Audio encoding device, audio encoding method, and audio encoding program for encoding a wide-band audio signal

• US 8,082,156 B2
• Filed: 01/06/2006
• Issued: 12/20/2011
• Est. Priority Date: 01/11/2005
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Shimada, Osamu
• Primary Examiner(s): MCFADDEN, SUSAN IRIS
• Application Number:
  US11/794,984
• Publication Number:
  US 20080140425A1
• Time in Patent Office: 2,174 Days
• Field of Search: 704/500
• US Class Current: 704/500
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/20 using sound class specific coding, hybrid encoders or object based coding
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

By using a high-range sub-band signal, a correction coefficient corresponding to importance of auditory sense is calculated to correct a noise level and generate additional signal information, thereby accurately reflecting the noise level of the sub-band important in the auditory sense. Thus, it is possible to calculate additional signal information reflecting the noise level of the sub-band important in the auditory sense according to importance with a small calculation amount. The calculation amount can further be reduced by using a correction coefficient based on the characteristic of an ordinary audio signal.

Claims

1. An audio encoding device for dividing an input signal into a low-frequency-band signal having a low frequency band and a high-frequency-band signal having a high frequency band, mixing a signal obtained by converting said low-frequency-band signal and a noise signal, and encoding noise signal information that is used in expressing the high-frequency-band signal, comprising:

an importance calculation unit for calculating energy of said high-frequency-band signal for each high-frequency band and calculating a correction coefficient such that a value of the correction coefficient is small for a high frequency band based upon said energy for each high-frequency band; and

a noise signal information correction unit for correcting said noise signal information based upon said correction coefficient for each high-frequency band using a processor.

2. The audio encoding device according to claim 1, further comprising a noise signal information integration unit for integrating said corrected noise signal information for each high-frequency band and calculating the noise signal information that is used in common in a plurality of the frequency bands.

3. The audio encoding device according to claim 1, wherein said importance calculation unit smoothes the correction coefficient of said high-frequency-band signal for each high-frequency band at least in one of a time direction and a frequency direction.

4. The audio encoding device according to claim 1, wherein said noise signal information is a noise level indicating a ratio of the noise signal over said high-frequency-band signal.

5. The audio encoding device according to claim 1, further comprising smoothing the correction coefficient calculated responding to each frequency component of said high-frequency-band signal at least in one of a time direction and a frequency direction.

6. The audio encoding device according to claim 1, wherein said noise signal information is a noise level indicating a ratio of the noise signal over said high-frequency-band signal.

7. An audio encoding method for dividing an input signal into a low-frequency-band signal having a low frequency band and a high-frequency-band signal having a high frequency band, mixing a signal obtained by converting said low-frequency-band signal and a noise signal, and encoding noise signal information that is used in expressing the high-frequency-band signal, comprising the steps of:

calculating energy of said high-frequency-band signal for each high-frequency band;

calculating a correction coefficient such that a value of the correction coefficient is small for a high-frequency band based upon said energy for each high-frequency band; and

correcting said noise signal information based upon said correction coefficient for each high-frequency band using a processor.

8. The audio encoding method according to claim 7, further comprising integrating said corrected noise signal information for each high-frequency band and calculating the noise signal information that is used in common in a plurality of the frequency bands.

9. The audio encoding method according to claim 7 wherein said calculating step smoothes the correction coefficient of said high-frequency-band signal for each high-frequency band at least in one of a time direction and a frequency direction.

10. The audio encoding method according to claim 7, wherein said noise signal information is a noise level indicating a ratio of the noise signal over said high-frequency-band signal.

11. The audio encoding method according to claim 7, further comprising smoothing the correction coefficient calculated responding to each frequency component of said high-frequency-band signal at least in one of a time direction and a frequency direction.

12. The audio encoding method according to claim 7, wherein said noise signal information is a noise level indicating a ratio of the noise signal over said high-frequency-band signal.

13. A non-transitory computer-readable medium having stored thereon an audio encoding program for dividing an input signal into a low-frequency-band signal having a low frequency band and a high-frequency-band signal having a high frequency band, mixing a signal obtained by converting said low-frequency-band signal and a noise signal, and encoding noise signal information that is used in expressing the high-frequency-band signal, the audio encoding program having computer-executable instructions for performing a method comprising:

calculating energy of said high-frequency-band signal for each high-frequency band;

calculating a correction coefficient such that a value of the correction coefficient is small for a high-frequency band based upon said energy for each high-frequency band; and

correcting said noise signal information based upon said correction coefficient for each high-frequency band using a processor.