fixed number of MPM candidates are always used, the above-described problem may not occur.
- the remaining mode may not be transmitted when there is a candidate having the same prediction mode as the current prediction unit among the MPM candidates.
- the mapping table since the mapping table may not be updated, the distribution of the intra prediction mode may not be sufficiently reflected in the mapping table.
- the mapping table is updated according to the current remaining mode, not the actual prediction mode of the current prediction unit. Therefore, since the mapping table reflects the distribution of the remaining mode instead of the actual intra prediction mode, the characteristics of the current contents may not be directly reflected in the mapping table.
- an intra prediction mode encoding / decoding method may be provided to more directly reflect the actual prediction mode of the current prediction unit and the characteristics of the content.
- FIG. 10 is a conceptual diagram illustrating another embodiment of an intra prediction mode encoding method using MPM.
- FIG. 10 illustrates an embodiment in which no candidate having the same prediction mode as the current prediction unit exists among the MPM candidates, for example, when prev_intra_luma_pred_flag is zero.
- the encoder may generate a table index for the current prediction mode by applying an inverse index mapping table directly to the prediction mode of the current prediction unit.
- the table index in this case may indicate the ranking of the current prediction mode in the inverse index mapping table.
- the number of entries in the inverse index mapping table may be equal to the number of prediction modes that the current prediction unit may have, not the number of remaining modes.
- the table index for the current prediction mode is called a current table index.
- the current table index may mean an index assigned to the current prediction mode in the inverse index mapping table.
- the index of the MPM candidate means an index assigned to the MPM candidate in the inverse index mapping table, and may also be referred to as an MPM index.
- the encoder may derive the code number from the current table index information and the index information of the MPM candidate.
- the current table index information may include a value of a current table index
- the index information of an MPM candidate may include a number of MPM candidates and an index value of an MPM candidate.
- the code number may also be called a codeword index. Details of the conversion process from the current table index to the code number will be described later.
- the encoder may convert the code number into a codeword using the VLC table, and the codeword may be transmitted to the decoder.
- FIG. 11 is a flowchart illustrating an embodiment of a method of converting a current table index into a code number. In the embodiment of FIG. 11, it is assumed that the maximum number of MPM candidates is two.
- the encoder may determine whether the number of MPM candidates is one (S1110).
- the encoder may determine whether the table index of the current prediction mode is smaller than the index of the MPM candidates (S1120). If the current table index is smaller than the index of the MPM candidate, the code number may have the same value as the current table index (S1130). If the current table index is not smaller than the index of the MPM candidate, the code number may have a value obtained by subtracting 1 from the value of the current table index (S1140).
- the encoder may determine whether the table index of the current prediction mode is smaller than the smaller of the indexes of the MPM candidates (S1150). If the current table index is smaller than the smaller of the MPM candidate indexes, the code number may have the same value as the current table index (S1160).
- the encoder may determine whether the table index of the current prediction mode is smaller than the larger of the indexes of the MPM candidate (S1170). If the current table index is smaller than the larger of the MPM candidates, the code number may have a value of 1 subtracted from the value of the current table index (S1180). If the current table index is not smaller than the larger of the MPM candidates, the code number may have a value of 2 subtracted from the value of the current table index (S1190).
- the code number may be 2. Since the index value of the MPM candidate is smaller than the value of the current table index, the code number may be 1 minus the current table index value. As another example, if the number of MPM candidates is 2, the index values of the MPM candidates are 1 and 2, and the current table index value is 3, the code number may be 1. Since the index values of the two MPM candidates are both smaller than the value of the current table index, the code number may be 2 minus the current table index value.
- the conversion process from the current table index to the code number described above is similar to the conversion process from the current prediction mode to the remaining mode in the embodiment of FIG. 8.
- 12 is a conceptual diagram illustrating another embodiment of an intra prediction mode decoding method using MPM. 12 illustrates an embodiment in which no candidate having the same prediction mode as the current prediction unit is present among the MPM candidates, for example, when prev_intra_luma_pred_flag is zero.
- a decoder may convert a codeword received from an encoder into a code number using an inverse VLC table.
- the code number may also be called a codeword index.
- the decoder may generate a current table index from the code number and the index information of the MPM candidate.
- the index information of the MPM candidate may include the number of MPM candidates and the value of the index of the MPM candidate.
- the index of the MPM candidate means an index assigned to the MPM candidate in the index mapping table used for decoding.
- the current table index may indicate a ranking of the current prediction mode in the index mapping table used for decoding.
- the current table index may mean an index assigned to the current prediction mode in the index mapping table.
- the current prediction mode may be output. Details of the conversion process from the code number to the current table index will be described later.
- the decoder may derive the current prediction mode using the current table index and the index mapping table.
- the index mapping table may not be directly applied to the code number, but may be applied to the current table index created using the index information of the MPM candidate.
- the number of entries in the index mapping table may be equal to the number of intra prediction modes that the current prediction unit may have, not the number of remaining modes.
- the decoder In order to perform the conversion from the above code number to the current table index, the decoder needs to find the index value of the MPM candidate.
- an input may be one of the indexes including the current table index
- an output may be one of intra prediction modes including the current prediction mode. Therefore, the decoder can find the index value of the MPM by inputting one possible index value into the index mapping table and searching the index having the mode value of the MPM as an output.
- the decoder may store an inverse index mapping table.
- an input may be one of intra prediction modes, and an output may be one of indexes including the current table index.
- the decoder can directly apply the inverse index mapping table to the mode value of the MPM to obtain the index value of the MPM without additional calculation.
- FIG. 13 is a flow diagram illustrating one embodiment of a method for converting a code number into a current table index. In the embodiment of FIG. 13, it is assumed that the maximum number of MPM candidates is two.
- the decoder may determine whether the number of MPM candidates is one (S1310).
- the decoder may determine whether the current code number is smaller than the index of the MPM candidates (S1320). If the code number is smaller than the index of the MPM candidate, the current table index may have the same value as the code number (S1330). If the code number is not smaller than the index of the MPM candidate, the current table index may have a value in which 1 is added to the value of the code number (S1340).
- the decoder may determine whether the current code number is smaller than the smaller of the indices of the MPM candidates (S1350). If the code number is smaller than the smaller of the indexes of the MPM candidate, the current table index may have the same value as the code number (S1360).
- the decoder may determine whether the current code number is smaller than the subtracted 1 from the larger of the indexes of the MPM candidate (S1370). If the code number is smaller than the subtracted 1 from the larger ones of the MPM candidates, the current table index may have a value of 1 added to the value of the code number (S1380). If the code number is not smaller than the subtracted 1 from the larger ones of the MPM candidates, the current table index may have a value of 2 added to the value of the code number (S1390).
- the current table index may be three. Since the current code number is not smaller than the index value of the MPM candidate, the current table index may have a value obtained by adding 1 to the current code number.
- the conversion process from the above code number to the current table index is similar to the conversion process from the remaining mode to the current prediction mode in the embodiment of FIG. 9.
- the code number may be represented as preCodeNum
- the current table index may be represented as codeNum.
- the decoder can derive preCodeNum from the codeword using the inverse VLC table, and can derive codeNum from preCodeNum using the number of MPMs and the index value of the MPM.
- the decoder can derive the current prediction mode from codeNum through the index mapping table.
- the index value of the MPM corresponding to the mode value of the MPM in the index mapping table is codeNum-Ori_Prev1.
- codeNum-Ori_Prev1 is input to the index mapping table, the mode value of the MPM may be output.
- preCodeNum is smaller than codeNum-Ori_Prev1, the preCodeNum value may be assigned to codeNum as it is. If preCodeNum is greater than or equal to codeNum-Ori_Prev1, a value of preCodeNum + 1 may be assigned to codeNum.
- index values of the MPM corresponding to the mode values of the MPM in the index mapping table are codeNum-Ori_Prev1 and codeNum-Ori_Prev2.
- mode values of the MPM may be output.
- codeNum-Ori_Prev1 is smaller than codeNum-Ori_Prev2.
- preCodeNum is smaller than codeNum-Ori_Prev1, the preCodeNum value may be assigned to codeNum as it is. If preCodeNum is greater than or equal to codeNum-Ori_Prev1 and less than codeNum-Ori_Prev2-1, a value of preCodeNum + 1 may be assigned to codeNum. If preCodeNum is greater than or equal to codeNum-Ori_Prev2 ⁇ 1, a value of preCodeNum + 2 may be assigned to codeNum.
- index values of the MPMs corresponding to the mode values of the MPMs in the index mapping table are codeNum-Ori_Prev1, codeNum-Ori_Prev2,... , assume codeNum-Ori_PrevN. At this time, codeNum-Ori_Prev1 and codeNum-Ori_Prev2,.
- mode values of the MPM may be output. It is assumed that codeNum-Ori_PrevX is sorted in ascending order of MPM index values assigned thereto. In other words, it is assumed that the larger the value of X, the larger MPM index values are allocated.
- preCodeNum is smaller than codeNum-Ori_Prev1, the preCodeNum value may be assigned to codeNum as it is. If preCodeNum is greater than or equal to codeNum-Ori_Prev1 and less than codeNum-Ori_Prev2-1, a value of preCodeNum + 1 may be assigned to codeNum. When preCodeNum is greater than or equal to codeNum-Ori_Prev2-1 and less than codeNum-Ori_Prev3-2, a value of preCodeNum + 2 may be assigned to codeNum.
- preCodeNum when X has a value from 1 to N-1, preCodeNum is greater than or equal to codeNum-Ori_PrevX-(X-1) and codeNum-Ori_Prev (X + 1)-X. If small, the value of preCodeNum + X can be assigned to codeNum. Also, when X is N, when preCodeNum is greater than or equal to codeNum-Ori_PrevN-(N-1), a value of preCodeNum + N may be assigned to codeNum.
- Inputs for the processing may include a position of a current block in the current picture, a size of a current prediction unit, an intra prediction mode of a previously reconstructed neighboring block, an index mapping table, an inverse index mapping table, and the like.
- the output may be the current intra prediction mode, updated index mapping table, and updated inverse index mapping table for the current prediction unit. This can be represented as follows.
- intraModeTable may represent an index mapping table and invIntraModeTable may represent an inverse index mapping table.
- the decoder may derive the neighboring blocks used for MPM candidate derivation and derive the intra prediction mode of each derived neighboring block. This can be represented as follows.
- the decoder may derive the MPM candidates using the intra prediction mode of the neighboring blocks, which may be represented as follows.
- candIntraPredModeN may represent an MPM candidate.
- the decoder may derive the MPM candidate list and the number of MPM candidates included in the list using the derived MPM candidates. This can be represented as follows.
- candModeList may represent an MPM candidate list and NumMPMCand may represent the number of MPM candidates.
- the decoder may derive the index value of the MPM according to the number of prediction modes that the current prediction unit may have.
- the decoder may use an inverse index mapping table to derive an index value of the MPM, and construct an MPM index list using the derived index values of the MPM. This can be represented as follows.
- intraPredModeNum represents the number of prediction modes that a current prediction unit can have.
- the condition for intraPredModeNum is not limited to 3 and / or 17, for example, 18 instead of 3 and 18 may be used instead of 3, respectively.
- the decoder may derive the current prediction mode from the MPM.
- the decoder may derive the current table index from the code number.
- the decoder may derive the current prediction mode by applying the index mapping table to the derived current table index.
- a separate index mapping table may not be applied. This may be represented as follows, where rem_intra_luma_pred_mode may correspond to the code number and rank_intra_luma_pred_mode may correspond to the current table index.
- condition for intraPredModeNum is not limited to 3, but 4 may be used instead of 3, for example.
- the decoder may update the index mapping table and the reverse index mapping table. This can be represented as follows.
- condition for intraPredModeNum is not limited to 3, but 4 may be used instead of 3, for example.
- the parsing process for deriving the code number can be expressed as follows.
- the portions marked with strikethrough are portions related to the use of the index mapping table and represent portions not used in the parsing process.
- the decoder derives the current table index from the code number and then applies the index mapping table to the current table index, so that the index mapping table may not be used in the parsing process.
- the index mapping table and the inverse index mapping table may be used.
- an embodiment of the source code for the index mapping table and the reverse index mapping table may be represented as follows.
- g_auiIntraModeTableD17 represents an index mapping table
- g_auiIntraModeTableE17 represents an inverse index mapping table.
- the numbers included in each list represent the mode values of the prediction mode.
- the prediction modes included in each list may be assigned an index of the index mapping table.
- an index of N-1 may be allocated to the N th prediction mode in the list.
- index 2 may be allocated to the prediction mode 9.
- an embodiment of the source code for the index mapping table and the reverse index mapping table can be represented as follows.
- g_auiIntraModeTableD34 represents an index mapping table
- g_auiIntraModeTableE34 represents an inverse index mapping table.
- the numbers included in each list represent the mode values of the prediction mode.
- the prediction modes included in each list may be assigned an index of the index mapping table.
- an index of N-1 may be allocated to the N th prediction mode in the list.
- index 3 may be allocated to the prediction mode 30.
- the VLC table may also be used.
- the VLC table may be configured using a Huffman code.
- an embodiment of the source code for the VLC table can be represented as follows.
- the upper list may be used when the number of MPM candidates is 1, and the lower list may be used when the number of MPM candidates is 2.
- the first component in each list in each huff17_2 and lengthHuff17_2 may be a component for indicating the MPM flag.
- the MPM flag may be a flag indicating whether a candidate having the same prediction mode as the current prediction unit exists among the MPM candidates, for example, may be prev_intra_luma_pred_flag. When the MPM flag value is 1, information about a remaining mode may not be transmitted.
- the second to last components in each list in each huff17_2 and lengthHuff17_2 may indicate that the MPM flag value is 0, and may indicate what value the code number to be transmitted has. In this case, since the renumbering mode of the current prediction unit may be reflected in the code number, it may also be referred to as a rank of the remaining mode.
- components in huff17_2 may represent a Huffman binary number represented by a decimal number
- components in lengthHuff17_2 may represent a Huffman binary length.
- the length of the Huffman binary number may indicate a length including a bit (1 bit) for indicating the MPM flag.
- the encoder and / or decoder may refer to the N + 2th component in each list in huff17_2 and lengthHuff17_2. This is because the first components in the list are components for indicating the MPM flag, and the second components are components for indicating the case where the code number is zero.
- the encoder and / or decoder may refer to the third component in the top list in huff17_2 and lengthHuff17_2. Since the third component is 5 in huff17_2 and the third component in lengthHuff17_2 is 4, the codeword corresponding to code number 1 may be '0101'. In this case, '0' located in the first bit may indicate the MPM flag, and '101' located in the remaining three bits may indicate a code number, that is, a rank of the remaining mode.
- an embodiment of the source code for the VLC table may be represented as follows.
- components in huff34_2 may represent a Huffman binary number represented by a decimal number
- components in lengthHuff34_2 may represent a Huffman binary length.
- the encoder and the decoder may use a fixed number of MPM candidates. Assuming that the number of prediction modes that a current prediction unit can have is 18 and the number of MPM candidates is always fixed at 2, an embodiment of the source code for the VLC table may be represented as follows.
- const UInt huff17_2 [18] ⁇ 1, 7, 4, 1, 12, 10, 7, 6, 5, 4, 1, 0, 26, 23, 22, 55, 54, 0 ⁇ ;
- huff17_2 and lengthHuff17_2 may each have only one list.
- the method of mapping a codeword and a code number through the code is the same as the method described above.
- the encoder and / or decoder may refer to the third component in the lists in huff17_2 and lengthHuff17_2. Since the third component in huff17_2, that is, huff17_2 [2] is 4 and the third component in lengthHuff17_2, that is, lengthHuff17_2 [2], is 4, the codeword corresponding to code number 1 may be '0100'. In this case, '0' located in the first bit may represent the MPM flag, and '100' located in the remaining three bits may represent a code number, that is, a rank of the remaining mode.
- an embodiment of the source code for the VLC table may be represented as follows.
- const UInt huff34_2 [35] ⁇ 1, 1, 4, 0, 12, 3, 28, 21, 5, 4, 63, 60, 58, 53, 47, 46, 45, 41, 40, 125, 124, 123, 119, 118, 111, 110, 109, 108, 105, 104, 89, 88, 245, 244, 0 ⁇ ;
- huff17_2 and lengthHuff17_2 may each have only one list.
- the method of mapping a codeword and a code number through the code is the same as the method described above.
- the inverse index mapping table may be directly applied to the actual prediction mode of the current prediction unit.
- the actual prediction mode of the direct current prediction unit is applied. Can be obtained.
- the mapping table may be updated according to the actual prediction mode of the current prediction unit. Therefore, the mapping table may reflect the distribution of the actual intra prediction mode rather than the remaining mode.
- the number of entries in the index mapping table and the reverse index mapping table is equal to the number of remaining modes that the current prediction unit may have. Therefore, in this case, different mapping tables should be used according to the number of MPMs.
- the number of entries of the index mapping table and the reverse index mapping table is equal to the number of actual prediction modes that the current prediction unit may have. Since the number of actual prediction modes that a current prediction unit can have is constant regardless of the number of MPMs, the encoder and the decoder do not need to use different mapping tables according to the number of MPMs. Therefore, memory can be saved and the characteristics of the contents can be reflected more quickly in the mapping table, so that the amount of bits transmitted from the encoder to the decoder can be reduced. However, as described above in the embodiment of FIG. 12, the decoder may use a separate inverse index mapping table to derive the index value of the MPM.
- Table 1 below is an embodiment schematically showing the number of mapping tables required by the decoder and the number of entries in each mapping table according to the decoding method of the intra prediction mode.
- the number of MPM candidates may be one or two
- the number of prediction modes that a current prediction unit may have is assumed to be 17 or 34.
- the number of prediction modes that a current prediction unit may have is not limited to the following embodiments and may vary depending on implementation and needs. For example, the number of prediction modes may be 18 instead of 17 and 35 instead of 34.
- the number of entries in each mapping table in Table 1 may also vary.
- two index mapping tables may be required in the intra prediction mode decoding method according to the embodiment of FIG. 9.
- one of the two index mapping tables may have 15 entries and the other may have 16 entries.
- two index mapping tables may be required in the intra prediction mode decoding method according to the embodiment of FIG. 9.
- one of the two index mapping tables may have 32 entries, and the other may have 33 entries.
- the mapping tables may have 17 entries each.
- the decoder can derive the index value of the MPM without using a separate inverse index mapping table.
- each mapping table may have 34 entries.
- only one index mapping table having 34 entries may be required in the intra prediction mode decoding method according to the embodiment of FIG. 12. This is because the decoder can derive the index value of the MPM without using a separate inverse index mapping table.
- the encoder and the decoder may use a fixed number of MPM candidates. If the number of MPM candidates is fixed, the number of remaining modes may also be fixed. In this case, only one index mapping table may be used in the intra prediction mode decoding method according to the above-described embodiment of FIG. 9 for each of 17 and 34 prediction modes that the current prediction unit may have. have.
- the remaining mode is decoded for the prediction unit in which one of the MPM candidates is selected as the current prediction mode. May not be sent to the device.
- the mapping table used in the embodiments of FIGS. 10 to 13 is based on the actual prediction mode of the current prediction unit rather than the remaining mode, when one of the MPM candidates is selected as the current prediction mode, that is, It may be updated even if it is not transmitted.
- the encoder and the decoder may allow the distribution of the intra prediction modes to be reflected in the mapping table more quickly.
- the distribution of code number values may vary depending on whether the DC mode is included in the MPM candidate list.
- the occurrence frequency of the DC mode or the planar mode may increase. Therefore, in this case, code number values reflecting the remaining mode except for the MPM candidates may be more evenly distributed than when the DC mode is not included in the MPM candidate list. That is, when the DC mode is included in the MPM candidate list, the frequency of occurrence of a small code number may be relatively low as compared with that otherwise.
- the code number binarization method may be applied differently, thereby improving the coding efficiency.
- the codeword may be determined such that a relatively large number of bits are allocated to a small code number, as compared with the case where the DC mode is included in the MPM candidate list.
- FIG. 14 is a flowchart schematically illustrating an intra prediction mode encoding method according to an embodiment of the present invention.
- the encoder obtains a current table index from the prediction mode of the current prediction unit (S1410).
- the encoder may generate a current table index for the current prediction mode by applying an inverse index mapping table directly to the prediction mode of the current prediction unit.
- the number of entries in the inverse index mapping table may be equal to the number of intra prediction modes that the current prediction unit may have. Embodiments of the inverse index mapping table used for intra prediction mode encoding have been described above.
- the encoder derives the code number from the current table index (S1420).
- the encoder may derive the code number from the current table index information and the index information of the MPM candidate.
- the current table index information may include a value of a current table index
- the index information of an MPM candidate may include a number of MPM candidates and an index value of an MPM candidate.
- the code number may also be called a codeword index. Specific embodiments of the conversion process from the current table index to the code number may be as described above in the embodiments of FIGS. 10 and 11.
- the encoder may convert the code number into a codeword using the VLC table, and the codeword may be transmitted to the decoder (S1430).
- Embodiments of the VLC table used for intra prediction mode encoding have been described above.
- 15 is a flowchart schematically illustrating an intra prediction mode decoding method according to an embodiment of the present invention.
- a decoder may convert a codeword received from an encoder into a code number using an inverse VLC table (S1510).
- the code number may also be called a codeword index.
- the decoder derives a current table index from the code number (S1520).
- the decoder may generate the current table index using the code number and the index information of the MPM candidate.
- the index information of the MPM candidate may include the number of MPM candidates and the value of the index of the MPM candidate.
- the decoder may use an inverse index mapping table to derive the index of the MPM candidate. Specific embodiments of the conversion process from the code number to the current table index may be as described above with reference to FIGS. 12 and 13.
- the decoder obtains an intra prediction mode for the current prediction unit from the current table index (S1530).
- the decoder may derive a current prediction mode by applying an index mapping table to the current table index.
- the index mapping table may not be directly applied to the code number, and may be applied to the current table index generated using the index information of the MPM candidate.
- the number of entries in the index mapping table may be equal to the number of intra prediction modes that the current prediction unit may have. Embodiments of the index mapping table used for intra prediction mode encoding have been described above.
- the encoder and the decoder may use CABAC as well as CAVLC for entropy encoding / decoding.
- CABAC CABAC entropy encoding method
- the encoder may binarize a symbol, convert the symbol into a bin, and generate a bitstream by performing arithmetic coding on the bin according to the occurrence probability of the bin.
- the decoder may also perform entropy decoding using CABAC correspondingly.
- the above-described intra prediction mode encoding / decoding method according to the embodiments of FIGS. 10 to 16 may be performed not only when entropy encoding / decoding is performed using CAVLC but also when entropy encoding / decoding is performed using CABAC. Can be applied.
- the encoder and the decoder may perform CABAC entropy encoding / decoding by using a mapping table having the same form as the mapping table described above in the embodiments of FIGS. 10 to 16, and the mapping table is not a remaining mode.
- the distribution of the intra prediction mode may be reflected.
Abstract
Description
Claims (17)
- 인트라(intra) 모드에서 현재 블록에 대한 예측을 수행하는 영상 복호화 방법으로서,
코드 넘버(code number) 및 MPM 인덱스 정보를 이용하여 현재 테이블 인덱스(current table index)를 생성하는 단계; 및
상기 현재 테이블 인덱스에 인덱스 매핑 테이블(index mapping table)을 적용하여 현재 예측 모드를 도출하는 단계를 포함하고,
상기 MPM 인덱스 정보는 MPM 후보(MPM candidate)의 개수 및 상기 MPM 후보의 인덱스의 값을 포함하고, 상기 MPM 후보의 인덱스는 상기 인덱스 매핑 테이블에서 상기 MPM 후보에 할당되는 인덱스이고, 상기 현재 예측 모드는 현재 예측 유닛의 인트라 예측 모드이고, 상기 현재 테이블 인덱스는 상기 인덱스 매핑 테이블에서 상기 현재 예측 모드에 할당되는 인덱스인 영상 복호화 방법. - 청구항 1에 있어서, 역 VLC 테이블을 이용하여 부호화기로부터 수신한 코드워드(codeword)를 상기 코드 넘버로 변환(convert)하는 단계를 추가로 포함하는 영상 복호화 방법.
- 청구항 1에 있어서, 상기 인덱스 매핑 테이블 내 엔트리(entry)의 개수는 상기 현재 예측 유닛이 가질 수 있는 인트라 예측 모드의 개수와 동일한 영상 복호화 방법.
- 청구항 1에 있어서, 상기 MPM 후보의 인덱스 값은 상기 MPM 후보의 모드값에 역 인덱스 매핑 테이블(inverse index mapping table)을 적용함으로써 도출되는 영상 복호화 방법.
- 청구항 1에 있어서, 상기 MPM 후보의 개수는 소정의 고정된 값인 영상 복호화 방법.
- 청구항 5에 있어서, 상기 소정의 고정된 값은 2, 3 또는 4인 영상 복호화 방법.
- 청구항 1에 있어서, 상기 현재 테이블 인덱스의 발생 빈도에 기초하여 상기 인덱스 매핑 테이블을 업데이트하는 단계를 추가로 포함하는 영상 복호화 방법.
- 청구항 7에 있어서, 상기 인덱스 매핑 테이블은, 상기 MPM 후보 중 하나가 인트라 예측 모드로 선택되는 예측 유닛에 대해서도 업데이트되는 영상 복호화 방법.
- 코드 넘버(code number) 및 MPM 인덱스 정보를 이용하여 현재 테이블 인덱스(current table index)를 생성하고, 상기 현재 테이블 인덱스에 인덱스 매핑 테이블(index mapping table)을 적용하여 현재 예측 모드를 도출하는 엔트로피 복호화부; 및
상기 도출된 현재 예측 모드를 이용하여 현재 블록에 대한 인트라 예측을 수행하는 예측부를 포함하고,
상기 MPM 인덱스 정보는 MPM 후보(MPM candidate)의 개수 및 상기 MPM 후보의 인덱스의 값을 포함하고, 상기 MPM 후보의 인덱스는 상기 인덱스 매핑 테이블에서 상기 MPM 후보에 할당되는 인덱스이고, 상기 현재 예측 모드는 상기 현재 예측 유닛의 인트라 예측 모드이고, 상기 현재 테이블 인덱스는 상기 인덱스 매핑 테이블에서 상기 현재 예측 모드에 할당되는 인덱스인 영상 복호화 장치. - 인트라 예측 모드 정보를 엔트로피 복호화하기 위한 인트라 예측 모드 복호화 방법으로서,
코드 넘버(code number) 및 MPM 인덱스 정보를 이용하여 현재 테이블 인덱스(current table index)를 생성하는 단계; 및
상기 현재 테이블 인덱스에 인덱스 매핑 테이블(index mapping table)을 적용하여 현재 예측 모드를 도출하는 단계를 포함하고,
상기 MPM 인덱스 정보는 MPM 후보(MPM candidate)의 개수 및 상기 MPM 후보의 인덱스의 값을 포함하고, 상기 MPM 후보의 인덱스는 상기 인덱스 매핑 테이블에서 상기 MPM 후보에 할당되는 인덱스이고, 상기 현재 예측 모드는 현재 예측 유닛의 인트라 예측 모드이고, 상기 현재 테이블 인덱스는 상기 인덱스 매핑 테이블에서 상기 현재 예측 모드에 할당되는 인덱스인 인트라 예측 모드 복호화 방법. - 청구항 10에 있어서, 역 VLC 테이블을 이용하여 부호화기로부터 수신한 코드워드(codeword)를 상기 코드 넘버로 변환(convert)하는 단계를 추가로 포함하는 인트라 예측 모드 복호화 방법.
- 청구항 10에 있어서, 상기 인덱스 매핑 테이블 내 엔트리(entry)의 개수는 상기 현재 예측 유닛이 가질 수 있는 인트라 예측 모드의 개수와 동일한 인트라 예측 모드 복호화 방법.
- 청구항 10에 있어서, 상기 MPM 후보의 인덱스 값은 상기 MPM 후보의 모드값에 역 인덱스 매핑 테이블(inverse index mapping table)을 적용함으로써 도출되는 인트라 예측 모드 복호화 방법.
- 청구항 10에 있어서, 상기 MPM 후보의 개수는 소정의 고정된 값인 인트라 예측 모드 복호화 방법.
- 청구항 14에 있어서, 상기 소정의 고정된 값은 2, 3 또는 4인 인트라 예측 모드 복호화 방법.
- 청구항 10에 있어서, 상기 현재 테이블 인덱스의 발생 빈도에 기초하여 상기 인덱스 매핑 테이블을 업데이트하는 단계를 추가로 포함하는 인트라 예측 모드 복호화 방법.
- 청구항 16에 있어서, 상기 인덱스 매핑 테이블은, 상기 MPM 후보 중 하나가 인트라 예측 모드로 선택되는 예측 유닛에 대해서도 업데이트되는 인트라 예측 모드 복호화 방법.
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CN107750455B (zh) * | 2015-06-18 | 2020-08-18 | 高通股份有限公司 | 帧内预测及帧内模式译码 |
US10841593B2 (en) | 2015-06-18 | 2020-11-17 | Qualcomm Incorporated | Intra prediction and intra mode coding |
US11463689B2 (en) | 2015-06-18 | 2022-10-04 | Qualcomm Incorporated | Intra prediction and intra mode coding |
WO2017204427A1 (ko) * | 2016-05-23 | 2017-11-30 | 가온미디어 주식회사 | 영상 처리 방법, 그를 이용한 영상 복호화 및 부호화 방법 |
US11277644B2 (en) | 2018-07-02 | 2022-03-15 | Qualcomm Incorporated | Combining mode dependent intra smoothing (MDIS) with intra interpolation filter switching |
US11303885B2 (en) | 2018-10-25 | 2022-04-12 | Qualcomm Incorporated | Wide-angle intra prediction smoothing and interpolation |
CN114270825A (zh) * | 2019-08-19 | 2022-04-01 | 北京字节跳动网络技术有限公司 | 基于计数器的帧内预测模式的初始化 |
Also Published As
Publication number | Publication date |
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KR20140037130A (ko) | 2014-03-26 |
US9762900B2 (en) | 2017-09-12 |
KR101876173B1 (ko) | 2018-07-09 |
US20140126629A1 (en) | 2014-05-08 |
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