HK1127825B - Method and apparatus for processing an audio signal - Google Patents

Description

Method and apparatus for processing 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 residual signals.

Background

In general, an audio signal includes a downmix signal and an ancillary data signal. And the auxiliary data signal may include a spatial information signal and an extension signal. In this case, the "extension signal" refers to an additional signal required to enable a signal to be reconstructed close to an original signal when a multi-channel signal is generated by performing a channel extension process on a downmix signal. For example, the extension signal may include a residual signal. "residual signal" refers to a signal corresponding to the difference between the original signal and the coded signal. In multi-channel audio coding, the residual signal may be used in the following cases. For example, the residual signal may be used for compensation of an artistic downmix signal or specific channel compensation at the time of decoding. Also, the residual signal can be used for both compensations. Therefore, it is possible to reconstruct an input audio signal into a signal closer to an original signal using a residual signal to improve sound quality.

Disclosure of Invention

Technical problem

However, if the decoder performs decoding on the extension signal unconditionally, although sound quality may be improved according to the type of the decoder, complexity rises and the operation load increases.

Further, since the header information of the audio signal is generally immutable, the header information is inserted into the bitstream only once. But in case that header information is inserted into a bitstream only once, if an audio signal needs to be decoded from a random time point for broadcasting or VOD, data frame information cannot be decoded due to the absence of the header information.

Technical scheme

Accordingly, the present invention is directed to a method and apparatus for processing an audio signal that substantially obviates one or more 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 the processing efficiency of the audio signal is improved by skipping decoding of an extension signal.

It is another object of the present invention 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.

It is another object of the present invention to provide a method and apparatus for processing an audio signal, by which an audio signal for broadcasting can be reproduced from a random point of time.

It is still another object of the present invention 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 has the following effects or advantages.

First, in case of decoding, the present invention selectively decodes an extension signal to achieve more efficient decoding. In case of decoding an extension signal, the present invention can improve sound quality of an audio signal. The present invention can reduce complexity in the case of not decoding an extension signal. Further, even if the extension signal is decoded, the present invention can improve sound quality by decoding only a predetermined low frequency portion and also reduce the computational load. In addition, in the case of using an audio signal for broadcasting or the like, the present invention can process the audio signal from a random point of time in a manner of identifying the presence or absence of header information within the audio signal.

Brief Description of Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle 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 4 are diagrams for explaining fixed bit allocation of extension signal length information according to an embodiment of the present invention;

fig. 5 and 6 are diagrams for explaining variable bit allocation of extension signal length information depending on a length type according to an embodiment of the present invention;

fig. 7 and 8 are diagrams for explaining adaptive bit allocation of extension signal length information depending on a real length of an extension signal according to an embodiment of the present invention;

fig. 9 is a diagram of configuring a bitstream structure of 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 bitstream 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 bitstream structure of an audio signal in the configuration of a downmix signal or an ancillary signal according to an embodiment of the present invention;

fig. 12 is a diagram of a broadcast stream 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 according to identification information indicating whether a header is included in an ancillary signal in case of 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 selectively decoding an extension signal using length information of the extension signal according to a level of a bitstream 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 obvious from the description, or may be learned by the 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 hereof 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 of processing an audio signal according to the present invention includes the steps of: extracting an ancillary signal for generating an audio signal and an extension signal included in the ancillary signal from a received bitstream; 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 an audio signal using the auxiliary signal.

To further achieve these and other advantages and in accordance with the purpose of the present invention, a method of processing an audio signal includes the steps of: acquiring synchronization information indicating a position of an ancillary signal used to generate an audio signal and a position 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 synchronization information; and generating an audio signal using the auxiliary 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 extraction unit that extracts an ancillary signal for generating an audio signal and an extension signal included in the ancillary signal from a received bitstream; an extension signal length reading unit that reads 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 an 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 synchronization information acquisition unit that acquires synchronization information indicating a position of an ancillary signal used to generate an audio signal and a position 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 synchronization information; and an upmixing unit generating an 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.

Modes for carrying out the invention

Reference will now be made in detail to the present preferred embodiments of the 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, the encoding apparatus includes a downmix 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 the case where multi-source audio signals X1, X2 … … Xn are input to the downmixing unit 10, the downmixing unit 10 generates a downmix signal by downmixing the multi-source signals. The downmix signal includes a mono signal, a stereo signal and a multi-source audio signal. The "source" includes a channel and is described as a channel for convenience. In the description of the present invention, the explanation is made with reference to a mono or stereo downmix signal. However, the present invention is not limited to mono or stereo downmix signals. The encoding apparatus can selectively and directly use an artistic downmix signal provided from the outside. In the downmixing process, an ancillary signal may be generated from a multi-channel audio signal, and an extension signal corresponding to additional information may also be generated. In this case, the ancillary signal may include a spatial information signal and an extension signal. The generated downmix signal, ancillary signal and extension signal are encoded by the downmix signal encoding unit 20, the ancillary signal encoding unit 30 and the extension signal encoding unit 40, respectively, and then transferred to the multiplexing unit 50.

In the present invention, "spatial information" refers to information necessary when an encoding apparatus transmits a downmix signal generated by downmixing a multi-channel signal to a decoding apparatus, and also necessary when the decoding apparatus generates a multi-channel signal 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 coherence) indicating a correlation between channels, CPC (channel prediction coefficient) used when three channels are generated from two channels, and the like. And "extension signal" refers to additional information necessary to enable a signal to be reconstructed closer to an original signal when a multi-channel signal is generated by upmixing a downmix signal by a decoding apparatus. For example, the additional information includes a residual signal, an artistic downmix residual signal, an artistic tree extension signal, and the like. In this case, the residual signal indicates a signal corresponding to a difference between the original signal and the 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 artistic downmix signal compensation.

In the present invention, the downmix signal encoding unit 20 or the downmix signal decoding unit 70 refers to a codec that encodes or decodes an audio signal that does not include an ancillary signal. In the present invention, a downmix audio signal is considered as an example of an audio signal not including an ancillary signal. Also, the downmix signal encoding unit 20 or the downmix signal decoding unit 70 may include MP3, AC-3, DTS or AAC. If the audio signal is subjected to a codec function, the downmix signal encoding unit 20 or the downmix signal decoding unit 70 may include a codec developed in the future as well as a codec that has been developed in the past.

The multiplexing unit 50 may generate a bitstream by multiplexing the downmix signal, the ancillary signal and the extension signal and then transmit the generated bitstream to the decoding apparatus. In this case, both the downmix signal and the ancillary signal may be transmitted to the decoding apparatus in a bitstream format. Alternatively, the ancillary signal and the downmix signal may be separately transmitted to the decoding apparatus in independent bit stream formats. Details of the bit stream will be explained in fig. 9 to 11.

In case that previously transmitted header information cannot be used because an audio signal is decoded from a random time point instead of being decoded from the beginning like a bitstream for broadcasting, the audio signal can be decoded using another header information inserted in the audio signal. In case header information is lost during transmission of an audio signal, decoding should start from an arbitrary time point of receiving the signal. Therefore, the header information may be inserted into the audio signal at least once. If the header information exists only once in the front of the audio signal, decoding cannot be performed due to the lack of the header information for the case of receiving the audio signal at a random time point. In this case, the header information may be introduced according to a predetermined format (e.g., time interval, spatial interval, etc.). Identification information indicating whether header information exists in the bitstream may be inserted. And, the audio signal may selectively include a header according to the identification information. For example, the ancillary signal may be selectively introduced into the header based on the header identification information. Details of the bitstream structure will be explained in fig. 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 bitstream and then separates an encoded downmix signal, an encoded ancillary signal and an encoded extension signal from the received bitstream. The downmix signal decoding unit 70 decodes the encoded downmix signal. And the ancillary signal decoding unit 80 decodes the encoded ancillary signal.

Meanwhile, the extension signal may be included in the auxiliary signal. It is necessary to efficiently decode an extension signal in order to efficiently generate a multi-channel audio signal. Therefore, the extension signal decoding unit 90 can selectively decode the encoded extension signal. Specifically, the encoded extension signal may be decoded, or decoding of the encoded extension signal may be skipped. Sometimes, if the decoding process of the extension signal is skipped, the encoded signal can be reconstructed closer to the original signal and the coding efficiency is improved.

For example, if the level of the decoding apparatus is lower than the bitstream, the decoding apparatus cannot decode the received extension signal. Therefore, decoding of the extension signal can be skipped. Even if the decoding of the extension signal is available because the decoding apparatus is higher in level than the bitstream, the decoding of the extension signal can be skipped by another information acquired from the audio signal. In this case, for example, the another information may include information indicating whether to perform decoding of the extension signal. This will be explained in detail later with reference to fig. 14.

For example, in order to omit the decoding of the extension signal, length information of the extension signal may be read from the bitstream and the decoding of the extension signal may be skipped using the length information. Alternatively, the decoding of the extension signal may be skipped using the synchronization information indicating the position of the extension signal. This will be explained in detail later with reference to fig. 2.

The length information of the extension signal may be defined in various ways. For example, fixed bits may be allocated, or variable bits may be allocated according to a predetermined length information type, or bits suitable for the length of a real extension signal may be adaptively allocated while reading the length of the extension signal. Details of the fixed bit allocation are explained in fig. 3 and 4. The details of the variable bits are explained in fig. 5 and 6. And details of the adaptive bit allocation are explained in fig. 7 and 8.

The length information of the extension signal may be located within the auxiliary data area. In this case, the ancillary data region indicates an area where additional information required to reconstruct the downmix signal into the original signal exists. For example, a spatial information signal or an extension signal may be taken as an example of the auxiliary data. Therefore, the length information of the extension signal may be located in the ancillary signal or the extension area of the ancillary signal.

Specifically, the length information of the extension signal is located in 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. This will be explained in detail later with reference to fig. 9 to 11.

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. Also, the selective decoding unit 93 includes a level decoding 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 of an extension signal from the demultiplexing unit 60 and then outputs a decoded extension signal. Sometimes, the extension signal decoding unit 90 may not output the extension signal, or may output the extension signal by completely zero-padding the extension signal bit stream. For the case where the extension signal is not output, a method of skipping decoding of the extension signal may be used. The extension signal type acquisition unit 91 acquires information indicating the type of the extension signal from the bitstream. For example, the information indicating the type of the extension signal may include a residual signal, an artistic downmix residual signal, an artistic tree extension signal, and the like. In the present invention, the residual signal is a general term for a general residual signal and an artistic downmix residual signal for compensating the artistic downmix signal. The residual signal may be used to compensate for an artistic downmix signal in a multi-channel audio signal or for a specific channel compensation at the time of decoding. Optionally, both of these scenarios may also be used. The extension signal length reading unit 92 reads the length of the extension signal determined by the type information of the extension signal if the type of the extension signal is determined by the extension signal type information. This can be achieved regardless of whether or not decoding of the extension signal is performed. Once the length of the extension signal is read, the selective decoding unit 93 selectively decodes the extension signal. This may be determined by the level determination unit 94. Specifically, the level determination unit 94 selects whether to perform decoding of the extension signal by comparing the level of the bitstream with the level of the decoding apparatus. For example, if the level of the decoding apparatus is equal to or higher than the level of the bitstream, the decoding apparatus acquires information on the extension signal via the extension signal information acquisition unit 95 and then decodes the information to output the extension signal. The output extension signal is transmitted to the upmixing unit 100 to be used in reconstructing an original signal or generating an audio signal. However, if the level of the decoding apparatus is lower than that of the bitstream, the decoding of the extension signal may be skipped via the extension signal skipping unit 96. In this case, the decoding of the extension signal may be skipped based on the length information read by the extension signal length reading unit 92. Therefore, in the case of using the extension signal, reconstruction closer to the original signal can be achieved to improve sound quality. The amount of operation of the decoding apparatus can be reduced by omitting the decoding of the extension signal, if necessary.

As one example of a method of omitting the decoding of the extension signal in the extension signal information skipping unit 96, in the case of using the length information of the extension signal, bit or byte length information of the extension signal may be inserted into data. And, the decoding can be continued by skipping as many bit fields of the extension signal as the value obtained from the length information. A method of defining length information of an extension signal will be explained with reference to fig. 3 to 8.

As another example of a method of omitting the decoding of the extension signal, the decoding of the extension signal may be skipped based on synchronization information indicating a position of the extension signal. For example, a sync word having a predetermined bit may be inserted at a point where the extension signal ends. The decoding apparatus continues to search the bit field of the residual signal until the sync word of the extension signal is found. Once the sync word is found, the decoding apparatus stops the search process and then continues decoding. In particular, decoding of the extension signal may be skipped until the sync word of the extension signal is found. As another example of the method of decoding according to the selection, in the case of performing decoding of the extension signal, the decoding may be performed after parsing the extension signal. When decoding of the extension signal is performed, the sync word of the extension signal may be read but may not be available.

Fig. 3 and 4 are diagrams for explaining fixed bit allocation with respect to length information of an extension signal according to an embodiment of the present invention.

The length information of the extension signal may be defined by a bit or byte unit. If the length information is determined by the byte unit, it indicates that the extension signal is allocated bytes. Fig. 3 illustrates a method of defining length information on an extension signal in the simplest manner. And, fig. 4 schematically illustrates the method shown in fig. 3. A syntax element for indicating length information of the extension signal is defined, and predetermined bits are allocated to the syntax element. For example, "bsresidualsignalllength" is defined as a syntax element, and 16 bits are allocated as fixed bits. However, this approach may consume a significant amount of bits. Therefore, the methods shown in fig. 5, 6, 7 and 8 are explained as follows.

Fig. 5 and 6 are diagrams for explaining variable allocation of bits of length information of an extension signal depending on length types according to one embodiment of the present invention.

Fig. 5 illustrates a method of defining one more syntax element to define how many bits are to be used for "bsresidualsignalllength" to further reduce bit consumption. And figure 6 schematically illustrates the method shown in figure 5. For example, "bsresidulalsignallingtype" is newly defined as a length type. If the value of "bsresidualsignalLength" is 0, 4 bits are allocated to "bsresidualsignalLength". If the value of "bsresidualsignalLength" is 1, 8 bits are allocated to "bsresidualsignalLength". If the value of "bsresidualsignalLength" is 2, 12 bits are allocated to "bsresidualsignalLength". If the value of "bsresidualsignalLength" is 3, 16 bits are allocated to "bsresidualsignalLength". In this case, the allocated bits are exemplary. Therefore, bits different from the above-defined bits may be allocated. In order to reduce the bit consumption more than the above methods, the methods shown in fig. 7 and 8 are provided.

Fig. 7 and 8 are diagrams for explaining adaptively allocating bits of length information of an extension signal depending on a real length of the extension signal according to an embodiment of the present invention.

If the extension signal is input, a length information value of the extension signal may be read up to an initially determined value. If the length information value is equal to the predetermined value, it may be additionally read up to a further determined value. If the length information value is equal to another predetermined value, it may additionally be read up to another further determined value. In this case, if the length information value is not the other predetermined value, the corresponding value is output as the length information value as it is. Accordingly, length information of the extension signal is adaptively read according to the real data length, whereby bit consumption can be minimized. The examples shown in fig. 7 and 8 are explained below.

In fig. 7, a residual signal is taken as an example of an extension signal. If a residual signal is input, a residual signal length of 4 bits is read. If the length information value (bsResidualsignalLength) is 2⁴-1(═ 15), then 8 more bits are read as the value of bsresidualsignalengthl. If the length information value (bsResidualsignalLength) is (2)⁴-1)+(2⁸-1) (-15 +255), then 12 more bits are read as the value of bsresidualsignalength 2. In the same manner, if the length information value (bsResidualSignalLength) is (2)⁴-1)+(2⁸-1)+(2¹²-1) (-15 +255+4095), then 16 more bits are read as the value of bsresidualsignalelength 3.

Fig. 8 schematically shows another example of adaptive bit allocation of length information of an extension signal.

In fig. 8, if an extension signal is input, 4 bits are preferentially read. If the value obtained by reading the length information is less than 4 bits, the corresponding value becomes length information. However, if the value resulting from reading the length information is greater than 4 bits, 8 bits are additionally read. If the additionally read value is less than 8 bits, the total read length information value corresponds to 12(═ 4+ 8). However, if the additionally read value is greater than 8 bits, 16 bits are additionally read. This will be described in detailA detailed explanation follows. First, if length information is input, 4 bits are read. The range of the real length information value is 0-14. If the length information value becomes 2⁴-1(═ 15), the extension signal is read again. In this case, the extension signal may additionally be read up to 28-2(═ 254). However, if the length information value corresponds to less than 2⁴A value of-1 (═ 15), the values read are 0 to (2)⁴-2) (═ 14) is output as is. Once the length information value becomes (2)⁴-1)+(2⁸-1), the extension signal is read again in addition. In this case, the extension signal may be read additionally up to (2)¹⁶-1). However, if the length information value corresponds to less than 2¹⁶A value of-1, then the read values 0 to (2)¹⁶-1) (-65535) is output as is. In this case, as described above, the allocated bits are an example for explanation. Other bits than those defined above may also be allocated.

Meanwhile, the length information of the extension signal may be length information of a header of the extension signal or length information of frame data of the extension signal. Therefore, the length information of the extension signal may be located in the header region and/or the frame data region. The bit stream structure used for this will be explained with reference to fig. 9 to 12.

Fig. 9 and 10 illustrate an embodiment of the present invention, in which a bitstream structure configuring an audio signal with a downmix signal, an ancillary signal, and an extension signal is illustrated.

The audio signal includes a downmix signal and an ancillary signal. As an example of the auxiliary signal, a spatial information signal may be mentioned. The downmix signal and the ancillary signal are each transmitted in units of a frame. The ancillary signal may include header information and data information or may include only data information. Accordingly, in a file/general stream structure configuring one audio signal, header information precedes and data information follows. For example, in the case of configuring a file/general stream structure of an audio signal with a downmix signal and an ancillary signal, a downmix signal header and an ancillary signal header may exist in the front as header information. And, the downmix signal data and the ancillary signal data may be configured with one frame as data information after the front. In this case, the extension signal may be located by defining an extension area of the auxiliary data. The extension signal may be included in the auxiliary signal or may be used as a separate signal. Fig. 9 shows a case where the extension signal is used as an independent signal, and fig. 10 shows a case where the extension signal is located in an extension area of the ancillary signal. Therefore, in the case where an extension signal exists, in a file/general stream structure, a header of the extension signal may exist in a front part as header information, as well as a downmix header and a spatial information header. After the front, as data information, extension signal data, and downmix signal data and ancillary signal data for configuring one frame may be further included. Since the extension signal can be selectively decoded, it may be located at the last part of the frame or may be continuously present after the ancillary signal. The length information explained in fig. 3 to 8 may be present in a header area of the extension signal and/or in a data area of the extension signal. In this case, the length information present in the header area (extension signal header) indicates the length information of the extension signal header, and the length information present in the data area (extension signal data) indicates the length information of the extension signal data. Accordingly, the length information present in each region is read from the bitstream, and the decoding apparatus can skip the decoding of the extension signal based on the length information.

Fig. 11 is a diagram of a bitstream structure configuring an independent audio signal with a downmix signal or an ancillary signal according to an embodiment of the present invention.

The audio signal includes a downmix signal and an ancillary signal. A spatial information signal may be used as an example of the auxiliary signal. The downmix signal and the ancillary signal may be transmitted as independent signals, respectively. In this case, the downmix signal has a structure of: downmix signal header (downmix signal header) as header information) Downmix signal data (r), g, and g … …)) located at the front as data information) After the head of the downmix signal. Also, the auxiliary signal has the structure: auxiliary signal header (auxiliary signal header) as header information) Auxiliary signal data (r) and (r) … …) located at the front as data information) After the auxiliary signal header. Since the extension signal may be included in the auxiliary signal, a structure in which the extension signal follows the auxiliary signal may be provided. Therefore, the signal header is extendedAt the head of the auxiliary signalThe extension signal data (r) then follows the auxiliary signal data (r). Likewise, the extension signal data (c) follows the ancillary signal data (c). In this case, the length information of the extension signal may be included in the extension signal headerExtended signal data (r) and/or extended signal data (r) … … andamong each of them.

Meanwhile, unlike the file/general stream structure, in the case where previously transmitted header information cannot be used because an audio signal is decoded from a random point in time rather than from the beginning, another header information included in the audio signal may be used for decoding. In the case of using an audio signal for broadcasting or the like or losing header information during transmission of the audio signal, decoding should start from any time when the signal is received. Therefore, coding efficiency can be improved by defining identification information indicating whether a header exists. The stream structure for broadcasting will be explained below with reference to fig. 12.

Fig. 12 is a diagram of a broadcast stream structure configuring an audio signal with a downmix signal and an ancillary signal according to an embodiment of the present invention.

In the case of a broadcast stream, if header information exists only once in the front of an audio signal, decoding cannot be performed due to the lack of header information in the case of receiving the audio signal at an arbitrary point in time. Therefore, the header information may be inserted into the audio signal at least once. In this case, the header information may be introduced according to a predetermined format (e.g., time interval, spatial interval, etc.). Specifically, the header information may be inserted into each frame, periodically inserted into each frame at a fixed interval, or non-periodically inserted into each frame at a random interval. Alternatively, the header information may be inserted once according to a fixed time interval (e.g., 2 seconds).

A broadcast stream structure configuring one audio signal has a structure in which: the header information is inserted at least once between the data information. For example, in the case of configuring a broadcast streaming structure of one audio signal, a downmix signal is in front and an ancillary signal is behind the downmix signal. The synchronization information for distinguishing the downmix signal and the ancillary signal may be located at a front portion of the ancillary signal. And, identification information indicating whether header information on the ancillary signal exists may be located (locate). For example, if the header identification information is 0, the next read frame has only a data frame without header information. If the header identification information is 1, the next read frame has header information and a data frame. This may be applicable to the auxiliary signal or the extension signal. These header information may be the same as the header information that has been initially transmitted or may be variable. In case that the header information is variable, new header information is decoded, and data information transmitted after the new header information is then decoded according to the decoded new header information. In the case where the header identification information is 0, the transmitted frame has only a data frame without header information. In this case, in order to process the data frame, previously transmitted header information may be used. For example, if the header identification information is 1 in fig. 12, there may be an auxiliary signal header (r) and an extended signal header (r). However, if the next input frame does not have header information because the header identification information is set to 0, the extension signal data (c) can be processed using the information of the extension signal header (r) previously transmitted.

Fig. 13 is a flowchart of a method of processing an extension signal based on length information of the extension signal according to identification information indicating whether a header is included in 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 generating an audio signal and an extension signal included in the ancillary signal are extracted from a received bitstream (1301). The extension signal may be included in the auxiliary signal. Identification information indicating whether the header is included in the auxiliary signal is extracted (1303). For example, 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 the 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 the extension signal header is included in the extension signal. If the header identification information is 0, it indicates that the extension signal header is not included in the extension signal. It is determined whether a header is included in the ancillary signal based on the header identification information (1305). If the header is included in the ancillary signal, length information is extracted from the header (1307). And, decoding of the extension signal may be skipped based on the length information (1309). In this case, the header plays a role in making each auxiliary signal and/or each extension signal interpreted. For example, the header information may include information on the residual signal, information on the length of the residual signal, synchronization information indicating the position of the residual signal, a sampling frequency, a frame length, the number of parameter bands, tree configuration information, quantization mode information, ICC (inter-channel level difference), parameter smoothing information, gain information for clip-prevention (clip-prediction), QMF (quadrature mirror filter) associated with the information, and the like. Also, if the header is not included in the ancillary signal according to the header identification information, decoding of the extension signal may be skipped based on previously extracted length information on the header (1311).

Fig. 14 is a flowchart of a method of selectively decoding an extension signal based on length information of the extension signal according to an embodiment of the present invention.

The profile (profile) means that the technical elements of the algorithm in the decoding process are standardized. In particular, a profile is a set of technical elements necessary to decode a bitstream and corresponds to a class of sub-standards. The level (level) defines the range of technical elements specified in the profile that is supported. In particular, the levels play a role in defining the capabilities of the decoding apparatus and the complexity of the bitstream. In the present invention, the level information may include a profile and a definition of a level. The decoding method of the extension signal may be changed according to the level information of the bitstream and the level information of the decoding apparatus. For example, even if an extension signal exists in the transmitted audio signal, decoding of the extension signal may or may not be performed as a result of the decision level information. Further, although decoding is performed, only a predetermined low frequency part may be used. In addition, as much as length information of the extension signal may be skipped in the decoding of the extension signal, so that the decoding of the extension signal is not performed. Alternatively, although the extension signal is completely read, decoding cannot be performed. Further, a part of the extension signal is read, only the read part is decoded, and the rest of the extension signal cannot be decoded. Alternatively, the extension signal may be completely read, and a portion of the extension signal may be decoded without decoding the remaining extension signal.

For example, referring to fig. 14, an ancillary signal for generating an audio signal and an extension signal included in the ancillary signal are extracted from a received bitstream (1410). And, information on the extension signal can be extracted. In this case, the information on the extension signal may include extension data type information indicating a data type of the extension signal. For example, the extension data type information includes residual coding data, artistic downmix residual coding data, artistic tree extension data, and the like. Therefore, the type of the extension signal is determined, and length information of the extension signal can be read from the extension area of the audio signal (1420). Subsequently, the level of the bit stream is decided. This can be determined with reference to the following information. For example, if the type of the extension signal is residual coding data, the level information of the bitstream may include the number of output channels, a sampling rate, a bandwidth of the residual signal, and the like. Therefore, if the level information explained above is input, they are compared with the level information on the decoding apparatus to determine whether the extension signal is to be decoded (1430). In this case, the level of the decoding apparatus may be set in advance. Generally, the level of the decoding apparatus should be equal to or greater than the audio signal. This is because the decoding apparatus should be able to decode the transmitted audio signal completely. However, in the case where the decoding apparatus is restricted (for example, in the case where the level of the decoding apparatus is smaller than the audio signal), decoding is sometimes possible. However, the corresponding quality may deteriorate. For example, if the level of the decoding apparatus is lower than the audio signal, the decoding apparatus cannot decode the audio signal. However, in some cases, the audio signal may be decoded based on the level of the decoding device.

In case it is determined that the level of the decoding apparatus is lower than the level of the bitstream, the decoding of the extension signal may be skipped 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 the level of the bitstream, the decoding of the extension signal may be performed (1460). However, although the decoding of the extension signal is performed, the decoding may be performed only on a predetermined low frequency part of the extension signal (1450). For example, there are cases where: since the decoding apparatus is a low power decoder, efficiency is degraded if the extension signal is completely decoded, or since the decoding apparatus cannot decode the entire extension information, a predetermined low frequency portion of the extension signal can be used. And, this is possible only when the level of the bitstream or the level of the decoding apparatus satisfies a specified condition.

Industrial applicability

Accordingly, various environments for encoding and decoding signals may be ubiquitous, and various methods of processing signals according to various environmental conditions may exist. In the present invention, a method of processing an audio signal is taken as an example, which does not limit the scope of the present invention. In this case, the signal includes an audio signal and/or a video signal. While the invention has been described and illustrated with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention. Accordingly, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (6)

1. A method of processing an audio signal, comprising the steps of:

extracting an audio signal including a downmix signal generated from downmixing a multi-channel audio signal and a bitstream including an ancillary signal and an extension signal, the extension signal being included in an extension area within the ancillary signal, and the ancillary signal and the extension signal being used to generate the multi-channel audio signal;

reading length information of the extension signal from the extension area, the reading the length information including:

reading 4 bits as bsresidualsignalllength;

if the value of bsresidualsignalLength is 15, then 8 bits are read as bsresidualsignalLength 1;

skipping decoding of the extension signal based on the length information; and

generating the multi-channel audio signal by applying the ancillary signal to the downmix signal.

2. The method of claim 1, wherein the extension signal comprises a residual signal.

3. The method of claim 1, wherein fixed bits are allocated to length information of the extension signal.

4. The method of claim 1, wherein bits are variably allocated to the length information of the extension signal according to the length type information of the extension signal.

5. The method of claim 1, wherein bits are adaptively allocated to the length information of the extension signal according to the length of the extension signal.

6. An apparatus for processing an audio signal, comprising:

a demultiplexing unit extracting a bitstream including a downmix signal generated from downmixing a multi-channel audio signal, an ancillary signal and an extension signal, the extension signal being included in an extension area within the ancillary signal, and the ancillary signal and the extension signal being used to generate the multi-channel audio signal;

an extended signal length reading unit that reads length information of the extended signal by reading 4 bits as bsResidualSignalLength, and if the value of bsResidualSignalLength is 15, 8 bits as bsResidualSignalLength 1;

a selective decoding unit skipping decoding of the extension signal based on the length information; and

an upmixing unit generating the multi-channel audio signal by applying the ancillary signal to the downmix signal.