Abstract:
A method for audio signal processing and system thereof, the method includes the steps of: obtaining first audio signal information, obtaining second audio signal information, determining an audio parameter based on the first audio signal information and the second audio signal information, modulating the first audio signal information and the second audio signal information based on the audio parameter to generate a first outputting audio signal and a second outputting audio signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 104,126,752 filed in Taiwan, R.O.C. on Aug. 17, 2015, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND 
       [0002]    Technical Field 
         [0003]    The present disclosure relates to a method for audio processing and a system thereof, particularly relates to a method for audio processing and a system thereof simulating a headphone. 
         [0004]    Description of the Related Art 
         [0005]    Using a headphone as an audio player brings users a great surround sound of user experiences. However, using the headphone for a long time may cause hearing damages. Therefore, the method of simulating a headphone with speakers is developed. 
         [0006]    However, the method of simulating a headphone with speakers in the prior art is letting the user not to hear the sound of the right channel with the left ear and not to hear the sound of the left channel with the right ear. The surround sound of the headphone is poorly performed when simulating the headphone with speakers. Therefore, how to perform the directional information of the surround sound with speakers in the headphone simulation system is still a problem to be overcome. 
       SUMMARY 
       [0007]    A method for audio signal processing for a system for audio signal processing includes obtaining a first sub-band audio of a first audio signal information, obtaining a second sub-band audio of a second audio signal information, determining an audio parameter according to the first sub-band audio and the second sub-band audio, and modulating the first audio signal information and the second audio signal information using the audio parameter to obtain a first outputting audio signal and a second outputting audio signal. 
         [0008]    A system for audio signal processing includes a first filter, a second filter, an audio amplifier, an audio modulator, and an audio player. The first filter is for filtering a first audio signal information to obtain a first low frequency audio of the first audio signal information and a first sub audio of the first audio signal information, and the first sub audio and the first low frequency audio from the first audio signal information. The second filter is for filtering the second audio signal information to obtain a second low frequency audio of the second audio signal information and a second sub audio of the second audio signal information, and the second sub audio and the second low frequency audio form the second audio signal information. The audio amplifier is coupled to the first filter and the second filter, and is for determining an audio amplifying parameter according to the first sub audio and the second sub audio and amplifying the first sub audio and the second sub audio using the audio amplifying parameter. The audio modulator is coupled to the first filter, the second filter, and the audio amplifier respectively, and is for generating a first outputting audio signal and a second outputting audio signal according to the first low frequency audio, the second low frequency audio, the amplified first sub audio, and the amplified second sub audio. The audio player is coupled to the audio modulator, and is for outputting the first outputting audio signal and the second outputting audio signal. 
         [0009]    The method for audio signal processing of the present disclosure captures the medium frequency or medium high frequency audio from the first audio signal information of the first channel and the second audio signal information of the second channel respectively and accordingly adjusts and amplifies the medium frequency audio of the first audio signal information and the medium frequency audio of the second audio signal information to enrich the directional information of the outputted audio. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present disclosure will become more fully understood from the detailed description given herein below and the accompanying drawings, which are given by way of illustration only and thus are not limitative of the present disclosure and wherein: 
           [0011]      FIG. 1  is a structural diagram of the system for audio signal processing according to an embodiment; 
           [0012]      FIG. 2  is a structural diagram of the audio amplifier according to an embodiment; 
           [0013]      FIG. 3  is a practical usage diagram of the system for audio signal processing according to an embodiment; and 
           [0014]      FIG. 4  is a functional block diagram of the first filter according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawings. Due to the characteristic of digital signal processing (DSP) area, the devices and components of the present disclosure are implemented by software, firmware, and hardware to realize digital audio processing and playing. 
         [0016]    Please refer to  FIG. 1 .  FIG. 1  is a structural diagram of the system for audio signal processing according to an embodiment. As shown in  FIG. 1 , the system for audio signal processing  1000  includes a first filter  1100 , a second filter  1200 , an audio amplifier  1300 , an audio modulator  1400 , and an audio player  1500 . The first filter  1100  and the second filter  1200  are both coupled to the audio amplifier  1300  and the audio modulator  1400 . The audio amplifier  1300  is coupled to the audio modulator  1400 . The audio modulator  1400  is coupled to the audio player  1500 . 
         [0017]    In an embodiment, please refer to  FIG. 1 . The first filter  1100  and the second filter  1200  both include a low-pass filter (LPF). Taking the first filter  1100  for example, the first low-pass filter  1110  of the first filter  1100  is for filtering the first audio signal information A 1  from the first channel to obtain the low frequency audio A 1 L of the first audio signal information A 1 , and the first filter  1100  subtracts the low frequency audio A 1 L from the first audio signal information A 1  to obtain the first sub audio A 11 . The second low-pass filter of the second filter  1200  is also for filtering the second audio signal information A 2  from the second channel to obtain the low frequency audio A 2 L of the second audio signal information A 2 , and the second filter  1200  subtracts the low frequency audio A 2 L from the second audio signal information A 2  to obtain the second sub audio A 21 . Therefore, in the present embodiment, the first sub audio A 11  is the high frequency part of the first audio signal information A 1  and the second sub audio A 21  is the high frequency part of the second audio signal information A 2 . 
         [0018]    The audio amplifier  1300  is for amplifying the first sub audio A 11  and the second sub audio A 21  according to the details of the first sub audio A 11  and the second sub audio A 21 . Specifically, please refer to  FIG. 2 .  FIG. 2  is a structural diagram of the audio amplifier according to an embodiment. As shown in  FIG. 2 , the audio amplifier  1300  includes a wave envelope detecting module  1310  and a controllable amplifying module  1320 . The input terminal of the wave envelope detecting module  1310  is coupled to the first filter  1100  and the second filter  1200 . The output terminal of the wave envelope detecting module  1310  is coupled to the controllable amplifying module  1320 . The output terminal of the controllable amplifying module  1320  is coupled to the audio modulator  1400 . 
         [0019]    The wave envelope detecting module  1310  is for detecting the wave envelopes of the first sub audio A 11  and the second sub audio A 21 , and for determining an audio amplifying parameter according to the wave envelopes of the first sub audio A 11  and the second sub audio A 21 . In an embodiment, the wave envelope detecting module  1310  detects the first wave envelope of the first sub audio A 11  and the second wave envelope of the second sub audio A 21 , and compares the level of the second sub audio A 21  with the level of the second wave envelope, and determines the audio amplifying parameter according to the maximum level corresponding to the first wave envelope and the second wave envelope. More specifically, when the maximum level corresponding to the first wave envelope is greater than the maximum level corresponding to the second wave envelope, the wave envelope detecting module  1310  determines the audio amplifying parameter according to the maximum level corresponding to the first wave envelope. When the maximum level corresponding to the first wave envelope is not greater than the maximum level corresponding to the second wave envelope, the wave envelope detecting module  1310  determines the audio amplifying parameter according to the maximum level corresponding to the second wave envelope. The controllable amplifying module  1320  is for amplifying the first wave envelope of the first sub audio A 11  and the second wave envelope of the second sub audio A 21  according to the amplifying parameter. 
         [0020]    The audio modulator  1400  is for mixing the high frequency audio A 2 H of the second audio signal information A 2  and the amplified first sub audio A 11  delaying for a first duration P 1  with the low frequency audio A 2 L of the second audio signal information A 2  and the amplified second sub audio A 21  to generate a second outputting audio signal A 2   o . Similarly, the audio modulator  1400  mixes the high frequency audio A 1 H of the second audio signal information A 1  and the amplified second sub audio A 21  delaying for a first duration P 1  with the low frequency audio A 1 L of the first audio signal information A 1  and the amplified first sub audio A 11  to generate a first outputting audio signal A 1   o.    
         [0021]    The audio player  1500  includes a first channel speaker  1510  and a second channel speaker  1520 . The first channel speaker  1510  and the second channel speaker  1520  are both coupled to the audio modulator  1400 , and the first channel speaker  1510  is for outputting the first outputting audio signal A 1   o  to an analog audio and the second channel speaker  1520  is for outputting the second outputting audio signal A 2   o  to an analog audio. 
         [0022]    Please refer to  FIG. 3 .  FIG. 3  is a practical usage diagram of the system for audio signal processing according to an embodiment. As shown in  FIG. 3 , when a user  2000  is in front of the first channel speaker  1510  and the second channel speaker  1520 , the user  2000  listens to the first outputting audio signal A 1   o  outputted from the first channel speaker  1510  with the right ear, and listens to the second outputting audio signal A 2   o  outputted from the second channel speaker  1520 . As shown in  FIG. 3 , the distance D 1  between the first channel speaker  1510  and the right ear is different from the distance D 2  between the second channel speaker  1520  and the right ear, and the distance D 2  is greater than the distance D 1 . Therefore, there is an interval difference between the first outputting audio signal A 1   o  and the second outputting audio signal A 2   o  when the right ear listens to the first outputting audio signal A 1   o  and the second outputting audio signal A 2   o , and the time interval is exactly equal or approximate to the first duration P 1 , so that the part of the second audio signal information A 2  in the first outputting audio signal A 1   o  and the part of the second audio signal information A 2  in the second outputting audio signal A 2   o  are cancelled to each other. Therefore, although the user  2000  is not using a headphone, the right ear almost only receives the audio signal of the first sub audio A 11  adjusted by the audio amplifier  1300  and the low frequency audio A 1 L of the first audio signal information A 1 . Due to the same principle, the left ear almost only receives the second sub audio A 21  adjusted by the audio amplifier  1300  and the low frequency audio A 2 L of the second audio signal information A 2 . 
         [0023]    In an embodiment, as the distance D 1  and the distance D 2  changes, adequate adjustment for amplifying or modulating the first audio signal information A 1  and the second audio signal information A 2  are needed for the user  2000  to obtain a better listening enjoyment. Please refer back to  FIG. 1 . The system for audio signal processing  1000  further includes a distance detector  1600 . The distance detector  1600  is coupled to the audio amplifier  1300  and is for detecting the distance between the user  2000  and the first channel speaker  1510  and the distance between the user  2000  and the second channel speaker  1520 . In an embodiment, the distance detector  1600  is a laser distance detector for detecting the distance between the user  2000  and the first channel speaker  1510 . In another embodiment, the distance detector  1600  is a microphone on the user  2000  to receive the sound from the first channel speaker  1510  and the second channel speaker  1520  for determining the distance between the user  2000  and the first channel speaker  1510  and the distance between the user  2000  and the second channel speaker  1520  accordingly and sending the distances to the first filter  1100  and the second filter  1200 . The first filter  1100  determines the frequency response according to the distance. The second filter  1200  determines the frequency response according to the distance. Taking the first filter  1100  for example, the first filter  1100  determines the gain or attenuation of the frequency band according to the distance D 1 , wherein the frequency band is low frequency, medium frequency, and/or high frequency. 
         [0024]    The reason why the audio amplifier  1300  does not process the low frequency audio A 1 L of the first audio signal information A 1  and the low frequency audio A 2 L of the second audio signal information A 2  is that the sound with low frequency contains less directional information to human hearing system. Therefore, the audio amplifier  1300  only processes the medium high frequency audio signal, so that the user  2000  sufficiently obtains the directional information from the first outputting audio signal A 1   o  and the second outputting audio signal A 2   o.    
         [0025]    In some embodiments, the outputted frequency responses of the first channel speaker  1510  and the second channel speaker  1520  are not the same, so the frequency response of the first filter  1100  is correspondingly set according to the frequency response of the first channel speaker  1510  and the frequency response of the second filter  1200  is correspondingly set according to the frequency response of the second channel speaker  1520 . The specific implementation is described as follows. The first audio signal information A 1  and second audio signal information A 2  are added with a white noise or a sweep tone and are outputted from the aforementioned system structure. The audio outputted from the two speakers is received by an audio receiver, such as a microphone. 
         [0026]    The frequency response of the first filter  1100  and the frequency response of the second filter  1200  are adjusted accordingly until the audio outputted from the two speakers are the same. 
         [0027]    In some other embodiments, please refer to  FIG. 4 .  FIG. 4  is a functional block diagram of the first filter according to an embodiment. As shown in  FIG. 4 , the first filter  1100  includes a low-pass filter (LPF) and a high-pass filter (HPF). The first low-pass filter  1110  of the first filter  1100  is for filtering the first audio signal information A 1  from the first channel to obtain the low frequency audio A 1 L of the first audio signal information A 1 . The first high-pass filter  1120  of the first filter  1100  is for filtering the first audio signal information A 1  from the first channel to obtain the high frequency audio A 1 H of the first audio signal information A 1 . The first filter  1100  subtracts the low frequency audio A 1 L and the high frequency audio A 1 H from the first audio signal information A 1  to obtain the first sub audio A 11 ′. The second filter  1200  has the same structure, so that the second filter outputs the high frequency audio A 2 H, the low frequency audio A 2 L, and the second sub audio A 21 ′ of the second audio signal information A 1 . Therefore, taking the present embodiment for example, the first sub audio A 11 ′ is the medium frequency part of the first audio signal information A 1  and the second sub audio A 21 ′ is the medium frequency part of the second audio signal information A 2 . The audio amplifier  1300  receives the first sub audio A 11 ′ and the second sub audio A 21 ′ and performs the aforementioned processing method of the present disclosure. The audio modulator  1400  directly receives the high frequency audio A 1 H and the low frequency audio A 1 L of the first audio signal information A 1  from the first filter  1100 , and directly receives the high frequency audio and the low frequency audio of the second audio signal information A 2  from the second filter  1200 . The audio modulator  1400  combines the audio from the first filter  1100  and the second filter  1200  with the first sub audio A 11 ′ and the second sub audio A 12 ′ processed by the audio amplifier  1300 , and eventually outputs the first outputting audio signal A 1   o  and the second outputting audio signal A 2   o  after performing the aforementioned process. 
         [0028]    The method for audio signal processing of the present disclosure captures the medium frequency or medium high frequency audio from the first audio signal information of the first channel and the second audio signal information of the second channel respectively and accordingly adjusts and amplifies the medium frequency audio of the first audio signal information and the medium frequency audio of the second audio signal information to enrich the directional information of the outputted audio. 
         [0029]    The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the disclosure to the precise forms or embodiments disclosed. Modifications and adaptations will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the disclosure. It is intended, therefore, that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims and their full scope of equivalents.