Patent Publication Number: US-2011054917-A1

Title: Apparatus and method for structuring bitstream for object-based audio service, and apparatus for encoding the bitstream

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2009-0080683, filed on Aug. 28, 2009, and Korean Patent Application No. 10-2009-0127946, filed on Dec. 21, 2009, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a method and apparatus for structuring a bitstream for an object-based audio service, and an apparatus for encoding the bitstream, and more particularly, to a method and apparatus for effectively providing an object-based audio service by including, in a bitstream, information associated with an upper bound value and a lower bound value when reproducing a sound source with a low quality. 
     2. Description of the Related Art 
     An audio signal provided using a broadcasting service such as TV broadcasting, radio broadcasting, Digital Multimedia Broadcasting (DMB), and the like may be mixed with other audio object obtained from various sound sources and thereby be stored and be transmitted as a single audio signal. In this environment, a user may adjust the volume of entire audio object and the like, whereas the user may not control a characteristic of an each sound object. For example, the user may not adjust volume of each sound source included in the transmitted single audio signal. In a content creation, when individually storing each sound object instead of mixing the audio object, the user may listen while controlling the volume of each sound object, and the like in a terminal. As described above, an audio service that enables the user to listen with appropriately controlling each audio object in a receiver, in such a manner that a storage end and a transmission end may individually store and transmit a plurality of audio object is referred to as an object-based audio service. 
     A sound source separation technology denotes a technology that may extract audio objects such as a vocal, a drum, and the like from a sound source, down mixed to stereo and the like, using various types signal processing schemes. Accordingly, in the case of using the sound source separation technology, even though a corresponding sound signal includes a plurality of audio object that are down mixed in existing various stereo types, it is possible to extract, from the corresponding sound source, various types of sound object such as vocal, drum, piano, and the like. Accordingly, it is possible to easily obtain a content for an object-based audio service. When providing an object-based audio service using a separated sound source, it is difficult to perfectly separate a corresponding sound source due to a characteristic of the sound source separation technology. Consequently, each separated sound object may have a relatively low quality compared to an original sound object and thus, there is a need to set a range of controlling a sound object. 
     Accordingly, there is a desire for an effective bitstream structuring apparatus and method that may designate a control range of each separated sound object when producing an object-based audio content based on a low quality sound source obtained according to a sound source separation technology and the like. 
     SUMMARY 
     An aspect of the present invention provides a method and apparatus for structuring a bitstream that may reduce a degradation in the sound quality occurring due to an excessive volume control by designating an upper bound value and a lower bound value of a reproduction volume in an object-based audio service using a relatively low quality sound source, and an apparatus for encoding the bitstream. 
     Another aspect of the present invention also provides a method and apparatus for structuring a bitstream that may more effectively reproduce an object-based audio by including, in a bitstream, preset information of audio objects, and an apparatus for encoding the bitstream. 
     According to an aspect of the present invention, there is provided a method of structuring a bitstream, including: configuring the bitstream by separating the bitstream into a file header and frames of audio objects that are separated using a sound source separation scheme; and storing, in the file header, reproduction level information of audio objects. 
     The method may further include storing, in the file header, preset information of the audio objects. 
     The reproduction level information may include at least one of a number of the audio objects, maximum reproduction level information of each of the audio objects, and minimum reproduction level information of each of the audio objects. 
     The preset information may include at least one of a number of presets associated with audio objects, a location of each of the audio objects, and a sound volume. 
     According to another aspect of the present invention, there is provided an apparatus for structuring a bitstream, including: a bitstream separation unit to configure the bitstream by separating the bitstream into a file header and frames of audio objects; and a reproduction level information storage unit to store, in the file header, reproduction level information of audio objects. 
     According to still another aspect of the present invention, there is provided an apparatus for encoding a bitstream, including: a bitstream separation unit to configure the bitstream including a file header and frames of audio objects that are separated using a sound source separation scheme; and an encoding unit to encode the bitstream, wherein the bitstream separation unit stores, in the file header, reproduction level information of audio objects. 
     According to yet another aspect of the present invention, there is provided an apparatus for decoding a bitstream, including: a decoding unit to decode an encoded bitstream and to thereby extract a file header and frames of audio object that are separated using a sound source separation scheme; and a reproduction information extraction unit to extract, from the file header, reproduction level information of audio objects. 
     EFFECT 
     According to embodiments of the present invention, there may be provided a method and apparatus for structuring a bitstream that may reduce a degradation in the sound quality occurring due to an excessive volume control by designating an upper bound value and a lower bound value of a reproduction volume in an object-based audio service using a relatively low quality sound source, and an apparatus for encoding the bitstream. 
     Also, according to embodiments of the present invention, there may be provided a method and apparatus for structuring a bitstream that may more effectively reproduce an object-based audio by including, in a bitstream, preset information of audio objects, and an apparatus for encoding the bitstream. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects, features, and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a flowchart illustrating a method of structuring a bitstream for an object-based audio service according to an embodiment of the present invention; 
         FIG. 2  is a diagram illustrating a structure of a bitstream of an object-based audio according to an embodiment of the present invention; 
         FIG. 3  is a diagram illustrating a format of a file header in the bitstream of  FIG. 2 ; 
         FIG. 4  is a block diagram illustrating an apparatus for structuring a bitstream for an object-based audio service according to an embodiment of the present invention; 
         FIG. 5  is a block diagram illustrating an apparatus for encoding a bitstream for an object-based audio service according to an embodiment of the present invention; and 
         FIG. 6  is a block diagram illustrating an apparatus for decoding a bitstream for an object-based audio service according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Exemplary embodiments are described below to explain the present invention by referring to the figures. 
       FIG. 1  is a flowchart illustrating a method of structuring a bitstream for an object-based audio service according to an embodiment of the present invention. 
     Referring to  FIG. 1 , in operation  110 , a bitstream may be configured by separating the bitstream into a file header and frames of audio objects that are separated using a sound source separation scheme. Here, the file header may store information associated with each of audio objects, and each of the frames of audio objects may store frames of a substantially separated corresponding object. 
     In operation  120 , reproduction level information of the audio objects may be stored in the file header. Here, the reproduction level information may include information associated with a maximum reproduction level and a minimum reproduction level. The maximum reproduction level may denote an upper bound value of volume controlling a corresponding audio object, and the minimum reproduction level may denote a lower bound value of the volume controlling the corresponding audio object. 
     The reproduction level information may include information associated with a number of audio objects and thus, it is possible to easily transfer information associated with the number of separated audio objects. 
     The reproduction level information may independently exist for each separated audio object. For example, when the number of separated audio objects is five, for example, vocal, drum, piano, base, and violin, maximum reproduction level information and minimum reproduction level information with respect to each of the five audio objects may be included in the file header. 
     In operation  130 , preset information of the audio objects may be stored in the file header. The preset information may include at least one of a location of each of the audio objects and a sound volume. 
     Here, the preset information may include a number of presets associated with audio objects. For example, when five presets are to be transmitted, information indicating that the number of presets to be transmitted is five may be included in the preset information whereby the preset information may be transmitted. 
     As described above, since information associated with an upper bound value and a lower bound value is included in a bitstream and thereby is transmitted when reproducing a relatively low quality sound object obtained through a sound source separation technology and the like, it is possible to effectively provide an object-based audio service. 
     Hereinafter, a structure of the bitstream will be further described. 
       FIG. 2  is a diagram illustrating a structure of a bitstream  200  of an object-based audio according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the bitstream  200  of the object-based audio may include a file header  210  and a plurality of separated frames of audio objects  220  and  230 . Here, a down-mixed sound source may be transmitted as a separated frames of audio objects for each separated sound source. The file header  210  will be further described with reference to  FIG. 3 . 
       FIG. 3  is a diagram illustrating a format of the file header  210  in the bitstream  200  of  FIG. 2 . 
     Referring to  FIG. 3 , the file header  210  may store reproduction level information  310  and preset information  320 . 
     Due to characteristics of a sound source separation technology, it may be impossible to perfectly separate audio objects constituting a down-mixed audio signal. Therefore, when a user listens to the down-mixed audio signal by completely removing a particularly separated audio object, a quality of the sound source may be degraded by affecting the particularly separated audio object and other audio objects. When a minimum reproduction level is set with respect to each separated audio object, it may be possible to prevent the above degradation in the sound quality to some extents. When reproducing the separated audio object at least predetermined level value, the sound quality may be degraded due to distortion. Thus, there is a need to set a maximum reproduction level. In addition, due to the characteristics of the sound source separation technology, a maximum reproduction level and a minimum reproduction level may be different for each separated audio object and thus, there may be a need to set the maximum reproduction level and the minimum reproduction level for each separated audio object. Accordingly, the reproduction level information  310  may include information associated with the maximum reproduction level and the minimum reproduction level for each audio object. 
     The reproduction level information  310  may include information  311  associated with a number of separated audio objects. For example, when the down-mixed sound source is separated into five audio objects, “five” may be stored as the number of separated audio objects and thereby be transmitted. Accordingly, it is possible to easily transmit information regarding how many the separated audio objects are. 
     The preset information  320  may include a number of presets  321  using the audio objects, and preset information including preset  1  information  322  and preset  2  information  323 . Specifically, the number of presets  321  and individual preset information, for example, the preset  1  information  322  and the preset  2  information  323  may be provided. The preset information may include a location of each audio object, a sound volume, and the like. 
     A bitstream configured according to an embodiment of the present invention may utilize, for an object-based audio service, a relatively low quality audio object that is obtained using a sound source separation technology. The bitstream may also utilize the relatively low quality audio object for an object-based audio service in a case where only a quality degraded sound source is available due to constraints on a sound source obtainment environment, and the like. In addition, the bitstream may be applicable to a method and apparatus for reducing the effect of a quality degradation against a user by limiting an object controlling range of the user. 
       FIG. 4  is a block diagram illustrating an apparatus  400  for structuring a bitstream for an object-based audio service according to an embodiment of the present invention. 
     Referring to  FIG. 4 , the bitstream structuring apparatus  400  for the object-based audio service may include a bitstream separation unit  410  and a reproduction level information storage unit  420 . The bitstream structuring apparatus  400  may further include a preset storage unit  430 . 
     The bitstream separation unit  410  may configure a bitstream by separating the bitstream into a file header and frames of audio objects that are separated using a sound source separation scheme. 
     The reproduction level information storage unit  420  may store, in the file header, reproduction level information of audio objects. Here, the reproduction level information may include a number of the audio objects. The reproduction level information may include maximum reproduction level information of each of the audio objects and minimum reproduction level information of each of the audio objects. Specifically, it is possible to designate an upper bound value and a lower bound value of volume controllable by a user with respect to each audio object. 
     The preset storage unit  430  may store, in the file header, preset information of the audio objects. The preset information may include at least one of a number of presents, a location of each audio object, and a sound volume. 
       FIG. 5  is a block diagram illustrating an apparatus  500  for encoding a bitstream for an object-based audio service according to an embodiment of the present invention. 
     Referring to  FIG. 5 , the bitstream encoding apparatus  500  may include a bitstream separation unit  510  and an encoding unit  520 . 
     The bitstream separation unit  510  may configure a bitstream including a file header and frames of audio objects that are separated using a sound source separation scheme. Here, the bitstream separation unit  510  may store, in the file header, reproduction level information and preset information in association with the audio objects. 
     The encoding unit  520  may encode the bitstream. Specifically, the encoding unit  520  may encode the bitstream in order to transmit the bitstream. 
       FIG. 6  is a block diagram illustrating an apparatus  600  for decoding a bitstream for an object-based audio service according to an embodiment of the present invention. 
     Referring to  FIG. 6 , the bitstream decoding apparatus  600  may include a decoding unit  610  and a reproduction information extraction unit  620 . 
     The decoding unit  610  may decode an encoded bitstream to thereby extract a file header and frames of audio objects that are separated using a sound source separation scheme. 
     The reproduction information extraction unit  620  may extract, from the file header, reproduction level information of the audio objects. Here, the extracted reproduction level information may include maximum reproduction level information of each of audio objects and minimum reproduction level information of each of the audio objects. The file header may further include information associated with a number of audio objects that are separated from a sound source and thereby are transmitted, preset information of the audio objects, and the like. Accordingly, the reproduction information extraction unit  620  may further extract, from the file header, the transmitted information associated with the number of audio objects, the preset information, and the like. The preset information may include at least one of a number of presets associated with audio objects, a location of each audio object, and a sound volume. 
     Accordingly, the bitstream encoding apparatus  600  may reproduce a corresponding audio frame based on the extracted reproduction level information, preset information, and the like. 
     Descriptions not made above with reference to  FIG. 4  through  FIG. 6  may refer to descriptions made above with reference to  FIG. 1  through  FIG. 3 . 
     As described above, according to embodiments of the present invention, it is possible to decrease a degradation in the sound quality occurring due to an excessive volume control by designating an upper bound value and a lower bound value of reproduction volume of each separated sound source in a bitstream for transmitting an object-based audio using a relatively low quality sound source. 
     Also, according to embodiments of the present invention, it is possible to more effectively reproduce an object-based audio by including preset information of audio objects in a bitstream. 
     Although a few exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described exemplary embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.