Encoding device and decoding device

Abstract

An encoding device ( 200 ) includes an MDCT unit ( 202 ) that transforms an input signal in a time domain into a frequency spectrum including a lower frequency spectrum, a BWE encoding unit ( 204 ) that generates extension data which specifies a higher frequency spectrum at a higher frequency than the lower frequency spectrum, and an encoded data stream generating unit ( 205 ) that encodes to output the lower frequency spectrum obtained by the MDCT unit ( 202 ) and the extension data obtained by the BWE encoding unit ( 204 ). The BWE encoding unit ( 204 ) generates as the extension data (i) a first parameter which specifies a lower subband which is to be copied as the higher frequency spectrum from among a plurality of the lower subbands which form the lower frequency spectrum obtained by the MDCT unit ( 202 ) and (ii) a second parameter which specifies a gain of the lower subband after being copied.

The invention claimed is: 
     
       1. An encoding device that encodes an input signal comprising:
 a time-frequency transforming unit operable to transform an input signal in a time domain into a frequency spectrum including a lower frequency spectrum;   a band extending unit operable to generate extension data used for specifying a higher frequency spectrum at higher frequency than the lower frequency spectrum; and   an encoding unit operable to encode the lower frequency spectrum and the extension data, and output the encoded lower frequency spectrum and extension data,   wherein the band extending unit generates a first parameter and a second parameter as the extension data, the first parameter is used to determine a partial spectrum which is to be copied as the higher frequency spectrum from among a plurality of the partial spectrums which form the lower frequency spectrum, and the second parameter is used to determine a gain of the partial spectrum after being copied, and   wherein the band extending unit generates, as the extension data, a third parameter which is used to determine whether or not the partial spectrum to be copied is inverted on a frequency domain.   
     
     
       2. The encoding device according to  claim 1 ,
 wherein the band extending unit generates, as the extension data, a fourth parameter indicating whether or not a phase of the partial spectrum to be copied is inverted.   
     
     
       3. The encoding device according to  claim 1 ,
 wherein the time-frequency transforming unit is operable to perform MDCT (Modified Discrete Cosine Transform) on an input signal in a time domain into a frequency spectrum including a lower frequency spectrum.   
     
     
       4. The encoding device according to  claim 1 ,
 wherein the band extending unit further generates a parameter specifying energy of a noise spectrum which is added to the higher frequency spectrum specified by the first parameter and the second parameter as the extension data, and   the parameter specifying energy of a noise spectrum is an energy ratio of the noise spectrum against the higher frequency spectrum.   
     
     
       5. The encoding device according to  claim 1 ,
 wherein the first parameter includes information indicating whether or not to use the same extension data as that of a preceding frame.   
     
     
       6. The encoding device according to  claim 4 ,
 wherein the first parameter includes information indicating whether or not to use the same extension data as that of an immediately preceding frame.   
     
     
       7. An encoding method for encoding an input signal, comprising:
 a time-frequency transforming step of transforming an input signal in a time domain into a frequency spectrum including a lower frequency spectrum;   a band extending step of generating extension data used for specifying a higher frequency spectrum at higher frequency than the lower frequency spectrum; and   an encoding step of encoding the lower frequency spectrum and the extension data, and outputting the encoded lower frequency spectrum and extension data,   wherein the band extending step generates a first parameter and a second parameter as the extension data, the first parameter is used to determine a partial spectrum which is to be copied as the higher frequency spectrum from among a plurality of the partial spectrums which form the lower frequency spectrum, and the second parameter is used to determine a gain of the partial spectrum after being copied, and   wherein the band extending step generates, as the extension data, a third parameter which is used to determine whether or not the partial spectrum to be copied is inverted on a frequency domain.   
     
     
       8. The encoding method according to  claim 7 ,
 wherein the band extending step generates, as the extension data, a fourth parameter indicating whether or not a phase of the partial spectrum to be copied is inverted.   
     
     
       9. A non-transitory computer-readable recording medium having recorded thereon an encoding program for encoding an input signal, the program causing a computer to execute the encoding method according to  claim 7 . 
     
     
       10. A decoding device for decoding an encoded signal, comprising:
 a decoding unit operable to decode the encoded signal and to generate therefrom a lower frequency spectrum and extension data used for specifying a higher frequency spectrum at higher frequency than the lower frequency spectrum,   a higher frequency spectrum generating unit operable to generate the higher frequency spectrum based on the lower frequency spectrum and the extension data; and   a time-frequency transforming unit operable to transform a frequency spectrum obtained by combining the generated higher frequency spectrum and the lower frequency spectrum into a signal in a time domain,   wherein the extension data includes a first parameter, a second parameter and a third parameter, and   the first parameter is used to determine a partial spectrum which is to be copied as the higher frequency spectrum from among a plurality of the partial spectrums which form the lower frequency spectrum, the second parameter is used to determine a gain of the partial spectrum after being copied, and the third parameter is used to determine whether or not the partial spectrum to be copied is inverted on a frequency domain.   
     
     
       11. The decoding device according to  claim 10 ,
 wherein the band extending unit generates, as the extension data, a fourth parameter indicating whether or not a phase of the partial spectrum to be copied is inverted.   
     
     
       12. The decoding device according to  claim 11 ,
 wherein the time-frequency transforming unit is operable to perform MDCT (Modified Discrete Cosine Transform) of the frequency spectrum obtained by combining the generated higher frequency spectrum and the lower frequency spectrum into a signal in a time domain.   
     
     
       13. The decoding device according to  claim 12 ,
 wherein, the extension data further includes a parameter specifying energy of a noise spectrum which is added to the higher frequency spectrum specified by the first parameter and the second parameter,   the parameter specifying energy of a noise spectrum is an energy ratio of the noise spectrum against the higher frequency spectrum, and   the higher frequency spectrum generating unit adds a noise spectrum having energy specified by said parameter specifying energy of a noise spectrum to the generated higher frequency spectrum.   
     
     
       14. The decoding device according to  claim 10 ,
 wherein the first parameter includes information indicating whether or not to use the same extension data as that of a preceding frame, and   the higher frequency spectrum generating unit generates the higher frequency spectrum by using the information.   
     
     
       15. The decoding device according to  claim 14 , wherein the first parameter includes information indicating whether or not to use the same extension data as that of an immediately preceding frame. 
     
     
       16. A decoding method of decoding an encoded signal, the decoding method comprising:
 a decoding step of decoding the encoded signal to generate therefrom a lower frequency spectrum and extension data used for specifying a higher frequency spectrum at higher frequency than the lower frequency spectrum,   a higher frequency spectrum generating step of generating the higher frequency spectrum based on the lower frequency spectrum and the extension data; and   a time-frequency transforming step of transforming a frequency spectrum obtained by combining the generated higher frequency spectrum and the lower frequency spectrum into a signal in a time domain,   wherein the extension data includes a first parameter, a second parameter and a third parameter, and   the first parameter is used to determine a partial spectrum which is to be copied as the higher frequency spectrum from among a plurality of the partial spectrums which form the lower frequency spectrum, the second parameter is used to determine a gain of the partial spectrum after being copied, and the third parameter is used to determine whether or not the partial spectrum to be copied is inverted on a frequency domain.   
     
     
       17. The decoding method according to  claim 16 ,
 wherein the extension data further includes a fourth parameter indicating whether or not a phase of the partial spectrum to be copied is inverted.   
     
     
       18. A non-transitory computer-readable recording medium having recorded thereon a decoding program for decoding an encoded signal, the program causing a computer to execute the decoding method according to  claim 16 . 
     
     
       19. A method for decoding an encoded audio signal, the method comprising:
 receiving the encoded audio signal and obtaining therefrom a lower frequency spectrum and extension data, wherein the lower frequency spectrum includes a plurality of frequency domain coefficients and the extension data includes one or more gain parameters;   reconstructing a higher frequency spectrum from the lower frequency spectrum, wherein generating a higher frequency spectrum signal of the higher frequency spectrum comprises inserting a copy of a partial spectrum signal as the higher frequency spectrum signal, wherein the partial spectrum signal is copied from among a plurality of partial spectrum signals which form the lower frequency spectrum;   applying one or more gains indicated by the one or more gain parameters to the higher frequency spectrum to form a gain-adjusted higher frequency spectrum;   combining the gain-adjusted higher frequency spectrum and the lower frequency spectrum to form a combined spectrum; and   transforming the combined spectrum from a frequency domain to a time domain,   wherein the higher frequency spectrum signal comprises frequencies not present in the lower frequency spectrum.   
     
     
       20. The method of claim 19 wherein the one or more gains represent energies of bands of the higher frequency spectrum. 
     
     
       21. The method of claim 19 wherein the higher frequency spectrum includes only a portion of a spectrum above the lower frequency spectrum. 
     
     
       22. The method of claim 19 wherein the frequency domain coefficients comprise MDCT frequency domain coefficients. 
     
     
       23. The method of claim 19 wherein the frequency domain coefficients are generated using a 256-point MDCT. 
     
     
       24. The method of claim 19 further comprising adding a noise spectrum to the higher frequency spectrum. 
     
     
       25. The method of claim 19 wherein the transforming comprises performing an inverse MDCT on the combined spectrum. 
     
     
       26. The method of claim 19 wherein the extension data further includes a first parameter for specifying the partial spectrum which is to be copied from among the plurality of partial spectrums which form the lower frequency spectrum. 
     
     
       27. The method of claim 19 wherein the gain parameter, the first parameter, and the third parameter are encoded in the encoded audio signal. 
     
     
       28. An audio decoder for decoding an encoded audio signal, wherein the audio decoder:
 receives the encoded audio signal and obtains therefrom a lower frequency spectrum and extension data, wherein the lower frequency spectrum includes a plurality of frequency domain coefficients and the extension data includes one or more gain parameters;   reconstructs a higher frequency spectrum from the lower frequency spectrum, wherein generating a higher frequency spectrum signal of the higher frequency spectrum comprises inserting a copy of a partial spectrum signal as the higher frequency spectrum signal, wherein the partial spectrum signal is copied from among a plurality of partial spectrum signals which form the lower frequency spectrum;   applies one or more gains indicated by the one or more gain parameters to the higher frequency spectrum to form a gain-adjusted higher frequency spectrum;   combines the gain-adjusted higher frequency spectrum and the lower frequency spectrum to form a combined spectrum; and   transforms the combined spectrum from a frequency domain to a time domain,   wherein the higher frequency spectrum signal comprises frequencies not present in the lower frequency spectrum.   
     
     
       29. The audio decoder of claim 28 wherein the one or more gains parameters represent energies of bands of the higher frequency spectrum. 
     
     
       30. The audio decoder of claim 28 wherein the higher frequency spectrum includes only a portion of a spectrum above the lower frequency spectrum. 
     
     
       31. The audio decoder of claim 28 wherein the frequency domain coefficients comprise MDCT frequency domain coefficients. 
     
     
       32. The audio decoder of claim 28 wherein the frequency domain coefficients are generated using a 256-point MDCT. 
     
     
       33. The audio decoder of claim 28 further comprising adding a noise spectrum to the higher frequency spectrum. 
     
     
       34. The audio decoder of claim 28 wherein the transforming comprises performing an inverse MDCT. 
     
     
       35. The audio decoder of claim 28 wherein the extension data further includes a first parameter for specifying the partial spectrum which is to be copied from among the plurality of partial spectrums which form the lower frequency spectrum. 
     
     
       36. The audio decoder of claim 28 wherein the gain parameter, the first parameter, and the third parameter are encoded in the encoded audio signal. 
     
     
       37. A computer-readable medium comprising instructions that when executed by a processor perform the method of claim 1.