Patent Publication Number: US-7590249-B2

Title: Object-based three-dimensional audio system and method of controlling the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korea Patent Application No. 2002-65918 filed on Oct. 28, 2002 in the Korean Intellectual Property Office, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to an object-based three-dimensional audio system, and a method of controlling the same. More particularly, the present invention relates to an object-based three-dimensional audio system and a method of controlling the same that can maximize audio information transmission, enhance the realism of sound reproduction, and provide services personalized by interaction with users. 
     (b) Description of the Related Art 
     Recently, remarkable research and development has been devoted to three-dimensional (hereinafter referred to as 3-D) audio technologies for personal computers. Various sound cards, multi-media loudspeakers, video games, audio software, compact disk read-only memory (CD-ROM), etc. with 3-D functions are on the market. 
     In addition, a new technology, acoustic environment modeling, has been created by grafting various effects such as reverberation onto the basic 3-D audio technology for simulation of natural audio scenes. 
     A conventional digital audio spatializing system incorporates accurate synthesis of 3-D audio spatialization cues responsive to a desired simulated location and/or velocity of one or more emitters relative to a sound receiver. This synthesis may also simulate the location of one or more reflective surfaces in the receiver&#39;s simulated acoustic environment. 
     Such a conventional digital audio spatializing system has been disclosed in U.S. Pat. No. 5,943,427, entitled “Method and apparatus for three-dimensional audio spatialization”. 
     In the U.S. &#39;427 patent, 3-D sound emitters output from a digital sound generation system of a computer is synthesized and then spatialized in a digital audio system to produce the impression of spatially distributed sound sources in a given space. Such an impression allows a user to have the realism of sound reproduction in a given space, particularly in a virtual reality game. 
     However, since the system of the U.S. &#39;427 patent permits a user to listen to the synthesized sound with the virtual realism, it cannot transmit the real audio contents three-dimensionally on the basis of objects, and interaction with a user is impossible. That is, a user may only listen to the sound. 
     In addition, with respect to U.S. Pat. No. 6,078,669 entitled “Audio spatial localization apparatus and methods,” audio spatial localization is accomplished by utilizing input parameters representing the physical and geometrical aspects of a sound source to modify a monophonic representation of the sound or voice and generate a stereo signal which simulates the acoustical effect of the localized sound. The input parameters include location and velocity, and may also include directivity, reverberation, and other aspects. These input parameters are used to generate control parameters that control voice processing. 
     According to such a conventional computer sound technique, sounds are divided by objects for ‘virtual reality’ game contents, and a parametric method is employed to process 3-D information and space information so that a virtual space may be produced and interaction with a user is possible. Since all the objects are separately processed, the above conventional technique is applicable to a small amount of synthesized object sounds, and the space information has to be simplified. 
     However, in order to utilize natural 3-D audio services, the number of object sounds increases, and the space information requires a lot of information for reality. 
     With respect to Moving Picture Experts Group (MPEG), moving pictures and sounds are encoded on the basis of objects, and additional scene information separated from the moving pictures and sounds is transmitted so that a terminal employing MPEG may provide object-based dialogic services. 
     However, the above conventional technique is based on virtual sound modeling of computer sounds, and, as described above, in order to apply natural 3-D audio services for broadcasting, cinema, and disc production, as well as disc reproduction, the number of sound objects becomes large, and the various means for encoding each object complicate the system architecture. In addition, the conventional virtual sound modeling architecture is too simple to effectively employ the same in a real acoustic environment. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an object-based 3-D audio system and a method of controlling the same that optimizes the number of objects of 3-D sounds, and to permit a user to control a reproduction format of respective object sounds according to his or her preference. 
     In one aspect of the present invention, an object-based three-dimensional (3-D) audio server system comprises: an audio input unit receiving object-based sound sources through various input devices; an audio editing/producing unit separating the sound sources applied through the audio input unit into object sounds and background sounds according to a user&#39;s selection, and converting them into 3-D audio scene information; and an audio encoding unit encoding 3-D information and object signals of the 3-D audio scene information converted by the audio editing/producing unit so as to transmit them through a medium. 
     The audio editing/producing unit includes: a router/audio mixer dividing the sound sources applied in the multi-track format into a plurality of sound source objects and background sounds; a scene editor/producer editing an audio scene and producing the edited audio scene by using 3-D information and spatial information of the sound source objects and background sound objects divided by the router/audio mixer; and a controller providing a user interface so that the scene editor/producer edits an audio scene and produces the edited audio scene under the control of a user. 
     In another aspect of the present invention, a method of controlling an object-based 3-D audio server system comprises: separating sound source objects from among sound sources applied through various means according to selection by a user; inputting 3-D information for each sound source object separated from the applied sound sources; mixing sound sources other than the separated sound source objects into background sounds; and forming the sound source objects, the 3-D information, and the background sound objects into an audio scene, and encoding and multiplexing the audio scene to transmit the encoded and multiplexed audio signal through a medium. 
     In still another aspect of the present invention, an object-based three-dimensional audio terminal system comprises: an audio decoding unit demultiplexing and decoding a multiplexed audio signal including object sounds, background sounds, and scene information applied through a medium; an audio scene-synthesizing unit selectively synthesizing the object sounds with the audio scene information decoded by the audio decoding unit into a 3-D audio scene under the control of a user; a user control unit providing a user interface so as to selectively synthesize the audio scene by the audio scene synthesizing unit under the control of the user; and an audio reproducing unit reproducing the 3-D audio scene synthesized by the audio scene-synthesizing unit. 
     The audio scene-synthesizing unit includes: a sound source object processor receiving the background sound objects, the sound source objects, and the audio scene information decoded by the audio decoding unit to process the sound source objects and audio scene information according to a motion, a relative location between the sound source objects, and a three-dimensional location of the sound source objects, and spatial characteristics under the control of the user; and an object mixer mixing the sound source objects processed by the sound source object processor with the background sound objects decoded by the audio decoding unit to output results. 
     The audio reproducing unit includes: an acoustic environment equalizer equalizing the acoustic environment between a listener and a reproduction system in order to accurately reproduce the 3-D audio transmitted from the audio scene synthesizing unit; an acoustic environment corrector calculating a coefficient of a filter for the acoustic environment equalizer&#39;s equalization, and correcting the equalization by the user; and an audio signal output device outputting a 3-D audio signal equalized by the acoustic environment equalizer. 
     The user control unit includes an interface that controls each sound source object and the listener&#39;s direction and position, and receives the user&#39;s control for maintaining realism of sound reproduction in a virtual space to transmit a control signal to each unit. 
     In still yet another aspect of the present invention, a method of controlling an object-based 3-D audio terminal system comprises: in receiving and outputting an object-based 3-D audio signal, decoding the audio signal applied through a medium and encoded, and dividing the audio signal into object sounds, 3-D information, and background sounds; performing motion processing, group object processing, 3-D sound localization, and 3-D space modeling on the object sounds and the 3-D information to modify and apply the processed object sounds and 3-D information according to a user&#39;s selection, and mixing them with the background sounds; and equalizing the mixed audio signal in response to correction of characteristics of the acoustic environment that the user controls, and outputting the equalized signal so that the user may listen to it. 
     In still yet another aspect of the present invention, an object-based three-dimensional audio system comprises: an audio input unit receiving object-based sound sources through input devices; an audio editing/producing unit separating the sound sources applied through the audio input unit into object sounds and background sounds according to a user&#39;s selection, and converting them into three-dimensional audio objects; an audio encoding unit encoding 3-D information of the audio objects and object signals converted by the audio editing/producing unit to transmit them through a medium; an audio decoding unit receiving the audio signal including object sounds and 3-D information encoded by the audio encoding unit through the medium, and decoding the audio signal; an audio scene synthesizing unit selectively synthesizing the object sounds with 3-D information decoded by the audio decoding unit into a 3-D audio scene under the control of a user; a user control unit outputting a control signal according to the user&#39;s selection so as to selectively synthesize the audio scene by the audio scene synthesizing unit under the control of the user; and an audio reproducing unit reproducing the audio scene synthesized by the audio scene synthesizing unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an object-based 3-D audio system in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is a block diagram of an audio input unit of  FIG. 1 ; 
         FIG. 3  is a block diagram of an audio editing/producing unit of  FIG. 1 ; 
         FIG. 4  is a block diagram of an audio encoding unit of  FIG. 1 ; 
         FIG. 5  is a block diagram of an audio decoding unit of  FIG. 1 ; 
         FIG. 6  is a block diagram of an audio scene-synthesizing unit of  FIG. 1 ; 
         FIG. 7  is a block diagram of an audio reproducing unit of  FIG. 1 ; 
         FIG. 8  depicts a flow chart describing the steps of controlling an object-based 3-D audio server system in accordance with the preferred embodiment of the present invention; and 
         FIG. 9  depicts a flow chart describing the steps of controlling an object-based 3-D audio terminal system in accordance with the preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiment of the present invention will now be fully described, referring to the attached drawings. Like reference numerals denote like reference parts throughout the specification and drawings. 
       FIG. 1  is a block diagram of an object-based 3-D audio system in accordance with a preferred embodiment of the present invention. 
     Referring to  FIG. 1 , the object-based 3-D audio system includes a user control unit  100 , an audio input unit  200 , an audio editing/producing unit  300 , an audio encoding unit  400 , an audio decoding unit  500 , an audio scene-synthesizing unit  600 , and an audio reproducing unit  700 . 
     The audio input unit  200 , the audio editing/producing unit  300 , and the audio encoding unit  400  are included in an input system that receives 3-D sound sources, process them on the basis of objects, and transmits an encoded audio signal through a medium, while the audio decoding unit  500 , the audio scene synthesizing unit  600 , and the audio reproducing unit  700  are included in an output system that receives the encoded signal through the medium, and outputs object-based 3-D sounds under the control of a user. 
     The construction of the audio input unit  200  that receives various sound sources in the object-based 3-D input system is depicted in  FIG. 2 . 
     Referring to  FIG. 2 , the audio input unit  200  includes a single channel microphone  210 , a stereo microphone  230 , a dummy head microphone  240 , an ambisonic microphone  250 , a multi-channel microphone  260 , and a source separation/3-D information extractor  220 . 
     In addition to the microphones depicted in  FIG. 2  according to the preferred embodiment of the present invention, the audio input unit  200  may have additional microphones for receiving various audio sound sources. 
     The single channel microphone  210  is a sound source input device having a single microphone, and the stereo microphone  230  has at least two microphones. The dummy head microphone  240  is a sound source input device whose shape is like a head of a human body, and the ambisonic microphone  250  receives the sound sources after dividing them into signals and volume levels, each moving with a given trajectory on 3-D X, Y, and Z coordinates. The multi-channel microphone  260  is a sound source input device for receiving audio signals of a multi-track. 
     The source separation/3-D information extractor  220  separates the sound sources that have been applied from the above sound source input devices by objects, and extracts 3-D information. 
     The audio input unit  200  separates sounds that have been applied from the various microphones into a plurality of object signals, and extracts 3-D information from the respective object sounds to transmit the 3-D information to the audio editing/producing unit  300 . 
     The audio editing/producing unit  300  produces given object sounds, background sounds, and audio scene information under the control of a user by using the input object signals and 3-D information. 
       FIG. 3  is a block diagram of the audio editing/producing unit  300  of  FIG. 1  according to the preferred embodiment of the present invention. 
     Referring to  FIG. 3 , the audio editing/producing unit  300  includes a router/3-D audio mixer  310 , a 3-D audio scene editor/producer  320 , and a controller  330 . 
     The router/3-D audio mixer  310  divides the object information and 3-D information that have been applied from the audio input unit  200  into a plurality of object sounds and background sounds according to a user&#39;s selection. 
     The 3-D audio scene editor/producer  320  edits audio scene information of the object sounds and background sounds that have been divided by the router/3-D audio mixer  310  under the control of the user, and produces edited audio scene information. 
     The controller  330  controls the router/3-D audio mixer  310  and the 3-D audio scene editor/producer  320  to select 3-D objects from among them, and controls audio scene editing. 
     The router/3-d audio mixer  310  of the audio editing/producing unit  300  divides the audio object information and 3-D information that have been applied from the audio input unit  200  into a plurality of object sounds and background sounds according to the user&#39;s selection to produce them, and processes the other audio object information that has not been selected into background sound. In this instance, the user may select object sounds through the controller  330 . 
     The 3-D audio scene editor/producer  320  forms a 3-D audio scene by using the 3-D information, and the controller  330  controls a distance between the sound sources or relationship of the sound sources and background sounds by a user&#39;s selection to edit/produce the 3-D audio scene. 
     The edited/produced audio scene information, the object sounds, and the background sound information are transmitted to the audio encoding unit  400  and converted by the audio encoding unit  400  to be transmitted through a medium. 
       FIG. 4  is a block diagram of the audio encoding unit  400  of  FIG. 1  according to the preferred embodiment of the present invention. 
     Referring to  FIG. 4 , the audio encoding unit  400  includes an audio-object encoder  410 , an audio scene information encoder  420 , a background-sound encoder  430 , and a multiplexer  440 . 
     The audio object encoder  410  encodes the object sounds transmitted from the audio editing/producing unit  300 , and the audio scene information encoder  420  encodes the audio scene information. The background sound encoder  430  encodes the background sounds. The multiplexer  440  multiplexes the object sounds, the audio scene information, and the background sounds respectively encoded by the audio object encoder  410 , the audio scene information encoder  420 , and the background sound encoder  430  in order to transmit the same as a single audio signal. 
     As described above, the object-based 3-D audio signal is transmitted via a medium, and a user may input and transmit sound sources, considering his or her purpose of listening to the audio signal, and his or her characteristics and acoustic environment. 
     The following description concerns an object-based 3-D audio output system that receives the audio signal and outputs it. 
     In order to receive the audio signal transmitted through the medium and provide the same to a listener, the audio decoding unit  500  of the 3-D audio output system first decodes the input audio signal. 
       FIG. 5  is a block diagram of the audio decoding unit  500  of  FIG. 1  according to the preferred embodiment of the present invention. 
     Referring to  FIG. 5 , the audio decoding unit  500  includes a demultiplexer  510 , an audio object decoder  520 , an audio scene information decoder  530 , and a background sound object decoder  540 . 
     The demultiplexer  510  demultiplexes the audio signal applied through the medium, and separates the same into object sounds, scene information and background sounds. 
     The audio object decoder  520  decodes the object sounds separated from the audio signal by the demultiplexing, and the audio scene information decoder  530  decodes the audio scene information. The background sound object decoder  540  decodes the background sounds. 
     The audio scene-synthesizing unit  600  synthesizes the object sounds, the audio scene information, and the background sounds decoded by the audio decoding unit  500  into a 3-D audio scene. 
       FIG. 6  is a block diagram of the audio scene-synthesizing unit  600  of  FIG. 1  according to the preferred embodiment of the present invention. 
     Referring to  FIG. 6 , the audio scene-synthesizing unit  600  includes a motion processor  610 , a group object processor  620 , a 3-D sound image localization processor  630 , a 3-D space modeling processor  640 , and an object mixer  650 . 
     The motion processor  610  successively updates location coordinates of each object sound moving with a particular trajectory and velocity relative to a listener, and when there is the listener&#39;s control, the group object processor  620  updates location coordinates of a plurality of sound sources relative to the listener in a group according to his or her control. 
     The 3-D sound image localization processor  630  has different functions according to a reproduction environment, i.e., the configuration and arrangement of loudspeakers. When two loudspeakers are used for sound reproduction, the 3-D sound image localization processor  630  employs a head related transfer function (HRTF) to perform sound image localization, and in the case of using a multi-channel microphone, the 3-D sound image localization processor  630  performs the sound image localization by processing the phase and level of loudspeakers. 
     The 3-D space modeling processor  640  reproduces spatial effects in response to the size, shape, and characteristics of an acoustic space included in the 3-D information, and individually processes the respective sound sources. 
     In this instance, the motion processor  610 , the group object processor  620 , the 3-D sound image localization processor  630 , and the 3-D space modeling processor  640  may be under the control of a user through the user control unit  100 , and the user may control processing of each object and space processing. 
     The object mixer  650  mixes the objects and background sounds respectively processed by the motion processor  610 , the group object processor  620 , the 3-D sound image localization processor  630 , and the 3-D space modeling processor  640  to output them to a given channel. 
     The audio scene-synthesizing unit  600  naturally reproduces the 3-D audio scene produced by the audio editing/producing unit  300  of the audio input system. In case of need, the user control unit  100  controls 3-D information parameters of the space information and object sounds to allow a user to change 3-D effects. 
     The audio reproducing unit  700  reproduces an audio signal that the audio scene-synthesizing unit  600  has transmitted after processing and mixing the object sounds, the background sounds, and the audio scene information with each other so that a user may listen to it. 
       FIG. 7  is a block diagram of the audio reproducing unit  700  of  FIG. 1  according to the preferred embodiment of the present invention. 
     The audio reproducing unit  700  includes an acoustic environment equalizer  710 , an audio signal output device  720 , and an acoustic environment corrector  730 . 
     The acoustic environment equalizer  710  applies an acoustic environment in which a user is going to listen to sounds at the final stage to equalize the acoustic environment. 
     The audio signal output device  720  outputs an audio signal so that a user may listen to the same. 
     The acoustic environment corrector  730  controls the acoustic environment equalizer  710  under the user&#39;s control, and corrects characteristics of the acoustic environment to accurately transmit signals, each output through the speakers of the respective channels, to the user. 
     More specifically, the acoustic environment equalizer  710  normalizes and equalizes characteristics of the reproduction system so as to more accurately reproduce 3-D audio signals synthesized in response to the architecture of loudspeakers, characteristics of the equipment, and characteristics of the acoustic environment. In this instance, in order to exactly transmit desired signals and output them through the speakers of the respective channels to a listener, the acoustic environment corrector  730  includes an acoustic environment correction and user control device. 
     The characteristics of the acoustic environment may be corrected by using a crosstalk cancellation scheme when reproducing audio signals in binaural stereo. In the case of using a multi-channel microphone, characteristics of the acoustic environment may be corrected by controlling the level and delay of each channel. 
     In the object-based 3-D audio output system, the user control unit  100  either corrects the space information of the 3-D audio scene through a user interface to control sound effects, or controls 3-D information parameters of the object sounds to control the location and motion of the object sounds. 
     In this instance, a user may properly form the 3-D audio information into a desired 3-D audio scene, monitoring the presently controlled situation by using the audio-visual information, or may reproduce only a special object or cancel the reproduction. 
     According to the preferred embodiment of the present invention, the object-based 3-D audio system provides the user interface by using 3-D audio information parameters to allow the blind with a normal sense of hearing to control an audio/video system, and more definitely controls the acoustic impression on the reproduced scene, thereby enhancing the understanding of the scene. 
     The object-based 3-D audio system of the present invention permits a user to appreciate a scene at a different angle and on a different position with video information, and may be applied to foreign language study. In addition, the present invention may provide users with various control functions such as picking out and listening to only the sound of a certain musical instrument when listening to a musical performance, e.g., a violin concerto. 
     The method of controlling the object-based 3-D audio system will now be described in detail. 
       FIG. 8  depicts a flow chart describing the steps of controlling an object-based 3-D audio server system in accordance with the preferred embodiment of the present invention 
     Referring to  FIG. 8 , when various sound sources are applied to the system through a plurality of microphones (S 801 ), a user selects object sounds from among the input sound sources (S 802 ), and inputs 3-D information for each object sound (S 803 ) to the system. 
     The user properly controls the object sounds and 3-D information and selects the object sounds, considering the purpose of using them, his or her characteristics, and characteristics of the acoustic environment. The other sound sources that the user has not selected as object sounds are processed into background sounds. By way of example, a speaker&#39;s voice may be selected as object sounds from among sound sources, so as to allow a listener to carefully listen to the native speaker&#39;s pronunciation. The other sound sources that the listener has not selected are processed into background sounds. In this manner, the listener may select only the native speaker&#39;s voice and pronunciation as object sounds while excluding other background sounds, to use the native speaker&#39;s pronunciation for foreign language study. 
     The audio scene editing/producing unit  300  edits and produces the object sounds, the 3-D information, and the background sounds that have been controlled in the steps S 802  and S 803  into a 3-D audio scene (S 804 ), and the audio encoding unit  400  respectively encodes and multiplexes the object sounds, the audio scene information, and the background sounds (S 805 ) to transmit them through a medium (S 806 ). 
     The following description is about the method of receiving audio data transmitted as object-based 3-D sounds, and reproducing the same. 
       FIG. 9  depicts a flow chart describing the steps of controlling an object-based 3-D audio terminal system in accordance with the preferred embodiment of the present invention. 
     Referring to  FIG. 9 , when audio signals are applied through the medium to the audio decoding unit  500  (S 901 ), the audio decoding unit  500  demultiplexes the input audio signals to separate them into object sounds, audio scene information, and background sounds, and decodes each of them (S 902 ). 
     The audio scene-synthesizing unit  600  synthesizes the decoded object sounds, audio scene information, and background sounds into a 3-D audio scene. In this instance, a listener may select object sounds according to his or her purpose of listening, and may either keep or remove the selected object sounds or control the volume of the object sounds (S 903 ). 
     In the step S 903  of processing each object sound into an audio signal by the audio scene-synthesizing unit  600 , the user controls the 3-D information through the user control unit  100  (S 904 ) to enhance the stereophonic sounds or produce special effects in response to an acoustic environment. 
     As described above, when the user has selected the object sounds and controlled the 3-D information through the user control unit  100 , the audio scene synthesizing unit  600  synthesizes them into an audio scene with background sounds (S 905 ), and the user controls the acoustic environment corrector  730  of the audio reproducing unit  700  to modify or input the acoustic environment information in response to the characteristics of the acoustic environment (S 906 ). 
     The acoustic environment equalizer  710  of the audio system equalizes audio signals that have been output in response to the acoustic environment&#39;s characteristics under the user&#39;s control (S 907 ), and the audio reproducing unit  700  reproduces them through loudspeakers (S 908 ) so as to let the user listen to them. 
     As described above, since the audio input/output system of the present invention allows a user to select an object of each sound source and arbitrarily input 3-D information to the system, it may be controlled in response to the functions of audio signals and a human listener&#39;s acoustic environment. Thus, the present invention may produce more dramatic audio effects or special effects and enhance the realism of sound reproduction by modifying the 3-D information and controlling the characteristics of the acoustic environment. 
     In conclusion, according to the object-based 3-D audio system and the method of controlling the same, a user may control the selection of sound sources based on objects and edit the 3-D information in response to his or her purpose of listening and characteristics of an acoustic environment so that he or she can selectively listen to desired audio. In addition, the present invention can enhance the realism of sound production and produce special effects. 
     While the present invention has been described in connection with what is considered to be the preferred embodiment, it is to be understood that the present invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modification and equivalent arrangements included within the spirit and scope of the appended claims.