Abstract:
A method of generating and recovering three-dimensional (3D) compression data, and an apparatus to perform the methods, the method of generating the 3D compression data including generating configuration information of a 3D compression data sequence; generating a plurality of pieces of individual 3D compression data to be included in the 3D compression data sequence; and generating the 3D compression data sequence by combining the plurality of pieces of the individual 3D compression data, combining the 3D compression data sequence with the configuration information, and outputting the combined result; wherein the generating of each of the plurality of pieces of individual 3D compression data comprises: generating individual configuration information of the piece of individual 3D compression data, generating a start code according to a data type of the piece of individual 3D compression data, and generating the 3D compression data according to the data type.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/669,927, filed on Apr. 11, 2005, and U.S. Provisional Application No. 60/676,972, filed on May 3, 2005, in the United States Patent &amp; Trademark Office, the disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method of generating three-dimensional (3D) graphic compression data, and an apparatus to perform the method, and a method of recovering 3D graphic compression data, and an apparatus to perform the method, and, more particularly, to a method of generating 3D graphic compression data, and an apparatus to perform the method, and a method of recovering 3D graphic compression data, and an apparatus to perform the method, in a mobile environment.  
         [0004]     2. Description of the Related Art  
         [0005]     The current state of the evolution of mobile devices allows some services, such as 3D games, 3D avatars, or 3D shopping, which were previously considered to be impossible or impractical in a mobile environment, to be provided. As a result, such services have been recognized as new business models to be used in mobile communications or content providers.  
         [0006]     However, the mobile devices are limited in terms of computational complexity and power consumption, and a bandwidth of a wireless network is also limited. Thus, an efficient method of representing and compressing 3D graphic data is needed to overcome these limitations in a mobile environment.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides a method of generating three-dimensional (3D) graphic compression data, and an apparatus to perform the method, and a method of recovering 3D graphic compression data, and an apparatus to perform the method, in order to compactly represent the 3D graphic data and effectively transmit the data via a wireless network in a mobile environment that is restricted in power consumption and computational complexity.  
         [0008]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.  
         [0009]     According to an aspect of the present invention, there is provided a method of generating three-dimensional (3D) compression data, the method comprising generating configuration information of a 3D compression data sequence; generating a plurality of pieces of individual 3D compression data to be included in the 3D compression data sequence; and generating the 3D compression data sequence by combining the plurality of pieces of the individual 3D compression data, combining the 3D compression data sequence with the configuration information, and outputting the combining result, wherein the generating of each of the plurality of pieces of individual 3D compression data comprises generating individual configuration information of the piece of individual 3D compression data; generating start code according to a data type of the piece of individual 3D compression data; and generating the 3D compression data according to the data type.  
         [0010]     According to another aspect of the present invention, there is provided a method of recovering three-dimensional (3D) compression data, the method comprising separating a 3D compression data sequence and configuration information of the 3D compression data sequence from a received signal; separating a plurality of pieces of individual 3D compression data and individual configuration information for each of the pieces of individual 3D compression data from the 3D compression data sequence; separating each start code from the pieces of individual 3D compression data according to a data type of each of the pieces of individual 3D compression data; and decoding the pieces of individual 3D compression data using the data type included in the individual configuration information.  
         [0011]     According to another aspect of the present invention, there is provided an apparatus to generate three-dimensional (3D) compression data, the apparatus comprising an encoder which generates different pieces of individual 3D compression data by encoding received 3D data according to a data type of the 3D data, generates a 3D compression data sequence by generating individual configuration information for each of the pieces of individual 3D compression data and combining the configuration information with the corresponding piece of individual 3D compression data, respectively, generates configuration information of the 3D compression data sequence, combines the configuration information with the 3D compression data sequence, and outputs the combining result; wherein, prior to the generation of the pieces of individual 3D compression data, the encoder generates a start code according to a data type of the pieces of individual 3D compression data.  
         [0012]     According to another aspect of the present invention, there is provided an apparatus to recover three-dimensional (3D) compression data from a received signal, the apparatus comprising a decoder which separates a 3D compression data sequence and configuration information of the 3D compression data sequence from the received signal; separates a plurality of pieces of individual 3D compression data and individual configuration for each of the pieces of individual 3D compression data from the 3D compression data sequence; analyzes a data type code comprising information of a data type of the pieces of individual 3D compression data, which is included in the individual configuration information; and decodes the pieces of individual 3D compression data according to the data type code; wherein the decoder separates start code from the pieces of individual 3D compression data according to the data type.  
         [0013]     According to another aspect of the present invention, there is provided a method of generating three-dimensional (3D) compression data, the method comprising generating configuration information of 3DCObjectSequence, which is the 3D compression data; generating 3DCObjects, which are a plurality of pieces of individual 3D compression data and are included in the 3D compression data; and generating a 3D compression data sequence by combining the plurality of pieces of individual 3D compression data, combining the 3D compression data sequence with configuration information of the 3D compression data sequence, and outputting the combining result. The generation of the pieces of individual 3D compression data comprises generating individual configuration information of the respective pieces of individual 3D compression data; generating start code according to a data type of the respective pieces of individual 3D compression data; and generating the 3D compression data according to the data type. The generation of the pieces of individual 3D compression data is realized by:  
                                                     3DCObject( ) {              3dc_object_start_code              is_3dc_object_identifier             if(is_3DC_object_identifier){              3dc_object_verid              3dc_object_priority             }             3dc_object_type_indication             next_start_code( )             if (3dc_object_type_indication == “Simple_3DMC”) {              3D_Mesh_Object( )             }             else if (3dc_object_type_indication == “Simple_WSSI”) {              WSS_start_code              Wavelet_Mesh_Object( )             }             else if (3dc_object_type_indication == “Main_CI”) {              CoordIC_start_code              CompressedCoordinateInterpolator( )             }             else if (3dc_object_type_indication == “Main_OI”) {              OriIC_start_code              CompressedOrientationInterpolatort( )             }             else if (3dc_object_type_indication == “Main_PI”) {              PosIC_start_code              CompressedPositionInterpolator( )             }             else if (3dc_object_type_indication == “Simple_BBA”)             {              bba_object( )             }            (more object types and corresponding decoders can be defined.)             if (next_bits( ) != “000 0000 0000 0000 0000 0001”              next_start_code( )           },                      
 
 wherein 3dc_object_start_code denotes code representing start of 3DCObject, is — 3dc_object_identifier denotes an identifier of the 3DCObject, 3dc_object_verid denotes code representing identification of a version of the 3DCObject, 3dc_object_priority denotes code representing priority of the 3DCObject, 3dc_object_type_indication denotes a type of the individual 3D compression data, WSS_start_code, CoordIC_start_code, OriIC_start_code, and PosIC_start_code are start codes for data types, respectively.
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0015]      FIG. 1  is a schematic block diagram illustrating a three-dimensional (3D) graphic system according to an embodiment of the present invention;  
         [0016]      FIG. 2  is a diagram illustrating a structure of compression data according to an MPEG-4 profile based on an MPEG-4 system;  
         [0017]      FIG. 3  is a diagram illustrating a structure of a 3D compression data stream according to an embodiment of the present invention;  
         [0018]      FIG. 4  is a diagram illustrating a multiplexed bit stream output from an AFX encoder illustrated in  FIG. 1 ;  
         [0019]      FIG. 5A  is a diagram illustrating an example of a scene; and  
         [0020]      FIG. 5B  is a graph illustrating the structure of objects included in the scene illustrated in  FIG. 5A . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.  
         [0022]      FIG. 1  is a schematic block diagram illustrating a three-dimensional (3D) graphic system according to an embodiment of the present invention. 3D graphics may include mobile 3D applications, such as, for example, a 3D game, a 3D graphic user interface (GUI), or a 3D avatar. Referring to  FIG. 1 , the system includes a 3D graphic authoring device  10  and a 3D graphic operation device  11 .  
         [0023]     The 3D graphic authoring device  10  includes an authoring tool  101 , an application implementation unit  102 , and an AFX (Animation Framework eXtension) encoder  103 .  
         [0024]     The authoring tool  101  creates 3D resources. The 3D resources may include, for example, a 3D mesh, a key-frame sequence, or bone information.  
         [0025]     The application implementation unit  102  outputs scene graph information used to display content stored in a data structure in a screen according to, for example, a user&#39;s input, an interaction with a user, scene management, Open GL, which is a graphic library, and GFX or DirectX, which are application program interfaces.  
         [0026]     The AFX encoder  103  compresses some of the 3D resources from the authoring tool  101 , or the information from the application implementation unit  102 , and transmits the compression result.  
         [0027]     The 3D graphic operation device  11  includes an application execution unit  111  and an AFX decoder  112 .  
         [0028]     The AFX decoder  112  recovers 3D data by decoding input compression data according to the type of the data.  
         [0029]     The application execution unit  111  receives and executes the information from the application implementation unit  102 , or executes the 3D resources recovered by the AFX decoder  112 .  
         [0030]      FIG. 2  is a diagram illustrating a structure of compression data according to an MPEG-4 profile based on an MPEG-4 system. Referring to  FIG. 2 , according to the specification of a system part of the ISO/IEC (International Organization for Standardization/lnternational Electrotechnical Commission) 14496-1, an MPEG-4 system (not shown) inserts an object descriptor  22 , which describes the characteristics of a media object (audio or video) and the characteristics of an elementary stream, into an elementary stream  21  comprised of access units (AUs). Configuration information  23  is inserted into the object descriptor  22 .  
         [0031]     The specification of the system part of the ISO/IEC 14496-1 specifies separate encoding of video data and audio data, and multiplexing and synchronizing of the encoded data in order to store multimedia data in a file or a recording medium or transmit it via a network. It is an MPEG-4 system that defines the data multiplexing. Video or audio binary data that has yet to be multiplexed by the system is referred to as the elementary stream.  
         [0032]     In the MPEG-4 standard, object encoding is used to multiplex audio and video data. In this case, both audio data and video data are processed as a single object, and the system multiplexes and synchronizes the objects.  
         [0033]     The MPEG-4 standard defines BIFS (Binary Format for Scenes) as a feature used in a scene description by combining and processing a plurality of objects. For example, moving picture data and audio data of a person or a background are encoded as separate objects. Thus, an application can be made, so that the encoded objects are displayed to overlap each other, or a user can move any object.  
         [0034]     However, when an application is downloaded and stored by using most basic tools in a mobile environment, the profile illustrated in  FIG. 2  is tightly coupled with an MPEG-4 system having a BIFS structure. That is, the profile is inefficient since the MPEG-4 system must be prepared to decode a bitstream encoded by an MPEG-4 AFX tool, thereby increasing the load on the hardware.  
         [0035]     Therefore, in an embodiment of the present invention, a 3D compression profile that does not require an MPEG-4 system is adopted. In 3D compression data according to an embodiment of the present invention, configuration information, i.e., header information of an object, is inserted into a start of a bitstream, and, optionally, repeatedly inserted into the bitstream after the start of the bitstream.  
         [0036]      FIG. 3  is a diagram illustrating a structure of a 3D compression data stream according to an embodiment of the present invention. Referring to  FIG. 3 , an elementary system includes objects, each having a plurality of access units, and configuration information Cfg of each object.  
         [0037]     The data structure illustrated in  FIG. 3  is obtained by making objects by encoding 3D data by the AFX encoder  103  of  FIG. 1  according to the types of the objects, and inserting configuration information into the corresponding objects and multiplexing the objects by the AFX encoder  103 . Here, the types of the objects include 3D mesh coding (3DMC), interpolator coding (IC), a coordinate interpolator (CI), an orientation interpolator (OC), a wavelet subdivision surface (WSS), a position interpolator (PI), and bone-based animation (BBA), which are suggested in the MPEG-4 standard.  
         [0038]      FIG. 4  is a diagram illustrating a data structure of a multiplexed bitstream output from the AFX encoder  103  of  FIG. 1 . The illustrated bitstream includes a 3DCObjectSequence header  51  and a 3DCObjectSequence  52 . The 3DCObjectSequence header  51 , which is generated by the AFX encoder  103 , includes a profile and level indication of the bitstream. Also, the 3DCObjectSequence header  51  may further include user data defined for a specific application by a user, e.g., scene graph information for the bitstream, which will be described in detail with reference to  FIGS. 5A and 5B .  
         [0039]      FIG. 5A  is a diagram illustrating an example of a scene.  FIG. 5B  is a graph illustrating the structure of objects included in the scene illustrated in  FIG. 5A . Referring to  FIG. 5A , the scene includes objects  1  through  3  defined in world coordinates  61 , and the object  3  includes detailed objects  3 - 1 ,  3 - 2 , and  3 - 3 . For example, the objects  1  through  3  may be a building, a tree, and a chair, respectively, and the detailed objects  3 - 1  through  3 - 3  of the object  3  may respectively be a ball on the chair and the legs of the chair.  
         [0040]     The scene illustrated in  FIG. 5A  may be represented as graph information as illustrated in  FIG. 5B . Referring to  FIG. 5B , the world coordinates  61  are linked to objects  1  through  3 , and the object  3  is linked to detailed objects  3 - 1 ,  3 - 2 , and  3 - 3 .  
         [0041]     The scene graph information illustrated in  FIGS. 5A and 5B  may be included as user data in the 3DCObjectSequence header  51  of  FIG. 4 . For example, the objects  1  through  3 , linked to the world coordinates  61 , may be included in the user data as the objects for configuring a scene, e.g., a building, a tree, and a chair, and the detailed objects  3 - 1  through  3 - 3 , which comprise the chair  3 , may also be included in the user data as a ball on the chair and the legs of the chair, respectively.  
         [0042]     The 3D compression object 3DCObjectSequence  52  includes a plurality of 3DCObject headers  521 , and a plurality of individual 3DCObjects  522 . Here, each of the 3DCObjects  522  is a 3D compression bitstream, such as, for example, a 3DMC Simple — 3DMC, IC (not shown), BBA Simple_BBA, WSS (not shown), or PI Simple_PI, which is encoded by the AFX encoder  103 .  
         [0043]     The 3DCObject header  521  includes a “3dc_object_verid” field describing the version number of a tool list of a 3D compression object type, and a “3dc_object_type_indication” field that is used in resynchronization and describes the object type of a 3D compression stream to be transmitted and the type of a decoder matching the 3D compression stream. For example, if the “3dc_object_type_indication” field is a “Simple — 3DMC” field, the AFX decoder  112  analyzes the “3dc_object_type_indication” field and decodes the 3D compression stream according to a decoding method matching the 3DMC object. Even if more AFX tools and functions are adopted in the tool list of a 3D compression object type, the data structure according to the present invention can be extended by defining further object types in the “3dc_object_type_indication” field in the following syntax.  
         [0044]     The 3DCObject header  521  may further include user data that a user defines for a specific application for the 3D compression object. For example, in  FIGS. 5A and 5B , a building, a tree, and a chair may be included in a 3DCObject header  1 , a 3DCObject header  2 , and a 3DCObject header  3 , respectively.  
         [0045]     The syntax of a process of generating a 3D compression object sequence is as follows:  
                                                   3DCObjectSequence( ) {           3dc_object_sequence_start_code           Profile_and_level_indication           while (next_bits( )== user_data_start_code){             user_data( )           }           do {             3DCObject( )           } while ( next_bits( ) != 3dc_object_sequence_end_code)           3dc_object_sequence_end_code           }                      
 
         [0046]     In the above code, 3dc_object sequence start_code is a hexadecimal number system of a bit string ‘000001C0’, and starts a 3D compression session. In this case, the Mnemonic is bslbf. The Mnemonic describes the type of data available for a coded bitstream, and bslbf stands for a bit string, left bit first.  
         [0047]     Profile_and_level_indication is an 8-bit integer used to signal the profile and level identification of the bitstream, and the meaning of each bit value is indicated in the following table:  
                           TABLE 1                                   Profile/Level   Code                           reserved   00000000           Simple profile/level 1   00000001           Simple profile/level 2   00000010           reserved   00000011           .   .           .   .           .   .           reserved   11111111                      
 
         [0048]     In this case, the mnemonic is uimsbf, which stands for unsigned integer, most significant bit first.  
         [0049]     3dc_object_sequence_end_code is a hexadecimal number system of a bit string ‘000001C1’, and ends the 3D compression session. In this case, the mnemonic is bslbf.  
         [0050]     To generate the 3D compression object sequence, when the 3D compression session starts, user data is generated according to a given profile and level during a period of time in which a next bit is user_data start_code, and 3DCObject is generated during a period of time in which a next bit is not 3dc_object_sequence_end_code.  
         [0051]     The syntax of a process of generating the 3D compression object is as follows:  
                                    3DCObject( ) {        3dc_object_start_code        is_3dc_object_identifier        if(is_3DC_object_identifier){          3dc_object_verid          3dc_object_priority        }        3dc_object_type_indication        next_start_code( )       while ( next_bits( )== user_data_start_code){          user_data( )        }        if (3dc_object_type_indication == “Simple_3DMC”) {          3D_Mesh_Object( )        }        else if (3dc_object_type_indication == “Simple_WSSI”) {         WSS_start_code         Wavelet_Mesh_Object( )        }        else if(3dc_object_type_indication == “Main_CI”) {         CoordIC_start_code         CompressedCoordinateInterpolator( )        }        else if (3dc_object_type_indication == “Main_OI”) {         OriIC_start_code         CompressedOrientationInterpolatort( )        }        else if (3dc_object_type_indication == “Main_PI”) {         PosIC_start_code         CompressedPositionInterpolator( )        }        else if (3dc_object_type_indication == “Simple_BBA”)        {         bba_object( )        }        (more object types and corresponding decoders may further be defined        here)        if (next_bits( ) != “000 0000 0000 0000 0000 0001”         next_start_code( )       }                  
 
         [0052]     In the above code, 3dc_object_start_code is a hexadecimal number system of a bit string ‘000001A2’, and starts a 3D compression object. In this case, the mnemonic is bslbf.  
         [0053]     is — 3dc_object_identifier is a 1-bit code, and set to ‘1’ when the version identification and priority of a 3D compression object are defined. In this case, the mnemonic is uimsbf.  
         [0054]     3dc_object_verid is a 4-bit code that represents the version number of the 3D compression object. The meanings of the bit values are shown in the following table. If 3dc_object_verid does not exist, the value of 3dc_object_verid is ‘0001’. In this case, the mnemonic is uimsbf.  
                   TABLE 2                       3dc_object_verid   Meaning                   0000   reserved       0001   object type listed in Table 3       0010-1111   reserved                  
 
         [0055]     Table 3 shows a tool list included in each object type. Current object types may be extended until new tools or functionalities are introduced.  
                                                         TABLE 3                                       3D Compression Object Type                Simple   Simple                           AFX Tool   3DMC   CI   Simple PI   Simple OI   Simple WSS   Simple BBA   reserved               3DMC   X                               CI       X       PI           X       OI               X       WSS                   X       BBA                       X       reserved                  
 
         [0056]     In Table 3, “3DMC” stands for 3D Mesh Compression, “CI” stands for Coordinate Interpolator, “PI” stands for Position Interpolator, “OI” stands for Orientation Interpolator, and “WSS” stands for Wavelet Subdivision Surface.  
         [0057]     3dc_object_priority is a 3-bit code representing the priority of the 3D compression object. 3dc_object_priority has a value between 1 and 7. Here, ‘1’ represents the highest priority, and ‘7’ represents the lowest priority. ‘0’ is a reserved value. In this case, the mnemonic is uimsbf.  
         [0058]     3dc_object_type_indication is a code that indicates the type of the 3D object, is comprised of a 32-bit bit string, and the mnemonic of which is bslbf. The 3dc_object_type_indication is used to limit the subsequent bitstreams to use a tool according to the indicated object type. According to the value of the 3dc_object_type_indication, a corresponding decoder is called and the compressed bit stream is decoded. Object types are listed in Table 3, and object types to be further added can be reflected in Table 4.  
                           TABLE 4                                   3D Compression Object Type   Code                           reserved   00000000           Simple 3DMC   00000001           Simple CI   00000010           Simple PI   00000011           Simple OI   00000100           Simple WSS   00000101           Simple BBA   00000110           reserved   00000111 . . . 11111111                      
 
         [0059]     To generate the 3D object, when a session starts, user data is generated according to the version and priority of the 3D compression object during a period of time in which a next bit is user_data_start_code. Next, an object is generated according to the type of the corresponding 3D object.  
         [0060]     The syntax of a process of generating the user data is as follows:  
                                                   user_data( ) {            user_data_start_code            while( next_bits( ) != “000 0000 0000 0000 0000 0001”) {             user_data            }           }                      
 
         [0061]     user_data_start_code is a hexadecimal number system of a bit string ‘000001B2’, and indicates the start of the user data. The user data is continuously generated until another start code is received. In this case, the mnemonic is bslbf.  
         [0062]     user_data is an 8-bit integer that is defined for a specific application by a user. If there are a series of user_data bytes, a bit string of 23 or more consecutive ‘0’s is not allowed.  
         [0063]     3D_Mesh_Object() or Wavelet_Mesh_Object( ) is a function of generating compression data according to the type of data, e.g., 3D mesh compression or wavelet subdivision surface. In an embodiment of the present invention, a start code according to the type of data is further generated to the start of compression data prior to generation of the compression data according to the type of data. 3D_Mesh_Object( ) and bba_object( ) do not have the start code because they include the start code inside them.  
         [0064]     In addition to the above-described embodiments, the method of the present invention can also be implemented by executing computer readable code/instructions in/on a medium, e.g., a computer readable medium. The medium can correspond to any medium/media permitting the storing and/or transmission of the computer readable code. The code/instructions may form a computer program.  
         [0065]     The computer readable code/instructions can be recorded/transferred on a medium in a variety of ways, with examples of the medium including magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.), optical recording media (e.g., CD-ROMs, or DVDs), and storage/transmission media such as carrier waves, as well as through the Internet, for example. The medium may also be a distributed network, so that the computer readable code/instructions is stored/transferred and executed in a distributed fashion. The computer readable code/instructions may be executed by one or more processors.  
         [0066]     As described above, according to the present invention, in a mobile environment being limited in power consumption and computational complexity, it is possible to effectively compress 3D graphic data and transmit the compressed 3D graphic data via a wireless network without an MPEG-4 system.  
         [0067]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.