DECODER, ENCODER, AND METHODS THEREOF

• US 20130085752A1
• Filed: 05/27/2011
• Published: 04/04/2013
• Est. Priority Date: 06/11/2010
• Status: Active Grant

• Current Assignee: III Holdings 12, LLC (Intellectual Ventures LLC)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Kawashima, Takuya, Oshikiri, Masahiro
• Granted Patent: US 9,082,412 B2
• Time in Patent Office: Days
• US Class Current: 704/225
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 19/22 Mode decision, i.e. based on audio signal content versus external parameters
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
• CPC Class Codes: G10L 21/034 Automatic adjustment

Abstract

Disclosed is a decoder capable of improving the sound quality of a decoded sound signal in an encoding method which combines speech encoding and music encoding in a hierarchical structure. A transform-encoding decoding unit (202) decodes transform-encoded data to generate a spectrum of a decoded transform-encoded signal. A band decision unit (203) uses the spectrum of the decoded transform-encoded signal to decide whether each of a plurality of bands in which frequency components of an input signal are divided constitute a first band in which a transform encoded pulse is not established or a second band in which said pulse is established. A CELP component suppression unit (207) suppresses the spectrum of a CELP decoded signal, which is the frequency component of a decoded signal of CELP encoded data, to the extent that suppression in the first band is weaker than suppression in the second band.

Claims

1. A decoding apparatus that receives and decodes first coded data generated through speech coding and second coded data generated through music coding, the apparatus comprising:

a first decoding section that performs an orthogonal transformation on a signal obtained by decoding the first coded data, to generate a first spectrum;

a second decoding section that decodes the second coded data to generate a second spectrum;

an identification section that identifies a first band in which a degree of suppression of an amplitude of the first spectrum is adjusted, using the second spectrum; and

a suppressing section that suppresses an amplitude of the first band of the first spectrum based on the adjusted degree.

2. The decoding apparatus according to claim 1, wherein the identification section identifies, as the first band, a band including pulses generated by the music coding, from a plurality of bands obtained by dividing frequency components of the second spectrum.

3. The decoding apparatus according to claim 1, wherein the suppressing section adjusts the degree of the suppression in the first band to a lower level than that in a band other than the first band and suppresses the amplitude of the first spectrum.

4. The decoding apparatus according to claim 1, wherein:

the second coded data is generated through transform coding as the music coding; and

the identification section identifies the first band by determining whether each of a plurality of bands obtained by dividing frequency components is the first band in which no pulse is generated by the transform coding or a second band in which the pulses are generated, using the second spectrum.

5. The decoding apparatus according to claim 4, wherein the suppressing section adjusts the degree of the suppression in the first band to a lower level than that in the second band and suppresses the amplitude of the first spectrum.

6. The decoding apparatus according to claim 5 further comprising an adjusting section that adjusts a suppressing coefficient indicating the degree of suppression to the first spectrum, a value of the suppressing coefficient decreasing with an increase in the degree of the suppression, and adjusts the suppressing coefficient in the first band to a higher level than the suppressing coefficient in the second band, wherein the suppressing section suppresses the first spectrum by multiplying the first spectrum by the suppressing coefficient.

7. The decoding apparatus according to claim 5, wherein:

the identification section further determines whether a band determined to be the second band among the plurality of bands is a third band having a high pulse density or a fourth band having a low pulse density; and

the suppressing section suppresses the first spectrum in the third band at a higher degree than suppression in the fourth band and suppresses the first spectrum in the first band at a lower degree than suppression in the fourth band.

8. The decoding apparatus according to claim 7 further comprising an adjusting section that adjusts a suppressing coefficient indicating the degree of suppression to the first spectrum, a value of the suppressing coefficient decreasing with an increase in the degree of the suppressing, and adjusts the suppressing coefficient in the third band to a lower level than the suppressing coefficient in the fourth band and adjusts the suppressing coefficient in the first band to a higher level than the suppressing coefficient in the fourth band, wherein the suppressing section suppresses the first spectrum by multiplying the first spectrum by the suppressing coefficient.

9. The decoding apparatus according to claim 5, wherein:

the identification section further determines whether a band determined to be the second band among the plurality of bands is a third band having a high pulse density or a fourth band having a low pulse density; and

the suppressing section suppresses the first spectrum at a frequency in which the pulses are not generated in the third band, at a higher degree than suppression in the fourth band, suppresses the first spectrum at a frequency in which the pulses are generated in the third band at the same degree as suppression in the fourth band, and suppresses the first spectrum in the first band at a lower degree than suppression in the fourth band.

10. The decoding apparatus according to claim 1, wherein:

the second decoding section comprises a third decoding section that decodes the second coded data to generate a selected spectrum, and a band restoring section that receives band selection information indicating a band subjected to the music coding upon the generation of the second coded data and generates the second spectrum using the band selection information and the selected spectrum; and

the identification section identifies the first band further using the band selection information.

11. A coding apparatus comprising:

a first coding section that encodes an input signal through speech coding to generate a first code and performs an orthogonal transformation on a signal obtained by decoding the first code, to generate a first spectrum;

a spectrum generating section that performs the orthogonal transformation on the input signal to generate a second spectrum;

a band selection section that divides a frequency band into a plurality of bands, selects a preset number of bands based on an energy of a residual signal between the first spectrum and the second spectrum, generates band selection information indicating information about the selected band, outputs a spectrum of the selected band in the first spectrum as a first selected spectrum, and outputs a spectrum of the selected band in the second spectrum as a second selected spectrum;

a suppressing section that suppresses an amplitude of the first selected spectrum using a suppressing coefficient representing the degree of suppression, to generate a suppressed spectrum;

a residual spectrum calculating section that calculates a difference between the second selected spectrum and the suppressed spectrum to generate a residual spectrum;

a second coding section that encodes the residual spectrum through music coding to generate a second code, and decodes the second code to generate a decoded residual spectrum;

a decoded spectrum generating section that generates a decoded spectrum using the suppressed spectrum and the decoded residual spectrum; and

a distortion evaluating section that calculates distortion between the second selected spectrum and the decoded spectrum and searches for the suppressing coefficient which minimizes the distortion.

12. A decoding method that receives and decodes first coded data generated through speech coding and second coded data generated through music coding, the method comprising:

a first decoding step of performing an orthogonal transformation on a signal obtained by decoding the first coded data, to generate a first spectrum;

a second decoding step of decoding the second coded data to generate a second spectrum;

an identification step of identifying a first band in which a degree of suppression of an amplitude of the first spectrum is adjusted, using the second spectrum; and

a suppressing step of suppressing an amplitude of the first band of the first spectrum based on the adjusted degree.

13. A coding method comprising:

a first coding step of encoding an input signal through speech coding to generate a first code and performing an orthogonal transformation on a signal obtained by decoding the first code to generate a first spectrum;

a spectrum generating step of performing the orthogonal transformation on the input signal to generate a second spectrum;

a band selection step of dividing a frequency band into a plurality of bands, selecting a preset number of bands based on an energy of a residual signal between the first spectrum and the second spectrum, generating band selection information indicating information about the selected band, outputting a spectrum of the selected band in the first spectrum as a first selected spectrum, and outputting a spectrum of the selected band in the second spectrum as a second selected spectrum;

a suppressing step of suppressing an amplitude of the first selected spectrum using a suppressing coefficient representing the degree of suppression, to generate a suppressed spectrum;

a residual spectrum calculating step of calculating a difference between the second selected spectrum and the suppressed spectrum to generate a residual spectrum;

a second coding step of encoding the residual spectrum through music coding to generate a second code, and decoding the second code to generate a decoded residual spectrum;

a decoded spectrum generating step of generating a decoded spectrum using the suppressed spectrum and the decoded residual spectrum; and

a distortion evaluating step of calculating distortion between the second selected spectrum and the decoded spectrum and searching for the suppressing coefficient which minimizes the distortion.