Patent Publication Number: US-9837089-B2

Title: High-band signal generation

Description:
I. CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/181,702, filed Jun. 18, 2015 and entitled “HIGH-BAND SIGNAL GENERATION”, and U.S. Provisional Patent Application No. 62/241,065, filed Oct. 13, 2015 and entitled “HIGH-BAND SIGNAL GENERATION”; the contents of each of the aforementioned applications are expressly incorporated herein by reference in their entirety. 
    
    
     II. FIELD 
     The present disclosure is generally related to high-band signal generation. 
     III. DESCRIPTION OF RELATED ART 
     Advances in technology have resulted in smaller and more powerful computing devices. For example, there currently exist a variety of portable personal computing devices, including wireless telephones such as mobile and smart phones, tablets and laptop computers that are small, lightweight, and easily carried by users. These devices can communicate voice and data packets over wireless networks. Further, many such devices incorporate additional functionality such as a digital still camera, a digital video camera, a digital recorder, and an audio file player. Also, such devices can process executable instructions, including software applications, such as a web browser application, that can be used to access the Internet. As such, these devices can include significant computing capabilities. 
     Transmission of audio, such as voice, by digital techniques is widespread. If speech is transmitted by sampling and digitizing, a data rate on the order of sixty-four kilobits per second (kbps) may be used to achieve a speech quality of an analog telephone. Compression techniques may be used to reduce the amount of information that is sent over a channel while maintaining a perceived quality of reconstructed speech. Through the use of speech analysis, followed by coding, transmission, and re-synthesis at a receiver, a significant reduction in the data rate may be achieved. 
     Speech coders may be implemented as time-domain coders, which attempt to capture the time-domain speech waveform by employing high time-resolution processing to encode small segments of speech (e.g., 5 millisecond (ms) sub-frames) at a time. For each sub-frame, a high-precision representative from a codebook space is found by means of a search algorithm. 
     One time-domain speech coder is the Code Excited Linear Predictive (CELP) coder. In a CELP coder, the short-term correlations, or redundancies, in the speech signal are removed by a linear prediction (LP) analysis, which finds the coefficients of a short-term formant filter. Applying the short-term prediction filter to the incoming speech frame generates an LP residue signal, which is further modeled and quantized with long-term prediction filter parameters and a subsequent stochastic codebook. Thus, CELP coding divides the task of encoding the time-domain speech waveform into the separate tasks of encoding the LP short-term filter coefficients and encoding the LP residue. Time-domain coding can be performed at a fixed rate (i.e., using the same number of bits, N o , for each frame) or at a variable rate (in which different bit rates are used for different types of frame contents). Variable-rate coders attempt to use the amount of bits needed to encode the parameters to a level adequate to obtain a target quality. 
     Wideband coding techniques involve encoding and transmitting a lower frequency portion of a signal (e.g., 50 Hertz (Hz) to 7 kiloHertz (kHz), also called the “low-band”). In order to improve coding efficiency, the higher frequency portion of the signal (e.g., 7 kHz to 16 kHz, also called the “high-band”) may not be fully encoded and transmitted. Properties of the low-band signal may be used to generate the high-band signal. For example, a high-band excitation signal may be generated based on a low-band residual using a non-linear model. 
     IV. SUMMARY 
     In a particular aspect, a device for signal processing includes a memory and a processor. The memory is configured to store a parameter associated with a bandwidth-extended audio stream. The processor is configured to select a plurality of non-linear processing functions based at least in part on a value of the parameter. The processor is also configured to generate a high-band excitation signal based on the plurality of non-linear processing functions. 
     In another particular aspect, a signal processing method includes selecting, at a device, a plurality of non-linear processing functions based at least in part on a value of a parameter. The parameter is associated with a bandwidth-extended audio stream. The method also includes generating, at the device, a high-band excitation signal based on the plurality of non-linear processing functions. 
     In another particular aspect, a computer-readable storage device stores instructions that, when executed by a processor, cause the processor to perform operations including selecting a plurality of non-linear processing functions based at least in part on a value of a parameter. The parameter is associated with a bandwidth-extended audio stream. The operations also include generating a high-band excitation signal based on the plurality of non-linear processing functions. 
     In another particular aspect, a device for signal processing includes a receiver and a high-band excitation signal generator. The receiver is configured to receive a parameter associated with a bandwidth-extended audio stream. The high-band excitation signal generator is configured to determine a value of the parameter. The high-band excitation signal generator is also configured to select, based on the value of the parameter, one of target gain information associated with the bandwidth-extended audio stream or filter information associated with the bandwidth-extended audio stream. The high-band excitation signal generator is further configured to generate a high-band excitation signal based on the one of the target gain information or the filter information. 
     In another particular aspect, a signal processing method includes receiving, at a device, a parameter associated with a bandwidth-extended audio stream. The method also includes determining, at the device, a value of the parameter. The method further includes selecting, based on the value of the parameter, one of target gain information associated with the bandwidth-extended audio stream or filter information associated with the bandwidth-extended audio stream. The method also includes generating, at the device, a high-band excitation signal based on the one of the target gain information or the filter information. 
     In another particular aspect, a computer-readable storage device stores instructions that, when executed by a processor, cause the processor to perform operations including receiving a parameter associated with a bandwidth-extended audio stream. The operations also include determining a value of the parameter. The operations further include selecting, based on the value of the parameter, one of target gain information associated with the bandwidth-extended audio stream or filter information associated with the bandwidth-extended audio stream. The operations also include generating a high-band excitation signal based on the one of the target gain information or the filter information. 
     In another particular aspect, a device includes an encoder and a transmitter. The encoder is configured to receive an audio signal. The encoder is also configured to generate a signal modeling parameter based on a harmonicity indicator, a peakiness indicator, or both. The signal modeling parameter is associated with a high-band portion of the audio signal. The transmitter is configured to transmit the signal modeling parameter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a device includes an encoder and a transmitter. The encoder is configured to receive an audio signal. The encoder is also configured to generate a high-band excitation signal based on a high-band portion of the audio signal. The encoder is further configured to generate a modeled high-band excitation signal based on a low-band portion of the audio signal. The encoder is also configured to select a filter based on a comparison of the modeled high-band excitation signal and the high-band excitation signal. The transmitter is configured to transmit filter information corresponding to the filter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a device includes an encoder and a transmitter. The encoder is configured to receive an audio signal. The encoder is also configured to generate a high-band excitation signal based on a high-band portion of the audio signal. The encoder is further configured to generate a modeled high-band excitation signal based on a low-band portion of the audio signal. The encoder is also configured to generate filter coefficients based on a comparison of the modeled high-band excitation signal and the high-band excitation signal. The encoder is further configured to generate filter information by quantizing the filter coefficients. The transmitter is configured to transmit the filter information in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a method includes receiving an audio signal at a first device. The method also includes generating, at the first device, a signal modeling parameter based on a harmonicity indicator, a peakiness indicator, or both. The signal modeling parameter is associated with a high-band portion of the audio signal. The method further includes sending, from the first device to a second device, the signal modeling parameter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a method includes receiving an audio signal at a first device. The method also includes generating, at the first device, a high-band excitation signal based on a high-band portion of the audio signal. The method further includes generating, at the first device, a modeled high-band excitation signal based on a low-band portion of the audio signal. The method also includes selecting, at the first device, a filter based on a comparison of the modeled high-band excitation signal and the high-band excitation signal. The method further includes sending, from the first device to a second device, filter information corresponding to the filter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a method includes receiving an audio signal at a first device. The method also includes generating, at the first device, a high-band excitation signal based on a high-band portion of the audio signal. The method further includes generating, at the first device, a modeled high-band excitation signal based on a low-band portion of the audio signal. The method also includes generating, at the first device, filter coefficients based on a comparison of the modeled high-band excitation signal and the high-band excitation signal. The method further includes generating, at the first device, filter information by quantizing the filter coefficients. The method also includes sending, from the first device to a second device, the filter information in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a computer-readable storage device stores instructions that, when executed by a processor, cause the processor to perform operations including generating a signal modeling parameter based on a harmonicity indicator, a peakiness indicator, or both. The signal modeling parameter is associated with a high-band portion of the audio signal. The operations also include causing the signal modeling parameter to be sent in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a computer-readable storage device stores instructions that, when executed by a processor, cause the processor to perform operations including generating a high-band excitation signal based on a high-band portion of an audio signal. The operations further include generating a modeled high-band excitation signal based on a low-band portion of the audio signal. The operations also include selecting a filter based on a comparison of the modeled high-band excitation signal and the high-band excitation signal. The operations further include causing filter information corresponding to the filter to be sent in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a computer-readable storage device stores instructions that, when executed by a processor, cause the processor to perform operations including generating a high-band excitation signal based on a high-band portion of an audio signal. The operations further include generating a modeled high-band excitation signal based on a low-band portion of the audio signal. The operations also include generating filter coefficients based on a comparison of the modeled high-band excitation signal and the high-band excitation signal. The operations further include generating filter information by quantizing the filter coefficients. The operations also include causing the filter information to be sent in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. 
     In another particular aspect, a device includes a resampler and a harmonic extension module. The resampler is configured to generate a resampled signal based on a low-band excitation signal. The harmonic extension module is configured to generate at least a first excitation signal corresponding to a first high-band frequency sub-range and a second excitation signal corresponding to a second high-band frequency sub-range based on the resampled signal. The first excitation signal is generated based on application of a first function to the resampled signal. The second excitation signal is generated based on application of a second function to the resampled signal. The harmonic extension module is further configured to generate a high-band excitation signal based on the first excitation signal and the second excitation signal. 
     In another particular aspect, a device includes a receiver and a harmonic extension module. The receiver is configured to receive a parameter associated with a bandwidth-extended audio stream. The harmonic extension module is configured to select one or more non-linear processing functions based at least in part on a value of the parameter. The harmonic extension module is also configured to generate a high-band excitation signal based on the one or more non-linear processing functions. 
     In another particular aspect, a device includes a receiver and a high-band excitation signal generator. The receiver is configured to receive a parameter associated with a bandwidth-extended audio stream. The high-band excitation signal generator is configured to determine a value of the parameter. The high-band excitation signal generator is also configured, responsive to the value of the parameter, to generate a high-band excitation signal based on target gain information associated with the bandwidth-extended audio stream or based on filter information associated with the bandwidth-extended audio stream. 
     In another particular aspect, a device includes a receiver and a high-band excitation signal generator. The receiver is configured to filter information associated with a bandwidth-extended audio stream audio stream. The high-band excitation signal generator is configured to determine a filter based on the filter information and to generate a modified high-band excitation signal based on application of the filter to a first high-band excitation signal. 
     In another particular aspect, a device includes a high-band excitation signal generator configured to generate a modulated noise signal by applying spectral shaping to a first noise signal and to generate a high-band excitation signal by combining the modulated noise signal and a harmonically extended signal. 
     In another particular aspect, a device includes a receiver and a high-band excitation signal generator. The receiver is configured to receive a low-band voicing factor and a mixing configuration parameter associated with a bandwidth-extended audio stream. The high-band excitation signal generator is configured to determine a high-band mixing configuration based on the low-band voicing factor and the mixing configuration parameter. The high-band excitation signal generator is also configured to generate a high-band excitation signal based on the high-band mixing configuration. 
     In another particular aspect, a signal processing method includes generating, at a device, a resampled signal based on a low-band excitation signal. The method also includes generating, at the device, at least a first excitation signal corresponding to a first high-band frequency sub-range and a second excitation signal corresponding to a second high-band frequency sub-range based on the resampled signal. The first excitation signal is generated based on application of a first function to the resampled signal. The second excitation signal is generated based on application of a second function to the resampled signal. The method also includes generating, at the device, a high-band excitation signal based on the first excitation signal and the second excitation signal. 
     In another particular aspect, a signal processing method includes receiving, at a device, a parameter associated with a bandwidth-extended audio stream. The method also includes selecting, at the device, one or more non-linear processing functions based at least in part on a value of the parameter. The method further includes generating, at the device, a high-band excitation signal based on the one or more non-linear processing functions. 
     In another particular aspect, a signal processing method includes receiving, at a device, a parameter associated with a bandwidth-extended audio stream. The method also includes determining, at the device, a value of the parameter. The method further includes, responsive to the value of the parameter, generating a high-band excitation signal based on target gain information associated with the bandwidth-extended audio stream or based on filter information associated with the bandwidth-extended audio stream. 
     In another particular aspect, a signal processing method includes receiving, at a device, filter information associated with a bandwidth-extended audio stream audio stream. The method also includes determining, at the device, a filter based on the filter information. The method further includes generating, at the device, a modified high-band excitation signal based on application of the filter to a first high-band excitation signal. 
     In another particular aspect, a signal processing method includes generating, at a device, a modulated noise signal by applying spectral shaping to a first noise signal. The method also includes generating, at the device, a high-band excitation signal by combining the modulated noise signal and a harmonically extended signal. 
     In another particular aspect, a signal processing method includes receiving, at a device, a low-band voicing factor and a mixing configuration parameter associated with a bandwidth-extended audio stream. The method also includes determining, at the device, a high-band mixing configuration based on the low-band voicing factor and the mixing configuration parameter. The method further includes generating, at the device, a high-band excitation signal based on the high-band mixing configuration. 
     Other aspects, advantages, and features of the present disclosure will become apparent after review of the entire application, including the following sections: Brief Description of the Drawings, Detailed Description, and the Claims. 
    
    
     
       V. BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a particular illustrative aspect of a system that includes devices that are operable to generate a high-band signal; 
         FIG. 2  is a diagram of another aspect of a system that includes devices that are operable to generate a high-band signal; 
         FIG. 3  is a diagram of another aspect of a system that includes devices that are operable to generate a high-band signal; 
         FIG. 4  is a diagram of another aspect of a system that includes devices that are operable to generate a high-band signal; 
         FIG. 5  is a diagram of a particular illustrative aspect of a resampler that may be included in one or more of the systems of  FIGS. 1-4 ; 
         FIG. 6  is a diagram of a particular illustrative aspect of spectral flipping of a signal that may be performed by one or more of the systems of  FIGS. 1-4 ; 
         FIG. 7  is a flowchart to illustrate an aspect of a method of high band signal generation; 
         FIG. 8  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 9  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 10  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 11  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 12  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 13  is a diagram of another aspect of a system that includes devices that are operable to generate a high-band signal; 
         FIG. 14  is a diagram of components of the system of  FIG. 13 ; 
         FIG. 15  is a diagram to illustrate another aspect of a method of high-band signal generation; 
         FIG. 16  is a diagram to illustrate another aspect of a method of high-band signal generation; 
         FIG. 17  is a diagram of components of the system of  FIG. 13 ; 
         FIG. 18  is a diagram to illustrate another aspect of a method of high-band signal generation; 
         FIG. 19  is a diagram of components of the system of  FIG. 13 ; 
         FIG. 20  is a diagram to illustrate another aspect of a method of high-band signal generation; 
         FIG. 21  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 22  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 23  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 24  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 25  is a flowchart to illustrate another aspect of a method of high band signal generation; 
         FIG. 26  is a block diagram of a device operable to perform high band signal generation in accordance with the systems and methods of  FIGS. 1-25 ; and 
         FIG. 27  is a block diagram of a base station operable to perform high band signal generation in accordance with the systems and methods of  FIGS. 1-26 . 
     
    
    
     VI. DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a particular illustrative aspect of a system that includes devices that are operable to generate a high-band signal is disclosed and generally designated  100 . 
     The system  100  includes a first device  102  in communication, via a network  107 , with a second device  104 . The first device  102  may include a processor  106 . The processor  106  may be coupled to or may include an encoder  108 . The second device  104  may be coupled to or in communication with one or more speakers  122 . The second device  104  may include a processor  116 , a memory  132 , or both. The processor  116  may be coupled to or may include a decoder  118 . The decoder  118  may include a first decoder  134  (e.g., an algebraic code-excited linear prediction (ACELP) decoder) and a second decoder  136  (e.g., a time-domain bandwidth extension (TBE) decoder). In illustrative aspects, one or more techniques described herein may be included in an industry standard, including but not limited to a standard for moving pictures experts group (MPEG)-H three dimensional (3D) audio. 
     The second decoder  136  may include a TBE frame converter  156  coupled to a bandwidth extension module  146 , a decoding module  162 , or both. The decoding module  162  may include a high-band (HB) excitation signal generator  147 , a HB signal generator  148 , or both. The bandwidth extension module  146  may be coupled, via the decoding module to a signal generator  138 . The first decoder  134  may be coupled to the second decoder  136 , the signal generator  138 , or both. For example, the first decoder  134  may be coupled to the bandwidth extension module  146 , the HB excitation signal generator  147 , or both. The HB excitation signal generator  147  may be coupled to the HB signal generator  148 . The memory  132  may be configured to store instructions to perform one or more functions (e.g., a first function  164 , a second function  166 , or both). The first function  164  may include a first non-linear function (e.g., a square function) and the second function  166  may include a second non-linear function (e.g., an absolute value function) that is distinct from the first non-linear function. Alternatively, such functions may be implemented using hardware (e.g., circuitry) at the second device  104 . The memory  132  may be configured to store one or more signals (e.g., a first excitation signal  168 , a second excitation signal  170 , or both). The second device  104  may further include a receiver  192 . In a particular implementation, the receiver  192  may be included in a transceiver. 
     During operation, the first device  102  may receive (or generate) an input signal  114 . The input signal  114  may correspond to speech of one or more users, background noise, silence, or a combination thereof. In a particular aspect, the input signal  114  may include data in the frequency range from approximately 50 hertz (Hz) to approximately 16 kilohertz (kHz). The low-band portion of the input signal  114  and the high-band portion of the input signal  114  may occupy non-overlapping frequency bands of 50 Hz-7 kHz and 7 kHz-16 kHz, respectively. In an alternate aspect, the low-band portion and the high-band portion may occupy non-overlapping frequency bands of 50 Hz-8 kHz and 8 kHz-16 kHz, respectively. In another alternate aspect, the low-band portion and the high-band portion may overlap (e.g., 50 Hz-8 kHz and 7 kHz-16 kHz, respectively). 
     The encoder  108  may generate audio data  126  by encoding the input signal  114 . For example, the encoder  108  may generate a first bit-stream  128  (e.g., an ACELP bit-stream) based on a low-band signal of the input signal  114 . The first bit-stream  128  may include low-band parameter information (e.g., low-band linear prediction coefficients (LPCs), low-band line spectral frequencies (LSFs), or both) and a low-band excitation signal (e.g., a low-band residual of the input signal  114 ). 
     In a particular aspect, the encoder  108  may generate a high-band excitation signal and may encode a high-band signal of the input signal  114  based on the high-band excitation signal. For example, the encoder  108  may generate a second bit-stream  130  (e.g., a TBE bit-stream) based on the high-band excitation signal. The second bit-stream  130  may include bit-stream parameters, as further described with reference to  FIG. 3 . For example, the bit-stream parameters may include one or more bit-stream parameters  160  as illustrated in  FIG. 1 , a non-linear (NL) configuration mode  158 , or a combination thereof. The bit-stream parameters may include high-band parameter information. For example, the second bit-stream  130  may include at least one of high-band LPC coefficients, high-band LSF, high-band line spectral pair (LSP) coefficients, gain shape information (e.g., temporal gain parameters corresponding to sub-frames of a particular frame), gain frame information (e.g., gain parameters corresponding to an energy ratio of high-band to low-band for a particular frame), and/or other parameters corresponding to a high-band portion of the input signal  114 . In a particular aspect, the encoder  108  may determine the high-band LPC coefficients using at least one of a vector quantizer, a hidden markov model (HMM), a gaussian mixture model (GMM), or another model or method. The encoder  108  may determine the high-band LSF, the high-band LSP, or both, based on the LPC coefficients. 
     The encoder  108  may generate high-band parameter information based on the high-band signal of the input signal  114 . For example, a “local” decoder of the first device  102  may emulate the decoder  118  of the second device  104 . The “local” decoder may generate a synthesized audio signal based on the high-band excitation signal. The encoder  108  may generate gain values (e.g., gain shape, gain frame, or both) based on a comparison of the synthesized audio signal and the input signal  114 . For example, the gain values may correspond to a difference between the synthesized audio signal and the input signal  114 . The audio data  126  may include the first bit-stream  128 , the second bit-stream  130 , or both. The first device  102  may transmit the audio data  126  to the second device  104  via the network  107 . 
     The receiver  192  may receive the audio data  126  from the first device  102  and may provide the audio data  126  to the decoder  118 . The receiver  192  may also store the audio data  126  (or portions thereof) in the memory  132 . In an alternate implementation, the memory  132  may store the input signal  114 , the audio data  126 , or both. In this implementation, the input signal  114 , the audio data  126 , or both, may be generated by the second device  104 . For example, the audio data  126  may correspond to media (e.g., music, movies, television shows, etc.) that is stored at the second device  104  or that is being streamed by the second device  104 . 
     The decoder  118  may provide the first bit-stream  128  to the first decoder  134  and the second bit-stream  130  to the second decoder  136 . The first decoder  134  may extract (or decode) low-band parameter information, such as low-band LPC coefficients, low-band LSF, or both, and a low-band (LB) excitation signal  144  (e.g., a low-band residual of the input signal  114 ) from the first bit-stream  128 . The first decoder  134  may provide the LB excitation signal  144  to the bandwidth extension module  146 . The first decoder  134  may generate a LB signal  140  based on the low-band parameters and the LB excitation signal  144  using a particular LB model. The first decoder  134  may provide the LB signal  140  to the signal generator  138 , as shown. 
     The first decoder  134  may determine a LB voicing factor (VF)  154  (e.g., a value from 0.0 to 1.0) based on the LB parameter information. The LB VF  154  may indicate a voiced/unvoiced nature (e.g., strongly voiced, weakly voiced, weakly unvoiced, or strongly unvoiced) of the LB signal  140 . The first decoder  134  may provide the LB VF  154  to the HB excitation signal generator  147 . 
     The TBE frame converter  156  may generate bit-stream parameters by parsing the second bit-stream  130 . For example, the bit-stream parameters may include the bit-stream parameters  160 , the NL configuration mode  158 , or a combination thereof, as further described with reference to  FIG. 3 . The TBE frame converter  156  may provide the NL configuration mode  158  to the bandwidth extension module  146 , the bit-stream parameters  160  to the decoding module  162 , or both. 
     The bandwidth extension module  146  may generate an extended signal  150  (e.g., a harmonically extended high-band excitation signal) based on the LB excitation signal  144 , the NL configuration mode  158 , or both, as described with reference to  FIGS. 4-5 . The bandwidth extension module  146  may provide the extended signal  150  to the HB excitation signal generator  147 . The HB excitation signal generator  147  may synthesize a HB excitation signal  152  based on the bit-stream parameters  160 , the extended signal  150 , the LB VF  154 , or a combination thereof, as further described with reference to  FIG. 4 . The HB signal generator  148  may generate an HB signal  142  based on the HB excitation signal  152 , the bit-stream parameters  160 , or a combination thereof, as further described with reference to  FIG. 4 . The HB signal generator  148  may provide the HB signal  142  to the signal generator  138 . 
     The signal generator  138  may generate an output signal  124  based on the LB signal  140 , the HB signal  142 , or both. For example, the signal generator  138  may generate an upsampled HB signal by upsampling the HB signal  142  by a particular factor (e.g., 2). The signal generator  138  may generate a spectrally flipped HB signal by spectrally flipping the upsampled HB signal in a time-domain, as described with reference to  FIG. 6 . The spectrally flipped HB signal may correspond to a high-band (e.g., 32 kHz) signal. The signal generator  138  may generate an upsampled LB signal by upsampling the LB signal  140  by a particular factor (e.g., 2). The upsampled LB signal may correspond to a 32 kHz signal. The signal generator  138  may generate a delayed HB signal by delaying the spectrally flipped HB signal to time-align the delayed HB signal and the upsampled LB signal. The signal generator  138  may generate the output signal  124  by combining the delayed HB signal and the upsampled LB signal. The signal generator  138  may store the output signal  124  in the memory  132 . The signal generator  138  may output, via the speakers  122 , the output signal  124 . 
     Referring to  FIG. 2 , a system is disclosed and generally designated  200 . In a particular aspect, the system  200  may correspond to the system  100  of  FIG. 1 . The system  200  may include a resampler and filterbank  202 , the encoder  108 , or both. The resampler and filterbank  202 , the encoder  108 , or both, may be included in the first device  102  of  FIG. 1 . The encoder  108  may include a first encoder  204  (e.g., an ACELP encoder) and a second encoder  296  (e.g., a TBE encoder). The second encoder  296  may include an encoder bandwidth extension module  206 , an encoding module  208  (e.g., a TBE encoder), or both. The encoder bandwidth extension module  206  may perform non-linear processing and modeling, as described with reference to  FIG. 13 . In a particular aspect, a receiving/decoding device may be coupled to or may include media storage  292 . For example, the media storage  292  may store encoded media. Audio for the encoded media may be represented by an ACELP bit-stream and a TBE bit-stream. Alternatively, the media storage  292  may correspond to a network accessible server from which the ACELP bit-stream and the TBE bit-stream are received during a streaming session. 
     The system  200  may include the first decoder  134 , the second decoder  136 , the signal generator  138  (e.g., a resampler, a delay adjuster, and a mixer), or a combination thereof. The second decoder  136  may include the bandwidth extension module  146 , the decoding module  162 , or both. The bandwidth extension module  146  may perform non-linear processing and modeling, as described with reference to  FIGS. 1 and 4 . 
     During operation, the resampler and filterbank  202  may receive the input signal  114 . The resampler and filterbank  202  may generate a first LB signal  240  by applying a low-pass filter to the input signal  114  and may provide the first LB signal  240  to the first encoder  204 . The resampler and filterbank  202  may generate a first HB signal  242  by applying a high-pass filter to the input signal  114  and may provide the first HB signal  242  to the encoding module  208 . 
     The first encoder  204  may generate a first LB excitation signal  244  (e.g., an LB residual), the first bit-stream  128 , or both, based on the first LB signal  240 . The first encoder  204  may provide the first LB excitation signal  244  to the encoder bandwidth extension module  206 . The first encoder  204  may provide the first bit-stream  128  to the first decoder  134 . 
     The encoder bandwidth extension module  206  may generate a first extended signal  250  based on the first LB excitation signal  244 . The encoder bandwidth extension module  206  may provide the first extended signal  250  to the encoding module  208 . The encoding module  208  may generate the second bit-stream  130  based on the first HB signal  242  and the first extended signal  250 . For example, the encoding module  208  may generate a synthesized HB signal based on the first extended signal  250 , may generate the bit-stream parameters  160  of  FIG. 1  to reduce a difference between the synthesized HB signal and the first HB signal  242 , and may generate the second bit-stream  130  including the bit-stream parameters  160 . 
     The first decoder  134  may receive the first bit-stream  128  from the first encoder  204 . The decoding module  162  may receive the second bit-stream  130  from the encoding module  208 . In a particular implementation, the first decoder  134  may receive the first bit-stream  128 , the second bit-stream  130 , or both, from the media storage  292 . For example, the first bit-stream  128 , the second bit-stream  130 , or both, may correspond to media (e.g., music or a movie) stored at the media storage  292 . In a particular aspect, the media storage  292  may correspond to a network device that is streaming the first bit-stream  128  to the first decoder  134  and the second bit-stream  130  to the decoding module  162 . The first decoder  134  may generate the LB signal  140 , the LB excitation signal  144 , or both, based on the first bit-stream  128 , as described with reference to  FIG. 1 . The LB signal  140  may include a synthesized LB signal that approximates the first LB signal  240 . The first decoder  134  may provide the LB signal  140  to the signal generator  138 . The first decoder  134  may provide the LB excitation signal  144  to the bandwidth extension module  146 . The bandwidth extension module  146  may generate the extended signal  150  based on the LB excitation signal  144 , as described with reference to  FIG. 1 . The bandwidth extension module  146  may provide the extended signal  150  to the decoding module  162 . The decoding module  162  may generate the HB signal  142  based on the second bit-stream  130  and the extended signal  150 , as described with reference to  FIG. 1 . The HB signal  142  may include a synthesized HB signal that approximates the first HB signal  242 . The decoding module  162  may provide the HB signal  142  to the signal generator  138 . The signal generator  138  may generate the output signal  124  based on the LB signal  140  and the HB signal  142 , as described with reference to  FIG. 1 . 
     Referring to  FIG. 3 , a system is disclosed and generally designated  300 . In a particular aspect, the system  300  may correspond to the system  100  of  FIG. 1 , the system  200  of  FIG. 2 , or both. The system  300  may include the first decoder  134 , the TBE frame converter  156 , the bandwidth extension module  146 , the decoding module  162 , or a combination thereof. The first decoder  134  may include an ACELP decoder, a MPEG decoder, an MPEG-H 3D audio decoder, a linear prediction domain (LPD) decoder, or a combination thereof. 
     During operation, the TBE frame converter  156  may receive the second bit-stream  130 , as described with reference to  FIG. 1 . The second bit-stream  130  may correspond to a data structure tbe_data( ) illustrated in Table 1: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Syntax 
                 No. of bits 
               
               
                   
                   
               
             
            
               
                   
                 tbe_data( ) 
                   
               
               
                   
                 { 
                   
               
               
                   
                  tbe_heMode; 
                 1 
               
               
                   
                  idxFrameGain; 
                 5 
               
               
                   
                  idxSubGains; 
                 5 
               
               
                   
                  lsf_idx[0]; 
                 7 
               
               
                   
                  lsf_idx[1]; 
                 7 
               
               
                   
                  if (tbe_heMode==0) { 
               
            
           
           
               
               
               
            
               
                   
                 tbe_hrConfig; 
                 1 
               
               
                   
                 tbe_nlConfig; 
                 1 
               
               
                   
                 idxMixConfig; 
                 2 
               
               
                   
                 if (tbe_hrConfig==1) { 
                   
               
               
                   
                  idxShbFrGain; 
                 6 
               
               
                   
                  idxResSubGains; 
                 5 
               
               
                   
                 } else { 
                   
               
               
                   
                  idxShbExcResp[0]; 
                 7 
               
               
                   
                  idxShbExcResp[1]; 
                 4 
               
               
                   
                 } 
               
            
           
           
               
               
            
               
                   
                  } 
               
               
                   
                 } 
               
               
                   
                   
               
            
           
         
       
     
     The TBE frame converter  156  may generate the bit-stream parameters  160 , the NL configuration mode  158 , or a combination thereof, by parsing the second bit-stream  130 . The bit-stream parameters  160  may include a high-efficiency (HE) mode  360  (e.g., tbe_heMode), gain information  362  (e.g., idxFrameGain and idxSubGains), HB LSF data  364  (e.g., lsf_idx[0,1]), a high resolution (HR) configuration mode  366  (e.g., tbe_hrConfig), a mix configuration mode  368  (e.g., idxMixConfig, alternatively referred to as a “mixing configuration parameter”), HB target gain data  370  (e.g., idxShbFrGain), gain shape data  372  (e.g., idxResSubGains), filter information  374  (e.g., idxShbExcResp[0,1]), or a combination thereof. The TBE frame converter  156  may provide the NL configuration mode  158  to the bandwidth extension module  146 . The TBE frame converter  156  may also provide one or more of the bit-stream parameters  160  to the decoding module  162 , as shown. 
     In a particular aspect, the filter information  374  may indicate a finite impulse response (FIR) filter. The gain information  362  may include HB reference gain information, temporal sub-frame residual gain shape information, or both. The HB target gain data  370  may indicate frame energy. 
     In a particular aspect, the TBE frame converter  156  may extract the NL configuration mode  158  from the second bit-stream  130  in response to determining that the HE mode  360  has a first value (e.g., 0). Alternatively, the TBE frame converter  156  may set the NL configuration mode  158  to a default value (e.g., 1) in response to determining that the HE mode  360  has a second value (e.g., 1). In a particular aspect, the TBE frame converter  156  may set the NL configuration mode  158  to the default value (e.g., 1) in response to determining that the NL configuration mode  158  has a first particular value (e.g., 2) and that the mix configuration mode  368  has a second particular value (e.g., a value greater than 1). 
     In a particular aspect, the TBE frame converter  156  may extract the HR configuration mode  366  from the second bit-stream  130  in response to determining that the HE mode  360  has the first value (e.g., 0). Alternatively, the TBE frame converter  156  may set the HR configuration mode  366  to a default value (e.g., 0) in response to determining that the HE mode  360  has the second value (e.g., 1). The first decoder  134  may receive the first bit-stream  128 , as described with reference to  FIG. 1 . 
     Referring to  FIG. 4 , a system is disclosed and generally designated  400 . In a particular aspect, the system  400  may correspond to the system  100  of  FIG. 1 , the system  200  of  FIG. 2 , the system  300  of  FIG. 3 , or a combination thereof. The system  400  may include the bandwidth extension module  146 , the HB excitation signal generator  147 , the HB signal generator  148 , or a combination thereof. The bandwidth extension module  146  may include a resampler  402 , a harmonic extension module  404 , or both. The HB excitation signal generator  147  may include a spectral flip and decimation module  408 , an adaptive whitening module  410 , a temporal envelope modulator  412 , an HB excitation estimator  414 , or a combination thereof. The HB signal generator  148  may include an HB linear prediction module  416 , a synthesis module  418 , or both. 
     During operation, the bandwidth extension module  146  may generate the extended signal  150  by extending the LB excitation signal  144 , as described herein. The resampler  402  may receive the LB excitation signal  144  from the first decoder  134  of  FIG. 1 , such as ACELP decoder. The resampler  402  may generate a resampled signal  406  based on the LB excitation signal  144 , as described with reference to  FIG. 5 . The resampler  402  may provide the resampled signal  406  to the harmonic extension module  404 . 
     The harmonic extension module  404  may receive the NL configuration mode  158  from the TBE frame converter  156  of  FIG. 1 . The harmonic extension module  404  may generate the extended signal  150  (e.g., an HB excitation signal) by harmonically extending the resampled signal  406  in a time-domain based on the NL configuration mode  158 . In a particular aspect, the harmonic extension module  404  may generate the extended signal  150  (E HE ) based on Equation 1: 
                     E   HE     =     {                    E   LB          ,       if   ⁢           ⁢   the_nlConfig     =   1                     ɛ   N     ⁢     sign   ⁡     (     E   LB     )       ⁢     E   LB   2       ,       if   ⁢           ⁢   the_nlConfig     =   0                         H   LP     ⁡     (   z   )       ⁢     ɛ   N     ⁢     sign   ⁡     (     E   LB     )       ⁢     E   LB   2       +       H   HP     ⁢          E   LB              ,                 if   ⁢           ⁢   the_nlConfig     =       0   ⁢           ⁢   AND   ⁢           ⁢   idxMixConfig     ≤   1             ,               Equation   ⁢           ⁢   1               
where E LB  corresponds to the resampled signal  406 , ε N  corresponds to an energy normalization factor between E LB  and E LB   2 , and tbe_nlConfig corresponds to the NL configuration mode  158 . The energy normalization factor may correspond to a ratio of frame energies of E LB  and E LB   2 . H LP  and H HP  correspond to a low-pass filter and high-pass filter respectively, with a particular cut-off frequency (e.g., ¾ f s  or approximately 12 kHz). A transfer function of the H LP  may be based on Equation 2:
 
     
       
         
           
             
               
                 
                   
                     
                       
                         H 
                         LP 
                       
                       ⁡ 
                       
                         ( 
                         z 
                         ) 
                       
                     
                     = 
                     
                       
                         0.57 
                         ⁢ 
                         
                           ( 
                           
                             1 
                             + 
                             
                               2 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 z 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             + 
                             
                               z 
                               
                                 - 
                                 2 
                               
                             
                           
                           ) 
                         
                       
                       
                         1 
                         + 
                         
                           0.94 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             z 
                             
                               - 
                               1 
                             
                           
                         
                         + 
                         
                           0.33 
                           ⁢ 
                           
                             z 
                             
                               - 
                               2 
                             
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
               
             
           
         
       
     
     A transfer function of the H HP  may be based on Equation 3: 
     
       
         
           
             
               
                 
                   
                     
                       
                         H 
                         HP 
                       
                       ⁡ 
                       
                         ( 
                         z 
                         ) 
                       
                     
                     = 
                     
                       
                         0.098 
                         ⁢ 
                         
                           ( 
                           
                             1 
                             - 
                             
                               2 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 z 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             + 
                             
                               z 
                               
                                 - 
                                 2 
                               
                             
                           
                           ) 
                         
                       
                       
                         1 
                         + 
                         
                           0.94 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             z 
                             
                               - 
                               1 
                             
                           
                         
                         + 
                         
                           0.33 
                           ⁢ 
                           
                             z 
                             
                               - 
                               2 
                             
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                 
               
             
           
         
       
     
     For example, the harmonic extension module  404  may select the first function  164 , the second function  166 , or both, based on a value of the NL configuration mode  158 . To illustrate, the harmonic extension module  404  may select the first function  164  (e.g., a square function) in response to determining that the NL configuration mode  158  has a first value (e.g., NL_HARMONIC or 0). The harmonic extension module  404  may, in response to selecting the first function  164 , generate the extended signal  150  by applying the first function  164  (e.g., the square function) to the resampled signal  406 . The square function may preserve the sign information of the resampled signal  406  in the extended signal  150  and may square values of the resampled signal  406 . 
     In a particular aspect, the harmonic extension module  404  may select the second function  166  (e.g., an absolute value function) in response to determining that the NL configuration mode  158  has a second value (e.g., NL_SMOOTH or 1). The harmonic extension module  404  may, in response to selecting the second function  166 , generate the extended signal  150  by applying the second function  166  (e.g., the absolute value function) to the resampled signal  406 . 
     In a particular aspect, the harmonic extension module  404  may select a hybrid function in response to determining that the NL configuration mode  158  has a third value (e.g., NL_HYBRID or 2). In this aspect, the TBE frame converter  156  may provide the mix configuration mode  368  to the harmonic extension module  404 . The hybrid function may include a combination of multiple functions (e.g., the first function  164  and the second function  166 ). 
     The harmonic extension module  404  may, in response to selecting the hybrid function, generate a plurality of excitation signals (e.g., at least the first excitation signal  168  and the second excitation signal  170 ) corresponding to a plurality of high-band frequency sub-ranges based on the resampled signal  406 . For example, the harmonic extension module  404  may generate the first excitation signal  168  by applying the first function  164  to the resampled signal  406  or a portion thereof. The first excitation signal  168  may correspond to a first high-band frequency sub-range (e.g., approximately 8-12 kHz). The harmonic extension module  404  may generate the second excitation signal  170  by applying the second function  166  to the resampled signal  406  or a portion thereof. The second excitation signal  170  may correspond to a second high-band frequency sub-range (e.g., approximately 12-16 kHz). 
     The harmonic extension module  404  may generate a first filtered signal by applying a first filter (e.g., a low-pass filter, such as a 8-12 kHz filter) to the first excitation signal  168  and may generate a second filtered signal by applying a second filter (e.g., a high-pass filter, such as a 12-16 kHz filter) to the second excitation signal  170 . The first filter and the second filter may have a particular cut-off frequency (e.g., 12 kHz). The harmonic extension module  404  may generate the extended signal  150  by combining the first filtered signal and the second filtered signal. The first high-band frequency sub-range (e.g., approximately 8-12 kHz) may correspond to harmonic data (e.g., weakly voiced or strongly voiced). The second high-band frequency sub-range (e.g., approximately 12-16 kHz) may correspond to noise-like data (e.g., weakly unvoiced or strongly unvoiced). The harmonic extension module  404  may thus use distinct non-linear processing functions for distinct bands in the spectrum. 
     In a particular implementation, the harmonic extension module  404  may select the second function  166  in response to determining that the NL configuration mode  158  has the second value (e.g., NL_SMOOTH or 1) and that the mix configuration mode  368  has a particular value (e.g., a value greater than 1). Alternatively, the harmonic extension module  404  may select the hybrid function in response to determining that the NL configuration mode  158  has the second value (e.g., NL_SMOOTH or 1) and that the mix configuration mode  368  has another particular value (e.g., a value less than or equal to 1). 
     In a particular aspect, the harmonic extension module  404  may, in response to determining that the HE mode  360  has the first value (e.g., 0), generate the extended signal  150  (e.g., an HB excitation signal) by harmonically extending the resampled signal  406  in a time-domain based on the NL configuration mode  158 . The harmonic extension module  404  may, in response to determining that the HE mode  360  has the second value (e.g., 1), generate the extend signal  150  (e.g., an HB excitation signal) by harmonically extending the resampled signal  406  in a time-domain based on the gain information  362  (e.g., idxSubGains). For example, the harmonic extension module  404  may generate the extended signal  150  using the tbe_nlConfig=1 configuration (e.g., E HE =|E LB |) in response to determining that the gain information  362  (e.g., idxSubGains) corresponds to a particular value (e.g., an odd value) and may generate the extended signal  150  using the tbe_nlConfig=0 configuration (e.g., E HE =ε N sign(E LB )E LB   2 ) otherwise. To illustrate, the harmonic extension module  404  may, in response to determining that the gain information  362  (e.g., idxSubGains) does not correspond to the particular value (e.g., an odd value) or that the gain information  362  (e.g., idxSubGains) corresponds to another value (e.g., an even value), may generate the extended signal  150  using the tbe_nlConfig=0 configuration (e.g., E HE =ε N Sign(E LB )E LB   2 ). 
     The harmonic extension module  404  may provide the extended signal  150  to the spectral flip and decimation module  408 . The spectral flip and decimation module  408  may generate a spectrally flipped signal by performing spectral flipping of the extended signal  150  in the time-domain based on Equation 4:
 
 E   HE   f ( n )=(−1) n   E   HE ( n ),  n= 0,1,2, . . . , N− 1,  Equation 4
 
where E HE   f (n) corresponds to the spectrally flipped signal and N (e.g., 512) corresponds to a number of samples per frame.
 
     The spectral flip and decimation module  408  may generate a first signal  450  (e.g., a HB excitation signal) by decimating the spectrally flipped signal based on a first all-pass filter and a second all-pass filter. The first all-pass filter may correspond to a first transfer function indicated by Equation 5: 
     
       
         
           
             
               
                 
                   
                     
                       H 
                       
                         AP 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                     ⁡ 
                     
                       ( 
                       z 
                       ) 
                     
                   
                   = 
                   
                     
                       ( 
                       
                         
                           
                             a 
                             
                               0 
                               , 
                               1 
                             
                           
                           + 
                           
                             z 
                             
                               - 
                               1 
                             
                           
                         
                         
                           1 
                           + 
                           
                             
                               a 
                               
                                 0 
                                 , 
                                 1 
                               
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       ( 
                       
                         
                           
                             a 
                             
                               1 
                               , 
                               1 
                             
                           
                           + 
                           
                             z 
                             
                               - 
                               1 
                             
                           
                         
                         
                           1 
                           + 
                           
                             
                               a 
                               
                                 1 
                                 , 
                                 1 
                               
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       
                         ( 
                         
                           
                             
                               a 
                               
                                 2 
                                 , 
                                 1 
                               
                             
                             + 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                           
                             1 
                             + 
                             
                               
                                 a 
                                 
                                   2 
                                   , 
                                   1 
                                 
                               
                               ⁢ 
                               
                                 z 
                                 
                                   - 
                                   1 
                                 
                               
                             
                           
                         
                         ) 
                       
                       . 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   5 
                 
               
             
           
         
       
     
     The second all-pass filter may correspond to a second transfer function indicated by Equation 6: 
     
       
         
           
             
               
                 
                   
                     
                       H 
                       
                         AP 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                     ⁡ 
                     
                       ( 
                       z 
                       ) 
                     
                   
                   = 
                   
                     
                       ( 
                       
                         
                           
                             a 
                             
                               0 
                               , 
                               2 
                             
                           
                           + 
                           
                             z 
                             
                               - 
                               1 
                             
                           
                         
                         
                           1 
                           + 
                           
                             
                               a 
                               
                                 0 
                                 , 
                                 2 
                               
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       ( 
                       
                         
                           
                             a 
                             
                               1 
                               , 
                               2 
                             
                           
                           + 
                           
                             z 
                             
                               - 
                               1 
                             
                           
                         
                         
                           1 
                           + 
                           
                             
                               a 
                               
                                 1 
                                 , 
                                 2 
                               
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       
                         ( 
                         
                           
                             
                               a 
                               
                                 2 
                                 , 
                                 2 
                               
                             
                             + 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                           
                             1 
                             + 
                             
                               
                                 a 
                                 
                                   2 
                                   , 
                                   2 
                                 
                               
                               ⁢ 
                               
                                 z 
                                 
                                   - 
                                   1 
                                 
                               
                             
                           
                         
                         ) 
                       
                       . 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   6 
                 
               
             
           
         
       
     
     Exemplary values of the all-pass filter coefficients are provided in Table 2 below: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
            
               
                   
                 a 0,1   
                 0.06056541924291 
               
               
                   
                 a 1,1   
                 0.42943401549235 
               
               
                   
                 a 2,1   
                 0.80873048306552 
               
               
                   
                 a 0,2   
                 0.22063024829630 
               
               
                   
                 a 1,2   
                 0.63593943961708 
               
               
                   
                 a 2,2   
                 0.94151583095682 
               
               
                   
                   
               
            
           
         
       
     
     The spectral flip and decimation module  408  may generate a first filtered signal by applying the first all-pass filter to filter even samples of the spectrally flipped signal. The spectral flip and decimation module  408  may generate a second filtered signal by applying the second all-pass filter to filter odd samples of the spectrally flipped signal. The spectral flip and decimation module  408  may generate the first signal  450  by averaging the first filtered signal and the second filtered signal. 
     The spectral flip and decimation module  408  may provide the first signal  450  to the adaptive whitening module  410 . The adaptive whitening module  410  may generate a second signal  452  (e.g., an HB excitation signal) by flattening a spectrum of the first signal  450  by performing fourth-order LP whitening of the first signal  450 . For example, the adaptive whitening module  410  may estimate auto-correlation coefficients of the first signal  450 . The adaptive whitening module  410  may generate first coefficients by applying bandwidth expansion to the auto-correlation coefficients based on multiplying the auto-correlation coefficients by an expansion function. The adaptive whitening module  410  may generate first LPCs by applying an algorithm (e.g., a Levinson-Durbin algorithm) to the first coefficients. The adaptive whitening module  410  may generate the second signal  452  by inverse filtering the first LPCs. 
     In a particular implementation, the adaptive whitening module  410  may modulate the second signal  452  based on normalized residual energy in response to determining that the HR configuration mode  366  has a particular value (e.g., 1). The adaptive whitening module  410  may determine the normalized residual energy based on the gain shape data  372 . Alternatively, the adaptive whitening module  410  may filter the second signal  452  based on a particular filter (e.g., a FIR filter) in response to determining that the HR configuration mode  366  has a first value (e.g., 0). The adaptive whitening module  410  may determine (or generate) the particular filter based on the filter information  374 . The adaptive whitening module  410  may provide the second signal  452  to the temporal envelope modulator  412 , the HB excitation estimator  414 , or both. 
     The temporal envelope modulator  412  may receive the second signal  452  from the adaptive whitening module  410 , a noise signal  440  from a random noise generator, or both. The random noise generator may be coupled to or may be included in the second device  104 . The temporal envelope modulator  412  may generate a third signal  454  based on the noise signal  440 , the second signal  452 , or both. For example, the temporal envelope modulator  412  may generate a first noise signal by applying temporal shaping to the noise signal  440 . The temporal envelope modulator  412  may generate a signal envelope based on the second signal  452  (or the LB excitation signal  144 ). The temporal envelope modulator  412  may generate the first noise signal based on the signal envelope and the noise signal  440 . For example, the temporal envelope modulator  412  may combine the signal envelope and the noise signal  440 . Combining the signal envelope and the noise signal  440  may modulate amplitude of the noise signal  440 . The temporal envelope modulator  412  may generate the third signal  454  by applying spectral shaping to the first noise signal. In an alternate implementation, the temporal envelope modulator  412  may generate the first noise signal by applying spectral shaping to the noise signal  440  and may generate the third signal  454  by applying temporal shaping to the first noise signal. Thus, spectral and temporal shaping may be applied in any order to the noise signal  440 . The temporal envelope modulator  412  may provide the third signal  454  to the HB excitation estimator  414 . 
     The HB excitation estimator  414  may receive the second signal  452  from the adaptive whitening module  410 , the third signal  454  from the temporal envelope modulator  412 , or both. The HB excitation estimator  414  may generate the HB excitation signal  152  by combining the second signal  452  and the third signal  454 . 
     In a particular aspect, the HB excitation estimator  414  may combine the second signal  452  and the third signal  454  based on the LB VF  154 . For example, the HB excitation estimator  414  may determine a HB VF based on one or more LB parameters. The HB VF may correspond to a HB mixing configuration. The one or more LB parameters may include the LB VF  154 . The HB excitation estimator  414  may determine the HB VF based on application of a sigmoid function on the LB VF  154 . For example, the HB excitation estimator  414  may determine the HB VF based on Equation 7: 
     
       
         
           
             
               
                 
                   
                     
                       VF 
                       i 
                     
                     = 
                     
                       1 
                       
                         1 
                         + 
                         
                           e 
                           
                             
                               - 
                               4 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               α 
                               i 
                             
                           
                         
                       
                     
                   
                   , 
                   
                     i 
                     = 
                     1 
                   
                   , 
                   2 
                   , 
                   3 
                   , 
                   4 
                   , 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   7 
                 
               
             
           
         
       
     
     where VF i  may correspond to a HB VF corresponding to a sub-frame i, and α i  may correspond to a normalized correlation from the LB. In a particular aspect, α i  may correspond to the LB VF  154  for the sub-frame i. The HB excitation estimator  414  may “smoothen” the HB VF to account for sudden variations in the LB VF  154 . For example the HB excitation estimator  414  may reduce variations in the HB VF based on the mix configuration mode  368  in response to determining that the HR configuration mode  366  has a particular value (e.g., 1). Modifying the HB VF based on the mix configuration mode  368  may compensate for a mismatch between the LB VF  154  and the HB VF. The HB excitation estimator  414  may power normalize the third signal  454  so that the third signal  454  has the same power level as the second signal  452 . 
     The HB excitation estimator  414  may determine a first weight (e.g., HB VF) and a second weight (e.g., 1−HB VF). The HB excitation estimator  414  may generate the HB excitation signal  152  by performing a weighted sum of the second signal  452  and the third signal  454 , where the first weight is assigned to the second signal  452  and the second weight is assigned to the third signal  454 . For example, the HB excitation estimator  414  may generate sub-frame (i) of the HB excitation signal  152  by mixing sub-frame (i) of the second signal  452  that is scaled based on VF i  (e.g., scaled based on a square root of VF i ) and sub-frame (i) of the third signal  454  that is scaled based on (1−VF i ) (e.g., scaled based on a square root of (1−VF i )). The HB excitation estimator  414  may provide the HB excitation signal  152  to the synthesis module  418 . 
     The HB linear prediction module  416  may receive the bit-stream parameters  160  from the TBE frame converter  156 . The HB linear prediction module  416  may generate LSP coefficients  456  based on the HB LSF data  364 . For example, the HB linear prediction module  416  may determine LSFs based on the HB LSF data  364  and may convert the LSFs to the LSP coefficients  456 . The bit-stream parameters  160  may correspond to a first audio frame of a sequence of audio frames. The HB linear prediction module  416  may interpolate the LSP coefficients  456  based on second LSP coefficients associated with another frame in response to determining that the other frame corresponds to a TBE frame. The other frame may precede the first audio frame in the sequence of audio frames. The LSP coefficients  456  may be interpolated over a particular number of (e.g., four) sub-frames. The HB linear prediction module  416  may refrain from interpolating the LSP coefficients  456  in response to determining that the other frame does not correspond to a TBE frame. The HB linear prediction module  416  may provide the LSP coefficients  456  to the synthesis module  418 . 
     The synthesis module  418  may generate the HB signal  142  based on the LSP coefficients  456 , the HB excitation signal  152 , or both. For example, the synthesis module  418  may generate (or determine) high-band synthesis filters based on the LSP coefficients  456 . The synthesis module  418  may generate a first HB signal by applying the high-band synthesis filters to the HB excitation signal  152 . The synthesis module  418  may, in response to determining that the HR configuration mode  366  has a particular value (e.g., 1), perform a memory-less synthesis to generate the first HB signal. For example, the first HB signal may be generated with past LP filter memories set to zero. The synthesis module  418  may match energy of the first HB signal to target signal energy indicated by the HB target gain data  370 . The gain information  362  may include frame gain information and gain shape information. The synthesis module  418  may generate scaled HB signal by scaling the first HB signal based on the gain shape information. The synthesis module  418  may generate the HB signal  142  by multiplying the scaled HB signal by gain frame indicated by the frame gain information. The synthesis module  418  may provide the HB signal  142  to the signal generator  138  of  FIG. 1 . 
     In a particular implementation, the synthesis module  418  may modify the HB excitation signal  152  prior to generating the first HB signal. For example, the synthesis module  418  may generate a modified HB excitation signal based on the HB excitation signal  152  and may generate the first HB signal by applying the high-band synthesis filters to the modified HB excitation signal. To illustrate, the synthesis module  418  may, in response to determining that the HR configuration mode  366  has a first value (e.g., 0), generate a filter (e.g., a FIR filter) based on the filter information  374 . The synthesis module  418  may generate the modified HB excitation signal by applying the filter to at least a portion (e.g., a harmonic portion) of the HB excitation signal  152 . Applying the filter to the HB excitation signal  152  may reduce distortion between the HB signal  142  generated at the second device  104  and an HB signal of the input signal  114 . Alternatively, the synthesis module  418  may, in response to determining that the HR configuration mode  366  has a second value (e.g., 1), generate the modified HB excitation signal based on target gain information. The target gain information may include the gain shape data  372 , the HB target gain data  370 , or both. 
     In a particular implementation, the HB excitation estimator  414  may modify the second signal  452  prior to generating the HB excitation signal  152 . For example, the HB excitation estimator  414  may generate a modified second signal based on the second signal  452  and may generate the HB excitation signal  152  by combining the modified second signal and the third signal  454 . To illustrate, the HB excitation estimator  414  may, in response to determining that the HR configuration mode  366  has a first value (e.g., 0), generate a filter (e.g., a FIR filter) based on the filter information  374 . The HB excitation estimator  414  may generate the modified second signal by applying the filter to at least a portion (e.g., a harmonic portion) of the second signal  452 . Alternatively, the HB excitation estimator  414  may, in response to determining that the HR configuration mode  366  has a second value (e.g., 1), generate the modified second signal based on target gain information. The target gain information may include the gain shape data  372 , the HB target gain data  370 , or both. 
     Referring to  FIG. 5 , the resampler  402  is shown. The resampler  402  may include a first scaling module  502 , a resampling module  504 , an adder  514 , a second scaling module  508 , or a combination thereof. 
     During operation, the first scaling module  502  may receive the LB excitation signal  144  and may generate a first scaled signal  510  by scaling the LB excitation signal  144  based on a fixed codebook (FCB) gain (g c ). The first scaling module  502  may provide the first scaled signal  510  to the resampling module  504 . The resampling module  504  may generate a resampled signal  512  by upsampling the first scaled signal  510  by a particular factor (e.g.,  2 ). The resampling module  504  may provide the resampled signal  512  to the adder  514 . The second scaling module  508  may generate a second scaled signal  516  by scaling a second resampled signal  515  based on a pitch gain (g p ). The second resampled signal  515  may correspond to a previous resampled signal. For example, the resampled signal  406  may correspond to an nth audio frame of a sequence of frames. The previous resampled signal may correspond to the (n−1)th audio frame of the sequence of frames. The second scaling module  508  may provide the second scaled signal  516  to the adder  514 . The adder  514  may combine the resampled signal  512  and the second scaled signal  516  to generate the resampled signal  406 . The adder  514  may provide the resampled signal  406  to the second scaling module  508  to be used during processing of the (n+1)th audio frame. The adder  514  may provide the resampled signal  406  to the harmonic extension module  404  of  FIG. 4 . 
     Referring to  FIG. 6 , a diagram is shown and generally designated  600 . The diagram  600  may illustrate spectral flipping of a signal. The spectral flipping of the signal may be performed by one or more of the systems of  FIGS. 1-4 . For example, the signal generator  138  may perform a spectral flipping of the high-band signal  142  in the time-domain, as described with reference to  FIG. 1 . The diagram  600  includes a first graph  602  and a second graph  604 . 
     The first graph  602  may correspond to a first signal prior to spectral flipping. The first signal may correspond to the high-band signal  142 . For example, the first signal may include an upsampled HB signal generated by upsampling the high-band signal  142  by a particular factor (e.g.,  2 ), as described with reference to  FIG. 1 . The second graph  604  may correspond to a spectrally flipped signal generated by spectrally flipping the first signal. For example, the spectrally flipped signal may be generated by spectrally flipping the upsampled HB signal in a time-domain. The first signal may be flipped at a particular frequency (e.g., f s /2 or approximately 8 kHz). Data of the first signal in a first frequency range (e.g., 0−f s /2) may correspond to second data of the spectrally flipped signal in a second frequency range (e.g., f s −f s /2). 
     Referring to  FIG. 7 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  700 . The method  700  may be performed by one or more components of the systems  100 - 400  of  FIGS. 1-4 . For example, the method  700  may be performed by the second device  104 , the bandwidth extension module  146  of  FIG. 1 , the resampler  402 , the harmonic extension module  404  of  FIG. 4 , or a combination thereof. 
     The method  700  includes generating, at a device, a resampled signal based on a low-band excitation signal, at  702 . For example, the resampler  402  may generate the resampled signal  406 , as described with reference to  FIG. 4 . 
     The method  700  also includes generating, at the device, at least a first excitation signal corresponding to a first high-band frequency sub-range and a second excitation signal corresponding to a second high-band frequency sub-range based on the resampled signal, at  704 . For example, the harmonic extension module  404  may generate at least the first excitation signal  168  and the second excitation signal  170  based on the resampled signal  406 , as described with reference to  FIG. 4 . The first excitation signal  168  may correspond to a first high-band frequency sub-range (e.g., 8-12 kHz). The second excitation signal  170  may correspond to a second high-band frequency sub-range (e.g., 12-16 kHz). The harmonic extension module  404  may generate the first excitation signal  168  based on application of the first function  164  to the resampled signal  406 . The harmonic extension module  404  may generate the second excitation signal  170  based on application of the second function  166  to the resampled signal  406 . 
     The method  700  further includes generating, at the device, a high-band excitation signal based on the first excitation signal and the second excitation signal, at  706 . For example, the harmonic extension module  404  may generate the extended signal  150  based on the first excitation signal  168  and the second excitation signal  170 , as described with reference to  FIG. 4 . 
     Referring to  FIG. 8 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  800 . The method  800  may be performed by one or more components of the systems  100 - 400  of  FIGS. 1-4 . For example, the method  800  may be performed by the second device  104 , the receiver  192 , the bandwidth extension module  146  of  FIG. 1 , the harmonic extension module  404  of  FIG. 4 , or a combination thereof. 
     The method  800  includes receiving, at a device, a parameter associated with a bandwidth-extended audio stream, at  802 . For example, the receiver  192  may receive the NL configuration mode  158  associated with the audio data  126 , as described with reference to  FIGS. 1 and 3 . 
     The method  800  also includes selecting, at the device, one or more non-linear processing functions based at least in part on a value of the parameter, at  804 . For example, the harmonic extension module  404  may select the first function  164 , the second function  166 , or both, based at least in part on a value of the NL configuration mode  158 . 
     The method  800  further includes generating, at the device, a high-band excitation signal based on the one or more non-linear processing functions, at  806 . For example, the harmonic extension module  404  may generate the extended signal  150  based on the first function  164 , the second function  166 , or both. 
     Referring to  FIG. 9 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  900 . The method  900  may be performed by one or more components of the systems  100 - 400  of  FIGS. 1-4 . For example, the method  900  may be performed by the second device  104 , the receiver  192 , the HB excitation signal generator  147 , the decoding module  162 , the second decoder  136 , the decoder  118 , the processor  116  of  FIG. 1 , or a combination thereof. 
     The method  900  includes receiving, at a device, a parameter associated with a bandwidth-extended audio stream, at  902 . For example, the receiver  192  may receive the HR configuration mode  366  associated with the audio data  126 , as described with reference to  FIGS. 1 and 3 . 
     The method  900  also includes determining, at the device, a value of the parameter, at  904 . For example, the synthesis module  418  may determine a value of the HR configuration mode  366 , as described with reference to  FIG. 4 . 
     The method  900  further includes, responsive to the value of the parameter, generating a high-band excitation signal based on target gain information associated with the bandwidth-extended audio stream or based on filter information associated with the bandwidth-extended audio stream, at  906 . For example, when the value of the HR configuration mode  366  is 1, the synthesis module  418  may generate a modified excitation signal based on target gain information, such as one or more of the gain shape data  372 , the HB target gain data  370 , or the gain information  362 , as described with reference to  FIG. 4 . When the value of the HR configuration mode  366  is 0, the synthesis module  418  may generate the modified excitation signal based on the filter information  374 , as described with reference to  FIG. 4 . 
     Referring to  FIG. 10 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  1000 . The method  1000  may be performed by one or more components of the systems  100 - 400  of  FIGS. 1-4 . For example, the method  1000  may be performed by the second device  104 , the receiver  192 , the HB excitation signal generator  147  of  FIG. 1 , or a combination thereof. 
     The method  1000  includes receiving, at a device, filter information associated with a bandwidth-extended audio stream audio stream, at  1002 . For example, the receiver  192  may receive the filter information  374  associated with the audio data  126 , as described with reference to  FIGS. 1 and 3 . 
     The method  1000  also includes determining, at the device, a filter based on the filter information, at  1004 . For example, the synthesis module  418  may determine a filter (e.g., FIR filter coefficients) based on the filter information  374 , as described with reference to  FIG. 4 . 
     The method  1000  further includes generating, at the device, a modified high-band excitation signal based on application of the filter to a first high-band excitation signal, at  1006 . For example, the synthesis module  418  may generate a modified high band excitation signal based on application of the filter to the HB excitation signal  152 , as described with reference to  FIG. 4 . 
     Referring to  FIG. 11 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  1100 . The method  1100  may be performed by one or more components of the systems  100 - 400  of  FIGS. 1-4 . For example, the method  1100  may be performed by the second device  104 , the HB excitation signal generator  147  of  FIG. 1 , or both. 
     The method  1100  includes generating, at a device, a modulated noise signal by applying spectral shaping to a first noise signal, at  1102 . For example, the HB excitation estimator  414  may generate a modulated noise signal by applying spectral shaping to a first signal, as described with reference to  FIG. 4 . The first signal may be based on the noise signal  440 . 
     The method  1100  also includes generating, at the device, a high-band excitation signal by combining the modulated noise signal and a harmonically extended signal, at  1104 . For example, the HB excitation estimator  414  may generate the HB excitation signal  152  by combining the modulated noise signal and the second signal  442 . The second signal  442  may be based on the extended signal  150 . 
     Referring to  FIG. 12 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  1200 . The method  1200  may be performed by one or more components of the systems  100 - 400  of  FIGS. 1-4 . For example, the method  1200  may be performed by the second device  104 , the receiver  192 , the HB excitation signal generator  147  of  FIG. 1 , or a combination thereof. 
     The method  1200  includes receiving, at a device, a low-band voicing factor and a mixing configuration parameter associated with a bandwidth-extended audio stream, at  1202 . For example, the receiver  192  may receive the LB VF  154  and the mix configuration mode  368  associated with the audio data  126 , as described with reference to  FIG. 1 . 
     The method  1200  also includes determining, at the device, a high-band voicing factor based on the low-band voicing factor and the mixing configuration parameter, at  1204 . For example, the HB excitation estimator  414  may determine a HB VF based on the LB VF  154  and the mix configuration mode  368 , as described with reference to  FIG. 4 . In an illustrative aspect, the HB excitation estimator  414  may determine the HB VF based on application of a sigmoid function to the LB VF  154 . 
     The method  1200  further includes generating, at the device, a high-band excitation signal based on the high-band mixing configuration, at  1206 . For example, the HB excitation estimator  414  may generate the HB excitation signal  152  based on the HB VF, as described with reference to  FIG. 4 . 
     Referring to  FIG. 13 , a particular illustrative aspect of a system that includes devices that are operable to generate a high-band signal is disclosed and generally designated  1300 . 
     The system  1300  includes the first device  102  in communication, via the network  107 , with the second device  104 . The first device  102  may include the processor  106 , a memory  1332 , or both. The processor  106  may be coupled to or may include the encoder  108 , the resampler and filterbank  202 , or both. The encoder  108  may include the first encoder  204  (e.g., an ACELP encoder) and the second encoder  296  (e.g., a TBE encoder). The second encoder  296  may include the encoder bandwidth extension module  206 , the encoding module  208 , or both. The encoding module  208  may include a high-band (HB) excitation signal generator  1347 , a bit-stream parameter generator  1348 , or both. The second encoder  296  may further include a configuration module  1305 , an energy normalizer  1306 , or both. The resampler and filterbank  202  may be coupled to the first encoder  204 , the second encoder  296 , one or more microphones  1338 , or a combination thereof. 
     The memory  1332  may be configured to store instructions to perform one or more functions (e.g., the first function  164 , the second function  166 , or both). The first function  164  may include a first non-linear function (e.g., a square function) and the second function  166  may include a second non-linear function (e.g., an absolute value function) that is distinct from the first non-linear function. Alternatively, such functions may be implemented using hardware (e.g., circuitry) at the first device  102 . The memory  1332  may be configured to store one or more signals (e.g., a first excitation signal  1368 , a second excitation signal  1370 , or both). The first device  102  may further include a transmitter  1392 . In a particular implementation, the transmitter  1392  may be included in a transceiver. 
     During operation, the first device  102  may receive (or generate) an input signal  114 . For example, the resampler and filterbank  202  may receive the input signal  114  via the microphones  1338 . The resampler and filterbank  202  may generate the first LB signal  240  by applying a low-pass filter to the input signal  114  and may provide the first LB signal  240  to the first encoder  204 . The resampler and filterbank  202  may generate the first HB signal  242  by applying a high-pass filter to the input signal  114  and may provide the first HB signal  242  to the second encoder  296 . 
     The first encoder  204  may generate the first LB excitation signal  244  (e.g., an LB residual), the first bit-stream  128 , or both, based on the first LB signal  240 . The first bit-stream  128  may include LB parameter information (e.g., LPC coefficients, LSFs, or both). The first encoder  204  may provide the first LB excitation signal  244  to the encoder bandwidth extension module  206 . The first encoder  204  may provide the first bit-stream  128  to the first decoder  134  of  FIG. 1 . In a particular aspect, the first encoder  204  may store the first bit-stream  128  in the memory  1332 . The audio data  126  may include the first bit-stream  128 . 
     The first encoder  204  may determine a LB voicing factor (VF)  1354  (e.g., a value from 0.0 to 1.0) based on the LB parameter information. The LB VF  1354  may indicate a voiced/unvoiced nature (e.g., strongly voiced, weakly voiced, weakly unvoiced, or strongly unvoiced) of the first LB signal  240 . The first encoder  204  may provide the LB VF  1354  to the configuration module  1305 . The first encoder  204  may determine an LB pitch based on the first LB signal  240 . The first encoder  204  may provide LB pitch data  1358  indicating the LB pitch to the configuration module  1305 . 
     The configuration module  1305  may generate estimated mix factors (e.g., mix factors  1353 ), a harmonicity indicator  1364  (e.g., indicating a high band coherence), a peakiness indicator  1366 , the NL configuration mode  158 , or a combination thereof, as described with reference to  FIG. 14 . The configuration module  1305  may provide the NL configuration mode  158  to the encoder bandwidth extension module  206 . The configuration module  1305  may provide the harmonicity indicator  1364 , the mix factors  1353 , or both, to the HB excitation signal generator  1347 . 
     The encoder bandwidth extension module  206  may generate the first extended signal  250  based on the first LB excitation signal  244 , the NL configuration mode  158 , or both, as described with reference to  FIG. 17 . The encoder bandwidth extension module  206  may provide the first extended signal  250  to the energy normalizer  1306 . The energy normalizer  1306  may generate a second extended signal  1350  based on the first extended signal  250 , as described with reference to  FIG. 19 . 
     The energy normalizer  1306  may provide the second extended signal  1350  to the encoding module  208 . The HB excitation signal generator  1347  may generate an HB excitation signal  1352  based on the second extended signal  1350 , as described with reference to  FIG. 17 . The bit-stream parameter generator  1348  may generate the bit-stream parameters  160  to reduce a difference between the HB excitation signal  1352  and the first HB signal  242 . The encoding module  208  may generate the second bit-stream  130  including the bit-stream parameters  160 , the NL configuration mode  158 , or both. The audio data  126  may include the first bit-stream  128 , the second bit-stream  130 , or both. The first device  102  may transmit the audio data  126 , via the transmitter  1392 , to the second device  104 . The second device  104  may generate the output signal  124  based on the audio data  126 , as described with reference to  FIG. 1 . 
     Referring to  FIG. 14 , a diagram of an illustrative aspect of the configuration module  305  is depicted. The configuration module  1305  may include a peakiness estimator  1402 , a LB to HB pitch extension measure estimator  1404 , a configuration mode generator  1406 , or a combination thereof. 
     The configuration module  1305  may generate a particular HB excitation signal (e.g., an HB residual) associated with the first HB signal  242 . The peakiness estimator  1402  may determine the peakiness indicator  1366  based on the first HB signal  242  or the particular HB excitation signal. The peakiness indicator  1366  may correspond to a peak-to-average energy ratio associated with the first HB signal  242  or the particular HB excitation signal. The peakiness indicator  1366  may thus indicate a level of temporal peakiness of the first HB signal  242 . The peakiness estimator  1402  may provide the peakiness indicator  1366  to the configuration mode generator  1406 . The peakiness estimator  1402  may also store the peakiness indicator  1366  in the memory  1332  of  FIG. 13 . 
     The LB to HB pitch extension measure estimator  1404  may determine the harmonicity indicator  1364  (e.g., a LB to HB pitch extension measure) based on the first HB signal  242  or the particular HB excitation signal, as described with reference to  FIG. 15 . The harmonicity indicator  1364  may indicate a voicing strength of the first HB signal  242  (or the particular HB excitation signal). The LB to HB pitch extension measure estimator  1404  may determine the harmonicity indicator  1364  based on the LB pitch data  1358 . For example, the LB to HB pitch extension measure estimator  1404  may determine a pitch lag based on a LB pitch indicated by the LB pitch data  1358  and may determine auto-correlation coefficients corresponding to the first HB signal  242  (or the particular HB excitation signal) based on the pitch lag. The harmonicity indicator  1364  may indicate a particular (e.g., maximum) value of the auto-correlation coefficients. The harmonicity indicator  1364  may thus be distinguished from an indicator of tonal harmonicity. The LB to HB pitch extension measure estimator  1404  may provide the harmonicity indicator  1364  to the configuration mode generator  1406 . The LB to HB pitch extension measure estimator  1404  may also store the harmonicity indicator  1364  in the memory  1332  of  FIG. 13 . 
     The LB to HB pitch extension measure estimator  1404  may determine the mix factors  1353  based on the LB VF  1354 . For example, the HB excitation estimator  414  may determine a HB VF based on the LB VF  1354 . The HB VF may correspond to a HB mixing configuration. In a particular aspect, the LB to HB pitch extension measure estimator  1404  determines the HB VF based on application of a sigmoid function to the LB VF  1354 . For example, the LB to HB pitch extension measure estimator  1404  may determine the HB VF based on Equation 7, as described with reference to  FIG. 4 , where VF i  may correspond to a HB VF corresponding to a sub-frame i, and α i  may correspond to a normalized correlation from the LB. In a particular aspect, α i  of Equation 7 may correspond to the LB VF  1354  for the sub-frame i. The LB to HB pitch extension measure estimator  1404  may determine a first weight (e.g., HB VF) and a second weight (e.g., 1−HB VF). The mix factors  1353  may indicate the first weight and the second weight. The LB to HB pitch extension measure estimator  1404  may also store the mix factors  1353  in the memory  1332  of  FIG. 13 . 
     The configuration mode generator  1406  may generate the NL configuration mode  158  based on the peakiness indicator  1366 , the harmonicity indicator  1364 , or both. For example, the configuration mode generator  1406  may generate the NL configuration mode  158  based on the harmonicity indicator  1364 , as described with reference to  FIG. 16 . 
     In a particular implementation, the configuration mode generator  1406  may generate the NL configuration mode  158  having a first value (e.g., NL_HARMONIC or 0) in response to determining that the harmonicity indicator  1364  satisfies a first threshold, that the peakiness indicator  1366  satisfies a second threshold, or both. The configuration mode generator  1406  may generate the NL configuration mode  158  having a second value (e.g., NL_SMOOTH or 1) in response to determining that the harmonicity indicator  1364  fails to satisfy the first threshold, that the peakiness indicator  1366  fails to satisfy the second threshold, or both. The configuration mode generator  1406  may generate the NL configuration mode  158  having a third value (e.g., NL_HYBRID or 2) in response to determining that the harmonicity indicator  1364  fails to satisfy the first threshold and that the peakiness indicator  1366  satisfies the second threshold. In another aspect, the configuration mode generator  1406  may generate the NL configuration mode  158  having the third value (e.g., NL_HYBRID or 2) in response to determining that the harmonicity indicator  1364  satisfies the first threshold and that the peakiness indicator  1366  fails to satisfy the second threshold. 
     In a particular implementation, the configuration module  1305  may generate the NL configuration mode  158  having the second value (e.g., NL_SMOOTH or 1) and the mix configuration mode  368  of  FIG. 3  having a particular value (e.g., a value greater than 1) in response to determining that the harmonicity indicator  1364  fails to satisfy the first threshold, that the peakiness indicator  1366  fails to satisfy the second threshold, or both. The configuration module  1305  may generate the NL configuration mode  158  having the second value (e.g., NL_SMOOTH or 1) and the mix configuration mode  368  having another particular value (e.g., a value less than or equal to 1) in response to determining that one of the harmonicity indicator  1364  and the peakiness indicator  1366  satisfies a corresponding threshold and the other of the harmonicity indicator  1364  and the peakiness indicator  1366  fails to satisfy a corresponding threshold. The configuration mode generator  1406  may also store the NL configuration mode  158  in the memory  1332  of  FIG. 13 . 
     Advantageously, determining the NL configuration mode  158  based on high band parameters (e.g., the peakiness indicator  1366 , the harmonicity indicator  1364 , or both) may be robust to cases where there is little (e.g., no) correlation between the first LB signal  240  and the first HB signal  242 . For example, the high-band signal  142  may approximate the first HB signal  242  when the NL configuration mode  158  is determined based on the high band parameters. 
     Referring to  FIG. 15 , a diagram of an illustrative aspect of a method of high band signal generation is shown and generally designated  1500 . The method  1500  may be performed by one or more components of the systems  100 - 200 ,  1300 - 1400  of  FIGS. 1-2, 13-14 . For example, the method  1500  may be performed by the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the second encoder  296  of  FIG. 2 , the configuration module  1305  of  FIG. 13 , the LB to HB pitch extension measure estimator  1404  of  FIG. 14 , or a combination thereof. 
     The method  1500  may include estimating an auto-correlation of a HB signal at lag indices (T−L to T+L), at  1502 . For example, the configuration module  1305  of  FIG. 13  may generate a particular HB excitation signal (e.g., an HB residual signal) based on the first HB signal  242 . The LB to HB pitch extension measure estimator  1404  of  FIG. 14  may generate an auto-correlation signal (e.g., auto-correlation coefficients  1512 ) based on the first HB signal  242  or the particular HB excitation signal. The LB to HB pitch extension measure estimator  1404  may generate the auto-correlation coefficients  1512  (R) based on lag indices within a threshold distance (e.g., T−L to T+L) of an LB pitch (T) indicated by the LB pitch data  1358 . The auto-correlation coefficients  1512  may include a first number (e.g., 2L) of coefficients. 
     The method  1500  may also include interpolating the auto-correlation coefficients (R), at  1506 . For example, the LB to HB pitch extension measure estimator  1404  of  FIG. 14  may generate second auto-correlation coefficients  1514  (R_interp) by applying a windowed sinc function  1504  to the auto-correlation coefficients  1512  (R). The windowed sinc function  1504  may correspond to a scaling factor (e.g., N). The second auto-correlation coefficients  1514  (R_interp) may include a second number (e.g., 2LN) of coefficients. 
     The method  1500  includes estimating normalized, interpolated auto-correlation coefficients, at  1508 . For example, the LB to HB pitch extension measure estimator  1404  may determine a second auto-correlation signal (e.g., normalized auto-correlation coefficients) by normalizing the second auto-correlation coefficients  1514  (R_interp). The LB to HB pitch extension measure estimator  1404  may determine the harmonicity indicator  1364  based on a particular (e.g., maximum) value of the second auto-correlation signal (e.g., the normalized auto-correlation coefficients). The harmonicity indicator  1364  may indicate a strength of a repetitive pitch component in the first HB signal  242 . The harmonicity indicator  1364  may indicate a relative coherence associated with the first HB signal  242 . The harmonicity indicator  1364  may indicate an LB pitch to HB pitch extension measure. 
     Referring to  FIG. 16 , a diagram of an illustrative aspect of a method of high band signal generation is shown and generally designated  1600 . The method  1600  may be performed by one or more components of the systems  100 - 200 ,  1300 - 1400  of  FIGS. 1-2, 13-14 . For example, the method  1600  may be performed by the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the second encoder  296  of  FIG. 2 , the configuration module  1305  of  FIG. 13 , the configuration mode generator  1406  of  FIG. 14 , or a combination thereof. 
     The method  1600  includes determining whether an LB to HB pitch extension measure satisfies a threshold, at  1602 . For example, the configuration mode generator  1406  of  FIG. 14  may determine whether the harmonicity indicator  1364  (e.g., an LB to HB pitch extension measure) satisfies a first threshold. 
     The method  1600  includes, in response to determining that the LB to HB pitch extension measure satisfies the threshold, at  1602 , selecting a first NL configuration mode, at  1604 . For example, the configuration mode generator  1406  of  FIG. 14  may, in response to determining that the harmonicity indicator  1364  satisfies the first threshold, generate the NL configuration mode  158  having a first value (e.g., NL_HARMONIC or 0). 
     Alternatively, in response to determining that the LB to HB pitch extension measure fails to satisfy the threshold, at  1602 , the method  1600  determining whether the LB to HB pitch extension measure fails to satisfy a second threshold, at  1606 . For example, the configuration mode generator  1406  of  FIG. 14  may, in response to determining that the harmonicity indicator  1364  fails to satisfy the first threshold, determine whether the harmonicity indicator  1364  satisfies a second threshold. 
     The method  1600  includes, in response to determining that the LB to HB pitch extension measure satisfies the second threshold, at  1606 , selecting a second NL configuration mode, at  1608 . For example, the configuration mode generator  1406  of  FIG. 14  may, in response to determining that the harmonicity indicator  1364  satisfies the second threshold, generate the NL configuration mode  158  having a second value (e.g., NL_SMOOTH or 1). 
     In response to determining that the LB to HB pitch extension measure fails to satisfy the second threshold, at  1606 , the method  1600  includes selecting a third NL configuration mode, at  1610 . For example, the configuration mode generator  1406  of  FIG. 14  may, in response to determining that the harmonicity indicator  1364  fails to satisfy the second threshold, generate the NL configuration mode  158  having a third value (e.g., NL_HYBRID or 2). 
     Referring to  FIG. 17 , a system is disclosed and generally designated  1700 . In a particular aspect, the system  1700  may correspond to the system  100  of  FIG. 1 , the system  200  of  FIG. 2 , the system  1300  of  FIG. 13 , or a combination thereof. The system  1700  may include the encoder bandwidth extension module  206 , the energy normalizer  1306 , the HB excitation signal generator  1347 , the bit-stream parameter generator  1348 , or a combination thereof. The encoder bandwidth extension module  206  may include the resampler  402 , the harmonic extension module  404 , or both. The HB excitation signal generator  1347  may include the spectral flip and decimation module  408 , the adaptive whitening module  410 , the temporal envelope modulator  412 , the HB excitation estimator  414 , or a combination thereof. 
     During operation, the encoder bandwidth extension module  206  may generate the first extended signal  250  by extending the first LB excitation signal  244 , as described herein. The resampler  402  may receive the first LB excitation signal  244  from the first encoder  204  of  FIGS. 2 and 13 . The resampler  402  may generate a resampled signal  1706  based on the first LB excitation signal  244 , as described with reference to  FIG. 5 . The resampler  402  may provide the resampled signal  1706  to the harmonic extension module  404 . 
     The harmonic extension module  404  may generate the first extended signal  250  (e.g., an HB excitation signal) by harmonically extending the resampled signal  1706  in a time-domain based on the NL configuration mode  158 , as described with reference to  FIG. 4 . The NL configuration mode  158  may be generated by the configuration module  1305 , as described with reference to  FIG. 14 . For example, the harmonic extension module  404  may select the first function  164 , the second function  166 , or a hybrid function based on a value of the NL configuration mode  158 . The hybrid function may include a combination of multiple functions (e.g., the first function  164  and the second function  166 ). The harmonic extension module  404  may generate the first extended signal  250  based on the selected function (e.g., the first function  164 , the second function  166 , or the hybrid function). 
     The harmonic extension module  404  may provide the first extended signal  150  to the energy normalizer  1306 . The energy normalizer  1306  may generate the second extended signal  1350  based on the first extended signal  250 , as described with reference to  FIG. 19 . The energy normalizer  1306  may provide the second extended signal  1350  to the spectral flip and decimation module  408 . 
     The spectral flip and decimation module  408  may generate a spectrally flipped signal by performing spectral flipping of the second extended signal  1350  in the time-domain, as described with reference to  FIG. 4 . The spectral flip and decimation module  408  may generate a first signal  1750  (e.g., a HB excitation signal) by decimating the spectrally flipped signal based on a first all-pass filter and a second all-pass filter, as described with reference to  FIG. 4 . 
     The spectral flip and decimation module  408  may provide the first signal  1750  to the adaptive whitening module  410 . The adaptive whitening module  410  may generate a second signal  1752  (e.g., an HB excitation signal) by flattening a spectrum of the first signal  1750  by performing fourth-order LP whitening of the first signal  1750 , as described with reference to  FIG. 4 . The adaptive whitening module  410  may provide the second signal  452  to the temporal envelope modulator  412 , the HB excitation estimator  414 , or both. 
     The temporal envelope modulator  412  may receive the second signal  1752  from the adaptive whitening module  410 , a noise signal  1740  from a random noise generator, or both. The random noise generator may be coupled to or may be included in the first device  102 . The temporal envelope modulator  412  may generate a third signal  1754  based on the noise signal  1740 , the second signal  1752 , or both. For example, the temporal envelope modulator  412  may generate a first noise signal by applying temporal shaping to the noise signal  1740 . The temporal envelope modulator  412  may generate a signal envelope based on the second signal  1752  (or the first LB excitation signal  244 ). The temporal envelope modulator  412  may generate the first noise signal based on the signal envelope and the noise signal  1740 . For example, the temporal envelope modulator  412  may combine the signal envelope and the noise signal  1740 . Combining the signal envelope and the noise signal  1740  may modulate amplitude of the noise signal  1740 . The temporal envelope modulator  412  may generate the third signal  1754  by applying spectral shaping to the first noise signal. In an alternate implementation, the temporal envelope modulator  412  may generate the first noise signal by applying spectral shaping to the noise signal  1740  and may generate the third signal  1754  by applying temporal shaping to the first noise signal. Thus, spectral and temporal shaping may be applied in any order to the noise signal  1740 . The temporal envelope modulator  412  may provide the third signal  1754  to the HB excitation estimator  414 . 
     The HB excitation estimator  414  may receive the second signal  1752  from the adaptive whitening module  410 , the third signal  1754  from the temporal envelope modulator  412 , the harmonicity indicator  1364 , the mix factors  1353  from the configuration module  1305 , or a combination thereof. The HB excitation estimator  414  may generate the HB excitation signal  1352  by combining the second signal  1752  and the third signal  1754  based on the harmonicity indicator  1364 , the mix factors  1353 , or both. 
     The mix factors  1353  may indicate a HB VF, as described with reference to  FIG. 14 . For example, the mix factors  1353  may indicate a first weight (e.g., HB VF) and a second weight (e.g., 1−HB VF). The HB excitation estimator  414  may adjust the mix factors  1353  based on the harmonicity indicator  1364 , as described with reference to  FIG. 18 . The HB excitation estimator  414  may power normalize the third signal  1754  so that the third signal  1754  has the same power level as the second signal  1752 . 
     The HB excitation estimator  414  may generate the HB excitation signal  1352  by performing a weighted sum of the second signal  1752  and the third signal  1754  based on the adjusted mix factors  1353 , where the first weight is assigned to the second signal  1752  and the second weight is assigned to the third signal  1754 . For example, the HB excitation estimator  414  may generate sub-frame (i) of the HB excitation signal  1352  by mixing sub-frame (i) of the second signal  1752  that is scaled based on VF i  of Equation 7 (e.g., scaled based on a square root of VF i ) and sub-frame (i) of the third signal  1754  that is scaled based on (1−VF i ) of Equation 7 (e.g., scaled based on a square root of (1−VF i )). The HB excitation estimator  414  may provide the HB excitation signal  1352  to the bit-stream parameter generator  1348 . 
     The bit-stream parameter generator  1348  may generate the bit-stream parameters  160 . For example, the bit-stream parameters  160  may include the mix configuration mode  368 . The mix configuration mode  368  may correspond to the mix factors  1353  (e.g., the adjusted mix factors  1353 ). As another example, the bit-stream parameters  160  may include the NL configuration mode  158 , the filter information  374 , the HB LSF data  364 , or a combination thereof. The filter information  374  may include an index generated by the energy normalizer  1306 , as further described with reference to  FIG. 19 . The HB LSF data  364  may correspond to a quantized filter (e.g., quantized LSFs) generated by the energy normalizer  1306 , as further described with reference to  FIG. 19 . 
     The bit-stream parameter generator  1348  may generate target gain information (e.g., the HB target gain data  370 , the gain shape data  372 , or both) based on a comparison of the HB excitation signal  1352  and the first HB signal  242 . The bit-stream parameter generator  1348  may update the target gain information based on the harmonicity indicator  1364 , the peakiness indicator  1366 , or both. For example, the bit-stream parameter generator  1348  may reduce an HB gain frame indicated by the target gain information when the harmonicity indicator  1364  indicates a strong harmonic component, the peakiness indicator  1366  indicates a high peakiness, or both. To illustrate, the bit-stream parameter generator  1348  may, in response to determining that the peakiness indicator  1366  satisfies a first threshold and the harmonicity indicator  1364  satisfies a second threshold, reduce the HB gain frame indicated by the target gain information. 
     The bit-stream parameter generator  1348  may update the target gain information to modify a gain shape of a particular sub-frame when the peakiness indicator  1366  indicates spikes of energy in the first HB signal  242 . The peakiness indicator  1366  may include sub-frame peakiness values. For example, the peakiness indicator  1366  may indicate a peakiness value of the particular sub-frame. The sub-frame peakiness values may be “smoothed” to determine whether the first HB signal  242  corresponds to a harmonic HB, a non-harmonic HB, or a HB with one or more spikes. For example, the bit-stream parameter generator  1348  may perform smoothing by applying an approximating function (e.g., a moving average) to the peakiness indicator  1366 . Additionally, or alternatively, the bit-stream parameter generator  1348  may update the target gain information to modify (e.g., attenuate) a gain shape of the particular sub-frame. The bit-stream parameters  160  may include the target gain information. 
     Referring to  FIG. 18 , a diagram of an illustrative aspect of a method of high band signal generation is shown and generally designated  1800 . The method  1800  may be performed by one or more components of the systems  100 - 200 ,  1300 - 1400  of  FIGS. 1-2, 13-14 . For example, the method  1800  may be performed by the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the second encoder  296  of  FIG. 2 , the HB excitation signal generator  1347  of  FIG. 13 , the LB to HB pitch extension measure estimator  1404  of  FIG. 14 , or a combination thereof. 
     The method  1800  includes receiving a LB to HB pitch extension measure, at  1802 . For example, the HB excitation estimator  414  may receive the harmonicity indicator  1364  (e.g., a HB coherence value) from the configuration module  1305 , as described with reference to  FIGS. 13-14 and 17 . 
     The method  1800  also includes receiving estimated mix factors based on low band voicing information, at  1804 . For example, the HB excitation estimator  414  may receive the mix factors  1353  from the configuration module  1305 , as described with reference to  FIGS. 13-14 and 17 . The mix factors  1353  may be based on the LB VF  1354 , as described with reference to  FIG. 14 . 
     The method  1800  further includes adjusting estimated mix factors based on knowledge of HB coherence (e.g., the LB to HB pitch extension measure), at  1806 . For example, the HB excitation estimator  414  may adjust the mix factors  1353  based on the harmonicity indicator  1364 , as described with reference to  FIG. 17 . 
       FIG. 18  also includes a diagram of an illustrative aspect of a method of adjusting estimated mix factors that is generally designated  1820 . The method  1820  may correspond to the step  1806  of the method  1800 . 
     The method  1820  includes determining whether a LB VF is greater than a first threshold and HB coherence is less than a second threshold, at  1808 . For example, the HB excitation estimator  414  may determine whether the LB VF  1354  is greater than a first threshold and the harmonicity indicator  1364  is less than a second threshold. In a particular aspect, the mix factors  1353  may indicate the LB VF  1354 . 
     The method  1820  includes, in response to determining that the LB VF is greater than the first threshold and that the HB coherence is less than the second threshold, at  1808 , attenuating mix factors, at  1810 . For example, the HB excitation estimator  414  may attenuate the mix factors  1353  in response to determining that the LB VF  1354  is greater than the first threshold and that the harmonicity indicator  1364  fails to satisfy is less than the second threshold. 
     The method  1820  includes, in response to determining that the LB VF is less than or equal to the first threshold or that the HB coherence is greater than or equal to the second threshold, at  1808 , determining whether the LB VF is less than the first threshold and that the HB coherence is less than the second threshold, at  1812 . For example, the HB excitation estimator  414  may, in response to determining that the LB VF  1354  is less than or equal to the first threshold or that the harmonicity indicator  1364  is greater than or equal to the second threshold, determine whether the LB VF  1354  is less than the first threshold and that the harmonicity indicator  1364  is greater than the second threshold. 
     The method  1820  includes, in response to determining that the LB VF is less than the first threshold and that the HB coherence is less than the second threshold, at  1812 , boosting mix factors, at  1814 . For example, the HB excitation estimator  414  may, in response to determining that the LB VF  1354  is less than the first threshold and that the harmonicity indicator  1364  is greater than the second threshold, boost the mix factors  1353 . 
     The method  1820  includes, in response to determining that the LB VF is greater than or equal to the first threshold or that the HB coherence is greater than or equal to the second threshold, at  1812 , leaving mix factors unchanged, at  1816 . For example, the HB excitation estimator  414  may, in response to determining that the LB VF  1354  is greater than or equal to the first threshold or that the harmonicity indicator  1364  is less than or equal to the second threshold, leave the mix factors  1353  unchanged. To illustrate, the HB excitation estimator  414  may leave the mix factors  1353  unchanged in response to determining that the LB VF  1354  is equal to the first threshold, that the harmonicity indicator  1364  is equal to the second threshold, that the LB VF  1354  is less than the first threshold and the harmonicity indicator  1364  is less than the second threshold, or that the LB VF  1354  is greater than the first threshold and the harmonicity indicator  1364  is greater than the second threshold. 
     The HB excitation estimator  414  may adjust the mix factors  1353  based on the harmonicity indicator  1364 , the LB VF  1354 , or both. The mix factors  1353  may indicate the HB VF, as described with reference to  FIG. 14 . The HB excitation estimator  414  may reduce (or increase) variations in the HB VF based on the harmonicity indicator  1364 , the LB VF  1354 , or both. Modifying the HB VF based on the harmonicity indicator  1364  and the LB VF  1354  may compensate for a mismatch between the LB VF  1354  and the HB VF. 
     Lower frequencies of voiced speech signals may generally exhibit a stronger harmonic structure than higher frequencies. An output (e.g., the extended signal  150  of  FIG. 1 ) of non-linear modeling may sometimes over-emphasize harmonics in a high-band portion and may lead to unnatural buzzy-sounding artifacts. Attenuating the mix factors may produce a pleasant sounding high-band signal (e.g., the high-band signal  142  of  FIG. 1 ). 
     Referring to  FIG. 19 , a diagram of an illustrative aspect of the energy normalizer  1306  is depicted. The energy normalizer  1306  may include a filter estimator  1902 , a filter applicator  1912 , or both. 
     The filter estimator  1902  may include a filter adjuster  1908 , an adder  1914 , or both. The second encoder  296  (e.g., the filter estimator  1902 ) may generate a particular HB excitation signal (e.g., an HB residual) associated with the first HB signal  242 . The filter estimator  1902  may select (or generate) a filter  1906  based on a comparison of the first extended signal  250  and the first HB signal  242  (or the particular HB excitation signal). For example, the filter estimator  1902  may select (or generate) the filter  1906  to reduce (e.g., eliminate) distortion between the first extended signal  250  and the first HB signal  242  (or the particular HB excitation signal), as described herein. The filter adjuster  1908  may generate a scaled signal  1916  by applying the filter  1906  (e.g., a FIR filter) to the first extended signal  250 . The filter adjuster  1908  may provide the scaled signal  1916  to the adder  1914 . The adder  1914  may generate an error signal  1904  corresponding to a distortion (e.g., a difference) between the scaled signal  1916  and the first HB signal  242  (or the particular HB excitation signal). For example, the error signal  1904  may correspond to a mean-squared error between the scaled signal  1916  and the first HB signal  242  (or the particular HB excitation signal). The adder  1914  may generate the error signal  1904  based on a least mean squares (LMS) algorithm. The adder  1914  may provide the error signal  1904  to the filter adjuster  1908 . 
     The filter adjuster  1908  may select (e.g., adjust) the filter  1906  based on the error signal  1904 . For example, the filter adjuster  1908  may iteratively adjust the filter  1906  to reduce a distortion metric (e.g., a mean-squared error metric) between a first harmonic component of the scaled signal  1916  and a second harmonic component of the first HB signal  242  (or the particular HB excitation signal) by reducing (or eliminating) an energy of the error signal  1904 . The filter adjuster  1908  may generate the scaled signal  1916  by applying the adjusted filter  1906  to the first extended signal  250 . The filter estimator  1902  may provide the filter  1906  (e.g., the adjusted filter  1906 ) to the filter applicator  1912 . 
     The filter applicator  1912  may include a quantizer  1918 , a FIR filter engine  1924 , or both. The quantizer  1918  may generate a quantized filter  1922  based on the filter  1906 . For example, the quantizer  1918  may generate filter coefficients (e.g., LSP coefficients, or LPCs) corresponding to the filter  1906 . The quantizer  1918  may generate quantized filter coefficients by performing a multi-stage (e.g., 2-stage) vector quantization (VQ) on the filter coefficients. The quantized filter  1922  may include the quantized filter coefficients. The quantizer  1918  may provide a quantization index  1920  corresponding to the quantized filter  1922  to the bit-stream parameter generator  1348  of  FIG. 13 . The bit-stream parameters  160  may include the filter information  374  indicating the quantization index  1920 , the HB LSF data  364  corresponding to the quantized filter  1922  (e.g., the quantized LSP coefficients or the quantized LPCs), or both. 
     The quantizer  1918  may provide the quantized filter  1922  to the FIR filter engine  1924 . The FIR filter engine  1924  may generate the second extended signal  1350  by filtering the first extended signal  250  based on the quantized filter  1922 . The FIR filter engine  1924  may provide the second extended signal  1350  to the HB excitation signal generator  1347  of  FIG. 13 . 
     Referring to  FIG. 20 , a diagram of an aspect of a method of high band signal generation is shown and generally designated  2000 . The method  2000  may be performed by one or more components of the systems  100 ,  200 , or  1300  of  FIG. 1, 2 or 13 . For example, the method  2000  may be performed by the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the second encoder  296  of  FIG. 2 , the energy normalizer  1306  of  FIG. 13 , the filter estimator  1902 , the filter applicator  1912  of  FIG. 19 , or a combination thereof. 
     The method  2000  includes receiving a high band signal and a first extended signal, at  2002 . For example, the energy normalizer  1306  of  FIG. 13  may receive the first HB signal  242  and the first extended signal  250 , as described with reference to  FIG. 13 . 
     The method  2000  also includes estimating a filter (h(n)) which minimizes (or reduces) energy of error, at  2004 . For example, the filter estimator  1902  of  FIG. 19  may estimate the filter  1906  to reduce an energy of the error signal  1904 , as described with reference to  FIG. 19 . 
     The method  2000  further includes quantizing and transmitting an index corresponding to h(n), at  2006 . For example, the quantizer  1918  may generate the quantized filter  1922  by quantizing the filter  1906 , as described with reference to  FIG. 19 . The quantizer  1918  may generate the quantization index  1920  corresponding to the filter  1906 , as described with reference to  FIG. 19 . 
     The method  2000  also includes using the quantized filter and filtering the first extended signal to generate a second extended signal, at  2008 . For example, the FIR filter engine  1924  may generate the second extended signal  1350  by filtering the first extended signal  250  based on the quantized filter  1922 . 
     Referring to  FIG. 21 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  2100 . The method  2100  may be performed by one or more components of the systems  100 ,  200 , or  1300  of  FIG. 1, 2 or 13 . For example, the method  2100  may be performed by the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the first encoder  204 , the second encoder  296  of  FIG. 2 , the bit-stream parameter generator  1348 , the transmitter  1392  of  FIG. 13 , or a combination thereof. 
     The method  2100  includes receiving an audio signal at a first device, at  2102 . For example, the encoder  108  of the second device  104  may receive the input signal  114 , as described with reference to  FIG. 13 . 
     The method  2100  also includes generating, at the first device, a signal modeling parameter based on a harmonicity indicator, a peakiness indicator, or both, the signal modeling parameter associated with a high-band portion of the audio signal, at  2104 . For example, the encoder  108  of the second device  104  may generate the NL configuration mode  158 , the mix configuration mode  368 , target gain information (e.g., the HB target gain data  370 , the gain shape data  372 , or both), or a combination thereof, as described with reference to  FIGS. 13, 14, 16, and 17 . To illustrate, the configuration mode generator  1406  may generate the NL configuration mode  158 , as described with reference to  FIGS. 14 and 16 . The HB excitation estimator  414  may generate the mix configuration mode  368  based on the mix factors  1353 , the harmonicity indicator  1364 , or both, as described with reference to  FIG. 17 . The bit-stream parameter generator  1348  may generate the target gain information, as described with reference to  FIG. 17 . 
     The method  2100  further includes sending, from the first device to a second device, the signal modeling parameter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal, at  2106 . For example, the transmitter  1392  of  FIG. 13  may transmit, from the second device  104  to the first device  102 , the NL configuration mode  158 , the mix configuration mode  368 , the HB target gain data  370 , the gain shape data  372 , or a combination thereof, in conjunction with the audio data  126 . 
     Referring to  FIG. 22 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  2200 . The method  2200  may be performed by one or more components of the systems  100 ,  200 , or  1300  of  FIG. 1, 2 or 13 . For example, the method  2200  may be performed by the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the first encoder  204 , the second encoder  296  of  FIG. 2 , the bit-stream parameter generator  1348 , the transmitter  1392  of  FIG. 13 , or a combination thereof. 
     The method  2200  includes receiving an audio signal at a first device, at  2202 . For example, the encoder  108  of the second device  104  may receive the input signal  114  (e.g., an audio signal), as described with reference to  FIG. 13 . 
     The method  2200  also includes generating, at the first device, a high-band excitation signal based on a high-band portion of the audio signal, at  2204 . For example, the resampler and filterbank  202  of the second device  104  may generate the first HB signal  242  based on a high-band portion of the input signal  114 , as described with reference to  FIG. 13 . The second encoder  296  may generate a particular HB excitation signal (e.g., an HB residual) based on the first HB signal  242 . 
     The method  2200  further includes generating, at the first device, a modeled high-band excitation signal based on a low-band portion of the audio signal, at  2206 . For example, the encoder bandwidth extension module  206  of the second device  104  may generate the first extended signal  250  based on the first LB signal  240 , as described with reference to  FIG. 13 . The first LB signal  240  may correspond to a low-band portion of the input signal  114 . 
     The method  2200  also includes selecting, at the first device, a filter based on a comparison of the modeled high-band excitation signal and the high-band excitation signal, at  2208 . For example, the filter estimator  1902  of the second device  104  may select the filter  1906  based on a comparison of the first extended signal  250  and the first HB signal  242  (or the particular HB excitation signal), as described with reference to  FIG. 19 . 
     The method  2200  further includes sending, from the first device to a second device, filter information corresponding to the filter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal, at  2210 . For example, the transmitter  1392  may transmit, from the second device  104  to the first device  102 , the filter information  374 , the HB LSF data  364 , or both, in conjunction with the audio data  126  corresponding to the input signal  114 , as described with reference to  FIGS. 13 and 19 . 
     Referring to  FIG. 23 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  2300 . The method  2300  may be performed by one or more components of the systems  100 ,  200 , or  1300  of  FIG. 1, 2 or 13 . For example, the method  2300  may be performed by the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the first encoder  204 , the second encoder  296  of  FIG. 2 , the bit-stream parameter generator  1348 , the transmitter  1392  of  FIG. 13 , or a combination thereof. 
     The method  2300  includes receiving an audio signal at a first device, at  2302 . For example, the encoder  108  of the second device  104  may receive the input signal  114  (e.g., an audio signal), as described with reference to  FIG. 13 . 
     The method  2300  also includes generating, at the first device, a high-band excitation signal based on a high-band portion of the audio signal, at  2304 . For example, the resampler and filterbank  202  of the second device  104  may generate the first HB signal  242  based on a high-band portion of the input signal  114 , as described with reference to  FIG. 13 . The second encoder  296  may generate a particular HB excitation signal (e.g., an HB residual) based on the first HB signal  242 . 
     The method  2300  further includes generating, at the first device, a modeled high-band excitation signal based on a low-band portion of the audio signal, at  2306 . For example, the encoder bandwidth extension module  206  of the second device  104  may generate the first extended signal  250  based on the first LB signal  240 , as described with reference to  FIG. 13 . The first LB signal  240  may correspond to a low-band portion of the input signal  114 . 
     The method  2300  also includes generating, at the first device, filter coefficients based on a comparison of the modeled high-band excitation signal and the high-band excitation signal, at  2308 . For example, the filter estimator  1902  of the second device  104  may generate filter coefficients corresponding to the filter  1906  based on a comparison of the first extended signal  250  and the first HB signal  242  (or the particular HB excitation signal), as described with reference to  FIG. 19 . 
     The method  2300  further includes generating, at the first device, filter information by quantizing the filter coefficients, at  2310 . For example, the quantizer  1918  of the second device  104  may generate the quantization index  1920  and the quantized filter  1922  (e.g., quantized filter coefficients) by quantizing the filter coefficients corresponding to the filter  1906 , as described with reference to  FIG. 19 . The quantizer  1918  may generate the filter information  374  indicating the quantization index  1920 , the HB LSF data  364  indicating the quantized filter coefficients, or both. 
     The method  2300  also includes sending, from the first device to a second device, the filter information in conjunction with a bandwidth-extended audio stream corresponding to the audio signal, at  2210 . For example, the transmitter  1392  may transmit, from the second device  104  to the first device  102 , the filter information  374 , the HB LSF data  364 , or both, in conjunction with the audio data  126  corresponding to the input signal  114 , as described with reference to  FIGS. 13 and 19 . 
     Referring to  FIG. 24 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  2400 . The method  2400  may be performed by one or more components of the systems  100 ,  200 , or  1300  of  FIG. 1, 2 or 13 . For example, the method  2400  may be performed by the first device  102 , the processor  106 , the encoder  108 , the second device  104 , the processor  116 , the decoder  118 , the second decoder  136 , the decoding module  162 , the HB excitation signal generator  147  of  FIG. 1 , the second encoder  296 , the encoding module  208 , the encoder bandwidth extension module  206  of  FIG. 2 , the system  400 , the harmonic extension module  404  of  FIG. 4 , or a combination thereof. 
     The method  2400  includes selecting, at a device, a plurality of non-linear processing functions based at least in part on a value of a parameter, at  2402 . For example, the harmonic extension module  404  may select the first function  164  and the second function  166  of  FIG. 1  based at least in part on a value of the NL configuration mode  158 , as described with reference to  FIGS. 4 and 17 . 
     The method  2400  also includes generating, at the device, a high-band excitation signal based on the plurality of non-linear processing functions, at  2404 . For example, the harmonic extension module  404  may generate the extended signal  150  based on the first function  164  and the second function  166 , as described with reference to  FIG. 4 . As another example, the harmonic extension module  404  may generate the first extended signal  250  based on the first function  164  and the second function  166 , as described with reference to  FIG. 17 . 
     The method  2400  may thus enable selection of a plurality of non-linear functions based on a value of a parameter. A high-band excitation signal may be generated, at an encoder, a decoder, or both, based on the plurality of non-linear functions. 
     Referring to  FIG. 25 , a flowchart of an aspect of a method of high band signal generation is shown and generally designated  2500 . The method  2500  may be performed by one or more components of the systems  100 ,  200 , or  1300  of  FIG. 1, 2 or 13 . For example, the method  2500  may be performed by the second device  104 , the receiver  192 , the HB excitation signal generator  147 , the decoding module  162 , the second decoder  136 , the decoder  118 , the processor  116  of  FIG. 1 , or a combination thereof. 
     The method  2500  includes receiving, at a device, a parameter associated with a bandwidth-extended audio stream, at  2502 . For example, the receiver  192  may receive the HR configuration mode  366  associated with the audio data  126 , as described with reference to  FIGS. 1 and 3 . 
     The method  2500  also includes determining, at the device, a value of the parameter, at  2504 . For example, the synthesis module  418  may determine a value of the HR configuration mode  366 , as described with reference to  FIG. 4 . 
     The method  2500  further includes selecting, based on the value of the parameter, one of target gain information associated with the bandwidth-extended audio stream or filter information associated with the bandwidth-extended audio stream, at  2506 . For example, when the value of the HR configuration mode  366  is 1, the synthesis module  418  may select target gain information, such as one or more of the gain shape data  372 , the HB target gain data  370 , or the gain information  362 , as described with reference to  FIG. 4 . When the value of the HR configuration mode  366  is 0, the synthesis module  418  may select the filter information  374 , as described with reference to  FIG. 4 . 
     The method  2500  also includes generating, at the device, a high-band excitation signal based on the one of the target gain information or the filter information, at  2508 . For example, the synthesis module  418  may generate a modified excitation signal based on the selected one of the target gain information or the filter information  374 , as described with reference to  FIG. 4 . 
     The method  2500  may thus enable selection of target gain information or filter information based on a value of a parameter. A high-band excitation signal may be generated, at a decoder, based on the selected one of the target gain information or the filter information. 
     Referring to  FIG. 26 , a block diagram of a particular illustrative aspect of a device (e.g., a wireless communication device) is depicted and generally designated  2600 . In various aspects, the device  2600  may have fewer or more components than illustrated in  FIG. 26 . In an illustrative aspect, the device  2600  may correspond to the first device  102  or the second device  104  of  FIG. 1 . In an illustrative aspect, the device  2600  may perform one or more operations described with reference to systems and methods of  FIGS. 1-25 . 
     In a particular aspect, the device  2600  includes a processor  2606  (e.g., a central processing unit (CPU)). The device  2600  may include one or more additional processors  2610  (e.g., one or more digital signal processors (DSPs)). The processors  2610  may include a media (e.g., speech and music) coder-decoder (CODEC)  2608 , and an echo canceller  2612 . The media CODEC  2608  may include the decoder  118 , the encoder  108 , or both. The decoder  118  may include the first decoder  134 , the second decoder  136 , the signal generator  138 , or a combination thereof. The second decoder  136  may include the TBE frame converter  156 , the bandwidth extension module  146 , the decoding module  162 , or a combination thereof. The decoding module  162  may include the HB excitation signal generator  147 , the HB signal generator  148 , or both. The encoder  108  may include the first encoder  204 , the second encoder  296 , the resampler and filterbank  202 , or a combination thereof. The second encoder  296  may include the energy normalizer  1306 , the encoding module  208 , the encoder bandwidth extension module  206 , the configuration module  1305 , or a combination thereof. The encoding module  208  may include the HB excitation signal generator  1347 , the bit-stream parameter generator  1348 , or both. 
     Although the media CODEC  2608  is illustrated as a component of the processors  2610  (e.g., dedicated circuitry and/or executable programming code), in other aspects one or more components of the media CODEC  2608 , such as the decoder  118 , the encoder  108 , or both, may be included in the processor  2606 , the CODEC  2634 , another processing component, or a combination thereof. 
     The device  2600  may include a memory  2632  and a CODEC  2634 . The memory  2632  may correspond to the memory  132  of  FIG. 1 , the memory  1332  of  FIG. 13 , or both. The device  2600  may include a transceiver  2650  coupled to an antenna  2642 . The transceiver  2650  may include the receiver  192  of  FIG. 1 , the transmitter  1392  of  FIG. 13 , or both. The device  2600  may include a display  2628  coupled to a display controller  2626 . One or more speakers  2636 , one or more microphones  2638 , or a combination thereof, may be coupled to the CODEC  2634 . In a particular aspect, the speakers  2636  may correspond to the speakers  122  of  FIG. 1 . The microphones  2638  may correspond to the microphones  1338  of  FIG. 13 . The CODEC  2634  may include a digital-to-analog converter (DAC)  2602  and an analog-to-digital converter (ADC)  2604 . 
     The memory  2632  may include instructions  2660  executable by the processor  2606 , the processors  2610 , the CODEC  2634 , another processing unit of the device  2600 , or a combination thereof, to perform one or more operations described with reference to  FIGS. 1-25 . 
     One or more components of the device  2600  may be implemented via dedicated hardware (e.g., circuitry), by a processor executing instructions to perform one or more tasks, or a combination thereof. As an example, the memory  2632  or one or more components of the processor  2606 , the processors  2610 , and/or the CODEC  2634  may be a memory device, such as a random access memory (RAM), magnetoresistive random access memory (MRAM), spin-torque transfer MRAM (STT-MRAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disk, a removable disk, or a compact disc read-only memory (CD-ROM). The memory device may include instructions (e.g., the instructions  2660 ) that, when executed by a computer (e.g., a processor in the CODEC  2634 , the processor  2606 , and/or the processors  2610 ), may cause the computer to perform one or more operations described with reference to  FIGS. 1-25 . As an example, the memory  2632  or the one or more components of the processor  2606 , the processors  2610 , the CODEC  2634  may be a non-transitory computer-readable medium that includes instructions (e.g., the instructions  2660 ) that, when executed by a computer (e.g., a processor in the CODEC  2634 , the processor  2606 , and/or the processors  2610 ), cause the computer perform one or more operations described with reference to  FIGS. 1-25 . 
     In a particular aspect, the device  2600  may be included in a system-in-package or system-on-chip device (e.g., a mobile station modem (MSM))  2622 . In a particular aspect, the processor  2606 , the processors  2610 , the display controller  2626 , the memory  2632 , the CODEC  2634 , and the transceiver  2650  are included in a system-in-package or the system-on-chip device  2622 . In a particular aspect, an input device  2630 , such as a touchscreen and/or keypad, and a power supply  2644  are coupled to the system-on-chip device  2622 . Moreover, in a particular aspect, as illustrated in  FIG. 26 , the display  2628 , the input device  2630 , the speakers  2636 , the microphones  2638 , the antenna  2642 , and the power supply  2644  are external to the system-on-chip device  2622 . However, each of the display  2628 , the input device  2630 , the speakers  2636 , the microphones  2638 , the antenna  2642 , and the power supply  2644  can be coupled to a component of the system-on-chip device  2622 , such as an interface or a controller. 
     The device  2600  may include a wireless telephone a mobile communication device, a smart phone, a cellular phone, a laptop computer, a desktop computer, a computer, a tablet computer, a set top box, a personal digital assistant, a display device, a television, a gaming console, a music player, a radio, a video player, an entertainment unit, a communication device, a fixed location data unit, a personal media player, a digital video player, a digital video disc (DVD) player, a tuner, a camera, a navigation device, a decoder system, an encoder system, a media playback device, a media broadcast device, or any combination thereof. 
     In a particular aspect, one or more components of the systems described with reference to  FIGS. 1-25  and the device  2600  may be integrated into a decoding system or apparatus (e.g., an electronic device, a CODEC, or a processor therein), into an encoding system or apparatus, or both. In other aspects, one or more components of the systems described with reference to  FIGS. 1-25  and the device  2600  may be integrated into a wireless telephone, a tablet computer, a desktop computer, a laptop computer, a set top box, a music player, a video player, an entertainment unit, a television, a game console, a navigation device, a communications device, a personal digital assistant (PDA), a fixed location data unit, a personal media player, or another type of device. 
     It should be noted that various functions performed by the one or more components of the systems described with reference to  FIGS. 1-25  and the device  2600  are described as being performed by certain components or modules. This division of components and modules is for illustration only. In an alternate aspect, a function performed by a particular component or module may be divided amongst multiple components or modules. Moreover, in an alternate aspect, two or more components or modules described with reference to  FIGS. 1-26  may be integrated into a single component or module. Each component or module illustrated in  FIGS. 1-26  may be implemented using hardware (e.g., a field-programmable gate array (FPGA) device, an application-specific integrated circuit (ASIC), a DSP, a controller, etc.), software (e.g., instructions executable by a processor), or any combination thereof. 
     In conjunction with the described aspects, an apparatus is disclosed that includes means for storing a parameter associated with a bandwidth-extended audio stream. For example, the means for storing may include the second device  104 , memory  132  of  FIG. 1 , the media storage  292  of  FIG. 2 , the memory  2632  of  FIG. 25 , one or more devices configured to store a parameter, or a combination thereof. 
     The apparatus also includes means for generating a high-band excitation signal based on a plurality of non-linear processing functions. For example, the means for generating may include the first device  102 , the processor  106 , the encoder  108 , the second device  104 , the processor  116 , the decoder  118 , the second decoder  136 , the decoding module  162  of  FIG. 1 , the second encoder  296 , the encoding module  208 , the encoder bandwidth extension module  206  of  FIG. 2 , the system  400 , the harmonic extension module  404  of  FIG. 4 , the processors  2610 , the media codec  2608 , the device  2600  of  FIG. 25 , one or more devices configured to generate a high-band excitation signal based on a plurality of non-linear processing functions (e.g., a processor executing instructions stored at a computer-readable storage device), or a combination thereof. The plurality of non-linear processing functions may be selected based at least in part on a value of the parameter. 
     Also, in conjunction with the described aspects, an apparatus is disclosed that includes means for receiving a parameter associated with a bandwidth-extended audio stream. For example, the means for receiving may include the receiver  192  of  FIG. 1 , the transceiver  2695  of  FIG. 25 , one or more devices configured to receive a parameter associated with a bandwidth-extended audio stream, or a combination thereof. 
     The apparatus also includes means for generating a high-band excitation signal based on one of target gain information associated with the bandwidth-extended audio stream or filter information associated with the bandwidth-extended audio stream. For example, the means for generating may include the HB excitation signal generator  147 , the decoding module  162 , the second decoder  136 , the decoder  118 , the processor  116 , the second device  104  of  FIG. 1 , the synthesis module  418  of  FIG. 4 , the processors  2610 , the media codec  2608 , the device  2600  of  FIG. 25 , one or more devices configured to generate a high-band excitation signal, or a combination thereof. The one of the target gain information or the filter information may be selected based on a value of the parameter. 
     Further, in conjunction with the described aspects, an apparatus is disclosed that includes means for generating a signal modeling parameter based on a harmonicity indicator, a peakiness indicator, or both. For example, the means for generating may include the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the second encoder  296 , the encoding module  208  of  FIG. 2 , the configuration module  1305 , the energy normalizer  1306 , the bit-stream parameter generator  1348  of  FIG. 13 , one or more devices configured to generate a signal modeling parameter based on the harmonicity indicator, the peakiness indicator, or both (e.g., a processor executing instructions stored at a computer-readable storage device), or a combination thereof. The signal modeling parameter may be associated with a high-band portion of an audio signal. 
     The apparatus also includes means for transmitting the signal modeling parameter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. For example, the means for transmitting may include the transmitter  1392  of  FIG. 13 , the transceiver  2695  of  FIG. 25 , one or more devices configured to transmit the signal modeling parameter, or a combination thereof. 
     Also, in conjunction with the described aspects, an apparatus is disclosed that includes means for selecting a filter based on a comparison of a modeled high-band excitation signal and a high-band excitation signal. For example, the means for selecting may include the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the second encoder  296 , the encoding module  208  of  FIG. 2 , the energy normalizer  1306  of  FIG. 13 , the filter estimator  1902  of  FIG. 19 , one or more devices configured to select the filter (e.g., a processor executing instructions stored at a computer-readable storage device), or a combination thereof. The high-band excitation signal may be based on a high-band portion of an audio signal. The modeled high-band excitation signal may be based on a low-band portion of the audio signal. 
     The apparatus also includes means for transmitting filter information corresponding to the filter in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. For example, the means for transmitting may include the transmitter  1392  of  FIG. 13 , the transceiver  2695  of  FIG. 25 , one or more devices configured to transmit the signal modeling parameter, or a combination thereof. 
     Further, in conjunction with the described aspects, an apparatus includes means for quantizing filter coefficients that are generated based on a comparison of a modeled high-band excitation signal and a high-band excitation signal. For example, the means for quantizing filter coefficients may include the first device  102 , the processor  106 , the encoder  108  of  FIG. 1 , the second encoder  296 , the encoding module  208  of  FIG. 2 , the energy normalizer  1306  of  FIG. 13 , the filter applicator  1912 , the quantizer  1918  of  FIG. 19 , one or more devices configured to quantize filter coefficients (e.g., a processor executing instructions stored at a computer-readable storage device), or a combination thereof. The high-band excitation signal may be based on a high-band portion of an audio signal. The modeled high-band excitation signal may be based on a low-band portion of the audio signal. 
     The apparatus also includes means for transmitting filter information in conjunction with a bandwidth-extended audio stream corresponding to the audio signal. For example, the means for transmitting may include the transmitter  1392  of  FIG. 13 , the transceiver  2695  of  FIG. 25 , one or more devices configured to transmit the signal modeling parameter, or a combination thereof. The filter information may be based on the quantized filter coefficients. 
     Referring to  FIG. 27 , a block diagram of a particular illustrative example of a base station  2700  is depicted. In various implementations, the base station  2700  may have more components or fewer components than illustrated in  FIG. 27 . In an illustrative example, the base station  2700  may include the first device  102 , the second device  104  of  FIG. 1 , or both. In an illustrative example, the base station  2700  may perform one or more operations described with reference to  FIGS. 1-26 . 
     The base station  2700  may be part of a wireless communication system. The wireless communication system may include multiple base stations and multiple wireless devices. The wireless communication system may be a Long Term Evolution (LTE) system, a Code Division Multiple Access (CDMA) system, a Global System for Mobile Communications (GSM) system, a wireless local area network (WLAN) system, or some other wireless system. A CDMA system may implement Wideband CDMA (WCDMA), CDMA 1×, Evolution-Data Optimized (EVDO), Time Division Synchronous CDMA (TD-SCDMA), or some other version of CDMA. 
     The wireless devices may also be referred to as user equipment (UE), a mobile station, a terminal, an access terminal, a subscriber unit, a station, etc. The wireless devices may include a cellular phone, a smartphone, a tablet, a wireless modem, a personal digital assistant (PDA), a handheld device, a laptop computer, a smartbook, a netbook, a tablet, a cordless phone, a wireless local loop (WLL) station, a Bluetooth device, etc. The wireless devices may include or correspond to the device  2600  of  FIG. 26 . 
     Various functions may be performed by one or more components of the base station  2700  (and/or in other components not shown), such as sending and receiving messages and data (e.g., audio data). In a particular example, the base station  2700  includes a processor  2706  (e.g., a CPU). The processor  2706  may correspond to the processor  106 , the processor  116  of  FIG. 1 , or both. The base station  2700  may include a transcoder  2710 . The transcoder  2710  may include an audio CODEC  2708 . For example, the transcoder  2710  may include one or more components (e.g., circuitry) configured to perform operations of the audio CODEC  2708 . As another example, the transcoder  2710  may be configured to execute one or more computer-readable instructions to perform the operations of the audio CODEC  2708 . Although the audio CODEC  2708  is illustrated as a component of the transcoder  2710 , in other examples one or more components of the audio CODEC  2708  may be included in the processor  2706 , another processing component, or a combination thereof. For example, a vocoder decoder  2738  may be included in a receiver data processor  2764 . As another example, a vocoder encoder  2736  may be included in a transmission data processor  2766 . 
     The transcoder  2710  may function to transcode messages and data between two or more networks. The transcoder  2710  may be configured to convert message and audio data from a first format (e.g., a digital format) to a second format. To illustrate, the vocoder decoder  2738  may decode encoded signals having a first format and the vocoder encoder  2736  may encode the decoded signals into encoded signals having a second format. Additionally or alternatively, the transcoder  2710  may be configured to perform data rate adaptation. For example, the transcoder  2710  may downconvert a data rate or upconvert the data rate without changing a format the audio data. To illustrate, the transcoder  2710  may downconvert 64 kbit/s signals into 16 kbit/s signals. 
     The audio CODEC  2708  may include the vocoder encoder  2736  and the vocoder decoder  2738 . The vocoder encoder  2736  may include an encoder selector, a speech encoder, and a non-speech encoder. The vocoder encoder  2736  may include the encoder  108 . The vocoder decoder  2738  may include a decoder selector, a speech decoder, and a non-speech decoder. The vocoder decoder  2738  may include the decoder  118 . 
     The base station  2700  may include a memory  2732 . The memory  2732 , such as a computer-readable storage device, may include instructions. The instructions may include one or more instructions that are executable by the processor  2706 , the transcoder  2710 , or a combination thereof, to perform one or more operations described with reference to  FIGS. 1-26 . The base station  2700  may include multiple transmitters and receivers (e.g., transceivers), such as a first transceiver  2752  and a second transceiver  2754 , coupled to an array of antennas. The array of antennas may include a first antenna  2742  and a second antenna  2744 . The array of antennas may be configured to wirelessly communicate with one or more wireless devices, such as the device  2600  of  FIG. 26 . For example, the second antenna  2744  may receive a data stream  2714  (e.g., a bit stream) from a wireless device. The data stream  2714  may include messages, data (e.g., encoded speech data), or a combination thereof. 
     The base station  2700  may include a network connection  2760 , such as backhaul connection. The network connection  2760  may be configured to communicate with a core network or one or more base stations of the wireless communication network. For example, the base station  2700  may receive a second data stream (e.g., messages or audio data) from a core network via the network connection  2760 . The base station  2700  may process the second data stream to generate messages or audio data and provide the messages or the audio data to one or more wireless device via one or more antennas of the array of antennas or to another base station via the network connection  2760 . In a particular implementation, the network connection  2760  may be a wide area network (WAN) connection, as an illustrative, non-limiting example. 
     The base station  2700  may include a demodulator  2762  that is coupled to the transceivers  2752 ,  2754 , the receiver data processor  2764 , and the processor  2706 , and the receiver data processor  2764  may be coupled to the processor  2706 . The demodulator  2762  may be configured to demodulate modulated signals received from the transceivers  2752 ,  2754  and to provide demodulated data to the receiver data processor  2764 . The receiver data processor  2764  may be configured to extract a message or audio data from the demodulated data and send the message or the audio data to the processor  2706 . 
     The base station  2700  may include a transmission data processor  2766  and a transmission multiple input-multiple output (MIMO) processor  2768 . The transmission data processor  2766  may be coupled to the processor  2706  and the transmission MIMO processor  2768 . The transmission MIMO processor  2768  may be coupled to the transceivers  2752 ,  2754  and the processor  2706 . The transmission data processor  2766  may be configured to receive the messages or the audio data from the processor  2706  and to code the messages or the audio data based on a coding scheme, such as CDMA or orthogonal frequency-division multiplexing (OFDM), as an illustrative, non-limiting examples. The transmission data processor  2766  may provide the coded data to the transmission MIMO processor  2768 . 
     The coded data may be multiplexed with other data, such as pilot data, using CDMA or OFDM techniques to generate multiplexed data. The multiplexed data may then be modulated (i.e., symbol mapped) by the transmission data processor  2766  based on a particular modulation scheme (e.g., Binary phase-shift keying (“BPSK”), Quadrature phase-shift keying (“QSPK”), M-ary phase-shift keying (“M-PSK”), M-ary Quadrature amplitude modulation (“M-QAM”), etc.) to generate modulation symbols. In a particular implementation, the coded data and other data may be modulated using different modulation schemes. The data rate, coding, and modulation for each data stream may be determined by instructions executed by processor  2706 . 
     The transmission MIMO processor  2768  may be configured to receive the modulation symbols from the transmission data processor  2766  and may further process the modulation symbols and may perform beamforming on the data. For example, the transmission MIMO processor  2768  may apply beamforming weights to the modulation symbols. The beamforming weights may correspond to one or more antennas of the array of antennas from which the modulation symbols are transmitted. 
     During operation, the second antenna  2744  of the base station  2700  may receive a data stream  2714 . The second transceiver  2754  may receive the data stream  2714  from the second antenna  2744  and may provide the data stream  2714  to the demodulator  2762 . The demodulator  2762  may demodulate modulated signals of the data stream  2714  and provide demodulated data to the receiver data processor  2764 . The receiver data processor  2764  may extract audio data from the demodulated data and provide the extracted audio data to the processor  2706 . In a particular aspect, the data stream  2714  may correspond to the audio data  126 . 
     The processor  2706  may provide the audio data to the transcoder  2710  for transcoding. The vocoder decoder  2738  of the transcoder  2710  may decode the audio data from a first format into decoded audio data and the vocoder encoder  2736  may encode the decoded audio data into a second format. In some implementations, the vocoder encoder  2736  may encode the audio data using a higher data rate (e.g., upconvert) or a lower data rate (e.g., downconvert) than received from the wireless device. In other implementations the audio data may not be transcoded. Although transcoding (e.g., decoding and encoding) is illustrated as being performed by a transcoder  2710 , the transcoding operations (e.g., decoding and encoding) may be performed by multiple components of the base station  2700 . For example, decoding may be performed by the receiver data processor  2764  and encoding may be performed by the transmission data processor  2766 . 
     The vocoder decoder  2738  and the vocoder encoder  2736  may select a corresponding decoder (e.g., a speech decoder or a non-speech decoder) and a corresponding encoder to transcode (e.g., decode and encode) the frame. Encoded audio data generated at the vocoder encoder  2736 , such as transcoded data, may be provided to the transmission data processor  2766  or the network connection  2760  via the processor  2706 . 
     The transcoded audio data from the transcoder  2710  may be provided to the transmission data processor  2766  for coding according to a modulation scheme, such as OFDM, to generate the modulation symbols. The transmission data processor  2766  may provide the modulation symbols to the transmission MIMO processor  2768  for further processing and beamforming. The transmission MIMO processor  2768  may apply beamforming weights and may provide the modulation symbols to one or more antennas of the array of antennas, such as the first antenna  2742  via the first transceiver  2752 . Thus, the base station  2700  may provide a transcoded data stream  2716 , that corresponds to the data stream  2714  received from the wireless device, to another wireless device. The transcoded data stream  2716  may have a different encoding format, data rate, or both, than the data stream  2714 . In other implementations, the transcoded data stream  2716  may be provided to the network connection  2760  for transmission to another base station or a core network. 
     The base station  2700  may therefore include a computer-readable storage device (e.g., the memory  2732 ) storing instructions that, when executed by a processor (e.g., the processor  2706  or the transcoder  2710 ), cause the processor to perform operations including selecting a plurality of non-linear processing functions based at least in part on a value of a parameter. The parameter is associated with a bandwidth-extended audio stream. The operations also include generating a high-band excitation signal based on the plurality of non-linear processing functions. 
     In a particular aspect, the base station  2700  may include a computer-readable storage device (e.g., the memory  2732 ) storing instructions that, when executed by a processor (e.g., the processor  2706  or the transcoder  2710 ), cause the processor to perform operations including receiving a parameter associated with a bandwidth-extended audio stream. The operations also include determining a value of the parameter. The operations further include selecting, based on the value of the parameter, one of target gain information associated with the bandwidth-extended audio stream or filter information associated with the bandwidth-extended audio stream. The operations also include generating a high-band excitation signal based on the one of the target gain information or the filter information. 
     Those of skill would further appreciate that the various illustrative logical blocks, configurations, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software executed by a processing device such as a hardware processor, or combinations of both. Various illustrative components, blocks, configurations, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or executable software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. 
     The steps of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in a memory device, such as random access memory (RAM), magnetoresistive random access memory (MRAM), spin-torque transfer MRAM (STT-MRAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disk, a removable disk, or a compact disc read-only memory (CD-ROM). An exemplary memory device is coupled to the processor such that the processor can read information from, and write information to, the memory device. In the alternative, the memory device may be integral to the processor. The processor and the storage medium may reside in an application-specific integrated circuit (ASIC). The ASIC may reside in a computing device or a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a computing device or a user terminal. 
     The previous description of the disclosed aspects is provided to enable a person skilled in the art to make or use the disclosed aspects. Various modifications to these aspects will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other aspects without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the aspects shown herein but is to be accorded the widest scope possible consistent with the principles and novel features as defined by the following claims.