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, performed by an audio signal processing device, for processing an encoded signal, the encoded signal comprising lower frequency spectrum data and spectrum extension data, the method comprising:
 determining a first parameter and a second parameter from the spectrum extension data of the encoded signal;   decoding the lower frequency spectrum data of the encoded signal to reproduce a decoded lower frequency spectrum signal;   generating a higher frequency spectrum signal from the decoded lower frequency spectrum signal by copying a partial spectrum signal from among a plurality of partial spectrum signals which form the decoded lower frequency spectrum signal, wherein the partial spectrum signal is indicated by the first parameter;   generating a gain-adjusted higher frequency spectrum signal by applying a gain indicated by the second parameter to the higher frequency spectrum signal;   generating a combined frequency spectrum signal by combining the gain-adjusted higher frequency spectrum signal and the decoded lower frequency spectrum signal; and   transforming the combined frequency spectrum signal into a time domain signal,   wherein one or more of the determining the first parameter and the second parameter, the decoding the lower frequency spectrum data, the generating the higher frequency spectrum signal, the generating the gain-adjusted higher frequency spectrum signal, the generating the combined frequency spectrum signal, and the transforming the combined frequency spectrum signal is implemented, at least in part, by one of more hardware elements of the audio signal processing device.   
     
     
       20. An audio signal processing device for processing an encoded signal, the encoded signal comprising lower frequency spectrum data and spectrum extension data, wherein the audio signal processing device:
 determines a first parameter and a second parameter from the spectrum extension data of the encoded signal;   decodes the lower frequency spectrum data of the encoded signal to reproduce a decoded lower frequency spectrum signal;   generates a higher frequency spectrum signal from the decoded lower frequency spectrum signal by copying a partial spectrum signal from among a plurality of partial spectrum signals which form the decoded lower frequency decoded spectrum signal, wherein the partial spectrum signal is indicated by the first parameter;   generates a gain-adjusted higher frequency spectrum signal by applying a gain indicated by the second parameter to the higher frequency spectrum signal;   generates a combined frequency spectrum signal by combining the gain-adjusted higher frequency spectrum signal and the decoded lower frequency spectrum signal; and   transforms the combined frequency spectrum signal into a time domain signal,   wherein one or more of the determining the first parameter and the second parameter, the decoding the lower frequency spectrum data, the generating the higher frequency spectrum signal, the generating the gain-adjusted higher frequency spectrum signal, the generating the combined frequency spectrum signal, and the transforming the combined frequency spectrum signal is implemented, at least in part, by one of more hardware elements of the audio signal processing device.