KR20150009468A - A method and an apparatus for encoding/decoding a scalable video signal - Google Patents
A method and an apparatus for encoding/decoding a scalable video signal Download PDFInfo
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- KR20150009468A KR20150009468A KR1020140089107A KR20140089107A KR20150009468A KR 20150009468 A KR20150009468 A KR 20150009468A KR 1020140089107 A KR1020140089107 A KR 1020140089107A KR 20140089107 A KR20140089107 A KR 20140089107A KR 20150009468 A KR20150009468 A KR 20150009468A
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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
- H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
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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
- H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
- H04N19/51—Motion estimation or motion compensation
- H04N19/573—Motion compensation with multiple frame prediction using two or more reference frames in a given prediction direction
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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
- H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
- H04N19/51—Motion estimation or motion compensation
- H04N19/58—Motion compensation with long-term prediction, i.e. the reference frame for a current frame not being the temporally closest one
Abstract
Description
The present invention relates to a scalable video signal encoding / decoding method and apparatus.
Recently, the demand for high resolution and high quality images such as high definition (HD) image and ultra high definition (UHD) image is increasing in various applications. As the image data has high resolution and high quality, the amount of data increases relative to the existing image data. Therefore, when the image data is transmitted using a medium such as a wired / wireless broadband line or stored using an existing storage medium, The storage cost is increased. High-efficiency image compression techniques can be utilized to solve such problems as image data becomes high-resolution and high-quality.
An inter picture prediction technique for predicting a pixel value included in a current picture from a previous or a subsequent picture of a current picture by an image compression technique, an intra picture prediction technique for predicting a pixel value included in a current picture using pixel information in the current picture, There are various techniques such as an entropy encoding technique in which a short code is assigned to a value having a high appearance frequency and a long code is assigned to a value having a low appearance frequency. Image data can be effectively compressed and transmitted or stored using such an image compression technique.
On the other hand, demand for high-resolution images is increasing, and demand for stereoscopic image content as a new image service is also increasing. Video compression techniques are being discussed to effectively provide high resolution and ultra-high resolution stereoscopic content.
It is an object of the present invention to provide a method and apparatus for up-sampling a picture of a reference layer in encoding / decoding a scalable video signal.
An object of the present invention is to provide a method and apparatus for constructing a reference picture list using an interlayer reference picture in encoding / decoding a scalable video signal.
An object of the present invention is to provide a method and apparatus for effectively deriving texture information of a current layer through inter-layer prediction in encoding / decoding a scalable video signal.
A scalable video signal decoding method and apparatus according to the present invention decodes a corresponding picture of a reference layer corresponding to a current picture of a current layer, upsamples the decoded corresponding picture to generate an interlayer reference picture, A reference picture list including a layer reference picture is generated, and inter-layer prediction of the current block is performed based on the reference picture list.
The reference picture list according to the present invention is configured in the order of a near reference picture, a long distance reference picture, and an inter-layer reference picture having an output order different from the current picture.
The inter-layer reference picture according to the present invention includes at least one of a first inter-layer reference picture and a second inter-layer reference picture, wherein the first inter-layer reference picture indicates a reference picture subjected to filtering on the integer position And the second interlayer reference picture is a reference picture that has not been subjected to filtering on the integer position.
The scalable video signal decoding method and apparatus according to the present invention may further comprise a decoding step of decoding the first interlayer reference picture and the second interlayer reference picture according to a predetermined priority order between the first interlayer reference picture and the second interlayer reference picture, And a reference picture is added to the reference picture list.
A scalable video signal encoding method and apparatus according to the present invention decodes a corresponding picture of a reference layer corresponding to a current picture of a current layer, upsamples the decoded corresponding picture to generate an interlayer reference picture, A reference picture list including a layer reference picture is generated, and inter-layer prediction of the current block is performed based on the reference picture list.
The reference picture list according to the present invention is configured in the order of a near reference picture, a long distance reference picture, and an inter-layer reference picture having an output order different from the current picture.
The inter-layer reference picture according to the present invention includes at least one of a first inter-layer reference picture and a second inter-layer reference picture, wherein the first inter-layer reference picture indicates a reference picture subjected to filtering on the integer position And the second interlayer reference picture is a reference picture that has not been subjected to filtering on the integer position.
A scalable video signal encoding method and apparatus according to the present invention are characterized by including a first interlayer reference picture and a second interlayer reference picture according to a predetermined priority order between the first interlayer reference picture and the second interlayer reference picture, And a reference picture is added to the reference picture list.
According to the present invention, a picture of a reference layer can be effectively upsampled.
According to the present invention, it is possible to effectively construct a reference picture list including an interlayer reference picture.
According to the present invention, texture information of a current layer can be effectively guided through inter-layer prediction.
1 is a block diagram schematically illustrating an encoding apparatus according to an embodiment of the present invention.
2 is a block diagram schematically illustrating a decoding apparatus according to an embodiment of the present invention.
FIG. 3 is a flowchart illustrating a process of inter-layer prediction of a current layer using a corresponding picture of a reference layer according to an embodiment of the present invention.
4 is a flowchart illustrating a method of upsampling a corresponding picture of a reference layer according to an embodiment of the present invention.
FIG. 5 illustrates a method of constructing a reference picture list in consideration of a pre-defined priority between inter-layer reference pictures, according to an embodiment of the present invention. Referring to FIG.
FIG. 6 illustrates a method of adding an interlayer reference picture to a reference picture list in consideration of a slice type, according to an embodiment of the present invention.
FIG. 7 illustrates a method of adding an interlayer reference picture to a reference picture list in consideration of the number of reference pictures between reference picture lists, according to an embodiment to which the present invention is applied.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.
When an element is referred to herein as being "connected" or "connected" to another element, it may mean directly connected or connected to the other element, Element may be present. In addition, the content of " including " a specific configuration in this specification does not exclude a configuration other than the configuration, and means that additional configurations can be included in the scope of the present invention or the scope of the present invention.
The terms first, second, etc. may be used to describe various configurations, but the configurations are not limited by the term. The terms are used for the purpose of distinguishing one configuration from another. For example, without departing from the scope of the present invention, the first configuration may be referred to as the second configuration, and similarly, the second configuration may be named as the first configuration.
In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that the components are composed of separate hardware or software constituent units. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of each constituent unit may form one constituent unit or one constituent unit may be divided into a plurality of constituent units to perform a function. The integrated embodiments and the separate embodiments of each component are also included in the scope of the present invention unless they depart from the essence of the present invention.
In addition, some of the components are not essential components to perform essential functions in the present invention, but may be optional components only to improve performance. The present invention can be implemented only with components essential for realizing the essence of the present invention, except for the components used for the performance improvement, and can be implemented by only including the essential components except the optional components used for performance improvement Are also included in the scope of the present invention.
The coding and decoding of video supporting a plurality of layers (multi-layers) in a bitstream is referred to as scalable video coding. Since there is a strong correlation between a plurality of layers, it is possible to remove redundant elements of data and improve the coding performance of an image by performing prediction using such a relation. Hereinafter, prediction of the current layer using information of another layer is referred to as inter-layer prediction or inter-layer prediction.
The plurality of layers may have different resolutions, where the resolution may refer to at least one of spatial resolution, temporal resolution, and image quality. Resampling such as up-sampling or down-sampling of a layer may be performed to adjust the resolution in the inter-layer prediction.
1 is a block diagram schematically illustrating an encoding apparatus according to an embodiment of the present invention.
The
The upper layer may be represented by a current layer or an enhancement layer and the lower layer may be represented by an enhancement layer, a base layer, or a reference layer having a resolution lower than that of the upper layer . The upper layer and the lower layer may have different spatial resolution, temporal resolution according to the frame rate, and image quality depending on the color format or the quantization size. Upsampling or downsampling of a layer may be performed when a resolution change is required to perform inter-layer prediction.
The
The lower
The encoding unit may be implemented by the image encoding method described in the embodiments of the present invention, but operations in some components may not be performed for lowering the complexity of the encoding apparatus or for fast real-time encoding. For example, in performing intra-picture prediction in the prediction unit, it is not necessary to use a method of selecting an optimal intra-picture coding method using all the intra-picture prediction mode methods in order to perform coding in real time, The intra-picture prediction mode may be used as the final intra-picture prediction mode. As another example, it is also possible to restrictively use the type of the prediction block used in intra-picture prediction or inter-picture prediction.
The unit of the block processed by the encoding apparatus may be a coding unit for performing encoding, a prediction unit for performing prediction, and a conversion unit for performing conversion. The coding unit can be expressed by CU (Coding Unit), the prediction unit by PU (Prediction Unit), and the conversion unit by TU (Transform Unit).
In the
The prediction block may be a unit for performing prediction such as intra-picture prediction or inter-picture prediction. The block for intra prediction may be a square block such as 2Nx2N, NxN. As a block for performing inter picture prediction, there is a prediction block dividing method using AMP (Asymmetric Motion Partitioning), which is a square shape such as 2Nx2N or NxN or a rectangular shape or an asymmetric shape such as 2NxN and Nx2N. The method of performing the transform in the transform unit 115 may vary depending on the type of the prediction block.
The
The
When the PCM (Pulse Coded Modulation) coding mode is used, it is also possible to directly encode the original block and transmit it to the decoding unit without performing the prediction through the
The prediction block may include a plurality of transform blocks. When intra prediction is performed, if the size of the prediction block and the size of the transform block are the same, a pixel existing on the left side of the prediction block, In-picture prediction for the prediction block based on the pixels existing in the prediction block. However, when intra prediction is performed, when the size of the prediction block is different from the size of the transform block, when a plurality of transform blocks are included in the prediction block, the intra-picture prediction is performed using the neighboring pixels adjacent to the transform block as reference pixels. Can be performed. Here, the neighboring pixels adjacent to the transform block may include at least one of neighboring pixels adjacent to the prediction block and pixels already decoded in the prediction block.
The intra-picture prediction method can generate a prediction block after applying a mode dependent intra-smoothing (MDIS) filter to the reference picture according to the intra-picture prediction mode. The type of MDIS filter applied to the reference pixel may be different. The MDIS filter can be used to reduce residuals in intra-frame predicted blocks generated after performing intra-prediction and applied to reference pixels and prediction as additional filters applied to intra-frame predicted blocks. In performing MDIS filtering, the filtering of the reference pixel and some columns included in the intra prediction block can perform filtering according to the direction of the intra prediction mode.
The
In the reference picture interpolating unit, the reference picture information is supplied from the
The
As the inter-picture prediction method, various methods such as a skip method, a merge method, and a method using a motion vector predictor (MVP) can be used.
In the inter-picture prediction, information such as motion information, such as reference indices, motion vectors, and residual signals, is entropy-encoded and transmitted to the decoding unit. When the skip mode is applied, a residual signal is not generated, so that the conversion and quantization process for the residual signal may be omitted.
The
Inter-layer prediction can predict a current block of an upper layer using motion information on a picture of a lower layer (reference layer) using a picture of a lower layer as a reference picture. A picture of a reference layer used as a reference picture in inter-layer prediction may be a picture sampled according to the resolution of the current layer. In addition, the motion information may include a motion vector and a reference index. At this time, the value of the motion vector for the picture of the reference layer can be set to (0, 0).
As an example of inter-layer prediction, a prediction method of using a picture of a lower layer as a reference picture has been described, but the present invention is not limited to this. The
Inter-layer texture prediction can derive the texture of the current layer based on the texture of the reference layer. The texture of the reference layer can be sampled according to the resolution of the current layer, and the
The inter-layer motion prediction can derive the motion vector of the current layer based on the motion vector of the reference layer. At this time, the motion vector of the reference layer can be scaled according to the resolution of the current layer. In the inter-layer syntax prediction, the syntax of the current layer can be predicted based on the syntax of the reference layer. For example, the
A residual block including residue information which is a difference value between the prediction blocks generated by the
The transforming
The
The
The
The
The
The
The
The deblocking filter can remove block distortion caused by the boundary between the blocks in the reconstructed picture. It may be determined whether to apply a deblocking filter to the current block based on pixels included in a few columns or rows included in the block to determine whether to perform deblocking. When a deblocking filter is applied to a block, a strong filter or a weak filter may be applied according to the deblocking filtering strength required. In applying the deblocking filter, horizontal filtering and vertical filtering may be performed concurrently when vertical filtering and horizontal filtering are performed.
The offset correction unit may correct the offset of the deblocked image with respect to the original image in units of pixels. In order to perform offset correction for a specific picture, pixels included in an image are divided into a predetermined area, and then an area to be offset is determined, and an offset is applied to the area, or an offset is applied considering edge information of each pixel Can be used.
The
The
The information output from the
The
2 is a block diagram schematically illustrating a decoding apparatus according to an embodiment of the present invention.
As shown in FIG. 2, the
The
The lower layer decoding unit 200b includes an
When a bitstream including a plurality of layers is transmitted from the encoding apparatus, the
The
As with the
The
The
The
The
The
The
The prediction unit determination unit receives various information such as prediction unit information input from the entropy decoding unit, prediction mode information of the intra prediction method, motion prediction related information of the inter picture prediction method, and separates prediction blocks in the current coding block. It is possible to determine whether the inter-picture prediction is performed or the intra-picture prediction is performed.
The inter-picture prediction unit uses the information necessary for the inter-picture prediction of the current prediction block provided by the coding apparatus to predict the current picture based on the information included in at least one of the previous picture of the current picture or the following picture The inter-picture prediction can be performed. In order to perform inter-picture prediction, a motion prediction method of a prediction block included in a coded block based on a coded block is classified into a skip mode, a merge mode, a mode using an MVP (motion vector predictor) Mode) can be determined.
The intra prediction unit can generate a prediction block based on the reconstructed pixel information in the current picture. If the prediction block is a prediction block in which intra prediction is performed, intra prediction can be performed based on intra prediction mode information of the prediction block provided by the encoder. The intra-picture prediction unit includes an MDIS filter that performs filtering on the reference pixels of the current block, a reference pixel interpolator that interpolates reference pixels to generate reference pixels of a pixel unit less than an integer value, Lt; RTI ID = 0.0 > DCF < / RTI >
The predicting
The inter-layer prediction unit may perform inter-layer prediction using intra-picture prediction mode information, motion information, and the like.
Inter-layer prediction can predict a current block of an upper layer using motion information on a lower layer (reference layer) picture using a picture of a lower layer as a reference picture.
A picture of a reference layer used as a reference picture in inter-layer prediction may be a picture sampled according to the resolution of the current layer. In addition, the motion information may include a motion vector and a reference index. At this time, the value of the motion vector for the picture of the reference layer can be set to (0, 0).
As an example of inter-layer prediction, a prediction method of using a picture of a lower layer as a reference picture has been described, but the present invention is not limited to this. The
Inter-layer texture prediction can derive the texture of the current layer based on the texture of the reference layer. The texture of the reference layer can be sampled to the resolution of the current layer, and the inter-layer prediction unit can predict the texture of the current layer based on the sampled texture. The inter-layer motion prediction can derive the motion vector of the current layer based on the motion vector of the reference layer. At this time, the motion vector of the reference layer can be scaled according to the resolution of the current layer. In the inter-layer syntax prediction, the syntax of the current layer can be predicted based on the syntax of the reference layer. For example, the
The reconstructed block or picture may be provided to the
Information on whether or not a deblocking filter has been applied to the block or picture from the encoding device and information on whether a strong filter or a weak filter is applied can be provided when the deblocking filter is applied. In the deblocking filter of the decoding apparatus, the deblocking filter related information provided by the encoding apparatus is provided, and the decoding apparatus can perform deblocking filtering on the corresponding block.
The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction applied to the image and the offset value information during encoding.
The
The encoding apparatus and the decoding apparatus can perform encoding on three or more layers instead of two layers. In this case, the encoding unit for the upper layer and the decoding unit for the upper layer are provided in a plurality corresponding to the number of the upper layers .
In SVC (Scalable Video Coding) which supports multi-layer structure, there is a relation between layers. By using this association, prediction can be performed to remove redundant elements of data and enhance the image coding performance.
Therefore, in the case of predicting a picture (video) of a current layer (enhancement layer) to be encoded / decoded, not only inter prediction or intra prediction using information of the current layer but also interlayer prediction using information of another layer can be performed .
In performing inter-layer prediction, the current layer may generate a prediction sample of a current layer using a decoded picture of a reference layer used for inter-layer prediction as a reference picture.
At this time, since at least one of the spatial resolution, the temporal resolution, and the image quality may be different between the current layer and the reference layer (i.e., due to the inter-layer scalability difference), the picture of the decoded reference layer, After resampling is performed, it can be used as a reference picture for interlayer prediction of the current layer. Resampling means up-sampling or down-sampling of the samples of the reference layer picture in accordance with the picture size of the current layer.
In this specification, a current layer refers to a layer on which encoding or decoding is currently performed, and may be an enhancement layer or an upper layer. A reference layer is a layer that the current layer refers to for interlayer prediction, and can be a base layer or a lower layer. A picture of a reference layer (i.e., a reference picture) used for inter-layer prediction of the current layer may be referred to as an inter-layer reference picture or a reference picture between layers.
FIG. 3 is a flowchart illustrating a process of inter-layer prediction of a current layer using a corresponding picture of a reference layer according to an embodiment of the present invention.
Referring to FIG. 3, the corresponding picture of the reference layer corresponding to the current picture of the current layer can be restored (S300).
The reference layer may refer to a base layer or other enhancement layer having a lower resolution than the current layer. The corresponding picture may mean a picture located in the same time zone as the current picture of the current layer.
For example, the corresponding picture may be a picture having picture order count (POC) information that is the same as the current picture of the current layer. The corresponding picture may belong to the same access unit (AU) as the current picture of the current layer. The corresponding picture may have the same temporal level identifier (TemporalID) as the current picture of the current layer. Here, the time level identifier may mean an identifier for specifying each of a plurality of scalably coded layers according to a temporal resolution.
In step S310, the reconstructed corresponding picture is up-sampled to generate an inter-layer reference picture (S310).
Here, the interlayer reference picture can be used as a reference picture for intra-layer prediction of the current picture. The current picture of the current layer may use one inter-layer reference picture or a plurality of inter-layer reference pictures. For example, the interlayer reference picture may include at least one of a first interlayer reference picture and a second interlayer reference picture. The first interlayer reference picture indicates a reference picture that has been subjected to filtering for an integer position and the second interlayer reference picture may refer to a reference picture that has not been filtered for an integer position. The integer position can refer to a pixel in integer units of the corresponding picture to be upsampled. Alternatively, in an upsampling process, when interpolation is performed in units of integer pixels or less, that is, 1 / n pixels, n phases are generated, and at this time, ). A specific upsampling method will be described with reference to FIG.
A reference picture list including the inter-layer reference pictures generated in step S310 may be generated (S320).
First, the reference picture list for the current picture may include a reference picture belonging to the same layer as the current picture (hereinafter referred to as a temporal reference picture).
The temporal reference picture refers to a picture having an output order (for example, picture order count, POC) different from the current picture, which can be stored in the decoding picture buffer (DPB). The temporal reference picture stored in the decoding picture buffer may be composed of a short-term reference picture and a long-term reference picture. The near reference picture means a picture in which the difference between the current picture and the POC value is not large and the long distance reference picture can mean a picture in which the difference between the current picture and the POC value is large.
The information indicating the near reference picture to be stored in the decoding picture buffer at the present time is composed of the output order (POC) of the reference picture and a flag (used_by_curr_pic_s0_flag) indicating whether the reference picture is directly referred to in the current picture. reference picture set). (For example, unsed for reference) that the picture not shown in the reference picture set for the current picture is not used as a reference picture, and may be removed from the decoding picture buffer.
In the case of the long-distance reference picture, since the difference between the current picture and the POC value is large, it can be expressed using the least significant bit (LSB) and the most significant bit (MSB) of the POC value. For example, if the POC value of a specific picture is 331 and the maximum value that can be represented by LSB is 32, 331 can be expressed as 32 * 10 + 11, where 10 is the MSB value and 11 is the LSB value .
In the case of the long-distance reference picture, the POC value of the reference picture can be derived by using the difference between the LSB value of the POC value of the reference picture and the MSB of the POC value of the current picture and the MSB of the POC value of the reference picture.
In generating the reference picture list including temporal reference pictures, it is possible to consider whether the temporal reference picture is a near reference picture and the POC value of the near reference picture. Here, the reference picture list may include at least one of a
For example, in the
In the
On the other hand, when the current picture performs inter-layer prediction, the reference picture list may further include an inter-layer reference picture. That is, in a multi-layer structure (for example, scalable video coding and multi-view video coding), not only reference pictures of the same layer but also reference pictures of other layers can be used as reference pictures of the enhancement layer.
Specifically, a picture belonging to the reference layer can be used as a reference picture. The reference layer can be identified by a reference layer identifier (RefPiclayerId) of the slice header. Here, the reference layer identifier can be derived based on the syntax of the slice header, inter_layer_pred_layer_idc (hereinafter referred to as an interlayer indicator). The interlayer indicator may indicate the layer of the picture used by the current picture for inter-layer prediction.
When an interlayer reference picture is further added to the reference picture list, the reference picture list can be composed of a near reference picture and a long distance reference picture, and an interlayer reference picture can be added at the end of the reference picture. In this case, the near reference picture may be arranged in the near reference picture having the POC value smaller than the POC value of the current picture, and the near reference picture having the POC value larger than the POC value of the current picture.
Alternatively, an interlayer reference picture may be added between temporal reference pictures. For example, it may be arranged after the first temporal reference picture in the reference picture list composed of temporal reference pictures. The first temporal reference picture in the reference picture list may refer to a reference picture having a
Further, the positions between the reference pictures may be additionally rearranged to improve the coding efficiency of the reference indices assigned to the reference picture list.
Meanwhile, as described in step S310, the interlayer reference picture may include at least one of a first interlayer reference picture and a second interlayer reference picture. Therefore, it is possible to generate a reference picture list including any one of the first interlayer reference picture and the second interlayer reference picture, and generate a reference picture list including both the first interlayer reference picture and the second interlayer reference picture And this will be described in detail with reference to FIGS. 5 to 7. FIG.
In order to selectively use the first interlayer reference picture and the second interlayer reference picture, both the first interlayer reference picture and the second interlayer reference picture are used in units of pictures, Can be selected. Furthermore, when either one of the first interlayer reference picture and the second interlayer reference picture is selected and used, it is possible to select which of the two interlayer reference pictures to use. To do this, the encoder can signal information about which of the two interlayer reference pictures to use.
Alternatively, a reference index may be used for the selective use. Specifically, only the first inter-layer reference picture may be selected by the reference index in units of prediction blocks, or only the second inter-layer reference picture may be selected, and both the first and second inter- .
On the other hand, when an interlayer reference picture is added to the reference picture list, it is necessary to change the number of reference pictures arranged in the reference picture list or the range of the number of reference indices allocated for each reference picture.
Here, it is assumed that the range of the num_ref_idx_l0_active_minus1 and num_ref_idx_l1_active_minus1 syntaxes of the slice header indicating the reference index maximum value of the reference picture list for the base layer has a value between 0 and 14.
In the case of using either the first interlayer reference picture or the second interlayer reference picture, the range of the num_ref_idx_l0_active_minus1 and the num_ref_idx_l1_active_minus1 syntaxes indicating the maximum value of the reference index of the reference picture list for the current layer is a value between 0 and 15 Can be defined. Alternatively, even when both the first interlayer reference picture and the second interlayer reference picture are used, when two interlayer reference pictures are added to different reference picture lists, the range of num_ref_idx_l0_active_minus1 and num_ref_idx_l1_active_minus1 is a value between 0 and 15 Can be defined.
For example, when the number of temporal reference pictures in the reference picture list L0 is 15, 16 total reference pictures exist when the first or second interlaced reference pictures are added to the reference picture list, and the value of num_ref_idx_l0_active_minus1 is 15 do.
Alternatively, when both the first interlayer reference picture and the second interlayer reference picture are used and two interlayer reference pictures are added to the same reference picture list, the reference index maximum value of the reference picture list for the current layer The range of the num_ref_idx_l0_active_minus1 and the num_ref_idx_l1_active_minus1 syntaxes may be defined as a value between 0 and 16.
For example, if the number of temporal reference pictures in the reference picture list L0 is 15, and a first interlaced reference picture and a second interlaced reference picture are added to the reference picture list L0, a total of 17 reference pictures exist, and num_ref_idx_l0_active_minus1 The value is 16.
The inter-layer prediction of the current block may be performed based on the reference picture list generated in step S320 (S330).
Specifically, the reference picture corresponding to the reference index of the current block is selected from the reference picture list. The selected reference picture may be a temporal reference picture in the same layer as the current block or an up-sampled inter-layer reference picture from a corresponding picture of the reference layer.
The reference block in the reference picture is specified based on the motion vector of the current block and the reconstructed sample value or texture information of the specified reference block is used to predict the sample value or the texture information of the current block. In this case, if the reference picture corresponding to the reference index of the current block is an interlayer reference picture, the reference block may be a block at the same position as the current block. To this end, if the reference picture of the current block is an interlayer reference picture, the motion vector of the current block may be set to (0, 0).
4 is a flowchart illustrating a method of upsampling a corresponding picture of a reference layer according to an embodiment of the present invention.
Referring to FIG. 4, a reference sample position of a reference layer corresponding to a current sample position of a current layer may be derived (S400).
Since the resolutions of the current layer and the reference layer may be different, a reference sample position corresponding to the current sample position can be derived taking into account the difference in resolution between them. That is, the aspect ratio between the picture of the current layer and the picture of the reference layer can be considered. In addition, since the upsampled picture of the reference layer may not coincide with the picture of the current layer, an offset for correcting the upsampled picture may be required.
For example, the reference sample position may be derived taking into account the scale factor and the upsampled reference layer offset.
Here, the scale factor can be calculated based on the ratio of the width and the height between the current picture of the current layer and the corresponding picture of the reference layer.
The upsampled reference layer offset may mean position difference information between any one of the samples located at the edge of the current picture and one of the samples located at the edge of the interlayer reference picture. For example, the upsampled reference layer offset includes positional difference information in the horizontal / vertical direction between the upper left sample of the current picture and the upper left sample of the interlayer reference picture, and the difference information between the lower right sample of the current picture and the lower right sample Directional horizontal / vertical directional difference information.
The upsampled reference layer offset may be obtained from the bitstream. For example, the upsampled reference layer offset may be obtained from at least one of a Video Parameter Set, a Sequence Parameter Set, a Picture Parameter Set, and a Slice Header .
The filter coefficient of the up-sampling filter may be determined considering the phase of the reference sample position derived in step S400 (S410).
Here, the up-sampling filter may use either a fixed up-sampling filter or an adaptive up-sampling filter.
1. Fixed Upsampling Filter
The fixed up-sampling filter may refer to an up-sampling filter having a predetermined filter coefficient without considering the characteristics of the image. A tap filter can be used as the fixed up-sampling filter, which can be defined for the luminance component and the chrominance component, respectively. A fixed up-sampling filter having an accuracy of 1/16 sample units will be described with reference to Tables 1 to 2 below.
Table 1 is a table defining the filter coefficients of the fixed up-sampling filter with respect to the luminance component.
As shown in Table 1, in the case of upsampling on the luminance component, an 8-tap filter is applied. That is, interpolation can be performed using a reference sample of the reference layer corresponding to the current sample of the current layer and a neighboring sample adjacent to the reference sample. Here, the neighbor samples can be specified according to the direction in which the interpolation is performed. For example, when interpolation is performed in the horizontal direction, the neighboring sample may include three consecutive samples to the left and four consecutive samples to the right based on the reference sample. Alternatively, when interpolation is performed in the vertical direction, the neighboring sample may include three consecutive samples at the top and four consecutive samples at the bottom based on the reference sample.
Since interpolation is performed with an accuracy of 1/16 sample units, there are a total of 16 phases. This is to support resolution of various magnifications such as 2 times and 1.5 times.
In addition, the fixed up-sampling filter may use different filter coefficients for each phase (p). The size of each filter coefficient may be defined to fall within a range of 0 to 63, except when the phase p is zero. This means that the filtering is performed with a precision of 6 bits. Here, the phase (p) of 0 means the position of an integer multiple of n when interpolation is performed in 1 / n sample units.
Table 2 defines the filter coefficients of the fixed up-sampling filter for the chrominance components.
As shown in Table 2, in case of up-sampling for the chrominance components, a 4-tap filter can be applied unlike the luminance component. That is, interpolation can be performed using a reference sample of the reference layer corresponding to the current sample of the current layer and a neighboring sample adjacent to the reference sample. Here, the neighbor samples can be specified according to the direction in which the interpolation is performed. For example, when interpolation is performed in the horizontal direction, the neighboring sample may include one continuous sample to the left and two consecutive samples to the right based on the reference sample. Alternatively, when interpolation is performed in the vertical direction, the neighboring sample may include one continuous sample at the top and two consecutive samples at the bottom based on the reference sample.
On the other hand, as in the case of the luminance component, since interpolation is performed with an accuracy of 1/16 sample units, there are a total of 16 phases, and different filter coefficients can be used for each phase (p). And, the size of each filter coefficient can be defined to fall in the range of 0 to 62, except when the phase (p) is zero. This also means that filtering is performed with a precision of 6 bits.
The 8-tap filter is applied to the luminance component and the 4-tap filter is applied to the chrominance component. However, the present invention is not limited to this, and the order of the tap filter may be variably determined in consideration of the coding efficiency Of course it is.
2. Adaptive up-sampling filter
It is possible to determine the optimum filter coefficient in the encoder considering the feature of the image without using the fixed filter coefficient, signaling it to the decoder, and transmit it to the decoder. It is the adaptive up-sampling filter that uses adaptively determined filter coefficients in the encoder. Since the characteristics of the image are different in picture units, it is possible to improve the coding efficiency by using an adaptive up-sampling filter capable of expressing characteristics of the image better than using a fixed up-sampling filter in all cases.
The inter-layer reference picture may be generated by applying the filter coefficient determined in step S410 to the corresponding picture of the reference layer (S420).
Specifically, the filter coefficient of the determined up-sampling filter may be applied to the samples of the corresponding picture to perform interpolation. Here, the interpolation may be performed primarily in the horizontal direction and may be performed in the vertical direction with respect to the sample generated after the interpolation in the horizontal direction.
When an interlayer reference picture is added to the reference picture list, a picture order count (POC) can be assigned to the interlayer reference picture. In this case, since both the first interlaced reference picture subjected to the filtering for the intra-position and the second inter-layer reference picture for which the filtering is not performed on the integer position have the same POC as the current picture of the current layer, There may be two POC values in the list that are the same as the current picture. Therefore, a method for distinguishing two interlayer reference pictures having the same POC value from each other is required. Hereinafter, the present invention will be described in detail with reference to FIG. 5 through FIG.
FIG. 5 illustrates a method of constructing a reference picture list in consideration of a pre-defined priority between inter-layer reference pictures, according to an embodiment of the present invention. Referring to FIG.
The present method can be applied when the slice of the current layer is a P slice and both the first interlayer reference picture and the second interlayer reference picture are used. Alternatively, the present method can be applied even when the slice of the current layer is a B slice or a first interlayer reference picture and a second interlayer reference picture are added to the same reference picture list (for example, the list L0 or the list L1) have.
FIG. 5A shows a case where the first inter-layer reference picture is pre-defined as having a higher priority than the second inter-layer reference picture on the reference picture list. Here, the priority may mean that the first interlayer reference picture in the reference picture list has a reference index smaller than the second interlayer reference picture.
5A, after a near reference picture and a long distance reference picture are added to a reference picture list, a first interlayer reference picture subjected to filtering for an integer position is added, and a first interlayer reference picture And then add a second interlayer reference picture that has not been filtered for the integer position.
In this manner, when there are two inter-layer reference pictures having the same POC value as the current picture in the reference picture list, the inter-layer reference pictures having the priority according to the pre-defined priority are filtered for the intra-position A first inter-layer reference picture can be displayed. Alternatively, an inter-layer reference picture having a relatively small reference index among the two inter-layer reference pictures having the same POC value may represent the first inter-layer reference picture. Conversely, an interlayer reference picture with a subordinate or a relatively large reference index in the reference picture list will represent a second interlayer reference picture.
5B shows a case in which it is assumed that the second interlayer reference picture has priority over the reference picture list over the first interlayer reference picture.
Referring to FIG. 5B, after a reference picture having a different POC from the current picture, i.e., a near reference picture and a long distance reference picture, is added, a second interlayer reference picture And add a first interlayer reference picture obtained by performing filtering on the intra position after the second inter-layer reference picture.
In other words, when there are two inter-layer reference pictures having the same POC value as the current picture in the reference picture list, the inter-layer reference pictures having the priority according to the pre-defined priority are filtered for the intra-position It is possible to display the second interlayer reference picture which is not included in the second interlayer reference picture. Alternatively, an inter-layer reference picture having a relatively small reference index among two inter-layer reference pictures having the same POC value may represent a second inter-layer reference picture. Conversely, an interlayer reference picture with a subordinate or a relatively large reference index in the reference picture list will represent the first interlayer reference picture.
5A or 5B, when the priority inter-layer reference picture is added to the reference picture list, the number of reference pictures in the reference picture list becomes the maximum of the reference pictures that can be included in the reference picture list If it is equal to the number, a subordinate interlayer reference picture may not be added.
Referring to FIG. 5C, after a near reference picture is added to the reference picture list, a first interlayer reference picture subjected to filtering on the intra position is added, and after the first interlayer reference picture, A second interlayer reference picture that has not been subjected to filtering for the low position can be added. Then, a long-term reference picture may be added after the second inter-layer reference picture.
In this case as well, if there are two inter-layer reference pictures having the same POC value as the current picture in the reference picture list as shown in Fig. 5 (a), the inter- A first inter-layer reference picture that has been subjected to the filtering on the integer position can be displayed. Alternatively, an inter-layer reference picture having a relatively small reference index among the two inter-layer reference pictures having the same POC value may represent the first inter-layer reference picture.
FIG. 6 illustrates a method of adding an interlayer reference picture to a reference picture list in consideration of a slice type, according to an embodiment of the present invention.
When the current slice is a P slice, one reference picture list is used. In the case of a B slice, two reference picture lists, that is, a
More specifically, when the current slice is a B slice, the first inter-layer reference picture and the second inter-layer reference picture can be added to different reference picture lists.
For example, the near reference picture and the long-distance reference picture can be added to the
A second interlayer reference picture that has not been subjected to filtering with respect to the intra position is added to the
Referring to FIG. 6B, in the
However, as shown in FIG. 6, the inter-layer reference picture is not limited to being added after the long-distance reference picture. That is, it is possible to add an interlayer reference picture after adding the near reference picture to the reference picture list, or to add a near reference picture after adding the interlayer reference picture to the reference picture list.
Alternatively, a first inter-layer reference picture that has been subjected to the filtering for the intra-position is added to the
FIG. 7 illustrates a method of adding an interlayer reference picture to a reference picture list in consideration of the number of reference pictures between reference picture lists, according to an embodiment to which the present invention is applied.
When the number of reference pictures in the reference picture list of either the
As shown in FIG. 7A, the
However, when both the first interlayer reference picture and the second interlayer reference picture are used, as shown in FIG. 7 (b), two reference pictures having the same POC value in one reference picture list 0 (
For example, in the case of setting a priority to the second interlayer reference picture, a reference picture having priority in the inter-layer reference picture having the same POC value as the current picture in the reference picture list during decoding is referred to as an intra- It can be considered that the second interlayer reference picture that has not been subjected to filtering and the subordinate reference picture having the same POC value as the current picture can be regarded as a first interlayer reference picture subjected to the filtering on the integer position.
Alternatively, in order to avoid the presence of two inter-layer reference pictures having the same POC value in one reference picture list, consideration is given to adding two inter-layer reference pictures to different reference picture lists as shown in FIG. 6 It is possible.
Claims (15)
Up-sampling the decoded corresponding picture to generate an inter-layer reference picture;
Generating a reference picture list including the interlayer reference pictures; And
And performing inter-layer prediction of the current block based on the reference picture list.
Wherein the first interlayer reference picture means a reference picture subjected to filtering on an integer position and the second interlayer reference picture means a reference picture not subjected to filtering on the integer position. / RTI >
Wherein the first interlayer reference picture and the second interlayer reference picture are added to the reference picture list according to a predefined priority order between the first interlayer reference picture and the second interlayer reference picture A method for decoding a scalable video signal.
Generating inter-layer reference pictures by up-sampling the decoded corresponding pictures, generating a reference picture list including the inter-layer reference pictures, and inter-layer prediction of the current block based on the reference picture list And a predicting unit for predicting the scalable video signal.
Wherein the first interlayer reference picture means a reference picture subjected to filtering on an integer position and the second interlayer reference picture means a reference picture not subjected to filtering on the integer position. Wherein the scalable video signal decoding apparatus comprises:
Wherein the first interlayer reference picture and the second interlayer reference picture are added to the reference picture list according to a predefined priority order between the first interlayer reference picture and the second interlayer reference picture A scalable video signal decoding apparatus.
Up-sampling the decoded corresponding picture to generate an inter-layer reference picture;
Generating a reference picture list including the interlayer reference pictures; And
And performing inter-layer prediction of the current block based on the reference picture list.
Wherein the first interlayer reference picture means a reference picture subjected to filtering on an integer position and the second interlayer reference picture means a reference picture not subjected to filtering on the integer position. / RTI > A method for encoding a scalable video signal.
Wherein the first interlayer reference picture and the second interlayer reference picture are added to the reference picture list according to a predefined priority order between the first interlayer reference picture and the second interlayer reference picture A scalable video signal encoding method.
Generating inter-layer reference pictures by up-sampling the decoded corresponding pictures, generating a reference picture list including the inter-layer reference pictures, and inter-layer prediction of the current block based on the reference picture list And a prediction unit,
Wherein the interlayer reference picture includes at least one of a first interlayer reference picture and a second interlayer reference picture,
Wherein the first interlayer reference picture means a reference picture subjected to filtering on an integer position and the second interlayer reference picture means a reference picture not subjected to filtering on the integer position. Wherein the scalable video signal encoding apparatus comprises:
Wherein the first interlayer reference picture and the second interlayer reference picture are added to the reference picture list according to a predefined priority order between the first interlayer reference picture and the second interlayer reference picture A scalable video signal encoding apparatus.
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US9008181B2 (en) * | 2011-01-24 | 2015-04-14 | Qualcomm Incorporated | Single reference picture list utilization for interprediction video coding |
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US10003817B2 (en) * | 2011-11-07 | 2018-06-19 | Microsoft Technology Licensing, Llc | Signaling of state information for a decoded picture buffer and reference picture lists |
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