Patent Publication Number: US-2023145725-A1

Title: Multi-channel audio signal encoding and decoding method and apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/CN2021/106514, filed on Jul. 15, 2021, which claims priority to Chinese Patent Application No. 202010699711.8, filed on Jul. 17, 2020. The disclosures of the aforementioned applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This application relates to audio coding technologies, and in particular, to multi-channel audio signal encoding and decoding methods and apparatuses. 
     BACKGROUND 
     With continuous development of multimedia technologies, audio has been widely used in the fields such as multimedia communication, consumer electronics, virtual reality, and human-computer interaction. Audio coding is one of key technologies of the multimedia technologies. In audio coding, redundant information in a raw audio signal is removed to reduce a data amount, so as to facilitate storage or transmission. 
     Multi-channel audio coding is coding of at least two channels, including common 5.1 channels, 7.1 channels, 7.1.4 channels, 22.2 channels, and the like. Multi-channel signal screening, coupling, stereo processing, multi-channel side information generation, quantization processing, entropy encoding processing, and bitstream multiplexing are performed on a multi-channel raw audio signal to form a serial bitstream, so as to facilitate transmission in a channel or storage in a digital medium. 
     How to reduce encoding bits of multi-channel side information to improve quality of a reconstructed signal on a decoder side becomes an urgent technical problem to be resolved. 
     SUMMARY 
     This application provides multi-channel audio signal encoding and decoding methods and apparatuses, to improve quality of a coded audio signal. 
     According to a first aspect, an embodiment of this application provides a multi-channel audio signal encoding method. The method may include: obtaining audio signals of P channels in a current frame of a multi-channel audio signal, where P is a positive integer greater than 1, the P channels include K channel pairs, each channel pair includes two channels, K is a positive integer, and P is greater than or equal to K×2; obtaining respective energy/amplitudes of the audio signals of the P channels; generating energy/amplitude equalization side information of the K channel pairs based on the respective energy/amplitudes of the audio signals of the P channels; and encoding the energy/amplitude equalization side information of the K channel pairs and the audio signals of the P channels to obtain an encoded bitstream. 
     In this implementation, the energy/amplitude equalization side information of the channel pairs is generated, and the encoded bitstream carries the energy/amplitude equalization side information of the K channel pairs without carrying energy/amplitude equalization side information of an uncoupled channel. This can reduce a quantity of bits of energy/amplitude equalization side information in the encoded bitstream and a quantity of bits of multi-channel side information. In addition, saved bits can be allocated to another functional module of an encoder, so as to improve quality of a reconstructed audio signal of a decoder side and improve encoding quality. 
     For example, the saved bits may be used to encode the multi-channel audio signal, so as to reduce a compression rate of a data part and improve the quality of the reconstructed audio signal of the decoder side. 
     In other words, the encoded bitstream includes a control information part and the data part. The control information part may include the foregoing energy/amplitude equalization side information, and the data part may include the foregoing multi-channel audio signal. That is, the encoded bitstream includes the multi-channel audio signal and control information generated in a process of encoding the multi-channel audio signal. In this embodiment of this application, a quantity of bits occupied by the control information part may be reduced, to increase a quantity of bits occupied by the data part and further improve the quality of the reconstructed audio signal of the decoder side. 
     It should be noted that the saved bits may alternatively be used for transmission of other control information. This embodiment of this application is not limited by the foregoing examples. 
     In a possible design, the K channel pairs include a current channel pair, and energy/amplitude equalization side information of the current channel pair includes fixed-point energy/amplitude scaling ratios and energy/amplitude scaling identifiers of the current channel pair. The fixed-point energy/amplitude scaling ratio is a fixed-point value of an energy/amplitude scaling ratio coefficient, the energy/amplitude scaling ratio coefficient is obtained based on respective energy/amplitudes of audio signals of two channels of the current channel pair before energy/amplitude equalization and respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization, the energy/amplitude scaling identifier is used to identify that the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization is or are increased or decreased relative to the respective energy/amplitudes of the audio signals before energy/amplitude equalization. 
     In this implementation, the decoder side may perform energy de-equalization based on the fixed-point energy/amplitude scaling ratios and the energy/amplitude scaling identifiers of the current channel pair, to obtain a decoded signal. 
     A floating-point energy/amplitude scaling ratio coefficient is transformed into the fixed-point energy/amplitude scaling ratio. This can reduce bits occupied by the energy/amplitude equalization side information, and further improve transmission efficiency. 
     In a possible design, the K channel pairs include the current channel pair, and the generating energy/amplitude equalization side information of the K channel pairs based on the respective energy/amplitudes of the audio signals of the P channels includes: determining, based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair before energy/amplitude equalization, the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization; and generating the energy/amplitude equalization side information of the current channel pair based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair before energy/amplitude equalization and the respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization. 
     In this implementation, energy/amplitude equalization is performed on the two channels of the channel pair, so that a large energy difference can still be maintained between channel pairs with a large energy difference after energy/amplitude equalization. In this way, an encoding requirement of a channel pair with large energy/a large amplitude is met in a subsequent encoding processing procedure, encoding efficiency and encoding effect are improved, and the quality of the reconstructed audio signal of the decoder side is further improved. 
     In a possible design, the current channel pair includes a first channel and a second channel, and the energy/amplitude equalization side information of the current channel pair includes a fixed-point energy/amplitude scaling ratio of the first channel, a fixed-point energy/amplitude scaling ratio of the second channel, an energy/amplitude scaling identifier of the first channel, and an energy/amplitude scaling identifier of the second channel. 
     In this implementation, the decoder side may perform energy de-equalization based on respective fixed-point energy/amplitude scaling ratios and respective energy/amplitude scaling identifiers of the two channels of the current channel pair, to obtain the decoded signal, and further reduce bits occupied by the energy/amplitude equalization side information of the current channel pair. 
     In a possible design, the generating the energy/amplitude equalization side information of the current channel pair based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair before energy/amplitude equalization and the respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization may include: determining an energy/amplitude scaling ratio coefficient of a q th  channel of the current channel pair and an energy/amplitude scaling identifier of the q th  channel based on energy/an amplitude of an audio signal of the q th  channel before energy/amplitude equalization and energy/an amplitude of the audio signal of the q th  channel after energy/amplitude equalization; and determining a fixed-point energy/amplitude scaling ratio of the q th  channel based on the energy/amplitude scaling ratio coefficient of the q th  channel, where q is 1 or 2. 
     In a possible design, the determining, based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization, the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization may include: determining an average energy/amplitude value of the audio signals of the current channel pair based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair before energy/amplitude equalization; and determining, based on the average energy/amplitude value of the audio signals of the current channel pair, the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization. 
     In this implementation, energy/amplitude equalization is performed on the two channels of the channel pair, so that a large energy difference can still be maintained between channel pairs with a large energy difference after energy/amplitude equalization. In this way, an encoding requirement of a channel pair with large energy/a large amplitude is met in a subsequent encoding processing procedure, and the quality of the reconstructed audio signal of the decoder side is further improved. 
     In a possible design, the encoding the energy/amplitude equalization side information of the K channel pairs and the audio signals of the P channels to obtain an encoded bitstream may include: encoding the energy/amplitude equalization side information of the K channel pairs, K, respective channel pair indexes of the K channel pairs, and the audio signals of the P channels, to obtain the encoded bitstream. 
     According to a second aspect, an embodiment of this application provides a multi-channel audio signal decoding method. The method may include: obtaining a to-be-decoded bitstream; demultiplexing the to-be-decoded bitstream to obtain a current frame of a to-be-decoded multi-channel audio signal, a quantity K of channel pairs included in the current frame, respective channel pair indexes of the K channel pairs, and energy/amplitude equalization side information of the K channel pairs; and decoding the current frame of the to-be-decoded multi-channel audio signal based on the respective channel pair indexes of the K channel pairs and the energy/amplitude equalization side information of the K channel pairs, to obtain decoded signals of the current frame, where K is a positive integer, and each channel pair includes two channels. 
     In a possible design, the K channel pairs include a current channel pair, and energy/amplitude equalization side information of the current channel pair includes fixed-point energy/amplitude scaling ratios and energy/amplitude scaling identifiers of the current channel pair. The fixed-point energy/amplitude scaling ratio is a fixed-point value of an energy/amplitude scaling ratio coefficient, the energy/amplitude scaling ratio coefficient is obtained based on respective energy/amplitudes of audio signals of two channels of the current channel pair before energy/amplitude equalization and respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization, the energy/amplitude scaling identifier is used to identify that the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization is or are increased or decreased relative to the respective energy/amplitudes of the audio signals before energy/amplitude equalization. 
     In a possible design, the K channel pairs include the current channel pair, and the decoding the current frame of the to-be-decoded multi-channel audio signal based on the respective channel pair indexes of the K channel pairs and the energy/amplitude equalization side information of the K channel pairs, to obtain decoded signals of the current frame may include: performing stereo decoding processing on the current frame of the to-be-decoded multi-channel audio signal based on a channel pair index corresponding to the current channel pair, to obtain the audio signals of the two channels of the current channel pair of the current frame; and performing energy/amplitude de-equalization processing on the audio signals of the two channels of the current channel pair based on the energy/amplitude equalization side information of the current channel pair, to obtain decoded signals of the two channels of the current channel pair. 
     In a possible design, the current channel pair includes a first channel and a second channel, and the energy/amplitude equalization side information of the current channel pair includes a fixed-point energy/amplitude scaling ratio of the first channel, a fixed-point energy/amplitude scaling ratio of the second channel, an energy/amplitude scaling identifier of the first channel, and an energy/amplitude scaling identifier of the second channel. 
     For technical effects of the multi-channel audio signal decoding method, refer to the technical effects of the foregoing corresponding encoding method. Details are not described herein again. 
     According to a third aspect, an embodiment of this application provides an audio signal encoding apparatus. The audio signal encoding apparatus may be an audio encoder, a chip of an audio encoding device, a system on chip, or a functional module that is of an audio encoder and that is configured to perform the method according to any one of the first aspect or the possible designs of the first aspect. The audio signal encoding apparatus may implement functions performed in the first aspect or the possible designs of the first aspect, and the functions may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the functions. For example, in a possible design, the audio signal encoding apparatus may include an obtaining module, an equalization side information generation module, and an encoding module. 
     According to a fourth aspect, an embodiment of this application provides an audio signal decoding apparatus. The audio signal decoding apparatus may be an audio decoder, a chip of an audio decoding device, a system on chip, or a functional module that is of an audio decoder and that is configured to perform the method according to any one of the second aspect or the possible designs of the second aspect. The audio signal decoding apparatus may implement functions performed in the second aspect or the possible designs of the second aspect, and the functions may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the functions. For example, in a possible design, the audio signal decoding apparatus may include an obtaining module, a demultiplexing module, and a decoding module. 
     According to a fifth aspect, an embodiment of this application provides an audio signal encoding apparatus, including a non-volatile memory and a processor that are coupled to each other. The processor invokes program code stored in the memory to perform the method according to any one of the first aspect or the possible designs of the first aspect. 
     According to a sixth aspect, an embodiment of this application provides an audio signal decoding apparatus, including a non-volatile memory and a processor that are coupled to each other. The processor invokes program code stored in the memory to perform the method according to any one of the second aspect or the possible designs of the second aspect. 
     According to a seventh aspect, an embodiment of this application provides an audio signal encoding device, including an encoder. The encoder is configured to perform the method according to any one of the first aspect or the possible designs of the first aspect. 
     According to an eighth aspect, an embodiment of this application provides an audio signal decoding device, including a decoder. The decoder is configured to perform the method according to any one of the second aspect or the possible designs of the second aspect. 
     According to a ninth aspect, an embodiment of this application provides a computer-readable storage medium, including the encoded bitstream obtained by using the method according to any one of the first aspect or the possible designs of the first aspect. 
     According to a tenth aspect, an embodiment of this application provides a computer-readable storage medium, including a computer program. When the computer program is executed on a computer, the computer is enabled to perform the method according to any one of the first aspect or the possible designs of the first aspect or the method according to any one of the second aspect or the possible designs of the second aspect. 
     According to an eleventh aspect, this application provides a computer program product. The computer program product includes a computer program. When the computer program is executed by a computer, the method according to any one of the first aspect or the method according to any one of the second aspect is performed. 
     According to a twelfth aspect, this application provides a chip, including a processor and a memory. The memory is configured to store a computer program, and the processor is configured to invoke and run the computer program stored in the memory, to perform the method according to any one of the first aspect or the method according to any one of the second aspect. 
     According to a thirteenth aspect, this application provides a coding device. The coding device includes an encoder and a decoder. The encoder is configured to perform the method according to any one of the first aspect or the possible designs of the first aspect. The decoder is configured to perform the method according to any one of the second aspect or the possible designs of the second aspect. 
     According to the multi-channel audio signal encoding and decoding methods and apparatuses in embodiments of this application, the audio signals of the P channels in the current frame of the multi-channel audio signal and the respective energy/amplitudes of the audio signals of the P channels are obtained, the P channels include K channel pairs, the energy/amplitude equalization side information of the K channel pairs is generated based on the respective energy/amplitudes of the audio signals of the P channels, and the energy/amplitude equalization side information of the K channel pairs and the audio signals of the P channels are encoded to obtain the encoded bitstream. The energy/amplitude equalization side information of the channel pairs is generated, and the encoded bitstream carries the energy/amplitude equalization side information of the K channel pairs without carrying energy/amplitude equalization side information of an uncoupled channel. This can reduce a quantity of bits of energy/amplitude equalization side information in the encoded bitstream and a quantity of bits of multi-channel side information. In addition, saved bits can be allocated to another functional module of an encoder, so as to improve quality of a reconstructed audio signal of a decoder side and improve coding quality. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic diagram of an example of an audio coding system according to an embodiment of this application; 
         FIG.  2    is a flowchart of a multi-channel audio signal encoding method according to an embodiment of this application; 
         FIG.  3    is a flowchart of a multi-channel audio signal encoding method according to an embodiment of this application; 
         FIG.  4    is a schematic diagram of a processing procedure of an encoder side according to an embodiment of this application; 
         FIG.  5    is a schematic diagram of a processing procedure of a multi-channel encoding processing unit according to an embodiment of this application; 
         FIG.  6    is a schematic diagram of a multi-channel side information writing procedure according to an embodiment of this application; 
         FIG.  7    is a flowchart of a multi-channel audio signal decoding method according to an embodiment of this application; 
         FIG.  8    is a schematic diagram of a processing procedure of a decoder side according to an embodiment of this application; 
         FIG.  9    is a schematic diagram of a processing procedure of a multi-channel decoding processing unit according to an embodiment of this application; 
         FIG.  10    is a flowchart of parsing multi-channel side information according to an embodiment of this application; 
         FIG.  11    is a schematic diagram of a structure of an audio signal encoding apparatus  1100  according to an embodiment of this application; 
         FIG.  12    is a schematic diagram of a structure of an audio signal encoding device  1200  according to an embodiment of this application; 
         FIG.  13    is a schematic diagram of a structure of an audio signal decoding apparatus  1300  according to an embodiment of this application; and 
         FIG.  14    is a schematic diagram of a structure of an audio signal decoding device  1400  according to an embodiment of this application. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Terms such as “first” and “second” in embodiments of this application are only used for distinguishing description, but cannot be understood as indicating or implying relative importance or a sequence. In addition, the terms “include”, “comprise”, or any other variant thereof are intended to cover a non-exclusive inclusion, for example, a series of steps or units. Methods, systems, products, or devices are not necessarily limited to those steps or units that are literally enumerated, but may include other steps or units that are not literally enumerated or that are inherent to such processes, methods, products, or devices. 
     It should be understood that, in this application, “at least one (item)” means one or more and “a plurality of” means two or more. The term “and/or” is used for describing an association relationship between associated objects, and represents that three relationships may exist. For example, “A and/or B” may represent the following three cases: Only A exists, only B exists, and both A and B exist, where A and B may be singular or plural. The character “/” generally indicates an “or” relationship between the associated objects. “At least one of the following items (pieces)” or a similar expression thereof means any combination of these items, including a single item (piece) or any combination of a plurality of items (pieces). For example, at least one of a, b, or c may represent: a, b, c, “a and b”, “a and c”, “b and c”, or “a, b and c”. Each of a, b, and c may be singular or plural. Alternatively, some of a, b, and c may be singular; and some of a, b, and c may be plural. 
     The following describes a system architecture to which an embodiment of this application is applied. Refer to  FIG.  1   .  FIG.  1    shows a schematic block diagram of an example of an audio coding system  10  to which an embodiment of this application is applied. As shown in  FIG.  1   , the audio coding system  10  may include a source device  12  and a destination device  14 . The source device  12  generates encoded audio data. Therefore, the source device  12  may be referred to as an audio encoding apparatus. The destination device  14  can decode the encoded audio data generated by the source device  12 . Therefore, the destination device  14  may be referred to as an audio decoding apparatus. In various implementation solutions, the source device  12 , the destination device  14 , or both the source device  12  and the destination device  14  may include at least one processor and a memory coupled to the at least one processor. The memory may include but is not limited to a RAM, a ROM, an EEPROM, a flash memory, or any other medium that can be used to store desired program code in a form of an instruction or a data structure accessible to a computer, as described in this specification. The source device  12  and the destination device  14  may include various apparatuses, including a desktop computer, a mobile computing apparatus, a notebook (for example, a laptop) computer, a tablet, a set-top box, a telephone handset such as a “smart” phone, a television set, a speaker, a digital media player, a video game console, an in-vehicle computer, any wearable device, a virtual reality (VR) device, a server providing a VR service, an augmented reality (AR) device, a server providing an AR service, a wireless communication device, and a similar device thereof. 
     Although  FIG.  1    depicts the source device  12  and the destination device  14  as separate devices, a device embodiment may alternatively include both the source device  12  and the destination device  14  or functionalities of both the source device  12  and the destination device  14 , that is, the source device  12  or a corresponding functionality and the destination device  14  or a corresponding functionality. In these embodiments, the source device  12  or the corresponding functionality and the destination device  14  or the corresponding functionality may be implemented by using same hardware and/or software, separate hardware and/or software, or any combination thereof. 
     A communication connection between the source device  12  and the destination device  14  may be implemented over a link  13 , and the destination device  14  may receive encoded audio data from the source device  12  over the link  13 . The link  13  may include one or more media or apparatuses capable of moving the encoded audio data from the source device  12  to the destination device  14 . In an example, the link  13  may include one or more communication media that enable the source device  12  to directly transmit the encoded audio data to the destination device  14  in real time. In this example, the source device  12  can modulate the encoded audio data according to a communication standard (for example, a wireless communication protocol), and can transmit modulated audio data to the destination device  14 . The one or more communication media may include a wireless communication medium and/or a wired communication medium, for example, a radio frequency (RF) spectrum or one or more physical transmission lines. The one or more communication media may form a part of a packet-based network, and the packet-based network is, for example, a local area network, a wide area network, or a global network (for example, the internet). The one or more communication media may include a router, a switch, a base station, or another device that facilitates communication from the source device  12  to the destination device  14 . 
     The source device  12  includes an encoder  20 . Optionally, the source device  12  may further include an audio source  16 , a preprocessor  18 , and a communication interface  22 . In a specific implementation, the encoder  20 , the audio source  16 , the preprocessor  18 , and the communication interface  22  may be hardware components in the source device  12 , or may be software programs in the source device  12 . They are separately described as follows. 
     The audio source  16  may include or may be a sound capture device of any type, configured to capture, for example, sound from the real world, and/or an audio generation device of any type. The audio source  16  may be a microphone configured to capture sound or a memory configured to store audio data, and the audio source  16  may further include any type of (internal or external) interface for storing previously captured or generated audio data and/or for obtaining or receiving audio data. When the audio source  16  is a microphone, the audio source  16  may be, for example, a local microphone or a microphone integrated into the source device. When the audio source  16  is a memory, the audio source  16  may be, for example, a local memory or a memory integrated into the source device. When the audio source  16  includes an interface, the interface may be, for example, an external interface for receiving audio data from an external audio source. For example, the external audio source is an external sound capture device such as a microphone, an external storage, or an external audio generation device. The interface may be any type of interface, for example, a wired or wireless interface or an optical interface, according to any proprietary or standardized interface protocol. 
     In this embodiment of this application, the audio data transmitted from the audio source  16  to the preprocessor  18  may also be referred to as raw audio data  17 . 
     The preprocessor  18  is configured to receive and preprocess the raw audio data  17 , to obtain preprocessed audio  19  or preprocessed audio data  19 . For example, preprocessing performed by the preprocessor  18  may include filtering or noise reduction. 
     The encoder  20  (or referred to as an audio encoder  20 ) is configured to receive the preprocessed audio data  19 , and is configured to perform encoding method embodiments described below, to implement application of an audio signal encoding method described in this application on an encoder side. 
     The communication interface  22  may be configured to receive encoded audio data  21 , and transmit the encoded audio data  21  to the destination device  14  or any other device (for example, a memory) over the link  13  for storage or direct reconstruction. The other device may be any device used for decoding or storage. The communication interface  22  may be, for example, configured to encapsulate the encoded audio data  21  into an appropriate format, for example, a data packet, for transmission over the link  13 . 
     The destination device  14  includes a decoder  30 . Optionally, the destination device  14  may further include a communication interface  28 , an audio postprocessor  32 , and a speaker device  34 . They are separately described as follows. 
     The communication interface  28  may be configured to receive the encoded audio data  21  from the source device  12  or any other source. The any other source is, for example, a storage device. The storage device is, for example, a device for storing the encoded audio data. The communication interface  28  may be configured to transmit or receive the encoded audio data  21  over the link  13  between the source device  12  and the destination device  14  or through any type of network. The link  13  is, for example, a direct wired or wireless connection. The any type of network is, for example, a wired or wireless network or any combination thereof, or any type of private or public network, or any combination thereof. The communication interface  28  may be, for example, configured to decapsulate the data packet transmitted through the communication interface  22 , to obtain the encoded audio data  21 . 
     Both the communication interface  28  and the communication interface  22  may be configured as unidirectional communication interfaces or bidirectional communication interfaces, and may be configured to, for example, send and receive messages to establish a connection, and acknowledge and exchange any other information related to a communication link and/or data transmission such as encoded audio data transmission. 
     The decoder  30  (or referred to as a decoder  30 ) is configured to receive the encoded audio data  21 , and provide decoded audio data  31  or decoded audio  31 . In some embodiments, the decoder  30  may be configured to perform decoding method embodiments described below, to implement application of an audio signal decoding method described in this application on a decoder side. 
     The audio postprocessor  32  is configured to postprocess the decoded audio data  31  (also referred to as reconstructed audio data) to obtain postprocessed audio data  33 . Postprocessing performed by the audio postprocessor  32  may include, for example, rendering or any other processing, and may be further configured to transmit the postprocessed audio data  33  to the speaker device  34 . 
     The speaker device  34  is configured to receive the postprocessed audio data  33  to play audio to, for example, a user or a viewer. The speaker device  34  may be or may include any type of speaker configured to play reconstructed sound. 
     Although  FIG.  1    depicts the source device  12  and the destination device  14  as separate devices, a device embodiment may alternatively include both the source device  12  and the destination device  14  or functionalities of both the source device  12  and the destination device  14 , that is, the source device  12  or a corresponding functionality and the destination device  14  or a corresponding functionality. In these embodiments, the source device  12  or the corresponding functionality and the destination device  14  or the corresponding functionality may be implemented by using same hardware and/or software, separate hardware and/or software, or any combination thereof. 
     As will be apparent for a person skilled in the art based on the descriptions, existence and (exact) split of functionalities of the different units or functionalities of the source device  12  and/or the destination device  14  shown in  FIG.  1    may vary depend on an actual device and application. The source device  12  and the destination device  14  may include any one of a wide range of devices, including any type of handheld or stationary device, for example, a notebook or laptop computer, a mobile phone, a smartphone, a pad or a tablet computer, a video camera, a desktop computer, a set-top box, a television set, a camera, an in-vehicle device, a sound box, a digital media player, an audio game console, an audio streaming transmission device (such as a content service server or a content distribution server), a broadcast receiver device, a broadcast transmitter device, smart glasses, or a smart watch, and may not use or may use any type of operating system. 
     The encoder  20  and the decoder  30  each may be implemented as any one of various appropriate circuits, for example, one or more microprocessors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), discrete logic, hardware, or any combinations thereof. If the technologies are implemented partially by using software, a device may store software instructions in an appropriate and non-transitory computer-readable storage medium and may execute the instructions by using hardware such as at least one processor, to perform the technologies of this disclosure. Any one of the foregoing content (including hardware, software, a combination of hardware and software, and the like) may be considered as at least one processor. 
     In some cases, the audio coding system  10  shown in  FIG.  1    is merely an example, and the technologies of this application are applicable to audio coding settings (for example, audio encoding or audio decoding) that do not necessarily include any data communication between an encoding device and a decoding device. In another example, data may be retrieved from a local memory, transmitted in a streaming manner through a network, or the like. An audio encoding device may encode data and store data into the memory, and/or an audio decoding device may retrieve and decode the data from the memory. In some examples, encoding and decoding are performed by devices that do not communicate with one another, but simply encode data to the memory and/or retrieve and decode data from the memory. 
     The encoder may be a multi-channel encoder, for example, a stereo encoder, a 5.1-channel encoder, or a 7.1-channel encoder. 
     The audio data may also be referred to as an audio signal. The audio signal in this embodiment of this application is an input signal in an audio encoding device. The audio signal may include a plurality of frames. For example, a current frame may be specifically a frame in the audio signal. In embodiments of this application, audio signal encoding and decoding of the current frame are used as an example for description. A previous frame or a next frame of the current frame in the audio signal may be correspondingly encoded and decoded based on audio signal encoding and decoding manners of the current frame. Encoding and decoding processes of the previous frame or the next frame of the current frame in the audio signal are not described one by one. In addition, the audio signal in embodiments of this application may be a multi-channel audio signal, that is, includes P channels. Embodiments of this application are used to perform multi-channel audio signal coding. 
     The encoder may perform a multi-channel audio signal encoding method in embodiments of this application, to reduce a quantity of bits of multi-channel side information. In this way, saved bits can be allocated to another functional module of the encoder, to improve quality of a reconstructed audio signal of a decoder side and improve encoding quality. For a specific implementation thereof, refer to specific explanation and description of the following embodiment. 
       FIG.  2    is a flowchart of a multi-channel audio signal encoding method according to an embodiment of this application. This embodiment of this application may be performed by the foregoing encoder. As shown in  FIG.  2   , the method in this embodiment may include the following steps. 
     Step  201 : Obtain audio signals of P channels in a current frame of a multi-channel audio signal and respective energy/amplitudes of the audio signals of the P channels, where the P channels include K channel pairs. The multi-channel signal may be signals of 5.1 channels (correspondingly, P satisfies 5+1=6), signals of 7.1 channels (correspondingly, P satisfies 7+1=8), signals of 11.1 channels (correspondingly, P satisfies 11+1=12), or the like. 
     Each channel pair (channel pair) includes two channels. P is a positive integer greater than 1, K is a positive integer, and P is greater than or equal to K×2. 
     In some embodiments, P=2K. Multi-channel signal screening and coupling are performed on the current frame of the multi-channel audio signal to obtain the K channel pairs. The P channels include the K channel pairs. 
     In some embodiments, P=2×K+Q, and Q is a positive integer. The audio signals of the P channels further include audio signals of Q uncoupled mono channels. Signals of 5.1 channels are used as an example. The 5.1 channels include a left (L) channel, a right (R) channel, a center (C) channel, a low frequency effect (LFE) channel, a left surround (LS) channel, and a right surround (RS) channel. Channels participating in multi-channel processing are obtained through screening from the 5.1 channels based on a multi-channel processing indicator (MultiProcFlag), for example, the channels participating in multi-channel processing include the L channel, the R channel, the C channel, the LS channel, and the RS channel. Coupling is performed between channels participating in multi-channel processing. For example, the L channel and the R channel are coupled to form a first channel pair. The LS channel and the RS channel are coupled to form a second channel pair. The LFE channel and the C channel are uncoupled channels. That is, P=6, K=2, and Q=2. The P channels include the first channel pair, the second channel pair, and the LFE channel and the C channel that are not coupled. 
     For example, a manner of performing coupling between the channels participating in multi-channel processing may be that K channel pairs are determined through a plurality of iterations, that is, one channel pair is determined in one iteration. For example, inter-channel correlation values between any two of the P channels participating in multi-channel processing are calculated in a first iteration, and two channels with highest inter-channel correlation values are selected in the first iteration to form a channel pair. Two channels with highest inter-channel correlation values in remaining channels (channels in the P channels other than the coupled channels) are selected in a second iteration to form a channel pair. By analogy, the K channel pairs are obtained. 
     It should be noted that, in this embodiment of this application, another coupling manner may alternatively be used to determine the K channel pairs. The foregoing example description of coupling is not limited in this embodiment of this application. 
     Step  202 : Generate energy/amplitude equalization side information of the K channel pairs based on the respective energy/amplitudes of the audio signals of the P channels. 
     It should be noted that “energy/amplitude” in this embodiment of this application represents energy or an amplitude. In addition, in an actual processing procedure, for processing of a frame, if energy processing performed at the beginning, energy processing is performed in all subsequent processing; or if amplitude processing is performed at the beginning, amplitude processing is performed in all subsequent processing. 
     For example, the energy equalization side information of the K channel pairs is generated based on the energy of the audio signals of the P channels. That is, energy equalization is performed by using the energy of the P channels, to obtain the energy equalization side information. Alternatively, the energy equalization side information of the K channel pairs is generated based on the amplitudes of the audio signals of the P channels. That is, energy equalization is performed by using the amplitudes of the P channels, to obtain the energy equalization side information. Alternatively, the amplitude equalization side information of the K channel pairs is generated based on the amplitudes of the audio signals of the P channels. That is, amplitude equalization is performed by using the amplitudes of the P channels, to obtain the amplitude equalization side information. 
     Specifically, stereo encoding processing is performed on a channel pair in this embodiment of the present disclosure, to improve encoding efficiency and encoding effect. For example, before stereo encoding processing is performed on a current channel pair, energy/amplitude equalization may be first performed on energy/amplitudes of audio signals of two channels of the current channel pair, to obtain energy/amplitudes of audio signals of the two channels after energy/amplitude equalization, and then subsequent stereo encoding processing is performed based on the energy/amplitudes after energy/amplitude equalization. In an implementation, energy/amplitude equalization may be performed based on the audio signals of the two channels of the current channel pair, instead of an audio signal corresponding to a mono channel and/or a channel pair other than the current channel pair. In another implementation, energy/amplitude equalization may alternatively be performed based on an audio signal corresponding to another channel pair and/or a mono channel, in addition to the audio signals of the two channels of the current channel pair. 
     The energy/amplitude equalization side information is used by the decoder side to perform energy/amplitude de-equalization, so as to obtain a decoded signal. 
     In an implementation, the energy/amplitude equalization side information may include a fixed-point energy/amplitude scaling ratio and an energy/amplitude scaling identifier. The fixed-point energy/amplitude scaling ratio is a fixed-point value of an energy/amplitude scaling ratio coefficient, the energy/amplitude scaling ratio coefficient is obtained based on energy/an amplitude before energy/amplitude equalization and energy/an amplitude after energy/amplitude equalization, and the energy/amplitude scaling identifier is used to identify that the energy/amplitude after energy/amplitude equalization is or are increased or decreased relative to the energy/amplitude before energy/amplitude equalization. The energy/amplitude scaling ratio coefficient may be an energy/amplitude scaling ratio coefficient, and the energy/amplitude scaling ratio coefficient is between (0, 1). 
     A channel pair is used as an example. Energy/amplitude equalization side information of the channel pair may include fixed-point energy/amplitude scaling ratios and energy/amplitude scaling identifiers of the channel pair. For example, the channel pair includes a first channel and a second channel, and the fixed-point energy/amplitude scaling ratio of the channel pair includes a fixed-point energy/amplitude scaling ratio of the first channel and a fixed-point energy/amplitude scaling ratio of the second channel. The energy/amplitude scaling identifiers of the channel pair include an energy/amplitude scaling identifier of the first channel and an energy/amplitude scaling identifier of the second channel. The first channel is used as an example. The fixed-point energy/amplitude scaling ratio of the first channel is a fixed-point value of the energy/amplitude scaling ratio coefficient of the first channel. The energy/amplitude scaling ratio coefficient of the first channel is obtained based on energy/an amplitude of an audio signal of the first channel before energy/amplitude equalization and energy/an amplitude of the audio signal of the first channel after energy/amplitude equalization. The energy/amplitude scaling identifier of the first channel is obtained based on the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization and the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization. For example, the energy/amplitude scaling ratio coefficient of the first channel is a value obtained by dividing, by a larger one between the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization and the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization, a smaller one between the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization and the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization. For example, if the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization is greater than the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization, the energy/amplitude scaling ratio coefficient of the first channel is a value obtained by dividing, by the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization, the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization. When the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization is greater than the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization, the energy/amplitude scaling identifier of the first channel is 1. When the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization is less than or equal to the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization, the energy/amplitude scaling identifier of the first channel is 0. Certainly, it may be understood that, when the energy/amplitude of the audio signal of the first channel before energy/amplitude equalization is greater than the energy/amplitude of the audio signal of the first channel after energy/amplitude equalization, the energy/amplitude scaling identifier of the first channel may alternatively be set to 0. Implementation principles thereof are similar, and this embodiment of this application is not limited by the foregoing description. 
     The energy/amplitude scaling ratio coefficient in this embodiment of this application may also be referred to as a floating-point energy/amplitude scaling ratio coefficient. 
     In another implementation, the energy/amplitude equalization side information may include a fixed-point energy/amplitude scaling ratio. The fixed-point energy/amplitude scaling ratio is a fixed-point value of an energy/amplitude scaling ratio coefficient, and the energy/amplitude scaling ratio coefficient is a ratio of energy/an amplitude before energy/amplitude equalization to energy/an amplitude after energy/amplitude equalization. That is, the energy/amplitude scaling ratio coefficient is a value obtained by dividing, by the energy/amplitude after energy/amplitude equalization, the energy/amplitude before energy/amplitude equalization. When the energy/amplitude scaling ratio coefficient is less than 1, the decoder side may determine that the energy/amplitude after energy/amplitude equalization is increased relative to the energy/amplitude before energy/amplitude equalization. When the energy/amplitude scaling ratio coefficient is greater than 1, the decoder side may determine that the energy/amplitude after energy/amplitude equalization is decreased relative to the energy/amplitude before energy/amplitude equalization. Certainly, it may be understood that the energy/amplitude scaling ratio coefficient may alternatively be a value obtained by dividing, by the energy/amplitude before energy/amplitude equalization, the energy/amplitude after energy/amplitude equalization. Implementation principles thereof are similar. This embodiment of this application is not limited by the foregoing description. In this implementation, the energy/amplitude equalization side information may include no energy/amplitude scaling identifiers. 
     Step  203 : Encode the energy/amplitude equalization side information of the K channel pairs and the audio signals of the P channels to obtain an encoded bitstream. 
     The energy/amplitude equalization side information of the K channel pairs and the audio signals of the P channels are encoded to obtain the encoded bitstream. That is, the energy/amplitude equalization side information of the K channel pairs is written into the encoded bitstream. In other words, the encoded bitstream carries the energy/amplitude equalization side information of the K channel pairs, instead of energy/amplitude equalization side information of an uncoupled channel. This can reduce a quantity of bits of energy/amplitude equalization side information in the encoded bitstream. 
     In some embodiments, the encoded bitstream further carries a quantity of channel pairs in the current frame and K channel pair indexes, and the quantity of channel pairs and the K channel pair indexes are used by the decoder side to perform processing such as stereo decoding and energy/amplitude de-equalization. A channel pair index indicates two channels included in a channel pair. In other words, an implementation of step  203  is to encode the energy/amplitude equalization side information of the K channel pairs, the quantity of channel pairs, K channel pair indexes, and the audio signals of the P channels, to obtain the encoded bitstream. The quantity of channel pairs may be K. The K channel pair indexes include channel pair indexes corresponding to the K channel pairs. 
     A sequence of writing the quantity of channel pairs, the K channel pair indexes, and the energy/amplitude equalization side information of the K channel pairs into the encoded bitstream may be as follows: The quantity of channel pairs is written first, so that the decoder side first obtains the quantity of channel pairs when decoding the received bitstream. Then, the K channel pair indexes and the energy/amplitude equalization side information of the K channel pairs are written. 
     It should be further noted that the quantity of channel pairs may be 0, that is, there are no coupled channels. In this case, the quantity of channel pairs and the audio signals of the P channels are encoded to obtain the encoded bitstream. The decoder side decodes the received bitstream, and first learns that the quantity of channel pairs is 0. In this case, the decoder side may directly decode the current frame of the to-be-decoded multi-channel audio signal without performing parsing to obtain the energy/amplitude equalization side information. 
     Before the encoded bitstream is obtained, energy/amplitude equalization may be further performed on coefficients in the current frame of the channel based on fixed-point energy/amplitude scaling ratio and the energy/amplitude scaling identifier of the channel. 
     In this embodiment, the P channels of the current frame of the multi-channel audio signal are obtained, where the P channels include the K channel pairs; the energy/amplitude equalization side information of the K channel pairs is generated based on the energy/amplitudes of the audio signals of the P channels; and the audio signals of the P channels are encoded based on the energy/amplitude equalization side information of the K channel pairs, to obtain the encoded bitstream. The energy/amplitude equalization side information of the channel pairs is generated, and the encoded bitstream carries the energy/amplitude equalization side information of the K channel pairs without carrying energy/amplitude equalization side information of an uncoupled channel. This can reduce a quantity of bits of energy/amplitude equalization side information in the encoded bitstream and a quantity of bits of multi-channel side information. In addition, saved bits can be allocated to another functional module of an encoder, so as to improve quality of a reconstructed audio signal of the decoder side and improve coding quality. 
       FIG.  3    is a flowchart of a multi-channel audio signal encoding method according to an embodiment of this application. This embodiment of this application may be performed by the foregoing encoder. This embodiment is a specific implementation of the method in the embodiment shown in  FIG.  2   . As shown in  FIG.  3   , the method in this embodiment may include the following steps. 
     Step  301 : Obtain audio signals of P channels in a current frame of a multi-channel audio signal. 
     Step  302 : Perform multi-channel signal screening and coupling on the P channels in the current frame of the multi-channel audio signal, to determine K channel pairs and K channel pair indexes. 
     For specific implementations of screening and coupling, refer to the explanation and description of step  201  in the embodiment shown in  FIG.  2   . 
     A channel pair index indicates two channels included in a channel pair. Different values of the channel pair index correspond to two different channel pairs. A correspondence between a value of a channel pair index and two channels may be preset. 
     Signals of 5.1 channels are used as an example. For example, an L channel and an R channel are coupled through filtering and coupling, to form a first channel pair. An LS channel and an RS channel are coupled to form a second channel pair. An LFE channel and a C channel are uncoupled channels. That is, K=2. A first channel pair index indicates that the L channel and the R channel are coupled. For example, a value of the first channel pair index is 0. A second channel pair index indicates that the LS channel and the RS channel are coupled. For example, a value of the second channel pair index is 9. 
     Step  303 : Perform energy/amplitude equalization processing on respective audio signals of the K channel pairs, to obtain respective audio signals of the K channel pairs after energy/amplitude equalization and respective energy/amplitude equalization side information of the K channel pairs. 
     Energy/amplitude equalization processing of a channel pair is used as an example. In an implementation, energy/amplitude equalization processing is performed at a granularity of a channel pair: Respective energy/amplitudes of audio signals of two channels of the channel pair after energy/amplitude equalization is or are determined based on respective energy/amplitudes of the audio signals of the two channels of the channel pair before energy/amplitude equalization. Energy/amplitude equalization side information of the current channel pair is generated based on the respective energy/amplitudes of the audio signals of the two channels of the channel pair before energy/amplitude equalization and the respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization, and audio signals of the two channels after energy/amplitude equalization are obtained. 
     For determining the respective energy/amplitudes of the audio signals of the two channels of the channel pair after energy/amplitude equalization, the following manner may be used: determining an average energy/amplitude value of the audio signals of the channel pair based on the respective energy/amplitudes of the audio signals of the two channels of the channel pair before energy/amplitude equalization, and determining, based on the average energy/amplitude value of the audio signals of the channel pair, the respective energy/amplitudes of the audio signals of the two channels of the channel pair after energy/amplitude equalization. For example, the respective energy/amplitudes of the audio signals of the two channels of the channel pair after energy/amplitude equalization is or are equal, and each are the average energy/amplitude value of the audio signals of the channel pair. 
     As described above, a channel pair may include a first channel and a second channel, and energy/amplitude equalization side information of the channel pair includes a fixed-point energy/amplitude scaling ratio of the first channel, a fixed-point energy/amplitude scaling ratio of the second channel, an energy/amplitude scaling identifier of the first channel, and an energy/amplitude scaling identifier of the second channel. 
     In some embodiments, an energy/amplitude scaling ratio coefficient of a q th  channel of the channel pair may be determined based on energy/an amplitude of an audio signal of the q th  channel before energy/amplitude equalization and energy/an amplitude of the audio signal of the q th  channel after energy/amplitude equalization. A fixed-point energy/amplitude scaling ratio of the q th  channel is determined based on the energy/amplitude scaling ratio coefficient of the q th  channel. An energy/amplitude scaling identifier of the q th  channel is determined based on the energy/amplitude of the audio signal of the q th  channel before energy/amplitude equalization and the energy/amplitude of the audio signal of the q th  channel after energy/amplitude equalization. q is 1 or 2. 
     For example, a fixed-point energy/amplitude scaling ratio of a q th  channel of a channel pair and an energy/amplitude scaling identifier of the q th  channel may be determined according to the following formulas (1) to (3). 
     The fixed-point energy/amplitude scaling ratio of the q th  channel is calculated according to formulas (1) and (2). 
       scaleInt_ q =ceil((1&lt;&lt; M )×scale F _ q )   (1)
 
       scaleInt_ q =clip(scaleInt_ q, 1,2 M −1)   (2)
 
     scaleInt_q is the fixed-point energy/amplitude scaling ratio of the q th  channel, scaleF_q is a floating-point energy/amplitude scaling ratio of the q th  channel, M is a fixed-point quantity of bits for change from the floating-point energy/amplitude scaling ratio coefficient to the fixed-point energy/amplitude scaling ratio, a function clip(x, a, b) is a bidirectional clip function that clips x between [a, b], clip((x), (a), (b))=max(a, min(b, (x))), a≤b, and ceil(x) is a function that rounds up x. M may be any integer, for example, M is 4. 
     When energy_q is greater than energy_q e , energyBigFlag_q is set to 1; or when energy_q is less than or equal to energy_q e , energyBigFlag_q is set to 0. 
     energy_q is the energy/amplitude of the audio signal of the q th  channel before energy/amplitude equalization, energy_q e  is the energy/amplitude of the audio signal of the q th  channel after energy/amplitude equalization, and energyBigFlag_q is the energy/amplitude scaling identifier of the q th  channel. energy_q e  may be an average energy/amplitude value of the two channels of the channel pair. 
     A manner of determining scaleF_q in the foregoing formula (1) is: When energy_q is greater than energy_q e , scaleF_q is equal to energy_q e /energy_q; or when energy_q is less than or equal to energy_q e , scaleF_q is equal to energy_q/energy_q e . 
     energy_q is the energy/amplitude of the audio signal of the q th  channel before energy/amplitude equalization, energy_q e  is the energy/amplitude of the audio signal of the q th  channel after energy/amplitude equalization, and scaleF_q is the floating-point energy/amplitude scaling ratio coefficient of the q th  channel. 
     energy_q is determined according to the following formula (3): 
       energy_ q =(Σ i=1   N sampleCoef( q,i )×sample_Coef( q,i )) 1/2    (3)
 
     sample_Coef (q, i) represents an i th  coefficient of an audio signal of the q th  channel in a current frame before energy/amplitude equalization, and N is a quantity of frequency domain coefficients of the current frame. 
     In an energy/amplitude equalization processing procedure, energy/amplitude equalization may be performed on the audio signal of the q th  channel in the current frame based on the fixed-point energy/amplitude scaling ratio of the q th  channel and the energy/amplitude scaling identifier of the q th  channel, to obtain an audio signal of the q th  channel after energy/amplitude equalization. 
     For example, if energyBigFlag_q is 1, q e (i)=q(i)×scaleInt_q/(1&lt;&lt;M); or when energyBigFlag_q is 0, q e (i)=q(i)×(1&lt;&lt;M)/scaleInt_q. 
     i is used to identify a coefficient of the current frame, q(i) is an i th  frequency domain coefficient of a q th  channel of a current frame before energy/amplitude equalization, and q e (i) is an i th  frequency domain coefficient of a q th  channel of a current frame after energy/amplitude equalization, M is a quantity of fixed-pointed bits for change from the floating-point energy/amplitude scaling ratio coefficient to the fixed-point energy/amplitude scaling ratio coefficient. 
     In another implementation, energy/amplitude equalization processing is performed at a granularity of all channels, all channel pairs, or a part of channels in all channels. For example, an average energy/amplitude value of the audio signals of the P channels is determined based on respective energy/amplitudes of the audio signals of the P channels before energy/amplitude equalization, and respective energy or amplitudes of audio signals of two channels of a channel pair after energy/amplitude equalization is determined based on the average energy/amplitude value of the audio signals of the P channels. For example, the average energy/amplitude value of the audio signals of the P channels may be used as energy or an amplitude of an audio signal of any channel in a channel pair after energy/amplitude equalization. That is, a manner of determining the energy or the amplitude after energy/amplitude equalization is different from that in the foregoing possible implementation, and a manner of determining energy/amplitude equalization side information may be the same as that in the foregoing possible implementation. For specific implementations of the manners, refer to the foregoing description. Details are not described herein again. 
     In the foregoing embodiment, the energy/amplitude equalization side information of the current channel pair includes the fixed-point energy/amplitude scaling ratio and the energy/amplitude scaling identifier of the first channel, and the fixed-point energy/amplitude scaling ratio and the energy/amplitude scaling identifier of the second channel. That is, for a current channel (the first channel or the second channel), the side information includes both the fixed-point energy/amplitude scaling ratio and the energy/amplitude scaling identifier. This is caused by the following reason: Because the energy/amplitude scaling ratio is obtained as a ratio of a larger one between energy/an amplitude of an audio signal of the current channel before energy/amplitude equalization and energy/an amplitude of an audio signal of the current channel after energy/amplitude equalization to a smaller one, or a ratio of a smaller one to a larger one, the obtained energy/amplitude scaling ratio is fixedly greater than or equal to 1 or the obtained energy/amplitude scaling ratio is fixedly less than or equal to 1. As a result, whether the energy/amplitude of the audio signal after energy/amplitude equalization is greater than the energy/amplitude of the audio signal before energy/amplitude equalization cannot be determined by using only the energy/amplitude scaling ratio or the fixed-point energy/amplitude scaling ratio, and therefore an energy/amplitude scaling identifier is required for indication. 
     In another embodiment of this aspect, the energy/amplitude of the audio signal of the current channel before energy/amplitude equalization and the energy/amplitude of the audio signal of the current channel after energy/amplitude equalization may be fixedly used. Alternatively, the energy/amplitude of the current channel after energy/amplitude equalization and the energy/amplitude of the current channel before energy/amplitude equalization are fixedly used. In this case, the energy/amplitude scaling identifier does not need to be used for indication. Correspondingly, the side information of the current channel may include a fixed-point energy/amplitude scaling ratio, but does not need to include an energy/amplitude scaling identifier. 
     Step  304 : Perform stereo processing on respective audio signals of the K channel pairs after energy/amplitude equalization, to obtain respective stereo processed audio signals of the K channel pairs and respective stereo side information of the K channel pairs. 
     A channel pair is used as an example. Stereo processing is performed on audio signals of two channels of the channel pair after energy/amplitude equalization, to obtain stereo processed audio signals of the two channels and generate stereo side information of the channel pair. 
     Step  305 : Encode the stereo processed audio signals of the K channel pairs, energy/amplitude equalization side information of the K channel pairs, stereo side information of the K channel pairs, K, the K channel pair indexes, and an audio signal of an uncoupled channel, to obtain an encoded bitstream. 
     The stereo processed audio signals of the K channel pairs, the energy/amplitude equalization side information of the K channel pairs, the stereo side information of the K channel pairs, a quantity (K) of channel pairs, the K channel pair indexes, and the audio signal of the uncoupled channel are encoded to obtain the encoded bitstream for a decoder side to perform decoding to obtain a reconstructed audio signal. 
     In this embodiment, the audio signals of the P channels in the current frame of the multi-channel audio signal are obtained, multi-channel signal screening and coupling are performed on the P channels in the current frame of the multi-channel audio signal to determine the K channel pairs and the K channel pair indexes, energy/amplitude equalization processing is performed on the respective audio signals of the K channel pairs to obtain the respective audio signals of the K channel pairs after energy/amplitude equalization and the respective energy/amplitude equalization side information of the K channel pairs, stereo processing is performed on the respective audio signals of the K channel pairs after energy/amplitude equalization to obtain the respective stereo processed audio signals of the K channel pairs and the respective stereo side information of the K channel pairs, and the stereo processed audio signals of the K channel pairs, the energy/amplitude equalization side information of the K channel pairs, the stereo side information of the K channel pairs, K, the K channel pair indexes, and the audio signal of the uncoupled channel are encoded to obtain the encoded bitstream. The energy/amplitude equalization side information of the channel pairs is generated, and the encoded bitstream carries the energy/amplitude equalization side information of the K channel pairs without carrying energy/amplitude equalization side information of an uncoupled channel. This can reduce a quantity of bits of energy/amplitude equalization side information in the encoded bitstream and a quantity of bits of multi-channel side information. In addition, saved bits can be allocated to another functional module of an encoder, so as to improve quality of the reconstructed audio signal of the decoder side and improve coding quality. 
     Signals of 5.1 channels are used as an example in the following embodiment to describe a multi-channel audio signal encoding method in this embodiment of this application. 
       FIG.  4    is a schematic diagram of a processing procedure of an encoder side according to an embodiment of this application. As shown in  FIG.  4   , the encoder side may include a multi-channel encoding processing unit  401 , a channel encoding unit  402 , and a bitstream multiplexing interface  403 . The encoder side may be the encoder described above. 
     The multi-channel encoding processing unit  401  is configured to: perform multi-channel signal screening, coupling, and stereo processing on an input signal; and generate energy/amplitude equalization side information and stereo side information. In this embodiment, the input signal is signals of 5.1 channels (an L channel, an R channel, a C channel, an LFE channel, an LS channel, and an RS channel) 
     In an example, the multi-channel encoding processing unit  401  couples the L channel signal and the R channel signal to form a first channel pair, and performs stereo processing to obtain a middle channel M 1  channel signal and a side channel S 1  channel signal. The LS channel signal and the RS channel signal are coupled to form a second channel pair, and stereo processing is performed to obtain a middle channel M 2  channel signal and a side channel S 2  channel signal. For specific description of the multi-channel encoding processing unit  401 , refer to the embodiment shown in  FIG.  5   . 
     The multi-channel encoding processing unit  401  outputs a stereo processed M 1  channel signal, a stereo processed S 1  channel signal, a stereo processed M 2  channel signal, a stereo processed S 2  channel signal, energy/amplitude equalization side information, stereo side information, channel pair indexes, and the LFE channel signal and the C channel signal that have not undergone stereo processing. 
     The channel encoding unit  402  is configured to encode the stereo processed M 1  channel signal, the stereo processed S 1  channel signal, the stereo processed M 2  channel signal, the stereo processed S 2  channel signal, multi-channel side information, and the LFE channel signal and the C channel signal that have not undergone stereo processing, to output encoded channels E 1  to E 6 . The multi-channel side information may include the energy/amplitude equalization side information, the stereo side information, and the channel pair indexes. Certainly, it may be understood that the multi-channel side information may further include bit allocation side information, entropy encoded side information, and the like. This is not specifically limited in this embodiment of this application. The channel encoding unit  402  sends the encoded channels E 1  to E 6  to the bitstream multiplexing interface  403 . 
     The bitstream multiplexing interface  403  multiplexes the six encoded channels E 1  to E 6  to form a serial bitstream (bitStream), that is, an encoded bitstream, to facilitate transmission of a multi-channel audio signal on a channel or storage of a multi-channel audio signal in a digital medium. 
       FIG.  5    is a schematic diagram of a processing procedure of a multi-channel encoding processing unit according to an embodiment of this application. As shown in  FIG.  5   , the multi-channel encoding processing unit  401  may include a multi-channel screening unit  4011  and an iterative processing unit  4012 . The iterative processing unit  4012  may include a coupling determining unit  40121 , a channel pair energy/amplitude equalization unit  40122 , a channel pair energy/amplitude equalization unit  40123 , a stereo processing unit  40124 , and a stereo processing unit  40125 . 
     The multi-channel screening unit  4011  obtains, through screening from 5.1 input channels (an L channel, an R channel, a C channel, an LS channel, an RS channel, and an LFE channel) based on a multi-channel processing indicator (MultiProcFlag), channels participating in multi-channel processing: the L channel, the R channel, the C channel, the LS channel, and the RS channel. 
     The coupling determining unit  40121  in the iterative processing unit  4012  calculates an inter-channel correlation value between each pair of channels in the L channel, the R channel, the C channel, the LS channel, and the RS channel in a first iterative step. In the first iterative step, a channel pair (the L channel, the R channel) with highest inter-channel correlation values is selected from the channels (the L channel, the R channel, the C channel, the LS channel, and the RS channel) to form a first channel pair. The channel pair energy/amplitude equalization unit  40122  performs energy/amplitude equalization on audio signals of the L channel and the R channel, to obtain audio signals of an L e  channel and an R e  channel. The stereo processing unit  40124  performs stereo processing on the L e  channel and the R e  channel, to obtain side information of the first channel pair, and a middle channel M 1  and a side channel S 1  that are stereo processed. The side information of the first channel pair includes energy/amplitude equalization side information, stereo side information, and channel indexes of the first channel pair. In a second iterative step, a channel pair (the LS channel, the RS channel) with highest inter-channel correlation values is selected from channels (the C channel, the LS channel, and the RS channel) to form a second channel pair. The energy/amplitude equalization unit  40123  performs energy/amplitude equalization on the LS channel and the RS channel, to obtain an LS e  channel and an RS e  channel. The stereo processing unit  40125  performs stereo processing on the LS e  channel and the RS e  channel, to obtain side information of the second channel pair, and a middle channel M 2  and a side channel S 2  that are stereo processed. The side information of the second channel pair includes energy/amplitude equalization side information, stereo side information, and channel pair indexes of the second channel pair. The side information of the first channel pair and the side information of the second channel pair constitute multi-channel side information. 
     The channel pair energy/amplitude equalization unit  40122  and the channel pair energy/amplitude equalization unit  40123  each average energy/amplitudes of an input channel pair to obtain equalized energy/an equalized amplitude. 
     For example, the channel pair energy/amplitude equalization unit  40122  may determine equalized energy/an equalized amplitude according to the following formula (4): 
       energy_avg_pair1=avg(energy_ L ,energy_ R )   (4)
 
     A function avg(a 1 , a 2 ) is used to output an average value of two parameters a 1  and az. energy_L is frame energy/a frame amplitude of the L channel before energy/amplitude equalization, energy_R is frame energy/a frame amplitude of the R channel before energy/amplitude equalization, and energy_avg_pair1 is frame energy/a frame amplitude of the first channel pair after energy/amplitude equalization. 
     energy_L and energy_R may be determined according to the foregoing formula (3). 
     The channel pair energy/amplitude equalization unit  40123  may determine equalized energy/an equalized amplitude according to the following formula (4): 
       energy_avg_pair2=avg(energy_ LS ,energy_ RS )   (5)
 
     A function avg(a 1 , a 2 ) is used to output an average value of two parameters a 1  and a 2 . energy_LS is frame energy/a frame amplitude of the LS channel before energy/amplitude equalization, energy_RS is frame energy/a frame amplitude of the RS channel before energy/amplitude equalization, and energy_avg_pair2 is energy/an amplitude of the second channel pair after energy/amplitude equalization. 
     In addition, the energy/amplitude equalization side information of the first channel pair and the energy/amplitude equalization side information of the second channel pair in the foregoing embodiment are generated in an energy/amplitude equalization process. The energy/amplitude equalization side information of the first channel pair and the energy/amplitude equalization side information of the second channel pair are in the encoded bitstream for transmission, to indicate energy/amplitude de-equalization of a decoder side. 
     A manner of determining the energy/amplitude equalization side information of the first channel pair is described. 
     S 01 : Calculate the energy/amplitude energy_avg_pair1, equalized by the channel pair energy/amplitude equalization unit  40122 , of the first channel pair. energy_avg_pair1 is determined according to the foregoing formula (4). 
     S 02 : Calculate a floating-point energy/amplitude scaling ratio coefficient of the L channel of the first channel pair. 
     In an example, the floating-point energy/amplitude scaling ratio coefficient of the L channel is scaleF_L. The floating-point energy/amplitude scaling ratio coefficient is between (0, 1). If energy_L&gt;energy_L e , scaleF_L=energy_L e /energy_L; or if energy_L≤energy_L e , scaleF_L=energy_L/energy_L e . 
     energy_L e  is equal to energy_avg_pair1. 
     S 03 : Calculate a fixed-point energy/amplitude scaling ratio of the L channel of the first channel pair. 
     In an example, the fixed-point energy/amplitude scaling ratio of the L channel is scaleInt_L. A fixed-point quantity of bits from the floating-point energy/amplitude scaling ratio coefficient scaleF_L to the fixed-point energy/amplitude scaling ratio scaleInt_L is a fixed value. The fixed-point quantity of bits determines precision of conversion from a floating point to a fixed point, and transmission efficiency also needs to be considered (because the side information occupies bits). Herein, it is assumed that the fixed-point quantity of bits is 4 (that is, M=4). In this case, a formula for calculating the fixed-point energy/amplitude scaling ratio of the L channel is as follows: 
       scaleInt_ L =ceil((1&lt;&lt;4)×scale F _ L )
 
       scaleInt_ L =clip(scaleInt_ L, 1,15) 
     clip((x), (a), (b))=max(a, min(b, (x))), a≤b. A function ceil(x) is a function that rounds up x. A function clip(x, a, b) is a bidirectional clip function that clips x between [a, b]. 
     S 04 : Calculate an energy/amplitude scaling identifier of the L channel of the first channel pair. 
     In an example, the energy/amplitude scaling identifier of the L channel is energyBigFlag_L. If energy_L is greater than energy_L e , energyBigFlag_L is set to 1; or if energy_L is less than or equal to energy_L e , energyBigFlag_L is set to 0. 
     Details about performing energy/amplitude equalization on each coefficient in the L channel in a current frame are as follows: 
     If energyBigFlag_L is 1, L e (i)=L(i)×scaleInt_L/(1&lt;&lt;4). i is used to identify a coefficient of the current frame, L(i) is an frequency domain coefficient of the current frame before energy/amplitude equalization, and L e (i) is an i th  frequency domain coefficient of the current frame after energy/amplitude equalization. If energyBigFlag_L is 0, L e (i)=L(i)×(1&lt;&lt;4)/scaleInt_L. 
     Similar operations S 01  to S 04  may be performed on the R channel of the first channel pair, to obtain a floating-point energy/amplitude scaling ratio coefficient scaleF_R, a fixed-point energy/amplitude scaling ratio scaleInt_R, and an energy/amplitude scaling identifier energyBigFlag_R of the R channel, and a current frame R e  after energy/amplitude equalization. That is, L in S 01  to S 04  is replaced by R. 
     Similar operations S 01  to S 04  may be performed on the LS channel of the second channel pair, to obtain a floating-point energy/amplitude scaling ratio coefficient scaleF_LS, a fixed-point energy/amplitude scaling ratio scaleInt_LS, an energy/amplitude scaling identifier energyBigFlag_LS of the LS channel, and a current frame LS e  after energy/amplitude equalization. That is, L in S 01  to S 04  is replaced by LS. 
     Similar operations S 01  to S 04  are performed on the RS channel of the second channel pair, to obtain a floating-point energy/amplitude scaling ratio coefficient scaleF_RS, a fixed-point energy/amplitude scaling ratio scaleInt_RS, and an energy/amplitude scaling identifier energyBigFlag_RS of the RS channel, and a current frame RS e  after energy/amplitude equalization. 
     Multi-channel side information is written into an encoded bitstream. The multi-channel side information includes a quantity of channel pairs, the energy/amplitude equalization side information of the first channel pair, a first channel pair index, energy/amplitude equalization side information of the second channel pair, and a second channel pair index. 
     For example, the quantity of channel pairs is currPairCnt, the energy/amplitude equalization side information of the first channel pair and the energy/amplitude equalization side information of the second channel pair are a two-dimensional array, and the first channel pair index and the second channel pair index are a one-dimensional array. For example, fixed-point energy/amplitude scaling ratios of the first channel pair are PairILDScale[0][0] and PairILDScale[0][1], energy/amplitude scaling identifiers of the first channel pair are energyBigFlag[0][0] and energyBigFlag[0][1], fixed-point energy/amplitude scaling ratios of the second channel pair are PairILDScale[1][0] and PairILDScale[1][1], and energy/amplitude scaling identifiers of the second channel pair are energyBigFlag[1][0] and energyBigFlag[1][1]. The first channel pair index is PairIndex[0], and the second channel pair index is PairIndex[1]. 
     The quantity of channel pairs currPairCnt may be of a fixed bit length, for example, 4 bits, and may identify a maximum of 16 stereo pairs. 
     Table 1 shows definitions of values of channel pair indexes PairIndex[pair]. A channel pair index may be length-variable code, is used for transmission in an encoded bitstream, so as to save bits, and is used to restore an audio signal of the decoder side. For example, if PairIndex[0]=0, it indicates that a channel pair includes an R channel and an L channel. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Channel pair index mapping table of 5 channels 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 0(L) 
                 1(R) 
                 2(C) 
                 3(LS) 
                 4(RS) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 0(L) 
                 0 
                 1 
                 3 
                 6 
               
               
                   
                 1(R) 
                   
                 2 
                 4 
                 7 
               
               
                   
                 2(C) 
                   
                   
                 5 
                 8 
               
               
                   
                 3(LS) 
                   
                   
                   
                 9 
               
               
                   
                 4(RS) 
               
               
                   
               
            
           
         
       
     
     In this embodiment, PairILDScale[0][0]=scaleInt_L. PairILDScale[0][1]=scaleInt_R. 
     PairILDScale[1][0]=scaleInt_LS. PairILDScale[1][1]=scaleInt_RS. 
     energyBigFlag[0][0]=energyBigFlag_L. energyBigFlag[0][1]=energyBigFlag_R. 
     energyBigFlag[1][0]=energyBigFlag_LS. energyBigFlag[1][1]=energyBigFlag_RS. 
     PairIndex[0]=0 (L and R). PairIndex[1]=9 (LS and RS). 
     For example,  FIG.  6    shows a procedure of writing multi-channel side information into a bitstream. Step  601 : Set a variable pair to 0, and write a quantity of channel pairs into the bitstream. For example, the quantity of channel pairs currPairCnt may be of 4 bits. Step  602 : Determine whether pair is less than the quantity of channel pairs; and if pair is less than the quantity of channel pairs, perform step  603 ; or if pair is greater than or equal to the quantity of channel pairs, the procedure ends. Step  603 : Write an index of an i th  channel pair into the bitstream. i=pair+1. For example, PairIndex[0] is written into the bitstream. Step  604 : Write fixed-point energy/amplitude scaling ratios of the i th  channel pair into the bitstream. For example, PairILDScale[0][0] and PairILDScale[0][1] are written into the bitstream. PairILDScale[0][0] and PairILDScale[0][1] each may occupy four bits. Step  605 : Write energy/amplitude scaling identifiers of the i th  channel pair into the bitstream. For example, energyBigFlag[0][0] and energyBigFlag[0][1] are written into the bitstream. energyBigFlag[0][0] and energyBigFlag[0][1] each may occupy one bit. Step  606 : Write stereo side information of the i th  channel pair into the bitstream, set pair=pair+1, and return to step  602 . After step  602  is returned, PairIndex[1], PairILDScale[1][0], PairILDScale[1][1], energyBigFlag[1][0], and energyBigFlag[1][1] are written into the bitstream until the procedure ends. 
       FIG.  7    is a flowchart of a multi-channel audio signal decoding method according to an embodiment of this application. This embodiment of this application may be performed by the foregoing decoder. As shown in  FIG.  7   , the method in this embodiment may include the following steps. 
     Step  701 : Obtain a to-be-decoded bitstream. 
     The to-be-decoded bitstream may be the encoded bitstream obtained in the foregoing encoding method embodiment. 
     Step  702 : Demultiplex the to-be-decoded bitstream to obtain a current frame of a to-be-decoded multi-channel audio signal and a quantity of channel pairs included in the current frame. 
     Signals of 5.1 channels are used as an example. The to-be-decoded bitstream is demultiplexed to obtain an M 1  channel signal, an S 1  channel signal, an M 2  channel signal, an S 2  channel signal, an LFE channel signal, a C channel signal, and a quantity of channel pairs. 
     Step  703 : Determine whether the quantity of channel pairs is equal to 0; and if the quantity of channel pairs is equal to 0, perform step  704 ; or if the quantity of channel pairs is not equal to 0, perform step  705 . 
     Step  704 : Decode the current frame of the to-be-decoded multi-channel audio signal to obtain decoded signals of the current frame. 
     When the quantity of channel pairs is equal to 0, that is, no channels are coupled, the current frame of the to-be-decoded multi-channel audio signal may be decoded to obtain the decoded signals of the current frame. 
     Step  705 : Parse the current frame to obtain K channel pair indexes included in the current frame and energy/amplitude equalization side information of the K channel pairs. 
     When the quantity of channel pairs is equal to K, the current frame may be further parsed to obtain other control information, for example, K channel pair indexes and energy/amplitude equalization side information of the K channel pairs in the current frame, so that energy/amplitude de-equalization is performed on the current frame of the to-be-decoded multi-channel audio signal in a subsequent decoding process to obtain the decoded signals of the current frame. 
     Step  706 : Decode the current frame of the to-be-decoded multi-channel audio signal based on the K channel pair indexes and the energy/amplitude equalization side information of the K channel pairs, to obtain decoded signals of the current frame. 
     Signals of 5.1 channels are used as an example. The M 1  channel signal, the S 1  channel signal, the M 2  channel signal, the S 2  channel signal, the LFE channel signal, and the C channel signal are decoded to obtain an L channel signal, an R channel signal, an LS channel signal, an RS channel signal, the LFE channel signal, and a C channel signal. In a decoding process, energy/amplitude de-equalization is performed based on the energy/amplitude equalization side information of the K channel pairs. 
     In some embodiments, energy/amplitude equalization side information of a channel pair may include fixed-point energy/amplitude scaling ratios and energy/amplitude scaling identifiers of the channel pair. For specific explanation thereof, refer to explanation in the foregoing encoding embodiment. Details are not described herein again. 
     In this embodiment, the to-be-decoded bitstream is demultiplexed to obtain the current frame of the to-be-decoded multi-channel audio signal and the quantity of channel pairs included in the current frame. When the quantity of channel pairs is greater than 0, the current frame is further parsed to obtain the K channel pair indexes and energy/amplitude equalization side information of the K channel pairs, and the current frame of the to-be-decoded multi-channel audio signal is decoded based on the K channel pair indexes and the energy/amplitude equalization side information of the K channel pairs to obtain the decoded signals of the current frame. A quantity of bits of energy/amplitude equalization side information in the encoded bitstream sent by an encoder side and a quantity of bits of multi-channel side information can be reduced because the bitstream does not carry energy/amplitude equalization side information of an uncoupled channel. In this way, saved bits can be allocated to another functional module of the encoder, so as to improve quality of a reconstructed audio signal of a decoder side. 
     Signals of 5.1 channels are used as an example in the following embodiment to describe a multi-channel audio signal decoding method in this embodiment of this application. 
       FIG.  8    is a schematic diagram of a processing procedure of a decoder side according to an embodiment of this application. As shown in  FIG.  8   , the decoder side may include a bitstream demultiplexing interface  801 , a channel decoding unit  802 , and a multi-channel decoding processing unit  803 . A decoding process in this embodiment is an inverse process of the encoding process in the embodiments shown in  FIG.  4    and  FIG.  5   . 
     The bitstream demultiplexing interface  801  is configured to demultiplex a bitstream output by an encoder side, to obtain six encoded channels E 1  to E 6 . 
     The channel decoding unit  802  is configured to perform inverse entropy encoding and inverse quantization on the encoded channels E 1  to E 6  to obtain a multi-channel signal, including: a middle channel M 1  and a side channel S 1  of the first channel pair, a middle channel M 2  and a side channel S 2  of the second channel pair, and a C channel and an LFE channel that are not coupled. The channel decoding unit  802  also performs decoding to obtain multi-channel side information. The multi-channel side information includes side information (for example, entropy encoded side information) generated in the channel encoding processing procedure in the embodiment shown in  FIG.  4   , and side information generated in the multi-channel encoding processing procedure (for example, energy/amplitude equalization side information of the channel pair). 
     The multi-channel decoding processing unit  803  performs multi-channel decoding processing on the middle channel M 1  and the side channel S 1  of the first channel pair and the middle channel M 2  and the side channel S 2  of the second channel pair. The multi-channel side information is used to: decode the middle channel M 1  and the side channel S 1  of the first channel pair into an L channel and an R channel, and decode the middle channel M 2  and the side channel S 2  of the second channel pair into an LS channel and an RS channel. The L channel, the R channel, the LS channel, the RS channel, and the uncoupled C channel and LFE channel constitute an output of the decoder side. 
       FIG.  9    is a schematic diagram of a processing procedure of a multi-channel decoding processing unit according to an embodiment of this application. As shown in  FIG.  9   , the multi-channel decoding processing unit  803  may include a multi-channel screening unit  8031  and a multi-channel decoding processing submodule  8032 . The multi-channel decoding processing submodule  8032  includes two stereo decoding boxes, an energy/amplitude de-equalization unit  8033 , and an energy/amplitude de-equalization unit  8034 . 
     The multi-channel screening unit  8031  obtains, through screening from 5.1 input channels (an M 1  channel, an S 1  channel, a C channel, an M 2  channel, an S 2  channel, and an LFE channel) based on a quantity of channel pairs and channel pair indexes in multi-channel side information, the M 1  channel, the S 1  channel, the M 2  channel, and the S 2  channel that participate in multi-channel processing. 
     A stereo decoding box of the multi-channel decoding processing submodule  8032  is configured to perform the following steps: indicating, based on stereo side information of a first channel pair, that a stereo decoding box decodes the first channel pair (M 1 , S 1 ) into an L e  channel and an R e  channel; and indicating, based on stereo side information of a second channel pair, that a stereo decoding box decodes the second channel pair (M 2 , S 2 ) into an LS e  channel and an RS e  channel. 
     The energy/amplitude de-equalization unit  8033  is configured to perform the following step: indicating, based on energy/amplitude side information of the first channel pair, that the energy/amplitude de-equalization unit de-equalizes energy/an amplitude of the L e  channel and the R e  channel for restoration into an L channel and an R channel. The energy/amplitude de-equalization unit  8034  is configured to perform the following step: indicating, based on energy/amplitude equalization side information of the second channel pair, that a first channel pair de-equalization unit de-equalizes energy/an amplitude of the LS e  channel and the RS e  channel for restoration an LS channel and an RS channel. 
     A multi-channel side information decoding process is described.  FIG.  10    is a flowchart of parsing multi-channel side information according to an embodiment of this application. This embodiment is an inverse process of the embodiment shown in  FIG.  6   . As shown in  FIG.  10   , the method includes the following steps. Step  701 : Parse a bitstream to obtain a quantity of channel pairs in a current frame, for example, a quantity of channel pairs currPairCnt, where the quantity of channel pairs currPairCnt occupies four bits in the bitstream. Step  702 : Determine whether the quantity of channel pairs in the current frame is 0; and if the quantity of channel pairs in the current frame is 0, the parsing process ends; or if the quantity of channel pairs in the current frame is not 0, perform step  703 , where if the quantity of channel pairs currPairCnt in the current frame is 0, it indicates that no coupling is performed in the current frame; in this case, there is no need to obtain energy/amplitude equalization side information through parsing; or if the quantity of channel pairs currPairCnt in the current frame is not 0, cyclic parsing is performed for energy/amplitude equalization side information of the first channel pair, . . . , and energy/amplitude equalization side information of a (currPairCnt) th  channel pair. For example, a variable pair is set to 0. In addition, subsequent steps  703  to  707  are performed. Step  703 : Determine whether pair is less than the quantity of channel pairs; and if pair is less than the quantity of channel pairs, perform step  704 ; or if pair is greater than or equal to the quantity of channel pairs, the process ends. Step  704 : Parse an index of an i th  channel pair from the bitstream, where i=pair+1. Step  705 : Parse fixed-point energy/amplitude scaling ratios of the i th  channel pair from the bitstream, for example, PairILDScale[pair][0] and PairILDScale[pair][1]. Step  706 : Parse energy/amplitude scaling identifiers of the i th  channel pair from the bitstream, for example, energyBigFlag[pair][0] and energyBigFlag[pair][1]. Step  707 : Parse stereo side information of the i th  channel pair from the bitstream, set pair=pair+1, and return to step  703  until all channel pair indexes, fixed-point energy/amplitude scaling ratios, and energy/amplitude scaling identifiers are obtained through parsing. 
     Signals of 5.1 channels (L, R, C, LFE, LS, RS) on an encoder side are used as example to describe a process of parsing side information of a first channel pair and a process of parsing side information of a second channel pair. 
     The process of parsing the side information of the first channel pair is as follows: A 4-bit channel pair index PairIndex[0] is parsed from a bitstream, and is mapped into an L channel and an R channel according to a definition rule of a channel pair index. A fixed-point energy/amplitude scaling ratio PairILDScale[0][0] of the L channel and a fixed-point energy/amplitude scaling ratio PairILDScale[0][1] of the R channel are parsed from the bitstream. An energy/amplitude scaling identifier energyBigFlag[0][0] of the L channel and an energy/amplitude scaling identifier energyBigFlag[0][1] of the R channel are parsed from the bitstream. Stereo side information of the first channel pair is parsed from the bitstream. Parsing of the side information of the first channel pair is completed. 
     The process of parsing the side information of the second channel pair is as follows: A 4-bit channel pair index PairIndex[1] is parsed from the bitstream, and is mapped into an LS channel and an RS channel according to a definition rule of a channel pair index. A fixed-point energy/amplitude scaling ratio PairILDScale[1][0] of the LS channel and a fixed-point energy/amplitude scaling ratio PairILDScale[1][1] of the RS channel are parsed from the bitstream. An energy/amplitude scaling identifier energyBigFlag[1][0] of the LS channel and an energy/amplitude scaling identifier energyBigFlag[1][1] of the RS channel are parsed from the bitstream. Stereo side information of the second channel pair is parsed from the bitstream. Parsing of the side information of the second channel pair is completed. 
     A process in which the energy/amplitude de-equalization unit  8033  is configured to de-equalize energy/an amplitude of the L e  channel and the R e  channel of the first channel pair is as follows: 
     A floating-point energy/amplitude scaling ratio coefficient scaleF_L of the L channel is calculated based on the fixed-point energy/amplitude scaling ratio PairILDScale[0][0] of the L channel and the energy/amplitude scaling identifier energyBigFlag[0][0] of the L channel. If the energy/amplitude scaling identifier energyBigFlag[0][0] of the L channel is 1, scaleF_L=(1&lt;&lt;4)/PairILDScale[0][0]; or if the energy/amplitude scaling identifier energyBigFlag[0][0] of the L channel is 0, scaleF_L=PairILDScale[0][0]/( 1  « 4 ). 
     A frequency domain coefficient of an L channel after energy/amplitude de-equalization is obtained based on the floating-point energy/amplitude scaling ratio coefficient scaleF_L of the L channel. L(i)=L e (i)×scaleF_L, where i is used to identify a coefficient of a current frame, L(i) is an i th  frequency domain coefficient of the current frame before energy/amplitude equalization, and L e (i) is an i th  frequency domain coefficient of the current frame after energy/amplitude equalization. 
     A floating-point energy/amplitude scaling ratio coefficient scaleF_R of an R channel is calculated based on the fixed-point energy/amplitude scaling ratio PairILDScale[0][1] of the R channel and the energy/amplitude scaling identifier energyBigFlag[0][1] of the R channel. If the energy/amplitude scaling identifier energyBigFlag[0][1] of the R channel is 1, scaleF_R=(1&lt;&lt;4)/PairILDScale[0][1]; or if the energy/amplitude scaling identifier energyBigFlag[0][1] of the R channel is 0, scaleF_R=PairILDScale[0][1]/(1&lt;&lt;4). 
     A frequency domain coefficient of an R channel after energy/amplitude de-equalization is obtained based on the floating-point energy/amplitude scaling ratio coefficient scaleF_R of the R channel. R(i)=R e (i)×scaleF_R, where i is used to identify a coefficient of a current frame, R(i) is an i th  frequency domain coefficient of the current frame before energy/amplitude equalization, and L e (i) is an i th  frequency domain coefficient of the current frame after energy/amplitude equalization. 
     A specific implementation in which the energy/amplitude de-equalization unit  8034  is configured to de-equalize energy/amplitudes of the LS e  channel and the RS e  channel of the second channel pair is consistent with an implementation of de-equalizing the energy/amplitudes of the L e  channel and the R e  channel of the first channel pair. Details are not described herein again. 
     An output of the multi-channel decoding processing unit  803  is a decoded L channel signal, R channel signal, LS channel signal, RS channel signal, C channel signal, and LFE channel signal. 
     In this embodiment, a quantity of bits of energy/amplitude equalization side information in the encoded bitstream sent by the encoder side and a quantity of bits of multi-channel side information can be reduced because the bitstream does not carry energy/amplitude equalization side information of an uncoupled channel. In this way, saved bits can be allocated to another functional module of the encoder, so as to improve quality of a reconstructed audio signal of a decoder side. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application further provides an audio signal encoding apparatus. The audio signal encoding apparatus may be used in an audio encoder. 
       FIG.  11    is a schematic diagram of a structure of an audio signal encoding apparatus according to an embodiment of this application. As shown in  FIG.  11   , the audio signal encoding apparatus  1100  includes an obtaining module  1101 , an equalization side information generation module  1102 , and an encoding module  1103 . 
     The obtaining module  1101  is configured to obtain audio signals of P channels in a current frame of a multi-channel audio signal and respective energy/amplitudes of the audio signals of the P channels, where P is a positive integer greater than 1, the P channels include K channel pairs, each channel pair includes two channels, K is a positive integer, and P is greater than or equal to K×2. 
     The equalization side information generation module  1102  is configured to generate energy/amplitude equalization side information of the K channel pairs based on the respective energy/amplitudes of the audio signals of the P channels. 
     The encoding module  1103  is configured to encode the energy/amplitude equalization side information of the K channel pairs and the audio signals of the P channels, to obtain an encoded bitstream. 
     In some embodiments, the K channel pairs include a current channel pair, and the energy/amplitude equalization side information of the current channel pair includes fixed-point energy/amplitude scaling ratios and energy/amplitude scaling identifiers of the current channel pair. The fixed-point energy/amplitude scaling ratio is a fixed-point value of an energy/amplitude scaling ratio coefficient, the energy/amplitude scaling ratio coefficient is obtained based on respective energy/amplitudes of audio signals of two channels of the current channel pair before energy/amplitude equalization and respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization, the energy/amplitude scaling identifier is used to identify that the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization is or are increased or decreased relative to the respective energy/amplitudes of the audio signals before energy/amplitude equalization. 
     In some embodiments, the K channel pairs include the current channel pair, and the equalization side information generation module  1102  is configured to: determine, based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair before energy/amplitude equalization, the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization; and generate the energy/amplitude equalization side information of the current channel pair based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair before energy/amplitude equalization and the respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization. 
     In some embodiments, the current channel pair includes a first channel and a second channel, and the energy/amplitude equalization side information of the current channel pair includes a fixed-point energy/amplitude scaling ratio of the first channel, a fixed-point energy/amplitude scaling ratio of the second channel, an energy/amplitude scaling identifier of the first channel, and an energy/amplitude scaling identifier of the second channel. 
     In some embodiments, the equalization side information generation module  1102  is configured to: determine an energy/amplitude scaling ratio coefficient of an audio signal of a q th  channel of the current channel pair based on energy/an amplitude of an audio signal of the q th  channel before energy/amplitude equalization and energy/an amplitude of the audio signal of the q th  channel after energy/amplitude equalization; determine a fixed-point energy/amplitude scaling ratio of the q th  channel based on the energy/amplitude scaling ratio coefficient of the q th  channel; and determine an energy/amplitude scaling identifier of the q th  channel based on the energy/amplitude of the audio signal of the q th  channel before energy/amplitude equalization and the energy/amplitude of the audio signal of the q th  channel after energy/amplitude equalization, where q is 1 or 2. 
     In some embodiments, the equalization side information generation module  1102  is configured to: determine an average energy/amplitude value of the audio signals of the current channel pair based on the respective energy/amplitudes of the audio signals of the two channels of the current channel pair before energy/amplitude equalization; and determine, based on the average energy/amplitude value of the audio signals of the current channel pair, the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization. 
     In some embodiments, the encoding module  1103  is configured to encode the energy/amplitude equalization side information of the K channel pairs, K, respective channel pair indexes of the K channel pairs, and the audio signals of the P channels, to obtain the encoded bitstream. 
     It should be noted that the obtaining module  1101 , the equalization side information generation module  1102 , and the encoding module  1103  may be used in an audio signal encoding process on an encoder side. 
     It should be further noted that, for a specific implementation process of the obtaining module  1101 , the equalization side information generation module  1102 , and the encoding module  1103 , refer to the detailed description of the encoding method in the foregoing method embodiment. For brevity of the specification, details are not described herein again. 
     Based on a same inventive idea as the foregoing method, an embodiment of this application provides an audio signal encoder. The audio signal encoder is configured to encode an audio signal, and includes, for example, the encoder described in the foregoing one or more embodiments. The audio signal encoding apparatus is configured to perform encoding to generate a corresponding bitstream. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides a device for encoding an audio signal, for example, an audio signal encoding device. As shown in  FIG.  12   , an audio signal encoding device  1200  includes: 
     a processor  1201 , a memory  1202 , and a communication interface  1203  (there may be at least one processor  1201  in the audio signal encoding device  1200 , and  FIG.  12    uses an example of one processor). In some embodiments of this application, the processor  1201 , the memory  1202 , and the communication interface  1203  may be connected through a bus or in another manner.  FIG.  12    shows an example of connection through a bus. 
     The memory  1202  may include a read-only memory and a random access memory, and provide instructions and data for the processor  1201 . A part of the memory  1202  may further include a non-volatile random access memory (NVRAM). The memory  1202  stores an operating system and operation instructions, an executable module or a data structure, or a subset thereof, or an extended set thereof. The operation instructions may include various operation instructions for performing various operations. The operating system may include various system programs, to implement various basic services and process a hardware-based task. 
     The processor  1201  controls an operation of the audio encoding device, and the processor  1201  may also be referred to as a central processing unit (CPU). In specific application, components of the audio encoding device are coupled together by using a bus system. In addition to a data bus, the bus system may further include a power bus, a control bus, a status signal bus, and the like. However, for clear description, various types of buses in the figure are marked as the bus system. 
     The method disclosed in embodiments of this application may be applied to the processor  1201 , or may be implemented by the processor  1201 . The processor  1201  may be an integrated circuit chip, and has a signal processing capability. In an implementation process, each step in the foregoing methods may be performed by using a hardware integrated logical circuit in the processor  1201  or an instruction in a form of software. The processor  1201  may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or another programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The processor  1201  may implement or perform the methods, the steps, and logical block diagrams that are disclosed in embodiments of this application. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like. The steps of the methods disclosed with reference to embodiments of this application may be directly executed and accomplished by using a hardware decoding processor, or may be executed and accomplished by using a combination of hardware and software modules in a decoding processor. A software module may be located in a storage medium mature in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an electrically erasable programmable memory, or a register. The storage medium is located in the memory  1202 , and the processor  1201  reads information in the memory  1202  and completes the steps of the foregoing method in combination with the hardware of the processor  1201 . 
     The communication interface  1203  may be configured to receive or send digit or character information, for example, may be an input/output interface, a pin, or a circuit. For example, the foregoing encoded bitstream is sent through the communication interface  1203 . 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides an audio encoding device, including a non-volatile memory and a processor that are coupled to each other. The processor invokes program code stored in the memory, to perform a part or all of the steps in the multi-channel audio signal encoding method in one or more of the foregoing embodiments. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides a computer-readable storage medium. The computer-readable storage medium stores program code, and the program code includes instructions for performing a part or all of the steps in the multi-channel audio signal encoding method in one or more of the foregoing embodiments. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides a computer program product. When the computer program product runs on a computer, the computer is enabled to perform a part or all of the steps in the multi-channel audio signal encoding method in one or more of the foregoing embodiments. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application further provides an audio signal decoding apparatus. The audio signal decoding apparatus may be used in an audio decoder. 
       FIG.  13    is a schematic diagram of a structure of an audio signal decoding apparatus according to an embodiment of this application. As shown in  FIG.  13   , the audio signal decoding apparatus  1300  includes an obtaining module  1301 , a demultiplexing module  1302 , and a decoding module  1303 . 
     The obtaining module  1301  is configured to obtain a to-be-decoded bitstream. 
     The demultiplexing module  1302  is configured to demultiplex the to-be-decoded bitstream to obtain a current frame of a to-be-decoded multi-channel audio signal, a quantity K of channel pairs included in the current frame, respective channel pair indexes of the K channel pairs, and energy/amplitude equalization side information of the K channel pairs. 
     The decoding module  1303  is configured to decode the current frame of the to-be-decoded multi-channel audio signal based on the respective channel pair indexes of the K channel pairs and the energy/amplitude equalization side information of the K channel pairs, to obtain decoded signals of the current frame, where K is a positive integer, and each channel pair includes two channels. 
     In some embodiments, the K channel pairs include a current channel pair, and the energy/amplitude equalization side information of the current channel pair includes fixed-point energy/amplitude scaling ratios and energy/amplitude scaling identifiers of the current channel pair. The fixed-point energy/amplitude scaling ratio is a fixed-point value of an energy/amplitude scaling ratio coefficient, the energy/amplitude scaling ratio coefficient is obtained based on respective energy/amplitudes of audio signals of two channels of the current channel pair before energy/amplitude equalization and respective energy/amplitudes of the audio signals of the two channels after energy/amplitude equalization, the energy/amplitude scaling identifier is used to identify that the respective energy/amplitudes of the audio signals of the two channels of the current channel pair after energy/amplitude equalization is or are increased or decreased relative to the respective energy/amplitudes of the audio signals before energy/amplitude equalization. 
     In some embodiments, the K channel pairs include the current channel pair, and the decoding module  1303  is configured to: perform stereo decoding processing on the current frame of the to-be-decoded multi-channel audio signal based on a channel pair index corresponding to the current channel pair, to obtain the audio signals of the two channels of the current channel pair of the current frame; and perform energy/amplitude de-equalization processing on the audio signals of the two channels of the current channel pair based on the energy/amplitude equalization side information of the current channel pair, to obtain decoded signals of the two channels of the current channel pair. 
     In some embodiments, the current channel pair includes a first channel and a second channel, and the energy/amplitude equalization side information of the current channel pair includes a fixed-point energy/amplitude scaling ratio of the first channel, a fixed-point energy/amplitude scaling ratio of the second channel, an energy/amplitude scaling identifier of the first channel, and an energy/amplitude scaling identifier of the second channel. 
     It should be noted that the obtaining module  1301 , the demultiplexing module  1302 , and the decoding module  1303  may be used in an audio signal decoding process on a decoder side. 
     It should be further noted that, for a specific implementation process of the obtaining module  1301 , the demultiplexing module  1302 , and the decoding module  1303 , refer to the detailed description of the decoding method in the foregoing method embodiment. For brevity of the specification, details are not described herein again. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides an audio signal decoder. The audio signal decoder is configured to decode an audio signal, and includes, for example, the decoder described in one or more of the foregoing embodiments. An audio signal decoding apparatus is configured to perform decoding to generate a corresponding bitstream. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides a device for decoding an audio signal, for example, an audio signal decoding device. As shown in  FIG.  14   , an audio signal decoding device  1400  includes: 
     a processor  1401 , a memory  1402 , and a communication interface  1403  (there may be at least one processor  1401  in the audio signal decoding device  1400 , and  FIG.  14    uses an example of one processor). In some embodiments of this application, the processor  1401 , the memory  1402 , and the communication interface  1403  may be connected through a bus or in another manner.  FIG.  14    shows an example of connection through a bus. 
     The memory  1402  may include a read-only memory and a random access memory, and provide instructions and data for the processor  1401 . A part of the memory  1402  may further include a non-volatile random access memory (NVRAM). The memory  1402  stores an operating system and operation instructions, an executable module or a data structure, or a subset thereof, or an extended set thereof. The operation instructions may include various operation instructions for performing various operations. The operating system may include various system programs, to implement various basic services and process a hardware-based task. 
     The processor  1401  controls an operation of an audio decoding device, and the processor  1401  may also be referred to as a central processing unit (CPU). In specific application, components of the audio decoding device are coupled together by using a bus system. In addition to a data bus, the bus system may further include a power bus, a control bus, a status signal bus, and the like. However, for clear description, various types of buses in the figure are marked as the bus system. 
     The method disclosed in embodiments of this application may be applied to the processor  1401 , or may be implemented by the processor  1401 . The processor  1401  may be an integrated circuit chip, and has a signal processing capability. In an implementation process, each step in the foregoing methods may be performed by using a hardware integrated logical circuit in the processor  1401  or an instruction in a form of software. The processor  1401  may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or another programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The processor  1401  may implement or perform the methods, the steps, and logical block diagrams that are disclosed in embodiments of this application. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like. The steps of the methods disclosed with reference to embodiments of this application may be directly executed and accomplished by using a hardware decoding processor, or may be executed and accomplished by using a combination of hardware and software modules in a decoding processor. A software module may be located in a storage medium mature in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an electrically erasable programmable memory, or a register. The storage medium is located in the memory  1402 , and the processor  1401  reads information in the memory  1402  and completes the steps of the foregoing method in combination with the hardware of the processor  1401 . 
     The communication interface  1403  may be configured to receive or send digit or character information, for example, may be an input/output interface, a pin, or a circuit. For example, the foregoing encoded bitstream is received through the communication interface  1403 . 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides an audio decoding device, including a non-volatile memory and a processor that are coupled to each other. The processor invokes program code stored in the memory, to perform a part or all of the steps in the multi-channel audio signal decoding method in one or more of the foregoing embodiments. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides a computer-readable storage medium. The computer-readable storage medium stores program code, and the program code includes instructions for performing a part or all of the steps in the multi-channel audio signal decoding method in one or more of the foregoing embodiments. 
     Based on the same inventive idea as the foregoing method, an embodiment of this application provides a computer program product. When the computer program product runs on a computer, the computer is enabled to perform a part or all of the steps in the multi-channel audio signal decoding method in one or more of the foregoing embodiments. 
     The processor mentioned in the foregoing embodiments may be an integrated circuit chip, and has a signal processing capability. In an implementation process, each step in the foregoing method embodiments may be performed by using a hardware integrated logical circuit in the processor or an instruction in a form of software. The processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or another programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like. The steps of the methods disclosed in embodiments of this application may be directly executed and accomplished by using a hardware encoding processor, or may be executed and accomplished by a combination of hardware and a software module in an encoding processor. A software module may be located in a storage medium mature in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an electrically erasable programmable memory, or a register. The storage medium is located in the memory, and the processor reads information in the memory and completes the steps of the foregoing method in combination with the hardware of the processor. 
     The memory in the foregoing embodiments may be a volatile memory or a non-volatile memory, or may include both a volatile memory and a non-volatile memory. The non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), used as an external cache. Through example but not limitative description, many forms of RAMs may be used, for example, a static random access memory (SRAM), a dynamic random access memory (DRAM), a synchronous dynamic random access memory (SDRAM), a double data rate synchronous dynamic random access memory (DDR SDRAM), an enhanced synchronous dynamic random access memory (ESDRAM), a synchronous link dynamic random access memory (SLDRAM), and a direct rambus dynamic random access memory (DR RAM). It should be noted that the memory in the system and method described in this specification includes, but is not limited to, these and any memory of another proper type. 
     A person of ordinary skill in the art may be aware that, in combination with the examples described in embodiments disclosed in this specification, units and algorithm steps can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed by hardware or software depends on particular applications and design constraints of the technical solutions. A person skilled in the art may use different methods to implement the described functions for each particular application, but it should not be considered that the implementation goes beyond the scope of this application. 
     It may be clearly understood by a person skilled in the art that, for the purpose of convenient and brief description, for a detailed working process of the foregoing system, apparatus, and unit, refer to a corresponding process in the foregoing method embodiments. Details are not described herein again. 
     In the several embodiments provided in this application, it should be understood that, the disclosed system, apparatus, and method may be implemented in other manners. For example, the described apparatus embodiments are merely examples. For example, division into the units is merely logical function division and may be other division in actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented through some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electrical, mechanical, or other forms. 
     The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. A part or all of the units may be selected based on actual requirements to achieve the objectives of the solutions of embodiments. 
     In addition, functional units in embodiments of this application may be integrated into one processing unit, each of the units may exist alone physically, or two or more units may be integrated into one unit. 
     When the functions are implemented in the form of a software functional unit and sold or used as an independent product, the functions may be stored in a computer-readable storage medium. Based on such an understanding, the technical solutions of this application essentially, or the part contributing to the prior art, or some of the technical solutions may be implemented in a form of a software product. The computer software product is stored in a storage medium, and includes several instructions for instructing a computer device (which may be a personal computer, a server, a network device, or the like) to perform all or a part of the steps of the methods described in embodiments of this application. The foregoing storage medium includes any medium that can store program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disc. 
     The foregoing descriptions are merely specific implementations of this application, but are not intended to limit the protection scope of this application. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in this application shall fall within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.