Audio mute concealment

• US 8,538,038 B1
• Filed: 02/12/2010
• Issued: 09/17/2013
• Est. Priority Date: 02/12/2010
• Status: Active Grant

• Current Assignee: Shure Acquisition Holdings Inc. (Shure Incorporated)
• Original Assignee: Shure Acquisition Holdings Inc. (Shure Incorporated)
• Inventors: Lester, Michael Ryan
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): Zhao, Eugene
• Application Number:
  US12/705,034
• Time in Patent Office: 1,313 Days
• Field of Search: 381/73.1, 381/77, 381/182, 455/436, 375/259
• US Class Current: 381/94.5
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08

Abstract

Mute intervals of an audio signal are concealed by decreasing a user'"'"'s perception of missing audio information. During the mute interval, different concealment techniques are activated at different times to form a concealment signal. The concealment signal is applied to the processed audio signal during the mute interval. A concealment technique may process buffered audio samples before the mute interval in order to obtain the concealment signal. Also, a previously activated concealment generator may be phased out while the currently activated concealment generator may be phased in during a transition period of a mute interval. Different concealment techniques may be used to generate a concealment signal, including a periodic extension concealment technique, a reverberation concealment technique, and a spectral replication technique. Further, the power levels may be matched between different periods of a mute interval.

Claims

1. A method comprising:

(a) when a mute interval of an audio signal is detected, activating one of a plurality of concealment generators to form a concealment signal and activating a timer, each concealment generator utilizing a different concealment technique;

(b) while the mute interval continues and when the timer equals a predetermined activation time, activating a different concealment generator of the plurality of concealment generators and deactivating a previously activated concealment generator to extend the concealment signal;

(c) repeating (b) while the mute interval continues;

(d) adding the concealment signal when there is a gap in the audio signal during the mute interval, wherein;

the concealment signal replaces the audio signal during at least a portion of the mute interval; and

the concealment signal is independent of knowledge about the audio signal after the mute interval; and

(e) when the mute interval ends, deactivating a currently activated concealment generator.

2. The method of claim 1, wherein the activating the different concealment generator comprises:

phasing in the different concealment generator during a predetermined transition interval; and

phasing out the previously activated concealment generator during the predetermined transition interval.

3. The method of claim 1, wherein the plurality of concealment generators support a periodic extension technique and a reverberation concealment technique.

4. The method of claim 1 further comprising:

deactivating the different concealment generator and activating another concealment generator at a subsequent predetermined activation time.

5. The method of claim 4, wherein the other concealment generator utilizes a spectral replication concealment technique.

6. The method of claim 3, further comprising:

the periodic extension technique utilizing a time domain reversal of buffered samples of the audio signal after a zero crossing with a flip in waveform polarity to prevent a waveform discontinuity.

7. The method of claim 6, further comprising:

extending audio content prior to the mute interval using a self-prediction technique on which to perform zero crossing detection.

8. The method of claim 5, wherein the spectral replication technique detects the mute interval of the audio signal, obtains buffered samples of the audio signal before the mute interval occurs, performs a spectral analysis of the buffered samples to obtain spectral samples, determines a magnitude of each spectral sample, combines the magnitude and a random phase value for each said spectral sample to obtain modified spectral samples, performs an inverse spectral analysis of the modified spectral samples to obtain time domain samples, removes an imaginary component of each time domain sample to obtain modified time domain samples, and adds the modified time domain samples to the audio signal during the mute interval.

9. The method of claim 1, further comprising:

matching a concealment signal power level with an audio power level of the audio signal before the mute interval when one of the plurality of concealment generators is activated.

10. The method of claim 1, further comprising:

matching a previous concealment power level of the previously activated concealment generator with a current concealment power level of the currently activated concealment generator.

11. The method of claim 2, wherein the phasing in utilizes a linearly increasing function and the phasing out utilizes a linearly decreasing function.

12. The method of claim 2, wherein the phasing in utilizes a logarithmically increasing function and the phasing out utilizes a logarithmically decreasing function.

13. The method of claim 1, wherein the deactivating the currently activated concealment generator utilizes a linearly decreasing function, and the method further comprises:

when the mute interval ends, phasing in the audio signal with a linearly increasing function.

14. The method of claim 1, wherein the deactivating the currently activated concealment generator utilizes a logarithmically decreasing function, and the method further comprises:

when the mute interval ends, phasing in the audio signal with a logarithmically increasing function.

15. The method of claim 1, wherein different concealment generators are chosen for execution based on an audio feature analysis of the audio signal prior to the mute interval.

16. The method of claim 1, wherein parameters for different concealment generators are chosen or altered based on an audio feature analysis of the audio signal prior to the mute interval.

17. The method of claim 2, wherein characteristics of the phasing in and the phasing out are determined by an audio feature analysis of the audio signal prior to the mute interval.

18. The method of claim 1, wherein (a)-(e) are performed without information about audio content that occurs after the mute interval.

33. The method of claim 1, further comprising:

matching the concealment signal with at least one characteristic of the audio signal that characterizes the audio signal before the mute interval.

34. The method of claim 1 wherein the plurality of concealment generators comprises a self-prediction technique and a periodic extension technique.

35. The method of claim 6, further comprising:

using a buffered window taper to force the zero crossing after a time interval on which to perform a periodic extension.

36. The method of claim 1 wherein the plurality of concealment generators comprises a periodic extension technique and a spectral replication technique.

19. An apparatus comprising:

at least one processing device;

a memory having stored therein machine executable instructions or firmware for logical processing, that when executed, cause the apparatus to;

(a) when a mute interval of an audio signal occurs, activate one of a plurality of concealment generators to form a concealment signal, activate a timer, and

match the power level of the audio signal before the mute interval when said one of the plurality of concealment generators is activated, wherein each concealment generator utilizes a different concealment technique;

(b) while the mute interval continues and when the timer equals a predetermined activation time, activate a different concealment generator of the plurality of concealment generators, deactivate a previously activated concealment generator to extend the concealment signal, and match power levels associated with the different concealment generator and the previously activated concealment generator;

(c) repeat (b) while the mute interval continues;

(d) add the concealment signal when there is a gap in the audio signal during the mute interval, wherein;

the concealment signal replaces the audio signal during at least a portion of the mute interval; and

the concealment signal is independent of knowledge about the audio signal after the mute interval; and

(e) when the mute interval ends, deactivate a currently activated concealment generator.

20. The apparatus of claim 19, wherein the apparatus does not utilize information about audio content that occurs after the mute interval.

21. The apparatus of claim 19, wherein the memory further causes the apparatus to:

phase in the different concealment generators during a predetermined transition interval; and

phase out the previously activated concealment generators during the predetermined transition interval.

22. The apparatus of claim 19, wherein the memory further causes the apparatus to:

phase in the different concealment generator based on information obtained from an audio feature analysis prior to the mute interval; and

phase out the previously activated concealment generator based on the information obtained from the audio feature analysis prior to the mute interval.

23. A non-transitory computer-readable storage medium storing computer-executable instructions that, when executed, cause a processor to perform:

(a) when a mute interval of an audio signal is detected, activating one of a plurality of concealment generators to form a concealment signal and activating a timer, each concealment generator utilizing a different concealment technique;

(b) while the mute interval continues and when the timer equals a predetermined activation time, activating a different concealment generator of the plurality of concealment generators and deactivating a previously activated concealment generator to extend the concealment signal;

(c) repeating (b) while the mute interval continues;

(d) adding the concealment signal when there is a gap in the audio signal during the mute interval, wherein;

the concealment signal replaces the audio signal during at least a portion of the mute interval; and

the concealment signal is independent of knowledge about the audio signal after the mute interval; and

(e) when the mute interval ends, deactivating a currently activated concealment generator.

24. The computer-readable storage medium of claim 23, wherein (a)-(e) are performed without information about audio content that occurs after the mute interval.

25. The computer-readable storage medium of claim 23, said method further comprising:

phasing in the different concealment generator during a predetermined transition interval; and

phasing out the previously activated concealment generator during the predetermined transition interval.

26. The computer-readable storage medium of claim 24, said method further comprising:

matching a concealment power level with an audio power level of the audio signal before the mute interval when said one of the plurality of concealment generators is activated.

27. The computer-readable storage medium of claim 23, said method further comprising:

matching a previous concealment power level of the previously activated concealment generator with a current concealment power level of the currently activated concealment generator.

28. A non-transitory computer-readable storage medium storing instructions or logical processing that, when excited with input data stimulus, cause an apparatus to perform:

(a) when a mute interval of an audio signal is detected, activating one of a plurality of concealment generators to form a concealment signal and activating a timer, each concealment generator utilizing a different concealment technique;

(b) while the mute interval continues and when the timer equals a predetermined activation time, activating a different concealment generator of the plurality of concealment generators and deactivating a previously activated concealment generator to extend the concealment signal;

(c) repeating (b) while the mute interval continues;

(d) adding the concealment signal when there is a gap in the audio signal during the mute interval, wherein;

the concealment signal replaces the audio signal during at least a portion of the mute interval; and

the concealment signal is independent of knowledge about the audio signal after the mute interval; and

(e) when the mute interval ends, deactivating a currently activated concealment generator.

29. A wireless microphone system comprising:

a receiver providing an indication of a mute interval of an audio signal to a concealment processing component; and

the concealment processing component including;

a plurality of concealment generators;

a timer;

at least one processor;

at least one memory having stored therein machine executable instructions, that when executed, cause the concealment processing component to;

(a) activate one of the plurality of concealment generators to form a concealment signal and activating the timer, each concealment generator utilizing a different concealment technique;

(b) while the mute interval continues and when the timer equals a predetermined activation time, activating a different concealment generator of the plurality of concealment generators and deactivating a previously activated concealment generator to extend the concealment signal;

(c) repeating (b) while the mute interval continues;

(d) adding the concealment signal when there is a gap in the audio signal during the mute interval, wherein;

the concealment signal replaces the audio signal during at least a portion of the mute interval; and

the concealment signal is independent of knowledge about the audio signal after the mute interval; and

(e) when the mute interval ends, deactivating a currently activated concealment generator.

30. The wireless microphone system of claim 29 wherein said one concealment generator utilizes a periodic extension concealment technique and the different concealment generator utilizes a reverberation concealment technique.

31. The wireless microphone system of claim 29 wherein said one concealment generator utilizes a periodic extension concealment technique and the different concealment generator utilizes a spectral replication technique.

32. The wireless microphone system of claim 29 in which the concealment processing component performs (a)-(e) without information about audio content that occurs after the mute interval.