Title of Invention	METHOD AND APPARATUS FOR PROCESSING AN AUDIO SIGNAL
Abstract	A method for processing an audio signal, comprising the steps of extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream, reading length information for the extension signal, skipping decoding of the extension signal or not using a result of the decoding based on the length information, and generating the audio signal using the ancillary signal. Accordingly, in case of processing the audio signal by the present invention, it is able to reduce a corresponding load of operation to enable efficient processing and enhance a sound quality.

Title of Invention

METHOD AND APPARATUS FOR PROCESSING AN AUDIO SIGNAL

Abstract

A method for processing an audio signal, comprising the steps of extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream, reading length information for the extension signal, skipping decoding of the extension signal or not using a result of the decoding based on the length information, and generating the audio signal using the ancillary signal. Accordingly, in case of processing the audio signal by the present invention, it is able to reduce a corresponding load of operation to enable efficient processing and enhance a sound quality.

Full Text	Method and Apparatus for Processing an Audio Signal TECHNICAL FIELD The present invention relates to a method and apparatus for processing an audio signal. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for processing a residual signal. BACKGROUND ART Generally, an audio signal includes a downmix signal and an ancillary data signal. And, the ancillary data signal can include a spatial information signal and an extension signal. In this case, the extension signal means an additional signal necessary to enable a signal to be reconstructed close to an original signal in generating a multi-channel signal by upmixing the downmix signal. For instance, the extension signal can include a residual signal. The residual signal means a signal corresponding to a difference between an original signal and a coded signal. In multi-channel audio coding, the residual signal is usable for the following cases. For instance, the residual signal is usable for compensation of an artistic downmix signal or specific channel compensation in decoding. And, the residual signal is usable for both of the compensations as well. So, it is able to reconstruct an inputted audio signal into a signal closer to an original signal using the residual signal to enhance sound quality. DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM However, if a decoder performs decoding on an extension signal unconditionally, although a sound quality may be improved according to a type of the decoder, complexity is raised and an operational load is increased. Moreover, since header information for an audio signal is not variable in general, the header information is inserted in a bit stream once only. But in case that the header information is inserted in the bit stream once only, if an audio signal needs to be decoded from a random timing point for broadcasting or VOD, it may be unable to decode data frame information due to the absence of the header information. TECHNICAL SOLUTION Accordingly, the present invention is directed to a method and apparatus for processing an audio signal that substantially obviate one or more of the problems due to limitations and disadvantages of the related art. An object of the present invention is to provide a method and apparatus for processing an audio signal, by which a processing efficiency of the audio signal is enhanced by skipping decoding of an extension signal. Another object of the present invention is to provide a method and apparatus for processing an audio signal, by which decoding of an extension signal is skipped using length information of the extension signal. Another object of the present invention is to provide a method and apparatus for processing an audio signal, by which an audio signal for broadcasting is reproducible from a random timing point. A further object of the present invention is to provide a method and apparatus for processing an audio signal, by which the audio signal is processed according to level information. ADVANTAGEOUS EFFECTS The present invention provides the following effects or advantages. First of all, in case of performing decoding, the present invention selectively decodes an extension signal to enable more efficient decoding. In case of performing decoding on an extension signal, the present invention is able to enhance a sound quality of an audio signal. In case of not performing decoding on an extension signal, the present invention is able to reduce complexity. Moreover, i even if decoding is performed on an extension signal, the present invention is able to enhance a sound quality by decoding a predetermined low frequency part only and also reduce a load of operation. Besides, in case of using an audio signal for broadcasting or the like, the present i invention is able to process an audio signal from a random timing point in a manner of identifying a presence or non- presence of header information within the audio signal. BRIEF DESCRIPTION OF THE DRAWINGS i The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: FIG. 1 is a block diagram of an audio signal encoding apparatus and an audio signal decoding apparatus according to an embodiment of the present invention; FIG. 2 is a schematic block diagram of an extension signal decoding unit 90 according to an embodiment of the present invention; FIG. 3 and FIG. 4 are diagrams to explain fixed bits assignment of length information for an extension signal according to an embodiment of the present invention; FIG. 5 and FIG. 6 are diagrams to explain variable bits assignment of length information for an extension signal by depending on a length type according to an embodiment of the present invention; FIG. 7 and FIG. 8 are diagrams to explain adaptive bits assignment of length information for an extension signal by depending on a real length of the extension signal according to an embodiment of the present invention; FIG. 9 is a diagram of a bit stream structure configuring an audio signal with a downmix signal, an ancillary signal, and an extension signal according to an embodiment of the present invention; FIG. 10 is a diagram of a bit stream structure configuring an audio signal with an ancillary signal including an extension signal and a downmix signal according to an embodiment of the present invention; FIG. 11 is a diagram of a bit stream structure configuring an independent audio signal with a downmix signal or an ancillary signal according to an embodiment of the present invention; FIG. 12 is a diagram of a broadcasting streaming structure configuring an audio signal with a downmix signal and an ancillary signal according to an embodiment of the present invention; FIG. 13 is a flowchart of a method of processing an extension signal using length information of the extension signal in accordance with identification information indicating whether a header is included within an ancillary signal in case if using an audio signal for broadcasting or the like according to an embodiment of the present invention; and FIG. 14 is a flowchart of a method of decoding an extension signal selectively using length information of the extension signal in accordance with a level of a bit stream according to an embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings. To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method for processing an audio signal according to the present invention includes the steps of extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream, reading length information of the extension signal, skipping decoding of the extension signal or not using a result of the decoding based on the length information, and generating the audio signal using the ancillary signal. To further achieve these and other advantages and in accordance with the purpose of the present invention, a method for processing an audio signal includes the steps of acquiring sync information indicating a location of an ancillary signal for generating the audio signal and a location of an extension signal included in the ancillary signal, skipping decoding of the extension signal or not using a result of the decoding based on the sync information, and generating the audio signal using the ancillary signal. To further achieve these and other advantages and in accordance with the purpose of the present invention, an apparatus for processing an audio signal includes a signal extracting unit extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream, an extension signal length reading unit reading length information of the extension signal, a selective decoding unit skipping decoding of the extension signal or not using a result of the decoding based on the length information, and an upmixing unit generating the audio signal using the ancillary signal. To further achieve these and other advantages and in accordance with the purpose of the present invention, an apparatus for processing an audio signal includes a sync information acquiring unit acquiring sync information indicating a location of an ancillary signal for generating the audio signal and a location of an extension signal included in the ancillary signal, a selective decoding unit skipping decoding of the extension signal or not using a result of the decoding based on the sync information, and an upmixing unit generating the audio signal using the ancillary signal. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. MODE FOR 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. FIG. 1 is a block diagram of an audio signal encoding apparatus and an audio signal decoding apparatus according to an embodiment of the present invention. Referring to FIG. 1, an encoding apparatus includes a downmixing unit 10, a downmix signal encoding unit 20, an ancillary signal encoding unit 30, an extension signal encoding unit 40, and a multiplexing unit 50. In case that multi-source audio signals XI, X2, ..., Xn are inputted to the downmixing unit 10, the downmixing unit 10 generates a downmix signal by downmixing the multi- source audio signals. The downmix signal includes a mono signal, a stereo signal, or a multi-source audio signal. The source includes a channel and is described as the channel for convenience. In the specification of the present invention, explanation is made with reference to a mono or stereo downmix signal. Yet, the present invention is not limited to the mono or stereo downmix signal. The encoding apparatus is able to use an artistic downmix signal provided from an outside selectively and directly. In the course of downmixing, an ancillary signal can be generated from a multi-channel audio signal and an extension signal corresponding to additional information can be generated as well. In this case, the ancillary signal can include a spatial information signal and an extension signal. The generated downmix, ancillary and extension signals are encoded by the downmix signal encoding unit 20, the ancillary signal encoding unit 30, and the extension signal encoding unit 4 0 and are then transferred to the multiplexing unit 50, respectively. In the present invention, the ^spatial information' means the information necessary for the encoding apparatus to transfer a downmix signal generated from downmixing multi-channel signals to the decoding apparatus and necessary for the decoding apparatus to generate multi- channel signals by upmixing the downmix signal. The spatial information includes spatial parameters. The spatial parameters include CLD (channel level difference) indicating an energy difference between channels, ICC (inter-channel coherences) meaning a correlation between channels, CPC (channel prediction coefficients) used in generating three channels from two channels, etc. And, the ^extension signal' means additional information necessary to enable a signal to be reconstructed closer to an original signal in generating multi-channel signals by upmixing the downmix signal by the decoding apparatus. For instance, the additional information includes a residual signal, an artistic downmix residual signal, an artistic tree extension signal, etc. In this case, the residual signal indicates a signal corresponding to a difference between an original signal and an encoded signal. In the following description, it is assumed that the residual signal includes a general residual signal or an artistic downmix residual signal for compensation of an artistic downmix signal. In the present invention, the downmix signal encoding unit 2 0 or the downmix signal decoding unit 70 means a codec that encodes or decodes an audio signal not included with an ancillary signal. In the present specification, a downmix audio signal is taken as an example of not included with the ancillary signal the audio signal. And, the downmix signal encoding unit 20 or the downmix signal decoding unit 70 is able to include MP3, AC-3, DTS, or AAC. If a codec function is performed on an audio signal, the downmix signal encoding unit 20 and the downmix signal decoding unit 70 can include a codec to be developed in the future as well as a previously developed codec. The multiplexing unit 50 can generate a bit stream by multiplexing a downmix signal, an ancillary signal, and an extension signal and then transfer the generated bit stream to the decoding apparatus. In this case, both of the downmix signal and the ancillary signal can be transferred in a bit stream format to the decoding apparatus. Alternatively, the ancillary signal and the downmix signal can be transferred in independent bit stream formats to the decoding apparatus, respectively. Details of the bit streams are explained in FIGs. 9 to 11. In case that it is unable to use previously transferred header information since an audio signal starts to be decoded from a random timing point instead of being decoded from the beginning like a bit stream for broadcasting, it is able to decode the audio signal using another header information inserted in the audio signal. In case of header information is lost in the course of transferring an audio signal, decoding should start from any timing point of receiving a signal. So, header information can be inserted in an audio signal at least once. If header information exists in a front part of an audio signal only once, it is unable to perform decoding due to the absence of the header information in case of receiving an audio signal at a random timing point. In this case, header information can be included according to a preset format (e.g., temporal interval, spatial interval, etc.). It is able to insert identification information indicating a presence or non-presence of header information in a bit stream. And, an audio signal is able to selectively include a header according to the identification information. For instance, an ancillary signal is able to selectively include a header according to the header identification information. Details of the bit stream structures are explained in FIGs. 9 to 12. The decoding apparatus includes a demultiplexing unit 60, a downmix signal decoding unit 70, an ancillary signal decoding unit 80, an extension signal decoding unit 90, and an upmixing unit 100. The demultiplexing unit 60 receives a bit stream and then separates an encoded downmix signal, an encoded ancillary signal, and an encoded extension signal from the received bit stream. The downmix signal decoding unit 7 0 decodes the encoded downmix signal. And, the ancillary signal decoding unit 8 0 decodes the encoded ancillary signal. Meanwhile, the extension signal can be included in the ancillary signal. It is necessary to efficiently decode the extension signal to efficiently generate multi-channel audio signals. So, the extension signal decoding unit 90 is able to selectively decode the encoded extension signal. In particular, the encoded extension signal can be decoded or the decoding of the encoded extension signal can be skipped. Occasionally, if the decoding of the extension signal is skipped, the encoded signal can be reconstructed to be closer to an original signal and coding efficiency can be raised. For instance, if a level of the decoding apparatus is lower than that of a bit stream, the decoding apparatus is unable to decode the received extension signal. So, the decoding of the extension signal can be skipped. Even if the decoding of the extension signal is available because the level of the decoding apparatus is higher than that of the bit stream, the decoding of the extension signal is able to be skipped by another information obtained from the audio signal. In this case, for instance, the another information may include information indicating whether to execute the decoding of the extension signal. This is explained in detail with reference to FIG. 14 later. And for instance, in order to omit the decoding of the extension signal, length information of the extension signal is read from the bit stream and the decoding of the extension signal is able to be skipped using the length information. Alternatively, it is able to skip the decoding of the extension signal using sync information indicating a position of the extension signal. This is explained in detail with reference to FIG. 2 later. The length information of the extension signal can be defined in various ways. For instance, fixed bits can be assigned, or variable bits can be assigned according to a predetermined length information type, or bits suitable for a length of a real extension signal can be adaptively assigned while the length of the extension signal is read. Details of the fixed bits assignment are explained in FIG. 3 and FIG. 4. Details of the variable bits assignment are explained in FIG. 5 and FIG. 6. And, details of the adaptive bits assignment are explained in FIG. 7 and FIG. 8. The length information of the extension signal can be located within an ancillary data area. In this case, the ancillary data area indicates an area where additional information necessary to reconstruct a downmix signal into an original signal exists. For instance, a spatial information signal or an extension signal can be taken as an example of the ancillary data. So, the length information of the extension signal can be located within the ancillary signal or an extension area of the ancillary signal. In particular, the length information of the extension signal is located within a header extension area of the ancillary signal, a frame data extension area of the ancillary signal, or both of the header extension area and the frame data extension area of the ancillary signal. These are explained in detail with reference to FIGs. 9 to 11 later. FIG. 2 is a schematic block diagram of an extension signal decoding unit 90 according to an embodiment of the present invention. Referring to FIG. 2, the extension signal decoding unit 90 includes an extension signal type information acquiring unit 91, an extension signal length reading unit 92, and a selective decoding unit 93. And, the selective decoding unit 93 includes a level deciding unit 94, an extension signal information acquiring unit 95, and an extension signal information skipping unit 96. The extension signal decoding unit 90 receives a bit stream for an extension signal from the demultiplexing unit 60 and then outputs a decoded extension signal. Occasionally, the extension signal decoding unit 90 may not output an extension signal or can output an extension signal by padding a bit stream for the extension signal with zeros completely. For the case of not outputting an extension signal, a method of skipping the decoding of the extension signal is usable. The extension signal type acquiring unit 91 acquires information indicating a type of an extension signal from a bit stream. For instance, the information indicating the type of the extension signal can include a residual signal, an artistic downmix residual signal, an artistic tree extension signal, or the like. In the present invention, the residual signal is a generic term of a general residual signal or an artistic downmix residual signal for compensation of an artistic downmix signal. The residual signal is usable for compensation of an artistic downmix signal in multi-channel audio signals or specific channel compensation in decoding. Optionally, the two cases are usable as well. If the type of the extension signal is decided by the extension signal type information, the extension signal length reading unit 92 reads a length of the extension signal decided by the type information of the extension signal. This can be achieved regardless of whether to perform the decoding of the extension signal. Once the length of the extension signal is read, the selective decoding unit 93 selectively performs decoding on the extension signal. This can be decided by the level deciding unit 94. In particular, the level deciding unit 94 selects whether to execute the decoding of the extension signal by comparing a level of a bit stream to a level of a decoding apparatus. For instance, if the level of the decoding apparatus is equal to or higher than that of the bit stream, the decoding apparatus acquires information for the extension signal via the extension signal information acquiring unit 95 and then decodes the information to output the extension signal. The outputted extension signal is transferred to an upmixing unit 100 to be used in reconstruct an original signal or generating an audio signal. Yet, if the level of the decoding apparatus is lower than that of the bit stream, it is able to skip the decoding of the extension signal via the extension signal information skipping unit 96. In this case, it is able to skip the decoding of the extension signal based on the length information read by the extension signal length reading unit 92. Thus, in case that the extension signal is used, the reconstruction can be achieved to get closer to the original signal to enhance a sound quality. If necessary, it is able to reduce a load of operation of the decoding apparatus by omitting the decoding of the extension signal. As an example of the method of omitting the decoding of the extension signal in the extension signal information skipping unit 96, in case of using the length information of the extension signal, bit or byte length information of the extension signal can be inserted in data. And, the decoding can keep proceeding by skipping a bit field of the extension signal as many as a value obtained from the length information. Methods of defining the length information of the extension signal shall be explained with reference to FIGs. 3 to 8. As another example of the method of omitting the decoding of the extension signal, it is able to skip the decoding of the extension signal based on sync information indicating a position of the extension signal. For instance, it is able to insert a sync word having predetermined bits in the point where the extension signal ends. The decoding apparatus keeps searching the bit field of the residual signal until finding a sync word of the extension signal. Once finding the sync word, the decoding apparatus stops the search process and then keeps performing the decoding. In particular, it is able to skip the decoding of the extension signal until the sync word of the extension signal is found. As another example of a decoding method according to the selection, in case of performing the decoding of the extension signal, it is able to perform the decoding after parsing the extension signal. When the decoding of the extension signal is performed, the sync word of the extension signal is read but may not be available. FIG. 3 and FIG. 4 are diagrams to explain fixed bits assignment of length information for an extension signal according to an embodiment of the present invention. The length information of the extension signal can be defined by a bit or byte unit. If the length information is decided by the byte unit, this means that the extension signal is assigned bytes. FIG. 3 shows a method of defining length information for an extension signal in a simplest way. And, FIG. 4 shows the method shown in FIG. 3 schematically. A syntax element for indicating the length information of the extension signal is defined and predetermined bits are assigned to the syntax element. For instance, 'bsResidualSignalLength' is defined as the syntax element and 16 bits are assigned as fixed bits. Yet, this method may consume a relatively considerable amount of bits. So, the methods shown in FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are explained as follows. FIG. 5 and FIG. 6 are diagrams to explain variable bits assignment of length information for an extension signal by depending on a length type according to an embodiment of the present invention. FIG. 5 shows a method of defining one more syntax element for defining how many bits are used for 'bsResidualSignalLength' to further reduce bit consumption. And, FIG. 6 schematically illustrates the method shown in FIG. 5. For instance, . ^bsResidualSignalLengthtype' is newly defined as a length type. If a value of the 'bsResidualSignalLengthtype' is zero, four bits are assigned to the ^bsResidualSignalLength'. If a value of the xbsResidualSignalLengthtype' is 1, eight bits are assigned to the ^bsResidualSignalLength' . If a value of the ^bsResidualSignalLengthtype' is 2, twelve bits are assigned to the 'bsResidualSignalLength' . If a value of the vbsResidualSignalLengthtype' is 3, sixteen bits are assigned to the 'bsResidualSignalLength'. In this case, the . assigned bits are exemplary. So, bits different from the above-defined bits can be assigned. To reduce the bit consumption more than those of the above methods, the method shown in FIG. 7 and FIG. 8 is provided. FIG. 7 and FIG. 8 are diagrams to explain adaptive bits assignment of length information for an extension signal by depending on a real length of the extension signal according to an embodiment of the present invention. If an extension signal is inputted, a length information value of the extension signal can be read up to an initially determined value. If the length information value equals to a predetermined value, it is able to read additionally up to a further determined value. If the length information value equals to another predetermined value, it is able to read additionally up to another further determined value. In this case, if the length information value is not another predetermined value, the corresponding value is outputted as the length information value as it is. Thus, the length information of the extension signal is adaptively read according to a real data length, whereby the bit consumption can be maximally reduced. The example shown in FIG. 7 or FIG. 8 is explained. In FIG. 7, a residual signal is taken as an example of the extension signal. If a residual signal is inputted, four bits of the residual signal length are read. If a length information value (bsResidualSignalLength) is 24-l (=15) , eight bits are further read as a value of bsResidualSignalLengthl. If the length information value (bsResidualSignalLength) is (24-l) + (28-l) (=15+255), twelve bits are further read as a value of bsResidualSignalLength2. In the same manner, if the length information value (bsResidualSignalLength) is (24-l) + (28-l) + (212-1) (=15+255+4095), sixteen bits are further read as a value of bsResidualSignalLength3. FIG. 8 schematically illustrates another example of the adaptive bits assignment of length information for an extension signal. In FIG. 8, if an extension signal is inputted, four bits are preferentially read. If a value resulting from reading length information is smaller than four bits, the corresponding value becomes the length information. Yet, if a value resulting from reading length information is greater than four bits, eight bits are further read in addition. If the additionally read value is smaller than eight bits, a total read length information value corresponds to 12 (=4 + 8) . Yet, if the additionally read value is greater than eight bits, sixteen bits are further read in addition again. This is explained in detail as follows. First of all, if length information is inputted, four bits are read. A real length information value ranges 0~14. If the length information value becomes 24-l (=15), the extension signal is further read in addition. In this case, the extension signal can be additionally read up to 28-2 (=254) . Yet, if the length information value corresponds to a value smaller than 24-l (=15), a value of the read 0~(24-2) (=14) is outputted as it is. Once the length information value becomes (24-l) + (28-l) , the extension signal is further read in addition. In this case, the extension signal can be additionally read up to (216-1). Yet, if the length information value corresponds to a value smaller than 216-1, a value of the read 0~(216-l) (=14) is outputted as it is. In this case, as mentioned in the foregoing description, the assigned bits are exemplary for explanation. So, another bits different from the above- defined bits can be assigned. Meanwhile, the length information of the extension signal can be length information of the extension signal header or length information of the extension signal frame data. So, the length information of the extension signal can be located in a header area and/or a frame data area. Bit stream structures for this are explained with reference to FIGs. 9 to 12. FIG. 9 and FIG. 10 show embodiments of the present invention, in which a bit stream structure configuring an audio signal with a downmix signal, an ancillary signal, and an extension signal is shown. An audio signal includes a downmix signal and an ancillary signal. As an example of the ancillary signal, a spatial information signal can be taken. Each of the downmix signal and the ancillary signal is transferred by a frame unit. The ancillary signal can include header information and data information or can include data information only. Thus, in the file/general streaming structure configuring one audio signal, the header information precedes and is followed by the data information. For instance, in case of a file/general streaming structure configuring one audio signal with a downmix signal and an ancillary signal, a downmix signal header and an ancillary signal header can exist as the header information in a front part. And, downmix signal data and ancillary signal data can configure one frame as the data information behind the front part. In this case, by defining an extension area of the ancillary data, it is able to locate an extension signal. The extension signal can be included within the ancillary signal or can be used as an independent signal. FIG. 9 shows a case that the extension signal is used as the independent signal and FIG. 10 shows a case that the extension signal is located in the extension area within the ancillary signal. So, in case that there exists the extension signal, in the file/general streaming structure, an extension signal header can exist as header information in the front part as well as the downmix header and the spatial information header. Behind the front part, extension signal data can be further included as data information as well as the downmix signal data and the ancillary signal data to configure one frame. Since the extension signal can be selectively decoded, it can be located at a last part of the frame or can consecutively exist right behind the ancillary signal. The length information explained in FIGs. 3 to 8 can exist within the header area of the extension signal and/or the data area of the extension signal. In this case, the length information existing within the header area (extension signal header) indicates the length information of the extension signal header, and the length information existing within the data area (extension signal data) indicates the length information of the extension signal data. Thus, the length information existing each of the areas is read from a bit stream and the decoding apparatus is able to skip the decoding of the extension signal based on the length information. FIG. 11 is a diagram of a bit stream structure configuring an independent audio signal with a downmix signal or an ancillary signal according to an embodiment of the present invention. An audio signal includes a downmix signal and an ancillary signal. As an example of the ancillary signal, a spatial information signal can be taken. The downmix signal and the ancillary signal can be transferred as independent signals, respectively. In this case, the downmix signal has a structure that a downmix signal header (downmix signal header®) as header information is located at a front part and that downmix signal datas (downmix signal data ©, ©, © , ..., © ) as data information follow the downmix signal header. Likewise, the ancillary signal has a structure that an ancillary signal header (ancillary signal header ©) as header information is located at a front part and that ancillary signal datas (ancillary signal data ®, ©, ..., ®) as data information follow the ancillary signal header. Since the extension signal can be included within the ancillary signal, a structure that the extension signal follows the ancillary signal data can be provided. So, an extension signal header © follows the ancillary signal header ® and the extension signal data © follows the ancillary signal data © . Likewise, the extension signal data © follows the ancillary signal data ©. In this case, length information of the extension signal can be included in each of the extension signal header ® , the extension signal data ©, and/or the extension signal data ©, ..., and Meanwhile, unlike the file/general streaming structure, in case that it is unable to use previously transferred header information since an audio signal is decoded from a random timing point instead of being decoded from the beginning, it is able to decode the audio signal using another header information included in the audio signal. In case of using an audio signal for broadcasting or the like or losing header information in the course of transferring an audio signal, decoding should start from any moment of receiving a signal. So, it is able to improve coding efficiency by defining identification information indicating whether the header exits. A streaming structure for broadcasting is explained with reference to FIG. 12 as follows. FIG. 12 is a diagram of a broadcasting streaming structure configuring an audio signal with a downmix signal and an ancillary signal according to an embodiment of the present invention. In case of a broadcast streaming, if header information exists in a front part of an audio signal once only, it is unable to execute decoding due to the absence of header information in case of receiving an audio signal at a random timing point. So, the header information can be inserted in the audio signal once at least. In this case, the header information can be included according to a preset format (e.g., temporal interval, spatial interval, etc.). In particular, the header information can be inserted in each frame, periodically inserted in each frame with a fixed interval, or non-periodically inserted in each frame with a random interval. Alternatively, the header information can be inserted once according to a fixed time interval (e.g., 2 seconds). A broadcast streaming structure configuring one audio signal has a structure that at least once header information is inserted between data informations. For instance, in case of a broadcast streaming structure configuring one audio signal, a downmix signal comes first and an ancillary signal follows the downmix signal. Sync information for distinguishing between the downmix signal and the ancillary signal can be located at a front part of the ancillary signal. And, identification information indicating whether header information for the ancillary signal exists can be located. For instance, if header identification information is 0, a next read frame only has a data frame without header information. If the header identification information is 1, a next read frame has both header information and a data frame. This is applicable to the ancillary signal or the extension signal. These header informations may be the same of the header information having been initially transferred or can be variable. In case that the header information is variable, new header information is decoded and data information transferred after the new header information is then decoded according to the decoded new header information. In case that the header identification information is 0, a transferred frame only has a data frame without header information. In this case, to process the data frame, previously transferred header information can be used. For instance, if the header identification information is 1 in FIG., 12, an ancillary signal header © and an extension signal header © can exist. Yet, if a next incoming frame has no header information since the header identification information set to 0, it is able to use information of the extension signal header © previously transferred to process extension signal data ©. FIG. 13 is a flowchart of a method of processing an extension signal based on length information of the extension signal in accordance with identification information indicating whether a header is included within an ancillary signal in case of using an audio signal for broadcasting or the like according to an embodiment of the present invention. Referring to FIG. 13, an ancillary signal for an audio signal generation and an extension signal included in the ancillary signal are extracted from a received bit stream (1301). The extension signal can be included within the ancillary signal. Identification information indicating whether a header is . included in the ancillary signal is extracted (1303). For instance, if the header identification information is 1, it indicates that an ancillary signal header is included in the ancillary signal. If the header identification information is 0, it indicates that an ancillary signal header is not included in the ancillary signal. In case that the extension signal is included in the ancillary signal, if the header identification information is 1, it indicates that an extension signal header is included in the extension signal. If the header identification information is 0, it indicates that an extension signal header is not included in the extension signal. It is decided that whether a header is included in the ancillary signal according to the header identification information (1305). If the header is included in the ancillary signal, length information is extracted from the header (1307). And, it is able to skip decoding of the extension signal based on the length information (1309). In this case, the header plays a role in enabling each ancillary signal and/or each extension signal to be interpreted. For instance, the header information can include information for a residual signal, length information for a residual signal, sync information indicating a location of a residual signal, a sampling frequency, a frame length, the number of a parameter band, tree information, quantization mode information, ICC (inter-channel correlation), parameter smoothing information, gain information for a clipping-prevention, QMF (quadrature mirror filter) associated information, etc. Moreover, if the header is not included in the ancillary signal according to the header identification information, it is able to skip decoding of the extension signal based on the previously extracted length information for the header (1311). FIG. 14 is a flowchart of a method of decoding an extension signal selectively based on length information of the extension signal according to an embodiment of the present invention. A profile means that technical elements for algorithm in a coding process are standardized. In particular, the profile is a set of technical elements necessary to decode a bit stream and corresponds to a sort of a sub-standard. A level defines a range of the technical elements, which are prescribed in the profile, to be supported. In particular, the level plays a role in defining capability of a decoding apparatus and complexity of a bit stream. In the present invention, level information can include definitions for the profile and level. A decoding method of an extension signal can selectively vary according to the level information of the bit stream and the level information of the decoding apparatus. For instance, even if the extension signal exists in a transferred audio signal, decoding of the extension signal may be or may not be executed as a result of deciding the level information. Moreover, although the decoding is executed, a predetermined low frequency part can be used only. Besides, it is able to skip the decoding of the extension signal as many as length information of the extension signal in order not to execute the decoding of the extension signal. Alternatively, although the extension signal is entirely read, the decoding cannot be executed. Furthermore, a portion of the extension signal is read, decoding can be performed on the read portion only, and the decoding cannot be performed on the rest of the extension signal. Alternatively, the extension signal is entirely read, a portion of the extension signal can be decoded, and the rest of the extension signal cannot be decoded. For instance, referring to FIG. 14, an ancillary signal for generating an audio signal and an extension signal included in the ancillary signal can be extracted from a received bit stream (1410) . And, information for the extension signal can be extracted. In this case, the information for the extension signal may include extension data type information indicating a data type of the extension signal. For instance, the extension data type information includes residual coding data, artistic downmix residual coding data, artistic tree extension data, or the like. So, the type of the extension signal is decided and it is able to read length information of the extension signal from an extension area of the audio signal (1420) . Subsequently, a level of the bit stream is decided. This can be decided with reference to following information. For instance, if the type of the extension signal is the residual coding data, the level information for the bit stream can include the number of output channels, a sampling rate, a bandwidth of a residual signal, and the like. So, if the above-explained level informations of the bit stream are inputted, they are compared to level information for a decoding apparatus to decide whether the extension signal will be decoded (1430). In this case, a level of the decoding apparatus can be previously set. In general, the level of the decoding apparatus should be equal to or greater than a level of the audio signal. This is because the decoding apparatus should be able to decode the transferred audio signal entirely. Yet, in case that limitation is put on the decoding apparatus (e.g., in case that the level of the decoding apparatus is smaller than that of the audio signal), decoding is occasionally possible. Yet, a corresponding quality may be degraded. For instance, if the level of the decoding apparatus is lower than that of the audio signal, the decoding apparatus may be unable to decode the audio signal. Yet, in some cases, the audio signal can be decoded based on the level of the decoding apparatus. In case that the level of the decoding apparatus is decided lower than that of the bit stream, it is able to skip the decoding of the extension signal based on the length information of the extension signal (1440). On the other hand, in case that the level of the decoding apparatus is equal to or higher than that of the bit stream, it is able to execute the decoding of the extension signal (1460). Yet, although the decoding of the extension signal is executed, the decoding can be performed on a predetermined low frequency portion of the extension signal only (1450) . For instance, there is a case that since the decoding apparatus is a low power decoder, if the extension signal is entirely decoded, efficiency is degraded, or since the decoding apparatus is unable to decode the entire extension signal a predetermined low frequency portion of the extension signal is usable. And, this is possible if the level of the bit stream or the level of the decoding apparatus meets a prescribed condition only. INDUSTRIAL APPLICABILITY Accordingly, various environments for encoding and decoding signals exist in general and there can exist various methods of processing signals according to the various environment conditions. In the present invention, a method of processing an audio signal is taken as an example, which does not restrict the scope of the present invention. In this case, the signals include audio signals and/or video signals. While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be, apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents. What is Claimed is: 1. A method for processing an audio signal, comprising the steps of: extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream; reading length information for the extension signal; skipping decoding of the extension signal or not using a result of the decoding based on the length information; and generating the audio signal using the ancillary signal. 2. The method of claim 1, wherein the extension signal is a residual signal. 3. The method of claim 1 or claim 2, wherein the length information of the extension signal is assigned fixed bits. 4. The method of claim 1 or claim 2, wherein the length information of the extension signal is assigned variable bits according to length type information of the extension signal. 5. The method of claim 1 or claim 2, wherein the length information of the extension signal is assigned adaptive bits according to a length of the extension signal. 6. A method of processing an audio signal, comprising the steps of: acguiring sync information indicating a location of an ancillary signal for generating the audio signal and a location of an extension signal included in the ancillary signal; skipping decoding of the extension signal or not using a result of the decoding based on the sync information; and generating the audio signal using the ancillary signal. 7. The method of claim 6, wherein the sync information indicates a start point and/or an end point of the extension signal. 8. The method of claim 6, wherein the extension signal is a residual signal. 9. An apparatus for processing an audio signal, comprising: a signal extracting unit extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream; an extension signal length reading unit reading length information of the extension signal; a selective decoding unit skipping decoding of the extension signal or not using a result of the decoding based on the length information; and an upmixing unit generating the audio signal using the ancillary signal. 10. An apparatus for processing an audio signal, comprising: a sync information acquiring unit acquiring sync information indicating a location of an ancillary signal for generating the audio signal and a location of an extension signal included in the ancillary signal; a selective decoding unit skipping decoding of the extension signal or not using a result of the decoding based on the sync information; and an upmixing unit generating the audio signal using the ancillary signal. A method for processing an audio signal, comprising the steps of extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream, reading length information for the extension signal, skipping decoding of the extension signal or not using a result of the decoding based on the length information, and generating the audio signal using the ancillary signal. Accordingly, in case of processing the audio signal by the present invention, it is able to reduce a corresponding load of operation to enable efficient processing and enhance a sound quality.

Full Text

Method and Apparatus for Processing an Audio Signal
TECHNICAL FIELD
The present invention relates to a method and
apparatus for processing an audio signal. Although the
present invention is suitable for a wide scope of
applications, it is particularly suitable for processing a
residual signal.
BACKGROUND ART
Generally, an audio signal includes a downmix signal
and an ancillary data signal. And, the ancillary data
signal can include a spatial information signal and an
extension signal. In this case, the extension signal means
an additional signal necessary to enable a signal to be
reconstructed close to an original signal in generating a
multi-channel signal by upmixing the downmix signal. For
instance, the extension signal can include a residual
signal. The residual signal means a signal corresponding to
a difference between an original signal and a coded signal.
In multi-channel audio coding, the residual signal is
usable for the following cases. For instance, the residual
signal is usable for compensation of an artistic downmix
signal or specific channel compensation in decoding. And,

the residual signal is usable for both of the compensations
as well. So, it is able to reconstruct an inputted audio
signal into a signal closer to an original signal using the
residual signal to enhance sound quality.
DISCLOSURE OF THE INVENTION
TECHNICAL PROBLEM
However, if a decoder performs decoding on an
extension signal unconditionally, although a sound quality
may be improved according to a type of the decoder,
complexity is raised and an operational load is increased.
Moreover, since header information for an audio
signal is not variable in general, the header information
is inserted in a bit stream once only. But in case that the
header information is inserted in the bit stream once only,
if an audio signal needs to be decoded from a random timing
point for broadcasting or VOD, it may be unable to decode
data frame information due to the absence of the header
information.
TECHNICAL SOLUTION
Accordingly, the present invention is directed to a
method and apparatus for processing an audio signal that
substantially obviate one or more of the problems due to

limitations and disadvantages of the related art.
An object of the present invention is to provide a
method and apparatus for processing an audio signal, by
which a processing efficiency of the audio signal is
enhanced by skipping decoding of an extension signal.
Another object of the present invention is to provide
a method and apparatus for processing an audio signal, by
which decoding of an extension signal is skipped using
length information of the extension signal.
Another object of the present invention is to provide
a method and apparatus for processing an audio signal, by
which an audio signal for broadcasting is reproducible from
a random timing point.
A further object of the present invention is to
provide a method and apparatus for processing an audio
signal, by which the audio signal is processed according to
level information.
ADVANTAGEOUS EFFECTS
The present invention provides the following effects
or advantages.
First of all, in case of performing decoding, the
present invention selectively decodes an extension signal
to enable more efficient decoding. In case of performing

decoding on an extension signal, the present invention is
able to enhance a sound quality of an audio signal. In case
of not performing decoding on an extension signal, the
present invention is able to reduce complexity. Moreover,
i even if decoding is performed on an extension signal, the
present invention is able to enhance a sound quality by
decoding a predetermined low frequency part only and also
reduce a load of operation. Besides, in case of using an
audio signal for broadcasting or the like, the present
i invention is able to process an audio signal from a random
timing point in a manner of identifying a presence or non-
presence of header information within the audio signal.
BRIEF DESCRIPTION OF THE DRAWINGS
i The accompanying drawings, which are included to
provide a further understanding of the invention and are
incorporated in and constitute a part of this specification,
illustrate embodiments of the invention and together with
the description serve to explain the principles of the
invention.
In the drawings:
FIG. 1 is a block diagram of an audio signal encoding
apparatus and an audio signal decoding apparatus according
to an embodiment of the present invention;

FIG. 2 is a schematic block diagram of an extension
signal decoding unit 90 according to an embodiment of the
present invention;
FIG. 3 and FIG. 4 are diagrams to explain fixed bits
assignment of length information for an extension signal
according to an embodiment of the present invention;
FIG. 5 and FIG. 6 are diagrams to explain variable
bits assignment of length information for an extension
signal by depending on a length type according to an
embodiment of the present invention;
FIG. 7 and FIG. 8 are diagrams to explain adaptive
bits assignment of length information for an extension
signal by depending on a real length of the extension
signal according to an embodiment of the present invention;
FIG. 9 is a diagram of a bit stream structure
configuring an audio signal with a downmix signal, an
ancillary signal, and an extension signal according to an
embodiment of the present invention;
FIG. 10 is a diagram of a bit stream structure
configuring an audio signal with an ancillary signal
including an extension signal and a downmix signal
according to an embodiment of the present invention;
FIG. 11 is a diagram of a bit stream structure
configuring an independent audio signal with a downmix

signal or an ancillary signal according to an embodiment of
the present invention;
FIG. 12 is a diagram of a broadcasting streaming
structure configuring an audio signal with a downmix signal
and an ancillary signal according to an embodiment of the
present invention;
FIG. 13 is a flowchart of a method of processing an
extension signal using length information of the extension
signal in accordance with identification information
indicating whether a header is included within an ancillary
signal in case if using an audio signal for broadcasting or
the like according to an embodiment of the present
invention; and
FIG. 14 is a flowchart of a method of decoding an
extension signal selectively using length information of
the extension signal in accordance with a level of a bit
stream according to an embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Additional features and advantages of the invention
will be set forth in the description which follows, and in
part will be apparent from the description, or may be

learned by practice of the invention. The objectives and
other advantages of the invention will be realized and
attained by the structure particularly pointed out in the
written description and claims thereof as well as the
appended drawings.
To achieve these and other advantages and in
accordance with the purpose of the present invention, as
embodied and broadly described, a method for processing an
audio signal according to the present invention includes
the steps of extracting an ancillary signal for generating
the audio signal and an extension signal included in the
ancillary signal from a received bit stream, reading length
information of the extension signal, skipping decoding of
the extension signal or not using a result of the decoding
based on the length information, and generating the audio
signal using the ancillary signal.
To further achieve these and other advantages and in
accordance with the purpose of the present invention, a
method for processing an audio signal includes the steps of
acquiring sync information indicating a location of an
ancillary signal for generating the audio signal and a
location of an extension signal included in the ancillary
signal, skipping decoding of the extension signal or not
using a result of the decoding based on the sync

information, and generating the audio signal using the
ancillary signal.
To further achieve these and other advantages and in
accordance with the purpose of the present invention, an
apparatus for processing an audio signal includes a signal
extracting unit extracting an ancillary signal for
generating the audio signal and an extension signal
included in the ancillary signal from a received bit stream,
an extension signal length reading unit reading length
information of the extension signal, a selective decoding
unit skipping decoding of the extension signal or not using
a result of the decoding based on the length information,
and an upmixing unit generating the audio signal using the
ancillary signal.
To further achieve these and other advantages and in
accordance with the purpose of the present invention, an
apparatus for processing an audio signal includes a sync
information acquiring unit acquiring sync information
indicating a location of an ancillary signal for generating
the audio signal and a location of an extension signal
included in the ancillary signal, a selective decoding unit
skipping decoding of the extension signal or not using a
result of the decoding based on the sync information, and
an upmixing unit generating the audio signal using the

ancillary signal.
It is to be understood that both the foregoing
general description and the following detailed description
are exemplary and explanatory and are intended to provide
further explanation of the invention as claimed.
MODE FOR 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.
FIG. 1 is a block diagram of an audio signal encoding
apparatus and an audio signal decoding apparatus according
to an embodiment of the present invention.
Referring to FIG. 1, an encoding apparatus includes a
downmixing unit 10, a downmix signal encoding unit 20, an
ancillary signal encoding unit 30, an extension signal
encoding unit 40, and a multiplexing unit 50.
In case that multi-source audio signals XI, X2, ..., Xn
are inputted to the downmixing unit 10, the downmixing unit
10 generates a downmix signal by downmixing the multi-
source audio signals. The downmix signal includes a mono
signal, a stereo signal, or a multi-source audio signal.
The source includes a channel and is described as the
channel for convenience. In the specification of the

present invention, explanation is made with reference to a
mono or stereo downmix signal. Yet, the present invention
is not limited to the mono or stereo downmix signal. The
encoding apparatus is able to use an artistic downmix
signal provided from an outside selectively and directly.
In the course of downmixing, an ancillary signal can be
generated from a multi-channel audio signal and an
extension signal corresponding to additional information
can be generated as well. In this case, the ancillary
signal can include a spatial information signal and an
extension signal. The generated downmix, ancillary and
extension signals are encoded by the downmix signal
encoding unit 20, the ancillary signal encoding unit 30,
and the extension signal encoding unit 4 0 and are then
transferred to the multiplexing unit 50, respectively.
In the present invention, the ^spatial information'
means the information necessary for the encoding apparatus
to transfer a downmix signal generated from downmixing
multi-channel signals to the decoding apparatus and
necessary for the decoding apparatus to generate multi-
channel signals by upmixing the downmix signal. The spatial
information includes spatial parameters. The spatial
parameters include CLD (channel level difference)
indicating an energy difference between channels, ICC

(inter-channel coherences) meaning a correlation between
channels, CPC (channel prediction coefficients) used in
generating three channels from two channels, etc. And, the
^extension signal' means additional information necessary
to enable a signal to be reconstructed closer to an
original signal in generating multi-channel signals by
upmixing the downmix signal by the decoding apparatus. For
instance, the additional information includes a residual
signal, an artistic downmix residual signal, an artistic
tree extension signal, etc. In this case, the residual
signal indicates a signal corresponding to a difference
between an original signal and an encoded signal. In the
following description, it is assumed that the residual
signal includes a general residual signal or an artistic
downmix residual signal for compensation of an artistic
downmix signal.
In the present invention, the downmix signal encoding
unit 2 0 or the downmix signal decoding unit 70 means a
codec that encodes or decodes an audio signal not included
with an ancillary signal. In the present specification, a
downmix audio signal is taken as an example of not included
with the ancillary signal the audio signal. And, the
downmix signal encoding unit 20 or the downmix signal
decoding unit 70 is able to include MP3, AC-3, DTS, or AAC.

If a codec function is performed on an audio signal, the
downmix signal encoding unit 20 and the downmix signal
decoding unit 70 can include a codec to be developed in the
future as well as a previously developed codec.
The multiplexing unit 50 can generate a bit stream by
multiplexing a downmix signal, an ancillary signal, and an
extension signal and then transfer the generated bit stream
to the decoding apparatus. In this case, both of the
downmix signal and the ancillary signal can be transferred
in a bit stream format to the decoding apparatus.
Alternatively, the ancillary signal and the downmix signal
can be transferred in independent bit stream formats to the
decoding apparatus, respectively. Details of the bit
streams are explained in FIGs. 9 to 11.
In case that it is unable to use previously
transferred header information since an audio signal starts
to be decoded from a random timing point instead of being
decoded from the beginning like a bit stream for
broadcasting, it is able to decode the audio signal using
another header information inserted in the audio signal. In
case of header information is lost in the course of
transferring an audio signal, decoding should start from
any timing point of receiving a signal. So, header
information can be inserted in an audio signal at least

once. If header information exists in a front part of an
audio signal only once, it is unable to perform decoding
due to the absence of the header information in case of
receiving an audio signal at a random timing point. In this
case, header information can be included according to a
preset format (e.g., temporal interval, spatial interval,
etc.). It is able to insert identification information
indicating a presence or non-presence of header information
in a bit stream. And, an audio signal is able to
selectively include a header according to the
identification information. For instance, an ancillary
signal is able to selectively include a header according to
the header identification information. Details of the bit
stream structures are explained in FIGs. 9 to 12.
The decoding apparatus includes a demultiplexing unit
60, a downmix signal decoding unit 70, an ancillary signal
decoding unit 80, an extension signal decoding unit 90, and
an upmixing unit 100.
The demultiplexing unit 60 receives a bit stream and
then separates an encoded downmix signal, an encoded
ancillary signal, and an encoded extension signal from the
received bit stream. The downmix signal decoding unit 7 0
decodes the encoded downmix signal. And, the ancillary
signal decoding unit 8 0 decodes the encoded ancillary

signal.
Meanwhile, the extension signal can be included in
the ancillary signal. It is necessary to efficiently decode
the extension signal to efficiently generate multi-channel
audio signals. So, the extension signal decoding unit 90 is
able to selectively decode the encoded extension signal. In
particular, the encoded extension signal can be decoded or
the decoding of the encoded extension signal can be skipped.
Occasionally, if the decoding of the extension signal is
skipped, the encoded signal can be reconstructed to be
closer to an original signal and coding efficiency can be
raised.
For instance, if a level of the decoding apparatus is
lower than that of a bit stream, the decoding apparatus is
unable to decode the received extension signal. So, the
decoding of the extension signal can be skipped. Even if
the decoding of the extension signal is available because
the level of the decoding apparatus is higher than that of
the bit stream, the decoding of the extension signal is
able to be skipped by another information obtained from the
audio signal. In this case, for instance, the another
information may include information indicating whether to
execute the decoding of the extension signal. This is
explained in detail with reference to FIG. 14 later.

And for instance, in order to omit the decoding of
the extension signal, length information of the extension
signal is read from the bit stream and the decoding of the
extension signal is able to be skipped using the length
information. Alternatively, it is able to skip the decoding
of the extension signal using sync information indicating a
position of the extension signal. This is explained in
detail with reference to FIG. 2 later.
The length information of the extension signal can be
defined in various ways. For instance, fixed bits can be
assigned, or variable bits can be assigned according to a
predetermined length information type, or bits suitable for
a length of a real extension signal can be adaptively
assigned while the length of the extension signal is read.
Details of the fixed bits assignment are explained in FIG.
3 and FIG. 4. Details of the variable bits assignment are
explained in FIG. 5 and FIG. 6. And, details of the
adaptive bits assignment are explained in FIG. 7 and FIG. 8.
The length information of the extension signal can be
located within an ancillary data area. In this case, the
ancillary data area indicates an area where additional
information necessary to reconstruct a downmix signal into
an original signal exists. For instance, a spatial
information signal or an extension signal can be taken as

an example of the ancillary data. So, the length
information of the extension signal can be located within
the ancillary signal or an extension area of the ancillary
signal.
In particular, the length information of the
extension signal is located within a header extension area
of the ancillary signal, a frame data extension area of the
ancillary signal, or both of the header extension area and
the frame data extension area of the ancillary signal.
These are explained in detail with reference to FIGs. 9 to
11 later.
FIG. 2 is a schematic block diagram of an extension
signal decoding unit 90 according to an embodiment of the
present invention.
Referring to FIG. 2, the extension signal decoding
unit 90 includes an extension signal type information
acquiring unit 91, an extension signal length reading unit
92, and a selective decoding unit 93. And, the selective
decoding unit 93 includes a level deciding unit 94, an
extension signal information acquiring unit 95, and an
extension signal information skipping unit 96. The
extension signal decoding unit 90 receives a bit stream for
an extension signal from the demultiplexing unit 60 and
then outputs a decoded extension signal. Occasionally, the

extension signal decoding unit 90 may not output an
extension signal or can output an extension signal by
padding a bit stream for the extension signal with zeros
completely. For the case of not outputting an extension
signal, a method of skipping the decoding of the extension
signal is usable. The extension signal type acquiring unit
91 acquires information indicating a type of an extension
signal from a bit stream. For instance, the information
indicating the type of the extension signal can include a
residual signal, an artistic downmix residual signal, an
artistic tree extension signal, or the like. In the present
invention, the residual signal is a generic term of a
general residual signal or an artistic downmix residual
signal for compensation of an artistic downmix signal. The
residual signal is usable for compensation of an artistic
downmix signal in multi-channel audio signals or specific
channel compensation in decoding. Optionally, the two cases
are usable as well. If the type of the extension signal is
decided by the extension signal type information, the
extension signal length reading unit 92 reads a length of
the extension signal decided by the type information of the
extension signal. This can be achieved regardless of
whether to perform the decoding of the extension signal.
Once the length of the extension signal is read, the

selective decoding unit 93 selectively performs decoding on
the extension signal. This can be decided by the level
deciding unit 94. In particular, the level deciding unit 94
selects whether to execute the decoding of the extension
signal by comparing a level of a bit stream to a level of a
decoding apparatus. For instance, if the level of the
decoding apparatus is equal to or higher than that of the
bit stream, the decoding apparatus acquires information for
the extension signal via the extension signal information
acquiring unit 95 and then decodes the information to
output the extension signal. The outputted extension signal
is transferred to an upmixing unit 100 to be used in
reconstruct an original signal or generating an audio
signal. Yet, if the level of the decoding apparatus is
lower than that of the bit stream, it is able to skip the
decoding of the extension signal via the extension signal
information skipping unit 96. In this case, it is able to
skip the decoding of the extension signal based on the
length information read by the extension signal length
reading unit 92. Thus, in case that the extension signal is
used, the reconstruction can be achieved to get closer to
the original signal to enhance a sound quality. If
necessary, it is able to reduce a load of operation of the
decoding apparatus by omitting the decoding of the

extension signal.
As an example of the method of omitting the decoding
of the extension signal in the extension signal information
skipping unit 96, in case of using the length information
of the extension signal, bit or byte length information of
the extension signal can be inserted in data. And, the
decoding can keep proceeding by skipping a bit field of the
extension signal as many as a value obtained from the
length information. Methods of defining the length
information of the extension signal shall be explained with
reference to FIGs. 3 to 8.
As another example of the method of omitting the
decoding of the extension signal, it is able to skip the
decoding of the extension signal based on sync information
indicating a position of the extension signal. For instance,
it is able to insert a sync word having predetermined bits
in the point where the extension signal ends. The decoding
apparatus keeps searching the bit field of the residual
signal until finding a sync word of the extension signal.
Once finding the sync word, the decoding apparatus stops
the search process and then keeps performing the decoding.
In particular, it is able to skip the decoding of the
extension signal until the sync word of the extension
signal is found. As another example of a decoding method

according to the selection, in case of performing the
decoding of the extension signal, it is able to perform the
decoding after parsing the extension signal. When the
decoding of the extension signal is performed, the sync
word of the extension signal is read but may not be
available.
FIG. 3 and FIG. 4 are diagrams to explain fixed bits
assignment of length information for an extension signal
according to an embodiment of the present invention.
The length information of the extension signal can be
defined by a bit or byte unit. If the length information is
decided by the byte unit, this means that the extension
signal is assigned bytes. FIG. 3 shows a method of defining
length information for an extension signal in a simplest
way. And, FIG. 4 shows the method shown in FIG. 3
schematically. A syntax element for indicating the length
information of the extension signal is defined and
predetermined bits are assigned to the syntax element. For
instance, 'bsResidualSignalLength' is defined as the syntax
element and 16 bits are assigned as fixed bits. Yet, this
method may consume a relatively considerable amount of bits.
So, the methods shown in FIG. 5, FIG. 6, FIG. 7, and FIG. 8
are explained as follows.
FIG. 5 and FIG. 6 are diagrams to explain variable

bits assignment of length information for an extension
signal by depending on a length type according to an
embodiment of the present invention.
FIG. 5 shows a method of defining one more syntax
element for defining how many bits are used for
'bsResidualSignalLength' to further reduce bit consumption.
And, FIG. 6 schematically illustrates the method shown in
FIG. 5. For instance, . ^bsResidualSignalLengthtype' is newly
defined as a length type. If a value of the
'bsResidualSignalLengthtype' is zero, four bits are
assigned to the ^bsResidualSignalLength'. If a value of the
xbsResidualSignalLengthtype' is 1, eight bits are assigned
to the ^bsResidualSignalLength' . If a value of the
^bsResidualSignalLengthtype' is 2, twelve bits are assigned
to the 'bsResidualSignalLength' . If a value of the
vbsResidualSignalLengthtype' is 3, sixteen bits are
assigned to the 'bsResidualSignalLength'. In this case, the .
assigned bits are exemplary. So, bits different from the
above-defined bits can be assigned. To reduce the bit
consumption more than those of the above methods, the
method shown in FIG. 7 and FIG. 8 is provided.
FIG. 7 and FIG. 8 are diagrams to explain adaptive
bits assignment of length information for an extension
signal by depending on a real length of the extension

signal according to an embodiment of the present invention.
If an extension signal is inputted, a length
information value of the extension signal can be read up to
an initially determined value. If the length information
value equals to a predetermined value, it is able to read
additionally up to a further determined value. If the
length information value equals to another predetermined
value, it is able to read additionally up to another
further determined value. In this case, if the length
information value is not another predetermined value, the
corresponding value is outputted as the length information
value as it is. Thus, the length information of the
extension signal is adaptively read according to a real
data length, whereby the bit consumption can be maximally
reduced. The example shown in FIG. 7 or FIG. 8 is explained.
In FIG. 7, a residual signal is taken as an example
of the extension signal. If a residual signal is inputted,
four bits of the residual signal length are read. If a
length information value (bsResidualSignalLength) is 24-l
(=15) , eight bits are further read as a value of
bsResidualSignalLengthl. If the length information value
(bsResidualSignalLength) is (24-l) + (28-l) (=15+255), twelve
bits are further read as a value of bsResidualSignalLength2.
In the same manner, if the length information value

(bsResidualSignalLength) is (24-l) + (28-l) + (212-1)
(=15+255+4095), sixteen bits are further read as a value of
bsResidualSignalLength3.
FIG. 8 schematically illustrates another example of
the adaptive bits assignment of length information for an
extension signal.
In FIG. 8, if an extension signal is inputted, four
bits are preferentially read. If a value resulting from
reading length information is smaller than four bits, the
corresponding value becomes the length information. Yet, if
a value resulting from reading length information is
greater than four bits, eight bits are further read in
addition. If the additionally read value is smaller than
eight bits, a total read length information value
corresponds to 12 (=4 + 8) . Yet, if the additionally read
value is greater than eight bits, sixteen bits are further
read in addition again. This is explained in detail as
follows. First of all, if length information is inputted,
four bits are read. A real length information value ranges
0~14. If the length information value becomes 24-l (=15),
the extension signal is further read in addition. In this
case, the extension signal can be additionally read up to
28-2 (=254) . Yet, if the length information value
corresponds to a value smaller than 24-l (=15), a value of

the read 0~(24-2) (=14) is outputted as it is. Once the
length information value becomes (24-l) + (28-l) , the
extension signal is further read in addition. In this case,
the extension signal can be additionally read up to (216-1).
Yet, if the length information value corresponds to a value
smaller than 216-1, a value of the read 0~(216-l) (=14) is
outputted as it is. In this case, as mentioned in the
foregoing description, the assigned bits are exemplary for
explanation. So, another bits different from the above-
defined bits can be assigned.
Meanwhile, the length information of the extension
signal can be length information of the extension signal
header or length information of the extension signal frame
data. So, the length information of the extension signal
can be located in a header area and/or a frame data area.
Bit stream structures for this are explained with reference
to FIGs. 9 to 12.
FIG. 9 and FIG. 10 show embodiments of the present
invention, in which a bit stream structure configuring an
audio signal with a downmix signal, an ancillary signal,
and an extension signal is shown.
An audio signal includes a downmix signal and an
ancillary signal. As an example of the ancillary signal, a
spatial information signal can be taken. Each of the

downmix signal and the ancillary signal is transferred by a
frame unit. The ancillary signal can include header
information and data information or can include data
information only. Thus, in the file/general streaming
structure configuring one audio signal, the header
information precedes and is followed by the data
information. For instance, in case of a file/general
streaming structure configuring one audio signal with a
downmix signal and an ancillary signal, a downmix signal
header and an ancillary signal header can exist as the
header information in a front part. And, downmix signal
data and ancillary signal data can configure one frame as
the data information behind the front part. In this case,
by defining an extension area of the ancillary data, it is
able to locate an extension signal. The extension signal
can be included within the ancillary signal or can be used
as an independent signal. FIG. 9 shows a case that the
extension signal is used as the independent signal and FIG.
10 shows a case that the extension signal is located in the
extension area within the ancillary signal. So, in case
that there exists the extension signal, in the file/general
streaming structure, an extension signal header can exist
as header information in the front part as well as the
downmix header and the spatial information header. Behind

the front part, extension signal data can be further
included as data information as well as the downmix signal
data and the ancillary signal data to configure one frame.
Since the extension signal can be selectively decoded, it
can be located at a last part of the frame or can
consecutively exist right behind the ancillary signal. The
length information explained in FIGs. 3 to 8 can exist
within the header area of the extension signal and/or the
data area of the extension signal. In this case, the length
information existing within the header area (extension
signal header) indicates the length information of the
extension signal header, and the length information
existing within the data area (extension signal data)
indicates the length information of the extension signal
data. Thus, the length information existing each of the
areas is read from a bit stream and the decoding apparatus
is able to skip the decoding of the extension signal based
on the length information.
FIG. 11 is a diagram of a bit stream structure
configuring an independent audio signal with a downmix
signal or an ancillary signal according to an embodiment of
the present invention.
An audio signal includes a downmix signal and an
ancillary signal. As an example of the ancillary signal, a

spatial information signal can be taken. The downmix signal
and the ancillary signal can be transferred as independent
signals, respectively. In this case, the downmix signal has
a structure that a downmix signal header (downmix signal
header®) as header information is located at a front part
and that downmix signal datas (downmix signal data ©, ©,
© , ..., © ) as data information follow the downmix signal
header. Likewise, the ancillary signal has a structure that
an ancillary signal header (ancillary signal header ©) as
header information is located at a front part and that
ancillary signal datas (ancillary signal data ®, ©, ..., ®)
as data information follow the ancillary signal header.
Since the extension signal can be included within the
ancillary signal, a structure that the extension signal
follows the ancillary signal data can be provided. So, an
extension signal header © follows the ancillary signal
header ® and the extension signal data © follows the
ancillary signal data © . Likewise, the extension signal
data © follows the ancillary signal data ©. In this case,
length information of the extension signal can be included
in each of the extension signal header ® , the extension
signal data ©, and/or the extension signal data ©, ..., and
Meanwhile, unlike the file/general streaming

structure, in case that it is unable to use previously
transferred header information since an audio signal is
decoded from a random timing point instead of being decoded
from the beginning, it is able to decode the audio signal
using another header information included in the audio
signal. In case of using an audio signal for broadcasting
or the like or losing header information in the course of
transferring an audio signal, decoding should start from
any moment of receiving a signal. So, it is able to improve
coding efficiency by defining identification information
indicating whether the header exits. A streaming structure
for broadcasting is explained with reference to FIG. 12 as
follows.
FIG. 12 is a diagram of a broadcasting streaming
structure configuring an audio signal with a downmix signal
and an ancillary signal according to an embodiment of the
present invention.
In case of a broadcast streaming, if header
information exists in a front part of an audio signal once
only, it is unable to execute decoding due to the absence
of header information in case of receiving an audio signal
at a random timing point. So, the header information can be
inserted in the audio signal once at least. In this case,
the header information can be included according to a

preset format (e.g., temporal interval, spatial interval,
etc.). In particular, the header information can be
inserted in each frame, periodically inserted in each frame
with a fixed interval, or non-periodically inserted in each
frame with a random interval. Alternatively, the header
information can be inserted once according to a fixed time
interval (e.g., 2 seconds).
A broadcast streaming structure configuring one audio
signal has a structure that at least once header
information is inserted between data informations. For
instance, in case of a broadcast streaming structure
configuring one audio signal, a downmix signal comes first
and an ancillary signal follows the downmix signal. Sync
information for distinguishing between the downmix signal
and the ancillary signal can be located at a front part of
the ancillary signal. And, identification information
indicating whether header information for the ancillary
signal exists can be located. For instance, if header
identification information is 0, a next read frame only has
a data frame without header information. If the header
identification information is 1, a next read frame has both
header information and a data frame. This is applicable to
the ancillary signal or the extension signal. These header
informations may be the same of the header information

having been initially transferred or can be variable. In
case that the header information is variable, new header
information is decoded and data information transferred
after the new header information is then decoded according
to the decoded new header information. In case that the
header identification information is 0, a transferred frame
only has a data frame without header information. In this
case, to process the data frame, previously transferred
header information can be used. For instance, if the header
identification information is 1 in FIG., 12, an ancillary
signal header © and an extension signal header © can exist.
Yet, if a next incoming frame has no header information
since the header identification information set to 0, it is
able to use information of the extension signal header ©
previously transferred to process extension signal data ©.
FIG. 13 is a flowchart of a method of processing an
extension signal based on length information of the
extension signal in accordance with identification
information indicating whether a header is included within
an ancillary signal in case of using an audio signal for
broadcasting or the like according to an embodiment of the
present invention.
Referring to FIG. 13, an ancillary signal for an
audio signal generation and an extension signal included in

the ancillary signal are extracted from a received bit
stream (1301). The extension signal can be included within
the ancillary signal. Identification information indicating
whether a header is . included in the ancillary signal is
extracted (1303). For instance, if the header
identification information is 1, it indicates that an
ancillary signal header is included in the ancillary signal.
If the header identification information is 0, it indicates
that an ancillary signal header is not included in the
ancillary signal. In case that the extension signal is
included in the ancillary signal, if the header
identification information is 1, it indicates that an
extension signal header is included in the extension signal.
If the header identification information is 0, it indicates
that an extension signal header is not included in the
extension signal. It is decided that whether a header is
included in the ancillary signal according to the header
identification information (1305). If the header is
included in the ancillary signal, length information is
extracted from the header (1307). And, it is able to skip
decoding of the extension signal based on the length
information (1309). In this case, the header plays a role
in enabling each ancillary signal and/or each extension
signal to be interpreted. For instance, the header

information can include information for a residual signal,
length information for a residual signal, sync information
indicating a location of a residual signal, a sampling
frequency, a frame length, the number of a parameter band,
tree information, quantization mode information, ICC
(inter-channel correlation), parameter smoothing
information, gain information for a clipping-prevention,
QMF (quadrature mirror filter) associated information, etc.
Moreover, if the header is not included in the ancillary
signal according to the header identification information,
it is able to skip decoding of the extension signal based
on the previously extracted length information for the
header (1311).
FIG. 14 is a flowchart of a method of decoding an
extension signal selectively based on length information of
the extension signal according to an embodiment of the
present invention.
A profile means that technical elements for algorithm
in a coding process are standardized. In particular, the
profile is a set of technical elements necessary to decode
a bit stream and corresponds to a sort of a sub-standard. A
level defines a range of the technical elements, which are
prescribed in the profile, to be supported. In particular,
the level plays a role in defining capability of a decoding

apparatus and complexity of a bit stream. In the present
invention, level information can include definitions for
the profile and level. A decoding method of an extension
signal can selectively vary according to the level
information of the bit stream and the level information of
the decoding apparatus. For instance, even if the extension
signal exists in a transferred audio signal, decoding of
the extension signal may be or may not be executed as a
result of deciding the level information. Moreover,
although the decoding is executed, a predetermined low
frequency part can be used only. Besides, it is able to
skip the decoding of the extension signal as many as length
information of the extension signal in order not to execute
the decoding of the extension signal. Alternatively,
although the extension signal is entirely read, the
decoding cannot be executed. Furthermore, a portion of the
extension signal is read, decoding can be performed on the
read portion only, and the decoding cannot be performed on
the rest of the extension signal. Alternatively, the
extension signal is entirely read, a portion of the
extension signal can be decoded, and the rest of the
extension signal cannot be decoded.
For instance, referring to FIG. 14, an ancillary
signal for generating an audio signal and an extension

signal included in the ancillary signal can be extracted
from a received bit stream (1410) . And, information for the
extension signal can be extracted. In this case, the
information for the extension signal may include extension
data type information indicating a data type of the
extension signal. For instance, the extension data type
information includes residual coding data, artistic downmix
residual coding data, artistic tree extension data, or the
like. So, the type of the extension signal is decided and
it is able to read length information of the extension
signal from an extension area of the audio signal (1420) .
Subsequently, a level of the bit stream is decided. This
can be decided with reference to following information. For
instance, if the type of the extension signal is the
residual coding data, the level information for the bit
stream can include the number of output channels, a
sampling rate, a bandwidth of a residual signal, and the
like. So, if the above-explained level informations of the
bit stream are inputted, they are compared to level
information for a decoding apparatus to decide whether the
extension signal will be decoded (1430). In this case, a
level of the decoding apparatus can be previously set. In
general, the level of the decoding apparatus should be
equal to or greater than a level of the audio signal. This

is because the decoding apparatus should be able to decode
the transferred audio signal entirely. Yet, in case that
limitation is put on the decoding apparatus (e.g., in case
that the level of the decoding apparatus is smaller than
that of the audio signal), decoding is occasionally
possible. Yet, a corresponding quality may be degraded. For
instance, if the level of the decoding apparatus is lower
than that of the audio signal, the decoding apparatus may
be unable to decode the audio signal. Yet, in some cases,
the audio signal can be decoded based on the level of the
decoding apparatus.
In case that the level of the decoding apparatus is
decided lower than that of the bit stream, it is able to
skip the decoding of the extension signal based on the
length information of the extension signal (1440). On the
other hand, in case that the level of the decoding
apparatus is equal to or higher than that of the bit stream,
it is able to execute the decoding of the extension signal
(1460). Yet, although the decoding of the extension signal
is executed, the decoding can be performed on a
predetermined low frequency portion of the extension signal
only (1450) . For instance, there is a case that since the
decoding apparatus is a low power decoder, if the extension
signal is entirely decoded, efficiency is degraded, or

since the decoding apparatus is unable to decode the entire
extension signal a predetermined low frequency portion of
the extension signal is usable. And, this is possible if
the level of the bit stream or the level of the decoding
apparatus meets a prescribed condition only.
INDUSTRIAL APPLICABILITY
Accordingly, various environments for encoding and
decoding signals exist in general and there can exist
various methods of processing signals according to the
various environment conditions. In the present invention, a
method of processing an audio signal is taken as an example,
which does not restrict the scope of the present invention.
In this case, the signals include audio signals and/or
video signals.
While the present invention has been described and
illustrated herein with reference to the preferred
embodiments thereof, it will be, apparent to those skilled
in the art that various modifications and variations can be
made therein without departing from the spirit and scope of
the invention. Thus, it is intended that the present
invention covers the modifications and variations of this
invention that come within the scope of the appended claims
and their equivalents.

What is Claimed is:
1. A method for processing an audio signal,
comprising the steps of:
extracting an ancillary signal for generating the
audio signal and an extension signal included in the
ancillary signal from a received bit stream;
reading length information for the extension signal;
skipping decoding of the extension signal or not
using a result of the decoding based on the length
information; and
generating the audio signal using the ancillary
signal.
2. The method of claim 1, wherein the extension
signal is a residual signal.
3. The method of claim 1 or claim 2, wherein the
length information of the extension signal is assigned
fixed bits.
4. The method of claim 1 or claim 2, wherein the
length information of the extension signal is assigned
variable bits according to length type information of the

extension signal.
5. The method of claim 1 or claim 2, wherein the
length information of the extension signal is assigned
adaptive bits according to a length of the extension signal.
6. A method of processing an audio signal,
comprising the steps of:
acguiring sync information indicating a location of
an ancillary signal for generating the audio signal and a
location of an extension signal included in the ancillary
signal;
skipping decoding of the extension signal or not
using a result of the decoding based on the sync
information; and
generating the audio signal using the ancillary
signal.
7. The method of claim 6, wherein the sync
information indicates a start point and/or an end point of
the extension signal.
8. The method of claim 6, wherein the extension
signal is a residual signal.

9. An apparatus for processing an audio signal,
comprising:
a signal extracting unit extracting an ancillary
signal for generating the audio signal and an extension
signal included in the ancillary signal from a received bit
stream;
an extension signal length reading unit reading
length information of the extension signal;
a selective decoding unit skipping decoding of the
extension signal or not using a result of the decoding
based on the length information; and
an upmixing unit generating the audio signal using
the ancillary signal.
10. An apparatus for processing an audio signal,
comprising:
a sync information acquiring unit acquiring sync
information indicating a location of an ancillary signal
for generating the audio signal and a location of an
extension signal included in the ancillary signal;
a selective decoding unit skipping decoding of the
extension signal or not using a result of the decoding
based on the sync information; and

an upmixing unit generating the audio signal using the
ancillary signal.

A method for processing an audio signal, comprising the steps of extracting an ancillary signal for generating the audio signal and an extension signal included in the ancillary signal from a received bit stream, reading length information for the extension signal, skipping decoding of the extension signal or not using a result of the decoding based on the length information, and generating the audio signal using the ancillary signal. Accordingly, in case of processing the audio signal by the present invention, it is able to reduce a corresponding load of operation to enable efficient processing and enhance a sound quality.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=+9pNqPK0eHC53PgFY2x3Uw==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

268906

Indian Patent Application Number

2325/KOLNP/2008

PG Journal Number

39/2015

Publication Date

25-Sep-2015

Grant Date

22-Sep-2015

Date of Filing

11-Jun-2008

Name of Patentee

LG ELECTRONICS INC.

Applicant Address

20, YOIDO-DONG, YOUNGDUNGPO-GU, SEOUL

Inventors:

#	Inventor's Name	Inventor's Address
1	PANG HEE SUCK	101, 4/7, #14-10, YANGJAE-DONG, SEOCHO-GU, SEOUL 137-130
2	LIM JAE HYUN	609, PARKVILLE OFFICETEL, # 1062-20, NAMHYEON-DONG, GWANAK-GU, SEOUL 151-801
3	OH HYEN O	306-403, HANSIN APT., GANGSEON-MAEUL 3-DANJI, JUYEOP 1-DONG, ILSAN-GU, GOYANG-SI, GYEONGGI-DO 411-744
4	JUNG YANG WON	2-803, YEOKSAM HANSHIN APT., DOGOK-DONG, GANGNAM-GU, SEOUL 135-270
5	KIM DONG SOO	502, WOOLIM VILLA, #602-265, NAMHYEON-DONG, GWANAK-GU, SEOUL 151-801

PCT International Classification Number

H03M 7/30

PCT International Application Number

PCT/KR2007/000866

PCT International Filing date

2007-02-16

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10-2007-0013364	2007-02-08	U.S.A.
2	60/803825	2006-06-02	U.S.A.
3	60/791907	2006-04-14	U.S.A.
4	60/775775	2006-02-23	U.S.A.