CN111833891A - LC3 encoding and decoding system, LC3 encoder and optimization method thereof - Google Patents
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Abstract
The application discloses an LC3 encoding and decoding system, an LC3 encoder and an optimization method thereof, and belongs to the technical field of audio encoding. The LC3 codec system of the present application includes: the LC3 encoder and the LC3 decoder are included, the LC3 encoder comprises a first long-term post-filter, the first long-term post-filter comprises a first long-term post-filter encoding module, the first long-term post-filter encoding module comprises a first long-term post-filter resampling module, wherein when the LC3 encoder receives a message that a current frame is encoded into a fixed-code-rate encoding scene, whether the current frame code rate at an entrance of the first long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the first long-term post-filter encoding module is closed. According to the fixed code rate coding scene, the complex LTPF (low temperature peak power factor) operation amount of about 5-15 mcps on the LC3 encoder side can be reduced, and the requirement of a processor can be reduced.
Description
Technical Field
The present application relates to the field of audio coding technologies, and in particular, to an LC3 codec system, an LC3 encoder, and an optimization method thereof.
Background
With the continuous development of the mobile communication field, the application of the bluetooth technology is also wider and wider, especially in the application aspect of bluetooth audio.
The Bluetooth international association Bluetooth Sig has now introduced a low complexity communication codec LC3 in conjunction with numerous vendors. Due to the LC3 codec technology, it has the advantages of lower delay, higher sound quality and coding gain and no special fee in the bluetooth field, and is receiving attention from a wide range of manufacturers. Since the LC3 originally proposes to satisfy the audio application in the bluetooth low energy field, the requirement for power consumption is very strict, in the bluetooth low energy field, the power consumption of the mobile device is expected to be low, the code rate of the audio is proportional to the occupied air bandwidth, and the code rate of the audio directly affects the power consumption of the radio frequency. The lower code rate can not only reduce the radio frequency power consumption and air interference of the transmitting and receiving end, but also reduce the operation amount of the coder and the decoder (mainly reducing the operation amount of arithmetic coding and decoding).
In the prior art, a Long Term Post Filter (LTPF) is used to process a time domain signal of a current frame using a historical time domain signal in the time domain signal. LTPF is a pitch (pitch) based post-filter at the decoding end that can perceive quantization noise in the spectral valleys. In a scene, when the current frame code rate is larger than or equal to a sampling rate related constant threshold, because the gain of the long-term post filter is 0, the long-term post filter in an actual LC3 decoder is not started, only the pitch integer part and the pitch fraction part are reserved in the historical pitch integer part and the historical pitch fraction part, and the gain of the long-term post filter is reserved in the historical long-term post filter to prepare for long period record for the next frame processing. Since the bitrate in this scenario does not change, these values recorded for long periods will always remain 0, which is a waste for the LC3 codec.
Disclosure of Invention
In view of the above technical problems in the prior art, the present application provides an LC3 codec system, an LC3 encoder, and an optimization method thereof.
The technical scheme adopted by the application is as follows: the LC3 coding and decoding system comprises an LC3 encoder and an LC3 decoder, wherein the LC3 encoder comprises a first long-term post-filter, the first long-term post-filter comprises a first long-term post-filter coding module, the first long-term post-filter coding module comprises a first long-term post-filter resampling module, when the LC3 encoder receives a message that a current frame is coded into a fixed-code-rate coding scene, whether the current frame code rate at the inlet of the first long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the first long-term post-filter coding module is closed.
Another technical scheme adopted by the application is as follows: the utility model provides a LC3 encoder, it includes long term post filter, long term post filter includes long term post filter coding module, long term post filter coding module includes long term post filter resampling module, wherein, when LC3 encoder received the message that current frame code is fixed code rate coding scene, judge whether the current frame code rate of long term post filter resampling module's entrance satisfies the preset condition, if satisfy the preset condition, close long term post filter coding module.
Another technical scheme adopted by the application is as follows: a method of optimizing an LC3 codec system, the method comprising: the LC3 coding and decoding system comprises an LC3 coder and an LC3 decoder, the LC3 coder comprises a first long-term post-filter, the first long-term post-filter comprises a first long-term post-filter coding module, the first long-term post-filter coding module comprises a first long-term post-filter resampling module, wherein when the LC3 coder receives a message that a current frame is coded into a fixed-code-rate coding scene, whether the current frame code rate at the entrance of the first long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the first long-term post-filter coding module is closed.
Another technical scheme adopted by the application is as follows: a method of optimizing an LC3 encoder, the method comprising: the LC3 encoder comprises a long-term post-filter, the long-term post-filter comprises a long-term post-filter encoding module, the long-term post-filter encoding module comprises a long-term post-filter resampling module, wherein when the LC3 encoder receives a message that the current frame codes in a fixed-rate encoding scene, whether the current frame code rate at the entrance of the long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the long-term post-filter encoding module is closed.
Another technical scheme adopted by the application is as follows: a computer readable storage medium storing computer instructions operable to perform a method of optimizing an LC3 codec system or a method of optimizing an LC3 encoder.
The beneficial effect of this application lies in: an LC3 encoder receives a message that a current frame is encoded into a fixed code rate encoding scene; when detecting the message of the fixed-rate coding scene, the LC3 encoder closes all the coding modules in the long-term postfilter if the current frame rate at the entrance of the resampling module in the long-term postfilter coding module meets a preset condition. According to the fixed code rate coding scene, the complex LTPF operand of about 5-15 mcps can be reduced on one side of the LC3 coder, the tone quality can be enhanced, and the requirement of a processor is reduced.
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FIG. 1 is a schematic diagram illustrating the LTPF encoding operation of an LC3 encoder in the prior art;
FIG. 2 is a diagram illustrating the LTPF encoded operational data flow of a prior art LC3 encoder;
FIG. 3 is a diagram of an embodiment of an LC3 codec system of the present application;
fig. 4 is a schematic diagram of an embodiment of an LC3 encoder of the present application.
Detailed Description
In order to make the aforementioned features and advantages of the present application more comprehensible, the present application is described in further detail below with reference to the accompanying drawings and the detailed description. This detailed description is merely intended to facilitate an understanding of the present application and the scope of the present application is not limited to the specific description stored in the detailed description.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Fig. 1 shows the LTPF encoding operation of the LC3 encoder in the prior art. Fig. 2 shows the LTPF encoding operation data stream of the LC3 encoder. The nomenclature of the application and the prior art will now be described with reference to fig. 1 and 2.
The input signal of the current frame can be composed of NFAn audio sample xs[n]When an input signal is inputted to the LTPF,
first, resampling to a frequency of 12.8kHz produces 128 audio samples x12.8[n]；
Second, high pass filtering is performed through a 2 nd order IIR (infinite impulse response) filter of HP50-50Hz, resulting in 128 audio samples
12.8(n)；
Again, downsampling to a frequency of 6.4kHz produces 64 audio samples x6.4[n]；
Thirdly, Pitch detection is performed for 64 audio samples x6.4[n]Performing finite space autocorrelation to obtain an unweighted autocorrelation coefficient set R64, weighting the unweighted autocorrelation coefficient set R64 to obtain a weighted autocorrelation coefficient set RW64, and obtaining an unweighted autocorrelation pitch lag T1 and an added autocorrelation pitch lag T64 according to the unweighted autocorrelation coefficient set R64 and the weighted autocorrelation coefficient set RW64A ratio of the weighted autocorrelation Pitch lag T2 and a normalized autocorrelation coefficient (norm corr), wherein if the normalized autocorrelation coefficient (norm corr) is greater than 0.6, a Pitch lag estimation (Pitch lag estimation) is turned on;
finally, an LTPF open flag (LTPF _ active) and a pitch sequence number (pitch _ index) are obtained.
Therefore, as can be seen from fig. 2, the LTPF calculation amount on the LC3 encoder side is high, and actually tested by the Cadence hifi3 platform, the LTPF occupies a complex calculation amount of about 5 to 15mcps, and its main overhead is: resampling x _128, high-pass filtering x _ hat _128, downsampling x _64, unweighted autocorrelation coefficient set R64, weighted autocorrelation coefficient set RW64, low-precision normalized correlation coefficients (norm corr), finite impulse response low-pass filtering Xi coefficient set, eight parts of high-precision normalized correlation coefficients nc.
Meanwhile, in the application scenario of the LC3 encoder, the usage scenario is mostly specified as a fixed-bitrate (fixed-bitrate).
The LTPF decoding operation process of the LC3 decoder is to analyze from the LC3 code stream to respectively obtain the current pitch mark (pitch _ present), which occupies 1bit (bit); a pitch sequence number (pitch _ index) for separating a pitch integer part (pitch _ int) and a pitch fraction part (pitch _ fr) which occupy 9 bits; LTPF _ active, which occupies 1 bit.
Therefore, the number of bits occupied by LTPF in the LC3 code stream is 1bit (including only the current tone flag) or 11bits (including the current tone flag, the tone sequence number, and the LTPF on flag).
Fig. 3 shows an embodiment of the LC3 codec system of the present application. In this specific embodiment, the LC3 codec system of the present application mainly includes: LC3 encoder and LC3 decoder, LC3 encoder includes first long term post-positioned filter, and first long term post-positioned filter includes first long term post-positioned filter coding module, and first long term post-positioned filter coding module includes first long term post-positioned filter resampling module. When the LC3 encoder receives a message that the current frame is encoded into a fixed-code-rate encoding scene, whether the current frame code rate at the entrance of the first long-term post-filter resampling module meets a preset condition or not is judged, and if the current frame code rate meets the preset condition, the first long-term post-filter encoding module is closed.
Specifically, firstly, the LC3 encoder side application protocol layer controls inform the LC3 encoder that the current frame is encoded into a fixed rate coded scene (fixed _ bitrate _ flag = 1).
Secondly, the LC3 encoder detects that the current frame is encoded as a fixed _ bitrate _ flag =1 message, at an entrance of the first LTPF resampling module, determines whether the current frame code rate meets a preset condition, and if the current frame code rate meets the preset condition, closes the first LTPF encoding module.
In this embodiment, since in the application protocol of the LC3 encoder, most of the usage scenarios are specified to be a fixed code rate. Fixing the current frame encoding to fixed rate encoding can reduce the amount of operations of the LC3 encoder.
The preset condition is that the current frame code rate (t _ nbits) is more than or equal to 560+ the current frame sampling rate index (fs _ idx) 80. The 560+ fs _ idx 80 condition is the lowest code rate for turning on LTPF specified by the LC3 specification, and if the condition is less than the minimum code rate, LTPF _ active is turned on, and if the condition is greater than or equal to the minimum code rate, LTPF _ active is turned off. Wherein LTPF _ active is a flag specified in the LC3 specification, and is used to describe whether the LTPF of the current frame is on.
In an embodiment of the present application, in the LC3 codec system of the present application, the LC3 encoder is further configured to set the current pitch flag to 0 (pitch _ present = 0) and add the current pitch flag to the side information (side _ information) encoding.
Specifically, when the LC3 encoder is configured to fixed _ bitrate _ flag =1, at the entry of the first LTPF resampling module, if t _ nbits ≧ 560+ fs _ idx 80, the first LTPF encoding module is turned off, that is, all processes from the first LTPF resampling are turned off, no LTPF operation is performed, and pitch _ index and LTPF _ active are ignored. And simultaneously setting the current pitch flag pitch _ present =0 to the side information (side _ information) for encoding, and directly outputting the audio data of the frame.
In this embodiment, in the variable rate scene fixed _ bitrate _ flat =0, the original LTPF logic is still kept unchanged, and the compatibility with the standard decoder in the non-fixed rate (variable rate) scene is kept.
In a specific embodiment of the present application, the first LTPF encoding module is further configured to allocate a free space corresponding to the first LTPF encoding module to a spectrum quantization module of the LC3 encoder. The release space of the first LTPF coding module comprises a release space of a first pitch sequence number (pitch _ index) and a first long-term post-filter opening flag (LTPF _ active).
Specifically, since the first LTPF encoding module is turned off, and at this time, the first pitch _ index and the first LTPF _ active are both 0, the first LTPF encoding module will save 10bits occupied by the first pitch _ index and the first LTPF _ active encoding, that is, the first LTPF encoding module encodes and reduces the vacated space by 10bits in the code stream. At this time, the 10bits are divided into the spectral coefficient coding space bit budget of the current frame again, that is, the 10bits are allocated to the subsequent spectrum quantization module, so that the spectrum quantization module has more 10bits extra spectrum coding space per frame, that is, the 10bits extra coding space can be allocated to the arithmetic coding and/or residual coding of the spectrum signal, thus, compared with the original scheme of the LC3 specification, better sound quality can be obtained under the fixed higher code rate coding scene.
In a specific embodiment of the present application, the LC3 decoder includes a second long term post filter, and the second long term post filter is configured to fill in a corresponding second pitch sequence number (pitch _ index) and a second long term post filter on flag (ltpf _ active) to 0.
Specifically, on the side of any decoder compatible with the LC3 specification, since pitch _ present =0, in this scenario, the current frame code rate is not changed, and LTPF of the LC3 decoder is not started. When the current frame decodes the side _ information, LTPF automatically fills in pitch _ index =0 and LTPF _ active = 0. Therefore, the LC3 decoder does not need to analyze and calculate the gain (gain _ LTPF) of the long-term post filter according to the current frame code rate every time, so that the LTPF decoding module can be kept closed all the time, and the operation amount of the LC3 decoder is saved.
In the specific implementation of the present application, a fixed code rate coding scenario is adopted, so that the complex LTPF operand of about 5 to 15mcps can be reduced on the LC3 encoder side, the sound quality can be enhanced, and the processor requirement can be reduced.
In the specific implementation of the present application, the spectral quantization module of the LC3 encoder of the present application will obtain 10bits of extra spectral coding space in the partial frame, thereby enhancing the sound quality.
In the specific implementation manner of the present application, when the LC3 encoder configures a fixed rate coding scenario, the current pitch flag is always set to 0 (pitch _ present = 0), and the corresponding LC3 decoder side can keep the LTPF decoding filter module always turned off, thereby saving the computation workload of the LC3 decoder.
Fig. 4 shows an embodiment of the LC3 encoder of the present application. In this embodiment, the LC3 encoder of the present application includes: the long-term post-filter comprises a long-term post-filter coding module, and the long-term post-filter coding module comprises a long-term post-filter resampling module. When the LC3 encoder receives a message that the current frame is encoded into a fixed code rate encoding scene, whether the current frame code rate at the entrance of the long-term post-filter resampling module meets a preset condition is judged, and if the current frame code rate meets the preset condition, the long-term post-filter encoding module is closed.
Specifically, the LC3 encoder end application protocol layer control informs the LC3 encoder that the current frame is encoded into a fixed rate coded scene (fixed _ bitrate _ flag = 1). The LC3 encoder detects a message LC3 encoder that the current frame is encoded as fixed _ bitrate _ flag = 1.
The preset condition is that the current frame code rate (t _ nbits) is more than or equal to 560+ the current frame sampling rate index (fs _ idx) 80.
In an embodiment of the present application, in the LC3 encoder of the present application, the LC3 encoder is further configured to set the current pitch flag to 0 (pitch _ present = 0) and add the current pitch flag to the side information (side _ information) encoding.
In a specific embodiment of the present application, the freed space of the long-term post-filter encoding module is allocated to the spectral quantization module of the LC3 encoder when the long-term post-filter encoding module is turned off. The release space of the long-term postfilter coding module comprises a corresponding release space of a pitch sequence number (pitch _ index) and a long-term postfilter opening flag (ltpf _ active).
In another embodiment of the present application, the present application provides a method for optimizing an LC3 codec system, the method comprising: the LC3 coding and decoding system comprises an LC3 coder and an LC3 decoder, the LC3 coder comprises a first long-term post-filter, the first long-term post-filter comprises a first long-term post-filter coding module, the first long-term post-filter coding module comprises a first long-term post-filter resampling module, wherein when the LC3 coder receives a message that a current frame is coded into a fixed-code-rate coding scene, whether the current frame code rate at the entrance of the first long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the first long-term post-filter coding module is closed.
Specifically, the LC3 encoder end application protocol layer control informs the LC3 encoder that the current frame is encoded into a fixed rate coded scene (fixed _ bitrate _ flag = 1). The LC3 encoder detects that the current frame is encoded as a fixed _ bitrate _ flag =1 message.
In this embodiment, since in the application protocol of the LC3 encoder, most of the usage scenarios are specified to be a fixed code rate. The current frame coding is fixed to the fixed code rate coding, on one hand, the sound quality of the current frame is not damaged, and on the other hand, the operation amount of an LC3 coder can be reduced.
The preset condition is that the current frame code rate (t _ nbits) is more than or equal to 560+ the current frame sampling rate index (fs _ idx) 80.
In an embodiment of the present application, the method for optimizing the LC3 codec system further includes setting the current pitch flag to 0 (pitch _ present = 0) and adding the current pitch flag to the side information (side _ information) code.
In a specific embodiment of the present application, the method for optimizing the LC3 codec system further includes allocating the released space corresponding to the first LTPF encoding module to the spectrum quantization module of the LC3 encoder. The release space of the first LTPF coding module comprises a release space of a first pitch sequence number (pitch _ index) and a first long-term post-filter opening flag (LTPF _ active).
In an embodiment of the present application, the method for optimizing the LC3 codec system further includes that the LC3 decoder includes a second long term post filter, and the second long term post filter is configured to fill in 0 a corresponding second pitch sequence number (pitch _ index) and a corresponding second long term post filter start flag (ltpf _ active).
The implementation principle and technical effect of the method for optimizing the LC3 codec system provided by the present application are similar to those of the LC3 codec system, and are not described herein again.
Another technical scheme adopted by the application is as follows: a method of optimizing an LC3 encoder, the method comprising: the LC3 encoder comprises a long-term post-filter, the long-term post-filter comprises a long-term post-filter encoding module, the long-term post-filter encoding module comprises a long-term post-filter resampling module, wherein when the LC3 encoder receives a message that the current frame codes in a fixed-rate encoding scene, whether the current frame code rate at the entrance of the long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the long-term post-filter encoding module is closed.
Specifically, the LC3 encoder end application protocol layer control informs the LC3 encoder that the current frame is encoded into a fixed rate coded scene (fixed _ bitrate _ flag = 1). The LC3 encoder detects that the current frame is encoded as a fixed _ bitrate _ flag =1 message.
The preset condition is that the current frame code rate (t _ nbits) is more than or equal to 560+ the current frame sampling rate index (fs _ idx) 80.
In a specific embodiment of the present application, the method for optimizing the LC3 encoder further includes setting the current pitch flag to 0 (pitch _ present = 0) and adding the current pitch flag to the side information (side _ information) encoding.
In a specific embodiment of the present application, the method for optimizing the LC3 encoder further includes allocating the released space corresponding to the LTPF coding block to the spectrum quantization block of the LC3 encoder. The release space of the LTPF coding module includes a release space of a pitch sequence number (pitch _ index) and a long-term postfilter start flag (LTPF _ active).
The implementation principle and technical effect of the method for optimizing the LC3 encoder provided by the present application are similar to those of the LC3 encoder described above, and are not described herein again.
In another embodiment of the present application, a computer-readable storage medium stores computer instructions operable to perform the method of optimizing an LC3 codec system or the method of optimizing an LC3 encoder described in any one of the embodiments.
In another embodiment of the present application, a program product includes a computer program stored on a readable storage medium, from which the computer program is readable by at least one processor, the computer program being executable by the at least one processor to perform the method for optimizing an LC3 post filter or the method for optimizing an LC3 encoder as described in any of the embodiments.
Wherein the storage medium may be RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium.
The Processor may be a Central Processing Unit (CPU), other general-purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), other Programmable logic devices, discrete Gate or transistor logic, discrete hardware components, or any combination thereof. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment. .
The above summary is only an example of the present application and is not intended to limit the scope of the present application, and all equivalent structural changes made by using the contents of the specification and drawings, or any other related technical fields, are also included in the scope of the present application.
Claims (10)
1. An LC3 codec system, characterized in that, the LC3 codec system includes an LC3 encoder and an LC3 decoder, the LC3 encoder includes a first long-term post-filter, the first long-term post-filter includes a first long-term post-filter encoding module, the first long-term post-filter encoding module includes a first long-term post-filter resampling module, wherein,
when the LC3 encoder receives a message that a current frame is encoded into a fixed-code-rate encoding scene, whether the current frame code rate at the inlet of the first long-term post-filter resampling module meets a preset condition or not is judged, and if the preset condition is met, the first long-term post-filter encoding module is closed.
2. The LC3 codec system of claim 1, wherein the LC3 encoder is further configured to set a current Pitch flag (Pitch _ present) to 0 and add to side information (side _ information) encoding.
3. The LC3 codec system of claim 1 or 2, wherein the first long term post filter coding module is further configured to allocate the free space of the first long term post filter coding module to the spectral quantization module of the LC3 encoder.
4. The LC3 codec system of claim 3, wherein the freed space includes a freed space of a first Pitch sequence number (first Pitch _ index) and a first long term post-filter on flag (first Ltpf _ active) corresponding to the first long term post-filter coding module.
5. The LC3 codec system of claim 1 or 2, wherein the LC3 decoder comprises a second long term post filter for filling in 0 a corresponding second Pitch sequence number (second Pitch _ index) and a second long term post filter on flag (second Ltpf _ active).
6. An LC3 encoder, comprising a long term post filter, wherein the long term post filter comprises a long term post filter encoding module, the long term post filter encoding module comprises a long term post filter resampling module, wherein,
when the LC3 encoder receives a message that a current frame is encoded into a fixed code rate encoding scene, whether the current frame code rate at the entrance of the long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the long-term post-filter encoding module is closed.
7. A method for optimizing an LC3 codec system is characterized in that the LC3 codec system comprises an LC3 encoder and an LC3 decoder, the LC3 encoder comprises a first long-term post-filter, the first long-term post-filter comprises a first long-term post-filter encoding module, the first long-term post-filter encoding module comprises a first long-term post-filter resampling module, wherein,
when the LC3 encoder receives a message that a current frame is encoded into a fixed-code-rate encoding scene, whether the current frame code rate at the inlet of the first long-term post-filter resampling module meets a preset condition or not is judged, and if the preset condition is met, the first long-term post-filter encoding module is closed.
8. The method for optimizing the LC3 codec system of claim 7, wherein the LC3 decoder comprises a second long term post filter for filling in 0 the corresponding Pitch sequence number (Pitch _ index) and long term post filter on flag (Ltpf _ active).
9. A method for optimizing an LC3 encoder, wherein the LC3 encoder includes a long term post filter, the long term post filter includes a long term post filter encoding module, the long term post filter encoding module includes a long term post filter resampling module, wherein,
when the LC3 encoder receives a message that a current frame is encoded into a fixed code rate encoding scene, whether the current frame code rate at the entrance of the long-term post-filter resampling module meets a preset condition is judged, and if the preset condition is met, the long-term post-filter encoding module is closed.
10. A computer readable storage medium storing computer instructions, wherein the computer instructions are operable to perform the method of claim 7 or claim 8 or claim 9.
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