Noise detection for audio encoding by mean and variance energy ratio

• US 7,457,747 B2
• Filed: 08/23/2004
• Issued: 11/25/2008
• Est. Priority Date: 08/23/2004
• Status: Expired due to Fees

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Ojanpera, Juha
• Primary Examiner(s): Hudspeth; David R
• Assistant Examiner(s): ALBERTALLI, BRIAN LOUIS
• Application Number:
  US10/924,006
• Publication Number:
  US 20060041426A1
• Time in Patent Office: 1,555 Days
• Field of Search: None
• US Class Current: 704/226
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding

Abstract

The techniques described are utilized for detection of noise and noise-like segments in audio coding. The techniques can include performing a prediction gain calculation, an energy compaction calculation, and a mean and variation energy calculation. Signal adaptive noise decisions can be made both in time and frequency dimensions. The techniques can be embodied as part of an AAC (advanced audio coding) encoder to detect noise and noise-like spectral bands. This detected information is transmitted in a bitstream using a signaling method defined for a perceptual noise substitution (PNS) encoding tool of the AAC encoder.

Claims

1. A method for estimating and detecting noise and noise-like spectral signal segments, the signal segments corresponding to one or more frequency bands of a signal, the method comprising:

calculating mean and variance energies for each frequency band of a signal;

defining boundaries for a ratio of the mean and variance energies in each frequency band of the signal; and

determining if each frequency band of the signal is noise or noise-like using the defined boundaries and a stage of two or more decisions.

2. The method of claim 1, further comprising predicting gain for spectral samples corresponding to each frequency band of a signal.

3. The method of claim 2, wherein predicting gain for spectral samples corresponding to each frequency band of a signal comprises applying linear predictive coding principles and accumulating resulting gain.

4. The method of claim 1, further comprising transmitting energy levels for each frequency band.

5. The method of claim 4, wherein the energy levels are transmitted using a signal defined for a perceptual noise substitution encoding tool of an encoder.

6. The method of claim 1, further comprising providing signal-adaptive noise decisions in time and frequency dimensions.

7. The method of claim 1, further comprising determining if each frequency band is tonal or tonal-like using the defined boundaries.

8. A system for estimating and detecting noise and noise-like spectral signal segments, the system comprising:

a device having a processor and an interface that receives signals; and

an encoder that determines noise or noise-like characteristics in frequency bands of the received signals using boundaries defined from a ratio of mean and variance energies in each frequency band and a stage of two or more decisions.

9. The system of claim 8, wherein the encoder is an advanced audio coding (AAC) encoder.

10. The system of claim 8, wherein the defined boundaries may change over time.

11. The system of claim 8, wherein the encoder determines if each frequency band is tonal or tonal-like using the defined boundaries.

12. A device configured for estimating and detecting noise and noise-like spectral signal segments, the device comprising:

a memory configured to contain programmed instructions and communication signals; and

an encoder that determines noise or noise-like characteristics in frequency bands of the communication signals using boundaries defined from a ratio of mean and variance energies in each frequency band and a stage of two or more decisions.

13. The device of claim 12, wherein the encoder predicts gain for spectral segments for each frequency band.

14. The device of claim 13, wherein the encoder predicts gain using linear predictive coding.

15. The device of claim 12, further comprising an interface capable to transmit energy levels for each frequency band.

16. A computer program product embodied on a computer-readable medium that estimates and detects noise and noise-like spectral signal segments, the signal segments corresponding to one or more frequency bands of a signal, the computer program product comprising:

computer code to calculate mean and variance energies for each frequency band of a signal;

computer code to define boundaries for a ratio of the mean and variance energies in each frequency band of the signal; and

computer code to determine if each frequency band of the signal is noise or noise-like using the defined boundaries and a stage of two or more decisions.

17. The computer program product of claim 16, further comprising computer code to determine if each frequency band is tonal or tonal-like using the defined boundaries.

18. The computer program product of claim 16, further comprising computer code to predict gain for spectral samples corresponding to each frequency band of a signal.

19. The computer program product of claim 16, further comprising computer code to transmit energy levels for each frequency band.

20. The computer program product of claim 19, wherein the energy levels are transmitted using a signal defined for a perceptual noise substitution encoding tool of an encoder.