Method for decoding stereo signals, device for decoding stereo signals, computer-readable storage medium, and computer program

Abstract

The present invention provides a stereo signal encoding method and apparatus, as well as a stereo signal decoding method and apparatus, that can reduce the number of bits required for encoding. [Solution] The encoding method includes the steps of: performing spread spectrum on the quantized LSF parameters of the primary channel signal in the current frame of the stereo signal to obtain the spread spectrum LSF parameters of the primary channel signal (S510); determining the predicted residual of the LSF parameters of the secondary channel signal in the current frame based on the original LSF parameters of the secondary channel signal and the spread spectrum LSF parameters of the primary channel signal (S520); and performing quantization on the predicted residual of the LSF parameters of the secondary channel signal (S530).

Description

Technical Field

[0001] This application claims the priority of Chinese Patent Application No. 201810701919.1, entitled "Stereo Signal Encoding Method and Apparatus, and Stereo Signal Decoding Method and Apparatus", filed with the China Patent Office on June 29, 2018, which is incorporated herein by reference in its entirety.

[0002] This application relates to the field of audio, and more specifically, to a stereo signal encoding method and apparatus, and a stereo signal decoding method and apparatus.

Background Art

[0003] In a time-domain stereo encoding / decoding method, on the encoder side, first, an inter-channel time difference estimation is performed on the stereo signal, time alignment is performed based on the estimation result, then time-domain downmixing is performed on the time-aligned signal, and finally, the primary channel signal and the secondary channel signal obtained after downmixing are separately encoded to obtain an encoded bitstream.

[0004] The encoding of the primary channel signal and the secondary channel signal may include determining the linear prediction coefficient (LPC) of the primary channel signal and the LPC of the secondary channel signal, respectively converting the LPC of the primary channel signal and the LPC of the secondary channel signal into the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal, and then performing quantization on the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal.

[0005] The process of performing quantization on the LSF parameters of the primary channel signal and the secondary channel signal may include: quantizing the original LSF parameters of the primary channel signal to obtain the quantized LSF parameters of the primary channel signal; performing a reuse determination based on the distance between the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal; determining that if the distance between the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal is greater than or equal to a threshold, the LSF parameters of the secondary channel signal do not meet the reuse condition and the original LSF parameters of the secondary channel signal need to be quantized to obtain the quantized LSF parameters of the secondary channel signal; and writing the quantized LSF parameters of the primary channel signal and the quantized LSF parameters of the secondary channel signal to the bitstream. If the distance between the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal is less than the threshold, only the quantized LSF parameters of the primary channel signal are written to the bitstream. In this case, the quantized LSF parameters of the primary channel signal may be used as the quantized LSF parameters of the secondary channel signal.

[0006] In this encoding process, if the LSF parameters of the secondary channel signal do not meet the reuse conditions, both the quantized LSF parameters of the primary channel signal and the quantized LSF parameters of the secondary channel signal must be written to the bitstream. Therefore, a relatively large number of bits are required for encoding. [Overview of the Initiative]

[0007] This invention provides a stereo signal coding method and apparatus, and a stereo signal decoding method and apparatus, which helps reduce the number of bits required for coding when the LSF parameter of the secondary channel signal does not satisfy the reuse conditions.

[0008] According to a first aspect, the present invention provides a stereo signal coding method. The coding method comprises the steps of: performing spread spectrum on the quantized LSF parameters of the primary channel signal in the current frame of a stereo signal to obtain the spread spectrum LSF parameters of the primary channel signal; determining the predicted residual of the LSF parameters of the secondary channel signal in the current frame based on the original LSF parameters of the secondary channel signal and the spread spectrum LSF parameters of the primary channel signal; and performing quantization on the predicted residual of the LSF parameters of the secondary channel signal.

[0009] In the encoding method, spread spectrum is first performed on the quantized LSF parameters of the primary channel signal. Then, the predicted residuals of the secondary channel signal are determined based on the spread spectrum LSF parameters and the original LSF parameters of the secondary channel signal, and quantization is performed on the predicted residuals. The value of the predicted residuals is smaller than the value of the LSF parameters of the secondary channel signal, and the order of magnitude of the value of the predicted residuals is smaller than the order of magnitude of the value of the LSF parameters of the secondary channel signal. Therefore, performing quantization on the predicted residuals helps reduce the number of bits required for encoding compared to performing quantization separately on the LSF parameters of the secondary channel signal.

[0010] In relation to the first aspect, in a first possible implementation, the step of performing spread spectrum on the quantized LSF parameters of the primary channel signal in the current frame of the stereo signal to obtain the spread spectrum LSF parameters of the primary channel signal includes the step of performing an average extension process on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters, the average extension process is performed according to the following equation.

number

[0011] Here,

number

number

number

[0012] In relation to the first aspect, in a second possible implementation, the step of performing spread spectrum on the quantized LSF parameters of the primary channel signal in the current frame of a stereo signal to obtain spread spectrum LSF parameters of the primary channel signal includes the steps of: converting the quantized LSF parameters of the primary channel signal into linear prediction coefficients; modifying the linear prediction coefficients to obtain modified linear prediction coefficients of the primary channel signal; and converting the modified linear prediction coefficients of the primary channel signal into LSF parameters, wherein the LSF parameters obtained through the conversion are spread spectrum LSF parameters of the primary channel signal.

[0013] In the first embodiment, or in a third possible implementation relating to the first or second possible implementation, the predicted residual of the LSF parameter of the secondary channel signal is the difference between the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal.

[0014] In the first embodiment, or in relation to the first or second possible implementation, in the fourth possible implementation, the step of determining the predicted residual of the LSF parameter of the secondary channel signal in the current frame based on the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal includes the steps of: performing a two-stage prediction on the LSF parameter of the secondary channel signal based on the spread spectrum LSF parameter of the primary channel signal to obtain the predicted LSF parameter of the secondary channel signal; and using the difference between the original LSF parameter of the secondary channel signal and the predicted LSF parameter as the predicted residual of the secondary channel signal.

[0015] In the first embodiment, or in a fifth possible implementation relating to any one of the possible implementations described above, prior to the step of determining the predicted residual of the LSF parameter of the secondary channel signal in the current frame based on the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal, the encoding method further includes a step of determining that the LSF parameter of the secondary channel signal does not satisfy the reuse condition.

[0016] Whether the LSF parameters of the secondary channel signal do not meet the reuse conditions can be determined according to the prior art, for example, the methods described in the background art.

[0017] According to a second aspect, the present application provides a stereo signal decoding method. The decoding method includes obtaining quantized LSF parameters of a primary channel signal in a current frame from a bitstream; performing spectral spreading on the quantized LSF parameters of the primary channel signal to obtain spectral spread LSF parameters of the primary channel signal; obtaining a prediction residual of LSF parameters of a secondary channel signal in the current frame in the stereo signal from the bitstream; and determining quantized LSF parameters of the secondary channel signal based on the prediction residual of the LSF parameters of the secondary channel signal and the spectral spread LSF parameters of the primary channel signal.

[0018] In the decoding method, the quantized LSF parameters of the secondary channel signal may be determined based on the prediction residual of the secondary channel signal and the quantized LSF parameters of the primary channel signal. Therefore, the quantized LSF parameters of the secondary channel signal may not need to be recorded in the bitstream, but the prediction residual of the secondary channel signal is recorded. This helps to reduce the number of bits required for encoding.

[0019] In relation to the second aspect, in a first possible implementation, the step of performing spectral spreading on the quantized LSF parameters of the primary channel signal in the current frame in the stereo signal to obtain spectral spread LSF parameters of the primary channel signal includes performing an average elongation process on the quantized LSF parameters of the primary channel signal to obtain spectral spread LSF parameters of the primary channel signal, and the average elongation process is performed according to the following formula.

Number

[0020] Here,

Number

number

number

[0021] In relation to the second aspect, in a second possible implementation, the step of performing spread spectrum on the quantized LSF parameters of the primary channel signal in the current frame of a stereo signal to obtain spread spectrum LSF parameters of the primary channel signal includes the steps of: converting the quantized LSF parameters of the primary channel signal into linear prediction coefficients; modifying the linear prediction coefficients to obtain modified linear prediction coefficients of the primary channel signal; and converting the modified linear prediction coefficients of the primary channel signal into LSF parameters, wherein the LSF parameters obtained through the conversion are spread spectrum LSF parameters of the primary channel signal.

[0022] In the second embodiment, or in a third possible implementation relating to the first or second possible implementation, the quantized LSF parameter of the secondary channel signal is the sum of the spread spectrum LSF parameter and the prediction residual.

[0023] In a second embodiment, or in relation to a first or second possible implementation, in a fourth possible implementation, the step of determining the quantized LSF parameter of the secondary channel signal based on the predicted residual of the LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal includes the steps of performing a two-stage prediction on the LSF parameter of the secondary channel signal based on the spread spectrum LSF parameter of the primary channel signal to obtain the predicted LSF parameter, and using the sum of the predicted LSF parameter and the predicted residual as the quantized LSF parameter of the secondary channel signal.

[0024] According to a third aspect, a stereo signal encoding device is provided. The encoding device includes a module configured to perform an encoding method according to the first aspect or one of possible implementations of the first aspect.

[0025] According to a fourth aspect, a stereo signal decoding device is provided. The decoding device includes a module configured to perform a method according to the second aspect, or any one of possible implementations of the second aspect.

[0026] According to a fifth aspect, a stereo signal encoding device is provided. The encoding device includes memory and a processor. The memory is configured to store a program. The processor is configured to execute the program. When the program is executed in memory, the processor implements an encoding method according to the first aspect or any one of the possible implementations of the first aspect.

[0027] According to a sixth aspect, a stereo signal decoding device is provided. The decoding device includes memory and a processor. The memory is configured to store a program. The processor is configured to execute the program. When the program is executed in memory, the processor implements a decoding method according to a second aspect or one of possible implementations of a second aspect.

[0028] According to the seventh aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores program code to be executed by a device or apparatus, the program code including instructions used to implement an encoding method according to the first aspect or any one of possible implementations thereof.

[0029] According to the eighth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores program code to be executed by a device or apparatus, the program code including instructions used to implement a decoding method according to the second aspect or any one of possible implementations of the second aspect.

[0030] According to the ninth aspect, a chip is provided. The chip includes a processor and a communication interface. The communication interface is configured to communicate with an external device. The processor is configured to implement an encoding method according to the first aspect, or any one of possible implementations of the first aspect.

[0031] Optionally, the chip may further include memory. The memory stores instructions. The processor is configured to execute instructions stored in memory. When an instruction is executed, the processor is configured to implement an encoding method according to the first embodiment or one of the possible implementations of the first embodiment.

[0032] Optionally, the chip can be integrated into a terminal device or a network device.

[0033] According to the tenth aspect, a chip is provided. The chip includes a processor and a communication interface. The communication interface is configured to communicate with an external device. The processor is configured to implement a decoding method according to the second aspect, or any one of possible implementations of the second aspect.

[0034] Optionally, the chip may further include memory. The memory stores instructions. The processor is configured to execute instructions stored in memory. When an instruction is executed, the processor is configured to implement a decoding method according to a second embodiment, or one of the possible implementations of the second embodiment.

[0035] Optionally, the chip can be integrated into a terminal device or a network device.

[0036] According to the eleventh aspect, an embodiment of the present application provides a computer program product including instructions. When the computer program product runs on a computer, the computer is able to perform an encoding method according to the first aspect.

[0037] According to a twelfth aspect, an embodiment of the present application provides a computer program product including instructions. When the computer program product is running on a computer, the computer is able to perform a decoding method according to a second aspect. [Brief explanation of the drawing]

[0038] [Figure 1] This is a schematic diagram of a stereo coding and decoding system in the time domain according to one embodiment of the present invention.

[0039] [Figure 2] This is a schematic diagram of a mobile terminal according to one embodiment of the present invention.

[0040] [Figure 3] This is a schematic diagram of a network element according to one embodiment of the present invention.

[0041] [Figure 4] This is a schematic flowchart illustrating how to perform quantization on the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal.

[0042] [Figure 5] This is a schematic flowchart of a stereo signal coding method according to one embodiment of the present invention.

[0043] [Figure 6] This is a schematic flowchart of a stereo signal coding method according to one embodiment of the present invention.

[0044] [Figure 7] This is a schematic flowchart of a stereo signal coding method according to one embodiment of the present invention.

[0045] [Figure 8] This is a schematic flowchart of a stereo signal coding method according to one embodiment of the present invention.

[0046] [Figure 9] This is a schematic flowchart of a stereo signal coding method according to one embodiment of the present invention.

[0047] [Figure 10] This is a schematic flowchart of a stereo signal decoding method according to one embodiment of the present invention.

[0048] [Figure 11] This is a schematic diagram of a stereo signal encoding device according to one embodiment of the present invention.

[0049] [Figure 12] This is a schematic diagram of a stereo signal decoding device according to one embodiment of the present invention.

[0050] [Figure 13] This is a schematic diagram of a stereo signal encoding device according to another embodiment of the present invention.

[0051] [Figure 14] This is a schematic diagram of a stereo signal decoding device according to another embodiment of the present invention.

[0052] [Figure 15] This is a schematic diagram of the linearly predicted spectral envelopes of the primary channel signal and the secondary channel signal. [Modes for carrying out the invention]

[0053] Figure 1 is a schematic diagram of a stereo coding and decoding system in the time domain according to an exemplary embodiment of the present application. The stereo coding and decoding system includes a coding component 110 and a decoding component 120.

[0054] It should be understood that the stereo signal in this application may be the original stereo signal, a stereo signal containing two signals included in signals on multiple channels, or a stereo signal containing two signals co-generated from multiple signals included in signals on multiple channels.

[0055] The encoding component 110 is configured to encode a stereo signal in the time domain. Optionally, the encoding component 110 may be implemented in software, hardware, or a combination of software and hardware, but is not limited to the embodiments of this application.

[0056] The encoding of a stereo signal in the time domain by the encoding component 110 may include the following steps:

[0057] (1) Time-domain preprocessing is performed on the acquired stereo signal to obtain the time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal.

[0058] The stereo signal can be collected by the acquisition component and transmitted to the encoding component 110. Optionally, the acquisition component and the encoding component 110 may be located in the same device. Alternatively, the acquisition component and the encoding component 110 may be located in different devices.

[0059] The time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal are the signals on the two channels in the preprocessed stereo signal.

[0060] Optionally, time-domain preprocessing may include at least one of high-pass filtering, pre-emphasis, sampling rate conversion, and channel switching, but is not limited to the embodiments of this application.

[0061] (2) Time estimation is performed based on the time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal to obtain the inter-channel time difference between the time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal.

[0062] For example, the cross-correlation function between the left channel signal and the right channel signal can be calculated based on the time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal. Next, the maximum value of the cross-correlation function is sought, and this maximum value is used as the inter-channel time difference between the time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal.

[0063] As another example, the cross-correlation function between the left and right channel signals can be calculated based on the time-domain preprocessed left and right channel signals. Then, based on the cross-correlation function between the left and right channel signals in each of the L frames (where L is an integer greater than or equal to 1) preceding the current frame, long-term smoothing is performed on the cross-correlation function between the left and right channel signals in the current frame to obtain the smoothed cross-correlation function. Subsequently, the maximum value of the smoothed cross-correlation function is found, and the index value corresponding to the maximum value is used as the inter-channel time difference between the time-domain preprocessed left and right channel signals in the current frame.

[0064] As another example, based on the inter-channel time difference in the M frames preceding the current frame (where M is an integer greater than or equal to 1), inter-frame smoothing may be performed on the estimated inter-channel time difference in the current frame, and the smoothed inter-channel time difference is used as the final inter-channel time difference between the time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal in the current frame.

[0065] The above-described method for estimating inter-channel time differences is merely an example, and it should be understood that the embodiments of this application are not limited to the above-described method for estimating inter-channel time differences.

[0066] (3) Based on the inter-channel time difference, time alignment is performed on the time-domain preprocessed left channel signal and the time-domain preprocessed right channel signal to obtain the time-aligned left channel signal and the time-aligned right channel signal.

[0067] For example, based on the estimated inter-channel time difference in the current frame and the inter-channel time difference in the previous frame, one or two signals in the left channel signal and right channel signal in the current frame may be compressed or decompressed so that there is no inter-channel time difference between the time-aligned left channel signal and the time-aligned right channel signal.

[0068] (4) Encode the inter-channel time difference and obtain the encoded index of the inter-channel time difference.

[0069] (5) Calculate the stereo parameters for the time-domain downmix, encode the stereo parameters for the time-domain downmix, and obtain the encoded index of the stereo parameters for the time-domain downmix.

[0070] The stereo parameters for time-domain downmixing are used to perform time-domain downmixing on the time-aligned left channel signal and the time-aligned right channel signal.

[0071] (6) Based on the stereo parameters for the time-domain downmix, a time-domain downmix is ​​performed on the time-aligned left channel signal and the time-aligned right channel signal to obtain the primary channel signal and the secondary channel signal.

[0072] The primary channel signal is used to represent the relationship between channels and may also be called the downmixed signal or the central channel signal. The secondary channel signal is used to represent the difference between channels and may also be called the residual signal or the side channel signal.

[0073] When the time-aligned left channel signal and the time-aligned right channel signal are matched in the time domain, the secondary channel signal is the weakest. In this case, the stereo signal has the best effect.

[0074] (7) The primary channel signal and the secondary channel signal are encoded separately to obtain a first mono encoded bitstream corresponding to the primary channel signal and a second mono encoded bitstream corresponding to the secondary channel signal.

[0075] (8) Write the encoded index of the inter-channel time difference, the encoded index of the stereo parameters, the first mono encoded bitstream, and the second mono encoded bitstream to the stereo encoded bitstream.

[0076] It should be noted that not all of the above steps are mandatory. For example, step (1) is not mandatory. If step (1) is absent, the left and right channel signals used for time estimation may be the left and right channel signals in the original stereo signal. In this specification, the left and right channel signals in the original stereo signal are the signals acquired after acquisition and analog-to-digital (A / D) conversion.

[0077] The decoding component 120 is configured to decode the stereo encoded bitstream generated by the encoding component 110 to obtain a stereo signal.

[0078] Optionally, the encoding component 110 may be connected to the decoding component 120 by wire or wireless means, and the decoding component 120 may obtain the stereo encoded bitstream generated by the encoding component 110 through the connection between the decoding component 120 and the encoding component 110. Alternatively, the encoding component 110 may store the generated stereo encoded bitstream in memory, and the decoding component 120 may read the stereo encoded bitstream from memory.

[0079] The decoding component 120 may optionally be implemented in software, hardware, or a combination of software and hardware. This is not limited to the embodiments of the present application.

[0080] The process by which the decoding component 120 decodes the stereo encoded bitstream to obtain a stereo signal may include the following steps:

[0081] (1) The first mono encoded bitstream and the second mono encoded bitstream in the stereo encoded bitstream are decoded to obtain the primary channel signal and the secondary channel signal.

[0082] (2) Based on the stereo encoded bitstream, obtain the encoded index of the stereo parameters for the time-domain upmix, and perform the time-domain upmix on the primary and secondary channel signals to obtain the time-domain upmixed left channel signal and the time-domain upmixed right channel signal.

[0083] (3) Based on the stereo encoded bitstream, the encoded index of the inter-channel time difference is obtained, and execution time adjustments are performed on the time-domain upmixed left channel signal and the time-domain upmixed right channel signal to obtain the stereo signal.

[0084] Optionally, the encoding component 110 and the decoding component 120 may be located on the same device or on different devices. The device may be a mobile terminal with audio signal processing capabilities, such as a mobile phone, tablet computer, laptop portable computer, desktop computer, Bluetooth® soundbox, recording pen, or wearable device, or it may be a network element with audio signal processing capabilities in a core network or wireless network. This is not limited to the embodiments of the present application.

[0085] For example, as shown in Figure 2, the following example is used to provide the explanation. The encoding component 110 is located in the mobile terminal 130. The decoding component 120 is located in the mobile terminal 140. Mobile terminals 130 and 140 are independent electronic devices with voice signal processing capabilities. For example, each of mobile terminals 130 and 140 could be a mobile phone, a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, etc. In addition, mobile terminal 130 is connected to mobile terminal 140 via a wireless or wired network.

[0086] Optionally, the mobile terminal 130 may include a collection component 131, an encoding component 110, and a channel encoding component 132. The collection component 131 is connected to the encoding component 110, and the encoding component 110 is connected to the encoding component 132.

[0087] Optionally, the mobile terminal 140 may include an audio playback component 141, a decoding component 120, and a channel decoding component 142. The audio playback component 141 is connected to the decoding component 120, and the decoding component 120 is connected to the channel decoding component 142.

[0088] After acquiring a stereo signal using the acquisition component 131, the mobile terminal 130 uses the encoding component 110 to encode the stereo signal and obtain a stereo encoded bitstream. Next, the mobile terminal 130 uses the channel encoding component 132 to encode the stereo encoded bitstream and obtain a transmission signal.

[0089] Mobile terminal 130 transmits a transmission signal to mobile terminal 140 via a wireless or wired network.

[0090] After receiving the transmission signal, the mobile terminal 140 decodes the transmission signal using the channel decoding component 142 to obtain a stereo encoded bitstream, decodes the stereo encoded bitstream using the decoding component 120 to obtain a stereo signal, and plays the stereo signal using the audio playback component 141.

[0091] For example, in describing this embodiment of the present application, we use an example in which the encoding component 110 and the decoding component 120 are located on the same network element 150 having voice signal processing capabilities in a core network or wireless network, as shown in Figure 3.

[0092] Optionally, the network element 150 includes a channel decoding component 151, a decoding component 120, an encoding component 110, and a channel encoding component 152. The channel decoding component 151 is connected to the decoding component 120, the decoding component 120 is connected to the encoding component 110, and the encoding component 110 is connected to the channel encoding component 152.

[0093] The channel decoding component 151 receives a transmission signal sent by another device, decodes the transmission signal, and obtains a first stereo encoded bitstream. The decoding component 120 decodes the stereo encoded bitstream and obtains a stereo signal. The encoding component 110 encodes the stereo signal and obtains a second stereo encoded bitstream. The channel encoding component 152 encodes the second stereo encoded bitstream and obtains a transmission signal.

[0094] The other device may be a mobile terminal with voice signal processing capabilities, or another network element with voice signal processing capabilities. This is not limited to the embodiments of the present application.

[0095] Optionally, the encoding component 110 and decoding component 120 in the network element may transcode a stereo encoded bitstream transmitted by a mobile terminal.

[0096] Optionally, in the embodiments of this application, the device on which the encoding component 110 is located may be referred to as an audio encoding device. In actual implementations, the audio encoding device may also have an audio decoding function, although this is not limited to the embodiments of this application.

[0097] Optionally, in the embodiments of this application, only stereo signals are used as illustrative examples. In this application, the audio coding device may further process multichannel signals, the multichannel signals comprising at least two channel signals.

[0098] The coding component 110 can encode the primary channel signal and the secondary channel signal by using the algebraic code excited linear prediction (ACELP) coding method.

[0099] The ACELP coding method typically includes determining the LPC coefficients of the primary channel signal and the LPC coefficients of the secondary channel signal, converting each of the LPC coefficients of the primary channel signal and the LPC coefficients of the secondary channel signal into LSF parameters, performing quantization on the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal, searching for adaptive code excitation to determine the pitch period and adaptive codebook gain, performing quantization separately on the pitch period and adaptive codebook gain, and searching for algebraic code excitation to determine the pulse index and gain of the algebraic code excitation, and performing quantization separately on the pulse index and gain of the algebraic code excitation.

[0100] Figure 4 illustrates an exemplary method by which the coding component 110 performs quantization on the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal.

[0101] S410: Determine the original LSF parameters of the primary channel signal based on the primary channel signal.

[0102] S420: Determine the original LSF parameters of the secondary channel signal based on the secondary channel signal.

[0103] There is no execution order between stage S410 and stage S420.

[0104] S430: Based on the original LSF parameters of the primary channel signal and the original LSF parameters of the secondary channel signal, it is determined whether the LSF parameters of the secondary channel signal satisfy the reuse criteria. The reuse criteria may also be simply referred to as the reuse conditions.

[0105] If the LSF parameters of the secondary channel signal do not meet the reuse criteria, step S440 is executed. If the LSF parameters of the secondary channel signal meet the reuse criteria, step S450 is executed.

[0106] Reuse means that the quantized LSF parameters of the secondary channel signal can be obtained based on the quantized LSF parameters of the primary channel signal. For example, the quantized LSF parameters of the primary channel signal are used as the quantized LSF parameters of the secondary channel signal. In other words, the quantized LSF parameters of the primary channel signal are reused as the quantized LSF parameters of the secondary channel signal.

[0107] Determining whether the LSF parameter of a secondary channel signal satisfies the reuse criteria can be referred to as performing a reuse determination on the LSF parameter of a secondary channel signal.

[0108] For example, if the reuse determination condition is that the distance between the original LSF parameters of the primary channel signal and the original LSF parameters of the secondary channel signal is less than or equal to a preset threshold, then if the distance between the original LSF parameters of the primary channel signal and the original LSF parameters of the secondary channel signal is greater than the preset threshold, then the LSF parameters of the secondary channel signal are determined not to satisfy the reuse determination condition. Alternatively, if the distance between the original LSF parameters of the primary channel signal and the original LSF parameters of the secondary channel signal is less than or equal to a preset threshold, then the LSF parameters of the secondary channel signal may be determined to satisfy the reuse determination condition.

[0109] It should be understood that the criteria used in the above-mentioned reuse determination are merely examples and are not limited to the present invention.

[0110] The distance between the LSF parameter of the primary channel signal and the LSF parameter of the secondary channel signal can be used to represent the difference between the LSF parameter of the primary channel signal and the LSF parameter of the secondary channel signal.

[0111] The distance between the LSF parameter of the primary channel signal and the LSF parameter of the secondary channel signal can be calculated using several methods.

[0112] For example, the distance between the LSF parameter of the primary channel signal and the LSF parameter of the secondary channel signal.

number

number

[0113] Here,

number

number

[0114]

number

[0115] Performing a reuse decision on the original LSF parameters of a secondary channel signal can also be referred to as performing a quantization decision on the LSF parameters of a secondary channel signal. If the decision result is to quantize the LSF parameters of the secondary channel signal, the original LSF parameters of the secondary channel signal can be quantized and written to the bitstream, and the quantized LSF parameters of the secondary channel signal can be obtained.

[0116] The determination result at this stage can be written to a bitstream and sent to the decoder.

[0117] S440: The original LSF parameters of the secondary channel signal are quantized to obtain the quantized LSF parameters of the secondary channel signal, and the LSF parameters of the primary channel signal are quantized to obtain the quantized LSF parameters of the primary channel signal.

[0118] It should be understood that directly using the quantized LSF parameters of the primary channel signal as the quantized LSF parameters of the secondary channel signal is merely an example, provided that the LSF parameters of the secondary channel signal satisfy the reuse criteria. Naturally, the quantized LSF parameters of the primary channel signal can be reused by other means to obtain the quantized LSF parameters of the secondary channel signal, and this is not limited to this embodiment of the present application.

[0119] S450: If the LSF parameters of the secondary channel signal satisfy the reuse criteria, the quantized LSF parameters of the primary channel signal are used directly as the quantized LSF parameters of the secondary channel signal.

[0120] The original LSF parameters of the primary channel signal and the original LSF parameters of the secondary channel signal are quantized separately and written to a bitstream to obtain the quantized LSF parameters of the primary channel signal and the quantized LSF parameters of the secondary channel signal. In this case, a relatively large number of bits are occupied.

[0121] Figure 5 is a schematic flowchart of a stereo signal coding method according to one embodiment of the present invention. If the reuse determination result indicates that the reuse determination condition is not met, the coding component 110 may perform the method shown in Figure 5.

[0122] S510: Perform spread spectrum on the quantized LSF parameters of the primary channel signal in the current frame of the stereo signal to obtain the spread spectrum LSF parameters of the primary channel signal.

[0123] S520: Based on the original LSF parameters of the secondary channel signal and the spread spectrum LSF parameters of the primary channel signal, the predicted residual of the LSF parameters of the secondary channel signal in the current frame is determined.

[0124] As shown in Figure 15, there is similarity between the linearly predicted spectral envelope of the primary channel signal and the linearly predicted spectral envelope of the secondary channel signal. The linearly predicted spectral envelope is represented by LPC coefficients, which can be converted to LSF parameters. Therefore, there is similarity between the LSF parameters of the primary channel signal and the LSF parameters of the secondary channel signal. Thus, determining the predicted residuals of the LSF parameters of the secondary channel signal based on the spread spectrum LSF parameters of the primary channel signal helps improve the accuracy of the predicted residuals.

[0125] The original LSF parameters of the secondary channel signal can be understood as the LSF parameters obtained based on the secondary channel signal using methods in the prior art, for example, the original LSF parameters obtained in S420.

[0126] Determining the predicted residual of the LSF parameter of the secondary channel signal based on the original LSF parameter of the secondary channel signal and the predicted LSF parameter of the secondary channel signal may involve using the difference between the original LSF parameter of the secondary channel signal and the predicted LSF parameter of the secondary channel signal as the predicted residual of the LSF parameter of the secondary channel signal.

[0127] S530: Perform quantization on the predicted residual of the LSF parameter of the secondary channel signal.

[0128] S540: Perform quantization on the quantized LSF parameters of the primary channel signal.

[0129] In the encoding method of this embodiment, if the LSF parameters of the secondary channel signal need to be encoded, quantization is performed on the predicted residual of the LSF parameters of the secondary channel signal. Compared to a method in which the LSF parameters of the secondary channel signal are encoded separately, this method helps to reduce the number of bits required for encoding.

[0130] In addition, the LSF parameters of the secondary channel signal, which are used to determine the predicted residuals, are obtained through predictions based on LSF parameters acquired after spread spectrum has been performed on the quantized LSF parameters of the primary channel signal. Therefore, similar features can be used between the linear predicted spectral envelope of the primary channel signal and the linear predicted spectral envelope of the secondary channel signal. This helps to improve the accuracy of the predicted residuals compared to the quantized LSF parameters of the primary channel signal, and helps to improve the accuracy of the decoder in determining the quantized LSF parameters of the secondary channel signal based on the predicted residuals and the quantized LSF parameters of the primary channel signal.

[0131] S510, S520, and S530 can be implemented in multiple ways. The following explanation will be provided with reference to Figures 6 to 9.

[0132] As shown in Figure 6, S510 may include S610, and S520 may include S620.

[0133] S610: Perform pull-to-average spread spectrum on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters of the primary channel signal.

[0134] The average stretching process described above can be performed according to the following formula.

number

[0135] Here,

number

number

number

[0136] Typically, different linear prediction ranks can be used for different coding bandwidths. For example, if the coding bandwidth is 16 kHz, a 20th-order linear prediction may be performed, i.e., M=20. If the coding bandwidth is 12.8 kHz, a 16th-order linear prediction may be performed, i.e., M=16. The LSF parameter vector can also be simply referred to as the LSF parameters.

[0137] The diffusion coefficient β can be a predetermined constant. For example, β can be a predetermined real constant greater than 0 and less than 1. For example, β = 0.82 or β = 0.91.

[0138] Alternatively, the spreading factor β can be acquired adaptively. For example, different spreading factors β may be preset based on different coding parameters such as different coding modes, coding bandwidth, or coding rates, and then the corresponding spreading factor β is selected based on one or more current coding parameters. The coding modes described herein may include speech activation detection results, voiceless and voiced distinctions, and so on.

[0139] For example, the corresponding spreading coefficient β below can be set to different coding rates.

number

[0140] Here, "brate" represents the encoding rate.

[0141] Next, the spreading factor corresponding to the coding rate in the current frame can be determined based on the coding rate in the current frame and the aforementioned correspondence between the coding rate and the spreading factor.

[0142] The mean vector of the LSF parameters of the secondary channel signal can be obtained through training based on a large amount of data, can be a pre-set constant vector, or can be obtained adaptively.

[0143] For example, different mean vectors of the LSF parameters of a secondary channel signal can be pre-set based on coding parameters such as coding mode, coding bandwidth, or coding rate. Then, the mean vector corresponding to the LSF parameters of the secondary channel signal is selected based on the coding parameters in the current frame.

[0144] S620: The difference between the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal is used as the predicted residual of the LSF parameter of the secondary channel signal.

[0145] Specifically, the predicted residual of the LSF parameter of the secondary channel signal satisfies the following equation.

number

[0146] Here,

number

number

number

[0147] In other words, the spread spectrum LSF parameter of the primary channel signal is used directly as the predicted LSF parameter of the secondary channel signal (this implementation is referred to as performing a single-stage prediction on the LSF parameter of the secondary channel signal), and the difference between the original LSF parameter of the secondary channel signal and the predicted LSF parameter of the secondary channel signal can be used as the predicted residual of the LSF parameter of the secondary channel signal.

[0148] As shown in Figure 7, S510 may include S710, and S520 may include S720.

[0149] S710: Perform average extended spread spectrum on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters of the primary channel signal.

[0150] Please refer to S610 for details on this stage. Further explanation will not be provided here.

[0151] S720: Based on the spread spectrum LSF parameters of the primary channel signal, a multi-stage prediction is performed on the LSF parameters of the secondary channel signal to obtain the predicted LSF parameters of the secondary channel signal, and the difference between the original LSF parameters of the secondary channel signal and the predicted LSF parameters of the secondary channel signal is used as the predicted residual of the secondary channel signal.

[0152] A particular number of predictions performed on the LSF parameters of a secondary channel signal can be referred to as a particular number of prediction stages performed on the LSF parameters of a secondary channel signal.

[0153] Multistage prediction may involve predicting the spread spectrum LSF parameters of the primary channel signal as the predicted LSF parameters of the secondary channel signal. This prediction may be referred to as intra-prediction.

[0154] Intra-predictions can be performed at any point in a multi-stage prediction. For example, an intra-prediction (i.e., stage 1 prediction) may be performed first, followed by non-intra-predictions (e.g., stage 2 and stage 3 predictions). Alternatively, non-intra-predictions (i.e., stage 1 prediction) may be performed first, followed by an intra-prediction (i.e., stage 2 prediction). Naturally, non-intra-predictions (i.e., stage 3 prediction) may be performed further.

[0155] If a two-stage prediction is performed on the LSF parameters of a secondary channel signal, and the Stage 1 prediction is an intra-prediction, then the Stage 2 prediction may be performed based on the intra-prediction result of the LSF parameters of the secondary channel signal (i.e., based on the spread spectrum LSF parameters of the primary channel signal), or based on the original LSF parameters of the secondary channel signal. For example, the Stage 2 prediction may be performed on the LSF parameters of the secondary channel signal by using an inter-prediction method based on the quantized LSF parameters of the secondary channel signal in the previous frame and the original LSF parameters of the secondary channel signal in the current frame.

[0156] When a two-stage prediction is performed on the LSF parameters of the secondary channel signal, with the first stage prediction being an intra-prediction and the second stage prediction being based on the spread spectrum LSF parameters of the primary channel signal, the prediction residuals for the secondary channel's LSF parameters satisfy the following equation.

number

number

[0157] Here,

number

number

number

number

number

[0158] If a two-stage prediction is performed on the LSF parameters of the secondary channel signal, with the first stage prediction being an intra-prediction and the second stage prediction being based on the original LSF parameter vector of the secondary channel signal, then the predicted residuals of the LSF parameters of the secondary channel signal satisfy the following equation.

number

number

[0159] Here,

number

number

number

number

number

[0160] As shown in Figure 8, S510 may include S810, S820, and S830, and S520 may include S840.

[0161] S810: Converts the quantized LSF parameters of the primary channel signal into linear prediction coefficients.

[0162] For details on converting LSF parameters to linear prediction coefficients, please refer to the prior art. Details will not be explained here. The linear prediction coefficient obtained after converting the quantized LSF parameters of the primary channel signal to linear prediction coefficients is α. i If it is shown as and the transfer function used in the transformation is denoted as A(z), then the following equation is satisfied.

number

[0163] Here, α i is a linear prediction coefficient obtained after converting the quantized LSF parameters of the primary channel signal into linear prediction coefficients, where M is the linear prediction rank.

[0164] S820: Correct the linear prediction coefficients to obtain the corrected linear prediction coefficients for the primary channel signal.

[0165] The transfer function of the modified linear predictor satisfies the following equation:

number

[0166] Here, α i β is a linear prediction coefficient obtained after converting the quantized LSF parameters of the primary channel signal into linear prediction coefficients, where β is the spreading factor and M is the linear prediction order.

[0167] The spread spectrum linear prediction coefficient for the primary channel signal satisfies the following equation.

number

number

[0168] Here, a i This is a linear prediction coefficient obtained after converting the quantized LSF parameters of the primary channel signal into linear prediction coefficients.

number

[0169] For information on how to obtain the diffusion coefficient β in this implementation, please refer to the method for obtaining the diffusion coefficient β in S610. Further details will not be explained here.

[0170] S830: Convert the modified linear prediction coefficients of the primary channel signal into LSF parameters. Here, the LSF parameters obtained through the conversion are the spread spectrum LSF parameters of the primary channel signal.

[0171] For methods of converting linear prediction coefficients to LSF parameters, please refer to prior art. Details are not provided here. The spread spectrum LSF parameters of the primary channel signal are:

number

[0172] S840: The difference between the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal is used as the predicted residual of the LSF parameter of the secondary channel signal.

[0173] For this stage, please refer to S620. Further details will not be explained here.

[0174] As shown in Figure 9, S510 may include S910, S920, and S930, and S520 may include S940.

[0175] S910: Converts the quantized LSF parameters of the primary channel signal into linear prediction coefficients.

[0176] Please refer to S810 for details on this stage. Further explanation will not be provided here.

[0177] S920: Correct the linear prediction coefficients to obtain the corrected linear prediction coefficients for the primary channel signal.

[0178] Please refer to S820 for details on this stage. Further explanation will not be provided here.

[0179] S930: Convert the modified linear prediction coefficients of the primary channel signal into LSF parameters. Here, the LSF parameters obtained through the conversion are the spread spectrum LSF parameters of the primary channel signal.

[0180] Please refer to S830 for details on this stage. Further explanation will not be provided here.

[0181] S940: Based on the spread spectrum LSF parameters of the primary channel signal, a multi-stage prediction is performed on the LSF parameters of the secondary channel signal to obtain the predicted LSF parameters of the secondary channel signal, and the difference between the original LSF parameters of the secondary channel signal and the predicted LSF parameters of the secondary channel signal is used as the predicted residual of the secondary channel signal.

[0182] Please refer to S720 for details on this stage. Further explanation will not be provided here.

[0183] In S530 of this embodiment, when quantization is performed on the predicted residual of the LSF parameter of the secondary channel signal, any prior art LSF parameter vector quantization method, such as partitioned vector quantization, multistage vector quantization, or safenet vector quantization, may be referenced.

[0184] The vector obtained after quantizing the predicted residuals of the LSF parameters of the secondary channel signal is

number

number

[0185] Here,

number

number

number

[0186] Figure 10 is a schematic flowchart of a stereo signal decoding method according to one embodiment of the present invention. If the reuse determination result indicates that the reuse conditions are not met, the decoding component 120 may perform the method shown in Figure 10.

[0187] S1010: Retrieves the quantized LSF parameters of the primary channel signal in the current frame from the bitstream.

[0188] Please refer to the conventional technology for this stage. Details will not be explained here.

[0189] S1020: Perform spread spectrum on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters of the primary channel signal.

[0190] Please refer to S510 for details on this stage. Further explanation will not be provided here.

[0191] S1030: Obtain the predicted residual of the LSF parameter of the secondary channel signal in the current frame of the stereo signal from the bitstream.

[0192] For this stage, please refer to the implementation methods for obtaining arbitrary parameters of a stereo signal from a bitstream in conventional technology. Details will not be explained here.

[0193] S1040: The quantized LSF parameters of the secondary channel signal are determined based on the predicted residuals of the LSF parameters of the secondary channel signal and the spread spectrum LSF parameters of the primary channel signal.

[0194] In the decoding method according to the embodiment of the present invention, the quantized LSF parameter of the secondary channel signal can be determined based on the predicted residual of the LSF parameter of the secondary channel signal. This helps to reduce the number of bits occupied by the LSF parameter of the secondary channel signal in the bitstream.

[0195] In addition, since the quantized LSF parameters of the secondary channel signal are determined based on the LSF parameters obtained after spread spectrum analysis has been performed on the quantized LSF parameters of the primary channel signal, similar features can be used between the linearly predicted spectral envelope of the primary channel signal and the linearly predicted spectral envelope of the secondary channel signal. This helps to improve the accuracy of the quantized LSF parameters of the secondary channel signal.

[0196] In some possible implementations, obtaining the spread spectrum LSF parameter of the primary channel signal by performing spread spectrum on the quantized LSF parameter of the primary channel signal in the current frame of a stereo signal involves performing mean extension on the quantized LSF parameter of the primary channel signal to obtain the spread spectrum LSF parameter, where mean extension may be performed according to the following equation.

number

[0197] Here,

number

number

number

[0198] In a possible implementation, the step of performing spread spectrum on the quantized LSF parameters of the primary channel signal in the current frame of a stereo signal to obtain the spread spectrum LSF parameters of the primary channel signal includes the steps of: converting the quantized LSF parameters of the primary channel signal into linear prediction coefficients; modifying the linear prediction coefficients to obtain modified linear prediction coefficients of the primary channel signal; and converting the modified linear prediction coefficients of the primary channel signal into LSF parameters, wherein the LSF parameters obtained through the conversion are the spread spectrum LSF parameters of the primary channel signal.

[0199] In some possible implementations, the quantized LSF parameter of the secondary channel signal is the sum of the spread spectrum LSF parameter of the primary channel signal and the predicted residual of the LSF parameter of the secondary channel signal.

[0200] In some possible implementations, the step of determining the quantized LSF parameters of the secondary channel signal based on the prediction residual of the LSF parameters of the secondary channel signal and the spectral spread LSF parameters of the primary channel signal may include: performing a two-stage prediction on the LSF parameters of the secondary channel signal based on the spectral spread LSF parameters of the primary channel signal to obtain the predicted LSF parameters; and using the sum of the predicted LSF parameters and the prediction residual of the LSF parameters of the secondary channel signal as the quantized LSF parameters of the secondary channel signal.

[0201] For an implementation of performing a two-stage prediction on the LSF parameters of the secondary channel signal based on the spectral spread LSF parameters of the primary channel signal to obtain the predicted LSF parameters in this implementation, refer to S720. Details will not be described again here.

[0202] FIG. 11 is a schematic block diagram of a stereo signal encoding apparatus 1100 according to an embodiment of the present application. It should be understood that the encoding apparatus 1100 is merely an example.

[0203] In some implementations, the spectral spread module 1110, the determination module 1120, and the quantization module 1130 may all be included in the encoding component 110 of the mobile terminal 130 or the network element 150.

[0204] The spectral spread module 1110 is configured to perform spectral spread on the quantized line spectral frequency LSF parameters of the primary channel signal in the current frame of the stereo signal to obtain the spectral spread LSF parameters of the primary channel signal.

[0205] The decision module 1120 is configured to determine the predicted residual of the LSF parameter of the secondary channel signal in the current frame, based on the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal.

[0206] The quantization module 1130 is configured to perform quantization on the prediction residuals.

[0207] Optionally, the spread spectrum module is configured to perform mean extension on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters, which may be performed according to the following equation.

number

[0208] Here,

number

number

number

[0209] Optionally, the spread spectrum module may be configured to convert the quantized LSF parameters of the primary channel signal into linear prediction coefficients, modify the linear prediction coefficients to obtain modified linear prediction coefficients for the primary channel signal, and convert the modified linear prediction coefficients for the primary channel signal into LSF parameters, the LSF parameters obtained through the conversion being the spread spectrum LSF parameters of the primary channel signal.

[0210] Optionally, the predicted residual of the secondary channel signal is the difference between the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter.

[0211] Optionally, the decision module may be configured to perform a two-stage prediction on the LSF parameters of the secondary channel signal based on the spread spectrum LSF parameters of the primary channel signal to obtain the predicted LSF parameters of the secondary channel signal, and to use the difference between the original LSF parameters of the secondary channel signal and the predicted LSF parameters as the predicted residual of the secondary channel signal.

[0212] Before determining the predicted residual of the secondary channel signal's LSF parameter in the current frame, based on the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal, the decision module is further configured to determine if the secondary channel signal's LSF parameter does not meet the reuse criteria.

[0213] The encoding device 1100 may be configured to perform the encoding method described in Figure 5. For brevity, the details will not be described again here.

[0214] Figure 12 is a schematic block diagram of a stereo signal decoding device 1200 according to one embodiment of the present invention. It should be understood that the decoding device 1200 is merely an example.

[0215] In some implementations, the acquisition module 1220, the spectrum spreading module 1230, and the determination module 1240 may all be included in the decoding component 120 of the mobile terminal 140 or the network element 150.

[0216] The acquisition module 1220 is configured to obtain the quantized LSF parameters of the primary channel signal in the current frame from the bitstream.

[0217] The spectrum spreading module 1230 is configured to perform spectrum spreading on the quantized LSF parameters of the primary channel signal to obtain the spectrum-spread LSF parameters of the primary channel signal.

[0218] The acquisition module 1220 is further configured to obtain the prediction residual of the line spectral frequency LSF parameters of the secondary channel signal in the current frame in the stereo signal from the bitstream.

[0219] The determination module 1240 is configured to determine the quantized LSF parameters of the secondary channel signal based on the prediction residual of the LSF parameters of the secondary channel signal and the spectrum-spread LSF parameters of the primary channel signal.

[0220] Optionally, the spectrum spreading module specifically may be configured to perform an average extension process on the quantized LSF parameters of the primary channel signal to obtain the spectrum-spread LSF parameters, and the average extension process may be performed according to the following formula.

Number

[0221] Here,

Number

number

number

[0222] Optionally, the spread spectrum module may be configured to convert the quantized LSF parameters of the primary channel signal into linear prediction coefficients, modify the linear prediction coefficients to obtain modified linear prediction coefficients for the primary channel signal, and convert the modified linear prediction coefficients for the primary channel signal into LSF parameters, the LSF parameters obtained through the conversion being the spread spectrum LSF parameters of the primary channel signal.

[0223] Optionally, the quantized LSF parameter of the secondary channel signal is the sum of the spread spectrum LSF parameter and the predicted residual.

[0224] Optionally, the decision module may be configured to perform a two-stage prediction on the LSF parameters of the secondary channel signal based on the spread spectrum LSF parameters of the primary channel signal to obtain the predicted LSF parameters, and to use the sum of the predicted LSF parameters and the prediction residuals as the quantized LSF parameters of the secondary channel signal.

[0225] Before acquiring the predicted residual of the line spectral frequency (LSF) parameter of the secondary channel signal in the current frame of the stereo signal from the bitstream, the acquisition module is further configured to determine if the LSF parameter of the secondary channel signal does not meet the reuse conditions.

[0226] The decoding device 1200 may be configured to perform the decoding method described in Figure 10. For brevity, the details will not be described again here.

[0227] Figure 13 is a schematic block diagram of a stereo signal encoding device 1300 according to one embodiment of the present invention. It should be understood that the encoding device 1300 is merely an example.

[0228] Memory 1310 is configured to store the program.

[0229] The processor 1320 is configured to execute a program stored in memory. When the program in memory is executed, the processor is configured to perform spread spectrum on the quantized line spectral frequency (LSF) parameters of the primary channel signal in the current frame of the stereo signal to obtain the spread spectrum LSF parameters of the primary channel signal, determine the predicted residuals of the LSF parameters of the secondary channel signal in the current frame based on the original LSF parameters of the secondary channel signal and the spread spectrum LSF parameters of the primary channel signal, and perform quantization on the predicted residuals.

[0230] Optionally, the processor 1320 may be configured to perform mean extension on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters, and the mean extension may be performed according to the following equation.

number

[0231] Here,

number

number

number

[0232] Optionally, the processor may be configured to specifically convert the quantized LSF parameters of the primary channel signal into linear prediction coefficients, modify the linear prediction coefficients to obtain modified linear prediction coefficients of the primary channel signal, and convert the modified linear prediction coefficients of the primary channel signal into LSF parameters, the LSF parameters obtained through the conversion being the spread spectrum LSF parameters of the primary channel signal.

[0233] Optionally, the predicted residual of the secondary channel signal is the difference between the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter.

[0234] Optionally, the processor may be configured to perform a two-stage prediction on the LSF parameters of the secondary channel signal based on the spread spectrum LSF parameters of the primary channel signal to obtain the predicted LSF parameters of the secondary channel signal, and to use the difference between the original LSF parameters of the secondary channel signal and the predicted LSF parameters as the predicted residual of the secondary channel signal.

[0235] Before determining the predicted residual of the secondary channel signal's LSF parameter in the current frame, based on the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal, the processor is further configured to determine if the secondary channel signal's LSF parameter does not meet the reuse condition.

[0236] The encoding device 1300 may be configured to perform the encoding method described in Figure 5. For brevity, the details will not be described again here.

[0237] Figure 14 is a schematic block diagram of a stereo signal decoding device 1400 according to one embodiment of the present invention. It should be understood that the decoding device 1400 is merely an example.

[0238] Memory 1410 is configured to store the program.

[0239] The processor 1420 is configured to execute a program stored in memory. When the program in memory is executed, the processor is configured to obtain the quantized LSF parameters of the primary channel signal in the current frame from the bitstream, perform spread spectrum on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters of the primary channel signal, obtain the predicted residuals of the line spectral frequency LSF parameters of the secondary channel signal in the current frame of the stereo signal from the bitstream, and determine the quantized LSF parameters of the secondary channel signal based on the predicted residuals of the LSF parameters of the secondary channel signal and the spread spectrum LSF parameters of the primary channel signal.

[0240] Optionally, the processor is: The system may be configured to perform mean extension on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters, and the mean extension may be performed according to the following equation.

number

[0241] Here,

number

number

number

[0242] Optionally, the processor may be configured to specifically convert the quantized LSF parameters of the primary channel signal into linear prediction coefficients, modify the linear prediction coefficients to obtain modified linear prediction coefficients of the primary channel signal, and convert the modified linear prediction coefficients of the primary channel signal into LSF parameters, the LSF parameters obtained through the conversion being the spread spectrum LSF parameters of the primary channel signal.

[0243] Optionally, the quantized LSF parameter of the secondary channel signal is the sum of the spread spectrum LSF parameter of the primary channel signal and the predicted residual.

[0244] Optionally, the processor may be configured to perform a two-stage prediction on the LSF parameters of the secondary channel signal based on the spread spectrum LSF parameters of the primary channel signal to obtain the predicted LSF parameters, and to use the sum of the predicted LSF parameters and the prediction residuals as the quantized LSF parameters of the secondary channel signal.

[0245] Before obtaining the predicted residual of the line spectral frequency (LSF) parameter of the secondary channel signal in the current frame of the stereo signal from the bitstream, the processor is further configured to determine if the LSF parameter of the secondary channel signal does not meet the reuse condition.

[0246] The decoding device 1400 may be configured to perform the decoding method described in Figure 10. For brevity, the details will not be described again here.

[0247] Those skilled in the art will recognize, by combining the various examples described in the embodiments disclosed herein, that multiple units and multiple algorithmic stages can be implemented by electronic hardware or by a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and the design constraints of the technical solution. Those skilled in the art will implement the described functions for specific applications using different methods, but these implementation examples should not be considered beyond the scope of the application.

[0248] For the sake of simplicity and conciseness, and so that those skilled in the art can clearly understand, please refer to the corresponding processes in the embodiments of the methods described above for detailed operating processes of the aforementioned systems, apparatus, and units. Further details will not be described here.

[0249] In some embodiments provided herein, it should be understood that the disclosed systems, apparatus, and methods may be implemented in other ways. For example, the embodiments of the apparatus described are merely examples. For example, the division into units is simply a division of logical functions. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, and some functions may be ignored or not performed. Furthermore, the mutual coupling, direct coupling, or communication connection shown or described may be implemented using several interfaces. Indirect coupling or communication connection between multiple devices or multiple units may be implemented in electronic, mechanical, or other forms.

[0250] Units described as separate parts may or may not be physically separate, and parts shown as units may or may not be physical units, may be located in one place, or may be distributed across multiple network units. Some or all of these units may be selected based on actual requirements to achieve the objectives of the solutions of these embodiments.

[0251] In addition, the functional units in the embodiments of the present invention may be integrated into a single processing unit, each of the units may exist physically independently, or two or more units may be integrated into a single unit.

[0252] It should be understood that the processor in the embodiments of this application may be a central processing unit (CPU). Alternatively, the processor may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or another programmable logic device, discrete gate or transistor logic device, discrete hardware component, etc. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor, etc.

[0253] When a function is implemented in the form of a software function unit and sold or used as a standalone product, the function may be stored on a computer-readable storage medium. Based on such understanding, the technical solution of the present application, or a portion of the prior art, or a part of the technical solution may be implemented in the form of a software product. The computer software product is stored on a storage medium and includes several instructions for instructing a computer device (which may be a personal computer, server, or network device) to perform all or certain steps of the methods described in embodiments of the present application. The storage medium mentioned above includes any medium capable of storing program code, such as a USB flash drive, removable hard disk, read-only memory (ROM), random access memory (RAM), magnetic disk, or compact disk.

[0254] The foregoing description is merely a specific implementation example of the present application and is not intended to limit the scope of protection of the present application. Any modification or substitution that is readily conceivable by a person skilled in the art within the scope of the art disclosed herein will be included in the scope of protection of the present application. Accordingly, the scope of protection of the present application will be subject to the scope of protection of the claims. Other possible claims (Item 1) A method for encoding stereo signals, The steps include: performing spread spectrum on the quantized line spectral frequency (LSF) parameter of the primary channel signal in the current frame of the stereo signal to obtain the spread spectrum (LSF) parameter of the primary channel signal; A step of determining the predicted residual of the LSF parameter of the secondary channel signal in the current frame based on the original LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal, The step of performing quantization on the above prediction residuals. A method for providing this. (Item 2) The above step of performing spread spectrum on the quantized line spectral frequency (LSF) parameter of the primary channel signal in the current frame of the stereo signal to obtain the spread spectrum (LSF) parameter of the primary channel signal is as follows: This step involves performing an average extension process on the quantized LSF parameters of the primary channel signal to obtain the spread spectrum LSF parameters. The above average extension process is performed using the following formula, i.e.

number

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Claims

1. A method for decoding multichannel signals, The steps include receiving a bitstream having the quantized line spectral frequency (LSF) parameter of the primary channel signal in the current frame of a multichannel signal containing at least two channel signals, The steps include parsing the bitstream to obtain the quantized LSF parameters of the primary channel signal, A step of obtaining the spread spectrum LSF parameter of the primary channel signal based on the quantized LSF parameter of the primary channel signal, The steps include obtaining the predicted residual of the LSF parameter in the secondary channel signal of the current frame, A step of obtaining the quantized LSF parameter of the secondary channel signal based on the predicted residual of the LSF parameter of the secondary channel signal and the spread spectrum LSF parameter of the primary channel signal, A step of acquiring the reconstructed multichannel signal of the current frame based on the quantized LSF parameters of the secondary channel signal, A method for decoding multichannel signals, comprising the following features.

2. The step of obtaining the spread spectral LSF parameter of the primary channel signal based on the quantized LSF parameter of the primary channel signal is: A step in which the diffusion rate is obtained, wherein the diffusion rate is greater than 0 and less than 1, The steps include obtaining the mean vector of the original LSF parameters of the secondary channel signal, The steps include obtaining the vector of the quantized LSF parameters of the primary channel signal, A step of obtaining the spread spectrum LSF parameter of the primary channel signal based on the diffusion rate, the mean vector, and the vector of the quantized LSF parameter of the primary channel signal, A method for decoding a multichannel signal according to claim 1, comprising:

3. The step of obtaining the spread spectrum LSF parameters of the primary channel signal based on the spreading coefficient, the mean vector, and the vector of the quantized LSF parameters of the primary channel signal is: [Math 1] Accordingly, the process includes the step of obtaining the spread spectrum LSF parameters of the primary channel signal, LSF SB This represents the vector of the spread spectrum LSF parameters of the primary channel signal, LSF Ｐ (i) represents the vector of the quantized LSF parameters of the primary channel signal, i represents the vector index, β represents the diffusion rate, where 0 < β < 1. [Math 4] The method for decoding a multichannel signal according to claim 2, wherein represents the mean vector, 1 ≤ i ≤ M, i is an integer, and M represents a linear prediction parameter.

4. The step of obtaining the spread spectrum LSF parameter of the primary channel signal based on the quantized LSF parameter of the primary channel signal is: A step of converting the quantized LSF parameters of the primary channel signal into linear prediction coefficients, A step of obtaining a modified linear prediction coefficient for the primary channel signal based on the linear prediction coefficient, The steps include converting the modified linear prediction coefficient of the primary channel signal into the spread spectrum LSF parameter of the primary channel signal, A method for decoding a multichannel signal according to any one of claims 1 to 3, comprising:

5. The method for decoding a multichannel signal according to any one of claims 1 to 4, wherein the quantized LSF parameter of the secondary channel signal is the sum of the spread spectrum LSF parameter of the primary channel signal and the predicted residual.

6. The step of obtaining the quantized LSF parameters of the secondary channel signal is: A step of obtaining predicted LSF parameters by performing a two-stage prediction on the LSF parameters of the secondary channel signal based on the spread spectrum LSF parameters of the primary channel signal. A step of obtaining the sum of the predicted LSF parameters and the predicted residual, wherein the sum represents the quantized LSF parameters of the secondary channel signal. A method for decoding a multichannel signal according to any one of claims 1 to 5, comprising:

7. A computer-readable storage medium storing a program that causes a computer to execute a multi-channel signal decoding method according to any one of claims 1 to 6.

8. A computer program that causes a computer to perform a multi-channel signal decoding method according to any one of claims 1 to 6.

9. Memory and A stereo signal encoding device comprising: at least one processor coupled to the memory and configured to perform the multi-channel signal decoding method according to any one of claims 1 to 6.

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