Method and apparatus for improved weighting filters in a CELP encoder

Abstract

A method of speech encoding comprises generating a first synthesized speech signal from a first excitation signal, weighting the first synthesized speech signal using a first error weighting filter to generate a first weighted speech signal, generating a second synthesized speech signal from a second excitation signal, weighting the second synthesized speech signal using a second error weighting filter to generate a second weighted speech signal, and generating an error signal using the first weighted speech signal and the second weighted speech signal, wherein the first error weighting filter is different from the second error weighting filter. The method may further generate the error signal by weighting the speech signal using a third error weighting filter to generate a third weighted speech signal, and subtracting the first weighted speech signal and the second weighted speech signal from the third weighted speech signal to generate the error signal.

1. A method of speech encoding comprising:
 generating a first synthesized speech signal from a first excitation signal; 
 weighting said first synthesized speech signal using a first error weighting filter to generate a first weighted speech signal; 
 generating a second synthesized speech signal from a second excitation signal; 
 weighting said second synthesized speech signal using a second error weighting filter to generate a second weighted speech signal; and 
 generating an error signal using said first weighted speech signal and said second weighted speech signal; 
 wherein said first error weighting filter is different from said second error weighting filter. 
 
     
     
       2. The method of  claim 1 , wherein said generating said error signal further comprises:
 weighting said speech signal using a third error weighting filter to generate a third weighted speech signal; and 
 subtracting said first weighted speech signal and said second weighted speech signal from said third weighted speech signal to generate said error signal. 
 
     
     
       3. The method of  claim 2 , wherein said third error weighting filter is independent from and the same as said first error weighting filter. 
     
     
       4. The method of  claim 1 , wherein said first excitation signal is from a first codebook and said second excitation signal is from a second codebook, said method further comprising:
 using said error signal to independently select a third excitation signal from said first codebook and a fourth excitation signal from said second codebook; and 
 using said error signal to independently select a third gain to apply to said third excitation signal and a fourth gain to apply to said fourth excitation signal. 
 
     
     
       5. The method of  claim 1 , wherein said generating said first synthesized speech signal uses a first synthesizer and said generating said second synthesized speech signal uses a second synthesizer, and wherein said first synthesizer is independent from said second synthesizer. 
     
     
       6. The method of  claim 5 , wherein said first synthesizer is the same as said second synthesizer. 
     
     
       7. A speech encoder comprising:
 a first codebook; 
 a second codebook; 
 a speech synthesizer configured to generate a first synthesized speech signal from a first excitation signal of said first codebook and to generate a second synthesized speech signal from a second excitation signal of said second codebook; 
 a first error weighting filter configured to generate a first weighted speech signal from said first synthesized speech signal; 
 a second error weighting filter configured to generate a second weighted speech signal from said second synthesized speech signal; and 
 an error signal generator configured to generate an error signal using said first weighted speech signal and said second weighted speech signal; 
 wherein said first error weighting filter is different from said second error weighting filter. 
 
     
     
       8. The speech encoder of  claim 7 , wherein said speech synthesizer includes a first speech synthesizer for generating said first synthesized speech signal and a second speech synthesizer for generating said second synthesized speech signal. 
     
     
       9. The speech encoder of  claim 7  further comprising a third error weighting filter to generate a third weighted speech signal from said speech signal, wherein said error signal generator includes a signal subtractor configured to subtract said first weighted speech signal and said second weighted speech signal from said third weighted speech signal to generate said error signal. 
     
     
       10. The speech encoder of  claim 9 , wherein said third error weighting filter is independent from and the same as said first error weighting filter. 
     
     
       11. The speech encoder of  claim 7 , wherein said speech encoder uses said error signal to independently select a third excitation signal from said first codebook and a fourth excitation signal from said second codebook, and to independently select a third gain to apply to said third excitation signal and a fourth gain to apply to said fourth excitation signal. 
     
     
       12. A speech encoder comprising:
 means for generating a first synthesized speech signal from a first excitation signal; 
 means for weighting said first synthesized speech signal to generate a first weighted speech signal; 
 means for generating a second synthesized speech signal from a second excitation signal; 
 means for weighting said second synthesized speech signal to generate a second weighted speech signal; and 
 means for generating an error signal using said first weighted speech signal and said second weighted speech signal; 
 wherein said means for weighting said first synthesized speech signal is different from said means for weighting said second synthesized speech signal. 
 
     
     
       13. The speech encoder of  claim 12  farther comprising:
 means for weighting said speech signal to generate a third weighted speech signal; and 
 means for subtracting said first weighted speech signal and said second weighted speech signal from said third weighted speech signal to generate said error signal. 
 
     
     
       14. The speech encoder of  claim 13 , wherein means for weighting said speech signal is independent from and the same as said means for weighting said first synthesized speech signal. 
     
     
       15. The speech encoder of  claim 12 , wherein said first excitation signal is from a first codebook and said second excitation signal is from a second codebook, said speech encoder further comprising means for using said error signal to independently select a third excitation signal from said first codebook and a fourth excitation signal from said second codebook, and means for using said error signal to independently select a third gain to apply to said third excitation signal and a fourth gain to apply to said fourth excitation signal. 
     
     
       16. The speech encoder of  claim 12 , wherein said means for generating said first synthesized speech signal is independent from said means for generating said second synthesized speech signal. 
     
     
       17. The speech encoder of  claim 16 , said means for generating said first synthesized speech signal is the same as said means for generating said second synthesized speech signal. 
     
     
       18. A method of encoding a speech signal for use by a device, the method comprising:
 performing, by the device, a first error weighting of the speech signal to generate a weighted speech signal;   generating, by the device, a first synthesized speech signal from a first excitation signal;   performing, by the device, a second error weighting of the first synthesized speech signal to generate a first weighted synthesized speech signal;   generating, by the device, a second synthesized speech signal from a second excitation signal;   performing, by the device, a third error weighting on the second synthesized speech signal to generate a second weighted synthesized speech signal; and   wherein the third error weighting is different from the second error weighting.    
     
     
       19. The method of claim 18 further comprising:
 generating a first error signal as a difference between the weighted speech signal and the first weighted synthesized speech signal.    
     
     
       20. The method of claim 19, wherein the first excitation signal is from the first codebook and the second excitation signal is from a second codebook, the method further comprising:
 using the first error signal to independently select a third excitation signal from the first codebook and a fourth excitation signal from the second codebook; and   using the first error signal to independently select a third gain to apply to the third excitation signal and a fourth gain to apply to the fourth excitation signal.    
     
     
       21. The method of claim 18, wherein the device is a communication device.  
     
     
       22. The method of claim 18, wherein the device is one of a telephone, a mobile phone, a cordless phone, a digital answering machine or a personal digital assistant.  
     
     
       23. The speech encoder of claim 7, wherein the speech encoder is included in a device.  
     
     
       24. The speech encoder of claim 23, wherein the device is a communication device.  
     
     
       25. The speech encoder of claim 23, wherein the device is one of a telephone, a mobile phone, a cordless phone, a digital answering machine or a personal digital assistant.  
     
     
       26. The method of claim 1, wherein the method of speech encoding is performed by a device.  
     
     
       27. The method of claim 26, wherein the device is a communication device.  
     
     
       28. The method of claim 26, wherein the device is one of a telephone, a mobile phone, a cordless phone, a digital answering machine or a personal digital assistant.  
     
     
       29. A device comprising:
 a speech encoder configured to:
 perform a first error weighting of the speech signal to generate a weighted speech signal; 
 generate a first synthesized speech signal from a first excitation signal; 
 perform a second error weighting of the first synthesized speech signal to generate a first weighted synthesized speech signal; 
 generate a second synthesized speech signal from a second excitation signal; 
 perform a third error weighting on the second synthesized speech signal to generate a second weighted synthesized speech signal; and 
 wherein the third error weighting is different from the second error weighting.  
   
     
     
       30. The device of claim 29, wherein the speech encoder is further configured to generate a first error signal as a difference between the weighted speech signal and the first weighted synthesized speech signal.  
     
     
       31. The device of claim 30, wherein the first excitation signal is from the first codebook and the second excitation signal is from a second codebook, and wherein the speech encoder is further configured to:
 Use the first error signal to independently select a third excitation signal from the first codebook and a fourth excitation signal from the second codebook; and   Use the first error signal to independently select a third gain to apply to the third excitation signal and a fourth gain to apply to the fourth excitation signal.    
     
     
       32. The device of claim 29, wherein the device is a communication device.  
     
     
       33. The device of claim 29, wherein the device is one of a telephone, a mobile phone, a cordless phone, a digital answering machine or a personal digital assistant.