Multi-channel signal encoding method, multi-channel signal decoding method, encoder, and decoder

Abstract

A multi-channel signal encoding method, a multi-channel signal decoding method, an encoder, and a decoder are provided.SOLUTION: The encoding method includes determining a downmixed signal of a first channel signal and a second channel signal in a multi-channel signal, and initial reverberation gain parameters of the first channel signal and the second channel signal, determining target reverberation gain parameters of the first channel signal and the second channel signal based on a correlation between the first channel signal and the downmixed signal, a correlation between the second channel signal and the downmixed signal, and the initial reverberation gain parameters, and quantizing the first channel signal and the second channel signal based on the downmixed signal and the target reverberation gain parameters, and writing a quantized first channel signal and a quantized second channel signal into a bitstream. Quality of a channel signal obtained after reverberation processing can be improved by the encoding method, the decoding method, the encoder, and the decoder.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This application claims priority to Chinese Patent Application No. 201710205821.2, entitled "Multi-channel signal encoding method, multi-channel signal decoding method, encoder, and decoder," filed with the China Patent Office on March 31, 2017, the entire contents of which are incorporated herein by reference.

[0002] This application relates to the field of audio coding, and more particularly to a method for encoding a multi-channel signal, a method for decoding a multi-channel signal, an encoder, and a decoder. [Background technology]

[0003] As the quality of life improves, people have a higher demand for high-quality sound. Compared with mono sound, stereo sound provides a sense of direction and distribution for each sound source, and also improves clarity, intelligibility, and the sense of sound location. Therefore, stereo sound is very popular.

[0004] Stereo processing techniques mainly include Mid / Sid (MS) coding, Intensity Stereo (IS) coding, and Parametric Stereo (PS) coding.

[0005] In the prior art, when encoding channel signals using PS coding, the encoder performs spatial parameter analysis on the multiple channel signals to obtain reverberation gain parameters and other spatial parameters of the multiple channel signals, and encodes the reverberation gain parameters and other spatial parameters of the multiple channel signals, so that the decoder can perform reverberation processing on the multiple channel signals obtained by decoding based on the reverberation gain parameters of the channel signals during decoding to improve the auditory effect. However, in some cases, for example, when the correlation between the multiple channel signals is relatively low, performing reverberation processing on the multiple channel signals obtained by decoding based on the reverberation gain parameters corresponding to the multiple channel signals will cause worse auditory effect. Summary of the Invention

[0006] This application provides a multi-channel signal encoding method, a multi-channel signal decoding method, an encoder and a decoder for improving the quality of the channel signals. [Means for solving the problem]

[0007] According to a first aspect, there is provided a multi-channel signal encoding method, the method including: determining a down-mix signal of a first channel signal and a second channel signal in the multi-channel signal and initial reverberation gain parameters for the first channel signal and the second channel signal; determining target reverberation gain parameters for the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal, a correlation between the second channel signal and the down-mix signal, and the initial reverberation gain parameter; and quantizing the first channel signal and the second channel signal based on the down-mix signal and the target reverberation gain parameter, and writing the quantized first channel signal and the quantized second channel signal into a bitstream.

[0008] In this application, when the target reverberation gain parameter of the channel signal is determined, the correlation between the channel signal and the downmix signal is taken into consideration, so that a better processing effect can be obtained when reverberation processing is performed on the channel signal based on the target reverberation gain parameter, thereby improving the quality of the channel signal obtained after reverberation processing.

[0009] Optionally, the correlation between the first channel signal or the second channel signal and the downmix signal may be determined based on a difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal, or may be determined based on a difference between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the downmix signal.

[0010] In relation to the first aspect, in some implementations of the first aspect, the first channel signal, the second channel signal, and the downmix signal are channel signals obtained after a normalization process.

[0011] In relation to the first aspect, in some implementations of the first aspect, the step of determining target reverberation gain parameters for the first channel signal and the second channel signal based on the correlation between the first channel signal and the downmix signal, the correlation between the second channel signal and the downmix signal, and the initial reverberation gain parameter includes the steps of determining a target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal, and adjusting the initial reverberation gain parameter based on the target attenuation coefficient to obtain the target reverberation gain parameter.

[0012] The initial reverberation gain parameters of the channel signals may be flexibly adjusted based on the correlation value between the channel signals and the downmix signal by using the attenuation coefficients.

[0013] The correlation between the first channel signal, the second channel signal, and the downmix signal can be conveniently measured by using the energy of the channel signals. That is, the target attenuation coefficient can be conveniently determined by comparing the difference between the energy of the channel signals and the energy of the downmix signal. Specifically, if the difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal is relatively large (greater than a predetermined threshold), the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal may be considered relatively weak. In this case, a relatively large target attenuation coefficient can be determined. However, if the difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal is relatively small (smaller than a predetermined threshold), the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal may be considered relatively weak. In this case, a relatively small target attenuation coefficient can be determined.

[0014] The step of determining a target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal may be a step of calculating a target attenuation coefficient based on the correlation between the channel signals and the downmix signal, or a step of directly determining a preset attenuation coefficient as the target attenuation coefficient after the correlation between the channel signals and the downmix signal is taken into consideration.

[0015] In relation to the first aspect, in some implementations of the first aspect, each of the first channel signal and the second channel signal includes a plurality of frequency bins, and the step of determining the target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal includes the steps of determining difference values ​​between the energy of the first channel signal and the energy of the downmix signal at the plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal at the plurality of frequency bins, and determining the target attenuation coefficient based on the difference values.

[0016] The difference between the energy of the first channel signal and the energy of the down-mix signal and the difference between the energy of the second channel signal and the energy of the down-mix signal can be conveniently determined by comparing difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in multiple frequency bins and difference values ​​between the energy of the second channel signal and the energy of the down-mix signal in multiple frequency bins, and an attenuation coefficient is further determined. Therefore, there is no need to compare the difference between the energy of the first channel signal and the energy of the down-mix signal and the difference between the energy of the second channel signal and the energy of the down-mix signal in all frequency bands.

[0017] In relation to the first aspect, in some implementations of the first aspect, the step of determining difference values ​​between the energy of the first channel signal and the energy of the downmix signal in a plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal in a plurality of frequency bins includes: determining a first difference value between the energy of the first channel signal and the energy of the downmix signal, where the first difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the downmix signal in a plurality of frequency bins; and determining a second difference value between the energy of the second channel signal and the energy of the downmix signal, where the second difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the downmix signal in a plurality of frequency bins; and the step of determining a target attenuation coefficient based on the difference value includes determining a target attenuation coefficient based on a ratio between the first difference value and the second difference value.

[0018] Alternatively, the target damping coefficient may be determined directly based on the first difference value and the second difference value.

[0019] In relation to the first aspect, in some implementations of the first aspect, before the step of determining the target damping coefficient based on the difference value, the method further includes the step of determining that the difference value is greater than a preset threshold.

[0020] Only when the difference values ​​between the energy of the first channel signal and the energy of the down-mix signal and between the energy of the second channel signal and the energy of the down-mix signal in multiple frequency bins are relatively large, the target attenuation coefficient is determined, and the initial reverberation gain parameter is adjusted based on the target attenuation coefficient. When the difference values ​​are relatively small, the initial reverberation gain parameter does not need to be adjusted, thereby improving coding efficiency.

[0021] If the difference value between the energy of the multi-channel signals and the energy of the downmix signal is smaller than a preset threshold, the initial reverberation gain parameters of the multi-channel signals may be directly determined as the target reverberation gain parameters of the multi-channel signals.

[0022] With regard to the first aspect, in some implementations of the first aspect, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0023] The energy of the downmix signal can be calculated by using the energy of the first channel signal and the energy of the second channel signal, and the calculation process can be simplified without using the downmix signal itself.

[0024] In relation to the first aspect, in some implementations of the first aspect, the target attenuation coefficient includes multiple attenuation coefficients, each of which corresponds to at least one subband of the multiple channel signals, and any subband corresponds to only one attenuation coefficient.

[0025] In addition, when the target attenuation coefficient includes multiple attenuation coefficients, the reverberation gain parameter can be adjusted more flexibly based on the target attenuation coefficient.

[0026] In relation to the first aspect, in some implementations of the first aspect, the frequency bands in which the first channel signal and the second channel signal are located each include a first frequency band and a second frequency band, and an attenuation coefficient corresponding to a subband in the first frequency band is less than or equal to an attenuation coefficient corresponding to a subband in the second frequency band, and the frequency of the first frequency band is less than the frequency of the second frequency band.

[0027] The reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands can be adjusted to different degrees by setting different sizes of attenuation coefficients for the reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands, and can also obtain better processing effects during reverberation processing.

[0028] According to a second aspect, there is provided a multi-channel signal decoding method, the method including the steps of: determining a down-mix signal of a first channel signal and a second channel signal in the multi-channel signal, and initial reverberation gain parameters of the first channel signal and the second channel signal; determining identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal and a correlation between the second channel signal and the down-mix signal, wherein the identification information is used to indicate a channel signal in the first channel signal and the second channel signal, the initial reverberation gain parameter of which needs to be adjusted; and quantizing the first channel signal and the second channel signal based on the down-mix signal, the initial reverberation gain parameter, and the identification information, and writing the quantized first channel signal and the quantized second channel signal into a bitstream.

[0029] Optionally, the correlation between the first channel signal or the second channel signal and the downmix signal may be determined based on a difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal, or may be determined based on a difference between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the downmix signal.

[0030] In this application, the channel signals whose initial reverberation gain parameters need to be adjusted can be determined based on the correlation between the channel signals and the downmix signal, so that the decoder side can first adjust the initial reverberation gain parameters of some channel signals and then perform reverberation processing on these channel signals, thereby improving the quality of the channel signals obtained after reverberation processing.

[0031] In relation to the second aspect, in some implementations of the second aspect, the step of determining identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the downmix signal and a correlation between the second channel signal and the downmix signal includes the step of determining identification information of the first channel signal and the second channel signal based on a correlation between an energy of the first channel signal and an energy of the downmix signal and a correlation between an energy of the second channel signal and an energy of the downmix signal.

[0032] The correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal can be conveniently measured by using the energy of the channel signal and the energy of the downmix signal, so that the channel signal whose initial reverberation gain parameter needs to be adjusted can be conveniently determined.

[0033] In relation to the second aspect, in some implementations of the second aspect, the step of determining identification information of the first channel signal and the second channel signal based on the correlation between the energy of the first channel signal and the energy of the down-mix signal and the correlation between the energy of the second channel signal and the energy of the down-mix signal includes the steps of determining a first difference value and a second difference value, where the first difference value is a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal at a plurality of frequency bins and the second difference value is a sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the down-mix signal at a plurality of frequency bins; and determining identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value.

[0034] It should be understood that the energy values ​​of the first channel signal, the second channel signal, and the down-mix signal may be values ​​obtained after a normalization process.

[0035] The difference between the energy of the first channel signal and the energy of the down-mix signal and the difference between the energy of the second channel signal and the energy of the down-mix signal can be conveniently determined by comparing difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in multiple frequency bins and between the energy of the second channel signal and the energy of the down-mix signal in multiple frequency bins to determine the channel signals whose initial reverberation gain parameters need to be adjusted. Therefore, there is no need to compare the difference between the energy of the first channel signal and the energy of the down-mix signal in all frequency bands.

[0036] In relation to the second aspect, in some implementations of the second aspect, the step of determining identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value includes the step of determining the larger difference value of the first difference value and the second difference value as a target difference value, and the step of determining identification information based on the target difference value, wherein the identification information is used to specifically indicate the channel signal corresponding to the target difference value, and the channel signal corresponding to the target difference value is the channel signal whose initial reverberation gain parameter needs to be adjusted.

[0037] In relation to the second aspect, in some implementations of the second aspect, the method further includes a step of determining a target attenuation coefficient based on the first difference value and the second difference value, where the target attenuation coefficient is used to adjust an initial reverberation gain parameter of the target channel signal, and a step of quantizing the target attenuation coefficient and writing the quantized target attenuation coefficient to the bitstream.

[0038] The initial reverberation gain parameters of the channel signals may be flexibly adjusted based on the correlation value between the channel signals and the downmix signal by using the attenuation coefficients.

[0039] In relation to the second aspect, in some implementations of the second aspect, the target attenuation coefficient includes multiple attenuation coefficients, each of which corresponds to at least one subband of the target channel signal, and any subband corresponds to only one attenuation coefficient.

[0040] In addition, when the target attenuation coefficient includes multiple attenuation coefficients, the reverberation gain parameter can be adjusted more flexibly based on the target attenuation coefficient.

[0041] In relation to the second aspect, in some implementations of the second aspect, the target channel signal includes a first frequency band and a second frequency band, an attenuation coefficient corresponding to a subband in the first frequency band is less than or equal to an attenuation coefficient corresponding to a subband in the second frequency band, and the frequency of the first frequency band is less than the frequency of the second frequency band.

[0042] The reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands can be adjusted to different degrees by setting different sizes of attenuation coefficients for the reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands, and can also obtain better processing effects during reverberation processing.

[0043] With regard to the second aspect, in some implementations of the second aspect, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0044] The energy of the downmix signal is estimated or predicted by using the energies of the multiple channel signals, which allows for reduced computation.

[0045] According to a third aspect, there is provided a multi-channel signal decoding method, the method including: obtaining a bitstream; determining, based on the bitstream, a down-mix signal of a first channel signal and a second channel signal in the multi-channel signal, initial reverberation gain parameters of the first channel signal and the second channel signal, and identification information of the first channel signal and the second channel signal, where the identification information is used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted; determining, based on the identification information, the channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted as a target channel signal; and adjusting the initial reverberation gain parameter of the target channel signal.

[0046] In this application, by using the identification information, a channel signal whose initial reverberation gain parameter needs to be adjusted can be determined, and the initial reverberation gain parameter of the channel signal is adjusted before reverberation processing is performed on the channel signal, thereby improving the quality of the channel signal obtained after reverberation processing.

[0047] In relation to the third aspect, in some implementations of the third aspect, adjusting the initial reverberation gain parameter of the target channel signal includes determining a target attenuation coefficient and adjusting the initial reverberation gain parameter of the target channel signal based on the target attenuation coefficient to obtain the target reverberation gain parameter of the target channel signal.

[0048] The initial reverberation gain parameters of the channel signals may be flexibly adjusted based on the correlation value between the channel signals and the downmix signal by using the attenuation coefficients.

[0049] With regard to the third aspect, in some implementations of the third aspect, determining the target damping coefficient includes determining a preset damping coefficient as the target damping coefficient.

[0050] By presetting the attenuation factor, the process of determining the target attenuation factor can be simplified, thereby improving decoding efficiency.

[0051] With respect to the third aspect, in some implementations of the third aspect, determining the target attenuation factor includes obtaining the target attenuation factor based on the bitstream.

[0052] If the bitstream includes the target attenuation coefficient, the target attenuation coefficient may be obtained directly from the bitstream, and the process of determining the target attenuation coefficient can also be simplified, thereby improving the decoding efficiency.

[0053] In relation to the third aspect, in some implementations of the third aspect, the step of determining the target attenuation coefficient includes the steps of obtaining an inter-channel level difference between the first channel signal and the second channel signal from the bitstream, and determining the target attenuation coefficient based on the inter-channel level difference, or determining the target attenuation coefficient based on the inter-channel level difference and the downmix signal.

[0054] The target attenuation coefficient can be determined more flexibly and accurately based on the inter-channel level difference, the downmix signal, etc., so that the initial reverberation parameters of the channel signals can be adjusted more accurately based on the attenuation coefficient.

[0055] In relation to the third aspect, in some implementations of the third aspect, the target attenuation coefficient includes multiple attenuation coefficients, each of which corresponds to at least one subband of the target channel signal, and any subband corresponds to only one attenuation coefficient.

[0056] In addition, when the target attenuation coefficient includes multiple attenuation coefficients, the reverberation gain parameter can be adjusted more flexibly based on the target attenuation coefficient.

[0057] In relation to the third aspect, in some implementations of the third aspect, the target channel signal includes a first frequency band and a second frequency band, an attenuation coefficient corresponding to a subband in the first frequency band is less than or equal to an attenuation coefficient corresponding to a subband in the second frequency band, and the frequency of the first frequency band is less than the frequency of the second frequency band.

[0058] The reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands can be adjusted to different degrees by setting different sizes of attenuation coefficients for the reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands, and can also obtain better processing effects during reverberation processing.

[0059] According to a fourth aspect, there is provided an encoder, the encoder comprising a module or unit configured to perform the method of the first aspect or various implementations of the first aspect.

[0060] According to a fifth aspect, there is provided an encoder, the encoder comprising a module or unit configured to perform the method of the second aspect or various implementations of the second aspect.

[0061] According to a sixth aspect, there is provided a decoder, the encoder comprising a module or unit configured to perform the method of the third aspect or various implementations of the third aspect.

[0062] According to a seventh aspect, there is provided an encoder, the encoder including a memory and a processor, the memory configured to store a program, the processor configured to execute the program, and when the program is executed, the processor performs the method of the first aspect or various implementations of the first aspect.

[0063] According to an eighth aspect, there is provided an encoder, the encoder including a memory and a processor, the memory configured to store a program, the processor configured to execute the program, and when the program is executed, the processor performs the method of the second aspect or various implementations of the second aspect.

[0064] According to a ninth aspect, there is provided a decoder, the decoder including a memory and a processor, the memory configured to store a program, the processor configured to execute the program, and when the program is executed, the processor performs the method of the third aspect or various implementations of the third aspect.

[0065] According to a tenth aspect, there is provided a computer-readable medium storing program code to be executed by a device, the program code including instructions used to perform the method of the first aspect or various implementations of the first aspect.

[0066] According to an eleventh aspect, there is provided a computer-readable medium, the computer-readable medium storing program code to be executed by a device, the program code including instructions used to perform the method of the second aspect or various implementations of the second aspect.

[0067] According to a twelfth aspect, there is provided a computer-readable medium storing program code to be executed by a device, the program code including instructions used to perform the method of the third aspect or various implementations of the third aspect. [Brief explanation of the drawings]

[0068] [Figure 1] 1 is a schematic flowchart of encoding a left channel signal and a right channel signal in the prior art; [Figure 2] 1 is a schematic flowchart of decoding a left channel signal and a right channel signal in the prior art; [Figure 3] 1 is a schematic flowchart of a multi-channel signal encoding method according to an embodiment of the present application; [Figure 4] 1 is a schematic flowchart of a multi-channel signal decoding method according to an embodiment of the present application; [Figure 5] 1 is a schematic flowchart of a multi-channel signal encoding method according to an embodiment of the present application; [Figure 6] 1 is a schematic flowchart of a multi-channel signal encoding method according to an embodiment of the present application; [Figure 7] 1 is a schematic flowchart of a multi-channel signal decoding method according to an embodiment of the present application; [Figure 8] 1 is a schematic block diagram of an encoder according to an embodiment of the present application; [Figure 9] 1 is a schematic block diagram of an encoder according to an embodiment of the present application; [Figure 10]FIG. 2 is a schematic block diagram of a decoder according to an embodiment of the present application; [Figure 11] 1 is a schematic block diagram of an encoder according to an embodiment of the present application; [Figure 12] 1 is a schematic block diagram of an encoder according to an embodiment of the present application; [Figure 13] FIG. 2 is a schematic block diagram of a decoder according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0069] The following describes the technical solution of this application with reference to the accompanying drawings. In order to better understand the multi-channel signal encoding method and multi-channel signal decoding method in the embodiments of this application, the following first briefly describes the multi-channel signal encoding method and multi-channel signal decoding method in the prior art with reference to Figures 1 and 2.

[0070] 1 shows a process for encoding a left channel signal and a right channel signal in the prior art. The encoding process shown in FIG. 1 specifically includes the following steps:

[0071] 110. Perform spatial parameter analysis and downmix processing on the left channel signal (denoted by L in the figure) and the right channel signal (denoted by R in the figure).

[0072] Specifically, step 110 specifically includes: performing a spatial parameter analysis on the left channel signal and the right channel signal to obtain spatial parameters of the left channel signal and spatial parameters of the right channel signal; and performing a downmixing process on the left channel signal and the right channel signal to obtain a downmixed signal (the downmixed signal obtained after the downmixing process is a mono audio signal, and the original two channels of the audio signal are converted into one channel of the audio signal by the downmixing process).

[0073] Spatial parameters (sometimes referred to as spatial sensing parameters) include inter-channel coherence (IC), inter-channel level difference (ILD), inter-channel time difference (ITD), inter-channel phase difference (IPD), etc.

[0074] IC represents inter-channel cross-correlation or coherence. This parameter determines the detection of sound field range and can improve the spatial sense and sound stability of audio signals. ILD is used to distinguish the horizontal angle of stereo sources and represents the inter-channel intensity difference, which also affects frequency components throughout the spectrum. ITD and IPD are spatial parameters that represent the horizontal direction of the sound source. ITD and IPD represent inter-channel time and phase differences. These parameters mainly affect frequency components below 2 kHz. For two-channel signals, ITD may represent the time delay between the left and right stereo channel signals, and IPD may represent the waveform similarity of the left and right stereo channel signals after time alignment. ILD, ITD, and IPD determine the human ear's detection of the location of sound sources, effectively determine sound field location, and play an important role in stereo signal restoration.

[0075] 120. Encode the downmix signal to obtain a bitstream.

[0076] 130. Encode the spatial parameters to obtain a bitstream.

[0077] 140. Multiplex the bitstream obtained by encoding the downmix signal and the bitstream obtained by encoding the spatial parameters to obtain one bitstream.

[0078] The resulting bitstream is stored or transmitted to a decoder-side device.

[0079] 2 shows a process for decoding a left channel signal and a right channel signal in the prior art. The decoding process shown in FIG. 2 specifically includes the following steps:

[0080] 210. Demultiplex the bitstream to separately obtain a bitstream obtained by encoding the downmix signal and a bitstream obtained by encoding the spatial parameters.

[0081] 220. Decode the bitstream to obtain a downmix signal of the left channel signal and the right channel signal, spatial parameters of the left channel signal, and spatial parameters of the right channel signal.

[0082] The spatial parameters include the IC of the left and right channel signals.

[0083] 230. Obtain a decorrelation signal based on the downmix signal and the spatial parameters of the previous frame.

[0084] The left channel signal and the right channel signal are obtained based on the decoded downmix signal and the decorrelated signal of the current frame.

[0085] 240. Obtain the final output left and right channel signals (represented by L' and R' respectively in FIG. 2) based on the spatial parameters, the left channel signal, and the right channel signal.

[0086] It should be understood that the left and right channel signals in step 240 (represented by L' and R', respectively, in FIG. 2) may be distorted to some extent compared to the left and right channel signals obtained by decoding and coded at the encoder side.

[0087] Specifically, the downmix signal may be filtered, and then the inter-channel correlation parameters are used to correct the filtered downmix signal to obtain a decorrelated signal.

[0088] The purpose of generating the decorrelated signals is to improve the sense of reverberation of the stereo signal finally generated at the decoder side and widen the sound field width of the stereo signal, so that the output audio signal becomes mellower and fuller for the human ear. The sense of reverberation is essentially the effect of delaying the original audio signal, such as by reflecting and refracting it differently, and then superimposing the reflected and refracted audio signal on the original audio signal as it enters the human ear.

[0089] In the prior art, after the IC is obtained, the correlation between different channel signals is not taken into consideration to adaptively adjust the IC. In this case, if reverberation processing is performed on the channel signals based on the previously obtained IC, a relatively poor hearing effect may be caused. For example, when the correlation between different channel signals is relatively low, if the previously obtained IC is still used to correct the uncorrelated signal, and then the uncorrelated signal is used to perform the same reverberation processing on the different channel signals, the quality of the channel signals finally output from the decoder side is relatively low. That is, because the difference between the different channel signals is relatively large, if reverberation processing is performed on the different channel signals by still using the uncorrelated signal corrected by the previous relatively large IC, the reverberation effect of the channel signals is not increased, but the output channel signals may be distorted.

[0090] Therefore, an embodiment of this application provides a method for encoding or decoding a multi-channel signal, in which a reverberation gain parameter can be adjusted correspondingly based on the correlation between different channel signals, and the adjusted reverberation gain parameter is used to correct the uncorrelated signals. Then, reverberation processing is performed on the different channel signals by using the uncorrelated signals. In this way, when reverberation processing is performed on the different channel signals, the correlation between the different channel signals is taken into account, thereby resulting in better quality of the output channel signals.

[0091] 3 is a schematic flowchart of a multi-channel signal encoding method according to an embodiment of the present application. The method of FIG. 3 may be performed by an encoder-side device or an encoder. The method of FIG. 3 includes the following steps:

[0092] 310. Determine a downmix signal of the first channel signal and the second channel signal in the multi-channel signal, and initial reverberation gain parameters of the first channel signal and the second channel signal.

[0093] It should be understood that in this embodiment of the application, the sequence of determining the downmix signal and determining the initial reverberation gain parameter is not limited, and the downmix signal and the initial reverberation gain parameter may be determined simultaneously or successively.

[0094] The initial reverberation gain parameters may be reverberation gain parameters obtained after a spatial parameter analysis is performed on the first channel signal and the second channel signal.

[0095] Specifically, the downmix signal may be obtained by performing a downmix process on a plurality of channel signals, where the spatial parameters of the first channel signal and the spatial parameters of the second channel signal are obtained by performing a spatial parameter analysis on the first channel signal and the second channel signal, and the spatial parameters include initial reverberation gain parameters of the first channel signal and the second channel signal.

[0096] It should be understood that the first channel signal and the second channel signal may correspond to the same spatial parameters, and correspondingly, the first channel signal and the second channel signal may correspond to the same initial reverberation gain parameters, i.e., the spatial parameters of the first channel signal and the spatial parameters of the second channel signal may be the same, and the initial reverberation gain parameters of the first channel signal and the second channel signal may be the same.

[0097] Furthermore, assuming that each of the first channel signal and the second channel signal includes 10 subbands and each subband corresponds to one reverberation gain parameter, the reverberation gain parameters corresponding to the subbands of the first channel signal and the second channel signal having the same index value may be the same.

[0098] Furthermore, the first channel signal, the second channel signal, and the downmix signal may be channel signals obtained after normalization processing.

[0099] 320. Determine target reverberation gain parameters for the first channel signal and the second channel signal based on the correlation between the first channel signal and the downmix signal, the correlation between the second channel signal and the downmix signal, and the initial reverberation gain parameters.

[0100] Optionally, the correlation between the first channel signal or the second channel signal and the downmix signal may be determined based on a difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal, or may be determined based on a difference between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the downmix signal.

[0101] Specifically, when the difference between the energy or amplitude of the first channel signal and the energy or amplitude of the downmix signal is relatively small, the correlation between the first channel signal and the downmix signal may be considered to be relatively large.When the difference between the energy or amplitude of the first channel signal and the energy or amplitude of the downmix signal is relatively large, the correlation between the first channel signal and the downmix signal may be considered to be relatively small.

[0102] The difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the down-mix signal may specifically be a difference value between the energy of the first channel signal or the energy of the second channel signal and the energy of the down-mix signal. Similarly, the difference between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the down-mix signal may specifically be a difference value between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the down-mix signal.

[0103] Furthermore, the correlation between the first channel signal or the second channel signal and the downmix signal may instead refer to the difference between the phase, period, etc. of the first channel signal or the second channel signal and the phase, period, etc. of the downmix signal.

[0104] 330. Quantize the first channel signal and the second channel signal based on the downmix signal and the target reverberation gain parameter, and write the quantized first channel signal and the quantized second channel signal into a bitstream.

[0105] It should be understood that when a multi-channel signal has three or more channel signals, for example, when the multi-channel signal includes a first channel signal, a second channel signal, a third channel signal, and a fourth channel signal, the first channel signal and the second channel signal are processed by using the method of FIG. 3, and the third channel signal and the fourth channel signal are also processed by using the method of FIG.

[0106] In this application, when the target reverberation gain parameter of the channel signal is determined, the correlation between the channel signal and the downmix signal is taken into consideration, so that a better processing effect can be obtained when reverberation processing is performed on the channel signal based on the target reverberation gain parameter, thereby improving the quality of the channel signal obtained after reverberation processing.

[0107] Optionally, in one embodiment, the step of determining target reverberation gain parameters for the first channel signal and the second channel signal based on the correlation between the first channel signal and the downmix signal, the correlation between the second channel signal and the downmix signal, and the initial reverberation gain parameter includes the steps of determining a target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal, and adjusting the initial reverberation gain parameter based on the target attenuation coefficient to obtain the target reverberation gain parameter.

[0108] Specifically, the step of determining the target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal may be a step of calculating the target attenuation coefficient based on the correlation between the channel signal and the downmix signal, or may be a step of directly determining a preset attenuation coefficient as the target attenuation coefficient after the correlation between the channel signal and the downmix signal is taken into consideration.

[0109] The initial reverberation gain parameters of the channel signals may be flexibly adjusted based on the correlation value between the channel signals and the downmix signal by using the attenuation coefficients.

[0110] For example, when the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal are relatively large (in this case, the first channel signal may be considered to be relatively similar to the second channel signal), a target attenuation coefficient with a relatively small value may be determined. However, when the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal are relatively small (in this case, the first channel signal may be considered to be relatively different from the second channel signal), a target attenuation coefficient with a relatively large value may be determined.

[0111] In some embodiments, the correlation between the multiple channel signals and the downmix signal may refer to the difference between the energy of the multiple channel signals and the energy of the downmix signal, or the difference between the amplitude of the multiple channel signals and the amplitude of the downmix signal. The difference between the energy of the multiple channel signals and the energy of the downmix signal may specifically be the difference value between the energy of the multiple channel signals and the energy of the downmix signal. Similarly, the difference between the amplitude of the multiple channel signals and the amplitude of the downmix signal may specifically be the difference value between the amplitude of the multiple channel signals and the amplitude of the downmix signal. In addition, the correlation between the multiple channel signals and the downmix signal may instead refer to the difference between the phase, period, etc. of the multiple channel signals and the phase, period, etc. of the downmix signal.

[0112] In some embodiments, a correlation between the first channel signal or the second channel signal and the downmix signal may be determined based on a difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal, and further a target attenuation coefficient is determined.

[0113] The correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal can be conveniently measured by using the energy of the channel signal and the energy of the downmix signal, i.e., the target attenuation factor can be conveniently determined by comparing the difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal.

[0114] Optionally, in one embodiment, both the first channel signal and the second channel signal include a plurality of frequency bins, and the step of determining a target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal includes the steps of determining difference values ​​between the energy of the first channel signal and the energy of the downmix signal in the plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal in the plurality of frequency bins, and determining a target attenuation coefficient based on the difference values.

[0115] The difference values ​​between the energy of the first channel signal and the energy of the downmix signal in multiple frequency bins may be difference values ​​between the energy of the first channel signal and the energy of the downmix signal in multiple of the same frequency bins. For example, the first channel signal includes three frequency bins (a first frequency channel number, a second frequency channel number, and a third frequency channel number). In this case, the difference values ​​between the energy of the first channel signal and the energy of the downmix signal in the three frequency bins are specifically the difference value between the first channel signal and the downmix signal at the first frequency channel number, the difference value between the first channel signal and the downmix signal at the second frequency channel number, and the difference value between the first channel signal and the downmix signal at the third frequency channel number.

[0116] Similarly, the difference value between the energy of the second channel signal and the energy of the downmix signal in a plurality of frequency bins may be the difference value between the energy of the second channel signal and the energy of the downmix signal in a plurality of the same frequency bins.

[0117] Optionally, the difference value between the energy of the first channel signal and the energy of the downmix signal in the plurality of frequency bins may be a sum of absolute values ​​of the difference values ​​between the energy of the first channel signal and the energy of the downmix signal in the plurality of frequency bins. Similarly, the difference value between the energy of the second channel signal and the energy of the downmix signal in the plurality of frequency bins may be a sum of absolute values ​​of the difference values ​​between the energy of the second channel signal and the energy of the downmix signal in the plurality of frequency bins.

[0118] It should be understood that the energy values ​​of the first channel signal, the second channel signal, and the down-mix signal may be values ​​obtained after a normalization process.

[0119] The difference between the energy of the first channel signal and the energy of the down-mix signal and the difference between the energy of the second channel signal and the energy of the down-mix signal can be conveniently determined by comparing difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in multiple frequency bins and difference values ​​between the energy of the second channel signal and the energy of the down-mix signal in multiple frequency bins, and an attenuation coefficient is further determined. Therefore, there is no need to compare the difference between the energy of the first channel signal and the energy of the down-mix signal and the difference between the energy of the second channel signal and the energy of the down-mix signal in all frequency bands.

[0120] Optionally, in one embodiment, the step of determining difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in a plurality of frequency bins and between the energy of the second channel signal and the energy of the down-mix signal in a plurality of frequency bins includes the steps of: determining a first difference value between the energy of the first channel signal and the energy of the down-mix signal, where the first difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in a plurality of frequency bins; determining a second difference value between the energy of the second channel signal and the energy of the down-mix signal, where the second difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in a plurality of frequency bins; and determining a target attenuation coefficient based on the first difference value and the second difference value.

[0121] Determining the target damping coefficient based on the first difference value and the second difference value may include determining the target damping coefficient based on a ratio between the first difference value and the second difference value.

[0122] Specifically, if the first channel signal is a left channel signal and the second channel signal is a right channel signal, the first difference value and the second difference value may be calculated according to the following formula:

number

[0123] When the target attenuation coefficient is determined based on the first difference value and the second difference value, the ratio between the first difference value and the second difference value may be directly determined as the target attenuation coefficient. For example, the first difference value is a and the second difference value is b. When a < b, a / b is determined as the target attenuation coefficient, or when a > b, b / a is determined as the target attenuation coefficient. Also, after the target attenuation coefficient is determined based on the first difference value and the second difference value, some smoothing process may be performed with respect to the target attenuation coefficient and the attenuation coefficient of the previous frame, and the target attenuation coefficient obtained after the smoothing process is used to further adjust the initial reverberation gain parameters of the plurality of channel signals.

[0124] Optionally, in one embodiment, before the target attenuation coefficient is determined based on the aforementioned difference value, the method of FIG. 3 further includes determining that the difference value is greater than a preset threshold.

[0125] Here, it should be understood that a difference value greater than a preset threshold in this specification may mean that the difference values ​​between the energy of the first channel signal and the energy of the down-mix signal and between the energy of the second channel signal and the energy of the down-mix signal in multiple frequency bins are greater than the same preset threshold, or may mean that the difference between the energy of the first channel signal and the energy of the down-mix signal is greater than a preset first threshold and the difference between the energy of the second channel signal and the energy of the down-mix signal is greater than a preset second threshold.

[0126] Only when the difference values ​​between the energy of the first channel signal and the energy of the down-mix signal and between the energy of the second channel signal and the energy of the down-mix signal in multiple frequency bins are relatively large, the target attenuation coefficient is determined, and the initial reverberation gain parameter is adjusted based on the target attenuation coefficient. When the difference values ​​are relatively small, the initial reverberation gain parameter does not need to be adjusted, thereby improving coding efficiency.

[0127] For example, if the difference value between the energy of the first channel signal and the energy of the downmix signal is greater than M (M is 0.5 to 1) times the energy of the first channel signal, the difference value between the energy of the first channel and the energy of the downmix signal may be considered to be greater than the preset threshold. In this case, the preset threshold is M times the energy of the first channel signal. Alternatively, if the ratio of the difference value between the energy of the first channel signal and the energy of the downmix signal to the energy of the first channel signal is greater than M, the difference value between the energy of the first channel and the energy of the downmix signal may be considered to be greater than the preset threshold.

[0128] If the difference value between the energy of the multi-channel signals and the energy of the downmix signal is smaller than a preset threshold, the initial reverberation gain parameters of the multi-channel signals may be directly determined as the target reverberation gain parameters of the multi-channel signals.

[0129] Optionally, in one embodiment, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0130] The energy of the downmix signal can be calculated by using the energy of the first channel signal and the energy of the second channel signal, and the calculation process can be simplified without using the downmix signal itself.

[0131] Indeed, in this embodiment of this application, the energy of the downmix signal may instead be calculated directly based on the downmix signal itself.

[0132] Optionally, in one embodiment, the target attenuation coefficients include multiple attenuation coefficients, each of the multiple attenuation coefficients corresponding to at least one subband of the multiple channel signals, and any subband corresponding to only one attenuation coefficient.

[0133] For example, the subband indices included in each of the first channel signal and the second channel signal range from 0 to 9. The first channel signal and the second channel signal each include 10 reverberation gain parameters, each subband corresponding to one reverberation gain parameter, and the target attenuation coefficients include 5 attenuation coefficients, each corresponding to two subbands, or the target attenuation coefficients include 10 attenuation coefficients, each corresponding to one subband.

[0134] In addition, when the target attenuation coefficient includes multiple attenuation coefficients, the reverberation gain parameters can be adjusted more flexibly based on the target attenuation coefficients. For example, the reverberation gain parameters corresponding to subbands whose indices are 0 to 4 of the multiple channel signals need to be adjusted slightly, while the reverberation gain parameters corresponding to subbands whose indices are 5 to 9 of the channel signals need to be adjusted significantly. In this case, a relatively small attenuation coefficient may be set for the reverberation gain parameters corresponding to the subbands whose indices are 0 to 4, and a relatively large attenuation coefficient may be set for the reverberation gain parameters corresponding to the subbands whose indices are 5 to 9.

[0135] Optionally, in one embodiment, each of the first channel signal and the second channel signal (wherein the frequency band occupied by the first channel signal and the frequency band occupied by the second channel signal are the same) includes a first frequency band and a second frequency band, and an attenuation coefficient corresponding to a subband in the first frequency band is less than or equal to an attenuation coefficient corresponding to a subband in the second frequency band, and the frequency of the first frequency band is less than the frequency of the second frequency band.

[0136] For example, the frequency bands in which the first channel signal and the second channel signal are located each include a low-frequency portion and a high-frequency portion, and the target attenuation coefficient includes a plurality of attenuation coefficients, where the low-frequency portion corresponds to at least one attenuation coefficient and the high-frequency portion corresponds to at least one attenuation coefficient, and the attenuation coefficient corresponding to the low-frequency portion is smaller than the attenuation coefficient corresponding to the high-frequency portion.

[0137] The reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands can be adjusted to different degrees by setting different sizes of attenuation coefficients for the reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands, and can also obtain better processing effects during reverberation processing.

[0138] 4 is a schematic flowchart of a multi-channel signal encoding method according to an embodiment of the present application. In FIG. 4, the channel signals include a left channel signal and a right channel signal, and the process of encoding the left channel signal and the right channel signal specifically includes the following steps:

[0139] 410. Calculate spatial parameters of the left channel signal and spatial parameters of the right channel signal.

[0140] The spatial parameters include initial reverberation gain parameters for the left and right channel signals, as well as other spatial parameters.

[0141] 420. Perform a downmix process on the left channel signal (denoted by L in the figure) and the right channel signal (denoted by R in the figure) to obtain a downmix signal.

[0142] 430. Determine difference values ​​between the energy of the left channel signal and the energy of the downmix signal and between the energy of the right channel signal and the energy of the downmix signal.

[0143] Specifically, each of the left channel signal and the right channel signal may be divided into a high frequency part and a low frequency part, and difference values ​​between the energy of the left channel signal and the energy of the downmix signal and between the energy of the right channel signal and the energy of the downmix signal in the high frequency part are determined as difference values ​​between the energy of the left channel signal and the energy of the downmix signal and between the energy of the right channel signal and the energy of the downmix signal.

[0144] 440. Adjust the reverberation gain parameters of the left channel signal and the right channel signal based on the difference values ​​between the energy of the left channel signal and the energy of the downmix signal and between the energy of the right channel signal and the energy of the downmix signal.

[0145] Specifically, the encoder side may determine a target attenuation coefficient based on a difference value between the energy of the left channel signal and the energy of the downmix signal and between the energy of the right channel signal and the energy of the downmix signal, and may adjust reverberation gain parameters of the left channel signal and the right channel signal based on the target attenuation coefficient.

[0146] 450. Quantize the downmix signal, the adjusted reverberation gain parameter, and other spatial parameters to obtain a bitstream.

[0147] Figure 5 is a schematic flowchart of a multi-channel signal decoding method according to an embodiment of the present application. In Figure 5, the channel signals include a left channel signal and a right channel signal. In Figure 5, the bitstream generated by encoding in the encoding method of Figure 4 may be decoded. The decoding process of Figure 5 specifically includes the following steps:

[0148] 510. Obtain the bit streams of the left channel signal and the right channel signal.

[0149] 520. Decode the bitstream to obtain a downmix signal.

[0150] 530. Decode the bitstream to obtain spatial parameters of the left channel signal and the right channel signal.

[0151] The spatial parameters include the reverberation gain parameters adjusted by the encoder side, i.e., the encoder side encodes the adjusted reverberation gain parameters, so that after decoding the bitstream, the decoder side obtains the reverberation gain parameters adjusted by the encoder side.

[0152] Steps 520 and 530 may be performed simultaneously rather than sequentially.

[0153] 540. Perform subsequent processing (eg smoothing filtering) on ​​the spatial parameters obtained by decoding.

[0154] 550. Obtain a decorrelated signal based on the downmix signal obtained by decoding and the reverberation gain parameter (the reverberation gain parameter is the reverberation gain parameter adjusted by the encoder side).

[0155] In step 540, an upmix process is performed based on the processed spatial parameters and the downmix signal to obtain a left channel signal and a right channel signal.

[0156] 570. Perform reverberation processing separately on the left channel signal and the right channel signal based on the decorrelated signals.

[0157] 5, the reverberation gain parameters on which the reverberation processes performed on the left channel signal and the right channel signal are based have been adjusted based on the correlation between the left channel signal and the downmix signal and between the right channel signal and the downmix signal, so that the corresponding reverberation processes can be performed based on the difference between the left channel signal and the right channel signal, thereby improving the quality of the channel signals obtained after the reverberation processes.

[0158] In the encoding method of Figure 3, the encoder side determines whether the initial reverberation gain parameters of the channel signal need to be adjusted. If the initial reverberation gain parameters of the channel signal need to be adjusted, the encoder side adjusts the initial reverberation gain parameters of the channel signal and encodes the adjusted reverberation gain parameters, so that the decoder side directly performs reverberation processing based on the reverberation gain parameters obtained by decoding.

[0159] In practice, the encoder side may instead only determine whether the initial reverberation gain parameters of the channel signal need to be adjusted. If the initial reverberation gain parameters of the channel signal need to be adjusted, the encoder side sends corresponding indication information to the encoder side. After receiving the indication information, the decoder side adjusts the initial reverberation gain parameters of the channel signal.

[0160] 6 is a schematic flowchart of a multi-channel signal encoding method according to an embodiment of this application. The method of FIG. 6 includes the following steps:

[0161] 610. Determine a downmix signal of the first channel signal and the second channel signal in the multi-channel signal, and initial reverberation gain parameters of the first channel signal and the second channel signal.

[0162] Specifically, the downmix signal may be obtained by performing a downmix process on the first channel signal and the second channel signal, and the spatial parameters are obtained by performing a spatial parameter analysis on the first channel signal and the second channel signal, where the spatial parameters include initial reverberation gain parameters of the first channel signal and the second channel signal.

[0163] It should be understood that the downmix signal and the initial reverberation gain parameters may be determined simultaneously or successively.

[0164] It should be understood that the first channel signal and the second channel signal may correspond to the same spatial parameters, and in particular, the first channel signal and the second channel signal also correspond to the same initial reverberation gain parameters, i.e., the spatial parameters of the first channel signal and the spatial parameters of the second channel signal are the same, and the initial reverberation gain parameters of the first channel signal and the second channel signal are the same.

[0165] Furthermore, assuming that each of the first channel signal and the second channel signal includes 10 subbands and each subband corresponds to one reverberation gain parameter, the reverberation gain parameters corresponding to the subbands of the first channel signal and the second channel signal having the same index value may be the same.

[0166] 620. Determine identification information of the first channel signal and the second channel signal based on the correlation between the first channel signal and the down-mix signal and the correlation between the second channel signal and the down-mix signal, where the identification information is used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted.

[0167] Optionally, the correlation between the first channel signal or the second channel signal and the downmix signal may be determined based on a difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal, or may be determined based on a difference between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the downmix signal.

[0168] Specifically, when the difference between the energy or amplitude of the first channel signal and the energy or amplitude of the downmix signal is relatively small, the correlation between the first channel signal and the downmix signal may be considered to be relatively large.When the difference between the energy or amplitude of the first channel signal and the energy or amplitude of the downmix signal is relatively large, the correlation between the first channel signal and the downmix signal may be considered to be relatively small.

[0169] The difference between the energy of the first channel signal or the energy of the second channel signal and the energy of the down-mix signal may specifically be a difference value between the energy of the first channel signal or the energy of the second channel signal and the energy of the down-mix signal. Similarly, the difference between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the down-mix signal may specifically be a difference value between the amplitude of the first channel signal or the amplitude of the second channel signal and the amplitude of the down-mix signal.

[0170] Furthermore, the correlation between the first channel signal or the second channel signal and the downmix signal may instead refer to the difference between the phase, period, etc. of the first channel signal or the second channel signal and the phase, period, etc. of the downmix signal.

[0171] The first channel signal, the second channel signal, and the downmix signal may be channel signals obtained after a normalization process.

[0172] Specifically, the identification information may indicate that the first channel signal or the second channel signal is a channel signal whose initial reverberation gain parameter needs to be adjusted, or may indicate that the first channel signal and the second channel signal are channel signals whose reverberation gain parameters need to be adjusted, or may indicate that there is no need to adjust the reverberation gain parameters for both the first channel signal and the second channel signal.

[0173] In some embodiments, the identification information may indicate, by using a value of an identifier field, which channel signal among the multiple channel signals needs to have its initial reverberation gain parameter adjusted. For example, the identifier field of the identification information occupies two bits. If the value of the identifier field is 00, it indicates that neither the initial reverberation gain parameter of the first channel signal nor the initial reverberation gain parameter of the second channel signal needs to be adjusted. If the value of the identifier field is 01, it indicates that only the initial reverberation gain parameter of the first channel signal needs to be adjusted. If the value of the identifier field is 10, it indicates that only the initial reverberation gain parameter of the second channel signal needs to be adjusted. If the value of the identifier field is 11, it indicates that both the initial reverberation gain parameters of the first channel signal and the second channel signal need to be adjusted.

[0174] In some embodiments, determining identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the downmix signal and a correlation between the second channel signal and the downmix signal comprises determining identification information of the first channel signal and the second channel signal based on a correlation between an energy of the first channel signal and an energy of the downmix signal and between an energy of the second channel signal and an energy of the downmix signal.

[0175] The correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal can be conveniently measured by using the energy of the channel signal and the energy of the downmix signal, so that the channel signal whose initial reverberation gain parameter needs to be adjusted can be conveniently determined.

[0176] In some embodiments, the energy or amplitude of the downmix signal may be calculated based on the energy of the first channel signal and the energy of the second channel signal, thereby simplifying the calculation process. Alternatively, the energy of the downmix signal may be calculated directly based on the downmix signal itself.

[0177] 630. Quantize the first channel signal and the second channel signal based on the downmix signal, the initial reverberation gain parameter, and the identification information, and write the quantized first channel signal and the quantized second channel signal into a bitstream.

[0178] In this application, by determining the relationship between a preset threshold and the magnitude of the difference value between the energy of a channel signal and the energy of a downmix signal, when the energy of a channel signal is significantly different from the energy of the downmix signal, the channel signal can be determined as the channel signal whose reverberation gain parameter needs to be adjusted. Therefore, the decoder side can first adjust the initial reverberation gain parameter of the channel signal, and then perform reverberation processing on the channel signal, thereby improving the quality of the channel signal obtained after reverberation processing.

[0179] Optionally, in one embodiment, the step of determining identification information of the first channel signal and the second channel signal based on the correlation between the energy of the first channel signal and the energy of the down-mix signal and between the energy of the second channel signal and the energy of the down-mix signal includes the steps of determining a first difference value and a second difference value, where the first difference value is a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in a plurality of frequency bins and the second difference value is a sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the down-mix signal in a plurality of frequency bins; and determining identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value.

[0180] The difference between the energy of the first channel signal and the energy of the down-mix signal and the difference between the energy of the second channel signal and the energy of the down-mix signal can be conveniently determined by comparing difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in multiple frequency bins and between the energy of the second channel signal and the energy of the down-mix signal in multiple frequency bins to determine the channel signals whose initial reverberation gain parameters need to be adjusted. Therefore, there is no need to compare the difference between the energy of the first channel signal and the energy of the down-mix signal in all frequency bands.

[0181] Optionally, the step of determining identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value includes the steps of determining a larger difference value among the first difference value and the second difference value as a target difference value, and determining identification information based on the target difference value, wherein the identification information is specifically used to indicate a target channel signal corresponding to the target difference value, and the channel signal corresponding to the target difference value is a channel signal whose initial reverberation gain parameter needs to be adjusted.

[0182] Specifically, if the sum of the absolute values ​​of the difference values ​​between the energy of the first channel signal and the energy of the downmix signal in multiple frequency bins is greater than the sum of the absolute values ​​of the difference values ​​between the energy of the second channel signal and the energy of the downmix signal in multiple frequency bins, the first channel signal may be determined as a channel signal whose initial reverberation gain parameter needs to be adjusted.

[0183] Furthermore, if both the sum of the absolute values ​​of the difference values ​​between the energy of the first channel signal and the energy of the downmix signal in multiple frequency bins and the sum of the absolute values ​​of the difference values ​​between the energy of the second channel signal and the energy of the downmix signal in multiple frequency bins are relatively large (e.g., both are larger than a preset threshold), another piece of identification information may be determined, and the identification information indicates that both the initial reverberation gain parameters of the first channel signal and the second channel signal need to be adjusted.

[0184] Specifically, in some embodiments, the step of determining identification information of the first channel signal and the second channel signal based on the sum of absolute values ​​of difference values ​​between the energy of the first channel signal or the energy of the second channel signal and the energy of the downmix signal in a plurality of frequency bins includes the steps of: generating first identification information when the sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the downmix signal in a plurality of frequency bins is greater than a preset threshold, wherein the first identification information is used to indicate that an initial reverberation gain parameter of the first channel signal needs to be adjusted; and generating second identification information when the sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the downmix signal in a plurality of frequency bins is greater than a preset threshold, wherein the second identification information is used to indicate that an initial reverberation gain parameter of the second channel signal needs to be adjusted.

[0185] By determining the relationship between the preset threshold and the magnitude of the difference value between the energy of a channel signal and the energy of the downmix signal, when the energy of a channel signal is significantly different from that of the downmix signal, the channel signal can be determined as the channel signal whose reverberation gain parameter needs to be adjusted. Therefore, the decoder side can first adjust the initial reverberation gain parameter of the channel signal, and then perform reverberation processing on the channel signal, thereby improving the quality of the channel signal obtained after reverberation processing.

[0186] It should be understood that the identification information of the first channel signal and the second channel signal may be one piece of identification information or two pieces of identification information. For example, if both the initial reverberation gain parameters of the first channel signal and the second channel signal need to be adjusted, the identification information of the first channel signal and the second channel signal may be one piece of identification information, and the identification information indicates that both the initial reverberation gain parameters of the first channel signal and the second channel signal need to be adjusted. Alternatively, the identification information of the first channel signal and the second channel signal may be two pieces of identification information, i.e., first identification information and second identification information, respectively, where the first identification information is used to indicate that the initial reverberation gain parameter of the first channel signal needs to be adjusted, and the second identification information is used to indicate that the initial reverberation gain parameter of the second channel signal needs to be adjusted. If a channel signal does not have corresponding identification information, it indicates that the initial reverberation gain parameter of the channel signal does not need to be adjusted. That is, if the identification information includes only the first identification information, the initial reverberation gain parameter of only the first channel signal in the first channel signal and the second channel signal needs to be adjusted.

[0187] Optionally, in some embodiments, if the initial reverberation gain parameter of the first channel signal needs to be adjusted, the method of FIG. 6 further includes the steps of determining a target attenuation coefficient based on the first difference value and the second difference value, where the target attenuation coefficient is used to adjust the initial reverberation gain parameter of the target channel signal, and quantizing the target attenuation coefficient and writing the quantized target attenuation coefficient to the bitstream.

[0188] The initial reverberation gain parameters of the channel signals may be flexibly adjusted based on the correlation value between the channel signals and the downmix signal by using the attenuation coefficients.

[0189] It should be understood that the first difference value and the second difference value may be calculated by reference to equations (1) and (2) above.

[0190] When the target damping coefficient is determined based on the first difference value and the second difference value, the target damping coefficient may be determined based on the ratio between the first difference value and the second difference value.

[0191] In some embodiments, the target attenuation coefficients include multiple attenuation coefficients, each of which corresponds to at least one subband of the target channel signal, and any subband corresponds to only one attenuation coefficient (e.g., a multi-channel signal may include multiple subbands, and adjacent subbands may correspond to one attenuation coefficient).

[0192] In addition, when the target attenuation coefficient includes multiple attenuation coefficients, the reverberation gain parameter can be adjusted more flexibly based on the target attenuation coefficient.

[0193] In some other embodiments, the target channel signal includes a first frequency band and a second frequency band, and an attenuation factor corresponding to a subband in the first frequency band is less than or equal to an attenuation factor corresponding to a subband in the second frequency band, and the frequency of the first frequency band is less than the frequency of the second frequency band.

[0194] The reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands can be adjusted to different degrees by setting different sizes of attenuation coefficients for the reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands, and can also obtain better processing effects during reverberation processing.

[0195] For example, the frequency band in which the target channel signal is located includes a low-frequency portion and a high-frequency portion, and the target attenuation coefficient includes a plurality of attenuation coefficients, where the low-frequency portion corresponds to at least one attenuation coefficient, the high-frequency portion corresponds to at least one attenuation coefficient, and the attenuation coefficient corresponding to the low-frequency portion is smaller than the attenuation coefficient corresponding to the high-frequency portion.

[0196] In some embodiments, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0197] The energy of the downmix signal can be calculated by using the energy of the first channel signal and the energy of the second channel signal, and the calculation process can be simplified without using the downmix signal itself.

[0198] The above describes in detail the encoding method in the embodiment of this application in relation to Fig. 6. The following describes the decoding method in the embodiment of this application in relation to Fig. 7. It should be understood that the decoding method in Fig. 7 corresponds to the encoding method in Fig. 6. For the sake of brevity, repeated descriptions will be omitted below as appropriate.

[0199] 7 is a schematic flowchart of a multi-channel signal decoding method according to an embodiment of the present application. The method of FIG. 7 may be performed by a decoder-side device or a decoder. The method of FIG. 7 specifically includes the following steps:

[0200] 710.Get bitstream.

[0201] 720. Determine, based on the bitstream, a downmix signal of a first channel signal and a second channel signal in the multi-channel signal, initial reverberation gain parameters of the first channel signal and the second channel signal, and identification information of the first channel signal and the second channel signal, where the identification information is used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted.

[0202] 730. Determine a channel signal, which is present in the first channel signal and the second channel signal and whose initial reverberation gain parameter needs to be adjusted, as a target channel signal based on the identification information.

[0203] 740. Adjust the initial reverberation gain parameter of the target channel signal.

[0204] In this application, by using the identification information, a channel signal whose initial reverberation gain parameter needs to be adjusted can be determined, and the initial reverberation gain parameter of the channel signal is adjusted before reverberation processing is performed on the channel signal, thereby improving the quality of the channel signal obtained after reverberation processing.

[0205] Optionally, in one embodiment, adjusting the initial reverberation gain parameters of the target channel signal includes determining a target attenuation coefficient and adjusting the initial reverberation gain parameters of the target channel signal based on the target attenuation coefficient to obtain target reverberation gain parameters of the target channel signal.

[0206] The initial reverberation gain parameters of the channel signals can be flexibly adjusted based on the magnitude of the correlation between the channel signals and the downmix signal by using the attenuation coefficients.

[0207] When determining the attenuation coefficient, the decoder side may determine the preset attenuation coefficient as the target attenuation coefficient, or the decoder side directly adjusts the initial reverberation gain parameter of the target channel signal based on the preset attenuation coefficient.

[0208] By presetting the attenuation factor, the process of determining the target attenuation factor can be simplified, thereby improving decoding efficiency.

[0209] In some embodiments, the decoder side may obtain the target attenuation coefficient from the bitstream of the multi-channel signal, i.e., obtain the target attenuation coefficient by decoding the bitstream of the multi-channel signal. In this case, the decoder side has determined the target attenuation coefficient, and encodes the target attenuation coefficient to obtain a bitstream and transmits it to the decoder side. In this way, the decoder side no longer needs to calculate the target attenuation coefficient, but directly decodes the bitstream to obtain the target attenuation coefficient.

[0210] If the bitstream includes the target attenuation coefficient, the target attenuation coefficient may be obtained directly from the bitstream, and the process of determining the target attenuation coefficient can also be simplified, thereby improving the decoding efficiency.

[0211] Optionally, in one embodiment, the step of determining the target attenuation coefficient specifically includes the steps of obtaining an inter-channel level difference between the first channel signal and the second channel signal from the bitstream, and determining the target attenuation coefficient based on the inter-channel level difference, or determining the target attenuation coefficient based on the inter-channel level difference and the downmix signal.

[0212] The target attenuation coefficient can be determined more flexibly and accurately based on the inter-channel level difference, the downmix signal, etc., so that the initial reverberation parameters of the channel signals can be adjusted more accurately based on the attenuation coefficient.

[0213] Specifically, when the inter-channel level difference is relatively large, it may be considered that the difference between the first channel signal and the second channel signal is relatively large and the correlation between the first channel signal and the second channel signal is relatively small, and in this case, a relatively large attenuation coefficient may be determined as the target attenuation coefficient.

[0214] In addition, when the target attenuation coefficient is determined based on the downmix signal, the target attenuation coefficient may be determined by using the periodicity and harmonics of the downmix signal. For example, when the periodicity or harmonics of the downmix signal is good, it may be considered that the difference between the first channel signal and the second channel signal is relatively small and the correlation between the first channel signal and the second channel signal is relatively large. In this case, an attenuation coefficient having a relatively small value may be determined as the target attenuation coefficient.

[0215] Optionally, in one embodiment, the target attenuation coefficient includes multiple attenuation coefficients, each of which corresponds to at least one subband of the target channel signal, and any subband corresponds to only one attenuation coefficient. For example, each of the first channel signal and the second channel signal may include multiple subbands, and multiple adjacent subbands may correspond to one attenuation coefficient.

[0216] In addition, when the target attenuation coefficient includes multiple attenuation coefficients, the reverberation gain parameter can be adjusted more flexibly based on the target attenuation coefficient.

[0217] In some other embodiments, the target channel signal includes a first frequency band and a second frequency band, and an attenuation factor corresponding to a subband in the first frequency band is less than or equal to an attenuation factor corresponding to a subband in the second frequency band, and the frequency of the first frequency band is less than the frequency of the second frequency band.

[0218] The reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands can be adjusted to different degrees by setting different sizes of attenuation coefficients for the reverberation gain parameters corresponding to the high frequency subbands and the low frequency subbands, and can also obtain better processing effects during reverberation processing.

[0219] For example, the frequency band in which the target channel signal is located includes a low-frequency portion and a high-frequency portion, and the target attenuation coefficient includes a plurality of attenuation coefficients, where the low-frequency portion corresponds to at least one attenuation coefficient, the high-frequency portion corresponds to at least one attenuation coefficient, and the attenuation coefficient corresponding to the low-frequency portion is smaller than the attenuation coefficient corresponding to the high-frequency portion.

[0220] The encoding method and decoding method in the embodiment of this application have been described in detail above with reference to Figures 3 to 7. The encoder and decoder in the embodiment of this application will be described below with reference to Figures 8 to 13. It should be understood that the encoder and decoder in Figures 8 to 13 can implement the steps performed by the encoder and decoder in the encoding method and decoding method in the embodiment of this application. For the sake of brevity, repeated descriptions will be omitted below as appropriate.

[0221] 8 is a schematic block diagram of an encoder according to an embodiment of the present application. The encoder 800 in FIG. 1. A processing unit 810 configured to determine a downmix signal of a first channel signal and a second channel signal of a multi-channel signal, initial reverberation gain parameters of the first channel signal and the second channel signal, a processing unit 810 further configured to determine target reverberation gain parameters for the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal, a correlation between the second channel signal and the down-mix signal, and an initial reverberation gain parameter; an encoding unit 820 configured to quantize the first channel signal and the second channel signal based on the downmix signal and the target reverberation gain parameter, and write the quantized first channel signal and the quantized second channel signal into a bitstream; Includes.

[0222] The encoder 800 may correspond to, and may perform, the multi-channel signal encoding method in FIG.

[0223] In this application, when the target reverberation gain parameter of the channel signal is determined, the correlation between the channel signal and the downmix signal is taken into consideration, so that a better processing effect can be obtained when reverberation processing is performed on the channel signal based on the target reverberation gain parameter, thereby improving the quality of the channel signal obtained after reverberation processing.

[0224] Optionally, in one embodiment, the processing unit 810 is specifically configured to determine a target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal, and adjust the initial reverberation gain parameter based on the target attenuation coefficient to obtain the target reverberation gain parameter.

[0225] Optionally, in one embodiment, each of the first channel signal and the second channel signal includes a plurality of frequency bins, and the processing unit 810 is specifically configured to determine difference values ​​between the energy of the first channel signal and the energy of the downmix signal at the plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal at the plurality of frequency bins, and to determine the target attenuation coefficient based on the difference values.

[0226] Optionally, in one embodiment, the processing unit 810 is specifically configured to determine a first difference value between the energy of the first channel signal and the energy of the down-mix signal, where the first difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in multiple frequency bins; the processing unit 810 is configured to determine a second difference value between the energy of the second channel signal and the energy of the down-mix signal, where the second difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in multiple frequency bins; and the processing unit 810 is configured to determine a target attenuation coefficient based on a ratio between the first difference value and the second difference value.

[0227] Optionally, in one embodiment, before determining the target damping coefficient based on the difference value, the processing unit 810 is more specifically configured to determine that the difference value is greater than a preset threshold.

[0228] Optionally, in one embodiment, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0229] Optionally, in one embodiment, the target attenuation coefficients include multiple attenuation coefficients, each of the multiple attenuation coefficients corresponding to at least one subband of the multiple channel signals, and any subband corresponding to only one attenuation coefficient.

[0230] 9 is a schematic block diagram of an encoder according to an embodiment of the present application. The encoder 900 in FIG. a processing unit 910 configured to determine a downmix signal of a first channel signal and a second channel signal of a multi-channel signal, initial reverberation gain parameters of the first channel signal and the second channel signal, a processing unit 910 further configured to determine identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal and a correlation between the second channel signal and the down-mix signal, the identification information being used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted; an encoding unit 920 configured to quantize the first channel signal and the second channel signal based on the downmix signal, the initial reverberation gain parameter, and the identification information, and write the quantized first channel signal and the quantized second channel signal into a bitstream; Includes.

[0231] In this application, the channel signals whose initial reverberation gain parameters need to be adjusted can be determined based on the correlation between the channel signals and the downmix signal, so that the decoder side can first adjust the initial reverberation gain parameters of some channel signals and then perform reverberation processing on these channel signals, thereby improving the quality of the channel signals obtained after reverberation processing.

[0232] It should be understood that the encoder 900 may correspond to and perform the multi-channel signal encoding method in FIG.

[0233] Optionally, in one embodiment, the processing unit 910 is specifically configured to determine identification information of the first channel signal and the second channel signal based on a correlation between the energy of the first channel signal and the energy of the down-mix signal and a correlation between the energy of the second channel signal and the energy of the down-mix signal.

[0234] Optionally, in one embodiment, the processing unit 910 is specifically configured to determine a first difference value and a second difference value, where the first difference value is a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal at multiple frequency bins, and the second difference value is a sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the down-mix signal at multiple frequency bins, and the processing unit 910 is specifically configured to determine identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value.

[0235] Optionally, in one embodiment, the processing unit 910 is specifically configured to: determine a larger difference value among the first difference value and the second difference value as a target difference value; and determine identification information based on the target difference value, wherein the identification information is specifically used to indicate a channel signal corresponding to the target difference value, and the channel signal corresponding to the target difference value is a channel signal whose initial reverberation gain parameter needs to be adjusted.

[0236] Optionally, in one embodiment, the processing unit 910 is more particularly configured to: determine a target attenuation coefficient based on the first difference value and the second difference value, the target attenuation coefficient being used to adjust an initial reverberation gain parameter of the target channel signal; and the processing unit 910 is more particularly configured to: quantize the target attenuation coefficient; and write the quantized target attenuation coefficient into the bitstream.

[0237] Optionally, in one embodiment, the target attenuation coefficients include multiple attenuation coefficients, each of the multiple attenuation coefficients corresponding to at least one subband of the target channel signal, and any subband corresponding to only one attenuation coefficient.

[0238] Optionally, in one embodiment, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0239] 10 is a schematic block diagram of a decoder according to an embodiment of the present application. The decoder 1000 in FIG. 10 includes: an acquisition unit 1010 configured to acquire a bitstream; a processing unit 1020 configured to determine, based on the bitstream, a downmix signal of a first channel signal and a second channel signal in the multi-channel signal, initial reverberation gain parameters of the first channel signal and the second channel signal, and identification information of the first channel signal and the second channel signal, where the identification information is used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted; Equipped with The processing unit 1020 is further configured to determine, based on the identification information, a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted as a target channel signal; The processing unit 1020 is further configured to adjust an initial reverberation gain parameter of the target channel signal.

[0240] In this application, by using the identification information, a channel signal whose initial reverberation gain parameter needs to be adjusted can be determined, and the initial reverberation gain parameter of the channel signal is adjusted before reverberation processing is performed on the channel signal, thereby improving the quality of the channel signal obtained after reverberation processing.

[0241] It should be understood that the decoder 1000 may correspond to and may perform the multi-channel signal decoding method in FIG.

[0242] Optionally, in one embodiment, the processing unit 1020 is specifically configured to determine a target attenuation coefficient, and adjust an initial reverberation gain parameter of the target channel signal based on the target attenuation coefficient to obtain a target reverberation gain parameter of the target channel signal.

[0243] Optionally, in one embodiment, the processing unit 1020 is specifically configured to determine a preset damping coefficient as the target damping coefficient.

[0244] Optionally, in one embodiment, the processing unit 1020 is specifically configured to obtain the target attenuation factor based on the bitstream.

[0245] Optionally, in one embodiment, the processing unit 1020 is specifically configured to obtain an inter-channel level difference between the first channel signal and the second channel signal from the bitstream, and determine a target attenuation coefficient based on the inter-channel level difference, or determine a target attenuation coefficient based on the inter-channel level difference and the downmix signal.

[0246] Optionally, in one embodiment, the target attenuation coefficients include multiple attenuation coefficients, each of the multiple attenuation coefficients corresponding to at least one subband of the target channel signal, and any subband corresponding to only one attenuation coefficient.

[0247] 11 is a schematic block diagram of an encoder according to an embodiment of the present application. The encoder 1100 in FIG. a memory 1110 configured to store a program; a processor 1120 configured to execute a program; When the program is executed, the processor 1120 is configured to: determine a down-mix signal of a first channel signal and a second channel signal in the multi-channel signal, initial reverberation gain parameters for the first channel signal and the second channel signal; determine target reverberation gain parameters for the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal, a correlation between the second channel signal and the down-mix signal, and the initial reverberation gain parameter; quantize the first channel signal and the second channel signal based on the down-mix signal and the target reverberation gain parameter; and write the quantized first channel signal and the quantized second channel signal to a bitstream.

[0248] The encoder 1100 may correspond to, and may perform, the multi-channel signal encoding method in FIG.

[0249] In this application, when the target reverberation gain parameter of the channel signal is determined, the correlation between the channel signal and the downmix signal is taken into consideration, so that a better processing effect can be obtained when reverberation processing is performed on the channel signal based on the target reverberation gain parameter, thereby improving the quality of the channel signal obtained after reverberation processing.

[0250] Optionally, in one embodiment, the processor 1120 is specifically configured to determine a target attenuation coefficient based on a correlation between the first channel signal and the downmix signal and a correlation between the second channel signal and the downmix signal, and adjust an initial reverberation gain parameter based on the target attenuation coefficient to obtain the target reverberation gain parameter.

[0251] Optionally, in one embodiment, each of the first channel signal and the second channel signal includes a plurality of frequency bins, and the processor 1120 is specifically configured to determine difference values ​​between the energy of the first channel signal and the energy of the downmix signal at the plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal at the plurality of frequency bins, and to determine the target attenuation coefficient based on the difference values.

[0252] Optionally, in one embodiment, the processor 1120 is specifically configured to determine a first difference value between the energy of the first channel signal and the energy of the downmix signal, where the first difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the downmix signal in a plurality of frequency bins; the processor 1120 is configured to determine a second difference value between the energy of the second channel signal and the energy of the downmix signal, where the second difference value is used to indicate a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the downmix signal in a plurality of frequency bins; and the processor 1120 is configured to determine a target attenuation coefficient based on a ratio between the first difference value and the second difference value.

[0253] Optionally, in one embodiment, before determining the target damping coefficient based on the difference value, the processor 1120 is more specifically configured to determine that the difference value is greater than a preset threshold.

[0254] Optionally, in one embodiment, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0255] Optionally, in one embodiment, the target attenuation coefficients include multiple attenuation coefficients, each of the multiple attenuation coefficients corresponding to at least one subband of the multiple channel signals, and any subband corresponding to only one attenuation coefficient.

[0256] 12 is a schematic block diagram of an encoder according to an embodiment of the present application. The encoder 1200 in FIG. a memory 1210 configured to store a program; a processor 1220 configured to execute a program; When the program is executed, the processor 1220 is configured to: determine a down-mix signal of a first channel signal and a second channel signal in the multi-channel signal, initial reverberation gain parameters for the first channel signal and the second channel signal, and determine identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal and a correlation between the second channel signal and the down-mix signal, wherein the identification information is used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted; and the processor 1220 is configured to quantize the first channel signal and the second channel signal based on the down-mix signal, the initial reverberation gain parameter, and the identification information, and write the quantized first channel signal and the quantized second channel signal to a bitstream.

[0257] In this application, the channel signals whose initial reverberation gain parameters need to be adjusted can be determined based on the correlation between the channel signals and the downmix signal, so that the decoder side can first adjust the initial reverberation gain parameters of some channel signals and then perform reverberation processing on these channel signals, thereby improving the quality of the channel signals obtained after reverberation processing.

[0258] It should be understood that the encoder 1200 may correspond to and perform the multi-channel signal encoding method in FIG.

[0259] Optionally, in one embodiment, the processor 1220 is specifically configured to determine identification information of the first channel signal and the second channel signal based on a correlation between the energy of the first channel signal and the energy of the downmix signal and a correlation between the energy of the second channel signal and the energy of the downmix signal.

[0260] Optionally, in one embodiment, the processor 1220 is specifically configured to determine a first difference value and a second difference value, where the first difference value is a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the downmix signal at a plurality of frequency bins, and the second difference value is a sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the downmix signal at a plurality of frequency bins, and the processor 1220 is configured to determine identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value.

[0261] Optionally, in one embodiment, the processor 1220 is configured to specifically determine a larger difference value among the first difference value and the second difference value as a target difference value, and to determine identification information based on the target difference value, where the identification information is specifically used to indicate a channel signal corresponding to the target difference value, and the channel signal corresponding to the target difference value is a channel signal whose initial reverberation gain parameter needs to be adjusted.

[0262] Optionally, in one embodiment, the processor 1220 is more specifically configured to determine a target attenuation coefficient based on the first difference value and the second difference value, the target attenuation coefficient being used to adjust an initial reverberation gain parameter of the target channel signal, and the processor 1220 is configured to quantize the target attenuation coefficient and write the quantized target attenuation coefficient to the bitstream.

[0263] Optionally, in one embodiment, the target attenuation coefficients include multiple attenuation coefficients, each of the multiple attenuation coefficients corresponding to at least one subband of the target channel signal, and any subband corresponding to only one attenuation coefficient.

[0264] Optionally, in one embodiment, the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

[0265] 13 is a schematic block diagram of a decoder according to an embodiment of the present application. The decoder 1300 in FIG. 13 includes: a memory 1310 configured to store a program; a processor 1320 configured to execute a program; When the program is executed, the processor 1320 is configured to acquire a bitstream, and determine, based on the bitstream, a downmix signal of a first channel signal and a second channel signal in the multi-channel signal, initial reverberation gain parameters of the first channel signal and the second channel signal, and identification information of the first channel signal and the second channel signal, wherein the identification information is used to indicate a channel signal, among the first channel signal and the second channel signal, whose initial reverberation gain parameter needs to be adjusted; and the processor 1320 is configured, based on the identification information, to determine, as a target channel signal, the channel signal, among the first channel signal and the second channel signal, whose initial reverberation gain parameter needs to be adjusted, and to adjust the initial reverberation gain parameters of the plurality of channel signals.

[0266] In this application, by using the identification information, a channel signal whose initial reverberation gain parameter needs to be adjusted can be determined, and the initial reverberation gain parameter of the channel signal is adjusted before reverberation processing is performed on the channel signal, thereby improving the quality of the channel signal obtained after reverberation processing.

[0267] It should be understood that the decoder 1300 may correspond to and perform the multi-channel signal decoding method in FIG.

[0268] Optionally, in one embodiment, the processor 1320 is specifically configured to determine a target attenuation coefficient and adjust an initial reverberation gain parameter of the target channel signal based on the target attenuation coefficient to obtain a target reverberation gain parameter of the target channel signal.

[0269] Optionally, in one embodiment, the processor 1320 is specifically configured to determine a preset damping coefficient as the target damping coefficient.

[0270] Optionally, in one embodiment, the processor 1320 is specifically configured to obtain the target attenuation factor based on the bitstream.

[0271] Optionally, in one embodiment, the processor 1320 is specifically configured to obtain an inter-channel level difference between the first channel signal and the second channel signal from the bitstream, and determine a target attenuation coefficient based on the inter-channel level difference, or to determine a target attenuation coefficient based on the inter-channel level difference and the downmix signal.

[0272] Optionally, in one embodiment, the target attenuation coefficients include multiple attenuation coefficients, each of the multiple attenuation coefficients corresponding to at least one subband of the target channel signal, and any subband corresponding to only one attenuation coefficient.

[0273] As will be appreciated by those skilled in the art, in combination with the example units and algorithm steps described in the embodiments disclosed in this specification, the embodiments may be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether a function is performed by hardware or software depends on the specific application and the design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be considered to go beyond the scope of this application.

[0274] For the sake of convenience and simplicity, in order to allow those skilled in the art to understand more clearly, the detailed working processes of the aforementioned systems, equipment, and units are referred to the corresponding processes in the aforementioned method embodiments, and therefore will not be described in detail again here.

[0275] In some embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods may be implemented in other ways. For example, the described device embodiments are merely examples. For example, the unit division is merely a logical functional division, and other divisions may be used in actual implementation. For example, multiple units or components may be combined or incorporated into other systems, or some features may be omitted or not implemented. Furthermore, the shown or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. Indirect couplings or communication connections between devices or units may be implemented in electronic, mechanical, or other forms.

[0276] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, and may be located in one location or distributed across multiple network units. Some or all of the units may be selected based on actual requirements to achieve the objectives of the solutions of the embodiments.

[0277] Furthermore, the functional units in the embodiments of this application may be integrated into a single processing unit, or each unit may exist physically alone, or two or more units may be integrated into a single unit.

[0278] When a function is implemented in the form of a software functional unit and sold or used as an independent product, the function may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, or a portion that contributes to the prior art, or a portion of the technical solution, may be implemented in the 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, etc.) to perform all or part of the steps of the method described in the embodiments of this application. The 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 disk.

[0279] The above description is merely a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any variations or replacements that can be easily conceived by those skilled in the art within the technical scope disclosed in this application shall fall within the scope of protection of this application. Therefore, the scope of protection of this application shall be limited to the scope of protection of the patent claims. [Explanation of symbols]

[0280] 800 encoder 810 Processing Unit 820 coding units 900 encoder 910 Processing Unit 920 coding units 1000 Decoder 1010 Acquisition Units 1020 Processing Unit 1100 encoder 1110 memory 1120 processor 1200 encoder 1210 memory 1220 processor 1300 encoder 1310 memory 1320 processor

Claims

1. determining a downmix signal of a first channel signal and a second channel signal in a multi-channel signal, and initial reverberation gain parameters for the first channel signal and the second channel signal; determining target reverberation gain parameters for the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal, a correlation between the second channel signal and the down-mix signal, and the initial reverberation gain parameter; quantizing the first channel signal and the second channel signal based on the downmix signal and the target reverberation gain parameter, and writing the quantized first channel signal and the quantized second channel signal into a bitstream; A multi-channel signal encoding method comprising:

2. determining target reverberation gain parameters for the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal, a correlation between the second channel signal and the down-mix signal, and the initial reverberation gain parameter, determining a target attenuation factor based on the correlation between the first channel signal and the down-mix signal and the correlation between the second channel signal and the down-mix signal; adjusting the initial reverberation gain parameters based on the target attenuation coefficients to obtain the target reverberation gain parameters; 2. The method of claim 1, comprising:

3. each of the first channel signal and the second channel signal includes a plurality of frequency bins, and the step of determining a target attenuation coefficient based on the correlation between the first channel signal and the downmix signal and the correlation between the second channel signal and the downmix signal includes: determining difference values ​​between the energy of the first channel signal and the energy of the downmix signal at the plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal at the plurality of frequency bins; determining the target damping coefficient based on the difference value; 3. The method of claim 2, comprising:

4. The step of determining difference values ​​between the energy of the first channel signal and the energy of the downmix signal in the plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal in the plurality of frequency bins comprises: determining a first difference value between the energy of the first channel signal and the energy of the down-mix signal, wherein the first difference value is used to indicate a sum of absolute values ​​of the difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in the plurality of frequency bins; determining a second difference value between the energy of the second channel signal and the energy of the down-mix signal, wherein the second difference value is used to indicate a sum of absolute values ​​of the difference values ​​between the energy of the second channel signal and the energy of the down-mix signal in the plurality of frequency bins; Including, The step of determining the target damping coefficient based on the difference value includes: determining the target damping coefficient based on a ratio between the first difference value and the second difference value; 4. The method of claim 3, comprising:

5. Prior to the step of determining the target damping coefficient based on the difference value, the method further comprises: determining that the difference value is greater than a preset threshold.

5. The method of claim 3 or 4, further comprising:

6. The method according to claim 3 , wherein the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

7. 7. The method of claim 2, wherein the target attenuation coefficients include a plurality of attenuation coefficients, each of the plurality of attenuation coefficients corresponding to at least one subband of the plurality of channel signals, and any subband corresponding to only one attenuation coefficient.

8. determining a downmix signal of a first channel signal and a second channel signal in a multi-channel signal, and initial reverberation gain parameters for the first channel signal and the second channel signal; determining identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal and a correlation between the second channel signal and the down-mix signal, the identification information being used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted; quantizing the first channel signal and the second channel signal based on the downmix signal, the initial reverberation gain parameter, and the identification information, and writing the quantized first channel signal and the quantized second channel signal into a bitstream; A multi-channel signal encoding method comprising:

9. determining identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal and a correlation between the second channel signal and the down-mix signal, determining the identification information of the first channel signal and the second channel signal based on a correlation between an energy of the first channel signal and an energy of the downmix signal and a correlation between an energy of the second channel signal and the energy of the downmix signal; 9. The method of claim 8, comprising:

10. determining the identification information of the first channel signal and the second channel signal based on a correlation between an energy of the first channel signal and an energy of the downmix signal and a correlation between an energy of the second channel signal and the energy of the downmix signal, determining a first difference value and a second difference value, wherein the first difference value is a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal at a plurality of frequency bins, and the second difference value is a sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the down-mix signal at the plurality of frequency bins; determining the identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value; 10. The method of claim 9, comprising:

11. determining the identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value, determining a larger difference value between the first difference value and the second difference value as a target difference value; determining the identification information based on the target difference value, the identification information being used to specifically indicate a channel signal corresponding to the target difference value, the channel signal corresponding to the target difference value being a channel signal whose initial reverberation gain parameter needs to be adjusted; 11. The method of claim 10, comprising:

12. The method comprises: determining a target attenuation factor based on the first difference value and the second difference value, the target attenuation factor being used to adjust an initial reverberation gain parameter of the target channel signal; quantizing the target attenuation coefficients and writing the quantized target attenuation coefficients into the bitstream; The method of claim 11 further comprising:

13. 13. The method of claim 12, wherein the target attenuation coefficients include a plurality of attenuation coefficients, each of the plurality of attenuation coefficients corresponding to at least one subband of the target channel signal, and any subband corresponding to only one attenuation coefficient.

14. The method according to any one of claims 9 to 13, wherein the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

15. obtaining a bitstream; determining, based on the bitstream, downmix signals of first and second channel signals in a multi-channel signal, initial reverberation gain parameters of the first and second channel signals, and identification information of the first and second channel signals, wherein the identification information is used to indicate channel signals in the first and second channel signals whose initial reverberation gain parameters need to be adjusted; determining, based on the identification information, a channel signal among the first channel signal and the second channel signal, the channel signal whose initial reverberation gain parameter needs to be adjusted, as a target channel signal; adjusting the initial reverberation gain parameter of the target channel signal; A multi-channel signal decoding method comprising:

16. said step of adjusting an initial reverberation gain parameter of said target channel signal comprising: determining a target damping coefficient; adjusting the initial reverberation gain parameter of the target channel signal based on the target attenuation coefficient to obtain a target reverberation gain parameter of the target channel signal; 16. The method of claim 15, comprising:

17. The step of determining a target damping coefficient comprises: determining a preset damping coefficient as the target damping coefficient; 17. The method of claim 16, comprising:

18. The step of determining a target damping coefficient comprises: obtaining the target attenuation factor based on the bitstream; 17. The method of claim 16, comprising:

19. The step of determining a target damping coefficient comprises: obtaining an inter-channel level difference between the first channel signal and the second channel signal from the bitstream; determining the target attenuation coefficient based on the inter-channel level difference; or determining the target attenuation coefficient based on the inter-channel level difference and the downmix signal; 17. The method of claim 16, comprising:

20. 20. The method of claim 16, wherein the target attenuation coefficients include a plurality of attenuation coefficients, each of the plurality of attenuation coefficients corresponding to at least one subband of the target channel signal, and any subband corresponding to only one attenuation coefficient.

21. 1. A processing unit configured to determine a downmix signal of a first channel signal and a second channel signal of a multi-channel signal, and initial reverberation gain parameters of the first channel signal and the second channel signal, the processing unit comprising: a processing unit further configured to determine target reverberation gain parameters for the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal, a correlation between the second channel signal and the down-mix signal, and the initial reverberation gain parameter; an encoding unit configured to quantize the first channel signal and the second channel signal based on the downmix signal and the target reverberation gain parameter, and write the quantized first channel signal and the quantized second channel signal into a bitstream; An encoder comprising:

22. The processing unit determining a target attenuation factor based on the correlation between the first channel signal and the down-mix signal and the correlation between the second channel signal and the down-mix signal; adjusting the initial reverberation gain parameter based on the target attenuation coefficient to obtain the target reverberation gain parameter; 22. The encoder of claim 21, specifically adapted to:

23. The first channel signal and the second channel signal each include a plurality of frequency bins, and the processing unit: determining difference values ​​between the energy of the first channel signal and the energy of the downmix signal at the plurality of frequency bins and between the energy of the second channel signal and the energy of the downmix signal at the plurality of frequency bins; determining the target damping coefficient based on the difference value; 23. The encoder of claim 22, specifically adapted to:

24. The processing unit specifically configured to determine a first difference value between the energy of the first channel signal and the energy of the downmix signal, the first difference value being used to indicate a sum of absolute values ​​of the difference values ​​between the energy of the first channel signal and the energy of the downmix signal in the plurality of frequency bins; specifically configured to determine a second difference value between the energy of the second channel signal and the energy of the down-mix signal, the second difference value being used to indicate a sum of absolute values ​​of the difference values ​​between the energy of the first channel signal and the energy of the down-mix signal in the plurality of frequency bins; specifically configured to determine the target damping coefficient based on a ratio between the first difference value and the second difference value.

24. The encoder of claim 23.

25. Before determining the target damping coefficient based on the difference value, the processing unit: determining that the difference value is greater than a preset threshold; 25. An encoder according to claim 23 or 24, further specifically adapted to:

26. 26. The encoder of claim 23, wherein the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

27. 27. The encoder of claim 22, wherein the target attenuation coefficients include a plurality of attenuation coefficients, each of the plurality of attenuation coefficients corresponding to at least one subband of the plurality of channel signals, and wherein any subband corresponds to only one attenuation coefficient.

28. 1. A processing unit configured to determine a downmix signal of a first channel signal and a second channel signal of a multi-channel signal, and initial reverberation gain parameters of the first channel signal and the second channel signal, the processing unit comprising: a processing unit further configured to determine identification information of the first channel signal and the second channel signal based on a correlation between the first channel signal and the down-mix signal and a correlation between the second channel signal and the down-mix signal, the identification information being used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted; an encoding unit configured to quantize the first channel signal and the second channel signal based on the downmix signal, the initial reverberation gain parameter, and the identification information, and write the quantized first channel signal and the quantized second channel signal into a bitstream; An encoder comprising:

29. The processing unit determining the identification information of the first channel signal and the second channel signal based on a correlation between an energy of the first channel signal and an energy of the downmix signal and a correlation between an energy of the second channel signal and the energy of the downmix signal; 29. The encoder of claim 28, specifically adapted to:

30. The processing unit determining a first difference value and a second difference value, wherein the first difference value is a sum of absolute values ​​of difference values ​​between the energy of the first channel signal and the energy of the down-mix signal at a plurality of frequency bins, and the second difference value is a sum of absolute values ​​of difference values ​​between the energy of the second channel signal and the energy of the down-mix signal at the plurality of frequency bins; determining the identification information of the first channel signal and the second channel signal based on the first difference value and the second difference value; 30. The encoder of claim 29, specifically adapted to:

31. The processing unit determining a larger difference value between the first difference value and the second difference value as a target difference value; determining the identification information based on the target difference value, the identification information being specifically used to indicate a channel signal corresponding to the target difference value, the channel signal corresponding to the target difference value being a channel signal whose initial reverberation gain parameter needs to be adjusted; 31. The encoder of claim 30, specifically adapted to:

32. The processing unit determining a target attenuation coefficient based on the first difference value and the second difference value, the target attenuation coefficient being used to adjust an initial reverberation gain parameter of the target channel signal; quantizing the target attenuation coefficients and writing the quantized target attenuation coefficients into the bitstream; 32. The encoder of claim 31 further configured to:

33. 33. The encoder of claim 32, wherein the target attenuation coefficients include a plurality of attenuation coefficients, each of the plurality of attenuation coefficients corresponding to at least one subband of the target channel signal, and wherein any subband corresponds to only one attenuation coefficient.

34. 34. The encoder of any one of claims 29 to 33, wherein the energy of the downmix signal is determined based on the energy of the first channel signal and the energy of the second channel signal.

35. an acquisition unit configured to acquire the bitstream; a processing unit configured to determine, based on a bitstream, a downmix signal of a first channel signal and a second channel signal in a multi-channel signal, initial reverberation gain parameters of the first channel signal and the second channel signal, and identification information of the first channel signal and the second channel signal, wherein the identification information is used to indicate a channel signal in the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted; Equipped with the processing unit is further configured to determine, based on the identification information, a channel signal of the first channel signal and the second channel signal whose initial reverberation gain parameter needs to be adjusted as a target channel signal; the processing unit is further configured to adjust the initial reverberation gain parameter of the target channel signal. Decoder.

36. The processing unit determining a target damping coefficient; adjusting the initial reverberation gain parameter of the target channel signal based on the target attenuation coefficient to obtain a target reverberation gain parameter of the target channel signal; 36. A decoder according to claim 35, specially adapted to:

37. The processing unit determining a preset damping coefficient as the target damping coefficient; 37. A decoder according to claim 36, specially adapted to:

38. The processing unit obtaining the target attenuation coefficient based on the bitstream; 37. A decoder according to claim 36, specially adapted to:

39. The processing unit obtaining an inter-channel level difference between the first channel signal and the second channel signal from the bitstream; determining the target attenuation coefficient based on the inter-channel level difference; or determining the target attenuation coefficient based on the inter-channel level difference and the downmix signal; 37. A decoder according to claim 36, specially adapted to:

40. 40. The decoder of claim 36, wherein the target attenuation coefficients include a plurality of attenuation coefficients, each of the plurality of attenuation coefficients corresponding to at least one subband of the target channel signal, and any subband corresponding to only one attenuation coefficient.

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