KR101366288B1 - A method and apparatus for decoding a video signal - Google Patents

Abstract

The present invention provides a method of obtaining first flag information that distinguishes a coding scheme of a current NAL from a header of a video signal, and in the case of multiview video coding according to the first flag information, whether the current NAL is used for inter-view prediction. Obtaining a second flag information indicating and partially decoding the video signal according to the second flag information.

Multi-view, point-in-time prediction

Description

A method and device for decoding a video signal {A METHOD AND APPARATUS FOR DECODING A VIDEO SIGNAL}

The present invention relates to the coding of video signals.

Compression coding refers to a series of signal processing techniques that transmit digitized information through a communication line or store the data in a form suitable for a storage medium. The target of compression coding includes objects such as voice, image, and character. In particular, the technique of performing compression coding on an image is referred to as video image compression. The general feature of the video image is that it has spatial redundancy and temporal redundancy.

It is intended to efficiently code a video signal by defining viewpoint information that can identify a viewpoint of a picture.

It is intended to efficiently code a video signal by defining an interview prediction flag that indicates whether the coded picture of the current NAL unit is used for inter-view prediction.

It is intended to efficiently code a video signal by generating and managing a reference picture list using interview reference information indicating a dependency between viewpoints.

Random access between viewpoints can be efficiently performed by obtaining interview reference information based on the interview picture group identification information.

It is intended to improve coding efficiency by placing attribute information of a multiview video image in an appropriate place.

In order to improve coding efficiency, an extended region of the sequence parameter set is located at an appropriate position.

The present invention provides a method of obtaining first flag information that distinguishes a coding scheme of a current NAL from a header of a video signal. A method of decoding a video signal, the method comprising: obtaining second flag information indicating and partially decoding the video signal according to the second flag information.

The present invention may further include acquiring type information of a macroblock included in a current NAL unit, and partially decoding the video signal based on the type information of the macroblock.

In addition, the present invention is characterized by decoding all data of the macroblock when the type information of the macroblock is intra prediction.

In addition, the present invention is characterized in that only the residual data of the macroblock is decoded when the type information of the macroblock is inter prediction.

The present invention also provides a method for acquiring sequence parameter information from a video signal, acquiring attribute information of a multi-view video signal from an extended region of a sequence parameter set after acquiring the sequence parameter information, and based on the attribute information. And decoding the video signal, wherein the attribute information includes interview reference information and camera parameter information indicating an inter-view reference relationship.

In addition, the present invention is characterized in that the sequence parameter information includes information indicating an image format, and when the image format is not the 4: 4: 4 format, color difference phase shift information is obtained for each viewpoint.

In addition, the present invention, when the current NAL unit is multi-view video coded according to the first flag information for distinguishing the coding scheme of the current NAL unit, the second flag information indicating whether the current NAL is used for inter-view prediction It provides a video signal decoding apparatus comprising a parser for obtaining the inter prediction unit for decoding the video signal in accordance with the second flag information.

According to the present invention, in coding a video signal, coding can be performed more efficiently by placing coding information at an appropriate place. In addition, by checking whether the current picture is used for inter-view prediction first, and transmitting information necessary for inter-view prediction only when it is used for inter-view prediction, the number of bits to be transmitted can be reduced and the decoded picture buffer By reducing the burden, coding speed can be improved. In addition, more efficient coding may be possible by using various attribute information of a multiview image.

The compression coding technique of video signal data considers spatial redundancy, temporal redundancy, scalable redundancy, and redundancy existing between views. In this compression encoding process, compression coding may be performed in consideration of mutual redundancy existing between views. The compression coding technique considering the inter-view redundancy is only an embodiment of the present invention, and the technical idea of the present invention may be applied to temporal redundancy, scalable redundancy, and the like. In addition, the term coding in this specification may include both the concepts of encoding and decoding, and may be flexibly interpreted according to the technical spirit and technical scope of the present invention.

1 is a schematic block diagram of a video signal decoding apparatus to which the present invention is applied.

The decoding apparatus includes a parsing unit 100, an entropy decoding unit 200, an inverse quantization / inverse transform unit 300, an intra prediction unit 400, a deblocking filter unit 500, a decoded picture buffer unit 600, Inter prediction unit 700 and the like.

 The parser 100 performs parsing on a network abstraction layer (NAL) basis in order to decode the received video image. In general, one or more sequence parameter sets and picture parameter sets are transmitted to the decoder before the slice header and slice data are decoded. In this case, various attribute information may be included in the NAL header area or the extension area of the NAL header. Multiview Video Coding (MVC) is an additional technology to the existing AVC technology, so it may be more efficient to add various attribute information only in the case of MVC bitstream rather than unconditionally adding. For example, flag information for identifying whether an MVC bitstream is included in the NAL header region or an extension region of the NAL header may be added. Attribute information about a multiview image may be added only when the input bitstream is a multiview image coded bitstream according to the flag information. For example, the attribute information may include view identification information, inter-view picture group identification information, inter-view prediction flag information, and the like.

First, view identification information refers to information for distinguishing a picture at a current view from a picture at a different view. When a video image signal is coded, POC (Picture Order Count) and frame_num are used to identify each picture. In the case of a multiview video image, since inter-view prediction is performed, identification information for distinguishing a picture at a current view from a picture at a different view is required. Therefore, it is necessary to define viewpoint identification information for identifying the viewpoint of the picture. The view identification information may be obtained from a header area of a video signal. For example, the header area may be an NAL header, an extended area of the NAL header, or a slice header. The view identification information may be used to obtain information of a picture that is different from the current picture, and the video signal may be decoded using the information of the picture at the other view.

Inter-view picture group identification information refers to information for identifying whether a coded picture of a current NAL unit is an interview picture group. The inter-view picture group means an encoded picture in which all slices refer only to slices in frames of the same time zone. For example, an encoded picture refers to only a slice at another viewpoint and no slice at the current viewpoint. In the decoding process of a multiview image, random access between views may be possible. As such, when the interview reference information is acquired based on the interview picture group identification information, random access between viewpoints can be performed more efficiently. This is because the inter-view reference relationship between the pictures in the interview picture group may be different from the inter-view reference relationship in the non-interview picture group. In this case, if the view identification information is used, more efficient random access may be possible.

Inter-view prediction flag information refers to information indicating whether a coded picture of a current NAL unit is used for inter-view prediction. The interview prediction flag information may be used in a part where temporal prediction or inter-view prediction is performed. In this case, the NAL unit may be used together with identification information indicating whether the NAL unit includes a slice of the reference picture. For example, when the current NAL unit does not include a slice of a reference picture according to the identification information but is used for inter-view prediction, the current NAL unit may be a reference picture used only for inter-view prediction. Alternatively, when the current NAL unit includes a slice of a reference picture according to the identification information and is used for inter-view prediction, the current NAL unit may be used for temporal prediction and inter-view prediction. In addition, even if the NAL unit does not include a slice of the reference picture according to the identification information, it may be stored in the decoded picture buffer. This is because, if the coded picture of the current NAL unit is used for inter-view prediction according to the interview prediction flag information, it needs to be stored. This will be described in detail with reference to FIG. 3.

The parsed bitstream is entropy decoded through the entropy decoding unit 200, and coefficients, motion vectors, and the like of each macroblock are extracted. The inverse quantization / inverse transform unit 300 multiplies the received quantized value by a constant constant to obtain a transformed coefficient value, and inversely transforms the coefficient value to restore the pixel value. Using the reconstructed pixel value, the intra prediction unit 400 performs intra prediction from the decoded samples in the current picture. Meanwhile, the deblocking filter unit 500 is applied to each coded macroblock in order to reduce block distortion. The filter smoothes the edges of the block to improve the quality of the decoded frame. The choice of filtering process depends on the boundary strength and the gradient of the image samples around the boundary. The filtered pictures are output or stored in the decoded picture buffer unit 600 for use as a reference picture.

The decoded picture buffer unit 600 stores or opens previously coded pictures in order to perform inter prediction. In this case, in order to store or open the decoded picture buffer unit 600, frame_num and POC (Picture Order Count) of each picture are used. Therefore, some of the previously coded pictures in MVC have pictures that are different from the current picture. Therefore, in order to utilize these pictures as reference pictures, not only the frame_num and the POC but also the view information for identifying the view point of the picture are included. It is available. In addition, information identifying a picture in a view direction having a concept similar to the frame_num may also be used.

The inter prediction unit 700 performs inter prediction using a reference picture stored in the decoded picture buffer unit 600. Inter-coded macroblocks can be divided into macroblock partitions, where each macroblock partition can be predicted from one or two reference pictures. The inter prediction unit 700 compensates for the movement of the current block by using the information transmitted from the entropy decoding unit 200. A motion vector of blocks neighboring the current block is extracted from the video signal, and a motion vector prediction value of the current block is obtained. The motion of the current block is compensated by using the obtained motion vector prediction value and the difference vector extracted from the video signal. In addition, such motion compensation may be performed using one reference picture or may be performed using a plurality of pictures. In multi-view video coding, when a current picture refers to pictures at different views, motion compensation is performed using information on a reference picture list for inter-view prediction stored in the decoded picture buffer unit 600. Can be done. In addition, motion compensation may be performed using viewpoint identification information for identifying the viewpoint of the picture.

Through the above process, the inter predicted pictures and the intra predicted pictures are selected according to the prediction mode to reconstruct the current picture. Hereinafter, various embodiments for providing an efficient decoding method of a video signal will be described.

FIG. 2 is an embodiment to which the present invention is applied and shows a structure of a NAL unit for describing attribute information for a multiview video image that may be added to a multiview video coded bitstream.

2 illustrates an example of a structure of a NAL unit to which attribute information of a multiview video image may be added. In general, the NAL unit may include a header of the NAL unit and a raw byte sequence payload (RBSP). The header of the NAL unit may include identification information nal_ref_idc indicating whether the NAL unit includes a slice of the reference picture and information nal_unit_type indicating the type of the NAL unit. In addition, the extended region of the NAL unit header may be limited. For example, when the information indicating the type of the NAL unit is related to multi-view video coding, the NAL unit may include an extended area of the NAL unit header. As a specific example, when nal_unit_type = 20 or 14, the NAL unit may also include an extended region of the NAL unit header. In addition, the extended region of the NAL unit header may include flag information svc_mvc_flag for distinguishing a coding scheme of a current NAL unit. For example, it may be identified whether the current NAL unit is a multiview video coded bitstream or a scalable video coded bitstream according to the flag information. In the case of a multiview video coded bitstream according to the flag information, attribute information of a multiview video image may be added.

As another example, when the information indicating the type of the NAL unit is information indicating a subset sequence parameter set, the RBSP may include information about the subset sequence parameter set. As a specific example, when nal_unit_type = 15, the RBSP may include information about a subset sequence parameter set, information about a slice layer, and the like. The subset sequence parameter set may include a sequence parameter set data area. The sequence parameter set data area may include sequence parameter information. For example, the sequence parameter information may include profile information, level information, color difference format information, and scaling related information.

 In addition, according to the profile information, the subset sequence parameter set may include an extended area of the sequence parameter set. For example, when the profile information profile_idc is a profile related to multi-view video coding, the subset sequence parameter set may include an extended region of the sequence parameter set. Alternatively, the sequence parameter set may include an extended area of the sequence parameter set according to the profile information. The extended area of the sequence parameter set may include interview reference information and partial decoding information. Inter-view reference information may mean information used to indicate inter-view dependency. For example, in order to indicate the inter-view dependency, information about the number of interview reference pictures and viewpoint identification information on the interview reference picture may be required. The partial decoding information may mean information indicating that the picture of the corresponding reference view may not be fully decoded. This may apply in the case of a non-interview picture group. For example, for all non-interview picture groups at all time points, the pictures at the corresponding reference time points may be partially decoded instead of completely decoded. As a specific example, in the non-interview picture group, the intra macroblock may completely decode when necessary, and the inter macroblock may decode only residual information when necessary. Alternatively, macroblock type information and motion information may be decoded for the inter macroblock and used as motion skip information at different views.

The interview reference information refers to information capable of knowing how the inter-view images are predicted. In addition, the inter-view reference information may be determined using the number of reference pictures and the view information of the reference picture. For example, first, the number of all viewpoints may be obtained, and viewpoint identification information for distinguishing each viewpoint may be determined based on the number of all viewpoints. In addition, information about the number of interview reference pictures indicating the number of reference pictures with respect to the reference direction may be obtained at each viewpoint. View identification information of each interview reference picture may be acquired according to the number information of the interview reference picture. In this manner, the interview reference information may be obtained, and the interview reference information may be identified by being divided into an interview picture group and a non-interview picture group. This can be known using the interview picture group identification information indicating whether the coded slice currently in the NAL is an interview picture group. In addition, the interview reference information acquired according to the interview picture group identification information may be used to generate and modify a reference picture list.

3 is an embodiment to which the present invention is applied and shows an overall prediction structure of a multiview image signal for explaining a decoding process using an interview prediction flag.

As shown in FIG. 3, T0 to T100 on the horizontal axis represent frames over time, and S0 to S7 on the vertical axis represent frames according to viewpoints, respectively. For example, pictures in T0 refer to images taken by different cameras in the same time zone (T0), and pictures in S0 refer to images in different time zones taken by one camera. In addition, the arrows in the drawings indicate the prediction direction and the order of each picture. For example, a P0 picture at S2 time point in the T0 time zone is a picture predicted from I0, which refers to a P0 picture at S4 time point in the TO time zone. It becomes a picture. It is also a reference picture of the B1 and B2 pictures in the T4 and T2 time zones at the time S2. As such, an interview reference picture is required to perform the inter-view prediction, and whether the current picture is used for the inter-view prediction may be determined by the interview prediction flag information. Hereinafter, an embodiment in which the interview prediction flag is used will be described.

As described above, the inter-view prediction flag information refers to information indicating whether a coded picture of a current NAL unit is used for inter-view prediction. The interview prediction flag information may be used in a part where temporal prediction or inter-view prediction is performed. In this case, the NAL unit may be used together with identification information indicating whether the NAL unit includes a slice of the reference picture. In addition, even if the NAL unit does not include a slice of the reference picture according to the identification information, it may be stored in the decoded picture buffer. This is because, if the coded picture of the current NAL unit is used for inter-view prediction according to the interview prediction flag information, it needs to be stored. In addition to using the flag information and the identification information together, one piece of identification information may indicate whether a coded picture of the current NAL unit is used for temporal prediction and / or inter-view prediction.

In another embodiment of the present invention, the interview prediction flag information may be used in a single loop decoding process. If the coded picture of the current NAL unit is not used for inter-view prediction according to the interview prediction flag information, decoding may be partially performed. For example, the intra macroblock may fully decode when necessary, and the inter macroblock may decode only residual information when necessary. As a specific example, the macroblock type information and the motion information may be decoded for the inter macroblock and used as motion skip information at different views. This may reduce the complexity of the decoding apparatus. This may be efficient when the user does not need to reconstruct the image by performing a motion compensation, among other viewpoints, when the user only sees the image of a certain view without seeing the image of all views. This will be described with reference to FIG. 3.

For example, when only a part (three views, S0, S1, S2) of FIG. 3 is examined, the coding order may be S0, S2, S1. Let the current picture to be coded be a B ₃ picture in the T2 time zone at the time S1. At this time, the picture B ₂ in the time zone T2 of S0 point for inter-time prediction may be used for the picture B ₂ in the time zone T2 of a point S2. If the B ₂ picture in the T2 time zone at time S0 is used for inter-view prediction, the interview prediction flag information may be set to one. If not used for inter-view prediction, the interview prediction flag information may be set to zero. In this case, if the interview prediction flag information of all slices at the time S0 becomes 0, it may not be necessary to decode all slices at the time S0. Therefore, the coding efficiency can be improved.

As another example, if the interview prediction flag information of all slices at the time point S0 is not 0, that is, if any one is set to 1, even if the slice is set to 0, it must be decoded. If it is assumed that the B ₂ picture in the T2 time zone at the time S0 is not used for decoding the current picture and the interview prediction flag information is set to 0 and no decoding is performed, the decoding is performed when decoding the slices at the time S0. B ₃ picture on the time zone T3 of the picture B ₃ and S0 point in time T1 of the point S0 using the picture B ₂ in the time zone T2 of the point as the reference picture is that they can not be restored. Therefore, it must be restored regardless of the interview prediction flag information.

As another example, the interview prediction flag information may be used in a decoded picture buffer (DPB). If there is no interview prediction flag information, a B ₂ picture or the like in the T2 time zone at the time of S0 must be stored in the decoded picture buffer. However, if it is known that the interview prediction flag information is 0, the B ₂ picture in the time zone T2 at the time point S0 may not be stored in the decoded picture buffer. Therefore, the memory of the decoded picture buffer can be saved.

FIG. 4 is an embodiment to which the present invention is applied and is shown to explain the position of an extended region of a sequence parameter set.

As described above with reference to FIG. 2, the subset sequence parameter set may include an extended region of the sequence parameter set according to the profile information, wherein the extended region of the sequence parameter set is located at a portion of the subset sequence parameter set. The efficiency of the coding may vary depending on the type of code. The subset sequence parameter set may include a sequence parameter set data area, and the sequence parameter set data area may include sequence parameter information. For example, the sequence parameter information may include profile information, level information, color difference format information, and scaling related information.

For example, when an extended region of the sequence parameter set is positioned ahead of the sequence parameter information, there may be a case where the sequence parameter information is defined overlappingly. Therefore, prior to the sequence parameter information to be defined first in order to use the information in the extended area of the sequence parameter set, more efficient coding may be possible when positioning the extended area of the sequence parameter set.

According to an embodiment of the present invention, information in an extended area of the sequence parameter set may be used according to color difference format information among sequence parameter information. The extended region of the sequence parameter set may include interview reference information indicating dependency between views and camera parameter information used to adjust coordinates of cameras at different viewpoints. For example, interpolation between actual pixels may be performed during a rectification operation to adjust the coordinates of the cameras. In this case, information in the extended area of the sequence parameter set may or may not be necessary according to the color difference format information. For example, in the case of 4: 4: 4 format according to the chrominance format information, each pixel value is at an integer position so that no phase shift occurs. However, in the case of 4: 4: 2 or 4: 2: 0 format, since the pixel values of the color difference signal can be sampled at various positions based on the positions of the pixel values of the luminance signal, the luminance signal and the color difference are different. Phase shift between signals may occur. Therefore, in order to perform more accurate interpolation, it is necessary to send chroma phase shift information at each time point. At this time, if the extended region of the sequence parameter set exists after the definition of the sequence parameter information, the color difference format information of the sequence parameter information can be checked first. In addition, since color phase shift information for each time point may be transmitted only in the case of 4: 4: 4 format according to the color difference format information, coding efficiency may be improved.

The decoding / encoding device to which the present invention is applied may be provided in a multimedia broadcasting transmitting / receiving device such as digital multimedia broadcasting (DMB), and may be used to decode video signals and data signals. Also, the multimedia broadcasting transmitting / receiving apparatus may include a mobile communication terminal.

In addition, the decoding / encoding method to which the present invention is applied may be stored in a computer-readable recording medium that is produced as a program for execution on a computer, and multimedia data having a data structure according to the present invention may also be read by a computer. It can be stored in the recording medium. The computer-readable recording medium includes all kinds of storage devices in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission via the Internet) . In addition, the bitstream generated by the encoding method may be stored in a computer-readable recording medium or transmitted using a wired / wireless communication network.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. , Alteration, substitution, addition, or the like. It is also possible to provide a medium for storing data applying at least one feature according to the present invention.

1 is a schematic block diagram of a video signal decoding apparatus to which the present invention is applied.

FIG. 2 is an embodiment to which the present invention is applied and shows a structure of a NAL unit for describing attribute information for a multiview video image that may be added to a multiview video coded bitstream.

3 is an embodiment to which the present invention is applied and shows an overall prediction structure of a multiview image signal for explaining a decoding process using an interview prediction flag.

FIG. 4 is an embodiment to which the present invention is applied and is shown to explain the position of an extended region of a sequence parameter set.

Claims (10)

Obtaining from the video signal first flag information identifying whether the NAL unit is a multiview video coded bitstream or a scalable video coded bitstream; Acquiring attribute information for a multiview image from the video signal when the multiview video is a bitstream according to the first flag information; wherein the attribute information includes interview prediction flag information, and the interview prediction Flag information is information indicating whether a coded picture of the NAL unit is used for inter-view prediction, Obtaining profile information from the video signal; If the profile information is a profile related to multi-view video coding, obtaining interview reference information; wherein the interview reference information refers to information used to indicate inter-view dependency. When a coded picture of the NAL unit is used for inter-view prediction according to the interview prediction flag information, generating a reference picture list for inter-view prediction using the interview reference information; And Performing inter prediction using the reference picture list for the inter-view prediction Video signal decoding method comprising a. The method of claim 1, wherein the interview reference information includes information about the number of interview reference pictures and viewpoint identification information of the interview reference picture. The method of claim 2, wherein the interview reference information is obtained for an interview picture group, The interview picture group means a picture in which all slices in a picture are encoded with reference to only slices of the same time zone. 4. The method of claim 3, wherein said interview reference information is obtained from an extended region of a sequence parameter set. The method of claim 1, wherein the first flag information is obtained from an extended area of a NAL unit header. Obtain first flag information identifying whether the NAL unit is a multiview video coded bitstream or a scalable video coded bitstream from the video signal, and is a multiview video coded bitstream according to the first flag information. A parsing unit obtaining attribute information of a multiview image from the video signal; wherein the attribute information includes interview prediction flag information, and the interview prediction flag information is used for inter-view prediction by a coded picture of the NAL unit. Information indicating whether or not A parsing unit obtaining profile information from the video signal and acquiring interview reference information when the profile information is a profile related to multi-view video coding; wherein the interview reference information is information used to indicate inter-view dependency relations. Means, A decoded picture buffer unit configured to generate a reference picture list for inter-view prediction using the interview reference information when the coded picture of the NAL unit is used for inter-view prediction according to the interview prediction flag information; And An inter prediction unit performing inter prediction using the reference picture list for inter-view prediction Video signal decoding apparatus comprising a. The video signal decoding apparatus of claim 6, wherein the interview reference information includes information about the number of interview reference pictures and viewpoint identification information of the interview reference picture. The method of claim 7, wherein the interview reference information is obtained for an interview picture group, The interview picture group is a video signal decoding apparatus, characterized in that all slices in a picture are encoded with reference to only slices of the same time zone. 9. The apparatus of claim 8, wherein the interview reference information is obtained from an extended region of a sequence parameter set. 7. The video signal decoding apparatus of claim 6, wherein the first flag information is obtained from an extended area of a NAL unit header.

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