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WO2013066045A1 - Procédé et appareil d'initialisation d'une liste d'images de référence - Google Patents

Procédé et appareil d'initialisation d'une liste d'images de référence Download PDF

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Publication number
WO2013066045A1
WO2013066045A1 PCT/KR2012/009052 KR2012009052W WO2013066045A1 WO 2013066045 A1 WO2013066045 A1 WO 2013066045A1 KR 2012009052 W KR2012009052 W KR 2012009052W WO 2013066045 A1 WO2013066045 A1 WO 2013066045A1
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Prior art keywords
picture
pictures
reference picture
reference pictures
poc
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English (en)
Korean (ko)
Inventor
헨드리헨드리
박승욱
전용준
임재현
김철근
김정선
박내리
전병문
박준영
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LG Electronics Inc
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LG Electronics Inc
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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
    • H04N19/109—Selection of coding mode or of prediction mode among a plurality of temporal predictive coding modes
    • 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
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction

Definitions

  • the present invention relates to image compression technology, and more particularly, to a method and apparatus for efficiently encoding / decoding a video signal.
  • High-efficiency image compression technology can be used to effectively transmit, store, and reproduce high-resolution, high-quality video information.
  • inter prediction and intra prediction may be used.
  • the pixel value of the current picture is predicted by referring to information of another picture
  • the intra prediction method the pixel value is predicted by using the correlation between pixels in the same picture. do.
  • the encoding apparatus and the decoding apparatus perform prediction based on a reference picture list indicating reference pictures available to the current block (current picture).
  • the decoding apparatus may effectively perform inter prediction by constructing a reference picture list based on information received from the encoding apparatus.
  • An object of the present invention is to provide a method and apparatus for constructing a reference picture list for performing prediction more efficiently.
  • the present invention is a method of initializing and configuring a reference picture list, and an object thereof is to provide a method and apparatus for considering a quantization parameter as well as a picture order count (POC) of reference pictures.
  • POC picture order count
  • the present invention is a method of initializing and configuring a reference picture list, and an object thereof is to provide a method and apparatus that considers a temporal level as well as a picture order count (POC) of reference pictures.
  • POC picture order count
  • An embodiment of the present invention is a method of initializing a reference picture list, the method comprising: aligning reference pictures according to picture order counts (POCs) of respective reference pictures for inter prediction on a current picture, and among the sorted pictures Selecting reference pictures to be used for prediction of the picture, wherein the selecting step may select reference pictures based on quantization parameters of the reference pictures.
  • POCs picture order counts
  • reference pictures having a quantization parameter less than or equal to the quantization parameter of the current picture may be selected among the aligned reference pictures.
  • reference pictures having a temporal level lower than or equal to the temporal level of the current picture may be selected among the aligned reference pictures.
  • the sort order determined in the sorting step may be maintained between the selected reference pictures.
  • the selected reference pictures may be sorted in descending order of the POC.
  • the selected reference pictures are sorted in the ascending order of the POC. Can be.
  • Reference pictures aligned in the alignment step may be at least one short-term reference picture and at least one long-term reference picture.
  • the long-term reference pictures determined to be used may be aligned following the selected reference pictures.
  • Reference pictures that are not selected in the selecting step may be aligned next to the selected reference pictures.
  • a reference picture list initialization apparatus comprising: a reference picture alignment unit for arranging a reference picture according to a picture order count (POC) of each reference picture for inter prediction on a current picture and the aligned pictures And a reference picture selector that selects reference pictures for reference pictures to be used for prediction of the current picture, wherein the reference picture selector may select a reference picture based on quantization parameters of the reference pictures.
  • POC picture order count
  • the reference picture selector may select reference pictures having a quantization parameter that is less than or equal to the quantization parameter of the current picture among the aligned reference pictures.
  • the reference picture selector may select reference pictures having a temporal level lower than or equal to the temporal level of the current picture among the aligned reference pictures.
  • An alignment order determined by the reference picture alignment unit may be maintained between the pictures selected by the reference picture selection unit.
  • the selected reference pictures may be sorted in descending order of POC, and for reference picture list 1 for the current picture, the selected reference pictures may be sorted in ascending order of POC. have.
  • the reference picture aligner may align at least one short-term reference picture and at least one long-term reference picture.
  • the reference picture selector may align the long term reference picture following the selected reference pictures.
  • the reference picture selector may align the non-selected reference pictures after the selected reference pictures.
  • the present invention in constructing the reference picture list, it is possible to determine the sorting order (indexing order) of the reference pictures in the reference picture list so as to obtain a more accurate prediction result.
  • prediction when initializing and configuring a reference picture list, prediction can be performed more effectively by considering not only the Picture Order Count (POC) of the reference pictures but also the quantization parameter.
  • POC Picture Order Count
  • prediction when initializing and configuring a reference picture list, prediction can be performed more effectively by considering not only the Picture Order Count (POC) of the reference pictures but also the temporal level.
  • POC Picture Order Count
  • FIG. 1 is a block diagram schematically illustrating an encoding apparatus (video encoding apparatus) according to an embodiment of the present invention.
  • FIG. 2 is a block diagram schematically illustrating an image decoding apparatus according to an embodiment of the present invention.
  • FIG. 3 is a diagram schematically illustrating an example of a candidate block that may be used when inter prediction is performed on a current block.
  • FIG. 4 is a diagram schematically illustrating a temporal level structure of reference pictures.
  • FIG. 5 is a diagram schematically illustrating an example of reference picture list initialization according to the present invention.
  • FIG. 6 is a diagram schematically illustrating another example of initialization of a reference picture list according to the present invention.
  • FIG. 7 is a flowchart schematically illustrating a method of performing initialization of a reference picture list according to the present invention.
  • FIG. 8 schematically illustrates an apparatus for performing initialization of a reference picture list according to the present invention.
  • each of the components in the drawings described in the present invention are shown independently for the convenience of description of different characteristic functions in the image encoding apparatus / decoding apparatus, each component is a separate hardware or separate software It does not mean that it is implemented.
  • 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 encoding apparatus 100 may include a picture divider 105, a predictor 110, a transformer 115, a quantizer 120, a reordering unit 125, an entropy encoding unit 130, An inverse quantization unit 135, an inverse transform unit 140, a filter unit 145, and a memory 150 are provided.
  • the picture dividing unit 105 may divide the input picture into at least one processing unit block.
  • the block as the processing unit may be a prediction unit (hereinafter referred to as a PU), a transform unit (hereinafter referred to as a TU), or a coding unit (hereinafter referred to as "CU"). It may be called.
  • the predictor 110 includes an inter predictor for performing inter prediction and an intra predictor for performing intra prediction, as described below.
  • the prediction unit 110 generates 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 CU, a TU, or a PU.
  • the prediction unit 110 may determine whether the prediction performed on the processing unit is inter prediction or intra prediction, and determine specific contents (eg, prediction mode, etc.) of each prediction method.
  • the processing unit in which the prediction is performed and the processing unit in which the details of the prediction method and the prediction method are determined may be different.
  • the prediction method and the prediction mode may be determined in units of PUs, and the prediction may be performed in units of TUs.
  • a prediction block may be generated by performing prediction based on information of at least one picture of a previous picture and / or a subsequent picture of the current picture.
  • a prediction block may be generated by performing prediction based on pixel information in a current picture.
  • a skip mode, a merge mode, a motion vector prediction (MVP), and the like can be used.
  • a reference picture may be selected for a PU and a reference block having the same size as the PU may be selected.
  • the reference block may be selected in integer pixel units.
  • a prediction block is generated in which a residual signal with the current PU is minimized and the size of the motion vector is also minimized.
  • the prediction block may be generated in integer sample units, or may be generated in sub-pixel units such as 1/2 pixel unit or 1/4 pixel unit.
  • the motion vector may also be expressed in units of integer pixels or less. For example, it may be expressed in units of 1/4 pixels for luminance samples and in units of 1/8 pixels for chrominance samples.
  • the residual may be used as the reconstructed block, and thus the residual may not be generated, transformed, quantized, or transmitted.
  • a prediction mode When performing intra prediction, a prediction mode may be determined in units of PUs, and prediction may be performed in units of PUs. In addition, a prediction mode may be determined in units of PUs, and intra prediction may be performed in units of TUs.
  • the prediction mode may have 33 directional prediction modes and at least two non-directional modes.
  • the non-directional mode may include a DC prediction mode and a planner mode (Planar mode).
  • a prediction block may be generated after applying a filter to a reference sample.
  • whether to apply the filter to the reference sample may be determined according to the intra prediction mode and / or the size of the current block.
  • the PU may be a block of various sizes / types, for example, in the case of inter prediction, the PU may be a 2N ⁇ 2N block, a 2N ⁇ N block, an N ⁇ 2N block, an N ⁇ N block (N is an integer), or the like.
  • the PU In the case of intra prediction, the PU may be a 2N ⁇ 2N block or an N ⁇ N block (where N is an integer).
  • the PU of the N ⁇ N block size may be set to apply only in a specific case.
  • the NxN block size PU may be used only for the minimum size CU or only for intra prediction.
  • PUs such as N ⁇ mN blocks, mN ⁇ N blocks, 2N ⁇ mN blocks, or mN ⁇ 2N blocks (m ⁇ 1) may be further defined and used.
  • the residual value (the residual block or the residual signal) between the generated prediction block and the original block is input to the converter 115.
  • the prediction mode information, the motion vector information, etc. used for the prediction are encoded by the entropy encoding unit 130 together with the residual value and transmitted to the decoding apparatus.
  • the transformer 115 performs transform on the residual block in transform units and generates transform coefficients.
  • the transform unit in the converter 115 may be a TU 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 convert 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 a quantization parameter by quantizing the residual values transformed by the transformation unit 115.
  • the value calculated by the quantization unit 120 is provided to the inverse quantization unit 135 and the reordering unit 125.
  • the reordering unit 125 rearranges the quantization parameter provided from the quantization unit 120. By rearranging the quantization parameters, the encoding efficiency of the entropy encoding unit 130 may be increased.
  • the reordering unit 125 may rearrange the quantization parameters in the form of a 2D block into a 1D vector form through a coefficient scanning method.
  • the reordering unit 125 may increase the entropy encoding efficiency of the entropy encoding unit 130 by changing the order of coefficient scanning based on probabilistic statistics of coefficients transmitted from the quantization unit.
  • the entropy encoding unit 130 may perform entropy encoding on the quantization parameters rearranged by the reordering unit 125.
  • Entropy encoding may include, for example, encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC).
  • the entropy encoding unit 130 may include quantization parameter information, block type information, prediction mode information, partition unit information, PU information, transmission unit information, motion vector information, and the like of the CUs received from the reordering unit 125 and the prediction unit 110.
  • Various information such as reference picture information, interpolation information of a block, and filtering information may be encoded.
  • the entropy encoding unit 130 may apply a constant change to a parameter set or syntax to be transmitted.
  • the inverse quantization unit 135 inverse quantizes the quantized values in the quantization unit 120, and the inverse transformer 140 inversely transforms the inverse quantized values in the inverse quantization unit 135.
  • the reconstructed block may be generated by combining the residual values generated by the inverse quantizer 135 and the inverse transform unit 140 and the prediction blocks predicted by the prediction unit 110.
  • a reconstructed block is generated by adding a residual block and a prediction block through an adder.
  • the adder may be viewed as a separate unit (restore block generation unit) for generating a reconstruction block.
  • the filter unit 145 may apply a deblocking filter, an adaptive loop filter (ALF), and a sample adaptive offset (SAO) to the reconstructed picture.
  • ALF adaptive loop filter
  • SAO sample adaptive offset
  • the deblocking filter may remove 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 the reconstructed image with the original image after the block is filtered through the deblocking filter. ALF may be performed only when high efficiency is applied.
  • the SAO restores the offset difference from the original image on a pixel-by-pixel basis to the residual block to which the deblocking filter is applied, and is applied in the form of a band offset and an edge offset.
  • 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.
  • the image decoding apparatus 200 may include an entropy decoding unit 210, a reordering unit 215, an inverse quantization unit 220, an inverse transform unit 225, a prediction unit 230, and a filter unit 235.
  • Memory 240 may be included.
  • the input bitstream may be decoded according to a procedure in which image information is processed in the image encoding apparatus.
  • variable length coding such as CAVLC (VLC)
  • VLC variable length coding
  • the entropy decoding unit 210 also uses the VLC used in the encoding apparatus. Entropy decoding may be performed by implementing the same VLC table as the table.
  • CABAC CABAC is used to perform entropy encoding in the image encoding apparatus
  • the entropy decoding unit 210 may perform entropy decoding using CABAC correspondingly.
  • Information for generating the prediction block among the information decoded by the entropy decoding unit 210 is provided to the prediction unit 230, and the residual value where the entropy decoding is performed by the entropy decoding unit 210 is transferred to the reordering unit 215. Can be entered.
  • the reordering unit 215 may reorder the entropy decoded bitstream by the entropy decoding unit 210 based on a method of reordering the image encoding apparatus.
  • the reordering unit 215 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 215 may be realigned by receiving information related to coefficient scanning performed by the encoding apparatus and performing reverse scanning based on the scanning order performed by the encoding apparatus.
  • the inverse quantization unit 220 may perform inverse quantization based on the quantization parameter provided by the encoding apparatus and the coefficient values of the rearranged block.
  • the inverse transform unit 225 may perform inverse DCT and / or inverse DST on the DCT and the DST performed by the transform unit of the encoding apparatus with respect to the quantization result performed by the image encoding apparatus.
  • the inverse transformation may be performed based on a transmission unit determined by the encoding apparatus or a division unit of an image.
  • the DCT and / or DST in the encoding unit of the encoding apparatus 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 transform unit 225 of the decoding apparatus is configured in the transformation unit of the encoding apparatus.
  • Inverse transformation may be performed based on the performed transformation information.
  • the prediction unit 230 may generate the prediction block based on the prediction block generation related information provided by the entropy decoding unit 210 and the previously decoded block and / or picture information provided by the memory 240.
  • intra prediction for generating a prediction block based on pixel information in the current picture may be performed.
  • inter prediction on the current PU may be performed based on information included in at least one of a previous picture or a subsequent picture of the current picture.
  • motion information required for inter prediction of the current PU provided by the image encoding apparatus for example, a motion vector, a reference picture index, and the like, may be derived by checking a skip flag, a merge flag, and the like received from the encoding apparatus.
  • the reconstruction block may be generated using the prediction block generated by the predictor 230 and the residual block provided by the inverse transform unit 225.
  • FIG. 2 it is described that the reconstructed block is generated by combining the prediction block and the residual block in the adder.
  • the adder may be viewed as a separate unit (restore block generation unit) for generating a reconstruction block.
  • the residual is not transmitted and the prediction block may be a reconstruction block.
  • the reconstructed block and / or picture may be provided to the filter unit 235.
  • the filter unit 235 may apply deblocking filtering, sample adaptive offset (SAO), and / or ALF to the reconstructed block and / or picture.
  • SAO sample adaptive offset
  • the memory 240 may store the reconstructed picture or block to use as a reference picture or reference block and provide the reconstructed picture to the output unit.
  • encoded or decoded pictures are stored in a memory, for example, a decoded picture buffer (DPB).
  • DPB decoded picture buffer
  • the encoding apparatus and the decoding apparatus may maintain a list of previously coded / decoded pictures in the reference picture list for use in inter prediction.
  • inter prediction When inter prediction is applied, the encoding apparatus and the decoding apparatus may perform prediction with respect to a target block (current block) of the current picture with reference to another picture. 1 and 2, inter prediction may be performed by a prediction unit in an encoding apparatus and a decoding apparatus.
  • the current block is predicted by using information of neighboring blocks that are adjacent to the current block and are available.
  • the neighboring block is available among the blocks co-located with the current block in reference pictures to which the current block can refer (hereinafter, referred to as 'col block' (co- located blocks).
  • the neighboring block used to perform prediction on the current block in inter prediction is referred to as a candidate block for convenience of description.
  • prediction of a current block is performed using information of a candidate block.
  • motion information eg, a motion vector
  • a reference picture of a selected block among candidate blocks may be used as motion information and a reference picture for the current block.
  • a Col block is used as a candidate block
  • a picture of a specific index may be used as a reference picture in the reference picture list.
  • motion information (eg, a motion vector) of a selected block among candidate blocks may be used as a motion vector for the current block, and reference picture information for the current block may be transmitted from the encoding device to the decoding device.
  • the difference between the MVP derived from the candidate block and the motion vector for the current block is transmitted from the encoding device to the decoding device, and the prediction unit of the decoding device may derive the motion information for the current block based on the MVP and the MVD.
  • FIG. 3 is a diagram schematically illustrating an example of a candidate block that may be used when inter prediction is performed on a current block.
  • the prediction unit of the encoding apparatus and the decoding apparatus may use a block at a predetermined position around the current block 400 as a candidate block.
  • a block at a predetermined position around the current block 400 For example, in the example of FIG. 3, two blocks A 0 410 and A 1 420 located at the lower left end of the current block, and three blocks B 0 430, B 1 440, B located at the upper right and upper left of the current block. 2 450 may be selected as a candidate block.
  • the above-described Col block 460 may be used as a candidate block as a temporal candidate block.
  • the reference picture for the current block may be derived from the reference picture of the neighboring block or may be indicated from the decoding apparatus.
  • the prediction unit of the decoding apparatus may use the reference picture of the neighboring block as the reference picture of the current block.
  • the prediction unit of the decoding apparatus may receive information indicating a reference picture for the current block from the encoding apparatus.
  • Pictures encoded / decoded prior to the current picture may be stored in a memory (eg, a Decoded Picture Buffer (DPB)) and used for prediction of the current block (current picture).
  • a memory eg, a Decoded Picture Buffer (DPB)
  • DPB Decoded Picture Buffer
  • the list of pictures available for inter prediction of the current block is maintained as a reference picture list.
  • P slices are slices that are decoded through intra prediction or inter prediction using at most one motion vector and one reference picture.
  • a B slice is a slice that is decoded through intra prediction or inter prediction using up to two motion vectors and two reference pictures.
  • the reference picture includes a short term reference picture and a long term reference picture.
  • Reference picture list 0 (referred to as 'L0' for convenience of description) is a reference picture list used for inter prediction of a P slice or a B slice.
  • Reference picture list 1 (referred to as 'L1' for convenience of description) is used for inter prediction of a B slice. Therefore, L0 is used for inter prediction on blocks of P slices that perform unidirectional prediction, and L0 and L1 are used for inter prediction on blocks of B slices which perform bidirectional prediction.
  • the decoding apparatus constructs a reference picture list when decoding the P slice and the B slice through inter prediction.
  • the reference picture used for inter prediction is specified through a reference picture list.
  • the reference picture index is an index indicating a reference picture on the reference picture list.
  • the reference picture list may be configured based on a reference picture set transmitted from the encoding apparatus.
  • Reference pictures constituting the reference picture list may be stored in a memory (eg, DPB).
  • Pictures stored in memory are managed by the encoding device and the decoding device.
  • the reference picture can be managed by a simple method that is stored in a memory and released after a certain time, but there are some problems. For example, even if there is a reference picture that is no longer needed, the efficiency is low because it cannot be ejected directly from the memory. Also, since it is released from the memory after a certain time, it becomes difficult to manage the long-term reference picture.
  • a MMCO Memory Management Command Operation
  • a method of transmitting a set of reference pictures necessary for decoding a slice in each slice header may be used.
  • the reference picture set includes reference pictures used for reference of the current picture / slice or future picture / slice.
  • the reference picture set is information transmitted from an encoding device to a decoding device, and pictures included in the reference picture set may be specified by a picture order count (POC).
  • POC Picture Order Count
  • the POCs of the reference pictures included in the reference picture set may be relative POCs to the POCs of the current picture.
  • the relative POC represents the POC difference between two pictures in the reference picture set.
  • the relative POC of the reference pictures before the current picture (the reference pictures with a smaller POC than the POC of the current picture) in the POC order is the POC difference from the previous reference picture in the reference picture set.
  • the relative POC of the reference pictures after the current picture in the POC order (reference pictures having a larger POC than the POC of the current picture) is also a POC difference from the immediately preceding reference picture in the reference picture set.
  • the reference picture set may be signaled from the encoding device to the decoding device for each picture to which inter prediction is applied.
  • the reference picture lists L0 and L1 may be configured based on a reference picture set received from the encoding apparatus.
  • the reference picture list L0 In the case of constructing the reference picture list L0, short-term reference pictures having a smaller POC than the POC of the current picture among the received reference picture sets (pictures before the current picture or relative POCs in the POC order have negative values). ) And short-term reference pictures whose POC is larger than the POC of the current picture (pictures after the current picture or pictures whose relative POC has a positive sign in POC order) whose POC is smaller than the POC of the current picture.
  • the reference picture list may be constructed by allocating the reference picture indexes from the pictures. The long term reference picture may then be added to the reference picture list L0.
  • the reference picture list L1 In the case of configuring the reference picture list L1, pictures having a POC smaller than the POC of the current picture among the received reference picture sets (pictures before the current picture or pictures with a negative sign of a relative POC in the POC order) And the reference picture index starting from a picture having a larger POC than the POC of the current picture (pictures after the current picture in the POC order or pictures whose relative POC has a positive value) among the pictures having a larger POC than the POC of the current picture. Is assigned to construct a reference picture list.
  • Reference pictures added to the reference picture list may be assigned a reference picture index in order.
  • the decoding apparatus may utilize the first N (reference pictures from index 0 to index N-1) among the reference pictures included in the reference picture list as available reference pictures.
  • the information about the number N of available reference pictures may be transmitted from the encoding apparatus.
  • the reference picture list may be explicitly transmitted from the encoding device to the decoding device.
  • the encoding apparatus may transmit a specific entry constituting the reference picture list together with the reference picture list modification information indicating that the derived reference picture list is modified.
  • the encoding device may indicate whether L0 or L1 will be implicitly derived or explicitly specified using the transmitted entry information. For example, when the flag value is 0 using the flag information, the reference picture list is implicitly derived, and when the flag value is 1, the reference picture list may be explicitly specified using the transmitted entry information.
  • the encoding device may transmit entry information about L0 when L0 is explicitly specified.
  • the entry information about L0 may indicate a reference picture corresponding to the index on L0.
  • the encoding apparatus may transmit entry information about L1 when L1 is explicitly specified.
  • the entry information about L1 may indicate a reference picture corresponding to the index on L1.
  • a reference picture list is specified by entry information
  • forward short-term reference pictures eg, pictures having a POC smaller than the current picture
  • backward short-term reference pictures eg, pictures having a POC larger than the current picture
  • the order (reference picture index) in the reference picture list of the long-term reference pictures may be different from the order (reference picture index) in the reference picture list implicitly derived.
  • available reference pictures to be utilized may also be different from the case of the reference picture list implicitly derived.
  • the decoding apparatus may configure the same reference picture as the reference picture list configured by the encoding apparatus based on the reference picture list modification information information and the entry information.
  • the encoding apparatus and the decoding apparatus may derive the reference picture list to be used for inter prediction of the current picture based on the POC of the pictures as described above.
  • a reference picture set has been described by considering only pictures that are available for convenience of description, but the reference picture list is constructed by considering whether or not the reference pictures are used in the encoder and the decoder. can do.
  • the reference picture list when initializing a reference picture list with respect to a current picture, the reference picture list may be initialized through a reference picture sorting stage and a reference picture selection step.
  • the reference picture set may be marked as being used as a reference picture, depending on whether it is used as a reference picture in a memory, such as a DPB (marked as “used for refernce”).
  • the available reference pictures marked as used as reference pictures are aligned in the DPB.
  • the reference pictures may be sorted in descending order from the largest POC to the smallest POC according to a picture number (PicNum), for example, a POC.
  • PicNum picture number
  • the sorting of the short-term reference pictures is first performed.
  • the entryShortTerm value is placed on the L0 in descending order of the POC.
  • pictures marked as being used as a short-term reference picture pictures having a POC value smaller than the POC of the current picture are located in descending order of the POC from the beginning of L0.
  • the long-term reference pictures for the L0 list may then be sorted.
  • long-term reference pictures long-term reference entries
  • the alignment of the long-term reference pictures is arranged in ascending order from the long-term reference picture having the smallest long-term reference picture number to the long-term reference picture having the largest long-term reference picture number.
  • L1 (RefPicList1) may be used.
  • temporal_ID temporal ID indicating a temporal level is equal to or less than the temporal ID of the current picture.
  • entryShortTerm For a particular entryShortTerm, if the POC of entryShortTerm is greater than the POC of the current picture, the entryShortTerm value is placed on L1 in ascending order of POC. In other words, among the pictures marked to be used as the short-term reference picture, pictures having a POC value larger than the POC of the current picture are located in ascending order of the POC from the beginning of L1.
  • the long term reference pictures for the L1 list may then be sorted.
  • long-term reference pictures long-term reference entries
  • the alignment of the long-term reference pictures is arranged in ascending order from the long-term reference picture having the smallest long-term reference picture number to the long-term reference picture having the largest long-term reference picture number.
  • the short-term reference picture may be specified by the POC. Therefore, as described above, the picture number specifying the short-term reference picture may be a POC. In the case of a long-term reference picture, the long-term reference picture may be specified by POC or Least Significant Bits (LSB) of the POC. Thus, the long term reference picture number specifying the long term reference picture may be a POC or an LSB of the POC.
  • LSB Least Significant Bits
  • a selection stage is performed.
  • pictures that can be used for inter prediction of the current picture are selected from the sorted pictures.
  • N pictures are selected from the beginning in the reference picture lists L0 and L1 to be used in the sort order.
  • an N value indicating the number of selected pictures may be determined based on information transmitted from the encoding apparatus.
  • the decoding apparatus may use the number N of reference pictures indicated by the received num_ref_idx_lX_default_active_minus1 as a default value in the current sequence.
  • the decoding apparatus may apply the N value indicated by the received num_ref_idx_l1_active_minus1 as the number of reference pictures for the current picture or the current slice.
  • the number information of the transmitted reference pictures for example, num_ref_idx_lX_default_active_minus1 or num_ref_idx_lX_active_minus1 may indicate the number of all reference pictures or may indicate only the number of short-term reference pictures.
  • the encoding apparatus indicates that long-term reference pictures are used as reference pictures for each long-term reference picture together with information indicating whether long-term reference pictures are used as reference pictures in the current picture. Can be transmitted.
  • the size of the quantization parameter may be considered in order to increase the accuracy of inter prediction.
  • Quantization divides the components transformed into DCT and / or DST and the like into quantization steps and approximates the result to a representative value.
  • inverse quantization the quantized value is multiplied by the quantization step and returned to the transform component.
  • the quantization step is not directly encoded, but a quantization parameter (QP) is referred to as 'QP' for convenience of description, and a quantization step is derived from the QP. If the QP is small, the signal can be encoded / decoded more accurately, but the amount of information to be processed and the amount of information to be transmitted increase.
  • QP quantization parameter
  • Quantization Parameter Initializing reference picture list based on (QP)
  • the initialization of the reference picture list for the current picture includes a sorting stage and a selection stage.
  • the entryShortTerm value is placed on the L0 in descending order of the POC.
  • pictures marked as being used as a short-term reference picture pictures having a POC value smaller than the POC of the current picture are located in descending order of the POC from the beginning of L0.
  • the long-term reference pictures for the L0 list may then be sorted.
  • long-term reference pictures long-term reference entries
  • the alignment of the long-term reference pictures is arranged in ascending order from the long-term reference picture having the smallest long-term reference picture number to the long-term reference picture having the largest long-term reference picture number.
  • L1 (RefPicList1) may be used.
  • temporal_ID temporal ID indicating a temporal level is equal to or less than the temporal ID of the current picture.
  • entryShortTerm For a particular entryShortTerm, if the POC of entryShortTerm is greater than the POC of the current picture, the entryShortTerm value is placed on L1 in ascending order of POC. In other words, among the pictures marked to be used as the short-term reference picture, pictures having a POC value larger than the POC of the current picture are located in ascending order of the POC from the beginning of L1.
  • the long term reference pictures for the L1 list may then be sorted.
  • long-term reference pictures long-term reference entries
  • the alignment of the long-term reference pictures is arranged in ascending order from the long-term reference picture having the smallest long-term reference picture number to the long-term reference picture having the largest long-term reference picture number.
  • the encoding apparatus or the decoding apparatus may select, among the aligned reference pictures, pictures having the same QP and QP of the current picture or smaller QP than the QP of the current picture. Between the selected pictures, the posterior relationship between the pictures determined in the alignment step is maintained.
  • pictures having the same QP and QP of the current picture or having a QP smaller than the QP of the current picture are sorted in descending order according to the POC value of each picture.
  • pictures whose QP and QP of the current picture are equal to or smaller than QP of the current picture are sorted in ascending order according to the POC value.
  • the selected pictures are located ahead of the unselected pictures (reference pictures that have a QP greater than the QP of the current picture). For example, selected pictures are assigned a lower reference picture index than pictures that are not selected.
  • non-selected reference pictures may be added after the selected reference picture according to the POC order.
  • the number of reference pictures to be added is equal to the difference (N-M) between the number N of reference pictures to be used and the number M of selected reference pictures.
  • a long-term reference picture information indicating whether a device reference picture is used for inter prediction of the current picture is transmitted, and when a long-term reference picture is used, it is indicated whether the long-term reference picture is referenced in the current picture for each long-term reference picture.
  • the long-term reference picture referenced in the current picture can be added after the selected reference pictures or short-term reference pictures.
  • the long-term reference picture may also be located earlier than the short-term reference picture not selected as the selected picture if a QP value equal to or less than the QP of the current picture is selected as the picture in the selection step.
  • Table 1 shows a syntax structure of a method for performing a selection step based on a QP in initializing a reference picture list.
  • SortedRefPicList represents a list of reference pictures stored in the DPB after the sorting step
  • FinalRefPicList is a final list of reference pictures output as a result of performing reference picture list initialization on the current picture
  • TmpRefPicList is a temporary list of reference pictures.
  • FinalRefPicList and TmpRefPicList are empty at the beginning of the initialization procedure or at the beginning of the selection phase.
  • the size of the quantization parameter may be reflected in the temporal hierarchical structure of the reference pictures.
  • the QP of the reference picture with a low temporal level is smaller than the QP of the reference picture with a high temporal level. Therefore, reference picture list initialization for the current picture may be performed using the temporal IDs of the reference pictures.
  • each picture that is inter predicted may refer to pictures in a forward direction in the case of a P picture, and may refer to pictures in a forward or reverse direction in the case of a B picture.
  • inter prediction may be performed by referring to pictures having the same or lower temporal level.
  • pictures with a temporal level TL of 1 do not refer to pictures with a temporal level 2 (pictures of TL2), but refer to pictures with a temporal level of 1 or 0 (pictures of TL1 or TL0). .
  • temporal level may be less than or greater than three.
  • Temporal ID Temporal ID Reference picture list based on
  • the initialization of the reference picture list for the current picture includes a sorting stage and a selection stage.
  • the entryShortTerm value is placed on the L0 in descending order of the POC.
  • pictures marked as being used as a short-term reference picture pictures having a POC value smaller than the POC of the current picture are located in descending order of the POC from the beginning of L0.
  • the long-term reference pictures for the L0 list may then be sorted.
  • long-term reference pictures long-term reference entries
  • the alignment of the long-term reference pictures is arranged in ascending order from the long-term reference picture having the smallest long-term reference picture number to the long-term reference picture having the largest long-term reference picture number.
  • L1 (RefPicList1) may be used.
  • temporal_ID temporal ID indicating a temporal level is equal to or less than the temporal ID of the current picture.
  • entryShortTerm For a particular entryShortTerm, if the POC of entryShortTerm is greater than the POC of the current picture, the entryShortTerm value is placed on L1 in ascending order of POC. In other words, among the pictures marked to be used as the short-term reference picture, pictures having a POC value larger than the POC of the current picture are located in ascending order of the POC from the beginning of L1.
  • the long term reference pictures for the L1 list may then be sorted.
  • long-term reference pictures long-term reference entries
  • the alignment of the long-term reference pictures is arranged in ascending order from the long-term reference picture having the smallest long-term reference picture number to the long-term reference picture having the largest long-term reference picture number.
  • the encoding apparatus or the decoding apparatus may select, among the aligned reference pictures, pictures having a temporal ID that is equal to or smaller than the temporal ID of the current picture.
  • the temporal ID of the picture specifies the temporal level to which the picture belongs. A picture with a low temporal ID belongs to a low temporal level, and a picture with a high temporal ID belongs to a high temporal level.
  • the posterior relationship between the pictures determined in the alignment step is maintained.
  • pictures having a temporal ID equal to or smaller than the temporal ID of the current picture are sorted in descending order according to the POC value of each picture.
  • pictures having a temporal ID that is less than or equal to the temporal ID of the current picture are sorted in ascending order according to the POC value.
  • the selected pictures are located ahead of the unselected pictures (reference pictures having a temporal ID that is greater than the temporal ID of the current picture). For example, selected pictures are assigned a lower reference picture index than pictures that are not selected.
  • non-selected reference pictures may be added after the selected reference picture according to the POC order.
  • the number of reference pictures to be added is equal to the difference (N-M) between the number N of reference pictures to be used and the number M of selected reference pictures.
  • a long-term reference picture information indicating whether a device reference picture is used for inter prediction of the current picture is transmitted, and when a long-term reference picture is used, it is indicated whether the long-term reference picture is referenced in the current picture for each long-term reference picture.
  • the long-term reference picture referenced in the current picture can be added after the selected reference pictures or short-term reference pictures.
  • the long-term reference picture may be located before the short-term reference picture that is not selected as the selected picture.
  • Table 2 shows a syntax structure of a method for performing a selection step based on a temporal ID in initializing a reference picture list.
  • SortedRefPicList represents a list of reference pictures stored in the DPB after the sorting step
  • FinalRefPicList is a final list of reference pictures output as a result of performing reference picture list initialization on the current picture
  • TmpRefPicList is a temporary list of reference pictures.
  • FinalRefPicList and TmpRefPicList are empty at the beginning of the initialization procedure or at the beginning of the selection phase.
  • FIG. 5 is a diagram schematically illustrating an example of reference picture list initialization according to the present invention.
  • the current picture 500 is a P picture and two reference pictures are selected as reference pictures used in the reference picture list is described as an example.
  • reference 1 refers to a reference relationship in which no QP or temporal level is considered, and reference pictures are finally sorted in the reference picture list according to reference picture order 1.
  • FIG. Reference 2 is a reference relationship in consideration of QP or temporal level, and the reference pictures are finally sorted in the reference picture list according to reference picture order 2.
  • the reference picture lists of L0 for the current picture are arranged and selected as [picture with POC 8, picture with POC 6] by initialization. .
  • the reference picture lists of L0 for the current picture are arranged and selected to be [picture with POC of 8, picture with POC of 4] by initialization.
  • FIG. 6 is a diagram schematically illustrating another example of initialization of a reference picture list according to the present invention.
  • the current picture 600 is a P picture and four reference pictures are selected as a reference picture used in the reference picture list is described as an example.
  • reference 1 is a reference relationship in which QP or temporal level is not considered, and reference pictures are finally sorted in the reference picture list according to reference picture order 1.
  • Reference 2 is a reference relationship in consideration of QP or temporal level, and the reference pictures are finally sorted in the reference picture list according to reference picture order 2.
  • the reference picture lists of L0 for the current picture are initialized by [initializing a picture having a POC of 8, a picture having a POC of 6, a picture having a POC of 4, and a POC by initialization]. Is selected to be zero).
  • the reference picture lists of L0 for the current picture are initialized by [initial picture with POC of 8, picture with POC of 0, picture with POC of 6, POC of 4 In-picture].
  • FIG. 7 is a flowchart schematically illustrating a method of performing initialization of a reference picture list according to the present invention.
  • alignment of reference pictures is performed (S710).
  • the reference pictures are aligned based on the POCs of the reference pictures.
  • the specific sorting procedure performed in the sorting step of reference pictures is the same as described in (1) sorting step of the reference picture list initialization based on QP and the reference picture list initialization based on temporal ID.
  • reference pictures to be used for inter prediction on the current picture are selected based on the QP (S720).
  • QP QP
  • reference pictures having a QP that is equal to or less than the QP of the current picture are selected. The selection may be performed based on the temporal level reflecting the QP.
  • the specific selection procedure performed in the selection step of the reference pictures is the same as described in the (2) selection step of the reference picture list initialization based on the QP and the reference picture list initialization based on the temporal ID.
  • FIG. 8 schematically illustrates an apparatus for performing initialization of a reference picture list according to the present invention.
  • the reference picture list initialization apparatus 800 includes an alignment unit 810 and a selection unit 820.
  • the alignment unit 810 aligns reference pictures based on POCs of pictures based on input reference picture information.
  • the alignment unit 810 may sort the pictures having the smaller POC than the current picture in descending order of the POC, and then sort the pictures having the larger POC than the current picture in ascending order of the POC.
  • the alignment unit 810 may sort the pictures having the larger POC than the current picture in ascending order of the POC, and then sort the pictures having the smaller POC than the current picture in descending order of the POC.
  • the alignment unit 810 Details of operations performed by the alignment unit 810 are the same as described in (1) the alignment step of the reference picture list initialization based on the QP and the reference picture list initialization based on the temporal ID.
  • the selector 820 compares the QPs of the reference pictures with the QP of the current picture, and selects reference pictures having a QP that is equal to or smaller than the QP of the current picture.
  • the selector 820 may select the reference picture based on the temporal level reflecting the QP.
  • the final reference picture list on which the selection is performed by the selection unit 820 may be stored in the DPB for prediction or transferred to the prediction unit to be referred to the prediction.
  • reference picture list initialization is described as being performed in a separate configuration (reference picture list initialization device), this is for convenience of explanation and understanding of the present invention, and the present invention is not limited thereto.
  • initialization of the reference picture list may be performed in a memory of the encoding apparatus and the decoding apparatus described with reference to FIGS. 1 and 2, for example, a DPB.
  • the above-described reference picture list apparatus may be a DPB.
  • the initialization of the reference picture list may be performed by the prediction unit of the encoding apparatus and the decoding apparatus described with reference to FIGS. 1 and 2.
  • the above-described reference picture list initialization apparatus may be a prediction unit.
  • the reference picture list initialization apparatus may be included as separate components in the encoding apparatus and the decoding apparatus.
  • reference pictures are sorted and / or selected in the reference picture list or reference pictures are added to the reference picture list, this is for convenience of description, and information for specifying the reference picture in the reference picture list is aligned and / Or may be interpreted to mean that the information to select or specify the reference picture to the reference picture list is added.

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Abstract

La présente invention concerne un procédé et un appareil d'initialisation d'une liste d'images de référence, le procédé d'initialisation d'une liste d'images de référence selon la présente invention comprenant les étapes consistant à : aligner, pour une prédiction inter de l'image courante, des images de référence sur la base d'un comptage d'ordres d'images (POC) de chaque image de référence ; et sélectionner, parmi les images alignées, des images de référence à utiliser dans la prédiction de l'image courante, les images de référence pouvant être sélectionnées sur la base de paramètres de quantification de celles-ci dans l'étape de sélection.
PCT/KR2012/009052 2011-10-31 2012-10-31 Procédé et appareil d'initialisation d'une liste d'images de référence Ceased WO2013066045A1 (fr)

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