Patent Publication Number: US-2017359563-A1

Title: Broadcast receiver and video data processing method thereof

Description:
TECHNICAL FIELD 
     The present invention relates to a broadcast receiver and a method for processing video data for use in the broadcast receiver, and more particularly to a broadcast receiver for receiving and processing three dimensional (3D) video data and a method for processing video data for use in the broadcast receiver. 
     BACKGROUND ART 
     Generally, a three dimensional (3D) image (or a stereoscopic image) provides user&#39;s eyes with a stereoscopic effect using the stereoscopic visual principle. A human being feels both near and far through a binocular parallax caused by a distance between their eyes spaced apart from each other by about 65 mm, such that the 3D image enables both right and left eyes to respectively view their associated planar images, resulting in the stereoscopic effect and the perspective effect. 
     The above-mentioned 3D image display method may be classified into a stereoscopic scheme, a volumetric scheme, a holographic scheme, etc. In case of using the stereoscopic scheme, the 3D image display method provides a left view image to be viewed by the left eye and a right view image to be viewed by the right eye, such that the user&#39;s left eye views the left view image and the user&#39;s right eye views the right view image through either polarization glasses or a display device, resulting in recognition of the 3D image effect. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Accordingly, the present invention is directed to a broadcastreceiver and a video data processing method thereof, that substantially obviate one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a method for allowing either a reception device capable of displaying 3D video data or another reception device capable of displaying only 2D video data to properly process video data, and providing a user with more efficient and convenient broadcast environments by outputting an appropriate image to each reception device. 
     Solution to Problem 
     The object of the present invention can be achieved by providing a method for processing video data of a broadcast receiver including receiving a broadcast signal including a video stream, wherein the video stream includes a plurality of video stream sections having different viewpoints, acquiring viewpoint information indicating corresponding viewpoints of the video stream sections; and outputting an interface indicating a viewpoint of the video stream that is currently displayed according to the viewpoint information. 
     In another aspect of the present invention, provided herein is a broadcast receiver including a tuner for receiving a broadcast signal, a demultiplexer for extracting a video stream from the broadcast signal, wherein the video stream includes a plurality of video stream sections having different viewpoints, a decoder for decoding the extracted video stream, and a three dimensional (3D) display controller for obtaining viewpoint information indicating corresponding viewpoints of the video stream sections, and controlling a 3D video display output of the video stream according to the obtained viewpoint information, wherein the 3D display controller outputs an interface indicating a viewpoint of the video stream that is currently displayed according to the viewpoint information. 
     Advantageous Effects of Invention 
     According to embodiments of the present invention, the broadcastreceiver recognizes a viewpoint of each image contained in a received video stream, such that it controls a 3D display output. 
     According to embodiments of the present invention, the broadcastreceiver controls the output of video data in response to each viewpoint, such that it can accurately display the 3D image, resulting in implementation of the 3D effect. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. 
       In the drawings: 
         FIG. 1  is a conceptual diagram illustrating a method for transferring a 3D content video stream according to one embodiment of the present invention. 
         FIG. 2  is a flowchart illustrating the order of processing a video stream including a Supplemental Enhancement Information (SEI) message according to one embodiment of the present invention. 
         FIG. 3  shows a syntax structure of an SEI message including view branching metadata according to one embodiment of the present invention. 
         FIG. 4  shows a syntax structure of data view_branch_data according to one embodiment of the present invention. 
         FIG. 5  shows a syntax structure of a Packetized Elementary Stream (PES) packet including view branching metadata according to one embodiment of the present invention. 
         FIG. 6  is a flowchart illustrating a method for allowing a broadcast receiver to process video data when view branching metadata is contained in a video Elementary Stream (ES) according to one embodiment of the present invention. 
         FIG. 7  is a flowchart illustrating a method for allowing a broadcast receiver to process video data when view branching metadata is contained in an additional PES packet according to one embodiment of the present invention. 
         FIG. 8  is a conceptual diagram illustrating a method for controlling the output of a 3D video stream according to one embodiment of the present invention. 
         FIG. 9  is a block diagram illustrating constituent elements of a broadcast receiver capable of processing a 3D broadcast signal including view branching metadata according to one embodiment of the present invention. 
         FIG. 10  is a flow chart illustrating a method for providing an interface indicating a viewpoint for use in a broadcast receiver according to one embodiment of the present invention. 
         FIG. 11  illustrates a display for an interface indicating a viewpoint according to one embodiment of the present invention. 
         FIG. 12  is a conceptual diagram illustrating viewpoint control of a display image obtained through an interface indicating a viewpoint according to one embodiment of the present invention. 
         FIG. 13  illustrates a user interface for indicating whether a 3D broadcast service is provided at a 2D image viewing mode. 
         FIG. 14  illustrates a table format of Terrestrial Virtual Channel Table (TVCT) information contained in Program and System Information Protocol (PSIP) information of a broadcast signal according to one embodiment of the present invention. 
         FIG. 15  illustrates a table format of a Program Map Table (PMT) contained in Program Specific Information (PSI) information of a broadcast signal according to one embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention, rather than to show the only embodiments that can be implemented according to the present invention. 
     Prior to describing the present invention, it should be noted that most terms disclosed in the present invention are defined in consideration of functions of the present invention and correspond to general terms well known in the art, and can be differently determined according to intention of those skilled in the art, usual practices, or introduction of new technologies. In some cases, a few terms have been selected by the applicant as necessary and will hereinafter be disclosed in the following description of the present invention. Therefore, it is preferable that the terms defined by the applicant be understood on the basis of their meanings in the present invention. 
     The 3D image display method includes a stereoscopic imaging scheme in which two viewpoints are considered and a multi-view imaging scheme in which three or more viewpoints are considered. In contrast, a single view image scheme shown in the related art may also be referred to as a monoscopic image scheme. 
     The stereoscopic imaging scheme is designed to use one pair of right and left view images acquired when a left-side camera and a right-side camera spaced apart from each other by a predetermined distance capture the same target object. The multi-view imaging scheme uses three or more images captured by three or more cameras spaced apart by a predetermined distance or angle. Although the following description discloses embodiments of the present invention using the stereoscopic imaging scheme as an example, the inventive concept of the present invention may also be applied to the multi-view imaging scheme. 
     A stereoscopic image or multi-view image may be compressed and coded according to a variety of methods including a Moving Picture Experts Group (MPEG) scheme, and transmitted to a destination. 
     For example, a stereoscopic image or a multi-view image may be compressed and coded according to the H.264/Advanced Video Coding (AVC) scheme, and transmitted. In this case, the reception system may decode a received image in reverse order of the H.264/AVC coding scheme, such that it is able to obtain the 3D image. 
     In addition, one of a left view image and a right view image of a stereoscopic image or one of multiple-view images may be assigned to an image of a base layer, and the remaining one may be assigned to an image of an extended layer. The base layer image may be encoded using the same method as the monoscopic imaging method. In association with the extended layer image, only information of the relationship between the base layer image and the extended layer image may be encoded and transmitted. As an exemplary compression coding scheme for the base layer image, a JPEG, an MPEG-2, an MPEG-4, or a H.264/AVC scheme may be used. For convenience of description, the H.264/AVC scheme may be exemplarily used in one embodiment of the present invention. In one embodiment of the present invention, the compression coding scheme for an image of an upper or higher layer may be set to the H.264/Multi-view Video Coding (MVC) scheme. 
     When the MVC scheme is additionally applied to the AVC scheme or the right/left image sequences are coded using only the AVC scheme so as to implement the stereoscopic display, one point to be duly considered when broadcasting corresponding 3D content is compatibility with the 2D broadcast receiver of the related art. For the related broadcast receiver incapable of supporting the 3D image display, if one of right and left view images is encoded and transmitted according to a backward compatible method, the 2D broadcast receiver recognizes and outputs only the corresponding signal, such that it may be possible for a user to view the corresponding contents through the related device. 
     In one embodiment of the 3D content transmission, one of right/left view images is selected and the selected image is encoded into a 2D compatible signal, such that the 2D compatible signal is transferred. However, in this case, a video stream, to be transmitted as a 2D image within the same content in consideration of a manufacturer&#39;s intention, an image effect, or a viewing environment, may be edited into image sequences having different viewpoints in respective sections, such that the resultant image sequences may be transmitted. For example, when generating the 2D video stream in respective sections within the same content, data of an initial 10 minutes is assigned to the left view image and data of the next  15  minutes is assigned to the right view image, such that the 2D video stream is formed. For compatibility with the related device, the formed 2D image stream is backward-compatible coded (e.g., AVC-coded) through a single stream, such that the coded result is transferred. 
       FIG. 1  is a conceptual diagram illustrating a method for transferring a 3D content video stream according to one embodiment of the present invention. 
     Referring to  FIG. 1 , a left view image sequence  1010  is captured and edited at a left view and a right view image sequence  1040  is captured and edited at a right view, such that the 3D content is manufactured. 
     In order to implement a display function for the 2D broadcast receiver, a transmission system selects one of left and right view image sequences  1010  and  1040 , and codes and transmits the selected one. However, if required, the video stream  1020  acquired when the left view image and the right view image are selected and arranged may be coded and transmitted. 
     In  FIG. 1 , the video stream  1020 , in which a left view video stream section, a right view video stream section, and the left view video stream section are arranged, is an AVC-coded video stream capable of being displayed by the 2D broadcast receiver for compatibility with the related device. In this case, the video stream section indicates a video stream section contained in a video stream of different viewpoints, and this section may be configured in units of a video frame, a picture, or a sequence. 
     An additional video stream  1030  for the 3D broadcast receiver is encoded by the AVC scheme or the MVC scheme, and transmitted. 
     There is a need for the 2D broadcast receiver to receive the video stream  1020  having been coded and transmitted for the 2D broadcast receiver, decode the received video stream  1020 , and output the decoded result. However, when the 3D broadcast receiver receives the video stream  1020  for the 2D broadcast receiver and the additional video stream  1030 , and outputs the received video streams  1020  and  1030  without any change, there may arise an unexpected section in which the left view image and the right view image are replaced with each other. 
     In other words, if a viewpoint is changed to another viewpoint within the coded video streams  1020  and  1030  as shown in  FIG. 1 , the 3D image may not be normally displayed under the condition that the 3D output is incorrectly controlled in response to a corresponding viewpoint. When decoding the 3D video stream, the right view image section must be transmitted to a display output unit for displaying the right view image, and the left view image section must be transmitted to a display output unit for displaying the left view image. The change or control of such viewpoints may even be applied to the multi-view image. 
     View branching metadata indicating signaling data, that informs the coded image sequence of a corresponding image&#39;s viewpoint in units of a picture, frame or sequence, will hereinafter be described with reference to the annexed drawings. A method for delivering the view branching metadata and broadcast receiver&#39;s operations performed when the view branching metadata is received will hereinafter be described in detail. 
     Firstly, a method for including view branching metadata in a video Elementary Stream (ES) and transmitting the resultant video ES in accordance with one embodiment of the present invention will hereinafter be described. 
     In case of using H.264 (or AVC) video data or MVC extension video data, a video ES may include a Supplemental Enhancement Information (SEI) message. The SEI message indicates additional information unnecessary for a decoding process of a Video Coding Layer (VCL). In addition, the SEI message may include each picture s timing information related to a Hypothetical Reference Decoder (HRD), information of a pan/scan function (i.e., a function for reading and displaying some parts of the decoded image), information necessary for random access, information independently defined by a user, and the like. 
       FIG. 2  is a flowchart illustrating the order of processing a video stream including an SEI message according to one embodiment of the present invention. 
     A method for processing an access unit shown in  FIG. 2  will hereinafter be described in detail. 
     When an access unit delimiter Network Abstraction Layer (NAL) unit is present at step S 2010 , it shall be the first NAL unit. There shall be at most one access unit delimiter NAL unit in any access unit. 
     When any SEI NAL units are present at step S 2020 , they shall precede the primary coded picture at step S 2030 . When an SEI NAL unit containing a buffering period SEI message is present, the buffering period SEI message shall be the first SEI message payload of the first SEI NAL unit in the access unit. 
     The primary coded picture shall precede the corresponding redundant coded pictures. When redundant coded pictures are present at step S 2040 , they shall be ordered in ascending order of the value of redundant_pic_cnt. 
     When a sequence parameter set extension NAL unit is present, it shall be the next NAL unit after a sequence parameter set NAL unit having the same value of seq_parameter_set_id as in the sequence parameter set extension NAL unit. 
     When one or more coded slices of an auxiliary coded picture without partitioning NAL units is present at step S 2050 , they shall follow the primary coded picture and all redundant coded pictures (if any). 
     When an end of sequence NAL unit is present at step S 2060 , it shall follow the primary coded picture and all redundant coded pictures (if any) and all coded slices of an auxiliary coded picture without partitioning NAL units (if any). 
     When an end of stream NAL unit is present at step S 2070 , it shall be the last NAL unit. 
     In one embodiment of the present invention, a transmission system may include view branching metadata in the SEI area of the video ES, and transmit the resultant video ES. 
       FIG. 3  shows a syntax structure of an SEI message including view branching metadata according to one embodiment of the present invention. 
     As can be seen from the SEI message of  FIG. 3 , the transmission system transmits additional information needed for broadcast application using ‘user_identifier’ and ‘user_structure’ fields included in a ‘user_data_registered_itu_t_ 35 ( )’ field in which an SEI payloadType value is set to 4. An ‘ATSC_user_data( )’ field is contained in the ‘user_structure( )’ field, and the transmission system is able to recognize that corresponding data is data ‘view_branch_data’ by referring to a ‘user_data_type_code’ field. A receiver is able to recognize which one of views is contained in a corresponding picture using fields contained in a ‘view_branch_data( )’ field of a ‘user_data_type structure’ field. 
       FIG. 4  shows a syntax structure of view branch data ‘view_branch_data’ according to one embodiment of the present invention. 
     Referring to  FIG. 4 , a ‘left_right_view_flag’ field indicates whether a picture including the SEI message is a left view image or a right view image. In the embodiment shown in  FIG. 4 , if the ‘left_right_view_flag’ field is set to ‘0’, this means that the picture including the SEI message is a left view image. Otherwise, if the ‘left_right_view_flag’ field is set to ‘1’, this means that the picture including the SEI message is a right view image. 
     For convenience of description and better understanding of the present invention, the embodiment shown in  FIG. 4  shows the stereoscopic image as an example. In case of the multi-view image, two or more bits are assigned to the ‘view_flag’ field so as to indicate a viewpoint of a corresponding image. 
     A method for transmitting view branching metadata may be made available in various ways, and associated embodiments will hereinafter be described in detail. 
     In one embodiment, view branching metadata may be transmitted at the position of an Instantaneous Decoding Refresh (IDR) picture indicating the head picture of an image sequence. In association with the IDR picture, because the H.264/AVC scheme generally allows an interframe prediction indicating that a P picture located behind an I picture refers to other picture located in front of the I picture, it is difficult to fully initialize a status using only a general I picture, such that the IDR picture is used to solve this problem. 
     In another embodiment, view branching metadata may be transmitted every picture position. 
     In another embodiment, view branching metadata may be transmitted at a start position of each sequence. In this case, previous view branching metadata may be maintained until new view branching metadata is received. 
     In another embodiment, view branching metadata may be transmitted every picture position, and at the same time a corresponding value may be kept at the same value within one sequence. In other words, if one viewpoint is selected in a specific section for a 2D video sequence, a video sequence may be coded such that the same viewpoint is maintained in one sequence. 
     In addition, other embodiments may also be proposed for each case that stereoscopic video data is transferred as two streams or one stream. 
     In one embodiment, if stereoscopic video data is transferred as two streams, view branching metadata is basically included in a base view video stream and then transmitted. Even in the case of processing an extended view video stream, it is possible to use information of a viewpoint included in the base view video stream. For example, in the case of the stereoscopic video stream, a viewpoint of the extended view video stream is opposite to that of the base view video stream, such that it is possible to use information of a viewpoint included in the base view video stream even in the case of processing the extended view video stream. In another embodiment, the base view video stream may even include the viewpoint information of the extended view video stream, and transmits the resultant base view video stream. 
     In addition, view branching metadata may be included in the extended view video stream and transmitted, or may be included in each of all streams and transmitted. 
     In another embodiment, if the stereoscopic video data is transferred as one stream, the left view image and the right view are mixed in the form of side-by-side, top-bottom, checkerboard, horizontally/vertically interleaved format, etc., and then transmitted. Even in this case, view branching metadata is included in the video data stream as described above, a 2D broadcast receiver or a 3D broadcast receiver for a 2D mode reconstructs a 2D sequence composed of a left view image or a right view image using the view branching metadata, and may display the reconstructed 2D sequence. 
     A plurality of embodiments related to viewpoint identification may be applied to the stereoscopic video data formed in two streams. 
     In one embodiment, left/right identification for a stream may be initially assigned using view branching metadata, such that a branching may be carried out. In another embodiment, basic viewpoint identification for a corresponding stream may be assigned via a flag indicating a viewpoint, and the branching may be carried out via view branching metadata. 
     Hereinafter, a method for constructing an additional Packetized Elementary Stream (PES) packet including view branching metadata and transmitting the constructed PES packet in accordance with one embodiment of the present invention will be described in detail. 
     Instead of including view branching metadata in the video stream as described above, a transmission system may construct the view branching metadata of an additional independent PES packet except for video and audio streams, and then transmit the constructed view branching metadata. 
       FIG. 5  shows a syntax structure of a PES packet including view branching metadata according to one embodiment of the present invention. 
     In  FIG. 5 , a ‘stream_id’ field has a value of ‘0xBF’, and indicates a stream ID of a PES including view branching metadata. 
     When different private data PESs are serviced, a ‘data_identifier’ field indicates that a corresponding PES is equal to a PES related to view branching metadata. 
     A ‘base_view_flag’ field indicates whether a stream to which metadata transferred via ‘view_branch_segment’ is applied is a base view stream (e.g., AVC stream) or an extended view stream (e.g., MVC extension stream). 
     A ‘number_of_scenes’ field indicates the number of scenes contained in a video stream interacting with view branching metadata, and each scene includes one of the left view image and the right view image in case of a stereoscopic image. 
     A ‘left_right_view_flag’ field indicates whether a picture included in a corresponding frame is a left view image or a right view image. In the embodiment shown in  FIG. 5 , if the ‘left_right_view_flag’ field is set to ‘0’, this means the picture is a left view image. Otherwise, if the ‘left_right_view_flag’ field is set to ‘1’, this means that the picture is a right view image. 
     For convenience of description and better understanding of the present invention, the embodiment shown in  FIG. 5  shows the stereoscopic image as an example. In case of the multi-view image, two or more bits are assigned to the ‘view_flag’ field so as to indicate a viewpoint of a corresponding image. Information about a frame section related to a viewpoint indicated by the ‘left_right_view_flag’ field may be acquired from a ‘start_frame_num’ field and an ‘end_frame_num’ field. 
     The ‘start_frame_num’ field indicates a frame number of a first picture of a corresponding scene, and may be represented by the decoding order or the displaying order in accordance with embodiments. 
     The ‘end_frame_num’ field indicates a frame number of the last picture of a corresponding scene, and may be represented by the decoding order or the displaying order. 
       FIG. 6  is a flowchart illustrating a method for allowing a broadcast receiver to process video data when view branching metadata is contained in a video Elementary Stream (ES) according to one embodiment of the present invention. 
     Referring to  FIG. 6 , a broadcast receiver receives a broadcast signal, parses Program and System Information Protocol (PSIP) information, and may acquire PID information of a video ES from a Program Map Table (PMT) or Terrestrial Virtual Channel Table (TVCT) contained in the PSIP information at step S 6010 . The broadcast receiver may filter a corresponding video ES by setting a filter using the acquired PID information, and then decode the extracted video stream at step S 6020 . 
     The broadcast receiver is able to decode the SEI message by decoding the video stream at step S 6030 . The decoding of the SEI message contained in the video stream may be carried out according to the method illustrated in  FIGS. 2 and 3 . 
     The broadcast receiver parses ‘view_branch_data’ contained in the SEI message, such that it is able to recognize a viewpoint of a corresponding picture at step S 6040 . The embodiment shown in  FIG. 6  discloses the case of the stereoscopic image as an example. In this embodiment of  FIG. 6 , a viewpoint of a corresponding picture may be a left view or a right view. 
     The broadcast receiver controls the 3D stereoscopic output of the decoded picture using the viewpoint information of the parsed view_branch_data at step S 6050 . In accordance with the 3D stereoscopic output control of the broadcast receiver, the left view image of the 3D stereoscopic image is output to the left view image output unit, and the right view image of the same is output to the right view image output unit, such that the 3D stereoscopic image may be displayed according to the intended 3D effect. 
       FIG. 7  is a flowchart illustrating a method for allowing a broadcast receiver to process video data when view branching metadata is contained in an additional Packetized Elementary Stream (PES) packet according to one embodiment of the present invention. 
     Referring to  FIG. 7 , a broadcast receiver receives a broadcast signal, and parses Program and System Information Protocol (PSIP) information. The broadcast receiver may acquire PID information of a PES packet including view branching metadata from a PMT or TVCT contained in the parsed PSIP information at step S 7010 . 
     The broadcast receiver performs a filtering process using the acquired PID information, such that it may transmit the PES packet including the view branching metadata to a view branching metadata processor at step S 7020 . The view branching metadata processor may decode and store the received PES packet at step S 7030 . 
     The broadcast receiver may acquire a viewpoint of a picture, to be decoded and output, using the decoded view branching metadata at step S 7040 . The embodiment shown in  FIG. 7  discloses the case of the stereoscopic image as an example. In this embodiment of  FIG. 7 , a viewpoint of a corresponding picture may be a left view or a right view. 
     The broadcast receiver controls the output of the decoded picture using the acquired viewpoint information at step  57050 . In accordance with the 3D stereoscopic output control of the broadcast receiver, the left view image of the 3D stereoscopic image is output to the left view image output unit, and the right view image of the same is output to the right view image output unit, such that the 3D stereoscopic image may be displayed according to the intended 3D effect. 
       FIG. 8  is a conceptual diagram illustrating a method for controlling the output of a 3D video stream according to one embodiment of the present invention. 
     In  FIG. 8 , a 3D video stream is a stereoscopic image, a video stream  8010  of a base layer is coded according to the AVC scheme, and a video stream  8020  of an extended layer is coded according to the AVC or MVC extension scheme. The video stream  8010  of the base layer includes sections corresponding to the order of left view (L)→right view (R)→left view (L) (i.e., left-right-left sections), and the video stream  8020  of the extended layer includes sections corresponding to the order of right view (R)→left view (L)→right view (R) (i.e., right-left-right sections). 
     A 2D broadcast receiver or a 3D broadcast receiver for a 2D mode receives the video stream  8030  of the base layer, and outputs the received video stream  8030  without any change. A 3D broadcast receiver for a 3D mode processes view branching metadata as described above, and controls the output of the decoded video stream according to the acquired viewpoint information. Accordingly, in the output video stream  8040 , the left view image may be output to the left view image output unit, and the right view image may be output to the right view image output unit. 
       FIG. 9  is a block diagram illustrating constituent elements of a broadcast receiver capable of processing a 3D broadcast signal including view branching metadata according to one embodiment of the present invention. 
     Referring to  FIG. 9 , a broadcast receiver includes a tuner and demodulator  9010 , a Vestigial Side Band (VSB) decoder  9020 , a Transport Packet (TP) demultiplexer (TP Demux)  9030 , a PSI/PSIP processor  9040 , an Audio/Video (A/V) decoder, an Extension video decoder  9060 , and a 3D stereoscopic control and 3D formatter  9070  (hereinafter referred to as a 3D video processor  9070 ). In accordance with one embodiment of the present invention, the broadcast receiver may further include a metadata processor  9080 . The A/V decoder  9050  includes a video coding layer  9090  for processing video data and a header &amp; extensions  9100  for processing supplemental data. The Extension video decoder  9060  may include a video coding layer  9110  for processing video data and a Header &amp; Extensions  9120  for processing supplemental data. Although not shown in  FIG. 9 , the broadcast receiver may further include a controller capable of controlling individual components of the broadcast receiver. 
     Besides, the broadcast receiver may include a plurality of image output units (not shown in  FIG. 9 ) to output images of corresponding viewpoints as necessary. 
     The broadcast receiver for displaying a stereoscopic image may further include a left view image output unit and a right view image output unit. In addition, one image output unit may control images of individual viewpoints, and then display the resultant images on a screen. 
     The A/V decoder  9050  is a decoder for decoding base view video data for the 2D image output, and the Extension video decoder  9060  is a decoder for decoding extended view video data for the 3D image output. 
     The broadcast receiver may be operated in various ways according to methods for transmitting view branching metadata. 
     A method ‘A’( 9140  or  9150 ) indicates how the broadcast receiver is operated when view branching metadata is transmitted after being contained in an SEI message of a video stream. A method ‘B’ ( 9130 ) indicates how the broadcast receiver is operated when view branching metadata is transmitted after being contained in an additional PES packet. 
     Firstly, operations of the broadcast receiver when view branching metadata is contained in the SEI message of the video stream and is then transmitted will hereinafter be described in detail. 
     The broadcast receiver extracts a video stream PID from the PMT and TVCT information parsed from the PSI/PSIP processor  9040 , and allows the TP demultiplexer  9030  to output a video stream using the corresponding video stream PID. If the output video stream corresponds to a base view video stream (AVC), the TP demultiplexer  9030  outputs the video stream to the A/V decoder  9050 . If the output video stream corresponds to an extended view video stream (MVC extension), the TP demultiplexer  9030  outputs the video stream to the Extension video decoder  9060 . 
     The A/V decoder  9050  and the Extension video decoder  9060  respectively process video data and supplemental data contained in the received video stream, and output the processed data to the 3D video processor  9070 . In this case, the A/V decoder  9050  and the Extension video decoder  9060  process view branching metadata contained in the video stream, and thus output viewpoint information. 
     The 3D video processor  9070  controls video data received from the A/V decoder  9050  and the Extension video decoder  9060  using viewpoint information in response to each viewpoint, and then outputs the controlled data. 
     The viewpoint information may be output from at least one of the A/V decoder  9050  and the Extension video decoder  9060 . 
     Operations of the broadcast receiver when view branching metadata is contained in an additional PES packet and then transmitted will hereinafter be described in detail. 
     The broadcast receiver extracts a PID of a PES packet including view branching metadata from the PMT and TVCT information parsed from the PSI/PSIP processor  9040 , and allows the TP demultiplexer  9030  to output the PES packet (view branching segment) to the metadata processor  9080  using the corresponding PID. 
     The metadata processor  9080  processes the PES packet including view branching metadata, such that it outputs viewpoint information to the 3D video processor  9070 . 
     The 3D video processor  9070  controls video data received from the A/V decoder  9050  and the Extension video decoder  9060  using viewpoint information in response to each viewpoint, and then outputs the controlled data. 
     In one embodiment, the 3D video processor  9070  reconstructs a video stream in response to each viewpoint, such that one video stream including a left view image may be output to the left view image output unit and the other video stream including a right view image may be output to the right view image output unit. In another embodiment, the 3D video processor  9070  may read video data of a corresponding viewpoint from a video stream buffer (not shown) using the acquired viewpoint information, and control the image output unit to output the read video data. 
     When a user views a 3D image, the user may switch a current viewing mode (i.e., a 3D image viewing mode) to a 2D image viewing mode in consideration of various factors, for example, eye fatigue, a variation in a viewing environment, broadcast content and the like. In relation to the above-mentioned mode switching, it is necessary to provide viewpoint information to the user. 
     A broadcast receiver for providing a User Interface (UI) to the user using the above-mentioned viewpoint information and a method for providing the UI will hereinafter be described in detail. 
       FIG. 10  is a flow chart illustrating a method for providing an interface indicating a viewpoint for use in a broadcast receiver according to one embodiment of the present invention. 
     Referring to  FIG. 10 , the controller switches a video viewing mode of the broadcast receiver to another mode at step S 10010 . In more detail, the controller switches a 3D video viewing mode to a 2D video viewing mode at step S 10010 . The broadcast receiver may receive a user input signal, such that it can perform the above-mentioned switching operation according to the received user input signal. 
     The broadcast receiver decodes a 2D video stream using the decoder and outputs the decoded video stream at step S 10020 . During the 2D video viewing mode, the broadcast receiver may decode only a base-view video stream, and output the decoded video stream. 
     The broadcast receiver acquires viewpoint information of an output video stream at step S 10030 . The operation for acquiring viewpoint information of the output video stream of the broadcast receiver may performed as in a description above. In other words, the broadcast receiver can acquire viewpoint information using a metadata processor or a decoder, and a detailed description thereof is identical to those of  FIGS. 3 to 9 . 
     The broadcast receiver generates an interface that indicates a viewpoint of an output video stream according to viewpoint information, and outputs the generated interface indicating a viewpoint using a 3D video processor at step S 10040 . The broadcast receiver recognizes whether a video stream that is currently output is a left-view video stream or a right-view video stream through a left_right_view_flag field contained in viewpoint information, generates an interface indicating a viewpoint of the video stream, and outputs the generated interface. 
     In one embodiment of the present invention, if the left_right_view_flag field acquired from either the decoder or the metadata processor is set to zero ‘0’, the broadcast receiver determines that a displaying image is a left-view image. If the left_right_view_flag field acquired from either the decoder or the metadata processor is set to ‘1’, the broadcast receiver determines that a displaying image is a right-view image. Then the broadcast receiver may represent the determined viewpoint of the displaying image using a user interface. 
       FIG. 11  illustrates a display for an interface indicating a viewpoint according to one embodiment of the present invention. 
       FIG. 11  shows display screen images  11010  and  11020  at a 2D video viewing mode (i.e., a 2D mode). In the embodiment of the present invention, the broadcast receiver displays interfaces indicating a viewpoint  11030  and  11040  (each of which may also be called as a view indicator), that indicate viewpoints of a display image, on some parts of a screen where a 2D image is currently displayed. 
     In this case, the broadcast receiver may represent viewpoint information using the interfaces indicating a viewpoint  11030  and  11040  according to viewpoint information of a video stream that is currently displayed. In more detail, the broadcast receiver may represent a viewpoint of an image that is currently displayed through the interfaces indicating a viewpoint  11030  and  11040  according to a field value of the left_right_view_flag field contained in the viewpoint information. 
     In one embodiment of the present invention, the interface indicating a viewpoint  11030  of the display image  11010  shown in  FIG. 11  shows an exemplary case in which the left_right_view_flag field contained in the viewpoint information of a current image is set to ‘0’. In the interface indicating a viewpoint  11030 , a left block ‘L’ indicating a left view is colored or highlighted, so that the colored or highlighted left block ‘L’ represents that a left-view image is currently displayed. In the display image  11020 , if the left_right_view_flag field contained in viewpoint information of a current display image is set to ‘1’, a right block ‘R’ indicating a right view is colored or highlighted, so that the colored or highlighted right block ‘R’ is currently displayed. If necessary, locations of the interfaces indicating a viewpoint  11030  and  11040  and a method for displaying the interface indicating a viewpoint may be different from those of  FIG. 11  according to embodiments and implementation methods. 
       FIG. 12  is a conceptual diagram illustrating a viewpoint control of a display image obtained through an interface indicating a viewpoint according to one embodiment of the present invention. 
     In one embodiment, if a user selects the L or R block of the interface indicating a viewpoint, a current viewpoint is changed to the user-selected viewpoint through the interface, so that the image output operation may be controlled in response to the changed viewpoint. 
     In the case where the image that is currently displayed through the interface indicating a viewpoint  12030  of the display image  12010  is denoted by ‘L’, ‘R’ may be selected through a remote-controller input action or a pointer displayed on screen. If the user selects the right view, the broadcast receiver converts a current output image into a right-view image. In one embodiment, in the case where a left-view image that is currently displayed on the screen is decoded from a base-view video stream and a viewpoint conversion is selected by the interface indicating a viewpoint, a broadcast receiver changes a current decoding target serving as a base-view video stream to an extended-view video stream, decodes a right-view image of a corresponding interval, and displays the decoded image  12020 . 
     Therefore, the user can recognize viewpoint information of a current image through the interface indicating a viewpoint, and can actively select a specific viewpoint image and view image of the selected viewpoint. 
       FIG. 13  illustrates a user interface for indicating whether a 3D broadcast service is provided at a 2D image viewing mode. 
     Referring to  FIG. 13 , if the user switches a current channel or program to another channel or program while viewing broadcast content at a 2D video viewing mode (i.e., a 2D mode), the 2D video viewing mode can be basically maintained. However, under the condition that content of the switched channel or program is provided as a 3D broadcast service, it is necessary to inform the user of this condition. 
     In  FIG. 13 , the channel or program switching is performed, so that a 2D image is displayed on the display screen  13010 . In this case, the broadcast receiver determines whether or not a 3D broadcast service for a corresponding channel or program is provided. If it is possible for the user to view the 3D image, the user interfaces  13020  and  13030  for indicating this situation are displayed. 
     In the embodiment of  FIG. 13 , a first UI  13020  and a second UI  13030  are shown. The first UI  13020  provides a user input for switching a viewing mode to a 3D-image viewing mode. If the user desires to continuously view a 2D image, the second UI  13030  provides a user input for stopping displaying UIs. In the case of switching a channel or program, the first UI  13020  for enabling the user to recognize the 3D availability is displayed for 5 to 10 seconds at intervals of 1 to 3 minutes. If the user desires to continuously view an image at a 2D mode, the user presses the second UI  13030  to prevent the 3D availability from being displayed. The UIs  13020  and  13030  may be selectively entered through an arrow mark or may be entered through a button of a remote-controller. In this case, information of a corresponding button may be additionally displayed through such UIs. For example, if the user desires to view a 3D image, the user presses the first button 1. If the user desires to continuously view a 2D image, the user presses the second button 2. 
     In the embodiment of  FIG. 13 , the broadcast receiver must determine whether a channel or program that is currently displayed provides the 3D broadcast service or not. A method for determining whether the 3D broadcast service is provided will hereinafter be described with reference to the following embodiments. 
     First, if an extended view video stream is contained in the received broadcast signal, the broadcast receiver determines that the 3D broadcast service is provided. That is, the PSI/PSIP processor parses the system information. If the extended view video stream or associated information is present in the received broadcast signal, the broadcast receiver determines whether the 3D broadcast service is provided. 
     In addition, the broadcast receiver parses a TVCT contained in PMT or PSIP information contained in the PSI information, and determines the presence or absence of a 3D broadcast service. 
     If the user selects the 3D video viewing mode through the above-mentioned UI, the broadcast receiver decodes the 3D video stream and displays the decoded 3D video stream. In this case, the broadcast receiver may decode and output the 3D video stream using the above-mentioned method with reference to  FIGS. 1 to 9 . That is, the broadcast receiver acquires viewpoint information, controls a base view video stream and an extended view video stream according to the acquired viewpoint information, and outputs the controlled resultant streams. 
       FIG. 14  illustrates a table format of TVCT information contained in PSIP information of a broadcast signal according to one embodiment of the present invention. 
     Individual fields contained in the TVCT shown in  FIG. 14  are as follows. 
     A ‘table_id’ field is an 8-bit unsigned integer field that indicates the type of table section. 
     A ‘section_syntax_indicator’ field is a one-bit field which shall be set to ‘1’ for the ‘terrestrial_virtual_channel_table_section( )’ field. 
     A ‘private_indicator’ field is a one-bit field which shall be set to ‘1’. 
     A ‘section_length’ field is a 12-bit field in which the first two bits shall be set to ‘00’, and specifies the number of bytes of the section, starting immediately following the ‘section_length’ field, and including the CRC. 
     A ‘transport stream_id’ field indicates the 16-bit MPEG-2 Transport Stream (TS) ID. The ‘transport stream_id’ field distinguishes a Terrestrial Virtual Channel Table (TVCT) from others that may be broadcast in different PTCs. 
     A ‘version_number’ field serving as a 5-bit field indicates a version number of the Virtual Channel Table (VCT). 
     A ‘current_next_indicator’ field is a one-bit indicator. In the case where the ‘current_next_indicator’ field is set to ‘1’, this means that a transmitted Virtual Channel Table (VCT) is currently applicable. When a bit of the ‘current_next_indicator’ field is set to ‘0’, this means that the transmitted table is not yet applicable and shall be the next table to become valid. 
     A ‘section_number’ field is an 8-bit field which gives the number of this section. 
     A ‘last section_number’ field serving as an 8-bit field specifies the number of the last section (that is, the section with the highest section_number value) of the complete Terrestrial Virtual Channel Table (TVCT). 
     A ‘protocol_version’ field serving as an 8-bit unsigned integer field is used to allow, in the future, the table type to carry parameters that may be structured differently than those defined in the current protocol. 
     A ‘num_channels_in_section’ field serving as an 8-bit field specifies the number of virtual channels in this VCT section. 
     A ‘short_name’ field may indicate the name of the virtual channel, represented as a sequence of one to seven 16-bit code values interpreted in accordance with the UTF-16 standard for unicode character data. 
     A ‘major_channel_number’ field indicates a 10-bit number that represents the ‘major’ channel number associated with the virtual channel being defined in this iteration of the ‘for’ loop. 
     A ‘minor_channel_number’ field indicates a 10-bit number in the range from ‘0’ to ‘999’ so as to represent the ‘minor’ or ‘sub’ channel number. This ‘minor_channel_number’ field together with the ‘major_channel_number’ field may indicate a two-part channel number, where the ‘minor_channel_number’ field represents the second or right-hand part of the number. 
     A ‘modulation_mode’ field including an 8-bit unsigned integer may indicate a modulation mode for the transmitted carrier associated with the virtual channel. 
     A ‘carrier_frequency’ field may indicate an allowed carrier frequency. 
     A ‘channel_TSID’ field is a 16-bit unsigned integer field in the range from 0x0000 to 0xFFFF. The ‘channel_TSID’ field represents an MPEG-2 Transport Stream (TS) ID associated with the Transport Stream (TS) carrying the MPEG-2 program referenced by the virtual channel. 
     A ‘program_number’ field includes a 16-bit unsigned integer that associates the virtual channel being defined here with the MPEG-2 program association and TS program map tables. 
     An ‘ETM_location’ field serving as a 2-bit field specifies the existence and the location of an Extended Text Message (ETM). 
     An ‘access_controlled’ field indicates a 1-bit Boolean flag. When the Boolean flag of the ‘access_controlled’ field is set, this means that accessing the events associated with a virtual channel may be controlled. 
     A ‘hidden’ field indicates a 1-bit Boolean flag. When the Boolean flag of the ‘hidden’ field is set, this means that the virtual channel is not accessed by a user by a direct entry of the virtual channel number. 
     A ‘hide_guide’ field indicates a Boolean flag. When the Boolean flag of the ‘hide_guide’ field is set to zero ‘0’ for a hidden channel, this means that the virtual channel and virtual channel events may appear in EPG displays. 
     A ‘service_type’ field is a 6-bit enumerated type field that shall identify the type of service carried in the virtual channel. 
     A ‘source_id field’ includes a 16-bit unsigned integer that identifies the programming source associated with the virtual channel. 
     A ‘descriptors_length’ field may indicate a total length (in bytes) of descriptors for a virtual channel. 
     A ‘descriptor( )’ field may include zero or more descriptors determined to be appropriate for the ‘descriptor( )’ field. 
     An ‘additional_descriptors_length’ field may indicate a total length (in bytes) of a VCT descriptor list. 
     A ‘CRC_32’ field is a 32-bit field which contains a CRC value that ensures a zero output of registers in the decoder defined in Annex A of ISO/IEC 13818 1 “MPEG-2 Systems” [8] after processing the entire Terrestrial Virtual Channel Table (TVCT) section. 
     The ‘service_type’ field  14010  may also indicate that a broadcast service provided from a corresponding channel is a 3D broadcast service. In accordance with one embodiment, if the ‘service_type’ field  14010  has a field value of 0x12, it can be recognized that a corresponding virtual channel provides a 3D broadcast program (including an audio stream, a video stream, and an additional video stream for displaying the 3D stereoscopic image). 
     Therefore, the broadcast receiver parses a TVCT using the PSI/PSIP processor, and determines whether the 3D broadcast service is provided through the service_type field of the TVCT. 
       FIG. 15  illustrates a table format of a PMT information contained in PSI information of a broadcast signal according to one embodiment of the present invention. 
     Individual fields contained in the PMT shown in  FIG. 15  are as follows. 
     A ‘table_id’ field is an 8-bit field which shall always be set to ‘0x02’ in a ‘TS_program_map_section’ field. 
     A ‘section syntax_indicator’ field is a 1-bit field which shall be set to ‘1’. 
     A ‘section_length’ field is a 12-bit field in which first two bits shall be set to ‘00’, and specifies the number of bytes of the section starting immediately the ‘section_length’ field, and including the CRC. 
     A ‘program_number’ field is a 16-bit field, which specifies the program to which the ‘program_map_PID’ field is applicable. 
     A ‘version_number’ field is a 5-bit field, which indicates the version number of the ‘TS_program_map_section’ field. 
     A ‘current_next_indicator’ field is a 1-bit field. When a bit of the ‘current_next_indicator’ field is set to ‘1’, this means that the transmitted ‘TS_program_map_section’ field is currently applicable. When a bit of the ‘current_next_indicator’ field is set to ‘0’, this means that the transmitted ‘TS_program_map_section’ field is not yet applicable and shall be the next ‘TS_program_map_section’ field to become valid. 
     A ‘section_number’ field includes a value of an 8-bit field which shall be ‘0x00’. 
     A ‘last section_number’ field includes a value of an 8-bit field which shall be ‘0x00’. 
     A ‘PCR_PID’ field is a 13-bit field indicating the PID of the Transport Stream (TS) packets which shall contain the PCR fields valid for the program specified by a ‘program_number’ field. In the case where no PCR is associated with a program definition for private streams, then this field shall take the value of ‘0x1FFF’. 
     A ‘program_info_length’ field is a 12-bit field, the first two bits of which shall be ‘00’. The ‘program_info_length’ field specifies the number of bytes of descriptors immediately following the ‘program_info_length’ field. 
     A ‘stream_type’ field is an 8-bit field specifying the type of elementary stream or payload carried within packets with the PID whose value is specified by the ‘elementary_PID’ field. 
     An ‘elementary_PID’ field is a 13-bit field specifying a PID of the Transport Stream (TS) packets which carry the associated elementary stream or payload. 
     An ‘ES_info_length’ field is a 12-bit field, the first two bits of which shall be ‘00’. The ‘ES_info_length’ field may specify the number of bytes of descriptors of the associated elementary stream immediately following the ‘ES_info_length’ field. 
     A ‘CRC_32’ field is a 32-bit field which contains a CRC value that gives a zero output of registers in the decoder defined in Annex B after processing the entire Transport Stream program map section. 
     The descriptor field  15010  may includes information about video streams constituting a stereoscopic image or 3D broadcast service. 
     The broadcast receiver parses a PMT using the PSI/PSIP processor, and determines whether the 3D broadcast service is provided through at least one of the stream_type field, the elementary_PID field, and the descriptor field. 
     The above-mentioned embodiments may also be applied to the 3D broadcast service of a multi-view image display scheme, instead of the stereoscopic image display scheme. 
     The method disclosed in the present invention may be implemented in the form of program commands executable by a variety of computer means, and recorded on a computer-readable recording medium. The computer-readable recording medium may include program commands, data files, data structures, etc. individually or in combination. The program commands recorded on the medium may be ones specially designed and configured for the present invention or ones known and available to those skilled in computer software. Examples of the computer-readable recording medium include magnetic media such as a hard disk, a floppy disk and a magnetic tape, optical media such as a compact disc read only memory (CD-ROM) and a digital versatile disc (DVD), magneto-optical media such as a floptical disk, and hardware devices specially configured to store and execute program commands, such as a ROM, a random access memory (RAM) and a flash memory. Examples of the program commands include high-level language codes that may be executed by a computer using an interpreter, etc., as well as machine language codes such as those produced by a compiler. The above-stated hardware devices may be configured to operate as one or more software modules to perform the operation of the present invention, and vice versa. 
     Although the present invention has been described in conjunction with the limited embodiments and drawings, the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible from this description. Therefore, the scope of the present invention should not be limited to the description of the exemplary embodiments and should be determined by the appended claims and their equivalents. 
     Mode for the Invention 
     Various embodiments have been described in the best mode for carrying out the invention. 
     INDUSTRIAL APPLICABILITY 
     As apparent from the above description, embodiments of the present invention may be wholly or partially applied to a digital broadcasting system. 
     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. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.