Noise detection for audio encoding by mean and variance energy ratio

• US 8,060,362 B2
• Filed: 10/20/2008
• Issued: 11/15/2011
• Est. Priority Date: 08/23/2004
• Status: Active Grant

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Ojanpera, Juha Petteri
• Primary Examiner(s): Albertalli; Brian
• Application Number:
  US12/254,448
• Publication Number:
  US 20090043590A1
• Time in Patent Office: 1,121 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, comprising:

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

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

determining, in a processor, 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. An apparatus, comprising:

an encoder configured to determine noise or noise-like characteristics in frequency bands of 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 apparatus of claim 8 further comprising a processor configured to receive signals.

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

11. The apparatus of claim 8, wherein the defined boundaries may change over time.

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

13. An apparatus, comprising:

an encoder configured to determine noise or noise-like characteristics in frequency bands of 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.

14. The apparatus of claim 13 further comprising a memory configured to contain programmed instructions and communication signals.

15. The apparatus of claim 13 wherein the encoder is further configured to predict gain for spectral segments for each frequency band.

16. The apparatus of claim 13 wherein the encoder is further configured to predict gain using linear predictive coding.

17. The apparatus of claim 13 further comprising an interface configured to transmit energy levels for each frequency band.

18. A computer program product embodied on a computer readable medium that estimates and detects noise and noise-like spectral signal segments, the computer program product comprising:

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

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

code for 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.

19. The computer program product of claim 18, further comprising code for determining if each frequency band is tonal or tonal-like using the defined boundaries.

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

21. The computer program product of claim 18, further comprising code for transmitting energy levels for each frequency band.

22. The computer program product of claim 21, wherein the energy levels are transmitted using a signal defined for a perceptual noise substitution encoding tool of an encoder.