Elimination of clipping associated with VAD-directed silence suppression

• US 6,865,162 B1
• Filed: 12/06/2000
• Issued: 03/08/2005
• Est. Priority Date: 12/06/2000
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Clemm, Alexander
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US09/732,104
• Time in Patent Office: 1,553 Days
• Field of Search: 370/286, 370/253, 370/353, 370/371, 370/516, 370/406, 704/201, 379/52, 379/406.03
• US Class Current: 370/286
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm

Abstract

A method and apparatus for elimination of clipping associated with VAD-directed silence suppression includes receiving a voice signal in a buffer during the delay between the start of voice activity and the detection of the voice activity. Then, the voice signal is played from the buffer in condensed form, e.g., by dropping packets or slightly accelerating playback of the signal from the buffer. After voice activity is detected, the voice signal may continue to be buffered and condensed until the buffer is completely depleted. The voice signal may then be transmitted directly, without being buffered or condensed.

Claims

1. A method comprising:

receiving a voice signal in a buffer;

ending silence suppression; and

condensing the voice signal.

2. The method of claim 1, wherein condensing further comprises:

reading the voice signal from the buffer faster than a speed that the voice signal is received in the buffer.

3. The method of claim 1, wherein condensing further comprises:

compressing inter-sound space of the voice signal.

4. The method of claim 1, wherein condensing further comprises:

dropping packets from the voice signal.

5. The method of claim 1, further comprising:

transmitting the condensed voice signal.

6. An apparatus comprising:

means for receiving a voice signal in a buffer;

means for ending silence suppression; and

means for condensing the voice signal.

7. The apparatus of claim 6, wherein said means for condensing further comprises:

means for reading the voice signal from the buffer faster than a speed that the voice signal is received in the buffer.

8. The apparatus of claim 6, wherein said means for condensing further comprises:

means for compressing inter-sound space of the voice signal.

9. The apparatus of claim 6, wherein said means for condensing further comprises:

means for dropping packets from the voice signal.

10. The apparatus of claim 6, further comprising:

means for transmitting the condensed voice signal.

11. A computer readable medium having instructions, which, when executed by a processing system, cause the system to:

receive a voice signal in a buffer;

end silence suppression; and

condense the voice signal.

12. The medium of claim 11, wherein the executed instructions cause the system to condense by:

reading the voice signal from the buffer faster than a speed that the voice signal is received in the buffer.

13. The medium of claim 11, wherein the executed instructions cause the system to condense by:

compressing inter-sound space of the voice signal.

14. The medium of claim 11, wherein the executed instructions cause the system to condense by:

dropping packets from the voice signal.

15. The medium of claim 11, further comprising instructions, which, when executed, cause the system to:

transmit the condensed voice signal.

16. An apparatus comprising:

a buffer to receive and store a voice signal;

a voice activity detector to detect voice activity and to output a voice activity detection signal; and

a condensing device to read the voice signal from the buffer and to output a condensed voice signal in response to the voice activity detection signal.

17. The apparatus of claim 16, wherein the condensing device condenses the voice signal by reading the voice signal from the buffer faster than a speed that the voice signal is received by the buffer.

18. The apparatus of claim 16, wherein the condensing device condenses the voice signal by compressing inter-sound space of the voice signal.

19. The apparatus of claim 16, wherein the condensing device condenses the voice signal by dropping at least one packet from the voice signal.

20. The apparatus of claim 16, further comprising:

a transmission device to transmit the condensed voice signal.

21. A method comprising:

suppressing silence in a voice signal for a time period, the voice signal having a first temporal length;

detecting voice activity in the voice signal during the time period of silence suppression;

buffering the voice signal during a buffer delay period approximately between a first time when the voice activity is detected and a second time when the silence suppression ends; and

condensing the voice signal to have a second temporal length less than the first temporal length.

22. The method of claim 21, further comprising communicating the condensed voice signal to a transmission device in response to detecting the voice activity.

23. The method of claim 22, further comprising ending the time period of silence suppression after the condensed voice signal is communicated to the transmission device.

24. The method of claim 22, further comprising transmitting the condensed voice signal.

25. The method of claim 21, further comprising buffering the voice signal continuously during the time period of silence suppression.

26. The method of claim 21, wherein buffering the voice signal occurs at a buffering speed and wherein condensing the voice signal comprises depleting the voice signal from a buffer over a buffer depletion period at a playback speed that is faster on average than the buffering speed.

27. The method of claim 26, wherein the playback speed is variable over the buffer depletion period.

28. The method of claim 27, wherein the playback speed is determined according to a decreasing speed function, wherein the playback speed is faster at the beginning of the buffer depletion period and approximately the same as the buffering speed at the end of the buffer depletion period.

29. The method of claim 21, wherein condensing the voice signal comprises compressing an inter-sound space of the voice signal.

30. The method of claim 21, wherein condensing the voice signal comprises dropping a packet from the voice signal.

31. A computer readable medium having instructions, which, when executed by a processing system, cause the system to:

suppress silence in a voice signal for a time period, the voice signal having a first temporal length;

detect voice activity in the voice signal during the time period of silence suppression;

buffer the voice signal during a buffer delay period approximately between a first time when the voice activity is detected and a second time when the silence suppression ends; and

condense the voice signal to have a temporal length less than the first temporal length.

32. The computer readable medium of claim 31, further comprising instructions to cause the system to communicate the condensed voice signal to a transmission device in response to detecting the voice activity.

33. The computer readable medium of claim 32, further comprising instructions to cause the system to end the time period of silence suppression after the condensed voice signal is communicated to the transmission device.

34. The computer readable medium of claim 32, further comprising instructions to cause the system to transmit the condensed voice signal.

35. The computer readable medium of claim 31, further comprising instructions to cause the system to buffer the voice signal continuously during the time period of silence suppression.

36. The computer readable medium of claim 31, wherein the instructions to cause the system to buffer the voice signal further cause the system to buffer the voice signal at a buffering speed and wherein the instructions to cause the system to condense the voice signal further cause the system to deplete the voice signal from a buffer over a buffer depletion period at a playback speed that is faster on average than the buffering speed.

37. The computer readable medium of claim 36, wherein the playback speed is variable over the buffer depletion period.

38. The computer readable medium of claim 37, wherein palyback speed is determined according to a decreasing speed function, wherein the playback speed is faster at the beginning of the buffer depletion period and approximately the same as the buffering speed at the end of the buffer depletion period.

39. The computer readable medium of claim 31, wherein the instructions to cause the system to condense the voice signal further cause the system to compress an inter-sound space of the voice signal.

40. The computer readable medium of claim 31, wherein the instructions to cause the system to condense the voice signal further cause the system to discard a packet from the voice signal.