KR20060109299A - Method for encoding-decoding subband spatial cues of multi-channel audio signal - Google Patents

Abstract

A method of encoding and decoding spatial information for each sub-band with respect to a multi-channel audio signal is provided to form spatial information of the audio signal from differential values by channels, sub-bands and frames to improve the encoding, transmission and decoding efficiency of the multi-channel audio signal. A multi-channel audio signal is down-mixed(310), and first spatial information is extracted from the multi-channel audio signal by sub-bands using a reference channel(311). Second spatial information is generated with differential values by channels, differential values by sub-bands and differential values by frames of the first spatial information(313). A core CODEC bit stream is generated using the down-mixed audio signal(312), and a spatial information bit stream is generated using the second spatial information(314).

Description

Code-decoding method of subband spatial information for multi-channel audio signal {METHOD FOR ENCODING-DECODING SUBBAND SPATIAL CUES OF MULTI-CHANNEL AUDIO SIGNAL}

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating a method for a human to recognize spatial information about an audio signal in the present invention.

2 is a diagram of a method of coding a multichannel audio signal using a spatial encoder and decoder in the present invention.

3A is a detailed diagram of a spatial encoder according to the first embodiment of the present invention.

3B is a flowchart of an encoding process according to the first embodiment of the present invention.

4A is a detailed diagram of a spatial encoder according to a second embodiment of the present invention.

4B is a flowchart of an encoding process according to the second embodiment of the present invention.

Fig. 5A is a detailed diagram of a spatial decoder according to the first embodiment of the present invention.

5B is a flowchart of a decoding process according to the first embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

101.Remote sound source 102.Direct sound wave

104. Reflected Sound Wave 201. Multichannel Audio Signal

202. Downmix unit 203. Special parameter extraction unit

204 Spatial Encoder 205 Artistic Downmix Audio Signal

206. Mono or stereo audio signal 207. Special parameters

208.Space Decoder 302.Filter Bank

303. Reference channel selection and spatial information calculation unit

304. Comparative value generation unit 305. Grouping generation unit

306. Minimum Bit Rate Determination Unit 410. Comparative Selection Unit

502. Spatial information detector 502. Differential spatial information detector

503. Grouping spatial information detection unit 506. Spatial information calculation unit

The present invention relates to an encoding-decoding method for spatial information of a multi-channel audio signal. More particularly, the present invention relates to generating sub-band spatial information as differential values or grouping in multi-channel audio coding. The present invention relates to a method for effectively configuring a bitstream.

Recently, various coding techniques and methods for digital audio signals have been developed, and related products have been produced. In addition, coding methods for multi-channel audio signals have been developed using a psychoacoustic model, and standardization thereof has been performed.

The psychoacoustic model is unnecessary in the coding process by using a method in which a human recognizes a sound, for example, a small sound that comes after a loud sound and can only hear a sound corresponding to a frequency of 20 Hz to 20000 Hz. By removing the audio signal for the part, the amount of data required can be effectively reduced.

Currently, audio standard technologies such as MPEG-1 Audio (MEPG-1 Layer III), MPEG-4 Advanced Audio Coding (AAC), and MPEG-4 High-Efficiency AAC (HE-AAC) have been developed and commercialized. In addition, a method of coding a multichannel audio signal using spatial information has been developed. The multi-channel audio signal coding method uses a compressed audio signal (e.g., stereo or mono audio signal) and a low bit-rate side information (e.g., spatial information) channel. Therefore, the transmission efficiency of the multichannel audio signal is greatly improved.

However, in constructing the bitstream of the multichannel audio signal, conventionally, the spatial information has been quantized by subband for encoding and decoding. Therefore, the conventional method does not consider the characteristics of the spatial information of the audio signal at all and requires a large bit rate for coding the spatial information, resulting in poor construction efficiency of the bitstream generated using the spatial information of the audio signal. There was a downside.

Accordingly, the present invention proposed to solve the above problems, in coding a multi-channel audio signal, in consideration of the characteristics of the spatial information of the audio signal, the spatial information by channel, subband, frame-by-frame differential value Encoding or decoding to improve the encoding, transmission and decoding efficiency of multichannel audio signals by constructing a spatial information bitstream or by generating a group by channel, subband, or frame. The purpose is to provide a method.

In order to achieve the above object, the present invention comprises the steps of downmixing the multichannel audio signal and extracting first spatial information for each subband using a reference channel from the multichannel audio signal; Generating second spatial information using a differential value for each channel, a differential value for each subband, or a differential value for each frame of the first spatial information; Forming a core codec bitstream by using the downmixed audio signal and forming a spatial information bitstream by using the second spatial information; providing a method of encoding a multichannel audio signal do. The second spatial information may be generated by combining two or more of the first spatial information by channel-specific, subband-differential, or frame-by-frame differential. The spatial information may include a Channel Level Difference (ICLD), a Channel Time Difference (ICTD), or an Inter-Channel Coherence (ICC), and the differential for each channel includes a channel having the largest energy, a channel having an intermediate energy, or One channel of the lowest energy channel may be used as the reference channel.

In addition, to achieve the above object, the present invention comprises the steps of downmixing the multichannel audio signal, and extracting first spatial information for each subband using a reference channel from the multichannel audio signal; Generating second spatial information by grouping the first spatial information by channel, subband, or frame; And forming a core codec bitstream using the downmixed audio signal, and forming a spatial information bitstream using the spatial information generated as the second comparison value. Provides an encoding method.

In addition, to achieve the above object, the present invention comprises the steps of (a) downmixing the multichannel audio signal, and extracting first spatial information for each subband using a reference channel from the multichannel audio signal; (b) generating second spatial information based on a channel-specific differential value, a subband-specific differential value, or a frame-specific differential value of the first spatial information; (c) generating second spatial information by grouping the first spatial information by channel, subband, or frame; (d) generating a spatial information bitstream by selecting one having a smaller bit rate among the second spatial information generated in step (b) and the second spatial information generated in step (c); (e) generating a spatial information bitstream using the first spatial information; (f) selecting one of the spatial information bitstream generated in step (d) and the spatial information bitstream generated in step (e). to provide. Here, when configuring the entire bitstream using the spatial information bitstream generated by the selected method, whether the spatial information bitstream is formed in the (d) step in the entire bitstream, the spatial information bit in the step (e) It may include identification information for distinguishing whether a stream is formed.

In addition, to achieve the above object, the present invention comprises the steps of: (a) receiving a core codec bitstream and spatial information bitstream for the downmixed audio signal; (b) Second spatial information and channel index information generated as a differential value for each channel, a differential value for each subband, or a differential value for each frame of the first spatial information generated for each subband using a reference channel from the spatial information bitstream. Reading a; (c) decoding the core codec bitstream and decoding the spatial information bitstream using the spatial information and the channel index information read in the step (b). It provides a method for decoding. The step (b) may further include reading the spatial information and the channel index information generated by grouping the second spatial information for each channel, subband, or frame. In addition, the downmix audio signal obtained by decoding the core codec bitstream may be converted into a multichannel audio signal using the spatial information obtained from the decoded spatial information bitstream.

In addition, in order to achieve the above object, the present invention comprises the steps of (a) receiving a core codec bitstream and spatial information bitstream for the downmixed audio signal; (b) reading spatial information and channel index information generated by grouping each channel, subband or frame from the spatial information bitstream; (c) decoding the core codec bitstream and decoding the spatial information bitstream using the spatial information and the channel index information read in the step (b). It provides a method for decoding.

In addition, in order to achieve the above object, the present invention is generated so that the audio signal includes a core codec bitstream and a spatial information bitstream, the spatial information bitstream is a subband using a reference channel from a multichannel audio signal And generating second spatial information by extracting first spatial information for each channel, and expressing second spatial information by a differential value for each channel, a differential value for each subband, or a differential value for each frame of the extracted first spatial information. Provide a method.

In addition, in order to achieve the above object, the present invention is generated so that an audio signal includes a core codec bitstream and a spatial information bitstream, the spatial information bitstream for each subband using a reference channel from a multi-channel audio signal And extracting first spatial information and grouping the extracted first spatial information by channel, subband, or frame to represent second spatial information.

In addition, in order to achieve the above object, the present invention extracts the first spatial information using a reference channel for each subband from the multi-channel audio signal, the differential value for each channel, the differential value for each subband of the first spatial information Alternatively, when the second spatial information is generated using differential values for each frame and the second spatial information is generated by grouping the first spatial information for each channel, for each subband, or for each frame, a smaller bit rate is used. And a method of generating a spatial information bitstream and a method of generating a spatial information bitstream using the first spatial information, and then selecting one method. do.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

1 shows a method for a human to recognize spatial information about an audio signal in the present invention. The coding method for a multichannel audio signal is based on the fact that a human perceives the audio signal as a three-dimensional space. I use it. Such parameters, called "spatial parameters" for indicating spatial information of a multichannel audio signal, include ICLD (Inter Channel level differences), ICC (Inter Channel Coherences), ICTD (Inter Channel Time Difference), and the like. The ICLD means an energy difference between two channels, the ICC means a correlation between two channels, and the ICTD means a time difference between two channels.

How a human perceives an audio signal spatially and how the concept of the spatial parameter is generated is shown in FIG. 1. Direct sound wave 103 from the remote source 105 arrives at the human left ear 107, and another direct sound wave 102 is diffracted around the head to the right ear 106. Will be reached. The two sound waves 102 and 103 show a difference in arrival time and energy level, and this difference generates the CLD, CPC and CTD parameters.

Also, if the reflected sound waves 104 and 105 reach both ears, or if the sound source 105 is dispersed, sound waves that do not correlate with each other will reach both ears, which will generate the ICC parameter. It is known that the spatial parameters generated on the principle as described above enable a strong number of bits in transmitting a multichannel audio signal as a mono or stereo signal and then outputting the multichannel audio signal back to the multichannel. The present invention proposes a method for generating a bitstream by generating the spatial parameter as a comparison value for each channel, for each subband, or for each frame, or for grouping.

2 illustrates the principle of coding a multichannel audio signal using a spatial encoder and decoder in the present invention. As shown, the spatial encoder 204 first receives a multichannel audio signal 201. Where N is the number of input channels. The multichannel audio signal 201 is downmixed by the down-mix unit 202 to be a downmix signal 206.

In addition, the spatial information of the multichannel audio signal, that is, the spatial parameter, is extracted from the multichannel audio signal 201 by the spatial parameter extractor 203. In this case, spatial information refers to downmixing a multi-channel (eg, Left, Right, Center, Left surround, Right surround, etc.) audio signal, transmitting the downmix signal 206, and transmitting the transmitted down signal. Information about the audio signal channel used when upmixing a mix signal back to multichannel. Alternatively, the downmix signal 206 may be generated using an externally provided downmix signal, for example, an artistic down-mix signal 205.

The downmix signal 206 is encoded using a core codec coding method and then compressed and transmitted. The downmix signal 206 is also transmitted with the spatial information, that is, the spatial parameter 207. The core codec refers to a codec for coding or encoding an audio signal other than the spatial information, that is, the spatial parameter 207. The core codec may include MP3, AC-3, DTS, or AAC. If the function is performed, it may include a codec to be developed in the future as well as a codec previously developed. If the user's system can only output the downmix signal 206, the compressed downmixed signal 206 may be decoded and output 209 directly. If the system is capable of outputting a multichannel audio signal, the compressed and transmitted audio signal is decoded and then received spatial information, i.e., spatial parameter 207, of the multichannel audio signal transmitted together by the spatial decoder 208. The multichannel audio signal 210 may be converted into a multichannel audio signal 210 and output.

Instead of transmitting the multichannel audio signal directly, the method of downmixing and transmitting the downmix signal 206 as described above, and transmitting the spatial information of the multichannel audio signal, that is, the spatial parameter 207 together, is compressed and It is very advantageous in terms of transmission efficiency. In the present invention, in transmitting the spatial information of the multi-channel audio signal, that is, the spatial parameter 207 together, the spatial parameter 207 extracted for each subband is adaptively quantized to construct a bit stream more efficiently. Compression and transmission efficiency can be improved.

3A shows in detail the spatial encoder according to the first embodiment of the present invention. In the drawing, a thick arrow means that a plurality of signals go. As shown, the multi-channel audio signal 301 passes through the filter bank 302 and is divided into subbands. The filter bank 302 divides an audio signal across all frequency bands into subbands, and a sub-band filter bank or a QMF filter bank may be used as the filter bank 302. have. The spatial information is extracted for each subband of the audio signal passing through the filter bank, and the reference channel selection and spatial information calculator 303 may variably set a reference channel using the spatial information extracted for each subband. have. The reference channel selector and the spatial information calculator 303 may use the variably set reference channel or use a fixed reference channel. The spatial information may include ICLD, ICTD, or ICC. The reference channel may be set for each subband or the same for all subbands. Next, the reference channel selection and spatial information calculator 303 generates first spatial information for each subband using the reference channel.

Next, the comparison value generator 304 may generate second spatial information using the channel-specific differential value, the subband-specific differential value, or the frame-specific differential value of the first spatial information. The differential for each channel may be generated based on a channel having the largest energy, based on a channel having an intermediate energy, or generated based on a channel having the smallest energy. The second spatial information is obtained by applying subband-differentials to the channel-specific differentials again, or is obtained by applying frame-differentials to the channel-specific differentials again, or by sub-band differential and subchannels again to the channel-differential values. Can be obtained by applying the differential per frame. The grouping generator 305 may generate the second spatial information by grouping the first spatial information by channel, subband, or frame. In addition, the grouping generator 305 may regenerate the second spatial information by grouping the second spatial information generated as the differential value by the comparison value generator 304 for each channel, subband, or frame. have.

Next, the minimum bit rate decision element 306 determines second spatial information generated by the differential value, the second spatial information generated by the grouping, and the minimum bit rate of the first spatial information. Select spatial information to have. The selected spatial information is encoded by the encoding unit 307 to form a spatial information bitstream 308. Entropy encoding, for example Hoffman encoding, may be applied to the encoding unit 307. The spatial information bitstream 308 forms an entire bitstream together with a core codec bitstream generated by using a downmix audio signal obtained by downmixing a multichannel audio signal. The spatial information bitstream is a spatial information extracted from a multi-channel audio signal, that is, a bitstream for a spatial parameter, and may be configured with a configuration bitstream and a spatial data bitstream for the spatial information. The core codec bitstream refers to a bitstream formed by an audio signal except for the spatial information.

For example, in the case of ICLD among the spatial information, first, energy of each channel is calculated for each subband from an audio signal divided for each subband through the filter bank 302. Next, the reference channel selection and spatial information calculator 303 may select the variable reference channel for each subband according to a preset reference using the energy for each channel. The reference channel selection and spatial information calculator 303 may use the variable reference channel or use a fixed reference channel. In addition, the reference channel selection and spatial information calculator 303 may generate an inter-channel energy difference (ICLD) using the reference channel. Next, the comparison value generator 304 generates the channel-to-band energy information and the channel index information expressed as described above as channel, band, or frame differential values. In addition, the grouping generation unit 305 may generate the channel-to-channel energy difference (ICLD) generated by using the reference channel by grouping by channel, subband, or frame. Next, the minimum bit rate determination unit 306 may select the one having the minimum bit rate by comparing the ICLD generated by the differential value, the ICLD generated by the grouping, and the ICLD generated by using the reference channel. The selected inter-channel energy difference (ICLD) information is combined with the channel index information or entropy coding such as Huffman Coding to form a spatial information bitstream, and a core codec bitstream composed of a downmix audio signal. In addition, the entire bitstream can be configured.

For example, in the case of ICTD or ICC among the spatial information, first, the ICTD or ICC is calculated for each subband from the audio signal divided for each subband through the filter bank 302. Subsequently, the reference channel selection and spatial information calculation unit 303 may select a variable reference channel for each subband based on a preset reference using the ICTD or ICC. The reference channel selection and spatial information calculator 303 may use the variable reference channel or use a fixed reference channel. In addition, the reference channel selection and spatial information calculator 303 may recalculate ICTD or ICC using the reference channel. Next, the comparison value generator 304 generates the ICTD or ICC and the channel index information expressed as described above as channel, subband, or frame differential values. In addition, the grouping generator 305 may generate an ICTD or ICC grouped by the channel, the subband, or the frame by using the reference channel. Next, the minimum bit rate determining unit 306 compares the ICTD or ICC generated by the differential value, the ICTD or ICC generated by the grouping, and the ICTD or ICC generated by using the reference channel to have a minimum bit rate. You can choose. The ICTD or ICC may configure the spatial information bitstream by entropy coding such as Huffman coding or channel index information, and the entire bitstream together with the core codec bitstream composed of downmixed signals. .

3B is a flowchart of an encoding process according to the first embodiment of the present invention. To more efficiently represent spatial information, first downmix 310 an audio signal from a multichannel audio signal 309, and then generate 312 a core codec bitstream using the downmixed audio signal. The downmixed audio signal may comprise a mono or stereo signal. Subsequently, first spatial information, for example, spatial parameters, are extracted 311 for each subband using a reference channel from the multichannel audio signal 309, and for each channel of the first spatial information extracted for each subband. In operation 313, second spatial information is generated using differential values per subband or per frame. In addition, the spatial information may be generated 313 by grouping the first spatial information extracted for each subband by channel, subband, or frame. Next, a spatial information bitstream is generated using the second spatial information (314), and the entire bitstream including the core codec bitstream and the spatial information bitstream is transmitted (315).

4A shows a detailed diagram of a spatial encoder according to a second embodiment of the present invention. As shown, the multichannel audio signal 401 passes through the filter bank 402 and is divided into subbands. The spatial information is extracted for each subband of the audio signal passing through the filter bank, and the reference channel selection and spatial information calculator 403 may set a variable reference channel for each subband using the spatial information. The reference channel selection and spatial information calculator 403 may use a variable reference channel or a fixed reference channel. The reference channel selection and spatial information calculator 403 generates first spatial information using the variable reference channel or the fixed reference channel. Next, the comparison value generator 404 may generate second spatial information using differential values of channels, subbands, or frames of the first spatial information. In addition, the comparison value generator 404 may generate the second spatial information by grouping the first spatial information by channel, subband, or frame.

Next, the minimum bit rate determining unit 406 selects a small bit rate from the second spatial information generated as the differential value and the second spatial information generated through the grouping. The selected second spatial information is encoded by the encoding unit 408 to generate a spatial information bitstream. In addition, the first spatial information generated for each subband may be encoded by the encoder 409 to generate a spatial information bitstream. The encoding unit 408 and the encoding unit 409 may be the same or different. Next, the comparison selecting unit 410 compares the spatial information bitstream generated by encoding the second spatial information with the spatial information bitstream generated by encoding the first spatial information, and then selects one. In this case, the comparison selector 410 may select a space information bitstream having a lower bit rate.

4B is a flowchart of an encoding process according to a second embodiment of the present invention. To more efficiently represent spatial information, first downmix 413 the audio signal from the multi-channel audio signal 412, and generate 415 a core codec bitstream using the downmixed audio signal. The downmixed audio signal may comprise a mono or stereo signal. Next, the first spatial information for each subband is extracted from the multichannel audio signal 412 for each subband using a reference channel (414), and a spatial information bitstream is generated using the first spatial information (416). )do. In addition, second spatial information is generated using channel, subband, or frame differential values of the first spatial information, and a spatial information bitstream is generated using the second spatial information (417). Next, the spatial information bitstream generated using the first spatial information is compared with the spatial information bitstream generated using the second spatial information (418). If the spatial information bitstream generated using the first spatial information has a lower bit rate, select 419 the spatial information bitstream generated using the first spatial information, and use the second spatial information. If the generated spatial information bitstream has a lower bit rate, the generated spatial information bitstream is selected 420 using the second spatial information. Then, the entire bitstream including the spatial information bitstream configured in the selected manner and the core codec bitstream is transmitted 421.

5a shows a spatial decoder according to a first embodiment of the present invention in detail. As shown, the spatial decoder receives an entire bitstream 501 that includes a core codec bitstream and a spatial information bitstream. The entire received bitstream may be sent to a plurality of spatial information detectors. For example, the plurality of spatial information detectors may include a spatial information detector 502, a differential spatial information detector 503, and a grouped spatial information detector 504. The plurality of spatial information detection units read flag information indicating how spatial information is generated in the encoder. If spatial information is generated for each subband, the spatial information reading unit 502 reads the spatial information. If spatial information is generated as a differential value of the spatial information for each subband, the spatial information is read by the differential spatial information detector 503. If spatial information is generated by grouping the spatial information generated by the subband spatial information or the difference value, the spatial information is read by the grouping spatial information detector 504.

Then, the spatial information bitstream is decoded by the decoding unit 505 using the read spatial information, and the spatial information calculating unit 506 uses the spatial index information and the spatial index information obtained from the decoding. Calculate the actual physical quantity corresponding to. The channel index information may include information about a reference channel. Then, using the actual physical quantity corresponding to the spatial information, the multi-channel generator 507 may output the downmix audio signal 509 obtained by decoding the core codec bitstream to the multi-channel audio signal 507. Can be converted to If the system only supports mono or stereo audio signals, the downmix audio signal 509 can be output directly.

5B shows a flowchart of a decoding process according to the first embodiment of the present invention. The spatial decoder first receives 509 the entire bitstream including the core codec bitstream and the spatial information bitstream. The core codec bitstream may then be decoded 510 and extract 512 a downmixed audio signal from the decoded core codec bitstream. The downmixed audio signal may comprise a mono or stereo audio signal. In addition, a method in which spatial information is generated in the encoder from the spatial information bitstream, for example, spatial information for each subband, spatial information generated as differential values of spatial information for each subband, or spatial information for each subband are grouped. The spatial information generated by the value is read (511). The spatial information bitstream is decoded using the read spatial information (513), and the physical quantity corresponding to the spatial information is calculated (514) using the channel index information and the spatial information obtained by decoding. The downmix signal is then converted into a multichannel audio signal using the physical quantity corresponding to the calculated spatial information (515).

Although the present invention has been described in detail with reference to some embodiments, the above embodiments are presented for the purpose of understanding the present invention, and the scope of the present invention is not limited to the above embodiments. Those skilled in the art will understand that various modifications are possible without departing from the scope of the technical idea of the present invention, and the scope of the present invention should be interpreted by the appended claims.

As described above, in coding the multi-channel audio signal according to the present invention, in order to efficiently represent spatial information, for each channel, subband, or frame of the first space information extracted for each subband. Generate second spatial information by differential value, or generate second spatial information by grouping the first spatial information by channel, subband, or frame and by using the second spatial information, a spatial information bitstream. By generating, the entire bitstream can be represented at a lower bit rate, thereby improving the encoding, transmission and decoding efficiency.

In addition, the case in which the spatial information bitstream is generated using the second spatial information and the case in which the spatial information bitstream is generated using the first spatial information may be expressed at a lower bit rate. The selection has the effect of improving the encoding, transmission and decoding efficiency.

Claims (22)

A method of encoding a multichannel audio signal, (a) downmixing the multichannel audio signal and extracting first spatial information for each subband using a reference channel from the multichannel audio signal; (b) generating second spatial information based on a channel-specific differential value, a subband-specific differential value, or a frame-specific differential value of the first spatial information; And (c) forming a core codec bitstream using the downmixed audio signal and forming a spatial information bitstream using the second spatial information. Encoding Method. The method of claim 1, The second spatial information is generated by combining two or more of the first spatial information per channel, subband differential, or frame differential. The method of claim 1, In step (b), And regenerating second spatial information by grouping the second spatial information by channel, subband, and frame. The method of claim 1, The spatial information includes an inter channel level difference (ICLD), an inter channel time difference (ICTD), or an inter-channel coherence (ICC). The method of claim 1, The differential for each channel is generated by using one of the channel with the highest energy, the channel with the highest energy, or the channel with the lowest energy as a reference channel. A method of encoding a multichannel audio signal, (a) downmixing the multichannel audio signal and extracting first spatial information for each subband using a reference channel from the multichannel audio signal; (b) generating second spatial information by grouping the first spatial information by channel, subband, or frame; And (c) forming a core codec bitstream using the downmixed audio signal and forming a spatial information bitstream using the second spatial information. Encoding Method. A method of encoding a multichannel audio signal, (a) downmixing the multichannel audio signal and extracting first spatial information for each subband using a reference channel from the multichannel audio signal; (b) generating second spatial information based on a channel-specific differential value, a subband-specific differential value, or a frame-specific differential value of the first spatial information; (c) generating second spatial information by grouping the first spatial information by channel, subband, or frame; (d) generating a spatial information bitstream by selecting one having a smaller bit rate among the second spatial information generated in step (b) and the second spatial information generated in step (c); (e) generating a spatial information bitstream using the first spatial information; And and (f) selecting one of the spatial information bitstream generated in the step (d) and the spatial information bitstream generated in the step (e). . The method of claim 7, wherein Step (f), When configuring the entire bitstream using the spatial information bitstream generated by the selected method, whether the spatial information bitstream is formed in the (d) step within the entire bitstream, or the spatial information bit in the step (e). Generating identification information that can distinguish whether a stream has been formed. In the method of decoding a multichannel audio signal, (a) receiving a core codec bitstream and a spatial information bitstream for the downmixed audio signal; (b) Second spatial information and channel index information generated as a differential value for each channel, a differential value for each subband, or a differential value for each frame of the first spatial information generated for each subband using a reference channel from the spatial information bitstream. Reading out; And (c) decoding the core codec bitstream, and decoding the spatial information bitstream using the spatial information and the channel index information read in the step (b). How to decode a signal. The method of claim 9, In step (b), And reading out the spatial information and the channel index information generated by grouping the second spatial information on a channel, subband, or frame basis. The method of claim 9, Step (c) is, And converting the downmix audio signal obtained by decoding the core codec bitstream into a multichannel audio signal using the spatial information obtained from the decoded spatial information bitstream. Decoding method. In the method of decoding a multichannel audio signal, (a) receiving a core codec bitstream and a spatial information bitstream for the downmixed audio signal; (b) reading second spatial information and channel index information generated by grouping first spatial information generated for each subband by a channel, subband or frame using a reference channel from the spatial information bitstream; ; And (c) decoding the core codec bitstream and decoding the spatial information bitstream using the read second spatial information and channel index information. How to. The method of claim 12, Step (c) is, And converting the downmix audio signal obtained by decoding the core codec bitstream into a multichannel audio signal by using the second spatial information obtained from the decoded spatial information bitstream. Method of decoding the signal. In the method of decoding a multichannel audio signal, (a) receiving a core codec bitstream and a spatial information bitstream for the downmixed audio signal; (b) reading identification information on a method of generating spatial information from the spatial information bitstream; And and (c) decoding the core codec bitstream, and decoding the spatial information bitstream according to the identification information read out in step (b). The method of claim 14, The identification information is generated when a spatial information bitstream is generated using first spatial information extracted for each subband using a reference channel, and the first spatial information is generated as a difference value for each channel, subband, or frame. The spatial information bitstream is generated by using the second spatial information to generate the spatial information bitstream, or by using the second spatial information generated by grouping the first spatial information by channel, subband, or frame. A method for decoding a multichannel audio signal, characterized in that the generated case can be distinguished. The method of claim 14, Step (c) is, Converting the downmix audio signal obtained by decoding the core codec bitstream using the spatial information obtained from the decoded spatial information bitstream into a multichannel audio signal. Decoding method. In generating an audio signal, The audio signal is generated to include a core codec bitstream and a spatial information bitstream, The spatial information bitstream extracts first spatial information for each subband using a reference channel from a multichannel audio signal, and extracts a differential value for each channel, a differential value for each subband, or a differential value for each frame from the extracted first spatial information. And generate second spatial information. The method of claim 17, The spatial information includes an inter channel level difference (ICLD), an inter channel time difference (ICTD), or an inter-channel coherence (ICC). The method of claim 17, The second spatial information is grouped by channel, subband, and frame to generate a spatial information bitstream. In generating an audio signal, The audio signal is generated to include a core codec bitstream and a spatial information bitstream, The spatial information bitstream extracts first spatial information for each subband using a reference channel from a multichannel audio signal, and groups the extracted first spatial information for each channel, for each subband, or for each frame. And to generate an audio signal. In generating an audio signal, Extracting first spatial information from a multi-channel audio signal by using a reference channel for each subband, and generating second spatial information using a differential value for each channel, a differential value for each subband, or a differential value for each frame. A method of generating a spatial information bitstream using a case in which the first spatial information is grouped by channel, subband, or frame to generate second spatial information, and having a smaller bit rate; And comparing a method of generating a spatial information bitstream using the first spatial information, and then selecting one method. The method of claim 21, When composing the entire bitstream using the spatial information bitstream formed by the selected method, whether the spatial information bitstream is formed using the first spatial information in the entire bitstream using the second spatial information. And identification information for discriminating whether or not a bitstream has been formed.

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