KR20070031212A - Method and Apparatus for encoding/decoding audio signal - Google Patents

Abstract

The present invention relates to a method and apparatus for encoding / decoding audio signals for efficient processing of audio signals.

The present invention provides a method of identifying a channel configuration identifier, extracting information on the number of bits of a first channel conversion module to which the number of bits corresponding to the number of input channels is allocated, if the channel configuration is not determined. It provides a method for decoding an audio signal comprising the step of generating a multi-channel using a channel conversion module.

Therefore, according to the present invention, it is possible to effectively reduce the amount of data by compressing a signal to a specific number, such as mono or stereo, and transmitting or storing the additional information represented by the spatial information together in multichannel audio coding. It is possible to effectively configure the bit stream containing the information to effectively process the audio signal.

Channel change, multichannel, spatial parameter

Description

Method and apparatus for encoding / decoding audio signal {Method and Apparatus for encoding / decoding audio signal}

1 illustrates an embodiment for conceptual description of an audio signal processing apparatus according to the present invention.

2 is a view for explaining an embodiment of up-mixing a down-mixed signal using a channel conversion module according to the present invention.

3 is a view for explaining an embodiment of generating an output channel by upmixing an input channel to a multi-channel according to the present invention.

4 is a diagram illustrating an embodiment of a spatial parameter configuration syntax according to the present invention.

5 is a diagram illustrating an embodiment of channel configuration information syntax according to the present invention.

6 is a view for explaining an embodiment of the number of bits indicating the number of channel conversion box according to the number of input channels according to the present invention;

FIG. 7 illustrates an embodiment of a number of bits representing channel remapping information according to the number of input channels according to the present invention.

8 illustrates an embodiment of a method for channel remapping using channel remapping information according to the present invention.

9 illustrates another embodiment of channel configuration information syntax according to the present invention.

10 is a flowchart illustrating a decoding method of an audio signal according to the present invention.

* Explanation of symbols for main parts of the drawings

10: encoding device 20: decoding device

100: space encoder 101: downmix module

102: spatial parameter extraction module 120: audio encoder

130: audio decoder 140: space decoder

141: synthesis module 200: TTT module

210, 220, 230, 240, 250: OTT Module

300: channel remapping module

The present invention relates to a method and apparatus for encoding / decoding an audio signal, and more particularly, to a method for constructing an effective bit stream in a method of using downmixing and additional information of a signal in a multichannel audio coding technique.

The standard for digital video and digital audio is the standard for compression and reconstruction of each signal. The standard for digital system divides compressed video and audio into packets of a certain size, and then provides timing information and stream related information. In addition, it is necessary to multiplex and transmit, and vice versa, to obtain timing information, stream related information, and the like, and to separate compressed video and audio, respectively.

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

The psychoacoustic model takes unnecessary part in the coding process by taking advantage of the way in which a human recognizes a sound, for example, a sound that is not heard after a loud sound, but only a sound corresponding to a frequency of 20 Hz to 20000 Hz. By removing the signal for, we can effectively reduce the amount of data needed.

Currently, audio standard technologies such as MPEG-1 audio, 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 multi-channel audio signal called "MPEG Surround" has been developed. The MPEG surround method is a compressed stereo (or mono) audio signal and low bit-rate spatial information. By using channels, the transmission efficiency of a multichannel audio signal is greatly improved.

However, since the number of bits is used for an unnecessary portion for coding spatial information of a multichannel audio signal in the MPEG surround method, there is a problem in that the efficiency of encoding, transmitting and decoding the signal is not good.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and in coding a multichannel audio signal, by representing spatial information in an effective manner, reducing the amount of data used for the spatial information, thereby compressing the multichannel audio signal. And an encoding and decoding method capable of improving transmission efficiency.

In order to achieve the above object, the present invention provides the steps of (a) checking a channel configuration identifier; and (b) if the channel configuration is not predetermined, a first channel conversion in which the number of bits corresponding to the number of input channels is allocated. And extracting the number information of the module, and (c) generating a multi-channel using the first channel conversion module.

In addition, the present invention provides a module for identifying a channel configuration identifier, and if the channel configuration is not determined, the first number information for extracting the number information of the first channel conversion module to which the number of bits corresponding to the number of input channels is allocated. And an extracting unit and a first channel conversion module for generating a multichannel using the extracted number information.

In addition, when the channel configuration is not defined in advance, generating the number information of the first channel conversion module to which the number of bits corresponding to the number of output channels is allocated, and the number information of the first channel conversion module Accordingly, the present invention provides a method of encoding an audio signal, the method comprising generating configuration information of a second channel conversion module.

In addition, when the channel configuration is not determined in advance, the first generation unit for generating information on the number of the first channel conversion module is assigned a number of bits corresponding to the number of output channels, and the number of the first channel conversion module It provides a device for encoding an audio signal comprising a second generator for generating configuration information of the second channel conversion module according to the information.

The present invention also includes a channel configuration identifier, and if the channel configuration is not determined, the audio information comprising the number information of the first channel conversion module to which the number of bits corresponding to the number of input channels is allocated. Provide a signal.

Therefore, according to the present invention, it is possible to effectively reduce the amount of data by compressing an audio signal to a specific number such as mono or stereo in multichannel audio coding, and transmitting or storing the spatial information of the audio signal together. It is possible to effectively configure the included bit stream to effectively process the audio signal.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can be specifically realized for the above purpose.

In addition, the terms used in the present invention was selected as a general term widely used as possible now, but in some cases, the term is arbitrarily selected by the applicant, in which case the meaning is described in detail in the description of the invention, It is to be understood that the present invention is to be understood as the meaning of terms rather than the names of terms.

In this regard, in the present invention, “spatial information” means down-mixing multichannels in an encoding unit and receiving signals transmitted by a decoding unit to perform up-mix to generate multichannels. Means necessary information. Although the spatial information is described based on the spatial parameters, it is to be understood that the present invention is not limited thereto.

In addition, the spatial parameter is used when generating three channels from two channels and an ICC (Inter Channel Coherences) representing a channel level difference (CLD) representing an energy difference between two channels, and a correlation between two channels. Channel Prediction Coefficients (CPC), which are prediction coefficients.

In this regard, in the present invention, a "channel configuration identifier" means information indicating a channel configuration of a specific signal. The channel configuration identifier determines whether the channel configuration is predetermined or not predetermined. The predetermined channel configuration is 5-1-5 case and 5-2-5 case. Although "bsTreeConfig" is described as an example of the channel configuration identifier, it is obvious that the present invention is not limited thereto.

In this regard, in the present invention, "channel conversion module" means a module for converting a specific number of input channels into a specific output channel number different from the number of input channels, and one of the channel conversion modules is referred to as a first channel conversion module. In addition, another channel conversion module is referred to as a second channel conversion module.

For example, the first channel conversion module converts an output channel into three when two input channels are provided. The second channel is based on a two-to-three (TTT) module or a TTT box. The conversion module will be described based on the OTT (One to Two: OTT) module or OTT box that converts the output channel into two when the input channel is one.

However, the present invention is not limited to the TTT module and the OTT module, and it is apparent that the first channel conversion module and the second channel conversion module are applicable to the case where the input channel and the output channel have any number. Put it.

In this regard, in the present invention, "channel configuration information" means checking the channel configuration identifier to include information on the channel configuration when the channel configuration is not predetermined, and in particular, when the channel configuration identifier is not predetermined. Shows information about channel configuration.

For example, since "TreeDescription ()" includes the channel configuration information in spatial parameter configuration, which is spatial information, it is obvious that the present invention is not limited to the above example.

In this regard, in the present invention, "Channel Re-mapping Information" refers to information when reordering input channels, that is, information for remapping an input channel to generate a multi-channel. it means. Although the channel remapping information is described based on "bsChannelRemapping [ch]", it is obvious that the present invention is not limited thereto.

In addition, in the present invention, a "channel remapping module" refers to a module for remapping an input channel according to channel remapping information.

FIG. 1 illustrates an embodiment for conceptual description of an audio signal processing apparatus according to the present invention. In particular, FIG. 1 is a diagram illustrating an apparatus for encoding and decoding an audio signal in MPEG surround.

The encoding device 10 encodes a downmixed audio signal and a spatial encoder 100 including a downmix module 101 and a spatial parameter estimation module 102. It is configured to include an audio encoder (Audio Encoder) (120).

,

,...,

)로 입력되면, 다운 믹스 모듈(101)은 미리 정해진 다운 믹스 정보 또는 외부 제어 명령에 따라 특정 개수의 채널로 입력된 오디오 신호의 다운 믹스를 수행하여 다운 믹스 채널을 생성하고, 상기 다운 믹스 채널로 다운 믹스된 오디오 신호를 출력하면, 상기 출력된 신호는 오디오 인코더(120)에 입력된다.The audio signal is N multichannel (

,

, ...,

), The downmix module 101 generates a downmix channel by downmixing an audio signal input to a specific number of channels according to predetermined downmix information or an external control command, and generates a downmix channel. When the down mixed audio signal is output, the output signal is input to the audio encoder 120.

,

)을 가지거나, 또는 다운 믹스 명령에 따라 특정 개수의 채널을 가질 수 있다. 이때, 다운 믹스된 채널의 개수는 설정가능하다.Here, the downmixed channel may be one channel or two channels (

,

) Or a certain number of channels depending on the downmix command. At this time, the number of down-mixed channels can be set.

Optionally, it is noted that the downmixed audio signal may utilize an externally provided downmixed audio signal, namely an artistic downmix signal.

The audio encoder 120 receives a downmix audio signal transmitted through a downmixed channel, encodes the received signal, and transmits a compressed audio signal.

The spatial parameter extraction module 102 extracts the spatial parameters from the multichannel and transmits the extracted spatial parameters to the decoding apparatus 20.

,

)을 통해 출력한다.The audio decoder 130 of the decoding apparatus 20 receives a compressed audio signal and performs audio decoding of the received compressed audio signal to convert a down mixed audio signal into a stereo channel (

,

)

In this case, when the decoding device 20 of the audio signal cannot decode the multi-channel, the decoding of the compressed audio signal may be performed and output directly as a mono or stereo audio signal, which may improve compatibility between the decoding devices of the audio signal. It is necessary for that.

,

, ...,

)을 생성하고, 상기 생성된 멀티채널을 통해서 멀티채널 오디오 신호를 출력한다.The synthesis module 141 of the spatial decoder 140 receives an audio stereo signal from the audio decoder 130, and receives the spatial parameters from the spatial parameter extraction module 102 of the encoding apparatus 10. Parameters, and surround integration to multi-channel (

,

, ...,

), And outputs a multichannel audio signal through the generated multichannel.

As such, a method of downmixing and transmitting a stereo or mono audio signal and transmitting spatial parameters of the multichannel audio signal together instead of directly transmitting the multichannel audio signal is an excellent method in terms of compression and transmission efficiency. .

In this regard, a case in which a spatial decoder (Spatial Decoder) 140 converts a mono- or stereo channel, which is a downmixed channel, into a multi-channel, from 2 to 5.1, will be described in more detail.

The conversion from 2 channels to 5.1 channels is performed in the time / frequency domain. The process is as follows.

First, a two-channel analysis filterbank converts a decoded and transmitted stereo audio signal into a two-channel time / frequency domain audio signal, and the time / frequency domain audio signal uses spatial information, that is, a spatial parameter. The six-channel time / frequency audio signal is up-mixed into a six-channel time / frequency audio signal, and the six-channel time / frequency audio signal is converted into a 5.1-channel audio signal by a six-channel synthesis filterbank.

Currently, there are 5-1-5 and 5-2-5 configuration channel configurations in a pre-defined configuration, and Configurations are tree structures including OTT modules and TTT modules. Structures).

The present invention is for signaling for arbitrary channel configuration (Arbitrary Channel Configuration) and not for a predetermined case in an audio system, in particular for arbitrary channel configuration of an audio signal in MPEG surround.

FIG. 2 is a diagram illustrating an embodiment of up-mixing a down-mixed signal using a channel conversion module according to the present invention. Particularly, the first channel conversion module is a TTT. The second channel conversion module on the basis of the module will be described based on the OTT module, and shows a case of converting five channels into eleven channels using the channel conversion module.

Referring to FIG. 2, an arbitrary decoder tree composed of one TTT module and five OTT modules is illustrated.

과

를 수신하는 TTT 모듈(200)은 상기 2개의 채널을 3개의 채널로 변환하고, 상기 3개의 채널로 3개의 신호를 출력하고, 상기 TTT 모듈(200)로부터 출력된 3개의 신호 중 첫 번째 신호는 OTT 모듈(220)에 입력되어 두 개의 채널로 출력신호

과

를 출력하고, 두 번째 신호는 OTT 모듈(230)에 입력되어 두 개의 채널로 출력신호

과

를 출력하고, 세 번 째 신호는 OTT 모듈(240)에 입력되어 두 개의 채널로 출력신호

과

를 출력한다.Input signal to 2 channels

and

Receiving the TTT module 200 converts the two channels into three channels, and outputs three signals to the three channels, the first of the three signals output from the TTT module 200 is Input signal to two channels input to OTT module 220

and

The second signal is input to the OTT module 230 and the output signal to the two channels

and

The third signal is input to the OTT module 240 and the output signal to the two channels

and

Outputs

와

는 OTT 모듈이 존재하지 않는 경우를 나타내는 비트 시퀀스(Bit-sequence)가 '0'인 경우로 OTT 모듈과 연결되지 않고 바로 출력신호

와

로 출력한다.And the input signal

Wow

The bit sequence representing the case where the OTT module does not exist is '0' and the output signal is not connected to the OTT module.

Wow

Will output

는 비트 시퀀스(Bit-sequence)가 '10100'인 경우로 첫 번째 OTT 모듈(210)에 의해서 2개의 채널로 변환되어, 상기 2채널 중 하나의 채널을 통해 출력된 신호는 더 이상 변환되지 않아 출력신호

이 출력되고, 상기 2채널 중 다른 하나의 채널을 통해 출력된 신호는 다시 OTT 모듈(250)에 의해 2개의 채널로 변환되고, 상기 변환된 2개의 채널을 통해서 출력신호

과

를 출력한다.And the input signal

The bit sequence is '10100', and the bit sequence is converted into two channels by the first OTT module 210 so that the signal output through one of the two channels is no longer converted and output. signal

Is output, and the signal output through the other one of the two channels is converted into two channels by the OTT module 250 again, and the output signal through the two converted channels

and

Outputs

3 is a view for explaining an embodiment of generating an output channel by upmixing an input channel to a multi-channel according to the present invention. In particular, when up-mixing from three input channels to 12 output channels. It is shown.

Referring to FIG. 3, this complete tree is described by four successive steps, where the input channel is a channel remapping module using channel remapping information "bsChannelRemapping [ch]". Re-ordered at (300).

For example, if there is one or more TTT modules determined by the number information of the TTT module, the first channel and the second channel after channel remapping become two inputs of the first TTT module, and three channels after channel remapping. The first and fourth channels are the two inputs of the second TTT module.

After the channel remapping in FIG. 3, the first channel and the second channel become input channels of the TTT module 310, and the TTT module 310 converts two channels into three channels to serve as a subtree. The tree "A", the subtree "B", and the subtree "C" are generated.

The first subtree, subtree "A", produces three output channels, including three OTT modules 320, 360, and 370, and the second subtree, subtree "B", is the OTT module ( 330 to generate two output channels, and the third subtree, subtree "C", includes the OTT module 340 to generate two output channels.

Also, after the channel remapping, the subtree "D", the fourth subtree not related to the TTT module 310, generates four output channels including three OTT modules 350, 380, and 390.

Therefore, there are 12 output channels for the three input channels, and each output channel is matched with each output channel and the external speaker by the output channel position information.

4 is a diagram illustrating an embodiment of a spatial parameter configuration syntax according to the present invention.

Referring to FIG. 4, the channel configuration identifier indicates a channel configuration and defines a tree configuration. In addition, the channel configuration identifier "bsTreeConfig" includes information about the channel configuration in 4 bits.

For example, if "bsTreeConfig" is "0", it means 5151 configuration, "bsTreeConfig" is "1" means 5152 configuration, "bsTreeConfig" is "2" means 525 configuration, and "bsTreeConfig" is '15' means that the entire tree description is signaled.

If the "bsTreeConfig" is "15" and extracts the channel configuration identifier, tree description information is extracted from "TreeDescription ()" including the channel configuration information. Hereinafter, "TreeDescription ()" is described in detail with reference to FIG. Let's take a look.

5 is a view for explaining an embodiment of the channel configuration information syntax according to the present invention, in which the channel configuration information refers to tree description information.

Referring to FIG. 5, "TreeDescription ()" is a typical element for describing Tree, which is a channel configuration, and "bsNumInChan" means information of the number of input channels, and "" which is the number of input channels. numInChan "is equal to" bsNumInChan + 1 ", and the number of bits representing the number information of the input channel is 4 bits.

In addition, in the present invention, "bsNumTttBoxes" indicates the number of TTT boxes, and the range is between 0 and half of the number of input channels, that is, between 0 <= bsNumTttBoxes <= numInChan / 2.

In particular, in the present invention, "bsNumTttBoxes" varies the bit field according to the number of TTT boxes. When "numInChan" is in the range of 2 ^ (n-1) to (2 ^ n) -1, the "bsNumTttBoxes" The number of bits representing the length is variable to n-1 bits. For example, if "numInChan" is 1 to 16, the length of "bsNumTttBoxes" is represented by any one of 0 to 4 bits. For details, refer to FIG. In the following description, n is an arbitrary integer.

Also, in the present invention, "bsChannelRemapping [ch]" is a field indicating channel remapping information for each input channel according to a defined number of input channels, and the channel remapping module performs channel remapping according to the channel remapping information.

When the number of TTT boxes is determined for arbitrary input channels, the positions of the TTT boxes are also determined.

In this regard, in the bit stream structure describing the relationship between the input channel and the output channel, the remapping information for each input channel has the same number of information as the number of input channels, and has one less information than the number of input channels. There is a case.

The range of channel remapping information for all channels is between 0 and the number of input channels, that is, between 0 <= bsChannelRemapping [ch] <numInChan.

In particular, the "bsChannelRemapping [ch]" varies the number of bits including channel remapping information for each input channel according to the number of input channels, where "numInChan" is 2 ^ (n-1) to (2 ^ n). When in the range of -1, the number of bits representing the length of "bsChannelRemapping [ch]" is variable by n bits.

For example, when "numInChan" is 1 to 16, the number of bits representing "bsChannelRemapping [ch]" is represented by any one of 0 to 4 bits. A detailed description thereof will be described with reference to FIG. 7, where n is arbitrary. Means an integer.

In this regard, the channel conversion module configuration information represents the configuration information of the channel conversion module in a tree structure. The channel conversion module configuration information indicates whether an output signal of the channel conversion module is a final output signal in a tree structure or an intermediate signal input to another channel conversion module in the tree structure.

The following description will be made based on "bsOttBoxPresent" indicating configuration information of the second channel conversion module. If the value of "bsOttBoxPresent" is "0", the output signal is the final output signal of the tree structure. If the value of "bsOttBoxPresent" is "1", the output signal is input to another second channel conversion module.

In this regard, the channel change box default information indicates a default of the channel change box. The following description will be made based on "bsOttDefaultCld" indicating a default of spatial information. The "bsOttDefaultCld" includes information of a default value for idxCLD [] [] []. If the value of the "bsOttDefaultCld" is '0', it means a default idxCLD [] [] [] = 0. If the value of "bsOttDefaultCld" is '1', it means a default idxCLD [] [] [] = 15.

In this regard, the channel conversion box mode information indicates in which mode the channel conversion box operates. The following description will be made based on "bsOttModeLfe" indicating mode information of the second channel conversion box.

The "bsOttModeLfe" includes information on which mode the OTT box operates in the normal mode or the LFE mode. When the value of "bsOttModeLfe" is 0, the "bsOttModeLfe" means the OTT box in the normal mode. If the value of bsOttModeLfe "is" 1 ", it means an OTT box in LFE mode.

In this regard, the output channel position information indicates the position information of the output channel in the tree structure. For example, when the output channel position information is described based on "bsOutputChannelPos", the "bsOutputChannelPos" means information indicating the position of each output channel in the tree structure and the loudspeakers (Loudspeakers) that are external speakers.

Hereinafter, the number of bits of "bsNumTttBoxes" and "bsChannelRemapping" indicating the number of TTT boxes and channel remapping information according to the number of input channels according to the present invention will be described with reference to FIGS. 6 and 7.

FIG. 6 is a view for explaining an embodiment of the number of bits representing the number of channel conversion boxes according to the number of input channels according to the present invention. In particular, in the bit stream structure describing the relationship between the input channel and the output channel, Accordingly, the case in which the bit field representing the number of TTT boxes, which means the first channel conversion box, of the channel conversion box is variably described will be described.

In this case, the number of TTT boxes may not exceed half of the number of input channels, and as shown in FIG. 6, the number of bits of bsNumTttBoxes for indicating the number of TTT boxes varies according to the number of input channels, as follows. This will be explained in detail.

Referring to FIG. 6, if "numInChan" is a value of '1', the bit of "bsNumTttBoxes" is set to 0 bits (not used). If "numInChan" is a value in the range of '2 to 3', a bit of "bsNumTttBoxes" is shown. Is 1 bit. If "numInChan" is a value in the range "4-7", the bit of "bsNumTttBoxes" is 2 bits. If "numInChan" is a value in the range "8-15", the bit of "bsNumTttBoxes" is 3 bits. , If "numInChan" is a value of '16', the bit of "bsNumTttBoxes" is 4 bits.

FIG. 7 is a view for explaining an embodiment of the number of bits representing channel remapping information according to the number of input channels according to the present invention. In particular, each bit according to the number of input channels in a bit stream structure describing a relationship between an input channel and an output channel is illustrated. The case where the number of bits including the remapping information for the input channel is varied is described as an example.

In this case, the information included in the channel remapping information means a case of an arbitrary channel index. Since the number of channel remapping information cannot exceed the number of input channels, it will be described in detail below.

Referring to FIG. 7, if "numInChan" is a value of '1', the bit of "bsChannelRemapping [ch]" is set to 0 bits (not used). If "numInChan" is a value of '2', "bsChannelRemapping [ch] is used. If the bit of "is 1 bit, if" numInChan "is a value in the range" 3-4 ", the bit of" bsChannelRemapping [ch] "is 2 bits. If" numInChan "is a value in the range" 5-8 ", it is" bsChannelRemapping [ ch] "bit is 3 bits, and if" numInChan "is a value in the range of" 9-16 ", the bit of" bsChannelRemapping [ch] "is 4 bits.

By using such a scheme (Scheme), when "numInChan" has a smaller value, it is possible to reduce the number of bits of "bsNumTttBoxes" and "bsChannelRemapping [ch]" to perform more efficient audio coding.

 In relation to this, i = 0, 1, ..., numInChan- for a value of "numInChan" which is the number of input channels and "bsChannelRemapping [i]" indicating remapping information for a particular i-th input channel indicating any input. By using the relation 1 to 0 <= bsChannelRemapping <numInChan, it is possible to express the entire combination of "bsChannelRemapping [i]", which can be expressed as the following formula.

FIG. 8 is a diagram illustrating an embodiment of a method for remapping a channel using channel remapping information according to the present invention. In particular, FIG. 8 illustrates a case in which channel remapping is performed using one channel remapping information less than the number of input channels. will be.

The channel remapping information "bsChannelRemapping" is one-to-one mapped and reordered with the input channel. In this case, the unmapped channel, which is the last element of "bsChannelRemapping", is the mapping information of the previous elements, "bsChannelRemapping [0]. ..numInChan-2] "can be used to map, so" bsChannelRemapping [numInChan-1] ", which is the channel mapping information of the last element, can be omitted.

The present invention is an integer of 0 <= bsChannelRemapping [i] <numInChan for "bsChannelRemapping [i]" indicating the value of "numInChan" which is the number of specific input channels and remapping information for the i-th input channel, and i = 0, Use the relation 1, ..., numInChan-1.

That is, when the encoding apparatus includes and transmits channel repacking information less than the number of input channels in the bit stream, the decoding apparatus receives the bit stream and performs channel remapping. The bit stream includes only "bsChannelRemapping [i]" for numInChan-1 input channels.

From the bit stream, numInChan-1 "bsChannelRemapping [i]" is extracted, and the value of numInChan-th "bsChannelRemapping [numInChan-1]" is calculated using a relationship of 0 <= bsChannelRemapping [i] <numInChan. It is as follows.

bsChannelRemapping[numInChan-1]=

bsChannelRemapping [numInChan-1] =

For example, referring to FIG. 8 and the above equation, since channel remapping information includes information on which channels are relocated, when channel relocation is performed using the channel remapping information, "bsChannelRemapping [0]" is set to Input channel # 1. , "bsChannelRemapping [1]" is relocated to Input channel # n-1, ..., "bsChannelRemapping [n-2]" is relocated to Input channel # n-2, and the last element "bsChannelRemapping [n-1]" Eventually relocates to Input channel # 0.

That is, if the difference between the sum of the channel numbers of the remapping channels mapped to the input channel and the sum of the channel numbers of the remapping channels is obtained, the input channel mapped to the last remapping channel is determined.

In relation to this, it is possible to express a combination of numInChan-1 "bsChannelRemapping [i]", which can be expressed by the following expression.

FIG. 9 is a diagram for explaining another embodiment of channel configuration information syntax according to the present invention. In this case, the channel configuration information refers to tree description information.

In particular, the difference from the syntax described with reference to FIG. 5 is that the channel remapping information includes one less information than the number of input channels, so the last channel remapping information is not included in the bit stream and should be calculated by the decoder. The last channel remapping information is based on "bsCannelRemapping [numInChan-1]".

Referring to FIG. 9, the number of bits of "bsNumTttBoxes" is determined by the number of input channels "numInChan", which is expressed as follows.

No. of bits of bsNumTttBoxes = ceil (log ((numInChan + 1) / 2))

In addition, the number of bits of "bsChannelRemapping [ch]" is determined by the number of input channels "numInChan", which is represented by the following equation.

No. of bits of bsChannelRemapping = ceil (log2 (numInChan))

Thus, the present invention makes it possible to code "bsNumTttBoxes" and "bsChannelRemapping [ch]" more effectively.

In this regard, how the number of bits according to the present invention is reduced when the number of input channels is N. FIG. The number of bits required for the number N of input channels is divided into a case where the number of bits is fixed and a case where the number of bits is fixed.

If the number of bits is fixed, 4 and 4N bits are required for the "bsNumTttBoxes" and "bsChannelRemapping [ch]", respectively. If the number of bits is variable, each of the "bsNumTttBoxes" and "bsChannelRemapping [ch]" ceil (log2 ((N +1) / 2), ceil (log2 (N)) * (N-1) bits are required, so the bit savings in accordance with the present invention are 4-ceil (log2 ((N + 1) / 2), 4N−, respectively). ceil (log2 (N)) * (N-1)

For example, in case of 5-2-5, in which 5 channels are downmixed to 2 channels and then transmitted and then upmixed to 5 channels again, when the number of bits is fixed, "bsNumTttBoxes" and "bsChannelRemapping [ch]" The bits used for all are 12 bits, but in the case where the number of bits is variable according to the present invention, the bits used for both "bsNumTttBoxes" and "bsChannelRemapping [ch]" are 2 bits. Therefore, it can be seen that bit saving of 10 bits is possible.

10 is a flowchart illustrating a method of decoding an audio signal according to the present invention, and more particularly, a method of generating a multichannel using information in a bit stream of a received audio signal.

The decoding apparatus receives the spatial parameter bit stream and checks the channel configuration identifier (S10).

After the check (S10), it is determined whether the channel configuration is predetermined (S20).

As a result of the check (S20), if the channel configuration is predetermined, since the decoding apparatus knows the information of the channel conversion module and the information for generating the multi-channel in the form of a table or the like, it generates a multi-channel by using this (S30). ).

As a result of the check (S20), if the channel configuration is not determined, the number information of the first channel conversion module to which the number of bits corresponding to the number of input channels is allocated is extracted (S40).

After extracting the number information of the first channel conversion module, the channel remapping information extraction unit extracts channel remapping information, and the channel remapping module performs channel remapping of the input channel (S50). Here, the bit field including the channel remapping information is allocated the number of bits corresponding to the number of input channels. For example, the channel remapping information may include the same number of information as the input channel or may include one less information than the input channel.

After performing the channel remapping, the second channel conversion module configuration information is extracted (S60). Here, the second channel conversion module configuration information refers to information including location information of the second channel conversion modules.

The multi-channel is generated using the information of the channel conversion module for the channel remapped channel in the step (S50) (S70). In other words, the positions of the first channel conversion module and the second channel conversion module, which are channel conversion modules, are determined according to the information extracted in steps S40 and S60, thereby generating multichannels of the remapped channels.

The present invention is not limited to the above-described embodiments, and as can be seen in the appended claims, modifications can be made by those skilled in the art to which the invention pertains, and such modifications are within the scope of the present invention.

A method and apparatus for encoding / decoding an audio signal according to the present invention as described above are as follows.

First, in multichannel audio coding, it is possible to effectively reduce the amount of data by compressing a signal to a certain number such as mono or stereo and transmitting or storing spatial information together.

Second, it is possible to effectively configure the bit stream containing the spatial information to effectively process the audio signal.

Claims (17)

(a) identifying a channel configuration identifier; (b) if the channel configuration is not determined, extracting number information of the first channel conversion module to which the number of bits corresponding to the number of input channels is allocated; (c) generating a multi-channel using the first channel conversion module. According to claim 1, wherein step (b), And extracting channel configuration information. The method of claim 1, The first channel conversion module is a decoding method of an audio signal, characterized in that the output channel is three channels if the input channel is two channels. The method of claim 1, And when the number information of the first channel conversion module is confirmed, the configuration of the second channel conversion module is determined. The method of claim 4, wherein The second channel conversion module is a method of decoding an audio signal, characterized in that the output channel is two channels if the input channel is one channel. The method of claim 1, And the number of first channel conversion modules is in a range between 0 and half of the number of input channels. The method of claim 1, When the number of input channels is in the range of 2 ^ (n-1) to (2 ^ n) -1 for any number n, the number information of the first channel conversion module is represented by n-1 bits. Decoding method of an audio signal, characterized in that. The method of claim 1, And the number of bits representing the number information of the first channel conversion module is ceil (log2 ((numInChan + 1) / 2)). The method according to claim 1 or 4, The position of the first channel conversion module is determined using the number information of the first channel conversion module, wherein the first channel conversion module is configured to have a configuration position before the second channel conversion module. Decoding method. The method of claim 1, And the input channel is remapped by a channel remapping module. The method of claim 1, The channel conversion module number field, which is a field indicating the number information of the first channel conversion module, is represented by any one of 0 to 4 bits. The method of claim 11, If the number of input channels is 16, the channel conversion module number field is 4 bits. If the number of input channels is 8-15, the channel conversion box module field is 3 bits. If the number of input channels is 4-7, the channel conversion module number field is 2 bits, and if the number of input channels is in the range of 2-3, the channel conversion module number field is 1 bit, and if the number of input channels is 1, the channel conversion module number field is 0 bit. A module for checking a channel configuration identifier, A first number information extracting unit extracting number information of a first channel conversion module to which the number of bits corresponding to the number of input channels is allocated, if the channel configuration is not determined; And a first channel conversion module for generating a multi-channel by using the extracted number information. If the channel configuration is not previously defined, generating number information of the first channel conversion module to which the number of bits corresponding to the number of output channels is allocated; And generating configuration information of the second channel conversion module according to the number information of the first channel conversion module. If the channel configuration is not predetermined, the first generation unit for generating the number information of the first channel conversion module to which the number of bits corresponding to the number of output channels is allocated; And a second generator for generating configuration information of the second channel conversion module according to the number information of the first channel conversion module. Contains a channel configuration identifier, If the channel configuration is not determined, the audio signal comprising the information on the number of the first channel conversion module allocated the number of bits corresponding to the number of input channels. The method of claim 16, The audio signal is characterized in that it further comprises a channel configuration information.

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